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Observation of H2O in a strongly lensed Herschel-ATLAS source at z=2.3: The Herschel survey, H-ATLAS, with its large areal coverage, has recently
discovered a number of bright, strongly lensed high-z submillimeter galaxies.
The strong magnification makes it possible to study molecular species other
than CO, which are otherwise difficult to observe in high-z galaxies. Among the
lensed galaxies already identified by H-ATLAS, the source J090302.9-014127B
(SDP.17b) at z = 2.305 is remarkable due to its excitation conditions and a
tentative detection of the H2O 202-111 emission line (Lupu et al. 2010). We
report observations of this line in SDP.17b using the IRAM interferometer
equipped with its new 277- 371GHz receivers. The H2O line is detected at a
redshift of z = 2.3049+/-0.0006, with a flux of 7.8+/-0.5 Jy km s-1 and a FWHM
of 250+/-60 km s-1. The new flux is 2.4 times weaker than the previous
tentative detection, although both remain marginally consistent within
1.6-sigma. The intrinsic line luminosity and ratio of H2O(202-111)/CO8-7 seem
comparable with those of the nearby starburst/enshrouded-AGN Mrk 231,
suggesting that SDP.17b could also host a luminous AGN. The detection of a
strong H2O 202-111 line in SDP.17b implies an efficient excitation mechanism of
the water levels that must occur in very dense and warm interstellar gas. | Clustering of galaxies around GRB sight-lines: There is evidence of an overdensity of strong intervening MgII absorption
line systems distributed along the lines of sight towards GRB afterglows
relative to quasar sight-lines. If this excess is real, one should also expect
an overdensity of field galaxies around GRB sight-lines, as strong MgII tends
to trace these sources. In this work, we test this expectation by calculating
the two point angular correlation function of galaxies within
120$^{\prime\prime}$ ($\sim470~h_{71}^{-1}~\mathrm{Kpc}$ at $\langle z\rangle
\sim0.4$) of GRB afterglows. We compare the Gamma-ray burst Optical and
Near-infrared Detector (GROND) GRB afterglow sample -- one of the largest and
most homogeneous samples of GRB fields -- with galaxies and AGN found in the
COSMOS-30 photometric catalog. We find no significant signal of anomalous
clustering of galaxies at an estimated median redshift of $z\sim0.3$ around GRB
sight-lines, down to $K_{\mathrm{AB}}<19.3$. This result is contrary to the
expectations from the MgII excess derived from GRB afterglow spectroscopy,
although many confirmed galaxy counterparts to MgII absorbers may be too faint
to detect in our sample -- especially those at $z>1$. We note that the addition
of higher sensitivity Spitzer IRAC or HST WFC3 data for even a subset of our
sample would increase this survey's depth by several orders of magnitude,
simultaneously increasing statistics and enabling the investigation of a much
larger redshift space.} |
Cosmology from Cosmic Shear with DES Science Verification Data: We present the first constraints on cosmology from the Dark Energy Survey
(DES), using weak lensing measurements from the preliminary Science
Verification (SV) data. We use 139 square degrees of SV data, which is less
than 3\% of the full DES survey area. Using cosmic shear 2-point measurements
over three redshift bins we find $\sigma_8 (\Omega_{\rm m}/0.3)^{0.5} = 0.81
\pm 0.06$ (68\% confidence), after marginalising over 7 systematics parameters
and 3 other cosmological parameters. We examine the robustness of our results
to the choice of data vector and systematics assumed, and find them to be
stable. About $20$\% of our error bar comes from marginalising over shear and
photometric redshift calibration uncertainties. The current state-of-the-art
cosmic shear measurements from CFHTLenS are mildly discrepant with the
cosmological constraints from Planck CMB data; our results are consistent with
both datasets. Our uncertainties are $\sim$30\% larger than those from CFHTLenS
when we carry out a comparable analysis of the two datasets, which we attribute
largely to the lower number density of our shear catalogue. We investigate
constraints on dark energy and find that, with this small fraction of the full
survey, the DES SV constraints make negligible impact on the Planck
constraints. The moderate disagreement between the CFHTLenS and Planck values
of $\sigma_8 (\Omega_{\rm m}/0.3)^{0.5}$ is present regardless of the value of
$w$. | A fast test to assess the impact of marginalization in Monte Carlo
analyses, and its application to cosmology: Monte Carlo (MC) algorithms are commonly employed to explore high-dimensional
parameter spaces constrained by data. All the statistical information obtained
in the output of these analyses is contained in the Markov chains, which one
needs to process and interpret. The marginalization technique allows us to
digest these chains and compute the posterior distributions for the parameter
subsets of interest. In particular, it lets us draw confidence regions in
two-dimensional planes, and get the constraints for the individual parameters.
It is very well known, though, that the marginalized results can suffer from
volume effects, which can introduce a non-negligible bias into our conclusions.
The impact of these effects are barely studied in the literature. In this paper
we first illustrate the problem through a very clear and simple example in two
dimensions, and suggest the use of the profile distributions (PDs) as a
complementary tool to detect marginalization biases directly from the MC
chains. We apply our method to four cosmological models: the standard
$\Lambda$CDM, early dark energy, coupled dark energy and the Brans-Dicke model
with a cosmological constant. We discuss the impact of the volume effects on
each model and the cosmological tensions, using the full Planck 2018
likelihood, the Pantheon compilation of supernovae of Type Ia and data on
baryon acoustic oscillations. Our test is very efficient and can be easily
applied to any MC study. It allows us to estimate the PDs at a derisory
computational cost not only for the main cosmological parameters, but also for
the nuisance and derived ones, and to assess the need to perform a more
in-depth analysis with the exact computation of the PDs. |
Central Stellar Mass Deficits in the Bulges of Local Lenticular
Galaxies, and the Connection with Compact z ~ 1.5 Galaxies: We have used the full radial extent of images from the Hubble Space
Telescope's Advanced Camera for Surveys and Wide Field Planetary Camera 2 to
extract surface brightness profiles from a sample of six, local lenticular
galaxy candidates. We have modelled these profiles using a core-Sersic bulge
plus an exponential disk model. Our lenticular disk galaxies with bulge
magnitudes M_V < ~ -21.30 mag have central stellar deficits, suggesting that
these bulges may have formed from `dry' merger events involving supermassive
black holes while their surrounding disk was subsequently built up, perhaps via
cold gas accretion scenarios. The central stellar mass deficits M_def are
roughly 0.5 to 2 M_BH (black hole mass), rather than ~ 10 to 20 M_BH as claimed
from some past studies, which is in accord with core-Sersic model mass deficit
measurements in elliptical galaxies. Furthermore, these bulges have Sersic
indices n ~ 3, half light radii R_e < 2 kpc and masses > 10^11 M_sun, and
therefore appear to be descendants of the compact galaxies reported at z ~ 1.5
to 2. Past studies which have searched for these local counterparts by using
single-component galaxy models to provide the z ~ 0 size comparisons have
over-looked these dense, compact and massive bulges in today's early-type disk
galaxies. This evolutionary scenario not only accounts for what are today
generally old bulges---which must be present in z ~ 1.5 images---residing in
what are generally young disks, but it eliminates the uncomfortable suggestion
of a factor of 3 to 5 growth in size for the compact, z ~ 1.5 galaxies that are
known to possess infant disks. | Improved Cosmological Constraints from SDSS redMaPPer Clusters via X-ray
Follow-up of a Complete Subsample of Systems: We improve upon the cosmological constraints derived from the abundance and
weak-lensing data of redMaPPer clusters detected in the Sloan Digital Sky
Survey (SDSS). Specifically, we derive gas mass data using Chandra X-ray
follow-up of a complete sample of the 30 richest SDSS redMaPPer clusters with
$z\in[0.1,0.3]$, and use these additional data to improve upon the original
analysis by Costanzi et al. (2019b). We simultaneously fit for the parameters
of the richness-mass relation, the cluster gas mass-mass relation, and
cosmology. By including our X-ray cluster sample in the SDSS cluster cosmology
analysis, we measure $\Omega_{\rm m} = 0.25 \pm 0.04$ and $\sigma_8 =
0.85^{+0.06}_{-0.08}$. These constraints represent a 25.5% and 29.8% reduction
in the size of the 68% confidence intervals of $\Omega_{\rm m}$ and $\sigma_8$
respectively, relative to the constraints published in Costanzi et al. (2019b).
