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Constraining the Mass-Richness Relationship of redMaPPer Clusters with
Angular Clustering: The potential of using cluster clustering for calibrating the mass-observable
relation of galaxy clusters has been recognized theoretically for over a
decade. Here, we demonstrate the feasibility of this technique to achieve high
precision mass calibration using redMaPPer clusters in the Sloan Digital Sky
Survey North Galactic Cap. By including cross-correlations between several
richness bins in our analysis we significantly improve the statistical
precision of our mass constraints. The amplitude of the mass-richness relation
is constrained to 7% statistical precision. However, the error budget is
systematics dominated, reaching an 18% total error that is dominated by
theoretical uncertainty in the bias-mass relation for dark matter halos. We
perform a detailed treatment of the effects of assembly bias on our analysis,
finding that the contribution of such effects to our parameter uncertainties is
somewhat greater than that of measurement noise. We confirm the results from
Miyatake et al. (2015) that the clustering amplitude of redMaPPer clusters
depends on galaxy concentration, and provide additional evidence in support of
this effect being due to some form of assembly bias. The results presented here
demonstrate the power of cluster clustering for mass calibration and cosmology
provided the current theoretical systematics can be ameliorated. | The JCMT Nearby Galaxies Legacy Survey VIII. CO data and the
L(CO3-2)-L(FIR) correlation in the SINGS sample: The James Clerk Maxwell Telescope Nearby Galaxies Legacy Survey (NGLS)
comprises an HI-selected sample of 155 galaxies spanning all morphological
types with distances less than 25 Mpc. We describe the scientific goals of the
survey, the sample selection, and the observing strategy. We also present an
atlas and analysis of the CO J=3-2 maps for the 47 galaxies in the NGLS which
are also part of the Spitzer Infrared Nearby Galaxies Survey. We find a wide
range of molecular gas mass fractions in the galaxies in this sample and
explore the correlation of the far-infrared luminosity, which traces star
formation, with the CO luminosity, which traces the molecular gas mass. By
comparing the NGLS data with merging galaxies at low and high redshift which
have also been observed in the CO J=3-2 line, we show that the correlation of
far-infrared and CO luminosity shows a significant trend with luminosity. This
trend is consistent with a molecular gas depletion time which is more than an
order of magnitude faster in the merger galaxies than in nearby normal
galaxies. We also find a strong correlation of the L(FIR)/L(CO3-2) ratio with
the atomic to molecular gas mass ratio. This correlation suggests that some of
the far-infrared emission originates from dust associated with atomic gas and
that its contribution is particularly important in galaxies where most of the
gas is in the atomic phase. |
Wide-field VLBA Observations of the Chandra Deep Field South: Wide-field surveys are a commonly-used method for studying thousands of
objects simultaneously, to investigate, e.g., the joint evolution of
star-forming galaxies and active galactic nuclei. VLBI observations can yield
valuable input to such studies because they are able to identify AGN. However,
VLBI observations of large swaths of the sky are impractical using standard
methods, because the fields of view of VLBI observations are of the order of
10" or less. We have embarked on a project to carry out Very Long Baseline
Array (VLBA) observations of all 96 known radio sources in one of the
best-studied areas in the sky, the Chandra Deep Field South (CDFS). The
challenge was to develop methods which could significantly reduce the amount of
observing (and post-processing) time. We have developed an extension to the
DiFX software correlator which allows one to correlate hundreds of positions
within the primary beams. This extension enabled us to target many sources, at
full resolution and high sensitivity, using only a small amount of observing
time. The combination of wide fields-of-view and high sensitivity across the
field in this survey is unprecedented. We have observed with the VLBA a single
pointing containing the Chandra Deep Field South, in which 96 radio sources
were known from previous observations with the ATCA. From our input sample, 20
were detected with the VLBA. The majority of objects have flux densities in
agreement with arcsec-scale observations, implying that their radio emission
comes from very small regions. One VLBI-detected object had earlier been
classified as a star-forming galaxy. Comparing the VLBI detections to sources
found in sensitive, co-located X-ray observations we find that X-ray detections
are not a good indicator for VLBI detections. Wide-field VLBI survey science is
now coming of age. | A Redshift Survey of the Strong Lensing Cluster Abell 383: Abell 383 is a famous rich cluster (z = 0.1887) imaged extensively as a basis
for intensive strong and weak lensing studies. Nonetheless there are few
spectroscopic observations. We enable dynamical analyses by measuring 2360 new
redshifts for galaxies with r$_{petro} \leq 20.5$ and within 50$^\prime$ of the
BCG (Brightest Cluster Galaxy: R.A.$_{2000} = 42.014125^\circ$, Decl$_{2000} =
-03.529228^\circ$). We apply the caustic technique to identify 275 cluster
members within 7$h^{-1}$ Mpc of the hierarchical cluster center. The BCG lies
within $-11 \pm 110$ km s$^{-1}$ and 21 $\pm 56 h^{-1}$ kpc of the hierarchical
cluster center; the velocity dispersion profile of the BCG appears to be an
extension of the velocity dispersion profile based on cluster members. The
distribution of cluster members on the sky corresponds impressively with the
weak lensing contours of Okabe et al. (2010) especially when the impact of
foreground and background structure is included. The values of R$_{200}$ =
$1.22\pm 0.01 h^{-1}$ Mpc and M$_{200}$ = $(5.07 \pm 0.09)\times 10^{14}
h^{-1}$ M$_\odot$ obtained by application of the caustic technique agree well
with recent completely independent lensing measures. The caustic estimate
extends direct measurement of the cluster mass profile to a radius of $\sim 5
h^{-1}$ Mpc. |
The RASS--6dFGS catalogue: a sample of X-ray selected AGN from the 6dF
Galaxy Survey: We present a catalogue of 3405 X-ray sources from the ROSAT All Sky Survey
(RASS) Bright Source Catalogue which fall within the area covered by the 6dF
Galaxy Survey (6dFGS). The catalogue is count-rate limited at 0.05 cts\s in the
X-ray and covers the area of sky with delta < 0 deg and |b|>10 deg. The
RASS--6dFGS sample was one of the additional target catalogues of the 6dFGS and
as a result we obtained optical spectra for 2224 (65%) RASS sources. Of these,
1715 (77%) have reliable redshifts with a median redshift of z=0.16 (excluding
the Galactic sources). For the optically bright sources (b_J < 17.5) in the
observed sample, over 90% have reliable redshifts. The catalogue mainly
comprises QSOs and active galaxies but also includes 238 Galactic sources. Of
the sources with reliable redshifts the majority are Type 1 AGN (69%), while
12% are Type 2 AGN, 6% absorption-line galaxies and 13% are stars. We also
identify a small number of optically-faint, very low redshift, compact objects
which fall outside the general trend in the b_J-z plane.
We detect 918 sources (27%) of the RASS--6dFGS sample in the radio using
either the 1.4 GHz NRAO VLA Sky Survey (NVSS) or the 843 MHz Sydney University
Molonglo Sky Survey (SUMSS) catalogues and find that the detection rate changes
with redshift. At redshifts larger than 1 virtually all of these sources have
radio counterparts and with a median flux density of 1.15 Jy, they are much
stronger than the median flux density of 28.6 mJy for the full sample. We
attribute this to the fact that the X-ray flux of these objects is being
boosted by a jet component, possibly Doppler boosted, that is only present in
radio-loud AGN. (abridged version) | Radio Sources from a 31 GHz Sky Survey with the Sunyaev-Zel'dovich Array: We present the first sample of 31-GHz selected sources to flux levels of 1
mJy. From late 2005 to mid 2007, the Sunyaev-Zel'dovich Array (SZA) observed
7.7 square degrees of the sky at 31 GHz to a median rms of 0.18 mJy/beam. We
identify 209 sources at greater than 5 sigma significance in the 31 GHz maps,
ranging in flux from 0.7 mJy to ~200 mJy. Archival NVSS data at 1.4 GHz and
observations at 5 GHz with the Very Large Array are used to characterize the
sources. We determine the maximum-likelihood integrated source count to be
N(>S) = (27.2 +- 2.5) deg^-2 x (S_mJy)^(-1.18 +- 0.12) over the flux range 0.7
- 15 mJy. This result is significantly higher than predictions based on 1.4-GHz
selected samples, a discrepancy which can be explained by a small shift in the
spectral index distribution for faint 1.4-GHz sources. From comparison with
previous measurements of sources within the central arcminute of massive
clusters, we derive an overdensity of 6.8 +- 4.4, relative to field sources. |
Multitension strings in high-resolution U(1)$\times$U(1) simulations: Topological defects are a fossil relic of early Universe phase transitions,
with cosmic strings being the best motivated example. While in most cases one
studies Nambu-Goto or Abelian-Higgs strings, one also expects that
cosmologically realistic strings should have additional degrees of freedom in
their worldsheets, one specific example being superstrings from Type IIB
superstring theory. Here we continue the scientific exploitation of our
recently developed multi-GPU field theory cosmic strings code to study the
evolution of U(1)$\times$U(1) multitension networks, which are a numerically
convenient proxy: these contain two lowest-tension strings networks able to
interact and form bound states, providing a convenient first approximation to
the behaviour expected from cosmic superstrings. (...) We rely on the largest
field theory simulations of this model so far, specifically $4096^3$, $\Delta x
= 0.5$ boxes. We present robust evidence of scaling for the lightest strings,
measured through a complete and self-consistent set of correlation length and
velocity diagnostics. We also find a linearly growing average length of the
bound state segments, consistent with a scaling behaviour. (In previously
reported lower-resolution simulations, such behaviour had only been identified
with carefully engineered initial conditions, rich in those segments.) Finally,
while we see no evidence of a large population of bound states forming at early
stages of the network evolution, we do present tentative evidence for an
asymptotic constant value of the fraction of bound states, with this value
being different in the radiation and the matter eras. Our work demonstrates
that our GPU-accelerated field theory code can by successfully extended beyond
the simple Abelian-Higgs approximation, and enables future detailed studies of
realistic string networks and of their observational signatures. | Resonant Conversion of Dark Matter Oscillons in Pulsar Magnetospheres: Due to their high magnetic fields and plasma densities, pulsars provide
excellent laboratories for tests of beyond Standard Model (BSM) physics. When
axions or axion-like particles (ALPs) approach closely enough to pulsars, they
can be resonantly converted to photons, yielding dramatic electromagnetic
signals. We discuss the possibility of detecting such signals from bound
configurations of axions, colliding with pulsar magnetospheres. We find that
all but the densest axion stars, $\textit{oscillons}$, are tidally destroyed
well before resonant conversion can take place. Oscillons can be efficiently
converted to photons, leading to bright, ephemeral radio flashes. Observation
of the galactic bulge using existing (Very Large Array and LOFAR) and
forthcoming (Square Kilometer Array) radio missions has the potential to detect
such events for axion masses in the range $m_a \in \left[0.1 \ \mu\text{eV},
200 \ \mu\text{eV}\right]$, even if oscillons make up a negligible fraction of
dark matter. |
Stellar binary black holes in the LISA band: a new class of standard
sirens: The recent Advanced LIGO detections of coalescing black hole binaries (BHBs)
imply a large population of such systems emitting at milli-Hz frequencies,
accessible to the Laser Interferometer Space Antenna (LISA). We show that these
systems provide a new class of cosmological standard sirens. Direct LISA
luminosity distance -$D_l$- measurements, combined with the inhomogeneous
redshift -$z$- distribution of possible host galaxies provide an effective way
to populate the $D_l-z$ diagram at $z<0.1$, thus allowing a precise local
measurement of the Hubble expansion rate. To be effective, the method requires
a sufficiently precise LISA distance determination and sky localization of a
sizeable number of BHBs, which is best achieved for a 6-link detector
configuration. We find that, for a BHB population consistent with current
fiducial LIGO rates, the Hubble constant $H_0$ can be determined at the
$\sim$5% and $\sim$2% level (68% confidence) assuming two and five million Km
arm-length respectively. | New 20-CM Radio-Continuum Study of The Small Magellanic Cloud: Part II -
Point Sources Catalogue: We present a new catalogue of radio-continuum sources in the field of the
Small Magellanic Cloud (SMC). This catalogue contains sources previously not
found in 2370 MHz ({\lambda}=13 cm) with sources found at 1400 MHz
({\lambda}=20 cm) and 843 MHz ({\lambda}=36 cm). 45 sources have been detected
at 13 cm, with 1560 sources at 20 cm created from new high sensitivity and
resolution radio-continuum images of the SMC at 20 cm from Paper I . We also
created a 36 cm catalogue to which we listed 1689 radio-continuum sources. |
Counting voids to probe dark energy: We show that the number of observed voids in galaxy redshift surveys is a
sensitive function of the equation of state of dark energy. Using the Fisher
matrix formalism we find the error ellipses in the $w_0-w_a$ plane when the
equation of state of dark energy is assumed to be of the form $w_{CPL}(z)=w_0
+w_a z/(1+z)$. We forecast the number of voids to be observed with the ESA
Euclid satellite and the NASA WFIRST mission, taking into account updated
details of the surveys to reach accurate estimates of their power. The
theoretical model for the forecast of the number of voids is based on matches
between abundances in simulations and the analytical prediction. To take into
account the uncertainties within the model, we marginalize over its free
parameters when calculating the Fisher matrices. The addition of the void
abundance constraints to the data from Planck, HST and supernova survey data
noticeably tighten the $w_0-w_a$ parameter space. We thus quantify the
improvement in the constraints due to the use of voids and demonstrate that the
void abundance is a sensitive new probe for the dark energy equation of state. | A Relativistic view on large scale N-body simulations: We discuss the relation between the output of Newtonian N-body simulations on
scales that approach or exceed the particle horizon to the description of
General Relativity. At leading order, the Zeldovich approximation is correct on
large scales, coinciding with the General Relativistic result. At second order
in the initial metric potential, the trajectories of particles deviate from the
second order Newtonian result and hence the validity of 2LPT initial conditions
should be reassessed when used in very large simulations. We also advocate
using the expression for the synchronous gauge density as a well behaved
measure of density fluctuations on such scales. |
Measuring the maximally allowed polarization states of the isotropic
stochastic gravitational wave background with the ground-based detectors: We discuss the polarizational study of isotropic gravitational wave
backgrounds with the second generation detector network, paying special
attention to the impacts of adding LIGO-India. The backgrounds can be
characterized by at most five spectral components (three parity-even ones and
two parity-odd ones). They can be algebraically decomposed through the
difference of the corresponding overlap reduction functions defined for the
individual spectra. We newly identify two interesting relations between the
overlap reduction functions, and these relations generally hamper the algebraic
decomposition in the low frequency regime $f \lesssim 30$Hz. We also find that
LIGO-India can significantly improve the network sensitives to the odd spectral
components. | Dark-ages Reionization & Galaxy Formation Simulation VIII. Suppressed
growth of dark matter halos during the Epoch of Reionization: We investigate how the hydrostatic suppression of baryonic accretion affects
the growth rate of dark matter halos during the Epoch of Reionization. By
comparing halo properties in a simplistic hydrodynamic simulation in which gas
only cools adiabatically, with its collisionless equivalent, we find that halo
growth is slowed as hydrostatic forces prevent gas from collapsing. In our
simulations, at the high redshifts relevant for reionization (between ${\sim}6$
and ${\sim}11$), halos that host dwarf galaxies ($\lesssim 10^{9}
\mathrm{M_\odot}$) can be reduced by up to a factor of 2 in mass due to the
hydrostatic pressure of baryons. Consequently, the inclusion of baryonic
effects reduces the amplitude of the low mass tail of the halo mass function by
factors of 2 to 4. In addition, we find that the fraction of baryons in dark
matter halos hosting dwarf galaxies at high redshift never exceeds ${\sim}90\%$
of the cosmic baryon fraction. When implementing baryonic processes, including
cooling, star formation, supernova feedback and reionization, the suppression
effects become more significant with further reductions of ${\sim}30\%$ to
60\%. Although convergence tests suggest that the suppression may become weaker
in higher resolution simulations, this suppressed growth will be important for
semi-analytic models of galaxy formation, in which the halo mass inherited from
an underlying N-body simulation directly determines galaxy properties. Based on
the adiabatic simulation, we provide tables to account for these effects in
N-body simulations, and present a modification of the halo mass function along
with explanatory analytic calculations. |
Galaxy And Mass Assembly (GAMA): A deeper view of the mass, metallicity,
and SFR relationships: A full appreciation of the role played by gas metallicity (Z), star-formation
rate (SFR), and stellar mass is fundamental to understanding how galaxies form
and evolve. The connections between these three parameters at different
redshifts significantly affect galaxy evolution, and thus provide important
constraints for galaxy evolution models. Using data from the Sloan Digital Sky
Survey-Data Release 7 (SDSS-DR7) and the Galaxy and Mass Assembly (GAMA)
surveys we study the relationships and dependencies between SFR, Z, and stellar
mass, as well as the Fundamental Plane for star-forming galaxies. We combine
both surveys using volume-limited samples up to a redshift of z ~ 0.36. The
GAMA and SDSS surveys complement each other when analyzing the relationships
between SFR, Mass and Z. We present evidence for SFR and metallicity evolution
to z ~ 0.2. We study the dependencies between SFR, Mass, Z, and specific
star-formation rate (SSFR) on the M-Z, M-SFR, M-SSFR, Z-SFR, and Z-SSFR
relations, finding strong correlations between all. Based on those
dependencies, we propose a simple model that allows us to explain the different
behaviour observed between low and high mass galaxies. Finally, our analysis
allows us to confirm the existence of a Fundamental Plane, for which Mass=f(Z,
SFR) in star-forming galaxies. | Resonant magnetogenesis from axions: We investigate the generation of seed magnetic field through the Chern-Simons
coupling between the U(1) gauge field and an axion field that commences to
oscillate at various epoch, depending on the mass scale. We address axions
which begin oscillation during inflation, reheating, and also the radiation
dominated era after the thermalization of the Universe. We study the resonant
generation mechanisms and highlight that a small oscillation time scale with
respect to that of the cosmic expansion can lead to an efficient generation of
(hyper) magnetic field via resonant generation, even for ${\cal O}(1)$
coupling. In addition, we demonstrate that the generated field can be helical
due to the tachyonic amplification phase prior to the onset of oscillation.
Furthermore, it is shown that the parametric resonance during reheating can
generate a circularly polarized (hyper) magnetic field in a void region with
the present amplitude $B_0 =3\times 10^{-15}$Gauss and the coherent length
$\lambda_0 = 0.3$pc without being plagued by the backreaction issue. |
Oscillations and Random Walk of the Soliton Core in a Fuzzy Dark Matter
Halo: A Fuzzy Dark Matter (FDM) halo consists of a soliton core close to the center
and an NFW-like density profile in the outer region. Previous investigations
found that the soliton core exhibits temporal oscillations and random walk
excursions around the halo center. Analyzing a set of numerical simulations, we
show that both phenomena can be understood as the results of wave interference
-- a suitable superposition of the ground (solitonic) state and excited states
in a fixed potential suffices to account for the main features of these
phenomena. Such an eigenmode analysis can shed light on the evolution of a
satellite halo undergoing tidal disruption. As the outer halo is stripped away,
reducing the amplitudes of the excited states, the ground state evolves
adiabatically. This suggests diminished soliton oscillations and random walk
excursions, an effect to consider in deducing constraints from stellar heating. | Supergravity based inflation models: a review: In this review, we discuss inflation models based on supergravity. After
explaining the difficulties in realizing inflation in the context of
supergravity, we show how to evade such difficulties. Depending on types of
inflation, we give concrete examples, particularly paying attention to chaotic
inflation because the ongoing experiments like Planck might detect the tensor
perturbations in near future. We also discuss inflation models in Jordan frame
supergravity, motivated by Higgs inflation. |
Red-channel (6000-8000 Å) nuclear spectra of 376 local galaxies: We obtained long-slit optical spectra of the nuclear regions of 376 galaxies
in the local Universe using the 1.5m Cassini telescope of Bologna Observatory.
Of these spectra, 164 were either never taken before by the Sloan Digital Sky
Survey (SDSS), or given by the Nasa Extragalactic Database (NED). With these
new spectra, we contribute investigating the occurrence of active galactic
nuclei (AGNs). Nevertheless, we stress that the present sample is by no means
complete, thus, it cannot be used to perform any demographic study. Following
the method presented in Gavazzi et al. (2011), we classify the nuclear spectra
using a six bin scheme: SEY (Seyfert), sAGN (strong AGN), and wAGN (weak AGN)
represent active galactic nuclei of different levels of activity; HII accounts
for star-forming nuclei; RET (retired) and PAS (passive) refer to nuclei with
poor or no star-formation activity. The spectral classification is performed
using the ratio of 6584 {\lambda} [NII] to H{\alpha} lines and the equivalent
width (EW) of H{\alpha} versus [NII]/H{\alpha} (WHAN diagnostic introduced by
Cid Fernandes and collaborators) after correcting H{\alpha} for underlying
absorption. The obtained spectra are made available in machine readable format
via the Strasbourg Astronomical Data Center (CDS) and NED. | Galaxy protocluster candidates at 1.6<z<2: We present a study of protoclusters associated with high redshift radio
galaxies. We imaged MRC1017-220 (z=1.77) and MRC0156-252 (z=2.02) using the
near-infrared wide-field (7.5'x7.5') imager VLT/HAWK-I in the Y, H and Ks
bands. We present the first deep Y-band galaxy number counts within a large
area (200 arcmin2). We then develop a purely near-infrared colour selection
technique to isolate galaxies at 1.6<z<3 that may be associated with the two
targets, dividing them into (i) red passively evolving or dusty star-forming
galaxies or (ii) blue/star-formation dominated galaxies with little or no dust.
Both targeted fields show an excess of star-forming galaxies with respect to
control fields. No clear overdensity of red galaxies is detected in the
surroundings of MRC1017-220 although the spatial distribution of the red
galaxies resembles a filament-like structure within which the radio galaxy is
embedded. In contrast, a significant overdensity of red galaxies is detected in
the field of MRC0156-252, ranging from a factor of 2-3 times the field density
at large scales (2.5Mpc, angular distance) up to a factor of 3-4 times the
field density within a 1Mpc radius of the radio galaxy. Half of these red
galaxies have colours consistent with red sequence models at z~2, with a large
fraction being bright (Ks<21.5, i.e. massive). In addition, we also find a
small group of galaxies within 5" of MRC0156-252 suggesting that the radio
galaxy has multiple companions within ~50 kpc. We conclude that the field of
MRC0156-252 shows many remarkable similarities with the well-studied
protocluster surrounding PKS1138-262 (z=2.16) suggesting that MRC0156-252 is
associated with a galaxy protocluster at z~2. |
Effects of New Viscosity Model on Cosmological Evolution: Bulk viscosity has been intrinsically existing in the observational cosmos
evolution with various effects for different cosmological evolution stages
endowed with complicated cosmic media. Normally in the idealized "standard
cosmology" the physical viscosity effect is often negligent in some extent by
assumptions, except for galaxies formation and evolution or the like
astrophysics phenomena. Actually we have not fully understood the physical
origin and effects of cosmic viscosity, including its functions for the
universe evolution in reality. In this present article we extend the concept of
temperature-dependent viscosity from classical statistical physics to
observational cosmology, especially we examine the cosmological effects with
possibility of the existence for two kinds of viscosity forms, which are
described by the Chapman's relation and Sutherland's formula respectively. By
considering that a modification of standard model with viscosity named as
$\Lambda$CDM-V model is constructed, which is supported by data fitting. In
addition to the enhancement to cosmic age value, the $\Lambda$CDM-V model
possesses other two pleasing features: the prediction about the
no-rip/singularity future and the mechanism of smooth transition from imperfect
cosmological models to perfect ones. | Implications of Fermi Observations for Hadronic Models of Radio Halos in
Clusters of Galaxies: We analyze the impact of the Fermi non-detection of gamma-ray emission from
clusters of galaxies on hadronic models for the origin of cluster radio halos.
In hadronic models, the inelastic proton-proton collisions responsible for the
production of the electron-positron population fueling the observed synchrotron
radio emission yield a gamma-ray flux, from the decay of neutral pions, whose
spectrum and normalization depend on the observed radio emissivity and on the
cluster magnetic field. We thus infer lower limits on the average cluster
magnetic field in hadronic models from the Fermi gamma-ray limits. We also
calculate the corresponding maximal energy density in cosmic rays and the
minimal-guaranteed gamma-ray flux from hadronic radio-halo models. We find that
the observationally most interesting cases correspond to clusters with large
radio emissivities featuring soft spectra. Estimates of the central magnetic
field values for those clusters are larger than, or close, to the largest
magnetic field values inferred from Faraday rotation measures of clusters,
placing tension on the hadronic origin of radio halos. In most cases, however,
we find that the Fermi data do not per se rule out hadronic models for cluster
radio halos as the expected gamma-ray flux can be pushed below the Fermi
sensitivity for asymptotically large magnetic fields. We also find that cosmic
rays do not contribute significantly to the cluster energy budget for nearby
radio halo clusters. |
Measuring the Hubble constant with kilonovae using the Expanding
Photosphere Method: While gravitational wave (GW) standard sirens from neutron star (NS) mergers
have been proposed to offer good measurements of the Hubble constant, we show
in this paper how a variation of the expanding photosphere method (EPM) or
spectral-fitting expanding atmosphere method, applied to the kilonovae (KNe)
associated with the mergers, can provide an independent distance measurement to
individual mergers that is potentially accurate to within a few percent. There
are four reasons why the KN-EPM overcomes the major uncertainties commonly
associated with this method in supernovae: 1) the early continuum is very
well-reproduced by a blackbody spectrum, 2) the dilution effect from electron
scattering opacity is likely negligible, 3) the explosion times are exactly
known due to the GW detection, and 4) the ejecta geometry is, at least in some
cases, highly spherical and can be constrained from line-shape analysis. We
provide an analysis of the early VLT/X-shooter spectra AT2017gfo showing how
the luminosity distance can be determined, and find a luminosity distance of
$D_L = 44.5\pm0.8$ Mpc in agreement with, but more precise than, previous
methods. We investigate the dominant systematic uncertainties, but our simple
framework, which assumes a blackbody photosphere, does not account for the full
time-dependent three-dimensional radiative transfer effects, so this distance
should be treated as preliminary. The luminosity distance corresponds to an
estimated Hubble constant of $H_0 = 67.0\pm 3.6$ km s$^{-1}$ Mpc$^{-1}$, where
the dominant uncertainty is due to the modelling of the host peculiar velocity.
We also estimate the expected constraints on $H_0$ from future KN-EPM-analysis
with the upcoming O4 and O5 runs of the LIGO collaboration GW-detectors, where
five to ten similar KNe would yield 1\% precision cosmological constraints. | CosmoGridV1: a simulated $w$CDM theory prediction for map-level
cosmological inference: We present CosmoGridV1: a large set of lightcone simulations for map-level
cosmological inference with probes of large scale structure. It is designed for
cosmological parameter measurement based on Stage-III photometric surveys with
non-Gaussian statistics and machine learning. CosmoGridV1 spans the $w$CDM
model by varying $\Omega_m$, $\sigma_8$, $w_0$, $H_0$, $n_s$, $\Omega_b$, and
assumes three degenerate neutrinos with $\sum m_\nu$ = 0.06 eV. This space is
covered by 2500 grid points on a Sobol sequence. At each grid point, we run 7
simulations with PkdGrav3 and store 69 particle maps at nside=2048 up to
$z$=3.5, as well as halo catalog snapshots. The fiducial cosmology has 200
independent simulations, along with their stencil derivatives. An important
part of CosmoGridV1 is the benchmark set of 28 simulations, which include
larger boxes, higher particle counts, and higher redshift resolution of shells.
They allow for testing if new types of analyses are sensitive to choices made
in CosmoGridV1. We add baryon feedback effects on the map level, using
shell-based baryon correction model. The shells are used to create maps of weak
gravitational lensing, intrinsic alignment, and galaxy clustering, using the
UFalcon code. The main part of CosmoGridV1 are the raw particle count shells
that can be used to create full-sky maps for a given $n(z)$. We also release
projected maps for a Stage-III forecast, as well as maps used previously in
KiDS-1000 deep learning constraints with CosmoGridV1. The data is available at
www.cosmogrid.ai. |
Constraint on a varying proton-to-electron mass ratio from H2 and HD
absorption at z = 2.34: Molecular hydrogen absorption in the damped Lyman-alpha system at z = 2.34
towards quasar Q1232+082 is analyzed in order to derive a constraint on a
possible temporal variation of the proton-to-electron mass ratio, mu, over
cosmological timescales. Some 106 H2 and HD transitions, covering the range
3290-3726 \AA, are analyzed with a comprehensive fitting technique, allowing
for the inclusion of overlapping lines associated with hydrogen molecules, the
atomic hydrogen lines in the Lyman-alpha forest as well as metal lines. The
absorption model, based on the most recent and accurate rest wavelength for H2
and HD transitions, delivers a value of dmu/mu = (19 +/- 9 +/- 5)x 10^(-6). An
attempt to correct the spectrum for possible long-range wavelength distortions
is made and the uncertainty on the distortion correction is included in the
total systematic uncertainty. The present result is an order of magnitude more
stringent than a previous measurement from the analysis of this absorption
system, based on a line-by-line comparison of only 12 prominent and isolated H2
absorption lines. This is consistent with other measurements of dmu/mu from 11
other absorption systems in showing a null variation of the proton-to-electron
mass ratio over a look-back time of 11 Gyrs. | Galaxy cluster optical mass proxies from probabilistic memberships: Robust galaxy cluster mass estimates are fundamental for constraining
cosmological parameters from counts. For this reason, it is essential to search
for tracers that, independent of the cluster's dynamical state, have a small
intrinsic scatter and can be easily inferred from observations. This work uses
a simulated data set to focus on photometric properties and explores different
optical mass proxies including richness, optical luminosity, and total stellar
mass. We have developed a probabilistic membership assignment that makes
minimal assumptions about the galaxy cluster properties, limited to a
characteristic radius, velocity dispersion, and spatial distribution. Applying
the estimator to over 919 galaxy clusters with $z_{phot}<$0.45 within a mass
range of $10^{12.8}$ to $10^{15}$ M$_\odot$, we obtain robust richness
estimates that deviate from the median true value (from simulations) by -0.01$
\pm $0.12. The scatter in the mass-observable relations is
$\sigma_{log_{10}(M|\mathcal{R})}=$0.181 $\pm$ 0.009 dex for richness,
$\sigma_{log_{10}(M|L_\lambda)}=$0.151 $\pm$ 0.007 dex for optical luminosity,
and $\sigma_{log_{10}(M|M_\lambda^*)}=$0.097 $\pm$ 0.005 dex for stellar mass.