Our cosmological constraints are in agreement with early universe results from
Planck. As a byproduct of our analysis, we also perform an independent
calibration of the amplitude of the $\langle M_{\rm gas}^{\rm true}|M_{\rm
500c}\rangle$ scaling relation. Our calibration is consistent with and of
comparable precision to that of Mantz et al. (2016b). |
Large scale gas sloshing out to half the virial radius in the strongest
cool core REXCESS galaxy cluster, RXJ2014.8-2430: We search the cool core galaxy clusters in the REXCESS sample for evidence of
large scale gas sloshing, and find clear evidence for sloshing in
RXJ2014.8-2430, the strongest cool core cluster in the REXCESS cluster sample.
The residuals of the surface brightness distribution from the azimuthal average
for RXJ2014 show a prominent swirling excess feature extending out to an abrupt
surface brightness discontinuity at 800 kpc from the cluster core (half the
virial radius) to the south, which the XMM-Newton observations confirm to be
cold, low entropy gas. The gas temperature is significantly higher outside this
southern surface brightness discontinuity, indicating that this is a cold front
800 kpc from the cluster core. Chandra observations of the central 200 kpc show
two clear younger cold fronts on opposite sides of the cluster. The scenario
appears qualitatively consistent with simulations of gas sloshing due to minor
mergers which raise cold, low entropy gas from the core to higher radius,
resulting in a swirling distribution of opposing cold fronts at increasing
radii. However the scale of the observed sloshing is much larger than that
which has been simulated at present, and is similar to the large scale sloshing
recently observed in the Perseus cluster and Abell 2142. | Probing Reionization and Early Cosmic Enrichment with the MgII Forest: Because the same massive stars that reionized the intergalactic medium (IGM)
inevitably exploded as supernovae that polluted the Universe with metals, the
history of cosmic reionization and enrichment are intimately intertwined. While
the overly sensitive Ly-alpha transition completely saturates in a neutral IGM,
strong low-ionization metal lines like the MgII 2796,2804 doublet will give
rise to a detectable `metal-line forest' if the metals produced during
reionization (Z ~ 10^{-3}Z_sol) permeate the neutral IGM. We simulate the MgII
forest for the first time by combining a large hydrodynamical simulation with a
semi-numerical reionization topology, assuming a simple enrichment model where
the IGM is uniformly suffused with metals. In contrast to the traditional
approach of identifying discrete absorbers, we treat the absorption as a
continuous random field and measure its two-point correlation function,
leveraging techniques from precision cosmology. We show that a realistic mock
dataset of 10 JWST spectra can simultaneously determine the Mg abundance,
[Mg/H], with a 1sigma precision of 0.02 dex and measure the global neutral
fraction <x_HI> to 5% for a Universe with <x_HI> = 0.74 and [Mg/H] = -3.7.
Alternatively, if the IGM is pristine, a null-detection of the MgII forest
would set a stringent upper limit on the IGM metallicity of [Mg/H] < -4.4 at
95% credibility, assuming <x_HI> > 0.5 from another probe. Concentrations of
metals in the circumgalactic environs of galaxies can significantly contaminate
the IGM signal, but we demonstrate how these discrete absorbers can be easily
identified and masked such that their impact on the correlation function is
negligible. The MgII forest thus has tremendous potential to precisely
constrain the reionization and enrichment history of the Universe. |
The First SRG/eROSITA All-Sky Survey: Optical Identification and
Properties of Galaxy Clusters and Groups in the Western Galactic Hemisphere: The first SRG/eROSITA All-Sky Survey (eRASS1) provides the largest
intracluster medium-selected galaxy cluster and group catalog covering the
western galactic hemisphere. Compared to samples selected purely on X-ray
extent, the sample purity can be enhanced by identifying cluster candidates
using optical and near-infrared data from the DESI Legacy Imaging Surveys.