We also discuss membership assignment, completeness and purity, and the
consequences of small centre and redshift offsets. We conclude that the
application of our method for photometric surveys delivers competitive cluster
mass proxies. |
An upper limit on the contribution of accreting white dwarfs to the type
Ia supernova rate: There is wide agreement that Type Ia supernovae (used as standard candles for
cosmology) are associated with the thermonuclear explosions of white dwarf
stars. The nuclear runaway that leads to the explosion could start in a white
dwarf gradually accumulating matter from a companion star until it reaches the
Chandrasekhar limit, or could be triggered by the merger of two white dwarfs in
a compact binary system. The X-ray signatures of these two possible paths are
very different. Whereas no strong electromagnetic emission is expected in the
merger scenario until shortly before the supernova, the white dwarf accreting
material from the normal star becomes a source of copious X-rays for ~1e7 yr
before the explosion. This offers a means of determining which path dominates.
Here we report that the observed X-ray flux from six nearby elliptical galaxies
and galaxy bulges is a factor of ~30-50 less than predicted in the accretion
scenario, based upon an estimate of the supernova rate from their K-band
luminosities. We conclude that no more than ~5 per cent of Type Ia supernovae
in early type galaxies can be produced by white dwarfs in accreting binary
systems, unless their progenitors are much younger than the bulk of the stellar
population in these galaxies, or explosions of sub-Chandrasekhar white dwarfs
make a significant contribution to the supernova rate. | A radio study of the double-double radio galaxy 3C293: We present radio continuum observations at frequencies ranging from $\sim$150
to 5000 MHz of the misaligned double-double radio galaxy, DDRG, 3C293
(J1352+3126) using the Giant Metrewave Radio Telescope (GMRT) and the Very
Large Array (VLA). The spectra of the outer lobes and the central source are
consistent with being straight, indicating spectral ages of $\lapp17-$23 Myr
for the outer lobes, and $\lapp$0.1 Myr for the central source. The
north-western lobe has a prominent hotspot suggesting that the interruption of
jet activity is $\lapp$0.1 Myr, consistent with the age of the inner double.
The time scale of interruption of jet activity appears significantly smaller
than observed in most other DDRGs which are often associated with giant radio
sources. These observations suggest that there is a wide range of time scales
of interruption of jet activity in active galaxies. |
One-loop corrections to the power spectrum in general single-field
inflation: We perform a thorough computation of the one-loop corrections from both
scalar and tensor degrees of freedom to the power spectrum of curvature
fluctuations for non-canonical Lagrangians in single-field inflation. We
consider models characterized by a small sound speed c_{s}, which produce large
non-Gaussianities. As expected, the corrections turn out to be inversely
proportional to powers of c_{s}; evaluating their amplitudes it is then
possible to derive some theoretical bounds on the sound speed by requesting the
conditions necessary for perturbation theory to hold. | The Galaxy Assembly and Interaction Neural Networks (GAINN) for
high-redshift JWST observations: We present the Galaxy Assembly and Interaction Neural Networks (GAINN), a
series of artificial neural networks for predicting the redshift, stellar mass,
halo mass, and mass-weighted age of simulated galaxies based on JWST
photometry. Our goal is to determine the best neural network for predicting
these variables at $11.5 < z < 15$. The parameters of the optimal neural
network can then be used to estimate these variables for real, observed
galaxies. The inputs of the neural networks are JWST filter magnitudes of a
subset of five broadband filters (F150W, F200W, F277W, F356W, and F444W) and
two medium-band filters (F162M and F182M). We compare the performance of the
neural networks using different combinations of these filters, as well as
different activation functions and numbers of layers. The best neural network
predicted redshift with normalized root mean squared error NRMS =
$0.009_{-0.002}^{+0.003}$, stellar mass with RMS = $0.073_{-0.008}^{+0.017}$,
halo mass with MSE = $ 0.022_{-0.004}^{+0.006}$, and mass-weighted age with RMS
= $10.866_{-1.410}^{+3.189}$. We also test the performance of GAINN on real
data from MACS0647-JD, an object observed by JWST. Predictions from GAINN for
the first projection of the object (JD1) have mean absolute errors $\langle
\Delta z \rangle <0.00228$, which is significantly smaller than with
template-fitting methods. We find that the optimal filter combination is F277W,
F356W, F162M, and F182M when considering both theoretical accuracy and
observational resources from JWST. |
Nature and nurture of early-type dwarf galaxies in low density
environments: We study stellar population parameters of a sample of 13 dwarf galaxies
located in poor groups of galaxies using high resolution spectra observed with
VIMOS at the ESO-VLT. LICK-indices were compared with Simple Stellar Population
models to derive ages, metallicities and [alpha/Fe]-ratios. Comparing the
dwarfs with a sample of giant ETGs residing in comparable environments we find
that the dwarfs are on average younger, less metal-rich, and less enhanced in
alpha-elements than giants. Age, Z, and [alpha/Fe] ratios are found to
correlate both with velocity dispersion and with morphology. We also find
possible evidence that low density environment (LDE) dwarfs experienced more
prolonged star formation histories than Coma dwarfs, however, larger samples
are needed to draw firm conclusions. | Super-resolution emulator of cosmological simulations using deep
physical models: We present an extension of our recently developed Wasserstein optimized model
to emulate accurate high-resolution features from computationally cheaper
low-resolution cosmological simulations. Our deep physical modelling technique
relies on restricted neural networks to perform a mapping of the distribution
of the low-resolution cosmic density field to the space of the high-resolution
small-scale structures. We constrain our network using a single triplet of
high-resolution initial conditions and the corresponding low- and
high-resolution evolved dark matter simulations from the Quijote suite of
simulations. We exploit the information content of the high-resolution initial
conditions as a well constructed prior distribution from which the network
emulates the small-scale structures. Once fitted, our physical model yields
emulated high-resolution simulations at low computational cost, while also
providing some insights about how the large-scale modes affect the small-scale
structure in real space. |
Assessing non-linear models for galaxy clustering II: model validation
and forecasts for Stage IV surveys: Accurate modelling of non-linear scales in galaxy clustering will be crucial
for data analysis of Stage IV galaxy surveys. A selection of competing
non-linear models must be made based on validation studies. We provide a
comprehensive set of forecasts of two different models for the halo redshift
space power spectrum, namely the commonly applied TNS model and an effective
field theory of large scale structure (EFTofLSS) inspired model. Using
simulation data and a least-$\chi^2$ analysis, we determine ranges of validity
for the models. We then conduct an exploratory Fisher analysis using the full
anisotropic power spectrum to investigate parameter degeneracies. We proceed to
perform an MCMC analysis utilising the monopole, quadrupole, and hexadecapole
spectra, with a restricted range of scales for the latter in order to avoid
biasing our growth rate, $f$, constraint. We find that the TNS model with a
Lorentzian damping and standard Eulerian perturbative modelling outperforms
other variants of the TNS model. Our MCMC analysis finds that the
EFTofLSS-based model may provide tighter marginalised constraints on $f$ at
$z=0.5$ and $z=1$ than the TNS model, despite having additional nuisance
parameters. However this depends on the range of scales used as well as the
fiducial values and priors on the EFT nuisance parameters. Finally, we extend
previous work to provide a consistent comparison between the Fisher matrix and
MCMC forecasts using the multipole expansion formalism, and find good agreement
between them. | A Baryonic Solution to the Missing Satellites Problem: It has been demonstrated that the inclusion of baryonic physics can alter the
dark matter densities in the centers of low-mass galaxies, making the central
dark matter slope more shallow than predicted in pure cold dark matter
simulations. This flattening of the dark matter profile can occur in the most
luminous subhalos around Milky Way-mass galaxies. Zolotov et al. (2012) have
suggested a correction to be applied to the central masses of dark matter-only
satellites in order to mimic the affect of (1) the flattening of the dark
matter cusp due to supernova feedback in luminous satellites, and (2) enhanced
tidal stripping due to the presence of a baryonic disk. In this paper, we apply
this correction to the z=0 subhalo masses from the high resolution, dark
matter-only Via Lactea II (VL2) simulation, and find that the number of massive
subhalos is dramatically reduced. After adopting a stellar mass to halo mass
relationship for the VL2 halos, and identifying subhalos that are (1) likely to
be destroyed by stripping and (2) likely to have star formation suppressed by
photo-heating, we find that the number of massive, luminous satellites around a
Milky Way-mass galaxy is in agreement with the number of observed satellites
around the Milky Way or M31. We conclude that baryonic processes have the
potential to solve the missing satellites problem. |
A QSO host galaxy and its Lyalpha emission at z=6.43: We report an optical detection of an extended structure around a QSO at
z=6.43 (CFHQSJ2329-0301, the highest redshift QSO currently known) in deep z'
and z_r-band images of the Subaru/Suprime-Cam. After a careful PSF (QSO)
subtraction, a structure in the z'-band extends more than 4'' on the sky
(R_e=11 kpc), and thus, is well-resolved (16sigma detection). The
PSF-subtracted z_r-band structure is in a similar shape to that in the z'-band,
but less significant with a 3 sigma detection. In the z'-band, a radial profile
of the QSO+host shows a clear excess over that of the averaged PSF in 0.8-3''
radius.
Since the z'-band includes a Lya emission at z=6.43, the z' flux is perhaps a
mixture of the host (continuum light) and its Lya emission, whereas the
z_r-band flux is from the host. Through a SED modeling, we estimate 40% of the
PSF-subtracted z'-band light is from the host (continuum) and 60% is from Lya
emission. The absolute magnitude of the host is M_{1450}=-23.9 (c.f.
M_{1450}=-26.4 for the QSO). A lower limit of the SFR(Lya) is 1.6 Msun yr^{-1}
with stellar mass ranging 6.2 x 10^8 to 1.1 x 10^10 Msun when 100 Myrs of age
is assumed. The detection shows that a luminous QSO is already harbored by a
large, star-forming galaxy in the early Universe only after ~840 Myr after the
big bang. The host may be a forming giant galaxy, co-evolving with a super
massive black hole. | The shape of galaxy dark matter halos in massive galaxy clusters:
Insights from strong gravitational lensing: We assess how much unused strong lensing information is available in the deep
\emph{Hubble Space Telescope} imaging and VLT/MUSE spectroscopy of the
\emph{Frontier Field} clusters. As a pilot study, we analyse galaxy cluster
MACS\,J0416.1-2403 ($z$$=$$0.397$, $M(R<200\,{\rm
kpc})$$=$$1.6$$\times$$10^{14}\msun$), which has 141 multiple images with
spectroscopic redshifts. We find that many additional parameters in a cluster
mass model can be constrained, and that adding even small amounts of extra
freedom to a model can dramatically improve its figures of merit. We use this
information to constrain the distribution of dark matter around cluster member
galaxies, simultaneously with the cluster's large-scale mass distribution. We
find tentative evidence that some galaxies' dark matter has surprisingly
similar ellipticity to their stars (unlike in the field, where it is more
spherical), but that its orientation is often misaligned. When non-coincident
dark matter and baryonic halos are allowed, the model improves by 35\%. This
technique may provide a new way to investigate the processes and timescales on
which dark matter is stripped from galaxies as they fall into a massive
cluster. Our preliminary conclusions will be made more robust by analysing the
remaining five \emph{Frontier Field} clusters. |
Cosmic decoherence: primordial power spectra and non-Gaussianities: We study the effect of quantum decoherence on the inflationary cosmological
perturbations. This process might imprint specific observational signatures
revealing the quantum nature of the inflationary mechanism being related to the
longstanding issue of the quantum-to-classical transition of inflationary
fluctuations. Several works have investigated the effect of quantum decoherence
on the statistical properties of primordial fluctuations. In particular, it has
been shown that cosmic decoherence leads to corrections to the curvature power
spectrum predicted by standard slow-roll inflation. Equally interesting, a non
zero curvature trispectrum has been shown to be purely induced by cosmic
decoherence, but surprisingly, decoherence seems not to generate any
bispectrum. We further develop such an analysis by adopting a generalized form
of the pointer observable, showing that decoherence does induce a non vanishing
curvature bispectrum and providing a specific underlying concrete physical
process. Present constraints on primordial bispectra allow to put an upper
bound on the strength of the environment-system interaction. In full
generality, the decoherence-induced bispectrum can be scale dependent provided
one imposes the corresponding correction to the power spectrum to be scale
independent. Such scale dependence on the largest cosmological scales might
represent a distinctive imprint of the quantum decoherence process taking place
during inflation. We also provide a criterion that allows to understand when
cosmic decoherence induces scale independent corrections, independently of the
type of environment considered. As a final result, we study the effect of
cosmic decoherence on tensor perturbations and we derive the decoherence
corrected tensor-to-scalar perturbation ratio. In specific cases, decoherence
induces a blue tilted correction to the standard tensor power spectrum. | Determination of the abundance of cosmic matter via the cell count
moments of the galaxy distribution (1): We demonstrate that accurate and precise information about the matter content
of the universe can be retrieved via a simple cell count analysis of the 3D
spatial distribution of galaxies. A new clustering statistic, the {\it galaxy
clustering ratio} $\eta$, is the key in this process. This is defined as the
ratio between one- and two-point second-order moments of the smoothed galaxy
density distribution. The distinguishing feature of this statistic is its
universality: on large cosmic scales both galaxies (in redshift space) and mass
(in real space) display the same $\eta$ amplitude. This quantity, in addition,
does not evolve as a function of redshift. As a consequence, the $\eta$
statistic provides insight into characteristic parameters of the real-space
power spectrum of mass density fluctuations without the need to specify the
galaxy biasing function, a model for galaxy redshift distortions nor the
growing mode of density ripples. We demonstrate the method with the luminous
red galaxy (LRG) sample extracted from the spectroscopic Sloan Digital Sky
Survey (SDSS) data release 7 (DR7) catalogue. Taking weak (flat) priors of the
curvature of the universe ($\Omega_k$) and of the constant value of the dark
energy equation of state ($w$), and strong (gaussian) priors of the physical
baryon density $\Omega_bh^2$, of the Hubble constant $H_0$ and of the spectral
index of primordial density perturbations $n_s$, we estimate the abundance of
matter with a relative error of 8% ($\Omega_m= 0.283\pm0.023$). We expect that
this approach will be instrumental in searching for evidence of new physics
beyond the standard model of cosmology and in planning future redshift surveys
such as BigBOSS or EUCLID. |
A Detailed Gravitational Lens Model Based on Submillimeter Array and
Keck Adaptive Optics Imaging of a Herschel-ATLAS Sub-millimeter Galaxy at
z=4.243: We present high-spatial resolution imaging obtained with the Submillimeter
Array (SMA) at 880um and the Keck Adaptive Optics (AO) system at Ks-band of a
gravitationally lensed sub-millimeter galaxy (SMG) at z=4.243 discovered in the
Herschel-Astrophysical Terahertz Large Area Survey. The SMA data (angular
resolution ~0.6") resolve the dust emission into multiple lensed images, while
the Keck AO Ks-band data (angular resolution ~0.1") resolve the lens into a
pair of galaxies separated by 0.3". We present an optical spectrum of the
foreground lens obtained with the Gemini-South telescope that provides a lens
redshift of z_lens = 0.595 +/- 0.005. We develop and apply a new lens modeling
technique in the visibility plane that shows that the SMG is magnified by a
factor of mu = 4.1 +/- 0.2 and has an intrinsic infrared (IR) luminosity of
L_IR = (2.1 +/- 0.2) x 10^13 Lsun. We measure a half-light radius of the
background source of r_s = 4.4 +/- 0.5 kpc which implies an IR luminosity
surface density of Sigma_IR = (3.4 +/- 0.9) x 10^11 Lsun kpc^-2, a value that
is typical of z > 2 SMGs but significantly lower than IR luminous galaxies at
z~0. The two lens galaxies are compact (r_lens ~ 0.9 kpc) early-types with
Einstein radii of theta_E1 = 0.57 +/- 0.01 and theta_E2 = 0.40 +/- 0.01 that
imply masses of M_lens1 = (7.4 +/- 0.5) x 10^10 Msun and M_lens2 = (3.7 +/-
0.3) x 10^10 Msun. The two lensing galaxies are likely about to undergo a
dissipationless merger, and the mass and size of the resultant system should be
similar to other early-type galaxies at z~0.6. This work highlights the
importance of high spatial resolution imaging in developing models of strongly
lensed galaxies discovered by Herschel. | Mass functions and bias of dark matter halos: We revisit the study of the mass functions and the bias of dark matter halos.
Focusing on the limit of rare massive halos, we point out that exact analytical
results can be obtained for the large-mass tail of the halo mass function. This
is most easily seen from a steepest-descent approach, that becomes
asymptotically exact for rare events. We also revisit the traditional
derivation of the bias of massive halos, associated with overdense regions in
the primordial density field. We check that the theoretical large-mass cutoff
agrees with the mass functions measured in numerical simulations. For halos
defined by a nonlinear threshold $\delta=200$ this corresponds to using a
linear threshold $\delta_L\simeq 1.59$ instead of the traditional value $\simeq
1.686$. We also provide a fitting formula that matches simulations over all
mass scales and obeys the exact large-mass tail. Next, paying attention to the
Lagrangian-Eulerian mapping (i.e. corrections associated with the motions of
halos), we improve the standard analytical formula for the bias of massive
halos. We check that our prediction, which contains no free parameter, agrees
reasonably well with numerical simulations. In particular, it recovers the
steepening of the dependence on scale of the bias that is observed at higher
redshifts, which published fitting formulae did not capture. This behavior
mostly arises from nonlinear biasing. |
Ultra-Compact Dwarfs in the Core of the Coma Cluster: We have discovered both a red and a blue subpopulation of Ultra-Compact Dwarf
(UCD) galaxy candidates in the Coma galaxy cluster. We analyzed deep F475W
(Sloan g) and F814W (I) Hubble Space Telescope images obtained with the
Advanced Camera for Surveys Wide Field Channel as part of the Coma Cluster
Treasury Survey and have fitted the light profiles of ~5000 point-like sources
in the vicinity of NGC 4874, one of the two central dominant galaxies of the
Coma cluster. Although almost all of these sources are globular clusters that
remain unresolved, we found that 52 objects have effective radii between ~10
and 66 pc, in the range spanned by Dwarf Globular Transition Objects (DGTO) and
UCDs. Of these 52 compact objects, 25 are brighter than M_V ~-11 mag, a
magnitude conventionally thought to separate UCDs and globular clusters. The
UCD/DGTO candidates have the same color and luminosity distribution as the most
luminous globular clusters within the red and blue subpopulations of the
immensely rich NGC 4874 globular cluster system. Unlike standard globular
clusters, blue and red UCD/DGTO subpopulations have the same median effective
radius. The spatial distribution of UCD/DGTO candidates reveal that they
congregate towards NGC 4874, and are not uniformly distributed. We find a
relative deficit of UCD/DGTOs compared with globular clusters in the inner 15
kpc around NGC 4874, however at larger radii UCD/DGTO and globular clusters
follow the same spatial distribution. | The WiggleZ Dark Energy Survey: Probing the Epoch of Radiation
Domination using Large Scale Structure: We place the most robust constraint to date on the scale of the turnover in
the cosmological matter power spectrum using data from the WiggleZ Dark Energy
Survey. We find this feature to lie at a scale of
$k_0=0.0160^{+0.0041}_{-0.0035}$ [h/Mpc] (68% confidence) for an effective
redshift of 0.62 and obtain from this the first-ever turnover-derived distance
and cosmology constraints: a measure of the cosmic distance-redshift relation
in units of the horizon scale at the redshift of radiation-matter equality
(r_H) of D_V(z=0.62)/r_H=18.3 (+6.3/-3.3) and, assuming a prior on the number
of extra relativistic degrees of freedom $N_{eff}=3$, constraints on the matter
density parameter $\Omega_Mh^2=0.136^{+0.026}_{-0.052}$ and on the redshift of
matter-radiation equality $z_{eq}=3274^{+631}_{-1260}$. All results are in
excellent agreement with the predictions of standard LCDM models. Our
constraints on the logarithmic slope of the power spectrum on scales larger
than the turnover is bounded in the lower limit with values only as low as -1
allowed, with the prediction of standard LCDM models easily accommodated by our
results. Lastly, we generate forecasts for the achievable precision of future
surveys at constraining $k_0$, $\Omega_Mh^2$, $z_{eq}$ and $N_{eff}$. We find
that BOSS should substantially improve upon the WiggleZ turnover constraint,
reaching a precision on $k_0$ of $\pm$9% (68% confidence), translating to
precisions on $\Omega_Mh^2$ and $z_{eq}$ of $\pm$10% (assuming a prior
$N_{eff}=3$) and on $N_{eff}$ of (+78/-56)% (assuming a prior
$\Omega_Mh^2=0.135$). This is sufficient precision to sharpen the constraints
on $N_{eff}$ from WMAP, particularly in its upper limit. For Euclid, we find
corresponding attainable precisions on $(k_0, \Omega_Mh^2, N_eff)$ of
(3,4,+17/-21)%. This represents a precision approaching our forecasts for the
Planck Surveyor. |
CosRayMC: a global fitting method in studying the properties of the new
sources of cosmic e$^{\pm}$ excesses: Recently PAMELA collaboration published the cosmic nuclei and electron
spectra with high precision, together with the cosmic antiproton data updated,
and the Fermi-LAT collaboration also updated the measurement of the total
$e^+e^-$ spectrum to lower energies. In this paper we develop a Markov Chain
Monte Carlo (MCMC) package {\it CosRayMC}, based on the GALPROP cosmic ray
propagation model to study the implications of these new data. It is found that
if only the background electrons and secondary positrons are considered, the
fit is very bad with $\chi_{\rm red}^2 \approx 3.68$. Taking into account the
extra $e^+e^-$ sources of pulsars or dark matter annihilation we can give much
better fit to these data, with the minimum $\chi_{\rm red}^2 \approx 0.83$.
This means the extra sources are necessary with a very high significance in
order to fit the data. However, the data show little difference between pulsar
and dark matter scenarios. Both the background and extra source parameters are
well constrained with this MCMC method. Including the antiproton data, we
further constrain the branching ratio of dark matter annihilation into quarks
$B_q<0.5%$ at $2\sigma$ confidence level. The possible systematical
uncertainties of the present study are discussed. | The morphology-density relation of galaxies around MACSJ0717.5+3745: We use an 18' x 9' mosaic of ACS images covering the entire large-scale
structure around the X-ray luminous cluster MACSJ0717.5 (z=0.545) to study the
morphology of galaxies at the cluster redshift. We find the global fraction of
morphological types of galaxies to be consistent with results in the
literature. Interestingly, we find that the fraction of S0s also correlates
with local galaxy density, in contrast to the findings of a study of the cores
of 10 clusters at similar redshift by Dressler et al. We suggest that this
apparent inconsistency is due to differences in the spatial coverage around
clusters, which is supported by the fact that the correlation disappears for
S0s within a radius of 0.6R_200 of MACSJ0717. We interpret this result as
evidence of the morphology-density relation being caused by a combination of
morphological transformation triggered by galaxy-galaxy interactions, and
effects related to the formation and evolution of large-scale structure. In
environments of low to intermediate density, where galaxy-galaxy interactions
are frequent and efficient, the observed pronounced morphology-density relation
for S0s reflects the density dependence of the interaction cross section. In
clusters, however, the correlation disappears for S0s, as the much higher
galaxy velocities in clusters not only lower the interaction cross section, but
also cause a spatial redistribution of galaxies that all but destroys such a
correlation. This argument does not hold for elliptical galaxies in clusters
which, having formed much earlier, have settled into the large-scale cluster
potential; hence the morphology-density relation for cluster ellipticals may
reflect primarily the state of advanced dynamical relaxation of this population
within the cluster rather than a causal link to the environment responsible for
the morphological transformation of galaxies. |
Understanding the Observed Evolution of the Galaxy Luminosity Function
from z=6-10 in the Context of Hierarchical Structure Formation: Recent observations of the Lyman-break galaxy (LBG) luminosity function (LF)
from z~6-10 show a steep decline in abundance with increasing redshift.
However, the LF is a convolution of the mass function of dark matter halos
(HMF)--which also declines sharply over this redshift range--and the
galaxy-formation physics that maps halo mass to galaxy luminosity. We consider
the strong observed evolution in the LF from z~6-10 in this context and
determine whether it can be explained solely by the behavior of the HMF. From
z~6-8, we find a residual change in the physics of galaxy formation
corresponding to a ~0.5 dex increase in the average luminosity of a halo of
fixed mass. On the other hand, our analysis of recent LF measurements at z~10
shows that the paucity of detected galaxies is consistent with almost no change
in the average luminosity at fixed halo mass from z~8. The LF slope also
constrains the variation about this mean such that the luminosity of galaxies
hosted by halos of the same mass are all within about an order-of-magnitude of
each other. We show that these results are well-described by a simple model of
galaxy formation in which cold-flow accretion is balanced by star formation and
momentum-driven outflows. If galaxy formation proceeds in halos with masses
down to 10^8 Msun, then such a model predicts that LBGs at z~10 should be able
to maintain an ionized intergalactic medium as long as the ratio of the
clumping factor to the ionizing escape fraction is C/f_esc < 10. | Consistency of Planck Data With Power-Law Primordial Scalar Power
Spectrum: In this work we explore the possibility of variations in the primordial
scalar power spectrum around the power-law shape, as predicted by single-field
slow-roll inflationary scenarios. We search for the trace of these fluctuations
in a semi-blind, model-independent way on the observations of the Cosmic
Microwave Background (CMB) sky. In particular we use two sets of perturbation
patterns, specific patterns with typical features such as oscillations, bumps
and transitions, as well as perturbation modes, constructed from the
eigenanalysis of the forecasted or measured covariance of perturbation
parameters. These modes, in principle, span the parameter space of all possible
perturbations to the primordial spectrum, and when rank-ordered, the ones with
the highest detectability would suffice to explore the constrainable features
around the power-law spectrum in a data-driven (and not theoretically-biased)
manner. With Planck measurements of CMB anisotropies, the amplitudes of all
perturbation patterns considered in this work are found to be consistent with
zero. This finding confirms, in the absence of theoretical biases, the
consistency of the Planck data with the assumption of power-law inflationary
pattern for the primordial spectrum. |
An Accurate Comprehensive Approach to Substructure: III. Masses and
Formation Times of the Host Haloes: With this Paper we complete a comprehensive study of substructure in dark
matter haloes. In Paper I we derived the radial distribution and mass function
(MF) of accreted subhaloes (scaled to the radius and mass of the host halo) and
showed they are essentially universal. This is not the case, however, for those
of stripped subhaloes, which depend on halo mass and assembly history. In Paper
II we derived these latter properties in the simplest case of purely accreting
haloes. Here we extend the study to ordinary haloes having suffered major
mergers. After showing that all the properties of substructure are encoded in
the mean truncated-to-original subhalo mass ratio profile, we demonstrate that
the dependence of the subhalo MF on halo mass arises from their mass-dependent
concentration, while the shape of the subhalo radial distribution depends on
the time of the last major merger of the host halo. In this sense, the latter
property is a better probe of halo formation time than the former.
Unfortunately, this is not the case for the radial distribution of satellites
as this profile is essentially disconnected from subhalo stripping and the
properties of accreted subhaloes are independent of the halo formation time. | A covariant approach to general field space metric in multi-field
inflation: We present a covariant formalism for general multi-field system which enables
us to obtain higher order action of cosmological perturbations easily and
systematically. The effects of the field space geometry, described by the
Riemann curvature tensor of the field space, are naturally incorporated. We
explicitly calculate up to the cubic order action which is necessary to
estimate non-Gaussianity and present those geometric terms which have not yet
known before. |
Dark Energy Survey Year 1 results: Validation of weak lensing cluster
member contamination estimates from P(z) decomposition: Weak lensing source galaxy catalogs used in estimating the masses of galaxy
clusters can be heavily contaminated by cluster members, prohibiting accurate
mass calibration. In this study we test the performance of an estimator for the
extent of cluster member contamination based on decomposing the photometric
redshift $P(z)$ of source galaxies into contaminating and background
components. We perform a full scale mock analysis on a simulated sky survey
approximately mirroring the observational properties of the Dark Energy Survey
Year One observations (DES Y1), and find excellent agreement between the true
number profile of contaminating cluster member galaxies in the simulation and
the estimated one. We further apply the method to estimate the cluster member
contamination for the DES Y1 redMaPPer cluster mass calibration analysis, and
compare the results to an alternative approach based on the angular correlation
of weak lensing source galaxies. We find indications that the correlation based
estimates are biased by the selection of the weak lensing sources in the
cluster vicinity, which does not strongly impact the $P(z)$ decomposition
method. Collectively, these benchmarks demonstrate the strength of the $P(z)$
decomposition method in alleviating membership contamination and enabling
highly accurate cluster weak lensing studies without broad exclusion of source
galaxies, thereby improving the total constraining power of cluster mass
calibration via weak lensing. | Intracluster supernovae in the Multi-epoch Nearby Cluster Survey: The Multi-Epoch Nearby Cluster Survey (MENeaCS) has discovered twenty-three
cluster Type Ia supernovae (SNe) in the 58 X-ray selected galaxy clusters (0.05
< z < 0.15) surveyed. Four of our SN Ia events have no host galaxy on close
inspection, and are likely intracluster SNe. Deep image stacks at the location
of the candidate intracluster SNe put upper limits on the luminosities of faint
hosts, with M_{r} > -13.0 mag and M_{g} > -12.5 mag in all cases. For such
limits, the fraction of the cluster luminosity in faint dwarfs below our
detection limit is <0.1%, assuming a standard cluster luminosity function. All
four events occurred within ~600 kpc of the cluster center (projected), as
defined by the position of the brightest cluster galaxy, and are more centrally
concentrated than the cluster SN Ia population as a whole. After accounting for
several observational biases that make intracluster SNe easier to discover and
spectroscopically confirm, we calculate an intracluster stellar mass fraction
of 0.16^{+0.13}_{-0.09} (68% CL) for all objects within R_{200}. If we assume
that the intracluster stellar population is exclusively old, and the cluster
galaxies themselves have a mix of stellar ages, we derive an upper limit on the
intracluster stellar mass fraction of <0.47 (84% one-sided CL). When combined
with the intragroup SNe results of McGee & Balogh, we confirm the declining
intracluster stellar mass fraction as a function of halo mass reported by
Gonzalez and collaborators. (Abridged) |
The velocity field in MOND cosmology: The recently developed code for N-body/hydrodynamics simulations in Modified
Newtonian Dynamics (MOND), known as RAyMOND, is used to investigate the
consequences of MOND on structure formation in a cosmological context, with a
particular focus on the velocity field. This preliminary study investigates the
results obtained with the two formulations of MOND implemented in RAyMOND, as
well as considering the effects of changing the choice of MOND interpolation
function, and the cosmological evolution of the MOND acceleration scale. The
simulations are contrived such that structure forms in a background cosmology
that is similar to $\Lambda$CDM, but with a significantly lower matter content.