Using the red-sequence-based cluster finder eROMaPPer, we measure individual
photometric properties (redshift $z_\lambda$, richness $\lambda$, optical
center, and BCG position) for 12,000 eRASS1 clusters over a sky area of 13,116
deg$^2$, augmented by 247 cases identified by matching the candidates with
known clusters from the literature. The median redshift of the identified
eRASS1 sample is $z=0.31$, with 10% of the clusters at $z>0.72$. The
photometric redshifts have an accuracy of $\delta z/(1+z)<0.005$ for
$0.05<z<0.9$. Spectroscopic cluster properties (redshift $z_{\rm spec}$ and
velocity dispersion $\sigma$) are measured a posteriori for a subsample of
3,210 and 1,499 eRASS1 clusters, respectively, using an extensive compilation
of spectroscopic redshifts of galaxies from the literature. We infer that the
primary eRASS1 sample has a purity of 86% and optical completeness >95% for
$z>0.05$. For these and further quality assessments of the eRASS1 identified
catalog, we apply our identification method to a collection of galaxy cluster
catalogs in the literature, as well as blindly on the full Legacy Surveys
covering 24,069 deg$^2$. Using a combination of these cluster samples, we
investigate the velocity dispersion-richness relation, finding
$\log(\lambda)=2.401\times\log(\sigma)-5.074$ with an intrinsic scatter of
$0.10\pm0.01$ dex. Our main result is the identified eRASS1 cluster catalog
with a high purity and a well-defined X-ray selection process, enabling precise
cosmological analyses presented in companion papers. | Higher-Order Gravitational Lensing Reconstruction using Feynman Diagrams: We develop a method for calculating the correlation structure of the Cosmic
Microwave Background (CMB) using Feynman diagrams, when the CMB has been
modified by gravitational lensing, Faraday rotation, patchy reionization, or
other distorting effects. This method is used to calculate the bias of the
Hu-Okamoto quadratic estimator in reconstructing the lensing power spectrum up
to O(\phi^4) in the lensing potential $\phi$. We consider both the diagonal
noise TTTT, EBEB, etc. and, for the first time, the off-diagonal noise TTTE,
TBEB, etc. The previously noted large O(\phi^4) term in the second order noise
is identified to come from a particular class of diagrams. It can be
significantly reduced by a reorganization of the $\phi$ expansion. These
improved estimators have almost no bias for the off-diagonal case involving
only one $B$ component of the CMB, such as EEEB. |
Noncanonical Domain Wall as a Unified Model of Dark Energy and Dark
Matter: I. Cosmic Dynamics: We propose noncanonical domain walls as a new dark energy model inspired by
grand unified theories (GUTs). We investigate the cosmic dynamics and discover
that the domain walls act as either dark energy or dark matter at different
times, depending on the velocity v in the observer's comoving frame. We find a
single stable solution to the dynamics, i.e., only freezing (v = 0)
noncanonical domain walls can enter the phantom zone without having to
experience ghost field instability. This means that the solution has an
equation of state (EoS) w_dw < -1 without having to possess negative kinetic
energy. These domain walls give rise to a late-time cosmic acceleration
starting from z = 0.8, resulting in w_dw = -1.5 and w_eff = -1.03 today. We
learn that the EoS of the noncanonical domain walls is independent of the
potential form. We also investigate the perturbation dynamics following the
model. Our simulations show that compared to LCDM, the amplitude of the dark
matter power spectrum in the noncanonical domain wall model is lower, while the
CMB power spectrum is shifted slighly to lower l multipoles. The proposed model
gives a smaller sigma8 compared to that of LCDM. | A new extensive catalog of optically variable AGN in the GOODS Fields
and a new statistical approach to variability selection: Variability is a property shared by practically all AGN. This makes
variability selection a possible technique for identifying AGN. Given that
variability selection makes no prior assumption about spectral properties, it
is a powerful technique for detecting both low-luminosity AGN in which the host
galaxy emission is dominating and AGN with unusual spectral properties. In this
paper, we will discuss and test different statistical methods for the detection
of variability in sparsely sampled data that allow full control over the false
positive rates. We will apply these methods to the GOODS North and South fields
and present a catalog of variable sources in the z band in both GOODS fields.
Out of 11931 objects checked, we find 155 variable sources at a significance
level of 99.9%, corresponding to about 1.3% of all objects. After rejection of
stars and supernovae, 139 variability selected AGN remain. Their magnitudes
reach down as faint as 25.5 mag in z. Spectroscopic redshifts are available for
22 of the variability selected AGN, ranging from 0.046 to 3.7. The absolute
magnitudes in the rest-frame z-band range from ~ -18 to -24, reaching
substantially fainter than the typical luminosities probed by traditional X-ray
and spectroscopic AGN selection in these fields. Therefore, this is a powerful
technique for future exploration of the evolution of the faint end of the AGN
luminosity function up to high redshifts. |
A simple model to interpret the ultraviolet, optical and infrared SEDs
of galaxies: We present a simple, largely empirical but physically motivated model, which
is designed to interpret consistently multi-wavelength observations from large
samples of galaxies in terms of physical parameters, such as star formation
rate, stellar mass and dust content. Our model is both simple and versatile
enough to allow the derivation of statistical constraints on the star formation
histories and dust contents of large samples of galaxies using a wide range of
ultraviolet, optical and infrared observations. We illustrate this by deriving
median-likelihood estimates of a set of physical parameters describing the
stellar and dust contents of local star-forming galaxies from the Spitzer
Infrared Nearby Galaxy Sample (SINGS) and from a newly-matched sample of SDSS
galaxies observed with GALEX, 2MASS, and IRAS. The model reproduces well the
observed spectral energy distributions of these galaxies across the entire
wavelength range from the far-ultraviolet to the far-infrared. We find
important correlations between the physical parameters of galaxies which are
useful to investigate the star formation activity and dust properties of
galaxies. Our model can be straightforwardly applied to interpret observed
ultraviolet-to-infrared spectral energy distributions (SEDs) from any galaxy
sample. | Joint analysis of the thermal Sunyaev-Zeldovich effect and 2MASS
galaxies: Probing gas physics in the local Universe and beyond: We present a first joint analysis of the power spectra of the thermal
Sunyaev-Zeldovich (tSZ) effect measured by the Planck and the number density
fluctuations of galaxies in the 2MASS redshift survey (2MRS) catalog, including
their cross-correlation. Combining these measurements with the cosmic microwave
background (CMB) data and CMB lensing of Planck assuming a flat $\Lambda$CDM
model, we constrain the mass bias parameter as $B = 1.54 \pm 0.098\;(1\sigma)$
[$(1-b) = 0.649 \pm 0.041$, where $(1-b) \equiv B^{-1}$], i.e., the Planck
cluster mass should be $35\%$ lower than the true mass. The mass bias
determined by the 2MRS-tSZ cross-power spectrum alone is consistent with that
determined by the tSZ auto-power spectrum alone, suggesting that this large
mass bias is not due to obvious systematics in the tSZ data. We find that the
2MRS-tSZ cross-power spectrum is more sensitive to less massive halos than the
tSZ auto-power spectrum and it significantly improves a constraint on the mass