Given this, and the fact that a fully consistent MOND cosmology is still
lacking, we compare our results with a standard $\Lambda$CDM simulation, rather
than observations. As well as demonstrating the effectiveness of using RAyMOND
for cosmological simulations, it is shown that a significant enhancement of the
velocity field is likely an unavoidable consequence of the gravitational
modification implemented in MOND, and may represent a clear observational
signature of such a modification. It is further suggested that such a signal
may be clearest in intermediate density regions such as cluster outskirts and
filaments. | Impact of next-to-leading order contributions to CMB lensing: In this Letter we study the impact on cosmological parameter estimation, from
present and future surveys, due to lensing corrections on CMB temperature and
polarization anisotropies beyond leading order. In particular, we show how
post-Born corrections, LSS effects and the correction due to the change in the
polarization direction between the emission at the source and the detection at
the observer, are non-negligible in the determination of the polarization
spectra. They have to be taken into account for an accurate estimation of
cosmological parameters sensitive to or even based on these spectra. We study
in detail the impact of higher order lensing on the determination of the
tensor-to-scalar ratio $r$ and on the estimation of the effective number of
relativistic species $N_\text{eff}$. We find that neglecting higher order
lensing terms can lead to misinterpreting these corrections as a primordial
tensor-to-scalar ratio of about $\mathcal{O}(10^{-3})$. Furthermore, it leads
to a shift of the parameter $N_\text{eff}$ by nearly two sigma considering the
level of accuracy aimed by future S4 surveys. |
Channeling in direct dark matter detection III: channeling fraction in
CsI crystals: The channeling of the ion recoiling after a collision with a WIMP changes the
ionization signal in direct detection experiments, producing a larger signal
scintillation or ionization than otherwise expected. We give estimates of the
fraction of channeled recoiling ions in CsI crystals using analytic models
produced since the 1960's and 70's to describe channeling and blocking effects. | The Cluster Birthline and the formation of stellar clusters in M33: We present a new method to analyze the IMF at its high mass end in young
stellar clusters, which rely on two integrated observables: the cluster
bolometric and Halpha luminosity. Using several cluster samples selected in M33
we show that a stochastically sampled universal IMF is in better agreement with
the data than a truncated IMF whose maximum stellar mass depends on cluster
mass. We also discuss the possibility that a delayed formation of massive stars
is taking place in low density star forming regions as an alternative to a
strong leakage of ionizing photons from HII regions of young luminous clusters. |
The Relative Role of Galaxy Mergers and Cosmic Flows in Feeding Black
Holes: Using a set of zoomed-in cosmological simulations of high-redshift
progenitors of massive galaxies, we isolate and trace the history of gas that
is accreted by central supermassive black holes. We determine the origins of
the accreted gas, in terms of whether it entered the galaxy during a merger
event or was smoothly accreted. Furthermore, we designate whether the smoothly
accreted gas is accreted via a cold flow or is shocked upon entry into the
halo. For moderate-mass (10^6 - 10^7 Msun) black holes at z ~ 4, there is a
preference to accrete cold flow gas than gas of shocked or merger origin.
However, this result is a consequence of the fact that the entire galaxy has a
higher fraction of gas from cold flows. In general, each black hole tends to
accrete the same fractions of smooth- and merger-accreted gas as is contained
in its host galaxy, suggesting that once gas enters a halo it becomes
well-mixed, and its origins are erased. We find that the angular momentum of
the gas upon halo entry is a more important factor; black holes preferentially
accrete gas that had low angular momentum when it entered the galaxy,
regardless of whether it was accreted smoothly or through mergers. | Collapsing Domain Wall Networks: Impact on Pulsar Timing Arrays and
Primordial Black Holes: Unstable domain wall (DW) networks in the early universe are cosmologically
viable and can emit a large amount of gravitational waves (GW) before
annihilating. As such, they provide an interpretation for the recent signal
reported by Pulsar Timing Array (PTA) collaborations. A related important
question is whether such a scenario also leads to significant production of
Primordial Black Holes (PBH). We investigate both GW and PBH production using
3D numerical simulations in an expanding background, with box sizes up to
$N=3240$, including the annihilation phase. We find that: i) the network decays
exponentially, i.e. the false vacuum volume drops as $\sim \exp(-\eta^3)$, with
$\eta$ the conformal time; ii) the GW spectrum is larger than traditional
estimates by more than one order of magnitude, due to a delay between DW
annihilation and the sourcing of GWs. We then present a novel semi-analytical
method to estimate the PBH abundances: rare false vacuum pockets of
super-Hubble size collapse to PBHs if their energy density becomes comparable
to the background when they cross the Hubble scale. Smaller (but more abundant)
pockets will instead collapse only if they are close to spherical. This
introduces very large uncertainties in the final PBH abundance. The first
phenomenological implication is that the DW interpretation of the PTA signal is
compatible with observational constraints on PBHs, within the uncertainties.
Second, in a different parameter region, the dark matter can be entirely in the
form of asteroid-mass PBHs from the DW collapse. Remarkably, this would also
lead to a GW background in the observable range of LIGO-Virgo-KAGRA and future
interferometers, such as LISA and Einstein Telescope. |
The REACH radiometer for detecting the 21-cm hydrogen signal from
redshift 7.5 to 28: Observations of the 21-cm line from primordial hydrogen promise to be one of
the best tools to study the early epochs of the Universe: the Dark Ages, the
Cosmic Dawn, and the subsequent Epoch of Reionization. In 2018, the EDGES
experiment caught the attention of the cosmology community with a potential
detection of an absorption feature in the sky-averaged radio spectrum centred
at 78 MHz. The feature is deeper than expected, and, if confirmed, would call
for new physics. However, different groups have re-analyzed the EDGES data and
questioned the reliability of the signal. The Radio Experiment for the Analysis
of Cosmic Hydrogen (REACH) is a sky-averaged 21-cm experiment aiming at
improving the current observations by tackling the issues faced by current
instruments related to residual systematic signals in the data. The novel
experimental approach focuses on detecting and jointly explaining these
systematics together with the foregrounds and the cosmological signal using
Bayesian statistics. To achieve this, REACH features simultaneous observations
with two different antennas, an ultra wideband system (redshift range 7.5 to
28), and a receiver calibrator based on in-field measurements. Simulated
observations forecast percent-level constraints on astrophysical parameters,
potentially opening up a new window to the infant Universe. | Is dynamic heating of stellar disk inevitable?: Major mergers or/and the repeated minor mergers lead to dynamical heating of
disks of galaxies. We analyze the available data on the velocity dispersion of
stellar disks of S-S0 galaxies, including the new observational data obtained
at 6m telescope of SAO RAS. As a measure of dynamical (over)heating, we use the
ratio of the observed velocity dispersion to the minimal dispersion which
provides the local stability of the stellar disks with respect to gravitational
perturbations. We came to conclusion that stellar disks in a significant part
of galaxies (including LSB and some S0 galaxies) are close to the marginal
stability condition (or are slightly overheated) -- at least at radial
distances $r\sim$ 2-3 radial scalelenghts. It enables to constrain the role of
merging in the heating of stellar disks: in many cases it seems to be
non-efficient. Marginal stability condition may also be successfully used to
estimate the mass of a disk and the midplane volume gas (stars) densities on
the basis of kinematic measurements. |
Density perturbations in the gas of wormholes: The observed dark matter phenomenon is attributed to the presence of a gas of
wormholes. We show that due to topological polarization effects the background
density of baryons generates non-vanishing values for wormhole rest masses. We
infer basic formulas for the scattering section between baryons and wormholes
and equations of motion. Such equations are then used for the kinetic and
hydrodynamic description of the gas of wormholes. In the Newtonian
approximation we consider the behavior of density perturbations and show that
at very large distances wormholes behave exactly like heavy non-baryon
particles, thus reproducing all features of CDM models. At smaller scales (at
galaxies) wormholes strongly interact with baryons and cure the problem of
cusps. We also show that collisions of wormholes and baryons lead to some
additional damping of the Jeans instability in baryons. | Halo assembly in cold and warm dark matter during the JWST frontier
epoch: The JWST mission is in the process of probing the galaxy mass function at
$z>10$, when conceivably any delay in halo assembly due to the presence of a
dwarf galaxy-scale power spectrum cutoff may drastically suppress the number of
galaxies relative to the cold dark matter (CDM) expectation. We employ N-body
simulations of CDM and warm dark matter (WDM) to explore how the difference in
halo collapse time between these models scales with $z=0$ descendant halo mass.
We demonstrate that collapse begins first for the most massive haloes, and the
delay in collapse time between CDM and WDM haloes correlates inversely with
descendant mass. We thus infer that only present-day dwarf galaxies exhibit any
difference in their assembly history between CDM and WDM at $z=10$, and
therefore support previous studies that have found JWST is unlikely to
determine whether our Universe is better described by the CDM cosmology or the
WDM cosmology without favourable lensing studies. |
On the HI column density - radio source size anti-correlation in compact
radio sources: Existing studies of the atomic hydrogen gas content in distant galaxies,
through the absorption of the 21-cm line, often infer that the total column
density is anti-correlated with the linear extent of the background radio
source. We investigate this interpretation, by dissecting the various
parameters from which the column density is derived, and find that the
relationship is driven primarily by the observed optical depth, which, for a
given absorber size, is anti-correlated with the linear size. Therefore, the
inferred anti-correlation is merely the consequence of geometry, in conjunction
with the assumption of a common spin temperature/covering factor ratio for each
member of the sample, an assumption for which there is scant observational
justification. While geometry can explain the observed correlation, many radio
sources comprise two radio lobes and so we model the projected area of a two
component emitter intercepted by a foreground absorber. From this, the observed
optical depth/linear size relationship is best reproduced through models which
approximate either of the two Fanaroff & Riley classifications, although the
observed scatter in the sample cannot be duplicated using a single deprojected
radio source size. Furthermore, the trend is best reproduced using an absorber
of diameter ~100 - 1000 pc, which is also the range of values of linear sizes
at which the 21-cm detection rate peaks. This may indicate that this is the
characteristic linear size of the absorbing gas structure. | Dark matter merging induced turbulence as an efficient engine for gas
cooling: We have performed a cosmological numerical simulation of primordial baryonic
gas collapsing onto a $3\times10^7$M$_{\odot}$ dark matter (DM) halo. We show
that the large scale baryonic accretion process and the merger of few
$\sim10^6$ M$_{\odot}$ DM halos, triggered by the gravitational potential of
the biggest halo, is enough to create super sonic ($\mathcal{M}>10$) shocks and
develop a turbulent environment. In this scenario the post shocked regions are
able to produced both H$_2$ and HD molecules very efficiently reaching maximum
abundances of $n_\mathrm{H_2}\sim10^{-2}n_\mathrm{H}$ and $n_\mathrm{HD}\sim
\mathrm{few}\times10^{-6}n_\mathrm{H}$, enough to cool the gas below 100K in
some regions. The kinetic energy spectrum of the turbulent primordial gas is
close to a Burgers spectrum, $\hat{E}_k\propto k^{-2}$, which could favor the
formation of low mass primordial stars. The solenoidal to total kinetic energy
ratio is $0.65\la R_k\la0.7$ for a wide range of wave numbers; this value is
close to $R_k\approx 2/3$ natural equipartition energy value of a random
turbulent flow. In this way turbulence and molecular cooling seem to work
together in order to produce potential star formation regions of cold and dense
gas in primordial environments. We conclude that both the mergers and the
collapse process onto the main DM halo provide enough energy to develop super
sonic turbulence which favor the molecular coolants formation: this mechanism,
which could be universal and the main route toward formation of the first
galaxies, is able to create potential star forming regions at high redshift. |
Suppression of HD-cooling in protogalactic gas clouds by Lyman-Werner
radiation: It has been shown that HD molecules can form efficiently in metal-free gas
collapsing into massive protogalactic halos at high redshift. The resulting
radiative cooling by HD can lower the gas temperature to that of the cosmic
microwave background, T_CMB=2.7(1+z)K, significantly below the temperature of a
few 100 K achievable via H_2-cooling alone, and thus reduce the masses of the
first generation of stars. Here we consider the suppression of HD-cooling by UV
irradiation in the Lyman-Werner (LW) bands. We include photo-dissociation of
both H_2 and HD, and explicitly compute the self-shielding and shielding of
both molecules by neutral hydrogen as well as the shielding of HD by H_2. We
use a simplified dynamical collapse model, and follow the chemical and thermal
evolution of the gas, in the presence of a UV background. We find that a LW
flux of J_crit = 1e-22 erg/cm^2/sr/s/Hz is able to suppress HD cooling and thus
prevent collapsing primordial gas from reaching temperatures below 100 K. The
main reason for the lack of HD cooling for J>J_crit is the partial
photo-dissociation of H_2, which prevents the gas from reaching sufficiently
low temperatures (T<150K) for HD to become the dominant coolant; direct HD
photo-dissociation is unimportant except for a narrow range of fluxes and
column densities. Since the prevention of HD-cooling requires only partial H_2
photo-dissociation, the critical flux J_crit is modest, and is below the UV
background required to reionize the universe at redshift z=10-20. We conclude
that HD-cooling can reduce the masses of typical stars only in rare halos
forming well before the epoch of reionization. | Mid-infrared spectroscopy of high-redshift 3CRR sources: Using the Spitzer Space Telescope, we have obtained rest frame 9-16mu spectra
of 11 quasars and 9 radio galaxies from the 3CRR catalog at redshifts
1.0<z<1.4. This complete flux-limited 178MHz-selected sample is unbiased with
respect to orientation and therefore suited to study orientation-dependent
effects in the most powerful active galactic nuclei (AGN). The mean radio
galaxy spectrum shows a clear silicate absorption feature (tau_9.7mu = 1.1)
whereas the mean quasar spectrum shows silicates in emission. The mean radio
galaxy spectrum matches a dust-absorbed mean quasar spectrum in both shape and
overall flux level. The data for individual objects conform to these results.
The trend of the silicate depth to increase with decreasing core fraction of
the radio source further supports that for this sample, orientation is the main
driver for the difference between radio galaxies and quasars, as predicted by
AGN unification. However, comparing our high-z sample with lower redshift 3CRR
objects reveals that the absorption of the high-z radio galaxy MIR continuum is
lower than expected from a scaled up version of lower luminosity sources, and
we discuss some effects that may explain these trends. |
A generalized local ansatz and its effect on halo bias: Motivated by the properties of early universe scenarios that produce
observationally large local non-Gaussianity, we perform N-body simulations with
non-Gaussian initial conditions from a generalized local ansatz. The bispectra
are schematically of the local shape, but with scale-dependent amplitude. We
find that in such cases the size of the non-Gaussian correction to the bias of
small and large mass objects depends on the amplitude of non-Gaussianity
roughly on the scale of the object. In addition, some forms of the generalized
bispectrum alter the scale dependence of the non-Gaussian term in the bias by a
fractional power of k. These features may allow significant observational
constraints on the particle physics origin of any observed local
non-Gaussianity, distinguishing between scenarios where a single field or
multiple fields contribute to the curvature fluctuations. While analytic
predictions for the non-Gaussian bias agree qualitatively with the simulations,
we find numerically a stronger observational signal than expected. This
suggests that a more precise understanding of halo formation is needed to fully
explain the consequences of primordial non-Gaussianity | Constraining Cosmological and Galaxy Parameters using Strong
Gravitational Lensing Systems: Strong gravitational lensing along with the distance sum rule method can
constrain both cosmological parameters as well as density profiles of galaxies
without assuming any fiducial cosmological model. To constrain galaxy
parameters and cosmic curvature $(\Omega_{k0})$, we use the distance ratio data
from a recently compiled database of $161$ galactic scale strong lensing
systems. We use databases of supernovae type-Ia (Pantheon) and Gamma Ray Bursts
(GRBs) for calculating the luminosity distance. To study the model of the lens
galaxy, we consider a general lens model namely, the Extended Power-Law model.
Further, we take into account two different parametrisations of the mass
density power-law index $(\gamma)$ to study the dependence of $\gamma$ on
redshift. The best value of $\Omega_{k0}$ suggests a closed universe, though a
flat universe is accommodated at $68\%$ confidence level. We find that
parametrisations of $\gamma$ have a negligible impact on the best fit value of
the cosmic curvature parameter.
Furthermore, measurement of time delay can be a promising cosmographic probe
via "time delay distance" that includes the ratio of distances between the
observer, the lens and the source. We again use the distance sum rule method
with time-delay distance dataset of H0LiCOW to put constraints on the Cosmic
Distance Duality Relation (CDDR) and the cosmic curvature parameter
$(\Omega_{k0})$. For this we consider two different redshift-dependent
parametrisations of the distance duality parameter $(\eta)$. The best fit value
of $\Omega_{k0}$ clearly indicates an open universe. However, a flat universe
can be accommodated at $95\%$ confidence level. Further, at $95\%$ confidence
level, no violation of CDDR is observed. We believe that a larger sample of
strong gravitational lensing systems is needed in order to improve the
constraints on the cosmic curvature and distance duality parameter. |
The Observed Growth of Massive Galaxy Clusters I: Statistical Methods
and Cosmological Constraints: (Abridged) This is the first of a series of papers in which we derive
simultaneous constraints on cosmological parameters and X-ray scaling relations
using observations of the growth of massive, X-ray flux-selected galaxy
clusters. Our data set consists of 238 clusters drawn from the ROSAT All-Sky
Survey, and incorporates extensive follow-up observations using the Chandra
X-ray Observatory. Here we describe and implement a new statistical framework
required to self-consistently produce simultaneous constraints on cosmology and
scaling relations from such data, and present results on models of dark energy.
In spatially flat models with a constant dark energy equation of state, w, the
cluster data yield Omega_m=0.23 +- 0.04, sigma_8=0.82 +- 0.05, and w=-1.01 +-
0.20, marginalizing over conservative allowances for systematic uncertainties.
These constraints agree well and are competitive with independent data in the
form of cosmic microwave background (CMB) anisotropies, type Ia supernovae
(SNIa), cluster gas mass fractions (fgas), baryon acoustic oscillations (BAO),
galaxy redshift surveys, and cosmic shear. The combination of our data with
current CMB, SNIa, fgas, and BAO data yields Omega_m=0.27 +- 0.02, sigma_8=0.79
+- 0.03, and w=-0.96 +- 0.06 for flat, constant w models. For evolving w
models, marginalizing over transition redshifts in the range 0.05-1, we
constrain the equation of state at late and early times to be respectively
w_0=-0.88 +- 0.21 and w_et=-1.05 +0.20 -0.36. The combined data provide
constraints equivalent to a DETF FoM of 15.5. Our results highlight the power
of X-ray studies to constrain cosmology. However, the new statistical framework
we apply to this task is equally applicable to cluster studies at other
wavelengths. | The strongest gravitational lenses: III. The order statistics of the
largest Einstein radii: The Einstein radius (ER) of a gravitational lens encodes information about
decisive quantities such as halo mass, concentration, triaxiality, and
orientation with respect to the observer. Thus, the largest Einstein radii can
potentially be utilised to test the predictions of the LCDM model. Hitherto,
studies have focussed on the single largest observed ER. We extend those
studies by employing order statistics to formulate exclusion criteria based on
the n largest Einstein radii and apply these criteria to the strong lensing
analysis of 12 MACS clusters at z>0.5. We obtain the order statistics of
Einstein radii by a MC approach, based on the semi-analytic modelling of the
halo population on the past lightcone. After sampling the order statistics, we
fit a GEV distribution to the first-order distribution, which allows us to
derive analytic relations for the order statistics of the Einstein radii. We
find that the Einstein radii of the 12 MACS clusters are not in conflict with
the LCDM expectations. Our exclusion criteria indicate that, in order to
exhibit tension with the concordance model, one would need to observe
approximately twenty Einstein radii >30", ten >35" or five >42" in the range of
0.5<z<1.0 on the full sky. Furthermore, we find that, with increasing order,
the haloes with the largest Einstein radii are on average less aligned along
the line-of-sight and less triaxial. In general, the cumulative distribution
functions steepen for higher orders, giving them better constraining power.
(abridged) |
Maximum likelihood map-making with the Laser Interferometer Space
Antenna: Given the recent advances in gravitational-wave detection technologies, the
detection and characterisation of gravitational-wave backgrounds (GWBs) with
the Laser Interferometer Space Antenna (LISA) is a real possibility. To assess
the abilities of the LISA satellite network to reconstruct anisotropies of
different angular scales and in different directions on the sky, we develop a
map-maker based on an optimal quadratic estimator. The resulting maps are
maximum likelihood representations of the GWB intensity on the sky integrated
over a broad range of frequencies. We test the algorithm by reconstructing
known input maps with different input distributions and over different
frequency ranges. We find that, in an optimal scenario of well understood noise
and high frequency, high SNR signals, the maximum scales LISA may probe are
$\ell_{\rm max} \lesssim 15$. The map-maker also allows to test the directional
dependence of LISA noise, providing insight on the directional sky sensitivity
we may expect. | The (black hole mass)-(host spheroid luminosity) relation at high and
low masses, the quadratic growth of black holes, and intermediate-mass black
hole candidates: From a sample of 72 galaxies with reliable supermassive black hole masses
M_(bh), we derive the M_(bh)-(host spheroid luminosity, L) relation for (i) the
subsample of 24 core-Sersic galaxies with partially depleted cores, and (ii)
the remaining subsample of 48 Sersic galaxies. Using (K_s)-band 2MASS data, we
find the near-linear relation M_(bh) ~ L_(K_s)^(1.10+/-0.20) for the
core-Sersic spheroids thought to be built in additive dry merger events, while
M_(bh) ~ L_(K_s)^(2.73+/-0.55) for the Sersic spheroids built from gas-rich
processes. After converting literature B-band disk galaxy magnitudes into
inclination- and dust-corrected bulge magnitudes, via a useful new equation
presented herein, we obtain a similar result. Unlike with the M_(bh)-sigma
diagram, which is also updated here using the same galaxy sample, it remains
unknown whether barred and non-barred Sersic galaxies are offset from each
other in the M_(bh)-L diagram.
While black hole feedback has typically been invoked to explain what was
previously thought to be a nearly constant M_bh/M_sph mass ratio of ~0.2%, we
advocate that the near-linear M_bh-L and M_bh-M_sph relations observed at high
masses may have instead largely arisen from the additive dry merging of
galaxies. We argue that feedback results in a dramatically different scaling
relation, such that black hole mass scales roughly quadratically with the
spheroid mass in Sersic galaxies. We therefore introduce a revised cold-gas
'quasar' mode feeding equation for semi-analytical models to reflect what we
dub the "quadratic growth" of black holes in Sersic galaxies built amidst
gas-rich processes. Finally, we use our new Sersic M_bh-L equations to predict
the masses of candidate `intermediate mass' black holes in almost 50 low
luminosity spheroids containing AGN, finding many masses between that of
stellar mass black holes and supermassive black holes. |
Correcting the z~8 Galaxy Luminosity Function for Gravitational Lensing
Magnification Bias: We present a Bayesian framework to account for the magnification bias from
both strong and weak gravitational lensing in estimates of high-redshift galaxy
luminosity functions. We illustrate our method by estimating the $z\sim8$ UV
luminosity function using a sample of 97 Y-band dropouts (Lyman break galaxies)
found in the Brightest of Reionizing Galaxies (BoRG) survey and from the
literature. We find the luminosity function is well described by a Schechter
function with characteristic magnitude of $M^\star = -19.85^{+0.30}_{-0.35}$,
faint-end slope of $\alpha = -1.72^{+0.30}_{-0.29}$, and number density of
$\log_{10} \Psi^\star [\textrm{Mpc}^{-3}] = -3.00^{+0.23}_{-0.31}$. These
parameters are consistent within the uncertainties with those inferred from the
same sample without accounting for the magnification bias, demonstrating that
the effect is small for current surveys at $z\sim8$, and cannot account for the
apparent overdensity of bright galaxies compared to a Schechter function found
recently by Bowler et al. (2014a,b) and Finkelstein et al. (2014). We estimate
that the probability of finding a strongly lensed $z\sim8$ source in our sample
is in the range $\sim 3-15 \%$ depending on limiting magnitude. We identify one
strongly-lensed candidate and three cases of intermediate lensing in BoRG
(estimated magnification $\mu>1.4$) in addition to the previously known
candidate group-scale strong lens. Using a range of theoretical luminosity
functions we conclude that magnification bias will dominate wide field surveys
-- such as those planned for the Euclid and WFIRST missions -- especially at
$z>10$. Magnification bias will need to be accounted for in order to derive
accurate estimates of high-redshift luminosity functions in these surveys and
to distinguish between galaxy formation models. | Review of axino dark matter: We review the status of axino dark matter. Two hierarchy problems, the strong
CP problem and the gauge hierarchy problem, have led to introducing into
particle physics a spontaneously broken global Peccei-Quinn symmetry and a
softly broken supersymmetry, respectively. Combining them implies the presence
of not only an axion, but also of its scalar component, saxion, and their
fermionic partner, axino. Among these, the axion and the axino are attractive
dark matter candidates. Various possibilities for the axino as dark matter are
discussed. |
Non-universal BBN bounds on electromagnetically decaying particles: In Poulin and Serpico [Phys. Rev. Lett. 114, 091101 (2015)] we have recently
argued that when the energy of a photon injected in the primordial plasma falls
below the pair-production threshold, the universality of the non-thermal photon
spectrum from the standard theory of electromagnetic cascades onto a photon
background breaks down. We showed that this could reopen or widen the parameter
space for an exotic solution to the 'lithium problem'. Here we discuss another
application, namely the impact that this has on non-thermal big bang
nucleosynthesis constraints from 4He, 3He and 2H, using the parametric example
of monochromatic photon injection of different energies. Typically, we find
tighter bounds than those existing in the literature, up to more than one order
of magnitude. As a consequence of the non-universality of the spectrum, the
energy-dependence of the photodissociation cross-sections is important. We also
compare the constraints obtained with current level and future reach of cosmic
microwave background spectral distortion bounds. | The impact of mechanical AGN feedback on the formation of massive
early-type galaxies: We employ cosmological hydrodynamical simulations to investigate the effects
of AGN feedback on the formation of massive galaxies with present-day stellar
masses of $M_{stel} = 8.8 \times 10^{10} - 6.0 \times 10^{11} M_{sun}$. Using
smoothed particle hydrodynamics simulations with a pressure-entropy formulation
that allows an improved treatment of contact discontinuities and fluid mixing,
we run three sets of simulations of 20 halos with different AGN feedback
models: (1) no feedback, (2) thermal feedback, and (3) mechanical and radiation
feedback. We assume that seed black holes are present at early cosmic epochs at
the centre of emerging dark matter halos and trace their mass growth via gas
accretion and mergers with other black holes. Both feedback models successfully
recover the observed M_BH - sigma relation and black hole-to-stellar mass ratio
for simulated central early-type galaxies. The baryonic conversion efficiencies
are reduced by a factor of two compared to models without any AGN feedback at
all halo masses. However, massive galaxies simulated with thermal AGN feedback
show a factor of ~10-100 higher X-ray luminosities than observed. The
mechanical/radiation feedback model reproduces the observed correlation between
X-ray luminosities and velocity dispersion, e.g. for galaxies with sigma = 200
km/s, the X-ray luminosity is reduced from $10^{42}$ erg/s to $10^{40}$ erg/s.