dependence of the mass bias. The redshift dependence is not strongly
constrained since the multipole range in which high redshift clusters mainly
contribute to the tSZ auto is dominated by the contaminating sources. We
conclude that no strong mass or redshift evolution of the mass bias is needed
to explain the data. |
Can denoising diffusion probabilistic models generate realistic
astrophysical fields?: Score-based generative models have emerged as alternatives to generative
adversarial networks (GANs) and normalizing flows for tasks involving learning
and sampling from complex image distributions. In this work we investigate the
ability of these models to generate fields in two astrophysical contexts: dark
matter mass density fields from cosmological simulations and images of
interstellar dust. We examine the fidelity of the sampled cosmological fields
relative to the true fields using three different metrics, and identify
potential issues to address. We demonstrate a proof-of-concept application of
the model trained on dust in denoising dust images. To our knowledge, this is
the first application of this class of models to the interstellar medium. | Measuring the Dark Matter Halo Mass of X-ray AGN at z~1 using
photometric redshifts: Data from the AEGIS, COSMOS and ECDFS surveys are combined to infer the bias
and dark matter halo mass of moderate luminosity [LX(2-10 keV) = 42.9 erg s-1]
X-ray AGN at z~1 via their cross-correlation function with galaxies. In
contrast to standard cross-correlation function estimators, we present a method
that requires spectroscopy only for the AGN and uses photometric redshift
probability distribution functions for galaxies to determine the projected
real-space AGN/galaxy cross-correlation function. The estimated dark matter
halo mass of X-ray AGN in the combined AEGIS, COSMOS and ECDFS fields is
~13h-1M_solar, in agreement with previous studies at similar redshift and
luminosity ranges. Removing from the sample the 5 per cent of the AGN
associated with X-ray selected groups results in a reduction by about 0.5 dex
in the inferred AGN dark matter halo mass. The distribution of AGN in dark
matter halo mass is therefore skewed and the bulk of the population lives in
moderate mass haloes. This result favour cold gas accretion as the main channel
of supermassive black hole growth for most X-ray AGN. |
Dark Energy after GW170817 and GRB170817A: The observation of GW170817 and its electromagnetic counterpart implies that
gravitational waves travel at the speed of light, with deviations smaller than
a few $\times 10^{-15}$. We discuss the consequences of this experimental
result for models of dark energy and modified gravity characterized by a single
scalar degree of freedom. To avoid tuning, the speed of gravitational waves
must be unaffected not only for our particular cosmological solution, but also
for nearby solutions obtained by slightly changing the matter abundance. For
this to happen the coefficients of various operators must satisfy precise
relations that we discuss both in the language of the Effective Field Theory of
Dark Energy and in the covariant one, for Horndeski, beyond Horndeski and
degenerate higher-order theories. The simplification is dramatic: of the three
functions describing quartic and quintic beyond Horndeski theories, only one
remains and reduces to a standard conformal coupling to the Ricci scalar for
Horndeski theories. We show that the deduced relations among operators do not
introduce further tuning of the models, since they are stable under quantum
corrections. | Testing Gravity using Cosmic Voids: We explore voids in dark matter and halo fields from simulations of
$\Lambda$CDM and Hu-Sawicki $f(R)$ models. In $f(R)$ gravity, dark matter void
abundances are greater than that of general relativity (GR). However, when
using haloes to identify voids, the differences of void abundances become much
smaller, but can still be told apart, in principle, at the 2, 6 and 14 $\sigma$
level for the $f(R)$ model parameter amplitudes of $|f_{R0}|=10^{-6}$,
$10^{-5}$ and $10^{-4}$. In contrast, the abundance of large voids found using
haloes in $f(R)$ gravity is lower than in GR. The more efficient halo formation
in underdense regions makes $f(R)$ voids less empty of haloes. This counter
intuitive result suggests that voids are not necessarily emptier in $f(R)$ if
one looks at galaxies in voids. Indeed, the halo number density profiles of
voids are not distinguishable from GR. However, the same $f(R)$ voids are more
empty of dark matter. This can in principle be observed by weak gravitational
lensing of voids, for which the combination of a spec-$z$ and a photo-$z$
survey over the same sky is necessary. For a volume of 1~(Gpc/$h$)$^3$,
neglecting the lensing shape noise, $|f_{R0}|=10^{-5}$ and $10^{-4}$ may be
distinguished from GR using the lensing tangential shear signal around voids by
4 and 8$\sigma$. The line-of-sight projection of large-scale structure is the
main systematics that limits the significance of this signal, limiting the
constraining power for $|f_{R0}|=10^{-6}$. The halo void abundance being
smaller and the steepening of dark matter void profiles in $f(R)$ models are
unique features that can be combined to break the degeneracy between $|f_{R0}|$
and $\sigma_8$. The outflow of mass from void centers and velocity dispersions
are greater in $f(R)$. Model differences in velocity profiles imply potential
powerful constraints of the model in phase space and in redshift space. |
A LOFAR study of non-merging massive galaxy clusters: Centrally located diffuse radio emission has been observed in both merging
and non-merging galaxy clusters. Depending on their morphology and size, we
distinguish between giant radio haloes, which occur predominantly in merging
clusters, and mini haloes, which are found in non-merging, cool-core clusters.
Low-frequency sensitive observations are required to assess whether the
emission discovered in these few cases is common in galaxy clusters or not.
With this aim, we carried out a campaign of observations with the LOw Frequency
ARay (LOFAR) in the frequency range 120 - 168 MHz of nine massive clusters
selected from the \textit{Planck} SZ catalogue, which had no sign of major
mergers. In this paper, we discuss the results of the observations that have
led to the largest cluster sample studied within the LOFAR Two-metre Sky
Survey, and we present Chandra X-ray data used to investigate the dynamical
state of the clusters, verifying that the clusters are currently not undergoing
major mergers, and to search for traces of minor or off-axis mergers. We
discover large-scale steep-spectrum emission around mini haloes in the
cool-core clusters PSZ1G139 and RXJ1720, which is not observed around the mini
halo in the non-cool-core cluster A1413. We also discover a new 570 kpc-halo in
the non-cool-core cluster RXCJ0142. We derived new upper limits to the radio
power for clusters in which no diffuse radio emission was found, and we discuss
the implication of our results to constrain the cosmic-ray energy budget in the
ICM. We conclude that radio emission in non-merging massive clusters is not
common at the sensitivity level reached by our observations and that no clear
connection with the cluster dynamical state is observed. Our results might
indicate that the sloshing of a dense cool core could trigger particle
acceleration on larger scales and generate steep-spectrum radio emission. | Signatures of inhomogeneous dark matter annihilation on 21-cm: The energy released from dark matter annihilation leads to additional
ionization and heating of the intergalactic gas and thereby impact the hydrogen
21-cm signal during the cosmic dawn. The dark matter annihilation rate scales
as density-squared and it becomes inhomogeneously boosted along with structure
formation. This paper examines the inhomogeneity in DM annihilation rate
induced by the growth of DM halo structures, and we show that this effect can
significantly enhance the spatial fluctuations in gas temperature, gas
ionization fraction and consequently the 21-cm brightness temperature. Compared
to previous homogeneous calculations, inhomogeneous dark matter annihilation
can enhance the 21-cm power spectrum by orders of magnitude across the scales
of $k \in [0.05, 3]\ {\rm{Mpc^{-1}}}$. For a DM annihilation rate of
$\left<\sigma v\right>/m_\chi \sim 10^{-27} {\rm cm^3 s^{-1} GeV^{-1}}$, the
corresponding signatures in the 21-cm power spectrum signal can be detected by
upcoming radio observatories such as the SKA. |
Primordial black holes as dark matter and gravitational waves from bumpy
axion inflation: We consider a mechanism for producing a significant population of primordial
black holes (PBHs) and an observable stochastic gravitational wave background
(SGWB) within string theory inspired models of inflation. In this framework
where inflaton is identified as a non-compact axion-like field, sub-leading
non-perturbative effects can superimpose steep cliffs connected by smooth
plateaus onto the underlying axion potential. In the presence of coupling to
Abelian gauge fields, the motion of axion on the cliff-like region(s) of its
potential triggers a localized production of one helicity state of gauge fields
due to the temporary fast-roll of axion around such a feature. In this setup,
primordial fluctuations sourced by vector fields exhibit a localized peak in
momentum space corresponding to modes that exit the horizon when the axion
velocity is maximal. As an application of this general mechanism, we present an
example of axion inflation which both matches Planck observations at CMB scales
and generates a population of light PBHs ($M_{\rm PBH} \simeq 10^{-13}
M_{\odot}$) that can account for all dark matter. In this scenario, the
enhanced scalar fluctuations that leads to PBHs also generate an observable
SGWB of induced origin at LISA scales. The amplitude and shape of the resulting
GW signal inherits specific properties (such as non-Gaussianity and its shape)
of its scalar sources that may allow us to distinguish this mechanism from
other inflationary scenarios and astrophysical backgrounds. This GW signal
together with an observation of PBH distribution at the corresponding scales
can thus provide a window to the inflationary dynamics on scales much smaller
than those probed by Cosmic Microwave Background (CMB) and Large Scale
Structure (LSS) Measurements. | Tomographic Magnification of Lyman Break Galaxies in The Deep Lens
Survey: Using about 450,000 galaxies in the Deep Lens Survey, we present a detection
of the gravitational magnification of z > 4 Lyman Break Galaxies by massive
foreground galaxies with 0.4 < z < 1.0, grouped by redshift. The magnification
signal is detected at S/N greater than 20, and rigorous checks confirm that it
is not contaminated by any galaxy sample overlap in redshift. The inferred
galaxy mass profiles are consistent with earlier lensing analyses at lower
redshift. We then explore the tomographic lens magnification signal by
splitting our foreground galaxy sample into 7 redshift bins. Combining
galaxy-magnification cross-correlations and galaxy angular auto-correlations,
we develop a bias-independent estimator of the tomographic signal. As a
diagnostic of magnification tomography, the measurement of this estimator
rejects a flat dark matter dominated Universe at > 7.5{\sigma} with a fixed
\sigma_8 and is found to be consistent with the expected redshift-dependence of
the WMAP7 {\Lambda}CDM cosmology. |
Reconstructing large scales at cosmic dawn: The cosmic microwave background (CMB) serves as a backlight to large-scale
structure during the epoch of reionization, where Thomson scattering gives rise
to temperature anisotropies on small angular scales from the kinetic Sunyaev
Zel'dovich (kSZ) effect. In this paper, we demonstrate that the technique of
kSZ tomography (velocity reconstruction), based on cross correlations between
CMB temperature and 21cm surveys, can significantly improve constraints on
models of inhomogeneous reionization and provide information about large-scale
modes that are poorly characterized by 21cm measurements themselves due to
foreground contamination. | Testing gravity with gravitational wave friction and gravitational slip: Gravitational waves (GWs) emitted by binary sources are interesting signals
for testing gravity on cosmological scales since they allow measurements of the
luminosity distance. When followed by electromagnetic counterparts, in
particular, they enable a reconstruction of the GW-distance-redshift relation.
In the context of several modified gravity (MG) theories, even when requiring
that the speed of propagation is equal to that of light, this GW distance
differs from the standard electromagnetic luminosity distance due to the
presence of a modified friction in the GW propagation. The very same source of
this friction, which is the running of an effective Planck mass, also affects
the scalar sector generating gravitational slip, i.e. a difference between the
scalar potentials, an observable that can be inferred from large-scale
structure (LSS) probes. In this work, we use a model within effective field
theories for dark energy to exemplify precisely the fact that, at the linear
perturbation level, parametrizing a single function is already enough to
generate simultaneous deviations in the GW distance and the slip. By simulating
multi-messenger GW events that might be detected by the Einstein Telescope in
the future, we compare the constraining power of the two observables on this
single degree of freedom. We then combine forecasts of a Euclid-like survey
with GW simulations, coming to the conclusion that, when using Planck data to
better constrain the cosmological parameters, those future data on the scalar
and tensor sectors are competitive to probe such deviations from General
Relativity, with LSS giving stronger (but more model-dependent) results than
GWs. |
Quenching Star Formation: Can AGN Do the Trick?: We post-process galaxy star formation histories in cosmological hydrodynamics
simulations to test quenching mechanisms associated with AGN. By comparing
simulation results to color-magnitude diagrams and luminosity functions of SDSS
galaxies, we examine whether "quasar mode" or "radio mode" AGN feedback can
yield a realistic red sequence. Both cases yield red sequences distinct from
the blue cloud, decent matches to the luminosity function, and galaxies that
are too blue by about 0.1 magnitudes in g-r. Our merger-based prescription for
quasar mode feedback, however, yields a red sequence build-up inconsistent with
observations: the luminosity function lacks a characteristic knee, and the
brightest galaxies include a small number of young stars. | Study of the Intracluster and Intergalactic Medium in the Sculptor
Supercluster with Suzaku: We studied the high temperature plasma in the direction of the Sculptor
supercluster at z=0.108 with Suzaku. Suzaku carried out four observations in
the supercluster: namely, A2811, A2811 offset, A2804, A2801 regions in 2005
Nov.--Dec., including the regions beyond the virial radii of these clusters.
The study needed precise background estimation because the measured intensity
of the redshifted lines, especially those from oxygen, were strongly affected
by the the Galactic emission. The spectra taken in the regions outside of the
virial radii of the member clusters were used as the background which included
both the Galactic and Cosmic X-ray Background (CXB) components. We also used
the background data which were taken near the Sculptor supercluster.