It also efficiently suppresses late time star formation, reducing the specific
star formation rate from $10^{-10.5}$ $yr^{-1}$ to $10^{-14}$ $yr^{-1}$ on
average and resulting in quiescent galaxies since z=2, whereas the thermal
feedback model shows higher late time in-situ star formation rates than
observed. |
A First Look at creating mock catalogs with machine learning techniques: We investigate machine learning (ML) techniques for predicting the number of
galaxies (N_gal) that occupy a halo, given the halo's properties. These types
of mappings are crucial for constructing the mock galaxy catalogs necessary for
analyses of large-scale structure. The ML techniques proposed here distinguish
themselves from traditional halo occupation distribution (HOD) modeling as they
do not assume a prescribed relationship between halo properties and N_gal. In
addition, our ML approaches are only dependent on parent halo properties (like
HOD methods), which are advantageous over subhalo-based approaches as
identifying subhalos correctly is difficult. We test 2 algorithms: support
vector machines (SVM) and k-nearest-neighbour (kNN) regression. We take
galaxies and halos from the Millennium simulation and predict N_gal by training
our algorithms on the following 6 halo properties: number of particles, M_200,
\sigma_v, v_max, half-mass radius and spin. For Millennium, our predicted N_gal
values have a mean-squared-error (MSE) of ~0.16 for both SVM and kNN. Our
predictions match the overall distribution of halos reasonably well and the
galaxy correlation function at large scales to ~5-10%. In addition, we
demonstrate a feature selection algorithm to isolate the halo parameters that
are most predictive, a useful technique for understanding the mapping between
halo properties and N_gal. Lastly, we investigate these ML-based approaches in
making mock catalogs for different galaxy subpopulations (e.g. blue, red, high
M_star, low M_star). Given its non-parametric nature as well as its powerful
predictive and feature selection capabilities, machine learning offers an
interesting alternative for creating mock catalogs. | An extension of the Planck galaxy cluster catalogue: We present a catalogue of galaxy clusters detected in the Planck all-sky
Compton parameter maps and identified using data from the WISE and SDSS
surveys. The catalogue comprises about 3000 clusters in the SDSS fields. We
expect the completeness of this catalogue to be high for clusters with masses
larger than M_500 =~ 3x10^14 Msun, located at redshifts z<0.7. At redshifts
above z=~0.4, the catalogue contains approximately an order of magnitude more
clusters than the 2nd Planck Catalogue of Sunyaev-Zeldovich sources in the same
fields of the sky. This catalogue can be used for identification of massive
galaxy clusters in future large cluster surveys, such as the SRG/eROSITA
all-sky X-ray survey. |
Quantifying the CMB Degeneracy Between the Matter Density and Hubble
Constant in Current Experiments: We revisit the degeneracy between the Hubble constant, $H_0$, and matter
density, $\Omega_m$, for current cosmic microwave background (CMB) observations
within the standard $\Lambda CDM$ model. We show that Planck, Wilkinson
Microwave Anisotropy Probe (WMAP), South Pole Telescope (SPT), and Atacama
Cosmology Telescope Polarimeter (ACTPol) temperature power spectra produce
different values of the exponent $x$ from minimizing the variance of the
product $\Omega_mH_0^x$. The distribution of $x$ from the different data sets
does not follow the Markov Chain Monte Carlo (MCMC) best-fit values for $H_0$
or $\Omega_m$. Particularly striking is the difference between Planck
multipoles $\ell\leq800$ ($x=2.81$), and WMAP ($x = 2.94$), despite very
similar best-fit cosmologies. We use a Fisher matrix analysis to show that, in
fact, this range in exponent values is exactly as expected in $\Lambda CDM$
given the multipole coverage and power spectrum uncertainties for each
experiment. We show that the difference in $x$ from the Planck $\ell \leq 800$
and WMAP data is explained by a turning point in the relationship between $x$
and the maximum effective multipole, at around $\ell=700$. The value of $x$ is
determined by several physical effects, and we highlight the significant impact
of gravitational lensing for the high-multipole measurements. Despite the
spread of $H_0$ values from different CMB experiments, the experiments are
consistent with their sampling of the $\Omega_m-H_0$ degeneracy and do not show
evidence for the need for new physics or for the presence of significant
underestimated systematics according to these tests. The Fisher calculations
can be used to predict the $\Omega_m-H_0$ degeneracy of future experiments. | Halo Abundance Matching: accuracy and conditions for numerical
convergence: Accurate predictions of the abundance and clustering of dark matter haloes
play a key role in testing the standard cosmological model. Here, we
investigate the accuracy of one of the leading methods of connecting the
simulated dark matter haloes with observed galaxies -- the Halo Abundance
Matching (HAM) technique. We show how to choose the optimal values of the mass
and force resolution in large-volume N-body simulations so that they provide
accurate estimates for correlation functions and circular velocities for haloes
and their subhaloes -- crucial ingredients of the HAM method. At the 10%
accuracy, results converge for 50 particles for haloes and 150 particles for
progenitors subhaloes. In order to achieve this level of accuracy a number of
conditions should be satisfied. The force resolution for the smallest resolved
(sub)haloes should be in the range (0.1-0.3)rs, where rs is the scale radius of
(sub)haloes. The number of particles for progenitors of subhaloes should be
150. We also demonstrate that the two-body scattering plays a minor role for
the accuracy of N-body simulations thanks to the relatively small number of
crossing-times of dark matter in haloes, and the limited force resolution of
cosmological simulations. |
The size-luminosity relation at z=7 in CANDELS and its implication on
reionization: The exploration of the relation between galaxy sizes and other physical
parameters has provided important clues for understanding galaxy formation. We
use the CANDELS Deep+Wide surveys in the GOODS-South, UDS and EGS fields,
complemented by data from the HUDF09 program, to address the relation between
size and luminosity at z\sim7. We select 153 z-band drop-out galaxies in six
different fields characterized by a wide combination of depth and areal
coverage, ideally suited to sample without biases the observed size-magnitude
plane. Detailed simulations allow us to derive the completeness as a function
of size and magnitude and to quantify measurements errors/biases. We find that
the half light radius distribution function of z\sim7 galaxies fainter than
J=26.6 is peaked at <0.1 arcsec (or equivalently 0.5 kpc proper), while at
brighter magnitudes high-z galaxies are typically larger than ~0.15 arcsec. We
also find a well defined size-luminosity relation, Rh\simL^1/2. We compute the
Luminosity Function in the HUDF and P12HUDF fields, finding large spatial
variation on the number density of faint galaxies. Adopting the size
distribution and the size-luminosity relation found for faint galaxies at z=7,
we derive a mean slope of -1.7\pm0.1 for the luminosity function of LBGs at
this redshift. Using this LF, we find that the amount of ionizing photons
cannot keep the Universe re-ionized if the IGM is clumpy (C_HII>3) and the
Lyman continuum escape fraction of high-z LBGs is relatively low (f_esc<0.3).
With future CANDELS data, we can put severe limits to the role of galaxies in
the reionization of the Universe. | Matter density perturbation and power spectrum in running vacuum model: We investigate the matter density perturbation $\delta_m$ and power spectrum
$P(k)$ in the running vacuum model (RVM) with the cosmological constant being a
function of the Hubble parameter, given by $\Lambda = \Lambda_0 + 6 \sigma H
H_0+ 3\nu H^2$, in which the linear and quadratic terms of $H$ would originate
from the QCD vacuum condensation and cosmological renormalization group,
respectively. Taking the dark energy perturbation into consideration, we derive
the evolution equation for $\delta_m$ and find a specific scale $d_{cr}=2
\pi/k_{cr}$, which divides the evolution of the universe into the sub and
super-interaction regimes, corresponding to $k \ll k_{cr}$ and $k \gg k_{cr}$,
respectively. For the former, the evolution of $\delta_m$ has the same behavior
as that in the $\Lambda$CDM model, while for the latter, the growth of
$\delta_m$ is frozen (greatly enhanced) when $\nu + \sigma >(<)0$ due to the
couplings between radiation, matter and dark energy. It is clear that the
observational data rule out the cases with $\nu<0$ and $\nu + \sigma <0$, while
the allowed window for the model parameters is extremely narrow with $\nu,
|\sigma| \lesssim \mathcal{O}(10^{-7})$. |
CMASS galaxy sample and the ontological status of the cosmological
principle: The cosmological principle (CP), assuming spatially homogeneous and isotropic
background geometry in the cosmological scale, is a fundamental assumption in
modern cosmology. Recent observations of the galaxy redshift survey provide
relevant data to confront the principle with observation. We present a
homogeneity test for the matter distribution using the BOSS DR12 CMASS galaxy
sample and clarify the ontological status of the CP. As a homogeneity
criterion, we compare the observed data with similarly constructed random
distributions using the number count in the truncated cones method. Comparisons
are also made with three theoretical results using the same method: (i) the
dark matter halo mock catalogs from the N-body simulation, (ii) the log-normal
distributions derived from the theoretical matter power spectrum, and (iii)
direct estimation from the theoretical power spectrum. We show that the
observed distribution is statistically impossible as a random distribution up
to 300 Mpc/h in radius, which is around the largest statistically available
scale. However, comparisons with the three theoretical results show that the
observed distribution is consistent with these theoretically derived results
based on the CP. We show that the observed galaxy distribution (light) and the
simulated dark matter distribution (matter) are quite inhomogeneous even on a
large scale. Here, we clarify that there is no inconsistency surrounding the
ontological status of the CP in cosmology. In practice, the CP is applied to
the metric and the metric fluctuation is extremely small in all cosmological
scales. This allows the CP to be valid as the averaged background in metric.
The matter fluctuation, however, is decoupled from the small nature of metric
fluctuation in the subhorizon scale. What is directly related to the matter in
Einstein's gravity is the curvature, a quadratic derivative of the metric. | An exact Jacobi map in the geodesic light-cone gauge: The remarkable properties of the recently proposed geodesic light-cone (GLC)
gauge allow to explicitly solve the geodetic-deviation equation, and thus to
derive an exact expression for the Jacobi map J^A_B(s,o) connecting a generic
source s to a geodesic observer o in a generic space time. In this gauge J^A_B
factorizes into the product of a local quantity at s times one at o, implying
similarly factorized expressions for the area and luminosity distance. In any
other coordinate system J^A_B is simply given by expressing the GLC quantities
in terms of the corresponding ones in the new coordinates. This is explicitly
done, at first and second order, respectively, for the synchronous and Poisson
gauge-fixing of a perturbed, spatially-flat cosmological background, and the
consistency of the two outcomes is checked. Our results slightly amend previous
calculations of the luminosity-redshift relation and suggest a possible
non-perturbative way for computing the effects of inhomogeneities on
observations based on light-like signals. |
Halo Assembly Bias using properties of central galaxies in SDSS
redMaPPer clusters: The clustering of dark matter halos depends on the assembly history of halos
at fixed halo mass; a phenomenon referred to as \textit{halo assembly bias}.
Halo assembly bias is readily observed in cosmological simulations of dark
matter. However, it is difficult to detect it in observations. The
identification of galaxy or cluster properties correlated with the formation
time of the halo at fixed halo mass and the ability to select galaxy clusters
free from projection effects are the two most significant hurdles in the
observational detection of halo assembly bias. The latter, in particular, can
cause a misleading detection of halo assembly bias by boosting the amplitude of
lensing and clustering on large scales. This study uses twelve different
properties of central galaxies of SDSS redMaPPer clusters derived from
spectroscopy to divide the clusters into sub-samples. We test the dependence of
the clustering amplitude on these properties at fixed richness. We first infer
halo mass and bias using weak lensing signals around the clusters using shapes
of galaxies from the SDSS survey. We validate the bias difference between the
two subsamples using cluster-galaxy cross-correlations. This methodology allows
us to decouple the contamination due to the projection effects from the halo
assembly bias signals. We do not find any significant evidence of a difference
in the clustering amplitudes correlated with any of our explored properties.
Our results indicate that central galaxy properties may not correlate
significantly with the halo assembly histories at fixed richness. | Velocity Dispersions and Stellar Populations of the Most Compact and
Massive Early-Type Galaxies at Redshift ~1: We present Gran-Telescopio-Canarias/OSIRIS optical spectra of 4 of the most
compact and massive early-type galaxies in the Groth Strip Survey at redshift
z~1, with effective radii Reff=0.5-2.4 kpc and photometric stellar masses
Mstar=1.2-4x10^11 Msun. We find these galaxies have velocity dispersions
sigma=156-236 km/s. The spectra are well fitted by single stellar population
models with approximately 1 Gyr of age and solar metallicity. We find that: i)
the dynamical masses of these galaxies are systematically smaller by a factor
of ~6 than the published stellar masses using BRIJK photometry; ii) when
estimating stellar masses as 0.7xMdyn, a combination of passive luminosity
fading with mass/size growth due to minor mergers can plausibly evolve our
objects to match the properties of the local population of early-type galaxies. |
Simulations of Wide-Field Weak Lensing Surveys II: Covariance Matrix of
Real Space Correlation Functions: Using 1000 ray-tracing simulations for a {\Lambda}-dominated cold dark model
in Sato et al. (2009), we study the covariance matrix of cosmic shear
correlation functions, which is the standard statistics used in the previous
measurements. The shear correlation function of a particular separation angle
is affected by Fourier modes over a wide range of multipoles, even beyond a
survey area, which complicates the analysis of the covariance matrix. To
overcome such obstacles we first construct Gaussian shear simulations from the
1000 realizations, and then use the Gaussian simulations to disentangle the
Gaussian covariance contribution to the covariance matrix we measured from the
original simulations. We found that an analytical formula of Gaussian
covariance overestimates the covariance amplitudes due to an effect of finite
survey area. Furthermore, the clean separation of the Gaussian covariance
allows to examine the non-Gaussian covariance contributions as a function of
separation angles and source redshifts. For upcoming surveys with typical
source redshifts of z_s=0.6 and 1.0, the non-Gaussian contribution to the
diagonal covariance components at 1 arcminute scales is greater than the
Gaussian contribution by a factor of 20 and 10, respectively. Predictions based
on the halo model qualitatively well reproduce the simulation results, however
show a sizable disagreement in the covariance amplitudes. By combining these
simulation results we develop a fitting formula to the covariance matrix for a
survey with arbitrary area coverage, taking into account effects of the
finiteness of survey area on the Gaussian covariance. | Searching for Evidence of Energetic Feedback in Distant Galaxies: A
Galaxy Wide Outflow in a z~2 Ultraluminous Infrared Galaxy: Leading models of galaxy formation require large-scale energetic outflows to
regulate the growth of distant galaxies and their central black holes. However,
current observational support for this hypothesis at high redshift is mostly
limited to rare z>2 radio galaxies. Here we present Gemini-North NIFS Intregral
Field Unit (IFU) observations of the [OIII] emission from a z~2 ultraluminous
infrared galaxy (L_IR>10^12 solar luminosities) with an optically identified
Active Galactic Nucleus (AGN). The spatial extent (~4-8 kpc) of the high
velocity and broad [OIII] emission are consistent with that found in z>2 radio
galaxies, indicating the presence of a large-scale energetic outflow in a
galaxy population potentially orders of magnitude more common than distant
radio galaxies. The low radio luminosity of this system indicates that
radio-bright jets are unlikely to be responsible for driving the outflow.
However, the estimated energy input required to produce the large-scale outflow
signatures (of order ~10^59 ergs over ~30 Myrs) could be delivered by a wind
radiatively driven by the AGN and/or supernovae winds from intense star
formation. The energy injection required to drive the outflow is comparable to
the estimated binding energy of the galaxy spheroid, suggesting that it can
have a significant impact on the evolution of the galaxy. We argue that the
outflow observed in this system is likely to be comparatively typical of the
high-redshift ULIRG population and discuss the implications of these
observations for galaxy formation models. |
Variability and the X-ray/UV ratio of Active Galactic Nuclei: The observed relation between the X-ray radiation from AGNs, originating in
the corona, and the optical/UV radiation from the disk is usually described by
the anticorrelation between the UV to X-ray slope alpha_ox and the UV
luminosity. Many factors can affect this relation, including: enhanced X-ray
emission associated with the jets of radio-loud AGNs; X-ray absorption
associated with the UV Broad Absorption Line (BAL) outflows; other X-ray
absorption not associated with BALs; intrinsic X-ray weakness; UV and X-ray
variability, and non-simultaneity of UV and X-ray observations. The separation
of these effects provides information about the intrinsic alpha_ox-L_UV
relation and its dispersion, constraining models of disk-corona coupling. We
extract simultaneous data from the second XMM-Newton serendipitous source
catalogue and the XMM-Newton Optical Monitor Serendipitous UV Source Survey
Catalog, and derive the single-epoch alpha_ox indices. We use ensemble
structure functions to analyse multi-epoch data. We confirm the anticorrelation
of alpha_ox with L_UV, and do not find any evidence of a dependence of alpha_ox
on z. The dispersion in our simultaneous data (0.12) is not significantly
smaller than in previous non-simultaneous studies, suggesting that "artificial
alpha_ox variability" introduced by non-simultaneity is not the main cause of
dispersion. "Intrinsic alpha_ox variability", i.e., the true variability of the
X-ray to optical ratio, is instead important, and accounts for ~30% of the
total variance, or more. "Inter-source dispersion", due to intrinsic
differences in the average alpha_ox values from source to source, is also
important. The dispersion introduced by variability is mostly caused by the
long timescale variations, which are expected to be driven by the optical
variations. | The Sloan Bright Arcs Survey: Four Strongly Lensed Galaxies with
Redshift >2: We report the discovery of four very bright, strongly-lensed galaxies found
via systematic searches for arcs in Sloan Digital Sky Survey Data Release 5 and
6. These were followed-up with spectroscopy and imaging data from the
Astrophysical Research Consortium 3.5m telescope at Apache Point Observatory
and found to have redshift $z>2.0$. With isophotal magnitudes $r = 19.2 - 20.4$
and $3\arcsec$-diameter magnitudes $r = 20.0 - 20.6$, these systems are some of
the brightest and highest surface brightness lensed galaxies known in this
redshift range. In addition to the magnitudes and redshifts, we present
estimates of the Einstein radii, which range from $5.0 \arcsec$ to $12.7
\arcsec$, and use those to derive the enclosed masses of the lensing galaxies. |
Uncertainty and bias of cosmology and astrophysical population model
from statistical dark sirens: Gravitational-wave (GW) radiation from a coalescing compact binary is a
standard siren as the luminosity distance of each event can be directly
measured from the amplitude of the signal. One possibility to constrain
cosmology using the GW siren is to perform statistical inference on a
population of binary black hole (BBH) events. In essence, this statistical
method can be viewed as follows. We can modify the shape of the distribution of
observed BBH events by changing cosmological parameters until it eventually
matches the distribution constructed from an astrophysical population model,
thereby allowing us to determine the cosmological parameters. In this work, we
derive the Cram\'er-Rao bound for both cosmological parameters and those
governing the astrophysical population model from this statistical dark siren
method by examining the Fisher information contained in the event distribution.
Our study provides analytical insights and enables fast yet accurate
estimations of the statistical accuracy of dark siren cosmology. Furthermore,
we consider the bias in cosmology due to unmodeled substructures in the merger
rate and the mass distribution. We find a $1\%$ deviation in the astrophysical
model can lead to a more than $1\%$ error in the Hubble constant. This could
limit the accuracy of dark siren cosmology when there are more than $10^4$ BBH
events detected. | Dynamical Friction and Black Holes in Ultralight Dark Matter Solitons: We numerically simulate the motion of a black hole as it plunges radially
through an ultralight dark matter soliton. We investigate the timescale in
which dynamical friction reduces the kinetic energy of the black hole to a
minimum, and consider the sensitivity of this timescale to changes in the ULDM
particle mass, the total soliton mass, and the mass of the black hole. We
contrast our numerical results with a semi-analytic treatment of dynamical
friction, and find that the latter is poorly suited to this scenario. In
particular, we find that the back-reaction of the soliton to the presence of
the black hole is significant, resulting in oscillations in the coefficient of
dynamical friction which cannot be described in the simple semi-analytical
framework. Furthermore, we observe a late-time reheating effect, in which a
significant amount of kinetic energy is transferred back to the black hole
after an initial damping phase. This complicates the discussion of ULDM
dynamical friction on the scales relevant to the final parsec problem. |
The X-ray Properties of Weak Lensing Selected Galaxy Clusters: We present the results of an X-ray follow-up campaign targeting 10 Weak
Lensing (WL) selected galaxy clusters from a Subaru WL survey. Eight clusters
were studied with dedicated Chandra pointings, whereas archival X-ray data were
used for the remaining two clusters. The WL clusters appear to fit the same
scaling relation between X-ray luminosity and temperature as X-ray selected
clusters. However, when we consider the luminosity-mass relation, the WL
selected clusters appear underluminous by a factor 3.9$\pm$0.9 (or,
alternatively, more massive by 2.9$\pm$0.2), compared to X-ray selected
clusters. Only by considering various observational effects that could
potentially bias WL masses, can this difference be reconciled. We used X-ray
imaging data to quantify the dynamical state of the clusters and found that one
of the clusters appears dynamically relaxed, and two of the clusters host a
cool core, consistent with Sunyaev-Zel'dovich effect selected clusters. Our
results suggest that regular, cool core clusters may be over-represented in
X-ray selected samples. | Measuring neutrino mass and asymmetry with matter pairwise velocities: Neutrinos are believed to be the most abundant fermions in the Universe, but
their masses are unknown, except for being non-zero but much smaller than other
fermions. Cosmological relic neutrinos could also have non-zero chemical
potentials (or asymmetries). Using neutrino-involved N-body simulations, we
investigate the neutrino effects on the matter pairwise velocity, which itself
is an interesting probe of cosmology. We find that for light-halo
($[10^{11},10^{13}]\ M_\odot$) mean pairwise velocity, in the transition range
($[4,15]\ \mathrm{Mpc}$), the effects of neutrino masses overwhelm the effects
of neutrino asymmetries, while in the two-halo-group range ($[25,50]\
\mathrm{Mpc}$), for both light and heavy haloes ($[10^{13},10^{15}]\ M_\odot$),
the effects of neutrino asymmetries dominate, making it possible to disentangle
the two effects. We provide fitting formulae to quantify the effects of
neutrino mass and asymmetry on halo-halo pairwise velocities. |
Energy Feedback from X-ray Binaries in the Early Universe: X-ray photons, because of their long mean-free paths, can easily escape the
galactic environments where they are produced, and interact at long distances
with the inter-galactic medium, potentially having a significant contribution
to the heating and reionization of the early Universe. The two most important
sources of X-ray photons in the Universe are active galactic nuclei (AGN) and
X-ray binaries (XRBs). In this Letter we use results from detailed, large scale
population synthesis simulations to study the energy feedback of XRBs, from the
first galaxies (z~ 20) until today. We estimate that X-ray emission from XRBs
dominates over AGN at z>6-8. The shape of the spectral energy distribution of
the emission from XRBs shows little change with redshift, in contrast to its
normalization which evolves by ~4 orders of magnitude, primarily due to the
evolution of the cosmic star-formation rate. However, the metallicity and the
mean stellar age of a given XRB population affect significantly its X-ray
output. Specifically, the X-ray luminosity from high-mass XRBs per unit of
star-formation rate varies an order of magnitude going from solar metallicity
to less than 10% solar, and the X-ray luminosity from low-mass XRBs per unit of
stellar mass peaks at an age of ~300 Myr and then decreases gradually at later
times, showing little variation for mean stellar ages > 3 Gyr. Finally, we
provide analytical and tabulated prescriptions for the energy output of XRBs,
that can be directly incorporated in cosmological simulations. | A comprehensive parametrization approach for the Hubble parameter in
scalar field dark energy models: This study proposes a novel parametrization approach for the dimensionless
Hubble parameter i.e. $E^2(z)=A(z)+\beta (1+\gamma B(z))$ in the context of
scalar field dark energy models. The parameterization is characterized by two
functions, $A(z)$ and $B(z)$, carefully chosen to capture the behavior of the
Hubble parameter at different redshifts. We explore the evolution of
cosmological parameters, including the deceleration parameter, density
parameter, and equation of state parameter. Observational data from Cosmic
Chronometers (CC), Baryonic Acoustic Oscillations (BAO), and the Pantheon+
datasets are analyzed using MCMC methodology to determine model parameters. The
results are compared with the standard $\Lambda$CDM model using the Planck
observations. Our approach provides a model-independent exploration of dark
energy, contributing to a comprehensive understanding of late-time cosmic
acceleration. |
Comparing photometric results of real and N-body bars: We compare the results of the photometrical analysis of barred galaxies with
those of a similar analysis from N-body simulations. The photometry is for a
sample of nine barred galaxies observed in the J and Ks bands with the CANICA
near infrared (NIR) camera at the 2.1-m telescope of the Observatorio
Astrofisico Guillermo Haro (OAGH) in Cananea, Sonora, Mexico. The comparison
includes radial ellipticity profiles and surface brightness (density for the
N-body galaxies) profiles along the bar major and minor axes. We find very good
agreement, arguing that the exchange of angular momentum within the galaxy
plays a determinant role in the evolution of barred galaxies. | Recognising Axionic Dark Matter by Compton and de-Broglie Scale
Modulation of Pulsar Timing: Light Axionic Dark Matter, motivated by string theory, is increasingly
favored for the "no-WIMP era". Galaxy formation is suppressed below a Jeans
scale, of $\simeq 10^8 M_\odot$ by setting the axion mass to, $m_B \sim
10^{-22}$eV, and the large dark cores of dwarf galaxies are explained as
solitons on the de-Broglie scale. This is persuasive, but detection of the
inherent scalar field oscillation at the Compton frequency, $\omega_B= (2.5{\rm
\, months})^{-1}(m_B/10^{-22}eV)$, would be definitive. By evolving the coupled
Schr\"odinger-Poisson equation for a Bose-Einstein condensate, we predict the
dark matter is fully modulated by de-Broglie interference, with a dense soliton
core of size $\simeq 150pc$, at the Galactic center. The oscillating field
pressure induces General Relativistic time dilation in proportion to the local
dark matter density and pulsars within this dense core have detectably large
timing residuals, of $\simeq 400nsec/(m_B/10^{-22}eV)$. This is encouraging as
many new pulsars should be discovered near the Galactic center with planned
radio surveys. More generally, over the whole Galaxy, differences in dark
matter density between pairs of pulsars imprints a pairwise Galactocentric
signature that can be distinguished from an isotropic gravitational wave
background. |
Clearing the Brush: The Last Stand of Solo Small Field Inflation: By incorporating both the tensor-to-scalar ratio and the measured value of
the spectral index, we set a bound on solo small field inflation of $\Delta
\phi / m_{Pl} \geq 1.00 \sqrt{r/0.1}$. Unlike previous bounds which require
monotonic $\epsilon_V,$ $|\eta_V| <1$, and 60 e-folds of inflation, the bound
remains valid for non-monotonic $\epsilon_V$, $|\eta_V| \gtrsim 1$, and for
inflation which occurs only over the 8 e-folds which have been observed on the
cosmic microwave background. The negative value of the spectral index over the
observed 8 e-folds is what makes the bound strong; we illustrate this by
surveying single field models and finding that for $r \gtrsim 0.1$ and 8
e-folds of inflation, there is no simple potential which reproduces observed
CMB perturbations and remains sub-Planckian. Models that are sub-Planckian
after 8 e-folds must be patched together with a second epoch of inflation that
fills out the remaining $\sim 50$ e-folds. This second, post-CMB epoch is
characterized by extremely small $\epsilon_V$ and therefore an increasing
scalar power spectrum. Using the fact that large power can overabundantly
produce primordial black holes, we bound the maximum energy level of the second
phase of inflation. | Clustering of quasars in the First Year of the SDSS-IV eBOSS survey:
Interpretation and halo occupation distribution: In current and future surveys, quasars play a key role. The new data will
extend our knowledge of the Universe as it will be used to better constrain the
cosmological model at redshift $z>1$ via baryon acoustic oscillation and
redshift space distortion measurements. Here, we present the first clustering
study of quasars observed by the extended Baryon Oscillation Spectroscopic
Survey. We measure the clustering of $\sim 70,000$ quasars located in the
redshift range $0.9<z<2.2$ that cover 1,168 deg$^2$. We model the clustering
and produce high-fidelity quasar mock catalogues based on the BigMultiDark
Planck simulation. Thus, we use a modified (Sub)Halo Abundance Matching model
to account for the specificities of the halo population hosting quasars. We
find that quasars are hosted by halos with masses $\sim10^{12.7}M_\odot$ and
their bias evolves from 1.54 ($z=1.06$) to 3.15 ($z=1.98$). Using the current
eBOSS data, we cannot distinguish between models with different fractions of
satellites. The high-fidelity mock light-cones, including properties of halos
hosting quasars, are made publicly available. |
Deep near-infrared spectroscopy of passively evolving galaxies at z>1.4: [Abridged] We present the results of new near-IR spectroscopic observations
of passive galaxies at z>1.4 in a concentration of BzK-selected galaxies in the
COSMOS field. The observations have been conducted with Subaru/MOIRCS, and have
resulted in absorption lines and/or continuum detection for 18 out of 34
objects. This allows us to measure spectroscopic redshifts for a sample almost
complete to K(AB)=21. COSMOS photometric redshifts are found in fair agreement
overall with the spectroscopic redshifts, with a standard deviation of ~0.05;
however, ~30% of objects have photometric redshifts systematically
underestimated by up to ~25%. We show that these systematic offsets in
photometric redshifts can be removed by using these objects as a training set.
All galaxies fall in four distinct redshift spikes at z=1.43, 1.53, 1.67 and
1.82, with this latter one including 7 galaxies. SED fits to broad-band fluxes
indicate stellar masses in the range of ~4-40x10^10Msun and that star formation
was quenched ~1 Gyr before the cosmic epoch at which they are observed. The
spectra of several individual galaxies have allowed us to measure their
Hdelta_F and Dn4000 indices, which confirms their identification as passive
galaxies, as does a composite spectrum resulting from the coaddition of 17
individual spectra. The effective radii of the galaxies have been measured on
the HST/ACS F814W image, confirming the coexistence at these redshifts of
passive galaxies which are substantially more compact than their local
counterparts with others that follow the local size-stellar mass relation. For
the galaxy with best S/N spectrum we were able to measure a velocity dispersion
of 270+/-105 km/s, indicating that this galaxy lies closely on the virial
relation given its stellar mass and effective radius. | Sources of $H_0$-tensions in dark energy scenarios: By focusing on the simple $w\neq-1$ extension to $\Lambda$CDM, we assess
which epoch(s) possibly source the $H_0$-tension. We consider Cosmic Microwave
Background (CMB) data in three possible ways: $i)$ complete CMB data; $ii)$
excluding the $l<30$ temperature and polarization likelihoods; $iii)$ imposing
early universe priors, that disentangle early and late time physics. Through a
joint analysis with low-redshift supernovae type-Ia and gravitationally lensed
time delay datasets, {and neglecting galaxy clustering Baryonic Acoustic
Oscillation (BAO) data}, we find that the inclusion of early universe CMB
priors is consistent with the local estimate of $H_0$ while excluding the
low-$l$+lowE likelihoods mildly relaxes the tension. This is in contrast to
joint analyses with the complete CMB data. Our simple implementation of
contrasting the effect of different CMB priors on the $H_0$ estimate shows that
the early universe information from the CMB data when decoupled from late-times
physics could be in agreement with a higher value of $H_0$. {We also find no
evidence for the early dark energy model using only the early universe physics
within the CMB data. Finally using the BAO data in different redshift ranges to
perform inverse distance ladder analysis, we find that the early universe
modifications, while being perfectly capable of alleviating the $H_0$-tension
when including the BAO galaxy clustering data, would be at odds with the
Ly-$\alpha$ BAO data due to the difference in $r_{\rm d}\, vs.\, H_0$
correlation between the two BAO datasets.} We therefore infer and speculate
that source for the $H_0$-tension between CMB and local estimates could
possibly originate in the modeling of late-time physics within the CMB
analysis. This in turn recasts the $H_0$-tension as an effect of late-time
physics in CMB, instead of the current early-time CMB vs. local late-time
physics perspective. |
Cosmology in the era of Euclid and the Square Kilometre Array: Theoretical uncertainties on non-linear scales are among the main obstacles
to exploit the sensitivity of forthcoming galaxy and hydrogen surveys like
Euclid or the Square Kilometre Array (SKA). Here, we devise a new method to
model the theoretical error that goes beyond the usual cut-off on small scales.