Temperature and metal abundance profiles were determined to the virial radii of
the member clusters, and then we searched for the oxygen line emission in the
region outside of the virial radii of the clusters. As a result, the
temperature of the clusters decreased toward the virial radii, and the spectral
fits for the filament region did not require extra component other than the
Galactic and CXB components. We constrained the intensities of O VII and O VIII
lines to be less than 8.1 and 5.1 photons cm^-2 s^-1 arcmin^-2, respectively,
as 2-sigma upper limits. The intensity of O VII indicates n_H < 1.6e-5 cm^-3
(Z/0.1 Z_solar)^-1/2 (L/25 Mpc)^-1/2, which corresponds to an over density,
delta < 60 (Z/0.1 Z_solar)^-1/2 (L/25 Mpc)^-1/2. |
Global structure of the Local Universe according to 2MRS survey: We report the results of a statistical analysis of the space distribution of
galaxies within distances about 300 Mpc using the 2MRS catalog, which contains
redshifts of 43533 galaxies of the 2MASS all-sky IR survey. Because of the
unique features of the 2MRS survey, such as its 90 percent sky coverage, galaxy
selection in the IR, the complete incorporation of the old stellar population
of galaxies, weakness of the dust extinction effects, and the smallness of the
k- and e-corrections allowed us to determine the statistical properties of the
global distribution of galaxies in the Local Universe. We took into account the
main methodological factors that distort the theoretically expected relations
compared to those actually observed. We construct the radial galaxy number
counts N(R), SL(R, r) statistics, and the complete correlation function
(conditional density) for volume-limited (VL) galaxy samples. The observed
conditional density in the redshift space is independent of the luminosity of
galaxies and has the form of a power-law function with slope ~ 1.0 over a large
range scale-length spanning from 0.1 to 100 Mpc. We compare the statistical
properties of the space distribution of galaxies of the 2MRS catalog with the
corresponding properties of simulated catalogs: stochastic fractal
distributions and galaxies of the Millennium catalog. | Improved time-delay lens modelling and $H_0$ inference with transient
sources: Strongly lensed explosive transients such as supernovae, gamma-ray bursts,
fast radio bursts, and gravitational waves are very promising tools to
determine the Hubble constant ($H_0$) in the near future in addition to
strongly lensed quasars. In this work, we show that the transient nature of the
point source provides an advantage over quasars: the lensed host galaxy can be
observed before or after the transient's appearance. Therefore, the lens model
can be derived from images free of contamination from bright point sources. We
quantify this advantage by comparing the precision of a lens model obtained
from the same lenses with and without point sources. Based on Hubble Space
Telescope (HST) Wide Field Camera 3 (WFC3) observations with the same sets of
lensing parameters, we simulate realistic mock datasets of 48 quasar lensing
systems (i.e., adding AGN in the galaxy center) and 48 galaxy-galaxy lensing
systems (assuming the transient source is not visible but the time delay and
image positions have been or will be measured). We then model the images and
compare the inferences of the lens model parameters and $H_0$. We find that the
precision of the lens models (in terms of the deflector mass slope) is better
by a factor of 4.1 for the sample without lensed point sources, resulting in an
increase of $H_0$ precision by a factor of 2.9. The opportunity to observe the
lens systems without the transient point sources provides an additional
advantage for time-delay cosmography over lensed quasars. It facilitates the
determination of higher signal-to-noise stellar kinematics of the main
deflector, and thus its mass density profile, which in turn plays a key role in
breaking the mass-sheet degeneracy and constraining $H_0$. |
Small and young radio sources: It is currently accepted that compact and bright radio sources characterized
by a convex spectrum peaking at frequencies ranging from 100 MHz to a few GHz
are young objects. In this scenario, high frequency peaker (HFP) radio sources,
with a turnover frequency higher than 5 GHz are good candidates to be extremely
young radio sources with ages of up to a few thousand years. The knowledge of
the conditions in young radio source is fundamental in order to draw reliable
evolution models able to describe the entire life-cycle of the radio emission.
Given the high spatial resolution and the large frequency range spanned, VLBI
observations provide a unique opportunity to constrain the physical conditions
in young radio sources, and to investigate the role played by the environment
on the source growth. | Resummed Kinetic Field Theory: general formalism and linear structure
growth from Newtonian particle dynamics: In earlier work, we have developed a nonequilibrium statistical field theory
description of cosmic structure formation, dubbed Kinetic Field Theory (KFT),
which is based on the Hamiltonian phase-space dynamics of classical particles
and thus remains valid beyond shell-crossing. Here, we present an exact
reformulation of the KFT framework that allows to resum an infinite subset of
terms appearing in the original perturbative expansion of KFT. We develop the
general formalism of this resummed KFT, including a diagrammatic language for
the resummed perturbation theory, and compute the lowest-order results for the
power spectra of the dark matter density contrast and momentum density. This
allows us to derive analytically how the linear growth of the largest
structures emerges from Newtonian particle dynamics alone, which, to our
knowledge, is the first time this has been achieved. |
A direct method to compute the galaxy count angular correlation function
including redshift-space distortions: In the near future, cosmology will enter the wide and deep galaxy survey area
allowing high-precision studies of the large scale structure of the universe in
three dimensions. To test cosmological models and determine their parameters
accurately, it is natural to confront data with exact theoretical expectations
expressed in the observational parameter space (angles and redshift). The
data-driven galaxy number count fluctuations on redshift shells, can be used to
build correlation functions $C(\theta; z_1, z_2)$ on and between shells which
can probe the baryonic acoustic oscillations, the distance-redshift distortions
as well as gravitational lensing and other relativistic effects. Transforming
the model to the data space usually requires the computation of the angular
power spectrum $C_\ell(z_1, z_2)$ but this appears as an artificial and
inefficient step plagued by apodization issues. In this article we show that it
is not necessary and present a compact expression for $C(\theta; z_1, z_2)$
that includes directly the leading density and redshift space distortions terms
from the full linear theory. It can be evaluated using a fast integration
method based on Clenshaw-Curtis quadrature and Chebyshev polynomial series.
This new method to compute the correlation functions without any Limber
approximation, allows us to produce and discuss maps of the correlation
function directly in the observable space and is a significant step towards
disentangling the data from the tested models. | An inflation model for massive primordial black holes to interpret the
JWST observations: The first observations of the James Webb Space Telescope (JWST) have
identified six massive galaxy candidates with the stellar masses $M_\ast\gtrsim
10^{10}\,M_\odot$ at high redshifts $7.4\lesssim z\lesssim 9.1$, with two most
massive high-$z$ objects having the cumulative comoving number densities
$n_{\rm G}$ up to $1.6\times 10^{-5}\, {\rm Mpc}^{-3}$. The presence of such
massive sources in the early universe challenges the standard $\Lambda$CDM
model since the needed star formation efficiency is unrealistically high. This
tension can be alleviated via the accretion of massive primordial black holes
(PBHs). In this work, with the updated data from the first JWST observations,
we find that the PBHs with mass $10^8\,M_\odot\lesssim M_{\rm PBH}\lesssim
10^{11}\,M_\odot$ can act as the seeds of extremely massive galaxies even with
a low abundance $10^{-7}\lesssim f_{\rm PBH}\lesssim 10^{-3}$. We construct an
ultraslow-roll inflation model and investigate its possibility of producing the
required PBHs. We explore the model in two cases, depending on whether there is
a perfect plateau on the inflaton potential. If the plateau is allowed to
incline slightly, our model can produce the PBHs that cover the required PBH
mass and abundance range to explain the JWST data. |
BICEP / Keck XIII: Improved Constraints on Primordial Gravitational
Waves using Planck, WMAP, and BICEP/Keck Observations through the 2018
Observing Season: We present results from an analysis of all data taken by the BICEP2, Keck
Array and BICEP3 CMB polarization experiments up to and including the 2018
observing season. We add additional Keck Array observations at 220 GHz and
BICEP3 observations at 95 GHz to the previous 95/150/220 GHz data set. The
$Q/U$ maps now reach depths of 2.8, 2.8 and 8.8 $\mu{\mathrm K}_{cmb}$ arcmin
at 95, 150 and 220 GHz respectively over an effective area of $\approx 600$
square degrees at 95 GHz and $\approx 400$ square degrees at 150 & 220 GHz. The
220 GHz maps now achieve a signal-to-noise on polarized dust emission exceeding
that of Planck at 353 GHz. We take auto- and cross-spectra between these maps
and publicly available WMAP and Planck maps at frequencies from 23 to 353 GHz
and evaluate the joint likelihood of the spectra versus a multicomponent model
of lensed-$\Lambda$CDM+$r$+dust+synchrotron+noise. The foreground model has
seven parameters, and no longer requires a prior on the frequency spectral
index of the dust emission taken from measurements on other regions of the sky.