The advantage of this more efficient implementation of the non-linear
uncertainties is tested through a Markov-Chain-Monte-Carlo (MCMC) forecast of
the sensitivity of Euclid and SKA to the parameters of the standard
$\Lambda$CDM model, including massive neutrinos with total mass $M_\nu$, and to
3 extended scenarios, including 1) additional relativistic degrees of freedom
($\Lambda$CDM + $M_\nu$ + $N_\mathrm{eff}$), 2) a deviation from the
cosmological constant ($\Lambda$CDM + $M_\nu$ + $w_0$), and 3) a time-varying
dark energy equation of state parameter ($\Lambda$CDM + $M_\nu$ +
$\left(w_0,w_a \right)$). We compare the sensitivity of 14 different
combinations of cosmological probes and experimental configurations. For Euclid
combined with Planck, assuming a plain cosmological constant, our method gives
robust predictions for a high sensitivity to the primordial spectral index
$n_{\rm s}$ ($\sigma(n_s)=0.00085$), the Hubble constant $H_0$
($\sigma(H_0)=0.141 \, {\rm km/s/Mpc}$), the total neutrino mass $M_\nu$
($\sigma(M_\nu)=0.020 \, {\rm eV}$). Assuming dynamical dark energy we get
$\sigma(M_\nu)=0.030 \, {\rm eV}$ for the mass and $(\sigma(w_0), \sigma(w_a))
= (0.0214, 0.071)$ for the equation of state parameters. The predicted
sensitivity to $M_\nu$ is mostly stable against the extensions of the
cosmological model considered here. Interestingly, a significant improvement of
the constraints on the extended model parameters is also obtained when
combining Euclid with a low redshift HI intensity mapping survey by SKA1,
demonstrating the importance of the synergy of Euclid and SKA. | The Imperial IRAS-FSC Redshift Catalogue: luminosity functions,
evolution and galaxy bias: We present the luminosity function and selection function of 60 micron
galaxies selected from the Imperial IRAS-FSC Redshift Catalogue (IIFSCz). Three
methods, including the 1/Vmax} and the parametric and non-parametric maximum
likelihood estimator, are used and results agree well with each other. A
density evolution proportional to (1+z)^3.4 or a luminosity evolution exp(1.7
t_L / \tau)$ where t_L is the look-back time is detected in the full sample in
the redshift range [0.02, 0.1], consistent with previous analyses. Of the four
infrared subpopulations, cirrus-type galaxies and M82-type starbursts show
similar evolutionary trends, galaxies with significant AGN contributions show
stronger positive evolution and Arp 220-type starbursts exhibit strong negative
evolution. The dominant subpopulation changes from cirrus-type galaxies to
M82-type starbursts at log (L_60 / L_Sun) ~ 10.3.
In the second half of the paper, we derive the projected two-point spatial
correlation function for galaxies of different infrared template type. The mean
relative bias between cirrus-type galaxies and M82-type starbursts, which
correspond to quiescent galaxies with optically thin interstellar dust and
actively star-forming galaxies respectively, is calculated to be around 1.25.
The relation between current star formation rate (SFR) in star-forming galaxies
and environment is investigated by looking at the the dependence of clustering
on infrared luminosity. We found that M82-type actively star-forming galaxies
show stronger clustering as infrared luminosity / SFR increases. The
correlation between clustering strength and SFR in the local Universe seems to
echo the basic trend seen in star-forming galaxies in the Great Observatories
Origins Deep Survey (GOODS) fields at z ~ 1. |
Cosmological constraints from unWISE and Planck CMB lensing tomography: A number of recent, low-redshift, lensing measurements hint at a universe in
which the amplitude of lensing is lower than that predicted from the
$\Lambda$CDM model fit to the data of the Planck CMB mission. Here we use the
auto- and cross-correlation signal of unWISE galaxies and Planck CMB lensing
maps to infer cosmological parameters at low redshift. In particular, we
consider three unWISE samples (denoted as "blue", "green" and "red") at median
redshifts $z \sim 0.6$, $1.1$ and 1.5, which fully cover the Dark Energy
dominated era. Our cross-correlation measurements, with combined significance
$S/N \sim 80$, are used to infer the amplitude of low-redshift fluctuations,
$\sigma_8$; the fraction of matter in the Universe, $\Omega_m$; and the
combination $S_8 \equiv \sigma_8 (\Omega_m / 0.3)^{0.5}$ to which these
low-redshift lensing measurements are most sensitive. The combination of blue,
green and red samples gives a value $S_8=0.784\pm 0.015$, that is fully
consistent with other low-redshift lensing measurements and in 2.4$\sigma$
tension with the CMB predictions from Planck. This is noteworthy, because CMB
lensing probes the same physics as previous galaxy lensing measurements, but
with very different systematics, thus providing an excellent complement to
previous measurements. | NoSOCS in SDSS. IV. The Role of Environment Beyond the Extent of Galaxy
Clusters: We are able to extend the investigation of the
color-morphology-density-radius relations, for bright and faint galaxies, to $R
\gtrsim 3 \times R_{200}$ and to very low density regions, probing the
transition region between cluster and field galaxies, and finding a smooth
variation between these two populations. We investigate the environmental
variation of galaxy properties (and their relations), such as color, spectral
type and concentration. Our sample comprises 6,415 galaxies that were
previously selected as cluster members from 152 systems with $z \le 0.100$. Our
main findings are: (i) The fraction of discs is generally higher than the ones
for blue and star-forming galaxies, indicating a faster transformation of color
and star-formation compared to structural parameters. (ii) Regarding the
distance to the cluster center we find a small variation in the galaxy
populations outside the virial radius. Once within that radius the fractions of
each population change fast, decreasing even faster within $R \sim 0.3 \times
R_{200}$. (iii) We also find a small increase in the fraction of blue faint
galaxies within $R \sim 0.4 \times R_{200}$, before decreasing again to the
most central bin. (iv) Our results do not indicate a significant dependence on
cluster mass, except for the disc fraction in the core of clusters. (v) The
relations between galaxy properties also point to no dependence on cluster
mass, except for the scatter of the color stellar mass relation. Our results
corroborate a scenario on which pre-processing in groups leads to a strong
evolution in galaxy properties, before they are accreted by large clusters
(abridged). |
Characterizing the Nature of the Unresolved Point Sources in the
Galactic Center: The Galactic Center Excess (GCE) of GeV gamma rays can be explained as a
signal of annihilating dark matter or of emission from unresolved astrophysical
sources, such as millisecond pulsars. Evidence for the latter is provided by a
statistical procedure---referred to as Non-Poissonian Template Fitting
(NPTF)---that distinguishes the smooth distribution of photons expected for
dark matter annihilation from a "clumpy" photon distribution expected for point
sources. In this paper, we perform an extensive study of the NPTF on simulated
data, exploring its ability to recover the flux and luminosity function of
unresolved sources at the Galactic Center. When astrophysical background
emission is perfectly modeled, we find that the NPTF successfully distinguishes
between the dark matter and point source hypotheses when either component makes
up the entirety of the GCE. When the GCE is a mixture of dark matter and point
sources, the NPTF may fail to reconstruct the correct contribution of each
component. We further study the impact of mismodeling the Galactic diffuse
backgrounds, finding that while a dark matter signal could be attributed to
point sources in some outlying cases for the scenarios we consider, the
significance of a true point source signal remains robust. Our work enables us
to comment on a recent study by Leane and Slatyer (2019) that questions prior
NPTF conclusions because the method does not recover an artificial dark matter
signal injected on actual Fermi data. We demonstrate that the failure of the
NPTF to extract an artificial dark matter signal can be natural when point
sources are present in the data---with the effect further exacerbated by the
presence of diffuse mismodeling---and does not on its own invalidate the
conclusions of the NPTF analysis in the Inner Galaxy. | Field-level multiprobe analysis of the CMB, integrated Sachs-Wolfe
effect, and the galaxy density maps: Extracting information from cosmic surveys is often done in a two-step
process, construction of maps and then summary statistics such as two-point
functions. We use simulations to demonstrate the advantages of a general
Bayesian framework that consistently combines different cosmological
experiments on the field level, and reconstructs both the maps and cosmological
parameters. We apply our method to jointly reconstruct the primordial CMB, the
integrated Sachs-Wolfe effect, and six tomographic galaxy density maps on the
full sky on large scales along with several cosmological parameters. While the
traditional maximum a posterior estimator has both two-point level and
field-level bias, the new approach yields unbiased cosmological constraints and
improves the signal-to-noise ratio of the maps. |
Uncovering substructure with wavelets: proof of concept using Abell 2744: A recent comparison of the massive galaxy cluster Abell 2744 with the
Millennium XXL (MXXL) N-body simulation has hinted at a tension between the
observed substructure distribution and the predictions of LambdaCDM. Follow-up
investigations indicated that this could be due to the contribution from the
host halo and the subhalo finding algorithm used. To be independent of any
subhalo finding algorithm, we therefore investigate the particle data of the
MXXL simulation directly. We propose a new method to find substructures in 2D
mass maps using a wavelet transform, which treats the simulation and
observations equally. Using the same criteria to define a subhalo in
observations and simulated data, we find three Abell 2744 analogues in the MXXL
simulation. Thus the observations in Abell 2744 are in agreement with the
predictions of LambdaCDM. We investigate the reasons for the discrepancy
between the results obtained from the SUBFIND and full particle data analyses.
We find that this is due to incompatible substructure definitions in
observations and SUBFIND. | Magnetic Fields in Population III Star Formation: We study the buildup of magnetic fields during the formation of Population
III star-forming regions, by conducting cosmological simulations from realistic
initial conditions and varying the Jeans resolution. To investigate this in
detail, we start simulations from identical initial conditions, mandating 16,
32 and 64 zones per Jeans length, and studied the variation in their magnetic
field amplification. We find that, while compression results in some
amplification, turbulent velocity fluctuations driven by the collapse can
further amplify an initially weak seed field via dynamo action, provided there
is sufficient numerical resolution to capture vortical motions (we find this
requirement to be 64 zones per Jeans length, slightly larger than, but
consistent with previous work run with more idealized collapse scenarios). We
explore saturation of amplification of the magnetic field, which could
potentially become dynamically important in subsequent, fully-resolved
calculations. We have also identified a relatively surprising phenomena that is
purely hydrodynamic: the higher-resolved simulations possess substantially
different characteristics, including higher infall-velocity, increased
temperatures inside 1000 AU, and decreased molecular hydrogen content in the
innermost region. Furthermore, we find that disk formation is suppressed in
higher-resolution calculations, at least at the times that we can follow the
calculation. We discuss the effect this may have on the buildup of disks over
the accretion history of the first clump to form as well as the potential for
gravitational instabilities to develop and induce fragmentation. |
Current data are consistent with flat spatial hypersurfaces in the
$Λ$CDM cosmological model but favor more lensing than the model
predicts: We study the performance of three pairs of tilted $\Lambda$CDM cosmological
models, two pairs allowing for non-flat spatial hypersurfaces with CMB
temperature and polarization power spectrum data (P18) from Planck, P18 lensing
(lensing), and non-CMB data (non-CMB). For the six models, we measure
cosmological parameters and study whether or not pairs of the data sets are
mutually consistent in these models. Half of these models allow the lensing
consistency parameter $A_L$ to be an additional free parameter, while the other
three have $A_L = 1$. The tilted spatially-flat models assume the usual
primordial spatial inhomogeneity power spectrum. The tilted non-flat models
assume either the primordial power spectrum used in the Planck group analyses
[Planck $P(q)$] or a recently computed power spectrum [new $P(q)$]. In the
tilted non-flat models with $A_L=1$ we find differences between P18 data and
non-CMB data cosmological parameter constraints, which are large enough to rule
out the Planck $P(q)$ model at 3$\sigma$ but not the new $P(q)$ model. While
both P18 data and non-CMB data separately favor a closed geometry when
P18+non-CMB data are jointly analyzed the evidence in favor of non-flat
hypersurfaces subsides. Differences between P18 data and non-CMB data
cosmological constraints subside when $A_L$ is allowed to vary. From the most
restrictive P18+lensing+non-CMB data combination we get almost
model-independent constraints and find that the $A_L>1$ option is preferred
over the $\Omega_k<0$ one, with the $A_L$ parameter, for all models, being
larger than unity by $\sim 2.5\sigma$. According to the deviance information
criterion, in the P18+lensing+non-CMB analysis, the varying $A_L$ option is on
the verge of being strongly favored over the $A_L=1$ one, which could indicate
a problem for the standard tilted flat $\Lambda$CDM model (Abridged abstract). | Redshift and redshift-drift in $Λ= 0$ quasi-spherical Szekeres
cosmological models and the effect of averaging: Since the advent of the accelerated expanding homogeneous universe model,
some other explanations for the supernova Ia dimming have been explored, among
which there are inhomogeneous models constructed with exact $\Lambda = 0$
solutions of Einstein's equations. They have been used either as one patch or
to build Swiss-cheese models. The most studied ones have been the
Lema\^itre-Tolman-Bondi (LTB) models. However, these models being spatially
spherical, they are not well designed to reproduce the large scale structures
which exhibit clusters, filaments and non spherical voids. This is the reason
why Szekeres models, which are devoid of any symmetry, have recently come into
play. In this paper, we give the equations and an algorithm to compute the
redshift-drift for the most general quasi-spherical Szekeres (QSS) models with
no dark energy. We apply it to a QSS model recently proposed by Bolejko and
Sussman (BSQSS model) who averaged their model to reproduce the density
distribution of the Alexander and collaborators' LTB model which is able to fit
a large set of cosmological data without dark energy. They concluded that their
model represents a significant improvement over the observed cosmic structure
description by spherical LTB models. We show here that this QSS model is ruled
out by a negative cosmological redshift, i.e. a blueshift, which is not
observed in the Universe. We also compute a positive redshift and the
redshift-drift for the Alexander et al.'s model and compare this redshift-drift
to that of the $\Lambda$CDM model. We conclude that the process of averaging an
unphysical QSS model can lead to obtain a physical model able to reproduce our
observed local Universe with no dark energy need and that the redshift-drift
can discriminate between this model and the $\Lambda$CDM model. For
completeness, we also compute the blueshift-drift of the BSQSS model. |
Galaxy Zoo: Bulgeless Galaxies With Growing Black Holes: The growth of supermassive black holes appears to be driven by galaxy
mergers, violent merger-free processes and/or `secular' processes. In order to
quantify the effects of secular evolution on black hole growth, we study a
sample of active galactic nuclei (AGN) in galaxies with a calm formation
history free of significant mergers, a population that heretofore has been
difficult to locate. Here we present an initial sample of 13 AGN in massive
(M_* >~ 1e10 M_sun) bulgeless galaxies -- which lack the classical bulges
believed inevitably to result from mergers -- selected from the Sloan Digital
Sky Survey using visual classifications from Galaxy Zoo. Parametric
morphological fitting confirms the host galaxies lack classical bulges; any
contributions from pseudobulges are very small (typically < 5%). We compute
black hole masses for the two broad-line objects in the sample (4.2e6 and 1.2e7
M_sun) and place lower limits on black hole masses for the remaining sample
(typically M_BH >~ 1e6 M_sun), showing that significant black hole growth must
be possible in the absence of mergers or violent disk instabilities.
The black hole masses are systematically higher than expected from
established bulge-black hole relations. However, if the mean Eddington ratio of
the systems with measured black hole masses (L/L_Edd = 0.065) is typical, 10 of
13 sources are consistent with the correlation between black hole mass and
total stellar mass. That pure disk galaxies and their central black holes may
be consistent with a relation derived from elliptical and bulge-dominated
galaxies with very different formation histories implies the details of stellar
galaxy evolution and dynamics may not be fundamental to the co-evolution of
galaxies and black holes. | Star Formation Rates for Starburst Galaxies from Ultraviolet, Infrared,
and Radio Luminosities: Star formation rates (SFR) are compared as determined from mid-infrared 7.7
um PAH luminosity [SFR(PAH)], from 1.4 GHz radio luminosity [SFR(radio)], and
from far ultraviolet luminosity [SFR(UV)] for a sample of 287 starburst
galaxies with z < 0.5 having Spitzer IRS observations. The previously adopted
relation log [SFR(PAH)] = log [vLv(7.7 um)] - 42.57+-0.2, for SFR in solar
masses per year and vLv(7.7 um) the luminosity at the peak of the 7.7 um PAH
feature in ergs per s, is found to agree with SFR(radio). Comparing with
SFR(UV) determined independently from ultraviolet observations of the same
sources with the GALEX mission (not corrected for dust extinction), the median
log [SFR(PAH)/SFR(UV)] = 1.67, indicating that only 2% of the ultraviolet
continuum typically escapes extinction by dust within a starburst. The ratio
SFR(PAH)/SFR(UV) depends on infrared luminosity, with form log
[SFR(PAH)/SFR(UV)]= (0.53+-0.05)log Lir - 4.11+-0.18, for Lir in solar
luminosities. We also find that the ratio SFR(PAH)/SFR(UV) is similar to that
in infrared-selected starbursts for a sample of Markarian starburst galaxies
originally selected using optical classification, which implies that there is
no significant selection effect in SFR(PAH)/SFR(UV) using starburst galaxies
discovered by Spitzer. These results indicate that SFRs determined with
ultraviolet luminosities require dust corrections by a factor of ~ 10 for
typical local starbursts but this factor increases to > 700 for the most
luminous starbursts at z ~ 2.5. With this amount of extinction, the optical
magnitude of a starburst having fv(7.7 um) of 1 mJy should be V ~ 25.6. |
Spin-up of low mass classical bulges in barred galaxies: Secular evolution is one of the key routes through which galaxies evolve
along the Hubble sequence. Not only the disk undergoes morphological and
kinematic changes, but also a preexisting classical bulge may be dynamically
changed by the secular processes driven primarily by the bar. We study the
influence of a growing bar on the dynamical evolution of a low mass classical
bulge such as might be present in galaxies like the Milky Way. Using
self-consistent high resolution {\it N}-body simulations, we study how an
initially isotropic non-rotating small classical bulge absorbs angular momentum
emitted by the bar. The basic mechanism of this angular momentum exchange is
through resonances and a considerable fraction of the angular momentum is
channeled through Lagrange point (-1:1) and ILR (2:1) orbits. In the phase of
rapid dynamical growth, also retrograde non-resonant orbits absorb significant
angular momentum. As a result of this angular momentum gain, the initially
non-rotating classical bulge transforms into a fast rotating, radially
anisotropic and triaxial object, embedded in the similarly fast rotating boxy
bulge formed from the disk. Towards the end of the evolution, the classical
bulge develops cylindrical rotation. By that time, its inner regions host a
"classical bulge-bar" whose distinct kinematics could serve as direct
observational evidence for the secular evolution in the galaxy. Some
implications of these results are discussed briefly. | CoMaLit-V. Mass forecasting with proxies. Method and application to weak
lensing calibrated samples: Mass measurements of astronomical objects are most wanted but still elusive.
We need them to trace the formation and evolution of cosmic structure but we
can get direct measurements only for a minority. This lack can be circumvented
with a proxy and a scaling relation. The twofold goal of estimating the
unbiased relation and finding the right proxy value to plug in can be hampered
by systematics, selection effects, Eddington/Malmquist biases and time
evolution. We present a Bayesian hierarchical method which deals with these
issues. Masses to be predicted are treated as missing data in the regression
and are estimated together with the scaling parameters. The calibration
subsample with measured masses does not need to be representative of the full
sample as far as it follows the same scaling relation. We apply the method to
forecast weak lensing calibrated masses of the Planck, redMaPPer and MCXC
clusters. Planck masses are biased low with respect to weak lensing calibrated
masses, with a bias more pronounced for high redshift clusters. MCXC masses are
under-estimated by ~20 per cent, which may be ascribed to hydrostatic bias.
Packages and catalogs are made available with the paper. |
Spatially unassociated galaxies contribute significantly to the blended
submillimetre galaxy population: predictions for follow-up observations of
ALMA sources: There is anecdotal evidence that spatially and physically unassociated
galaxies blended into a single submillimetre (submm) source contribute to the
submm galaxy (SMG) population. This work is the first to theoretically predict
the number counts of such sources. We generate mock SMG catalogues using
lightcones derived from the Bolshoi cosmological simulation; to assign submm
flux densities to the mock galaxies, we use a fitting function previously
derived from the results of dust radiative transfer performed on hydrodynamical
simulations of isolated disc and merging galaxies. We then calculate submm
number counts for different beam sizes and without blending. We predict that >
~50 per cent of blended SMGs have at least one spatially unassociated component
with S_850 > 1 mJy. For a 15-arcsec beam, blends of >2 galaxies in which at
least one component is spatially unassociated dominate the blended sources with
total S_850 > ~3 mJy. The distribution of the redshift separations amongst the
components is strongly bimodal. The typical redshift separation of spatially
unassociated blended sources is ~1. Our predictions for the contributions of
spatially unassociated components and the distribution of redshift separations
are not testable with currently available data, but they will be easily tested
once sufficiently accurate redshifts for the individual subcomponents (resolved
by, e.g., ALMA) of a sufficient number of single-dish-detected blended SMGs are
available. | N-body Simulations for Extended Quintessence Models: We introduce the N-body simulation technique to follow structure formation in
linear and nonlinear regimes for the extended quintessence models
(scalar-tensor theories in which the scalar field has a self-interaction
potential and behaves as dark energy), and apply it to a class of models
specified by an inverse power-law potential and a non-minimal coupling. Our
full solution of the scalar field perturbation confirms that, when the
potential is not too nonlinear, the effects of the scalar field could be
accurately approximated as a modification of background expansion rate plus a
rescaling of the effective gravitational constant relevant for structure
growth. For the models we consider, these have opposite effects, leading to a
weak net effect in the linear perturbation regime. However, on the nonlinear
scales the modified expansion rate dominates and could produce interesting
signatures in the matter power spectrum and mass function, which might be used
to improve the constraints on the models from cosmological data. We show that
the density profiles of the dark matter halos are well described by the
Navarro-Frenk-White formula, although the scalar field could change the
concentration. We also derive an analytic formula for the scalar field
perturbation inside halos assuming NFW density profile and sphericity, which
agrees well with numerical results if the parameter is appropriately tuned. The
results suggest that for the models considered, the spatial variation of the
scalar field (and thus the locally measured gravitational constant) is very
weak, and so local experiments could see the background variation of
gravitational constant. |
The Effect of Large-Scale Structure on the Magnification of
High-Redshift Sources by Cluster-Lenses: Cluster gravitational lensing surveys like the Hubble Space Telescope
Frontier Fields survey will detect distant galaxies 10-50 times fainter than
any yet discovered. Using these surveys to measure the luminosity function of
such faint, distant galaxies, however, requires that magnification maps built
from the constraints of strongly-lensed images be accurate. For models that
assume the cluster and nearby (correlated) structures are the only significant
sources of lensing, a potential source of error in these maps comes from the
fact that light rays also suffer weak deflections by uncorrelated large-scale
structure along the line-of-sight, i.e. cosmic weak lensing (CWL). To
demonstrate the magnitude of this effect, we calculate the magnification change
which results when the same cluster-lens is placed along different lines of
sight. Using a simple density profile for a cluster-lens at z~0.3-0.5 and the
power spectrum of the matter density fluctuations responsible for CWL, we show
that the typical magnifications of ~5(10) of sources at z=6-10 can differ by
~10-20(20-30)% from one line-of-sight to another. However, these fluctuations
rise to greater than order unity near critical curves, indicating that CWL
tends to make its greatest contribution to the most magnified images. We
conclude that the neglect of CWL in determining the intrinsic luminosities of
highly-magnified galaxies may introduce errors significant enough to warrant
further effort to include this contribution in cluster-lens modeling. We
suggest that methods of modeling CWL in galaxy-strong-lensing systems should be
generalized to cluster-lensing systems. | Prospects of discovering sub-solar primordial black holes using the
stochastic gravitational wave background from third-generation detectors: Primordial black holes (PBHs) are dark matter candidates that span broad mass
ranges from $10^{-17}$ $M_\odot$ to $\sim 100$ $M_\odot$. We show that the
stochastic gravitational wave background can be a powerful window for the
detection of sub-solar mass PBHs and shed light on their formation channel via
third-generation gravitational wave detectors such as Cosmic Explorer and the
Einstein Telescope. By using the mass distribution of the compact objects and
the redshift evolution of the merger rates, we can distinguish astrophysical
sources from PBHs and will be able to constrain the fraction of sub-solar mass
PBHs $\leq 1$ $M_\odot$ in the form of dark matter $f_{PBH}\leq 1\%$ at $68\%$
C.L. even for a pessimistic value of a binary suppression factor. In the
absence of any suppression of the merger rate, constraints on $f_{PBH}$ will be
less than $0.001\%$. Furthermore, we will be able to measure the redshift
evolution of the PBH merger rate with about $1\%$ accuracy, making it possible
to uniquely distinguish between the Poisson and clustered PBH scenarios. |
Precise Estimation of Cosmological Parameters Using a More Accurate
Likelihood Function: The estimation of cosmological parameters from a given data set requires a
construction of a likelihood function which, in general, has a complicated
functional form. We adopt a Gaussian copula and constructed a copula likelihood
function for the convergence power spectrum from a weak lensing survey. We show
that the parameter estimation based on the Gaussian likelihood erroneously
introduces a systematic shift in the confidence region, in particular for a
parameter of the dark energy equation of state w. Thus, the copula likelihood
should be used in future cosmological observations. | Searching for cosmological variation of the proton-to-electron mass
ratio using a single $H_2$ system: Exploring physics beyond General Relativity and the Standard Model of
Particle Physics involves investigating spacetime variations in natural
constants. This study employs an $H_2$-single of QSO 0347-383 observational
spectrum to propose a unique approach for detecting potential changes in the
proton-to-electron mass ratio. By comparing the ratio from observational and
laboratory data in the Lyman-Alpha transition line, we derive a cosmological
variation of $\Delta\mu / \mu = (0.120 \pm 0.144) \times 10^{-8}$ at
$z_{abs}=3.025$. This approach not only advances fundamental physics
understanding but also introduces innovative techniques for analyzing
high-redshift QSO systems. |
Squeezing the halo bispectrum: a test of bias models: We study the halo-matter cross bispectrum in the presence of primordial
non-Gaussianity of the local type. We restrict ourselves to the squeezed limit,
for which the calculation are straightforward, and perform the measurements in
the initial conditions of N-body simulations, to mitigate the contamination
induced by nonlinear gravitational evolution. Interestingly, the halo-matter
cross bispectrum is not trivial even in this simple limit as it is strongly
sensitive to the scale-dependence of the quadratic and third-order halo bias.
Therefore, it can be used to test biasing prescriptions. We consider three
different prescription for halo clustering: excursion set peaks (ESP), local
bias and a model in which the halo bias parameters are explicitly derived from
a peak-background split. In all cases, the model parameters are fully
constrained with statistics other than the cross bispectrum. We measure the
cross bispectrum involving one halo fluctuation field and two mass overdensity
fields for various halo masses and collapse redshifts. We find that the ESP is
in reasonably good agreement with the numerical data, while the other
alternatives we consider fail in various cases. This suggests that the
scale-dependence of halo bias also is a crucial ingredient to the squeezed
limit of the halo bispectrum. | A Density Spike on Astrophysical Scales from an N-Field Waterfall
Transition: Hybrid inflation models are especially interesting as they lead to a spike in
the density power spectrum on small scales, compared to the CMB, while also
satisfying current bounds on tensor modes. Here we study hybrid inflation with
$N$ waterfall fields sharing a global $SO(N)$ symmetry. The inclusion of many
waterfall fields has the obvious advantage of avoiding topologically stable
defects for $N>3$. We find that it also has another advantage: it is easier to
engineer models that can simultaneously (i) be compatible with constraints on
the primordial spectral index, which tends to otherwise disfavor hybrid models,
and (ii) produce a spike on astrophysically large length scales. The latter may
have significant consequences, possibly seeding the formation of
astrophysically large black holes. We calculate correlation functions of the
time-delay, a measure of density perturbations, produced by the waterfall
fields, as a convergent power series in both $1/N$ and the field's correlation
function $\Delta(x)$. We show that for large $N$, the two-point function is
$<\delta t({\bf x})\,\delta t({\bf 0})>\,\propto\Delta^2(|{\bf x}|)/N$ and the
three-point function is $<\delta t({\bf x})\,\delta t({\bf y})\,\delta t({\bf
0})>\,\propto\Delta(|{\bf x}-{\bf y}|)\Delta(|{\bf x}|)\Delta(|{\bf y}|)/N^2$.