This model is an adequate description of the data at the current noise levels.
The likelihood analysis yields the constraint $r_{0.05}<0.036$ at 95%
confidence. Running maximum likelihood search on simulations we obtain unbiased
results and find that $\sigma(r)=0.009$. These are the strongest constraints to
date on primordial gravitational waves. | Low surface brightness galaxies mass profiles as a consequence of
galactic evolution: This paper presents a principal components analysis of rotation curves from a
sample of low surface brightness galaxies. The physical meaning of the
principal components is investigated, and related to the intrinsic properties
of the galaxies. The rotation curves are re-scaled using the optical disk
scale, the resulting principal component decomposition demonstrates that the
whole sample is properly approximated using two components. The ratio of the
second to the first component is related to the halo steepness in the central
region, is correlated to the gas fraction in the galaxy, and is un-correlated
to other parameters. As a consequence the gas fraction appear as a fundamental
variable with respect to the galaxies rotation curves, and its correlation with
the halo steepness is especially important. Since the gas fraction is related
to the degree of galaxy evolution, it is very likely that the steepness of the
halo at the center is a consequence of galaxy evolution. More evolved galaxies
have shallower central profile and statistically less gas, most likely as a
consequence of more star formation and supernovae. The differences in
evolution, gas fractions and halo central steepness of the galaxies could be
due to the influence of different environments. |
Gravitational wave microlensing by dressed primordial black holes: We study gravitational wave microlensing by primordial black holes (PBHs),
accounting for the effect of a particle dark matter minihalo surrounding them.
Such minihaloes are expected when PBHs make up only a fraction of all dark
matter. We find that the LIGO-Virgo detections imply a $1\sigma$ bound on the
abundance of PBHs heavier than $50 M_{\odot}$. The next generation
observatories can potentially probe PBHs as light as $0.01 M_\odot$ and down to
$2\times10^{-4}$ fraction of all dark matter. We also show that these detectors
can distinguish between dressed and naked PBHs, providing a novel way to study
the distribution of particle dark matter around black holes and potentially
shed light on the origins of black holes. | Identification of (high-redshift) AGN with WFXT: lessons from COSMOS and
CDFS: The Wide Field X-ray Telescope (WFXT) will provide tens of millions of AGN,
with more than 4x10^5 expected at z>3. Here we review the issues present in the
identification of (large) samples of faint and high-redshift X-ray sources, and
describe a statistical, powerful tool that can be applied to WFXT catalogs. The
depth of associated optical and near infrared catalogs, needed for a reliable
and as much complete as possible identification, are also discussed, along with
the combined synergies with existing or planned facilities |
Molecular gas in galaxies at all redshifts: I review some recent results about the molecular content of galaxies,
obtained essentially from the CO lines, but also dense tracers, or the dust
continuum emission. New results have been obtained on molecular cloud physics,
and their efficiency to form stars, shedding light on the Kennicutt-Schmidt law
as a function of surface density and galaxy type.
Large progress has been made on galaxy at moderate and high redshifts,
allowing to interprete the star formation history and star formation efficiency
as a function of gas content, or galaxy evolution.
In massive galaxies, the gas fraction was higher in the past, and galaxy
disks were more unstable and more turbulent.
ALMA observations will allow the study of more normal galaxies at high z with
higher spatial resolution and sensitivity. | Cosmological Evolution With Interaction Between Dark Energy And Dark
Matter: In this review we consider in detail different theoretical topics associated
with interaction in the dark sector. We study linear and nonlinear interactions
which depend on the dark matter and dark energy densities. We consider a number
of different models (including the holographic dark energy and dark energy in a
fractal universe) with interacting dark energy (DE) and dark matter (DM), have
done a thorough analysis of these models. The main task of this review was not
only to give an idea about the modern set of different models of dark energy,
but to show how much can be diverse dynamics of the universe in these models.
We find that the dynamics of a Universe that contains interaction in the dark
sector can differ significantly from the Standard Cosmological Model (SCM). |
New probability distributions in astrophysics: I. The truncated
generalized gamma: The gamma function is a good approximation to the luminosity function of
astrophysical objects, and a truncated gamma distribution would permit a more
rigorous analysis. This paper examines the generalized gamma distribution (GG)
and then introduces the scale and the new double truncation. The magnitude
version of the truncated GG distribution with scale is adopted in order to fit
the luminosity function (LF) for galaxies or quasars. The new truncated GG LF
is applied to the five bands of SDSS galaxies, to the 2dF QSO Redshift Survey
in the range of redshifts between 0.3 and 0.5, and to the COSMOS QSOs in the
range of redshifts between 3.7 and 4.7. The average absolute magnitude versus
redshifts for SDSS galaxies and QSOs of 2dF was modeled adopting a redshift
dependence for the lower and upper absolute magnitude of the new truncated GG
LF. | Kinetic Field Theory: Perturbation theory beyond first order: We present recent improvements in the perturbative treatment of particle
interactions in Kinetic Field Theory (KFT) for inertial Zel'dovich
trajectories. KFT has been developed for the systematic analytical calculation
of non-linear cosmic structure formation on the basis of microscopic
phase-space dynamics. We improve upon the existing treatment of the interaction
operator by deriving a more rigorous treatment of phase-space trajectories of
particles in an expanding universe. We then show how these results can be
applied to KFT perturbation theory by calculating corrections to the late-time
dark matter power spectrum at second order in the interaction operator. We find
that the modified treatment of interactions w.r.t. inertial Zel'dovich
trajectories improves the agreement of KFT with simulation results on
intermediate scales compared to earlier results. Additionally, we illustrate
that including particle interactions up to second order leads to a systematic
improvement of the non-linear power spectrum compared to the first-order
result. |
Unified dark energy and dark matter from a scalar field different from
quintessence: We explore unification of dark matter and dark energy in a theory containing
a scalar field of non-Lagrangian type, obtained by direct insertion of a
kinetic term into the energy-momentum tensor. This scalar is different from
quintessence, having an equation of state between -1 and 0 and a zero sound
speed in its rest frame. We solve the equations of motion for an exponential
potential via a rewriting as an autonomous system, and demonstrate the
observational viability of the scenario, for sufficiently small exponential
potential parameter \lambda, by comparison to a compilation of kinematical
cosmological data. | Constraints on the dark energy with barotropic equation of state:
assessing the importance of different observations: For dynamical dark energy with the barotropic equation of state we determine
the mean values of parameters and their confidence ranges together with other
cosmological parameters on the basis of different combined datasets. The used
observations include Planck data on CMB temperature anisotropy, E-mode
polarization and lensing, BICEP2/Keck Array data on B-mode polarization, BAO
from SDSS and 6dFGS, power spectrum of galaxies from WiggleZ, weak lensing from
CFHTLenS and SN Ia data from the JLA compilation. We find that all but one mean
models are phantom, mean values of the equation of state parameter at current
epoch are close to $-1$ and constraints on the adiabatic sound speed of dark
energy are weak. We investigate the effect of CMB polarization data on the dark
energy parameters estimation. We discuss also which type of data on the large
scale structure of the Universe allows to determine the dark energy parameters
most precisely. |
Accurate Modeling of the Projected Galaxy Clustering in Photometric
Surveys: I. Tests with Mock Catalogs: We develop a novel method to explore the galaxy-halo connection using the
galaxy imaging surveys by modeling the projected two-point correlation function
measured from the galaxies with reasonable photometric redshift measurements.