In accordance with the central limit theorem, the density perturbations on the
scale of the spike are Gaussian for large $N$ and non-Gaussian for small $N$. |
Influence of the hypermagnetic field noise on the baryon asymmetry
generation in the symmetric phase of the early universe: We study a matter turbulence caused by strong random hypermagnetic fields
(HMFs ) that influence the baryon asymmetry evolution due to the Abelian
anomalies in the symmetric phase in the early Universe. Such a matter
turbulence is stipulated by the presence of the advection term in the induction
equation for which a fluid velocity is dominated by the Lorentz force in the
Navier-Stokes equation. For random HMFs, having nonzero mean squared strengths,
we calculate the spectra for the HMF energy and the HMF helicity densities. The
latter function governs the evolution of the fermion asymmetries in the
symmetric phase before the electroweak phase transition (EWPT). In the simplest
model based on the first SM generation for the lepton asymmetries of
$e_\mathrm{R,L}$ and $\nu_{e_\mathrm{L}}$, we calculate a decline of all
fermion asymmetries including the baryon asymmetry, given by the `t Hooft
conservation law, when one accounts for a turbulence of HMFs during the
universe cooling down to EWPT. We obtain that the stronger the mean squared
strength of random initial HMFs is, the deeper the fermion asymmetries
decrease, compared to the case in the absence of any turbulence. | Probing Modified Gravity Theories with ISW and CMB Lensing: We use the optimised skew-spectrum as well as the skew-spectra associated
with the Minkowski Functionals (MFs) to test the possibility of using the
cross-correlation of the Integrated Sachs-Wolfe effect (ISW) and lensing of the
cosmic microwave background (CMB) radiation to detect deviations in the theory
of gravity away from General Relativity (GR). We find that the although both
statistics can put constraints on modified gravity, the optimised skew-spectra
are especially sensitive to the parameter $\rm B_0$ that denotes the the {\em
Compton wavelength} of the scalaron at the present epoch. We investigate three
modified gravity theories, namely: the Post-Parametrised Friedmanian (PPF)
formalism; the Hu-Sawicki (HS) model; and the Bertschinger-Zukin (BZ)
formalism. Employing a likelihood analysis for an experimental setup similar to
ESA's Planck mission, we find that, assuming GR to be the correct model, we
expect the constraints from the first two skew-spectra, $S_{\ell}^{(0)}$ and
$S_{\ell}^{(1)}$, to be the same: $\rm B_0<0.45$ at $95%$ confidence level
(CL), and $\rm B_0<0.67$ at $99%$ CL in the BZ model. The third skew-spectrum
does not give any meaningful constraint. We find that the optimal skew-spectrum
provides much more powerful constraint, giving $\rm B_0<0.071$ at $95%$ CL and
$\rm B_0<0.15$ at $99%$ CL, which is essentially identical to what can be
achieved using the full bispectrum. |
HI absorption from the epoch of reionization and primordial magnetic
fields: We study the impact of primordial magnetic fields on the HI absorption from
the Epoch of Reionization. The presence of these fields result in two distinct
effects: (a) the heating of the haloes from the decay of magnetic fields owing
to ambipolar diffusion, and (b) an increase in the number of haloes owing to
additional matter fluctuations induced by magnetic fields. We analyse both
these effects and show that the latter is potentially observable because the
number of haloes along of line of sight can increase by many orders of
magnitude. While this effect is not strongly dependent on the magnetic field
strength in the range $0.3\hbox{--}0.6$ nG, it is extremely sensitive to the
magnetic field power spectral index for the near scale-free models. Therefore
the detection of such absorption features could be a sensitive probe of the
primordial magnetic field and its power spectrum. We discuss the detectability
of these features with the ongoing and future radio interferometers. In
particular, we show that LOFAR might be able to detect these absorption
features at $z \simeq 10$ in less than 10 hrs of integration if the flux of the
background source is 400 mJy. | Recoiling Black Holes in Merging Galaxies: Relationship to AGN Lifetimes
and Merger Remnant Properties: Central supermassive black holes (SMBHs) are a ubiquitous feature of
locally-observed galaxies, and ample evidence suggests that the growth of SMBHs
and their host galaxies is closely linked. However, in the event of a merger,
gravitational-wave (GW) recoil may displace a SMBH from its galactic center, or
eject it entirely. To explore the consequences of this phenomenon, we use
hydrodynamic simulations of gaseous galaxy mergers that include a range of BH
recoil velocities. We have generated a suite of over 200 simulations with more
than 60 merger models, enabling us to identify systematic trends in the
behavior of recoiling BHs -- specifically (i) their dynamics, (ii) their
observable signatures, and (iii) their effects on BH/galaxy co-evolution. (i)
Recoiling BH trajectories depend heavily on the gas content of the host galaxy;
maximal BH displacements from the center may vary by up to an order of
magnitude between gas-rich and gas-poor mergers. In some cases, recoil
trajectories also depend on the timing of the BH merger relative to the
formation of the galaxy merger remnant. (ii) Recoiling BHs may be observable as
offset active galactic nuclei (AGN) via either kinematic offsets (v > 800 km
s^-1) or spatial offsets (R > 1 kpc) for lifetimes of about 1 - 100 Myr. In
addition, recoil events affect the total AGN lifetime. GW recoil generally
reduces the lifetimes of bright AGN, but may extend lower-luminosity AGN
lifetimes. (iii) Rapidly-recoiling BHs may be up to about 5 times less massive
than their stationary counterparts. These mass deficits lower the normalization
of the M - sigma relation and contribute to both intrinsic and overall scatter.
Furthermore, recoil events displace AGN feedback from the galactic center,
which enhances central star formation rates. This results in longer starburst
phases and higher central stellar densities in merger remnants. |
BeyondPlanck XIII. Intensity foreground sampling, degeneracies, and
priors: We present the intensity foreground algorithms and model employed within the
BeyondPlanck analysis framework. The BeyondPlanck analysis is aimed at
integrating component separation and instrumental parameter sampling within a
global framework, leading to complete end-to-end error propagation in the
$Planck$ Low Frequency Instrument (LFI) data analysis. Given the scope of the
BeyondPlanck analysis, a limited set of data is included in the component
separation process, leading to foreground parameter degeneracies. In order to
properly constrain the Galactic foreground parameters, we improve upon the
previous $\texttt{Commander}$ component separation implementation by adding a
suite of algorithmic techniques. These algorithms are designed to improve the
stability and computational efficiency for weakly constrained posterior
distributions. These are: 1) joint foreground spectral parameter and amplitude
sampling, building on ideas from Miramare; 2) component-based monopole
determination; 3) joint spectral parameter and monopole sampling; and 4)
application of informative spatial priors for component amplitude maps. We find
that the only spectral parameter with a significant signal-to-noise ratio using
the current BeyondPlanck data set is the peak frequency of the anomalous
microwave emission component, for which we find $\nu_{\mathrm{p}}=25.3\pm0.5$
GHz; all others must be constrained through external priors. Future works will
be aimed at integrating many more data sets into this analysis, both map and
time-ordered based, thereby gradually eliminating the currently observed
degeneracies in a controlled manner with respect to both instrumental
systematic effects and astrophysical degeneracies. When this happens, the
simple LFI-oriented data model employed in the current work will need to be
generalized to account for both a richer astrophysical model and additional
instrumental effects. | Constraining the lensing of binary black holes from their stochastic
background: Gravitational waves (GWs) are subject to gravitational lensing in the same
way as electromagnetic radiation. However, to date, no unequivocal observation
of a lensed GW transient has been reported. Independently, GW observatories
continue to search for the stochastic GW signal which is produced by many
transient events at high redshift. We exploit a surprising connection between
the lensing of individual transients and limits to the background radiation
produced by the unresolved population of binary back hole mergers: we show that
it constrains the fraction of individually resolvable lensed binary black holes
to less than $\sim 4\times 10^{-5}$ at present sensitivity. We clarify the
interpretation of existing, low redshift GW observations (obtained assuming no
lensing) in terms of their apparent lensed redshifts and masses and explore
constraints from GW observatories at future sensitivity. Based on our results,
recent claims of observations of lensed events are statistically disfavoured. |
Spin characterisation of systematics in CMB surveys -- a comprehensive
formalism: The CMB $B$-mode polarisation signal -- both the primordial gravitational
wave signature and the signal sourced by lensing -- is subject to many
contaminants from systematic effects. Of particular concern are systematics
that result in mixing of signals of different ``spin'', particularly leakage
from the much larger spin-0 intensity signal to the spin-2 polarisation signal.
We present a general formalism, which can be applied to arbitrary focal plane
setups, that characterises signals in terms of their spin. We provide general
expressions to describe how spin-coupled signals observed by the detectors
manifest at map-level, in the harmonic domain, and in the power spectra,
focusing on the polarisation spectra -- the signals of interest for upcoming
CMB surveys. We demonstrate the presence of a previously unidentified
cross-term between the systematic and the intrinsic sky signal in the power
spectrum, which in some cases can be the dominant source of contamination. The
formalism is not restricted to intensity to polarisation leakage but provides a
complete elucidation of all leakage including polarisation mixing, and applies
to both full and partial (masked) sky surveys, thus covering space-based,
balloon-borne, and ground-based experiments. Using a pair-differenced setup, we
demonstrate the formalism by using it to completely characterise the effects of
differential gain and pointing systematics, incorporating both intensity
leakage and polarisation mixing. We validate our results with full time ordered
data simulations. Finally, we show in an Appendix that an extension of simple
binning map-making to include additional spin information is capable of
removing spin-coupled systematics during the map-making process. | A 43-GHz Survey in the ELAIS N2 Area: We describe a survey in the ELAIS N2 region with the VLA at 43.4 GHz, carried
out with 1627 independent snapshot observations in D-configuration and covering
about 0.5 square degrees. One certain source is detected, a
previously-catalogued flat-spectrum QSO at z=2.2. A few (<5) other sources may
be present at about the 3sigma level, as determined from positions of
source-like deflections coinciding with blue stellar objects, or with sources
from lower-frequency surveys. Independently we show how all the source-like
detections identified in the data can be used with a maximum-likelihood
technique to constrain the 43-GHz source counts at a level of ~7 mJy. Previous
estimates of the counts at 43 GHz, based on lower-frequency counts and spectral
measurements, are consistent with these constraints, although the present
results are suggestive of somewhat higher surface densities at the 7 mJy level.
They do not provide direct evidence of intrusion of a previously unknown source
population, although the several candidate sources need examination before such
a population can be ruled out. |
Highlights and Conclusions of the Chalonge Meudon Workshop Dark Matter
in the Universe: The CIAS Chalonge Workshop `Dark Matter in the Universe and Universal
Properties of Galaxies: Theory and Observations', was held at the Meudon
Ch^ateau of Observatoire de Paris on 8-11 June 2010. The Workshop approached DM
in a fourfold way: astronomical observations of DM structures (galaxy
properties, halos, rotation curves and density profiles), DM numerical
simulations (with and without baryons), theoretical astrophysics and cosmology
(kinetic theory, Boltzmann-Vlasov evolution), astroparticle physics. Peter
Biermann, Alfonso Cavaliere, Hector J. de Vega, Gianfranco Gentile, Chandra
Jog, Andrea Lapi, Paolo Salucci, Norma G. Sanchez, Pasquale Serpico, Rainer
Stiele, Janine van Eymeren and Markus Weber present here their highlights of
the Workshop. The summary and conclusions by H. J. de Vega and N. G. Sanchez
stress among other points the growing evidence that DM particles have a mass in
the keV scale and that those keV scale particles naturally produce the small
scale structures observed in galaxies. Wimps (DM particles heavier than 1 GeV)
are strongly disfavoured combining theory with galaxy astronomical
observations. Peter Biermann presents his live minutes of the Workshop and
concludes that a right-handed sterile neutrino of mass of a few keV is the most
interesting DM candidate. Photos of the Workshop are included. | A lightcone catalogue from the Millennium-XXL simulation: improved
spatial interpolation and colour distributions for the DESI BGS: The use of realistic mock galaxy catalogues is essential in the preparation
of large galaxy surveys, in order to test and validate theoretical models and
to assess systematics. We present an updated version of the mock catalogue
constructed from the Millennium-XXL simulation, which uses a halo occupation
distribution (HOD) method to assign galaxies r-band magnitudes and g-r colours.
We have made several modifications to the mock to improve the agreement with
measurements from the SDSS and GAMA surveys. We find that cubic interpolation,
which was used to build the original halo lightcone, produces extreme
velocities between snapshots. Using linear interpolation improves the
correlation function quadrupole measurements on small scales. We also update
the g-r colour distributions so that the observed colours better agree with
measurements from GAMA data, particularly for faint galaxies. As an example of
the science that can be done with the mock, we investigate how the luminosity
function depends on environment and colour, and find good agreement with
measurements from the GAMA survey. This full-sky mock catalogue is designed for
the ongoing Dark Energy Spectroscopic Instrument (DESI) Bright Galaxy Survey
(BGS), and is complete to a magnitude limit r=20.2. |
The influence of magnetic fields on the thermodynamics of primordial
star formation: We explore the effects of magnetic energy dissipation on the formation of the
first stars. For this purpose, we follow the evolution of primordial chemistry
in the presence of magnetic fields in the post-recombination universe until the
formation of the first virialized halos. From the point of virialization, we
follow the protostellar collapse up to densities of $\sim10^{12}$ cm$^{-3}$ in
a one-zone model. In the intergalactic medium (IGM), comoving field strengths
of $\gtrsim0.1$ nG lead to Jeans masses of $10^8 M_\odot$ or more and thus
delay gravitational collapse in the first halos until they are sufficiently
massive. During protostellar collapse, we find that the temperature minimum at
densities of $\sim10^3$ cm$^{-3}$ does not change significantly, such that the
characteristic mass scale for fragmentation is not affected. However, we find a
significant temperature increase at higher densities for comoving field
strengths of $\gtrsim0.1$ nG. This may delay gravitational collapse, in
particular at densities of $\sim10^9$ cm$^{-3}$, where the proton abundance
drops rapidly and the main contribution to the ambipolar diffusion resistivity
is due to collisions with Li$^+$. After the formation of the protostar, the
increased gas temperatures may enhance the protostellar accretion rate. Our
model confirms that initial weak magnetic fields may be amplified considerably
during gravitational collapse and become dynamically relevant. For instance, a
comoving field strength above $10^{-5}$ nG will be amplified above the critical
value for the onset of jets which can magnetize the IGM. | Galaxy clusters and the cosmic cycle of baryons across cosmic times: We discuss the central role played by the X-ray study of hot baryons within
galaxy clusters to reconstruct the assembly of cosmic structures and to trace
the past history of star formation and accretion onto supermassive Black Holes
(BHs). We shortly review the progress in this field contributed by the current
generation of X-ray telescopes. Then, we focus on the outstanding scientific
questions that have been opened by observations carried out in the last years
and that represent the legacy of Chandra and XMM: (a) When and how is entropy
injected into the inter-galactic medium (IGM)? (b) What is the history of metal
enrichment of the IGM? (c) What physical mechanisms determine the presence of
cool cores in galaxy clusters? (d) How is the appearance of proto-clusters at
z~2 related to the peak of star formation activity and BH accretion? We show
that a highly efficient observational strategy to address these questions is to
carry out a large-area X-ray survey, reaching a sensitivity comparable to that
of deep Chandra and XMM pointings, but extending over several thousands of
square degrees. A similar survey can only be carried out with a Wide-Field
X-ray Telescope (WFXT), which combines a high survey speed with a sharp PSF
across the entire FoV. We emphasize the important synergies that WFXT will have
with a number of future ground-based and space telescopes, covering from the
radio to the X-ray bands. Finally, we discuss the immense legacy value that
such a mission will have for extragalactic astronomy at large. |
A dynamics-based density profile for dark haloes. I. Algorithm and basic
results: The density profiles of dark matter haloes can potentially probe dynamics,
fundamental physics, and cosmology, but some of the most promising signals
reside near or beyond the virial radius. While these scales have recently
become observable, the profiles at large radii are still poorly understood
theoretically, chiefly because the distribution of orbiting matter (the
one-halo term) is partially concealed by particles falling into halos for the
first time. We present an algorithm to dynamically disentangle the orbiting and
infalling contributions by counting the pericentric passages of billions of
simulation particles. We analyse dynamically split profiles out to 10 R200m
across a wide range of halo mass, redshift, and cosmology. We show that the
orbiting term experiences a sharp truncation at the edge of the orbit
distribution. Its sharpness and position are mostly determined by the mass
accretion rate, confirming that the entire profile shape primarily depends on
halo dynamics and secondarily on mass, redshift, and cosmology. The infalling
term also depends on the accretion rate for fast-accreting haloes but is mostly
set by the environment for slowly accreting haloes, leading to a diverse array
of shapes that does not conform to simple theoretical models. While the
resulting scatter in the infalling term reaches 1 dex, the scatter in the
orbiting term is only between 0.1 and 0.4 dex and almost independent of radius.
We demonstrate a tight correspondence between the redshift evolution in LCDM
and the slope of the matter power spectrum. Our code and data are publicly
available. | Generation of gravitational waves from symmetry restoration during
inflation: We discuss the possibility of a feature in the spectrum of inflationary
gravitational waves sourced by a scalar field $\chi$ whose vacuum fluctuations
are amplified by a rapidly time dependent mass. Unlike previous work which has
focused on the case in which the mass of the field $\chi$ vanishes only for an
instant before becoming massive again, we study a system where the scalar field
becomes and remains massless through the end of inflation as the consequence of
the restoration of a shift symmetry. After applying appropriate constraints to
our parameters, we find, for future CMB experiments, a small contribution to
the tensor-to-scalar ratio which can be at most of the order $r \sim 10^{-5}$.
At smaller scales probed by gravitational interferometers, on the other hand,
the energy density in the gravitational waves produced this way might be above
the projected sensitivity of LISA, $\Omega_{GW}\,h^2 \sim 10^{-13}$, in a
narrow region of parameter space. If there is more than one $\chi$ species,
then these amplitudes are enhanced by a factor equal to the number of those
species. |
Forecasting ground-based sensitivity to the Rayleigh scattering of the
CMB in the presence of astrophysical foregrounds: The Rayleigh scattering of cosmic microwave background (CMB) photons off the
neutral hydrogen produced during recombination effectively creates an
additional scattering surface after recombination that encodes new cosmological
information, including the expansion and ionization history of the universe. A
first detection of Rayleigh scattering is a tantalizing target for
next-generation CMB experiments. We have developed a Rayleigh scattering
forecasting pipeline that includes instrumental effects, atmospheric noise, and
astrophysical foregrounds (e.g., Galactic dust, cosmic infrared background, or
CIB, and the thermal Sunyaev-Zel'dovich effect). We forecast the Rayleigh
scattering detection significance for several upcoming ground-based
experiments, including SPT-3G+, Simons Observatory, CCAT-prime, and CMB-S4, and
examine the limitations from atmospheric and astrophysical foregrounds as well
as potential mitigation strategies. When combined with Planck data, we estimate
that the ground-based experiments will detect Rayleigh scattering with a
significance between 1.6 and 3.7, primarily limited by atmospheric noise and
the CIB. | M-flation and its spectators: M-flation is an implementation of assisted inflation, in which the inflaton
fields are three N_c x N_c non-abelian hermitean matrices. The model can be
consistently truncated to an effectively single field inflation model, with all
``spectator'' fields fixed at the origin. We show that starting with random
initial conditions for all fields the truncated sector is not a late-time
attractor, but instead the system evolves towards quadratic assisted inflation
with all fields mass degenerate. Demanding the energy density during inflation
to be below the effective quantum gravity scale, we find that the number of
fields, and thus the assisted effect, is bounded N_c < 10^2. |
Forecasts of cosmological constraints from HI intensity mapping with
FAST, BINGO & SKA-I: We forecast the cosmological constraints of the neutral hydrogen (HI)
intensity mapping (IM) technique with radio telescopes by assuming 1-year of
observational time. The current and future radio telescopes we consider here
are FAST (Five hundred meter Aperture Spherical Telescope), BINGO (Baryon
acoustic oscillations In Neutral Gas Observations), and SKA-I (Square Kilometre
Array phase I) single-dish experiment. We also forecast the combined
constraints of the three radio telescopes with Planck. We find that, the $1
\sigma$ errors of $(w_{0}, w_{a})$ for BINGO, FAST and SKA-I with respect to
the fiducial values are respectively, $(0.9293, 3.5792), (0.4083, 1.5878),
(0.3158, 0.4622)$. This is equivalent to $(56.04\%, 55.64\%)$ and $(66.02\%,
87.09\%)$ improvements in constraining $(w_{0}, w_{a})$ for FAST and SKA-I
relative to BINGO. Simulations further show that SKA-I will put more stringent
constraints than both FAST and BINGO when each of the experiment is combined
with Planck measurement. For the $9$ cosmological parameters in consideration,
we find that, there is a trade-off between SKA-I and FAST in constraining
cosmological parameters, with each experiment being more superior in
constraining a particular set of parameters. | The density distributions of cosmic structures: impact of the local
environment on weak-lensing convergence: Whilst the underlying assumption of the Friedman-Lema\^itre-Robertson-Walker
(FLRW) cosmological model is that matter is homogeneously distributed
throughout the universe, gravitational influences over the life of the universe
have resulted in mass clustered on a range of scales. Hence we expect that, in
our inhomogeneous universe, the view of an observer will be influenced by the
location and local environment. Here we analyse the one-point probability
distribution functions and angular power spectra of weak-lensing (WL)
convergence and magnification numerically to investigate the influence of our
local environment on WL statistics in relativistic $N$-body simulations. To
achieve this, we numerically solve the null geodesic equations which describe
the propagation of light bundles backwards in time from today, and develop a
ray-tracing algorithm, and from these calculate various WL properties. Our
findings demonstrate how cosmological observations of large-scale structure
through WL can be impacted by the locality of the observer. We also calculate
the constraints on the cosmological parameters as a function of redshift from
the theoretical and numerical study of the angular power spectrum of WL
convergence. This study concludes the minimal redshift for the constraint on
the parameter $\Omega_m$ ($H_0$) is $z \sim 0.2$ $(z \sim 0.6 )$ beyond which
the local environment's effect is negligible and the data from WL surveys are
more meaningful above that redshift. The outcomes of this study will have
direct consequences for future surveys, where percent-level-precision is
necessary. |
Coaxing Cosmic 21cm Fluctuations from the Polarized Sky using m-mode
Analysis: In this paper we continue to develop the m-mode formalism, a technique for
efficient and optimal analysis of wide-field transit radio telescopes, targeted
at 21 cm cosmology. We extend this formalism to give an accurate treatment of
the polarised sky, fully accounting for the effects of polarisation leakage and
cross-polarisation. We use the geometry of the measured set of visibilities to
project down to pure temperature modes on the sky, serving as a significant
compression, and an effective first filter of polarised contaminants. We use
the m-mode formalism with the Karhunen-Loeve transform to give a highly
efficient method for foreground cleaning, and demonstrate its success in
cleaning realistic polarised skies observed with an instrument suffering from
substantial off axis polarisation leakage. We develop an optimal quadratic
estimator in the m-mode formalism, which can be efficiently calculated using a
Monte-Carlo technique. This is used to assess the implications of foreground
removal for power spectrum constraints where we find that our method can clean
foregrounds well below the foreground wedge, rendering only scales $k_\parallel
< 0.02 h \,\mathrm{Mpc}^{-1}$ inaccessible. As this approach assumes perfect
knowledge of the telescope, we perform a conservative test of how essential
this is by simulating and analysing datasets with deviations about our assumed
telescope. Assuming no other techniques to mitigate bias are applied, we
recover unbiased power spectra when the per-feed beam width to be measured to
0.1%, and amplifier gains to be known to 1% within each minute. Finally, as an
example application, we extend our forecasts to a wideband 400-800 MHz
cosmological observation and consider the implications for probing dark energy,
finding a medium-sized cylinder telescope improves the DETF Figure of Merit by
around 70% over Planck and Stage II experiments alone. | Tight Correlations Between Massive Galaxy Structural Properties and
Dynamics: The Mass Fundamental Plane Was in Place by z~2: The Fundamental Plane (FP) is an empirical relation between the size, surface
brightness, and velocity dispersion of early-type galaxies. This relation has
been studied extensively for early-type galaxies in the local universe to
constrain galaxy formation mechanisms. The evolution of the zeropoint of this
plane has been extended to high redshifts to study the luminosity evolution of
massive galaxies, under the assumption of structural homology. In this work, we
assess this assumption by replacing surface brightness with stellar mass
density and present the evolution of the "mass FP" for massive, quiescent
galaxies since z~2. By accounting for stellar populations, we thereby isolate
and trace structural and dynamical evolution. Despite the observed dramatic
evolution in the sizes and morphologies of massive galaxies since z~3, we find
that quiescent galaxies lie on the mass FP out to z~2. In contrast with ~1.4
dex evolution in the luminosity FP, average residuals from the z~0 mass FP are
less than ~0.15 dex since z~2. Assuming the Hyde & Bernardi (2009) mass FP
slope, we find that this minimal offset scales as (1+z)^{-0.095+/-0.043}. This
result lends credence to previous studies that derived luminosity evolution
from the FP. Therefore, despite their compact sizes and suggestions that
massive galaxies are more disk-like at z~2, the relationship between their
dynamics and structural properties are consistent with local early-type
galaxies. Finally, we find no strong evidence for a tilt of the mass FP
relative to the Virial plane, but emphasize the need for full models including
selection biases to fully investigate this issue. |
Scalar-tensor cosmologies without screening: Scalar-tensor theories are frequently only consistent with fifth force
constraints in the presence of a screening mechanism, namely in order to
suppress an otherwise unacceptably large coupling between the scalar and
ordinary matter. Here we investigate precisely which subsets of Horndeski
theories do not give rise to and/or require such a screening mechanism. We
investigate these subsets in detail, deriving their form and discussing how
they are restricted upon imposing additional bounds from the speed of
gravitational waves, solar system tests and cosmological observables. Finally,
we also identify what subsets of scalar-tensor theories precisely recover the
predictions of standard (linearised) $\Lambda\text{CDM}$ cosmologies in the
quasi-static limit. | Measurements of E-Mode Polarization and Temperature-E-Mode Correlation
in the Cosmic Microwave Background from 100 Square Degrees of SPTpol Data: We present measurements of $E$-mode polarization and temperature-$E$-mode
correlation in the cosmic microwave background (CMB) using data from the first
season of observations with SPTpol, the polarization-sensitive receiver
currently installed on the South Pole Telescope (SPT). The observations used in
this work cover 100~\sqdeg\ of sky with arcminute resolution at $150\,$GHz. We
report the $E$-mode angular auto-power spectrum ($EE$) and the
temperature-$E$-mode angular cross-power spectrum ($TE$) over the multipole
range $500 < \ell \leq5000$. These power spectra improve on previous
measurements in the high-$\ell$ (small-scale) regime. We fit the combination of
the SPTpol power spectra, data from \planck\, and previous SPT measurements
with a six-parameter \LCDM cosmological model. We find that the best-fit
parameters are consistent with previous results. The improvement in high-$\ell$
sensitivity over previous measurements leads to a significant improvement in
the limit on polarized point-source power: after masking sources brighter than
50\,mJy in unpolarized flux at 150\,GHz, we find a 95\% confidence upper limit
on unclustered point-source power in the $EE$ spectrum of $D_\ell = \ell
(\ell+1) C_\ell / 2 \pi < 0.40 \ \mu{\mbox{K}}^2$ at $\ell=3000$, indicating
that future $EE$ measurements will not be limited by power from unclustered
point sources in the multipole range $\ell < 3600$, and possibly much higher in
$\ell.$ |
A unified empirical model for infrared galaxy counts based on observed
physical evolution of distant galaxies: We reproduce the mid-infrared to radio galaxy counts with a new empirical
model based on our current understanding of the evolution of main-sequence (MS)
and starburst (SB) galaxies. We rely on a simple Spectral Energy Distribution
(SED) library based on Herschel observations: a single SED for the MS and
another one for SB, getting warmer with redshift. Our model is able to
reproduce recent measurements of galaxy counts performed with Herschel,
including counts per redshift slice. This agreement demonstrates the power of
our 2 Star-Formation Modes (2SFM) decomposition for describing the statistical
properties of infrared sources and their evolution with cosmic time. We discuss
the relative contribution of MS and SB galaxies to the number counts at various
wavelengths and flux densities. We also show that MS galaxies are responsible
for a bump in the 1.4 GHz radio counts around 50 {\mu}Jy. Material of the model
(predictions, SED library, mock catalogs...) is available online at
http://irfu.cea.fr/Sap/Phocea/Page/index.php?id=537. | Quantifying the impact of baryon-CDM perturbations on halo clustering
and baryon fraction: Baryons and cold dark matter (CDM) did not comove prior to recombination.
This leads to differences in the local baryon and CDM densities, the so-called
baryon-CDM isocurvature perturbations $\delta_{bc}$. These perturbations are
usually neglected in the analysis of Large-Scale Structure data but taking them
into account might become important in the era of high precision cosmology.
Using gravity-only 2-fluid simulations we assess the impact of such
perturbations on the dark matter halos distribution. In particular, we focus on
the baryon fraction in halos as a function of mass and large-scale
$\delta_{bc}$, which also allows us to study details of the nontrivial
numerical setup required for such simulations. We further measure the
cross-power spectrum between the halo field and $\delta_{bc}$ over a wide range
of mass. This cross-correlation is nonzero and negative which shows that halo
formation is impacted by $\delta_{bc}$. We measure the associated bias
parameter $b_{\delta_{bc}}$ and compare it to recent results, finding good
agreement. Finally we quantify the impact of such perturbations on the
halo-halo power spectrum and show that this effect can be degenerate with the
one of massive neutrinos for surveys like DESI. |
CMB map restoration: Estimating the cosmological microwave background is of utmost importance for
cosmology. However, its estimation from full-sky surveys such as WMAP or more
recently Planck is challenging: CMB maps are generally estimated via the
application of some source separation techniques which never prevent the final
map from being contaminated with noise and foreground residuals. These spurious
contaminations whether noise or foreground residuals are well-known to be a
plague for most cosmologically relevant tests or evaluations; this includes CMB
lensing reconstruction or non-Gaussian signatures search. Noise reduction is
generally performed by applying a simple Wiener filter in spherical harmonics;
however this does not account for the non-stationarity of the noise. Foreground
contamination is usually tackled by masking the most intense residuals detected
in the map, which makes CMB evaluation harder to perform. In this paper, we
introduce a novel noise reduction framework coined LIW-Filtering for Linear
Iterative Wavelet Filtering which is able to account for the noise spatial
variability thanks to a wavelet-based modeling while keeping the highly desired
linearity of the Wiener filter. We further show that the same filtering
technique can effectively perform foreground contamination reduction thus
providing a globally cleaner CMB map. Numerical results on simulated but
realistic Planck data are provided. | A new mechanism for primordial black hole formation during reheating: The Reheating process at the end of inflation is often modeled by an
oscillating scalar field which shows a background dust-like behaviour,
prompting the analysis of gravitational collapse and black hole formation in
this era to be approached by the spherical collapse of standard structure
formation. In the scalar field dark matter structure formation process
virialized halos halt the direct collapse, resulting in halos with condensed
central cores at the de Broglie scale of the dominant scalar field. We show
that a similar process can take place during reheating, leading to the
formation of primordial black holes (PBHs). We study the formation of PBHs
through the gravitational further collapse of structures virialized during
reheating, looking at the collapse of either the whole structure, or that of
the central core within these configurations. We compute the threshold
amplitude for the density contrast to undergo this process, for both free and
self-interacting scalar fields. We discuss the relevance of our results for the
abundance of PBHs at the lower end of the mass spectrum. |
Modeling Biased Tracers at the Field Level: In this paper we test the perturbative halo bias model at the field level.
The advantage of this approach is that any analysis can be done without sample
variance if the same initial conditions are used in simulations and
perturbation theory calculations. We write the bias expansion in terms of
modified bias operators in Eulerian space, designed such that the large bulk
flows are automatically resummed and not treated perturbatively. Using these
operators, the bias model accurately matches the Eulerian density of halos in
N-body simulations. The mean-square model error is close to the Poisson shot
noise for a wide range of halo masses and it is rather scale-independent, with
scale-dependent corrections becoming relevant at the nonlinear scale. In
contrast, for linear bias the mean-square model error can be higher than the
Poisson prediction by factors of up to a few on large scales, and it becomes
scale dependent already in the linear regime. We show that by weighting
simulated halos by their mass, the mean-square error of the model can be
further reduced by up to an order of magnitude, or by a factor of two when
including $60\%$ mass scatter. We also test the Standard Eulerian bias model
using the nonlinear matter field measured from simulations and show that it
leads to a larger and more scale-dependent model error than the bias expansion
based on perturbation theory. These results may be of particular relevance for
cosmological inference methods that use a likelihood of the biased tracer at
the field level, or for initial condition and BAO reconstruction that requires
a precise estimate of the large-scale potential from the biased tracer density. | Cosmological growth and feedback from supermassive black holes: We develop a simple evolutionary scenario for the growth of supermassive
black holes (BHs), assuming growth due to accretion only, to learn about the
evolution of the BH mass function from $z=3$ to 0 and from it calculate the
energy budgets of different modes of feedback. We tune the parameters of the
model by matching the derived X-ray luminosity function (XLF) with the observed
XLF of active galactic nuclei. We then calculate the amount of comoving kinetic
and bolometric feedback as a function of redshift, derive a kinetic luminosity
function and estimate the amount of kinetic feedback and $PdV$ work done by
classical double Fanaroff-Riley II (FR II) radio sources. We also derive the
radio luminosity function for FR IIs from our synthesized population and set
constraints on jet duty cycles. Around 1/6 of the jet power from FR II sources
goes into $PdV$ work done in the expanding lobes during the time the jet is on.
Anti hierarchical growth of BHs is seen in our model due to addition of an
amount of mass being accreted on to all BHs independent of the BH mass. The
contribution to the total kinetic feedback by active galaxies in a low
accretion, kinetically efficient mode is found to be the most significant at
$z<1.5$. FR II feedback is found to be a significant mode of feedback above
redshifts $z\sim 1.5$, which has not been highlighted by previous studies. |
Diffuse light in the young cluster of galaxies CL J1449+0856 at z=2.07: Cluster properties do not seem to be changing significantly during their
mature evolution phase, for example they do not seem to show strong dynamical
evolution at least up to z~0.5, their galaxy red sequence is already in place
at least up to z$\sim$1.2, and their diffuse light content remains stable up to
z~0.8. The question is now to know if cluster properties can evolve more
significantly at redshifts notably higher than 1. We propose here to see how
the properties of the intracluster light (ICL) evolve with redshift by
detecting and analysing the ICL in the X-ray cluster CL J1449+0856 at z=2.07
(discovered by Gobat et al. 2011), based on deep HST NICMOS H band exposures.We
used the same wavelet-based method as that applied to 10 clusters between z=0.4
and 0.8 by Guennou et al. (2012). We detect three diffuse light sources with
respective total magnitudes of H=24.8, 25.5, and 25.9, plus a more compact
object with a magnitude H=25.3. We discuss the significance of our detections
and show that they are robust. The three sources of diffuse light indicate an
elongation along a north-east south-west axis, similar to that of the
distribution of the central galaxies and to the X-ray elongation. This strongly
suggests a history of merging events along this direction. While Guennou et al.
(2012) found a roughly constant amount of diffuse light for clusters between
z~0 and 0.8, we put in evidence at least a 1.5 magnitude increase between z~0.8
and 2. If we assume that the amount of diffuse light is directly linked to the
infall activity on the cluster, this implies that CL J1449+0856 is still
undergoing strong merging events. | An Analytic Model of the Physical Properties of Galaxy Clusters: We introduce an analytic model of the diffuse intergalactic medium in galaxy
clusters based on a polytropic equation of state for the gas in hydrostatic
equilibrium with the cluster gravitational potential. This model is directly
applicable to the analysis of X-ray and Sunyaev-Zeldovich Effect observations
from the cluster core to the virial radius, with 5 global parameters and 3
parameters describing the cluster core. We validate the model using Chandra
X-ray observations of two polytropic clusters, MS 1137.5+6625 and CL
J1226.9+3332, and two cool core clusters, Abell 1835 and Abell 2204. We show
that the model accurately describes the spatially resolved spectroscopic and
imaging data, including the cluster core region where significant cooling of
the plasma is observed. |
The CAMELS project: Cosmology and Astrophysics with MachinE Learning
Simulations: We present the Cosmology and Astrophysics with MachinE Learning Simulations
--CAMELS-- project. CAMELS is a suite of 4,233 cosmological simulations of
$(25~h^{-1}{\rm Mpc})^3$ volume each: 2,184 state-of-the-art
(magneto-)hydrodynamic simulations run with the AREPO and GIZMO codes,
employing the same baryonic subgrid physics as the IllustrisTNG and SIMBA
simulations, and 2,049 N-body simulations. The goal of the CAMELS project is to
provide theory predictions for different observables as a function of cosmology
and astrophysics, and it is the largest suite of cosmological
(magneto-)hydrodynamic simulations designed to train machine learning
algorithms. CAMELS contains thousands of different cosmological and
astrophysical models by way of varying $\Omega_m$, $\sigma_8$, and four
parameters controlling stellar and AGN feedback, following the evolution of
more than 100 billion particles and fluid elements over a combined volume of
$(400~h^{-1}{\rm Mpc})^3$. We describe the simulations in detail and
characterize the large range of conditions represented in terms of the matter
power spectrum, cosmic star formation rate density, galaxy stellar mass
function, halo baryon fractions, and several galaxy scaling relations. We show
that the IllustrisTNG and SIMBA suites produce roughly similar distributions of
galaxy properties over the full parameter space but significantly different
halo baryon fractions and baryonic effects on the matter power spectrum. This
emphasizes the need for marginalizing over baryonic effects to extract the
maximum amount of information from cosmological surveys. We illustrate the
unique potential of CAMELS using several machine learning applications,
including non-linear interpolation, parameter estimation, symbolic regression,
data generation with Generative Adversarial Networks (GANs), dimensionality
reduction, and anomaly detection. | Revisiting the Hubble sequence in the SDSS DR7 spectroscopic sample: a
publicly available bayesian automated classification: We present an automated morphological classification in 4 types
(E,S0,Sab,Scd) of ~700.000 galaxies from the SDSS DR7 spectroscopic sample
based on support vector machines. The main new property of the classification
is that we associate to each galaxy a probability of being in the four
morphological classes instead of assigning a single class. The classification
is therefore better adapted to nature where we expect a continuos transition
between different morphological types. The algorithm is trained with a visual
classification and then compared to several independent visual classifications
including the Galaxy Zoo first release catalog. We find a very good correlation
between the automated classification and classical visual ones. The compiled
catalog is intended for use in different applications and can be downloaded at
http://gepicom04.obspm.fr/sdss_morphology/Morphology_2010.html and soon from
the CasJobs database. |
Environmental dependence of X-ray and optical properties of galaxy
clusters: Galaxy clusters are widely used to constrain cosmological parameters through
their properties, such as masses, luminosity and temperature distributions. One
should take into account all kind of biases that could affect these analyses in
order to obtain reliable constraints. In this work, we study the difference in
the properties of clusters residing in different large scale environments,
defined by their position within or outside of voids, and the density of their
surrounding space. We use both observational and simulation cluster and void
catalogues, i.e. XCS and redMaPPer clusters, BOSS voids, and Magneticum
simulations. We devise two different environmental proxies for the clusters and
study their redshift, richness, mass, X-ray luminosity and temperature
distributions as well as some properties of their galaxy populations. We use
the Kolmogorov-Smirnov two-sample test to discover that richer and more massive
clusters are more prevalent in overdense regions and outside of voids. We also
find that clusters of matched richness and mass in overdense regions and
outside voids tend to have higher X-ray luminosities and temperatures. These
differences could have important implications for precision cosmology with
clusters of galaxies, since cluster mass calibrations can vary with
environment. | (P)reheating Effects of a Constrained Kähler Moduli Inflation Model: In this talk, I discuss the effects, viability, and predictions of the
string-theory-motivated K\"ahler Moduli Inflation I (KMII) potential, coupled
to a light scalar field $\chi$, which can provide a possible source for today's
dark energy density due to the potential's non-vanishing minimum. Although the
model is consistent with the current measured Cosmic Microwave Background (CMB)
data, tighter constraints from future observations are required to test the
viability of the KMII potential with its minimum equivalent to the observed
cosmological constant's energy density $\rho_{\Lambda_{\mathrm{obs}}}$. We
implement a Markov Chain Monte Carlo (MCMC) sampling method to compute the
allowed model parameter ranges and bounds on the inflaton's mass $m_{\phi}$ and
reheating temperature $T_{\mathrm{reh}}$. Additionally, our lattice simulations
predict stochastic gravitational-wave backgrounds generated during the inflaton
oscillations that would be observable today in the $10^{9}$-$10^{11} \,
\mathrm{Hz}$ frequency range. All the results and details will be included in
our upcoming paper with the same title. |
Galaxy groups and clouds in the Local (z~0.01) universe: We present an all-sky catalogue of 395 nearby galaxy groups revealed in the
Local Supercluster and its surroundings. The groups and their associations are
identified among 10914 galaxies at |b|>15deg with radial velocities VLG<3500
km/s. Our group finding algorithm requires the group members to be located
inside their zero-velocity surface. Hereby, we assume that individual galaxy
masses are proportional to their total K-band luminosities, M/L_K=6 Msun/Lsun.
The sample of our groups, where each group has n>=4 members, is characterized
by the following medians: mean projected radius <R>=268 kpc, radial velocity
dispersion sigma_V=74 km/s, K-band luminosity L_K=1.2x10^11 Lsun, virial and
projected masses Mvir=2.4x10^12 and Mp=3.3x10^12 Msun, respectively. Accounting
for measurement error reduces the median masses by 30 per cent. For 97 per cent
of identified groups the crossing time does not exceed the cosmic time, 13.7
Gyr, having the median at 3.8 Gyr.
We examine different properties of the groups, in particular, of the known
nearby groups and clusters in Virgo and Fornax. About a quarter of our groups
can be classified as fossil groups where the dominant galaxy is at least ten
times brighter than the other group members.
In total, our algorithm identifies 54 per cent of galaxies to be members of
groups. Together with triple systems and pairs they gather 82 per cent of the
K-band light in Local universe. We have obtained the local value of matter
density to be Omega_m=0.08+-0.02 within a distance of ~40 Mpc assuming H0=73
km/s/Mpc. It is significantly smaller than the cosmic value, 0.28, in the
standard lambdaCDM model. The discrepancy between the global and local
quantities of Omega_m may be caused by the existence of Dark Matter component
unrelated to the virial masses of galaxy systems. | Promising Observational Methods for Detecting the Epoch of Reionization: It has been several years since the first detection of Gunn-Peterson troughs
in the z > 6 Ly-alpha forest and since the first measurement of the Thomson
scattering optical depth through reionization from the cosmic microwave
background (CMB). Present day CMB measurements provide a significant constraint
on the mean redshift of reionization, and the Ly-alpha forest provides a lower
bound on the redshift at which reionization ended. However, no observation has
provided definitive information on the duration and morphology of this process.
This article is intended as a short review on the most promising observational
methods that aim to detect and study this cosmic phase transition, focusing on
CMB anisotropies, gamma ray burst afterglows, Ly-alpha emitting galaxies, and
redshifted 21cm emission. |
Observational constraints on phantom power-law cosmology: We investigate phantom cosmology in which the scale factor is a power law,
and we use cosmological observations from Cosmic Microwave Background (CMB),
Baryon Acoustic Oscillations (BAO) and observational Hubble data, in order to
impose complete constraints on the model parameters. We find that the power-law
exponent is $\beta\approx-6.51^{+0.24}_{-0.25}$, while the Big Rip is realized
at $t_s\approx104.5^{+1.9}_{-2.0}$ Gyr, in 1$\sigma$ confidence level.
Providing late-time asymptotic expressions, we find that the dark-energy
equation-of-state parameter at the Big Rip remains finite and equal to
$w_{DE}\approx -1.153$, with the dark-energy density and pressure diverging.
Finally, we reconstruct the phantom potential. | GRASIL-3D: an Implemention of Dust Effects in the SEDs of Simulated
Galaxies: We introduce a new model for the spectral energy distribution of galaxies,
GRASIL-3D, which includes a careful modelling of the dust component of the
interstellar medium. GRASIL-3D is an entirely new model based on the formalism
of an existing and widely applied spectrophotometric model, GRASIL, but
specifically designed to be interfaced with galaxies with any arbitrarily given
geometry, such as galaxies calculated by theoretical hydrodynamical galaxy
formation codes. GRASIL-3D is designed to separately treat radiative transfer
in molecular clouds and in the diffuse cirrus component. The code has a general
applicability to the outputs of simulated galaxies, either from Lagrangian or
Eulerian hydrodynamic codes. As an application, the new model has been
interfaced to the P-DEVA and GASOLINE smoothed-particle hydrodynamic codes, and
has been used to calculate the spectral energy distribution for a variety of
simulated galaxies from UV to sub-millimeter wavelengths, whose comparison with
observational data gives encouraging results. In addition, GRASIL-3D allows 2D
images of such galaxies to be obtained, at several angles and in different
bands. |
Steepest growth re-examined: repercussions for primordial black hole
formation: Primordial black holes (PBHs) can be produced by a range of mechanisms in the
early universe. A particular formation channel that connects PBHs with
inflationary phenomenology invokes enhanced primordial curvature perturbations
at small scales. In this paper, we re-examine the impact of the growth of the
primordial power spectrum on PBH formation in terms of its implications for the
PBH mass function. We elaborate on how rapidly the background can transition
between different values of the parameters of the Hubble hierarchy, which must
ultimately derive from a consistent derivative expansion for the background
inflaton field. We discuss artefacts associated with matching calculations, and
highlight the robustness of the $k^4$ steepest growth previously found for
single-field inflation with conservatively smoothed transitions and limits on
how much the amplitude of the power spectrum can grow. We show that the mass
function is relatively insensitive to the steepness of the growth of the power
spectrum and subsequent decay, depending primarily on the peak amplitude and
the presence of any plateaus that last more than an e-fold. The shape of the
power spectrum can of course be constrained by other tracers, and so
understanding the physical limitations on its shape remains a pertinent
question. | Dwarf Galaxy Formation with H2-Regulated Star Formation: II. Gas-Rich
Dark Galaxies at Redshift 2.5: We present a cosmological hydrodynamic simulation of the formation of dwarf
galaxies at redshifts z>~2.5 using a physically-motivated model for
H2-regulated star formation. Our simulation, performed using the Enzo code and
reaching a peak resolution of 109 proper parsecs at z=2.5, extends the results
of Kuhlen et al. (2012) to significantly lower redshifts. We show that a star
formation prescription regulated by the local H2 abundance leads to the
suppression of star formation in dwarf galaxy halos with M_h <~ 10^10 Msun and
to a large population of gas-rich "dark galaxies" at z=2.5 with low star
formation efficiencies and gas depletion timescales >20 Gyr. The fraction of
dark galaxies is 60% at M_h ~ 10^10 Msun and increases rapidly with decreasing
halo mass. Dark galaxies form late and their gaseous disks never reach the
surface densities, > ~5700 Msun / pc^2 (Z/10^-3 Zsun)^(-0.88), that are
required to build a substantial molecular fraction. Despite this large
population of dark galaxies, we show that our H2-regulated simulation is
consistent with both the observed luminosity function of galaxies and the
cosmological mass density of neutral gas at z>~2.5. Moreover, our results
provide a theoretical explanation for the recent detection in fluorescent
Ly-alpha emission of gaseous systems at high redshift with little or no
associated star formation. We further propose that H2-regulation may offer a
fresh solution to a number of outstanding "dwarf galaxy problems" in LambdaCDM.
In particular, H2-regulation leads galaxy formation to become effectively
stochastic on mass scales of M_h ~ 10^10 Msun, and thus these massive dwarfs
are not "too big to fail". |
Hydrodynamical simulations of coupled and uncoupled quintessence models
I: Halo properties and the cosmic web: We present the results of a series of adiabatic hydrodynamical simulations of
several quintessence models (both with a free and an interacting scalar field)
in comparison to a standard \LCDM\ cosmology. For each we use $2\times1024^3$
particles in a $250$\hMpc\ periodic box assuming WMAP7 cosmology. In this work
we focus on the properties of haloes in the cosmic web at $z=0$. The web is
classified into \emph{voids}, \emph{sheets}, \emph{filaments} and \emph{knots}
depending on the eigenvalues of the velocity shear tensor, which are an
excellent proxy for the underlying overdensity distribution. We find that the
properties of objects classified according to their surrounding environment
shows a substantial dependence on the underlying cosmology; for example, while
$V_{\rm max}$ shows average deviations of $\approx5$ per cent across the
different models when considering the full halo sample, comparing objects
classified according to their environment, the size of the deviation can be as
large as $20$ per cent.
We also find that halo spin parameters are positively correlated to the
coupling, whereas halo concentrations show the opposite behaviour. Furthermore,
when studying the concentration-mass relation in different environments, we
find that in all cosmologies underdense regions have a larger normalization and
a shallower slope. While this behaviour is found to characterize all the
models, differences in the best-fit relations are enhanced in (coupled) dark
energy, thus providing a clearer prediction for this class of models. | Accretion-Driven Turbulence as Universal Process: Galaxies, Molecular
Clouds, and Protostellar Disks: Complex turbulent motions are ubiquitously observed in many astrophysical
systems. Their origin, however, is still poorly understood. When cosmic
structures form, they grow in mass via accretion from the surrounding
environment. We propose that this accretion is able to drive internal turbulent
motions in a wide range of astrophysical objects and study this process in the
case of galaxies, molecular clouds and protoplanetary disks. We use a
combination of numerical simulations and analytical arguments to predict the
level of turbulence as a function of the accretion rate, the dissipation scale,
and the density contrast, and compare with observational data. We find that in
Milky Way type galaxies the observed level of turbulence in the interstellar
medium can be explained by accretion, provided that the galaxies gain mass at a
rate comparable to the rate at which they form stars. This process is
particularly relevant in the extended outer disks beyond the star-forming
radius. We also calculate the rate at which molecular clouds grow in mass when
they build up from the atomic component of the galactic gas and find that their
internal turbulence is likely to be driven by accretion as well. It is the very
process of cloud formation that excites turbulent motions on small scales by
establishing the turbulent cascade. In the case of T Tauri disks, we show that
accretion can drive subsonic turbulence at the observed level if the rate at
which gas falls onto the disk is comparable to the rate at which disk material
accretes onto the central star. This also explains the observed relation of
accretion rate and stellar mass, dM/dt ~ M^1.8. The efficiency required to
convert infall motion into turbulence is of the order of a few percent in all
three cases. We conclude that accretion-driven turbulence is a universal
concept with far-reaching implications for a wide range of astrophysical
objects. |
What makes a galaxy radio-loud?: We compare the Spectral Energy Distribution (SED) of radio-loud and
radio-quiet AGNs in three different samples observed with SDSS: radio-loud AGNs
(RLAGNs), Low Luminosity AGNs (LLAGNs) and AGNs in isolated galaxies (IG-AGNs).
All these galaxies have similar optical spectral characteristics. The median
SED of the RLAGNs is consistent with the characteristic SED of quasars, while
that of the LLAGNs and IG-AGNs are consistent with the SED of LINERs, with a
lower luminosity in the IG-AGNs than in the LLAGNs. We infer the masses of the
black holes (BHs) from the bulge masses. These increase from the IG-AGNs to the
LLAGNs and are highest for the RLAGNs. All these AGNs show accretion rates near
or slightly below 10% of the Eddington limit, the differences in luminosity
being solely due to different BH masses. Our results suggests there are two
types of AGNs, radio quiet and radio loud, differing only by the mass of their
bulges or BHs. | The Effective Field Theory of Large-Scale Structure in the presence of
Massive Neutrinos: We develop a formalism to analytically describe the clustering of matter in
the mildly non-linear regime in the presence of massive neutrinos. Neutrinos,
whose free streaming wavenumber ($k_{\rm fs}$) is typically longer than the
non-linear scale ($k_{\rm NL}$) are described by a Boltzmann equation coupled
to the effective fluid-like equations that describe dark matter. We solve the
equations expanding in the neutrino density fraction $(f_\nu)$ and in $k/
k_{\rm NL}$, and add suitable counterterms to renormalize the theory. This
allows us to describe the contribution of short distances to long-distance
observables. Equivalently, we construct an effective Boltzmann equation where
we add additional terms whose coefficients renormalize the contribution from
short-distance physics. We argue that neutrinos with $k_{\rm fs}\gtrsim k_{\rm
NL}$ require an additional counterterm similar to the speed of sound ($c_s$)
for dark matter. We compute the one-loop total-matter power spectrum, and find
that it is roughly equal to $16f_\nu$ times the dark matter one for $k$'s
larger that the typical $k_{\rm fs}$. It is about half of that for smaller
$k$'s. The leading contribution results from the back-reaction of the neutrinos
on the dynamics of the dark matter. The counterterms contribute in a
hierarchical way: the leading ones can either be computed in terms of $c_s$, or
can be accounted for by shifting $c_s$ by an amount proportional to $f_\nu$. |
Cosmological constraints in extended parameter space from the Planck
2018 Legacy release: We present new constraints on extended cosmological scenarios using the
recent data from the Planck 2018 Legacy release. In addition to the six
parameters of the standard LCDM model, we also simultaneously vary the dark
energy equation of state, the neutrino mass, the neutrino effective number, the
running of the spectral index and the lensing amplitude $A_L$. We confirm that
a resolution of the Hubble tension is given by a dark energy equation of state
with w<-1, ruling out quintessence models at high statistical significance.
This solution is, however, not supported by BAO and Pantheon data. We find no
evidence for evolving dark energy, i.e. $w_a \neq 0$. The neutrino effective
number is always in agreement with the expectations of the standard model based
on three active neutrinos. The running of the spectral index also is always
consistent with zero. Despite the increase in the number of parameters, the
$A_L$ lensing anomaly is still present at more than two standard deviations.
The $A_L$ anomaly significantly affects the bounds on the neutrino mass that
can be larger by a factor four with respect to those derived under standard
$\Lambda$CDM. While the lensing data reduces the evidence for $A_L>1$, the
inclusion of BAO and Pantheon increase its statistical significance. | Optical Characteristics of the Astrometric Radio Sources: A new list of physical characteristics of 3914 astrometric radio sources,
including all 717 ICRF-Ext.2 sources, observed during IVS and NRAO VCS sessions
have been compiled. The list includes source type, redshift and visual
magnitude (if available). In case of doubt detailed comment is provided. The
list of sources with their positions was taken from the Goddard VLBI
astrometric catalog with addition of two ICRF-Ext.2 sources. At this stage the
source characteristics were mainly taken from the NASA/IPAC Extragalactic
Database (NED). 667 sources from our list are included into the IERS list.
Comparison has shown a significant difference in characteristics for about half
of these 667 common sources. We compiled a list of frequently observed sources
without known physical characteristics for urgent optical identification and
spectrophotometric observations with large optical telescopes. This presented
list of physical characteristics can be used as a supplement material for the
ICRF-2, as well as a database for kinematic studies of the Universe and other
related works, including scheduling of dedicated IVS programs. |
Cosmology with the Wide-Field Infrared Survey Telescope -- Multi-Probe
Strategies: We simulate the scientific performance of the Wide-Field Infrared Survey
Telescope (WFIRST) High Latitude Survey (HLS) on dark energy and modified
gravity. The 1.6 year HLS Reference survey is currently envisioned to image
2000 deg$^2$ in multiple bands to a depth of $\sim$26.5 in Y, J, H and to cover
the same area with slit-less spectroscopy beyond z=3. The combination of deep,
multi-band photometry and deep spectroscopy will allow scientists to measure
the growth and geometry of the Universe through a variety of cosmological
probes (e.g., weak lensing, galaxy clusters, galaxy clustering, BAO, Type Ia
supernova) and, equally, it will allow an exquisite control of observational
and astrophysical systematic effects. In this paper we explore multi-probe
strategies that can be implemented given WFIRST's instrument capabilities. We
model cosmological probes individually and jointly and account for correlated
systematics and statistical uncertainties due to the higher order moments of
the density field. We explore different levels of observational systematics for
the WFIRST survey (photo-z and shear calibration) and ultimately run a joint
likelihood analysis in N-dim parameter space. We find that the WFIRST reference
survey alone (no external data sets) can achieve a standard dark energy FoM of
>300 when including all probes. This assumes no information from external data
sets and realistic assumptions for systematics. Our study of the HLS reference
survey should be seen as part of a future community driven effort to simulate
and optimize the science return of WFIRST. | Model-independent reconstruction of the primordial curvature power
spectrum from PTA data: Recently released data from pulsar timing array (PTA) collaborations provide
strong evidence for a stochastic signal consistent with a gravitational-wave
background, potentially originating from scalar-induced gravitational waves
(SIGWs). However, in order to determine whether the SIGWs with a specific power
spectrum of curvature perturbations can account for the PTA signal, one needs
to estimate the energy density of the SIGWs, which can be computationally
expensive. In this paper, we use a model-independent approach to reconstruct
the primordial curvature power spectrum using a free spectrum cross over from
$10^{1}\,\mathrm{Mpc}^{-1}$ to $10^{20}\,\mathrm{Mpc}^{-1}$ with NANOGrav
15-yrs data set. Our results can simplify the task of assessing whether a given
primordial curvature power spectrum can adequately explain the observed PTA
signal without calculating the energy density of SIGWs. |
Gravitational Collapse in One Dimension: We simulate the evolution of one-dimensional gravitating collisionless
systems from non- equilibrium initial conditions, similar to the conditions
that lead to the formation of dark- matter halos in three dimensions. As in the
case of 3D halo formation we find that initially cold, nearly homogeneous
particle distributions collapse to approach a final equilibrium state with a
universal density profile. At small radii, this attractor exhibits a power-law
behavior in density, {\rho}(x) \propto |x|^(-{\gamma}_crit), {\gamma}_crit
\simeq 0.47, slightly but significantly shallower than the value {\gamma} = 1/2
suggested previously. This state develops from the initial conditions through a
process of phase mixing and violent relaxation. This process preserves the
energy ranks of particles. By warming the initial conditions, we illustrate a
cross-over from this power-law final state to a final state containing a
homogeneous core. We further show that inhomogeneous but cold power-law initial
conditions, with initial exponent {\gamma}_i > {\gamma}_crit, do not evolve
toward the attractor but reach a final state that retains their original
power-law behavior in the interior of the profile, indicating a bifurcation in
the final state as a function of the initial exponent. Our results rely on a
high-fidelity event-driven simulation technique. | Imprints of dark matter-massive neutrino interaction in upcoming
post-reionization and galaxy surveys: We explore possible signatures of the interaction between dark matter (DM)
and massive neutrinos during the post-reionization epoch. Using both Fisher
matrix forecast analysis and Markov Chain Monte-Carlo (MCMC) simulation, we
conduct a thorough investigation of the constraints and imprints of the
scenario on the upcoming post-reionization and galaxy surveys. Our
investigation focuses on two key parameters: the strength of the DM-massive
neutrino interaction ($u$) and the total neutrino mass ($M_{\rm tot}$), on top
of the usual 6 cosmological parameters. We utilize future 21-cm intensity
mapping, galaxy clustering as well as cosmic shear observations in order to
investigate the possible constraints of these parameters in the future
observations: Square Kilometre Array (SKA1 and SKA2) and Euclid, taking both
conservative and realistic approaches. All these missions show promise in
constraining both the parameters $u$ and $M_{\rm tot}$ by few orders compared
to the current constraints from Planck18 (SKA2 performing the best among them).
Although we do not find much improvement in $H_0$ and $\sigma_8$ tensions from
our forecast analysis, SKA2 constrains them better in conservative approach. We
further perform a brief investigation of the prospects of some of the next
generation Cosmic Microwave Background (CMB) missions in combinations with LSS
experiments in improving the constraints. Our analysis reveals that both SKA2
and CMB-S4 + Euclid + SKA1 IM2 combination will put the strongest bounds on the
model parameters. |
Skewness as a test of dark energy perturbations: We investigate the role played by dark energy perturbations in the skewness
$S_3$ of large-scale matter distribution. We consider a two-fluid universe
composed by matter and dark energy, with perturbations in both components, and
we estimate numerically the skewness of the matter density field as a function
of the dark energy parameters. We characterize today's $S_3$ value for
quintessence and phantom dark energy cosmologies as well as its dependence on
the matter density parameter $\Omega_{m0}$ and the dark energy sound speed
$c^2_s$ with accurate numerical fitting. These fits can be used to test
cosmology against future high quality data on large scale structure. | Numerical simulations challenged on the prediction of massive subhalo
abundance in galaxy clusters: the case of Abell 2142: In this Letter we compare the abundance of member galaxies of a rich, nearby
($z=0.09$) galaxy cluster, Abell 2142, with that of halos of comparable virial
mass extracted from sets of state-of-the-art numerical simulations, both
collisionless at different resolutions and with the inclusion of baryonic
physics in the form of cooling, star formation, and feedback by active galactic
nuclei. We also use two semi-analytical models to account for the presence of
orphan galaxies. The photometric and spectroscopic information, taken from the
Sloan Digital Sky Survey Data Release 12 (SDSS DR12) database, allows us to
estimate the stellar velocity dispersion of member galaxies of Abell 2142. This
quantity is used as proxy for the total mass of secure cluster members and is
properly compared with that of subhalos in simulations. We find that simulated
halos have a statistically significant ($\gtrsim 7$ sigma confidence level)
smaller amount of massive (circular velocity above $200\,{\rm km\, s^{-1}}$)
subhalos, even before accounting for the possible incompleteness of
observations. These results corroborate the findings from a recent strong
lensing study of the Hubble Frontier Fields galaxy cluster MACS J0416
\citep{grillo2015} and suggest that the observed difference is already present
at the level of dark matter (DM) subhalos and is not solved by introducing
baryonic physics. A deeper understanding of this discrepancy between
observations and simulations will provide valuable insights into the impact of
the physical properties of DM particles and the effect of baryons on the
formation and evolution of cosmological structures. |
Directional detection of dark matter streams: Directional detection of WIMPs, in which the energies and directions of the
recoiling nuclei are measured, currently presents the only prospect for probing
the local velocity distribution of Galactic dark matter. We investigate the
extent to which future directional detectors would be capable of probing dark
matter substructure in the form of streams. We analyse the signal expected from
a Sagittarius-like stream and also explore the full parameter space of stream
speed, direction, dispersion and density. Using a combination of non-parametric
directional statistics, a profile likelihood ratio test and Bayesian parameter
inference we find that within acceptable exposure times (O(10) kg yr for cross
sections just below the current exclusion limits) future directional detectors
will be sensitive to a wide range of stream velocities and densities. We also
examine and discuss the importance of the energy window of the detector. | The Aemulus Project IV: Emulating Halo Bias: Models of the spatial distribution of dark matter halos must achieve new
levels of precision and accuracy in order to satisfy the requirements of
upcoming experiments. In this work, we present a halo bias emulator for
modeling the clustering of halos on large scales. It incorporates the
cosmological dependence of the bias beyond the mapping of halo mass to peak
height. The emulator makes substantial improvements in accuracy compared to the
widely used Tinker et al. (2010) model. Halos in this work are defined using an
overdensity criteria of 200 relative to the mean background density. Halo
catalogs are produced for 40 N-body simulations as part of the Aemulus project
at snapshots from z=3 to z=0. The emulator is trained over the mass range
$6\times10^{12}-7\times10^{15}\ h^{-1}M_{\odot}$. Using an additional suite of
35 simulations, we determine that the precision of the emulator is redshift
dependent, achieving sub-percent levels for a majority of the redshift range.
Two additional simulation suites are used to test the ability of the emulator
to extrapolate to higher and lower masses. Our high-resolution simulation suite
is used to develop an extrapolation scheme in which the emulator asymptotes to
the Tinker et al. (2010) model at low mass, achieving ~3% accuracy down to
$10^{11}\ h^{-1}M_{\odot}$. Finally, we present a method to propagate emulator
modeling uncertainty into an error budget. Our emulator is made publicly
available at \url{https://github.com/AemulusProject/bias_emulator}. |
Testing Shear Recovery with Field Distortion: The tilt, rotation, or offset of each CCD with respect to the focal plane, as
well as the distortion of the focal plane itself, cause shape distortions to
the observed objects, an effect typically known as field distortion (FD). We
point out that FD provides a unique way of quantifying the accuracy of cosmic
shear measurement. The idea is to stack the shear estimators from galaxies that
share similar FD-induced shape distortions. Given that the latter can be
calculated with parameters from astrometric calibrations, the accuracy of the
shear estimator can be directly tested on real images. It provides a way to
calibrate the multiplicative and additive shear recovery biases within the
scientific data itself, without requiring simulations or any external data
sets. We use the CFHTLenS images to demonstrate the accuracy of the
Fourier_Quad shear recovery method. We highlight some details in our image
processing pipeline, including background removal, source identification and
deblending, astrometric calibration, star selection for PSF reconstruction,
noise reduction, etc.. We show that in the shear ranges of -0.005 < g_1 < 0.005
and -0.008 < g_2 < 0.008, the multiplicative biases are at the level of < 0.04.
Slight additive biases on the order of 5E-4 (6 sigma) are identified for
sources provided by the official CFHTLenS catalog (not using its shear
catalog), but are minor (4 sigma) for source catalog generated by our
Fourier_Quad pipeline. | A Bayesian Calibration Framework for EDGES: We develop a Bayesian model that jointly constrains receiver calibration,
foregrounds and cosmic 21cm signal for the EDGES global 21\,cm experiment. This
model simultaneously describes calibration data taken in the lab along with
sky-data taken with the EDGES low-band antenna. We apply our model to the same
data (both sky and calibration) used to report evidence for the first star
formation in 2018. We find that receiver calibration does not contribute a
significant uncertainty to the inferred cosmic signal (<1%), though our joint
model is able to more robustly estimate the cosmic signal for foreground models
that are otherwise too inflexible to describe the sky data. We identify the
presence of a significant systematic in the calibration data, which is largely
avoided in our analysis, but must be examined more closely in future work. Our
likelihood provides a foundation for future analyses in which other
instrumental systematics, such as beam corrections and reflection parameters,
may be added in a modular manner. |
BH masses in NLS1: the role of the broad-line region geometry: Narrow Line Seyfert 1 galaxies (NLS1) are generally believed to host
"under-massive" black holes with respect to the predictions from the host
galaxy -- black hole mass scale relations. Black hole masses in NLS1 are
estimated from the continuum luminosity and the width of broad emission lines.
Here we show that the "mass deficit" can be canceled out if we assume that the
broad line region (BLR) in type-1 AGN has a flat geometry, which is seen
face-on in NLS1. The detection of relativistic jets aligned along the line of
sight in a number of NLS1 supports this picture. Moreover, a flat geometry of
the BLR is also suggested by a general trend of the mass deficit as a function
of the line width observed in other type-1 AGN, from quasars to BL Lac objects,
and is consistent with a simple extension of the Unified Model of AGN to the
BLR geometry. | A multi-tracer empirically-driven approach to line-intensity mapping
lightcones: Line-intensity mapping (LIM) is an emerging technique to probe the
large-scale structure of the Universe. By targeting the integrated intensity of
specific spectral lines, it captures the emission from all sources and is
sensitive to the astrophysical processes that drive galaxy evolution. Relating
these processes to the underlying distribution of matter introduces
observational and theoretical challenges, such as observational contamination
and highly non-Gaussian fields, which motivate the use of simulations to better
characterize the signal. In this work we present SkyLine, a computational
framework to generate realistic mock LIM observations that include
observational features and foreground contamination, as well as a variety of
self-consistent tracer catalogs. We apply our framework to generate
realizations of LIM maps from the MultiDark Planck 2 simulations coupled to the
UniverseMachine galaxy formation model. We showcase the potential of our scheme
by exploring the voxel intensity distribution and the power spectrum of
emission lines such as 21 cm, CO, CII, and Lyman-$\alpha$, their mutual
cross-correlations, and cross-correlations with galaxy clustering. We
additionally present cross-correlations between LIM and sub-millimeter
extragalactic tracers of large-scale structure such as the cosmic infrared
background and the thermal Sunyaev-Zel'dovich effect, as well as quantify the
impact of galactic foregrounds, line interlopers and instrument noise on LIM
observations. These simulated products will be crucial in quantifying the true
information content of LIM surveys and their cross-correlations in the coming
decade, and to develop strategies to overcome the impact of contaminants and
maximize the scientific return from LIM experiments. |
Quintessential power-law cosmology: dark energy equation of state: Power-law cosmology with scale factor as power of cosmic time, $a \propto
t^{\a}$, is investigated. We review and discuss value of $\a$ obtained from
various types of observation. Considering dark energy dominant era in late
universe from $z < 0.5$, we use observational derived results from Cosmic
Microwave Background (WMAP7), Baryon Acoustic Oscillations (BAO) and
observational Hubble data to find power exponent $\a$ and other cosmological
variables. $\a$ is found to be $0.99 \pm 0.02$ (WMAP7+BAO+$H_0$) and $0.99 \pm
0.04$ (WMAP7). These values do not exclude possibility of acceleration at
1$\sigma$ hence giving viability to power-law cosmology in general. When
considering scenario of canonical scalar field dark energy with power-law
cosmology, we derive scalar field potential, exact scalar field solution and
equation of state parameter. We found that the scenario of power-law cosmology
containing dynamical canonical scalar field predicts present equation of state
parameter $w_{\phi, 0} = -0.449 \pm 0.030 $ while the $w$CDM with WMAP7 data
(model independent, $w$ constant) allows a maximum (+1$\sigma$) value of
$w_{\phi, 0}$ at -0.70 which is off the prediction range. However, in case of
varying $w_{\phi}$, the $w_{\phi, 0}$ value predicted from quintessential
power-law cosmology is allowed within 1$\sigma$ uncertainty. | Strong lensing systems and galaxy cluster observations as probe to the
cosmic distance duality relation: {In this paper, we use large scale structure observations to test the
redshift dependence of cosmic distance duality relation (CDDR), $D_{\rm
L}(1+z)^{-2}/D_{\rm A}=\eta(z)$}, with $D_{\rm L}$ and $D_{\rm A}$, being the
luminosity and angular diameter distances, respectively. In order to perform
the test, the following data set are considered: strong lensing systems and
galaxy cluster measurements (gas mass fractions). No specific cosmological
model is adopted, only a flat universe is assumed. { By considering two
$\eta(z)$ parametrizations, It is observed that the CDDR remain redshift
independent within $1.5\sigma$ which is in full agreement with other recent
tests involving cosmological data}. It is worth to comment that our results are
independent of the baryon budget of galaxy clusters. |
A Census of the LyC Photons that Form the UV Background During
Reionization: We present a new, on-the-fly photon flux and absorption tracer algorithm
designed to directly measure the contribution of different source populations
to the metagalactic UV background and to the ionisation fraction of gas in the
Universe. We use a suite of multifrequency radiation hydrodynamics simulations
that are carefully calibrated to reproduce a realistic reionization history and
galaxy properties at $z \ge 6$, to disentangle the contribution of photons
emitted by different mass haloes and by stars with different metallicities and
ages to the UV background during reionization. While at very early cosmic times
low mass, metal poor haloes provide most of the LyC photons, their contribution
decreases steadily with time. At $z = 6$ it is the photons emitted by massive
systems (${\rm M_{halo}}/{\rm M_\odot} > 10^{10} \, {\rm h ^{-1}}$) and by the
metal enriched stars ($10^{-3} < Z/Z_{\rm \odot} < 10^{-1.5}$) that provide the
largest contribution to the ionising UV background. We demonstrate that there
are large variations in the escape fraction depending on the source, with the
escape fraction being highest ($\sim 45-60\%$) for photons emitted by the
oldest stars that penetrate into the IGM via low opacity channels carved by the
ionising photons and supernova from younger stars. Before HII regions begin to
overlap, the photoionisation rate strongly fluctuates between different,
isolated HII bubbles, depending on the embedded ionising source, which we
suggest may result in spatial variations in the properties of dwarf galaxies. | Subjecting dark matter candidates to the cluster test: Galaxy clusters, employed by Zwicky to demonstrate the existence of dark
matter, pose new stringent tests. If merging clusters demonstrate that dark
matter is self-interacting with cross section $\sigma/m\sim 2$ cm$^2$/gr,
MACHOs, primordial black holes and light axions that build MACHOs are ruled out
as cluster dark matter. Recent strong lensing and X-ray gas data of the quite
relaxed and quite spherical cluster A1835 allow to test the cases of dark
matter with Maxwell-Boltzmann, Bose-Einstein and Fermi-Dirac distribution, next
to Navarro-Frenck-White profiles. Fits to all these profiles are formally
rejected at over $5\sigma$, except in the fermionic situation. The
interpretation in terms of (nearly) Dirac neutrinos with mass of
$1.61^{+0.19}_{-0.30}$ eV/$c^2$ is consistent with results on the cluster
A1689, with the WMAP, Planck and DES dark matter fractions and with the
nondetection of neutrinoless double $\beta$-decay. The case will be tested in
the 2018 KATRIN experiment. |
Revised $f_{\rm NL}$ parameter in Curvaton Scenario: We revise the Non-Gaussianity of canonical curvaton scenario with a
generalized $\delta N$ formalism, in which it could handle the generic
potentials. In various curvaton models, the energy density is dominant in
different period including the secondary inflation of curvaton, matter
domination and radiation domination. Our method could unify to deal with these
periods since the non-linearity parameter $f_{\rm NL}$ associated with
Non-Gaussianity is a function of equation of state $w$. We firstly investigate
the most simple curvaton scenario, namely the chaotic curvaton with quadratic
potential. Our study shows that most parameter space satisfies with
observational constraints. And our formula will nicely recover the well-known
value of $f_{\rm NL}$ in the absence of non-linear evolution. From the micro
origin of curvaton, we also investigate the Pseudo-Nambu-Goldstone curvaton.
Our result clearly indicates that the second short inflationary process for
Pseudo-Nambu-Goldstone curvaton is ruled out in light of observations. Finally,
our method sheds a new way for investigating the Non-Gaussianity of curvaton
mechanism, espeically for exploring the Non-Gaussianity in MSSM curvaton model. | Regulation of Star Formation Rates in Multiphase Galactic Disks: a
Thermal/Dynamical Equilibrium Model: We develop a model for regulation of galactic star formation rates Sigma_SFR
in disk galaxies, in which ISM heating by stellar UV plays a key role. By
requiring simultaneous thermal and (vertical) dynamical equilibrium in the
diffuse gas, and star formation at a rate proportional to the mass of the
self-gravitating component, we obtain a prediction for Sigma_SFR as a function
of the total gaseous surface density Sigma and the density of stars + dark
matter, rho_sd. The physical basis of this relationship is that thermal
pressure in the diffuse ISM, which is proportional to the UV heating rate and
therefore to Sigma_SFR, must adjust to match the midplane pressure set by the
vertical gravitational field. Our model applies to regions where Sigma < 100
Msun/pc^2. In low-Sigma_SFR (outer-galaxy) regions where diffuse gas dominates,
the theory predicts Sigma_SFR \propto Sigma (rho_sd)^1/2. The decrease of
thermal equilibrium pressure when Sigma_SFR is low implies, consistent with
observations, that star formation can extend (with declining efficiency) to
large radii in galaxies, rather than having a sharp cutoff. The main parameters
entering our model are the ratio of thermal pressure to total pressure in the
diffuse ISM, the fraction of diffuse gas that is in the warm phase, and the
star formation timescale in self-gravitating clouds; all of these are (in
principle) direct observables. At low surface density, our model depends on the
ratio of the mean midplane FUV intensity (or thermal pressure in the diffuse
gas) to the star formation rate, which we set based on Solar neighborhood
values. We compare our results to recent observations, showing good agreement
overall for azimuthally-averaged data in a set of spiral galaxies. For the
large flocculent spiral galaxies NGC 7331 and NGC 5055, the correspondence
between theory and observation is remarkably close. |
Monopole and dipole estimation for multi-frequency sky maps by linear
regression: We describe a simple but efficient method for deriving a consistent set of
monopole and dipole corrections for multi-frequency sky map data sets, allowing
robust parametric component separation with the same data set. The
computational core of this method is linear regression between pairs of
frequency maps, often called "T-T plots". Individual contributions from
monopole and dipole terms are determined by performing the regression locally
in patches on the sky, while the degeneracy between different frequencies is
lifted when ever the dominant foreground component exhibits a significant
spatial spectral index variation. Based on this method, we present two
different, but each internally consistent, sets of monopole and dipole
coefficients for the 9-year WMAP, Planck 2013, SFD 100 um, Haslam 408 MHz and
Reich & Reich 1420 MHz maps. The two sets have been derived with different
analysis assumptions and data selection, and provides an estimate of residual
systematic uncertainties. In general, our values are in good agreement with
previously published results. Among the most notable results are a relative
dipole between the WMAP and Planck experiments of 10-15 uK (depending on
frequency), an estimate of the 408 MHz map monopole of 8.9 +- 1.3 K, and a
non-zero dipole in the 1420 MHz map of $0.15 +- 0.03 K pointing towards
Galactic coordinates (l,b) = (308,-36) +- 14 degrees. These values represent
the sum of any instrumental and data processing offsets, as well as any
Galactic or extra-Galactic component that is spectrally uniform over the full
sky. | Constraining cosmic polarization rotation and implications for
primordial B-modes: Cosmological Birefringence (CB) is a phenomenon, caused by parity violating
modifications to electrodynamics, whereby the linear polarisation angle of
light changes as photons traverse a vacuum. It is possible to use a number of
different analysis techniques to constrain this effect using Cosmic Microwave
Background (CMB) polarisation observations. We investigate two different
methods of constraining direction dependent birefringence for present and
future CMB experiments including BICEP/Keck, Simons Observatory (SO), and
LiteBIRD . Specifically we compare the constraints placed on anisotropic CB
from a quadratic estimator technique to those derived from estimates of the
$B$-mode power-spectrum for the three different experiments. The constraints
derived from estimates of the $B$-mode power spectrum are found to be
comparable to those derived from quadratic estimator for BICEP/Keck and SO, but
not LiteBIRD due to its larger sky coverage. These forecasted upper bounds for
CB are converted to constraints on primordial magnetic fields and the coupling
between photons and pseudo Nambu-Goldstone bosons. Finally we show that even
with the best constraints on CB, for the respective experiments, the
potentially induced $B$-mode power can act as a significant contaminant in the
prospective measurement of primordial $B$-modes. |
Power-Law Template for IR Point Source Clustering: We perform a combined fit to angular power spectra of unresolved infrared
(IR) point sources from the Planck satellite (at 217, 353, 545 and 857 GHz,
over angular scales 100 < l < 2200), the Balloon-borne Large-Aperture
Submillimeter Telescope (BLAST; 250, 350 and 500 um; 1000 < l < 9000), and from
correlating BLAST and Atacama Cosmology Telescope (ACT; 148 and 218 GHz) maps.
We find that the clustered power over the range of angular scales and
frequencies considered is well fit by a simple power law of the form C_l
\propto l^-n with n = 1.25 +/- 0.06. While the IR sources are understood to lie
at a range of redshifts, with a variety of dust properties, we find that the
frequency dependence of the clustering power can be described by the square of
a modified blackbody, nu^beta B(nu,T_eff), with a single emissivity index beta
= 2.20 +/- 0.07 and effective temperature T_eff = 9.7 K. Our predictions for
the clustering amplitude are consistent with existing ACT and South Pole
Telescope results at around 150 and 220 GHz, as is our prediction for the
effective dust spectral index, which we find to be alpha_150-220 = 3.68 +/-
0.07 between 150 and 220 GHz. Our constraints on the clustering shape and
frequency dependence can be used to model the IR clustering as a contaminant in
Cosmic Microwave Background anisotropy measurements. The combined Planck and
BLAST data also rule out a linear bias clustering model. | Probing primordial non-Gaussianity with 21 cm fluctuations from
minihalos: We investigate future constraints on primordial local-type non-Gaussianity
from 21 cm angular power spectrum from minihalos. We particularly focus on the
trispectrum of primordial curvature perturbations which are characterized by
the non-linearity parameters $\tau_{\rm NL}$ and $g_{\rm NL}$. We show that
future measurements of minihalo 21 cm angular power spectrum can probe these
non-linearity parameters with an unprecedented precision of $\tau_{\rm
NL}\sim30$ and $g_{\rm NL}\sim2\times10^3$ for Square Kilometre Array (SKA) and
$\tau_{\rm NL}\sim0.6$ and $g_{\rm NL}\sim8\times10^2$ for Fast Fourier
Transform Telescope (FFTT). These levels of sensitivity would give significant
implications for models of the inflationary Universe and the origin of cosmic
density fluctuations. |
Testing Isotropy in the Local Universe: We test the isotropy of the local distribution of galaxies using the 2MASS
extended source catalogue. By decomposing the full sky survey into distinct
patches and using a combination of photometric and spectroscopic redshift data,
we use both parametric and non-parametric methods to obtain the shape of the
luminosity function in each patch. We use the shape of the luminosity function
to test the statistical isotropy of the underlying galaxy distribution. The
parametric estimator shows some evidence of a hemispherical asymmetry in the
north/south Galactic plane. However the non-parametric estimator exhibits no
significant anisotropy, with the galaxy distribution being consistent with the
assumption of isotropy in all regions considered. The parametric asymmetry is
attributed to the relatively poor fit of the functional form to the underlying
data. When using the non-parametric estimator, we do find a dipole in the shape
of the luminosity function, with maximal deviation from isotropy at galactic
coordinate $(b,l)=(30^{\circ},315^{\circ})$. However we can ascribe no strong
statistical significance to this observation. | Hanny's Voorwerp: a nuclear starburst in IC2497: We present high and intermediate resolution radio observations of the central
region in the spiral galaxy IC 2497, performed using the European VLBI Network
(EVN) at 18 cm, and the Multi-Element Radio Linked Interferometer Network
(MERLIN) at 18 cm and 6 cm. The e-VLBI observations detect two compact radio
sources with brightness temperatures in excess of 105 K, suggesting that they
are associated with an AGN located at the centre of the galaxy. We show that
IC2497 lies on the FIR-radio correlation and that the dominant component of the
18 cm radio flux density of the galaxy is associated with extended emission
confined to sub-kpc scales. IC 2497 therefore appears to be a luminous infrared
galaxy that exhibits a nuclear starburst with a total star formation rate
(assuming a Salpeter IMF) of ~ 70 M*/yr. Typically, vigorous star forming
galaxies like IC2497 always show high levels of extinction towards their
nuclear regions. The new results are in-line with the hypothesis that the
ionisation nebula "Hanny's Voorwerp", located ~15-25 kpc from the galaxy is
part of a massive gas reservoir that is ionised by the radiation cone of an AGN
that is otherwise obscured along the observer's line-of- sight. |
Confirmation of the detection of B-modes in the Planck polarization maps: One of the main problems for extracting the Cosmic Microwave Background (CMB)
from submm/mm observations is to correct for the Galactic components, mainly
synchrotron, free - free and thermal dust emission with the required accuracy.
Through a series of papers, it has been demonstrated that this task can be
fulfilled by means of simple neural networks with high confidence. The main
purpose of this paper is to demonstrate that the CMB BB power spectrum detected
in the Planck 2015 polarization maps is present in the improved Planck 2017
maps with higher signal-to-noise ratio. Two features have been detected in the
EB power spectrum in the new data set, both with S/N $\sim$4 . The origin of
these features is most likely leakage from E to B with a level of about 1 per
cent. This leakage gives no significant contribution to the detected BB power
spectrum. The TB power spectrum is consistent with a zero signal. Altogether,
the BB power spectrum is not consistent with the 'canonical' tensor-to-scalar
models combined with gravitational lensing spectra. These results will give
additional strong arguments for support to the proposed polarization satellite
projects to follow up on the Planck mission . | A Combined View of Sterile-Neutrino Constraints from CMB and Neutrino
Oscillation Measurements: We perform a comparative analysis of constraints on sterile neutrinos from
the Planck experiment and from current and future neutrino oscillation
experiments (MINOS, IceCube, SBN). For the first time, we express the Planck
constraints on $N_{\rm eff}$ and $m_{\rm eff}^{\rm sterile}$ from the Cosmic
Microwave Background in the parameter space used by oscillation experiments
using both mass-squared differences and mixing angles. In a model with a single
sterile neutrino species and using standard assumptions, we find that the
Planck data and the oscillation experiments measuring muon-neutrino
disappearance have similar sensitivity. |
Structural and dynamical modeling of WINGS clusters. III. The pseudo
phase-space density profile: Numerical simulations indicate that cosmological halos display power-law
radial profiles of pseudo phase-space density (PPSD), Q=rho/sigma^3, where rho
is mass density and sigma velocity dispersion. We test these predictions using
the parameters derived from the Markov Chain Monte Carlo (MCMC) analysis
performed with the MAMPOSSt code on the observed kinematics of a velocity
dispersion based stack (sigmav) of 54 nearby regular clusters of galaxies from
the WINGS dataset. In the definition of PPSD, the density is either in total
mass rho (Q_rho) or in galaxy number density nu (Q_nu) of three morphological
classes of galaxies (ellipticals, lenticulars, and spirals), while the velocity
dispersion (obtained by inversion of the Jeans equation) is either the total
(Q_rho and Q_nu) or its radial component (Q_r,rho and Q_r,nu). We find that the
PPSD profiles are power-law relations for nearly all MCMC parameters. The
logarithmic slopes of our observed Q_rho(r) and Q_r,rho(r) for ellipticals and
spirals are in excellent agreement with the predictions for particles in
simulations, but slightly shallower for S0s. For Q_nu(r) and Q_r,nu(r), only
the ellipticals have a PPSD slope matching that of particles in simulations,
while the slope for spirals is much shallower, similar to that of subhalos. But
for cluster stacks based on richness or gas temperature, the fraction of
power-law PPSDs is lower (esp. Q_nu) and the Q_rho slopes are shallower, except
for S0s. The observed PPSD profiles, defined using rho rather than nu, appear
to be a fundamental property of galaxy clusters. They would be imprinted during
an early phase of violent relaxation for dark matter and ellipticals, and later
for spirals as they move towards dynamical equilibrium in the cluster
gravitational potential, while S0s are either intermediate (richness and
temperature-based stacks) or a mixed class (sigmav stack). | Hamiltonian Monte Carlo reconstruction from peculiar velocities: The problem of the reconstruction of the large scale density and velocity
fields from peculiar velocities surveys is addressed here within a Bayesian
framework by means of Hamiltonian Monte Carlo (HMC) sampling. The HAmiltonian
Monte carlo reconstruction of the Local EnvironmenT (Hamlet) algorithm is
designed to reconstruct the linear large scale density and velocity fields in
conjunction with the undoing of lognormal bias in the derived distances and
velocities of peculiar velocities surveys such as the Cosmicflows data. The
Hamlet code has been tested against Cosmicflows mock catalogs consisting of up
to 30 000 data points with mock errors akin to those of the Cosmicflows-3 data,
within the framework of the LCDM standard model of cosmology.
The Hamlet code outperforms previous applications of Gibbs sampling MCMC
reconstruction from the Cosmicflows-3 data by two to four orders of magnitude
in CPU time. The gain in performance is due to the inherent higher efficiency
of the HMC algorithm and due to parallel computing on GPUs rather than CPUs.
This gain will enable an increase in the reconstruction of the large scale
structure from the upcoming Cosmicfows-4 data and the setting of constrained
initial conditions for cosmological high resolution simulations. |
A universal equation to predict $Ω_{\rm m}$ from halo and galaxy
catalogues: We discover analytic equations that can infer the value of $\Omega_{\rm m}$
from the positions and velocity moduli of halo and galaxy catalogues. The
equations are derived by combining a tailored graph neural network (GNN)
architecture with symbolic regression. We first train the GNN on dark matter
halos from Gadget N-body simulations to perform field-level likelihood-free
inference, and show that our model can infer $\Omega_{\rm m}$ with $\sim6\%$
accuracy from halo catalogues of thousands of N-body simulations run with six
different codes: Abacus, CUBEP$^3$M, Gadget, Enzo, PKDGrav3, and Ramses. By
applying symbolic regression to the different parts comprising the GNN, we
derive equations that can predict $\Omega_{\rm m}$ from halo catalogues of
simulations run with all of the above codes with accuracies similar to those of
the GNN. We show that by tuning a single free parameter, our equations can also
infer the value of $\Omega_{\rm m}$ from galaxy catalogues of thousands of
state-of-the-art hydrodynamic simulations of the CAMELS project, each with a
different astrophysics model, run with five distinct codes that employ
different subgrid physics: IllustrisTNG, SIMBA, Astrid, Magneticum,
SWIFT-EAGLE. Furthermore, the equations also perform well when tested on galaxy
catalogues from simulations covering a vast region in parameter space that
samples variations in 5 cosmological and 23 astrophysical parameters. We
speculate that the equations may reflect the existence of a fundamental physics
relation between the phase-space distribution of generic tracers and
$\Omega_{\rm m}$, one that is not affected by galaxy formation physics down to
scales as small as $10~h^{-1}{\rm kpc}$. | Cosmological neutrino entropy changes due to flavor statistical mixing: Entropy changes due to delocalization and decoherence effects should modify
the predictions for the cosmological neutrino background (C$\nu$B) temperature
when one treats neutrino flavors in the framework of composite quantum systems.
Assuming that the final stage of neutrino interactions with the $\gamma
e^{-}e^{+}$ radiation plasma before decoupling works as a measurement scheme
that projects neutrinos into flavor quantum states, the resulting
free-streaming neutrinos can be described as a statistical ensemble of
flavor-mixed neutrinos. Even not corresponding to an electronic-flavor pure
state, after decoupling the statistical ensemble is described by a density
matrix that evolves in time with the full Hamiltonian accounting for flavor
mixing, momentum delocalization and, in case of an open quantum system
approach, decoherence effects. Since the statistical weights, $w$, shall follow
the electron elastic scattering cross section rapport given by $0.16\,w_{e} =
w_{\mu} = w_{\tau}$, the von-Neumann entropy will deserve some special
attention. Depending on the quantum measurement scheme used for quantifying the
entropy, mixing associated to dissipative effects can lead to an increasing of
the flavor associated von-Neumann entropy for free-streaming neutrinos. The
production of von-Neumann entropy mitigates the constraints on the predictions
for energy densities and temperatures of a cosmologically evolving isentropic
fluid, in this case, the cosmological neutrino background. The effects of
entropy changes on the cosmological neutrino temperature are quantified, and
the {\em constraint} involving the number of neutrino species, $N_{\nu} \approx
3$, in the phenomenological confront with Big Bang nucleosynthesis parameters
is consistently relieved. |
Studying the Diversity of Type Ia Supernovae in the Ultraviolet:
Comparing Models with Observations: In the ultraviolet (UV), Type Ia supernovae (SNe Ia) show a much larger
diversity in their properties than in the optical. Using a stationary
Monte-Carlo radiative transfer code, a grid of spectra at maximum light was
created varying bolometric luminosity and the amount of metals in the outer
layers of the SN ejecta. This model grid is then compared to a sample of
high-redshift SNe Ia in order to test whether the observed diversities can be
explained by luminosity and metallicity changes alone. The dispersion in
broadband UV flux and colours at approximately constant optical spectrum can be
readily matched by the model grid. In particular, the UV1-b colour is found to
be a good tracer of metal content of the outer ejecta, which may in turn
reflect on the metallicity of the SN progenitor. The models are less successful
in reproducing other observed trends, such as the wavelengths of key UV
features, which are dominated by reverse fluorescence photons from the optical,
or intermediate band photometric indices. This can be explained in terms of the
greater sensitivity of these detailed observables to modest changes in the
relative abundances. Specifically, no single element is responsible for the
observed trends. Due to their complex origin, these trends do not appear to be
good indicators of either luminosity or metallicity. | A Measurement of the Cosmic Microwave Background Lensing Potential and
Power Spectrum from 500 deg$^2$ of SPTpol Temperature and Polarization Data: We present a measurement of the cosmic microwave background (CMB) lensing
potential using 500 deg$^2$ of 150 GHz data from the SPTpol receiver on the
South Pole Telescope. The lensing potential is reconstructed with
signal-to-noise per mode greater than unity at lensing multipoles $L \lesssim
250$, using a quadratic estimator on a combination of CMB temperature and
polarization maps. We report measurements of the lensing potential power
spectrum in the multipole range of $100< L < 2000$ from sets of
temperature-only, polarization-only, and minimum-variance estimators. We
measure the lensing amplitude by taking the ratio of the measured spectrum to
the expected spectrum from the best-fit $\Lambda$CDM model to the
$\textit{Planck}$ 2015 TT+lowP+lensing dataset. For the minimum-variance
estimator, we find $A_{\rm{MV}} = 0.944 \pm 0.058{\rm (Stat.)}\pm0.025{\rm
(Sys.)}$; restricting to only polarization data, we find $A_{\rm{POL}} = 0.906
\pm 0.090 {\rm (Stat.)} \pm 0.040 {\rm (Sys.)}$. Considering statistical
uncertainties alone, this is the most precise polarization-only lensing
amplitude constraint to date (10.1 $\sigma$), and is more precise than our
temperature-only constraint. We perform null tests and consistency checks and
find no evidence for significant contamination. |
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