By assuming a Gaussian form of the photometric redshift errors, we are able to
simultaneously constrain the halo occupation distribution (HOD) models and the
effective photometric redshift uncertainties. Tests with mock galaxy catalogs
demonstrate that this method can successfully recover (within $\sim 1\sigma$)
the intrinsic large-scale galaxy bias, as well as the HOD models and the
effective photometric redshift uncertainty. This method also works well even
for galaxy samples with 10 per cent catastrophic photometric redshift errors. | The Origin of Color Gradients in Early-Type Systems and Their
Compactness at High-z: In this Letter, we present mean optical+NIR color gradient estimates for 5080
early-type galaxies (ETGs) in the grizYJHK wavebands of the Sloan Digital Sky
Survey (SDSS) plus UKIRT Infrared Deep Sky Survey (UKIDSS). The color gradient
is estimated as the logarithmic slope of the radial color profile in ETGs. With
such a large sample size, we study the variation of the mean color gradient as
a function of waveband with unprecedented accuracy. We find that (i) color
gradients are mainly due, on average, to a metallicity variation of about
-0.4dex per decade in galaxy radius; and (ii) a small, but significant,
positive age gradient is present, on average, in ETGs, with the inner stellar
population being slightly younger, by ~0.1dex per radial decade, than the outer
one. Also, we show that the presence of a positive mean age gradient in ETGs,
as found in the present study, implies their effective radius to be smaller at
high z, consistent with observations. |
Comments on gauge-invariance in cosmology: We revisit the gauge issue in cosmological perturbation theory, and highlight
its relation to the notion of covariance in general relativity. We also discuss
the similarities and differences of the covariant approach in perturbation
theory to the Bardeen or metric approach in a non-technical fashion. | Ammonia (J,K) = (1,1) to (4,4) and (6,6) inversion lines detected in the
Seyfert 2 galaxy NGC 1068: We present the detection of the ammonia (NH3) (J,K) = (1,1) to (4,4) and
(6,6) inversion lines toward the prototypical Seyfert 2 galaxy NGC 1068, made
with the Green Bank Telescope (GBT). This is the first detection of ammonia in
a Seyfert galaxy. The ortho-to-para-NH3 abundance ratio suggests that the
molecule was formed in a warm medium of at least 20 K. For the NH3 column
density and fractional abundance, we find (1.09\pm0.23)\times10^14 cm^-2 and
(2.9\pm0.6)\times10^-8, respectively, from the inner 1.2 kpc of NGC 1068. The
kinetic temperature can be constrained to 80\pm20 K for the bulk of the
molecular gas, while some fraction has an even higher temperature of 140\pm30
K. |
Radiative cooling functions for primordial molecules: Cooling of primordial gas plays a crucial role in the birth of the first
structures in our Universe. Due to the low fractional abundance of molecular
species at high redshifts, spontaneous emission rather than collisions
represents the most efficient way to cool the pristine plasma. In the present
work, radiative cooling functions are evaluated for the diatomic species HD,
HD$^+$, HeH$^+$, LiH and LiH$^+$. Cooling functions for the triatomic ions
H$_3^+$ and H$_2$D$^+$ are also considered. Analytic fits as functions of
temperature are provided. | Inferences of $H_0$ in presence of a non-standard recombination: Measurements of the Hubble parameter from the distance ladder are in tension
with indirect measurements based on the cosmic microwave background (CMB) data
and the inverse distance ladder measurements at 3-4 $\sigma$ level. We consider
phenomenological modification to the timing and width of the recombination
process and show that they can significantly affect this tension. This
possibility is appealing, because such modification affects both the distance
to the last scattering surface and the calibration of the baryon acoustic
oscillations (BAO) ruler. Moreover, because only a very small fraction of the
most energetic photons keep the early universe in the plasma state, it is
possible that such modification could occur without affecting the energy
density budget of the universe or being incompatible with the very tight limits
on the departure from the black-body spectrum of CMB. In particular, we find
that under this simplified model, with a conservative subset of Planck data
alone, $H_0=73.44_{-6.77}^{+5.50}~{\rm km\ s}^{-1}\ {\rm Mpc}^{-1}$ and in
combination with BAO data $H_0=68.86_{-1.35}^{+1.31}~{\rm km\ s}^{-1}\ {\rm
Mpc}^{-1}$, decreasing the tension to $\sim 2\sigma$ level. However, when
combined with Planck lensing reconstruction and high-$\ell$ polarization data,
the tension climbs back to $\sim 2.7\sigma$, despite the uncertainty on
non-ladder $H_0$ measurement more than doubling. |
Analytical studies on the Sunyaev-Zeldovich effect in the cluster of
galaxies for three Lorentz frames II: single integral formula: We study the Sunyaev-Zeldovich effect for clusters of galaxies. The Boltzmann
equations for the cosmic microwave background photon distribution function are
studied in three Lorentz frames. We extend the previous work and derive
analytic expressions for the integrated photon redistribution functions over
the photon frequency. We also derive analytic expressions in the power series
expansion approximation. By combining two formulas, we offer a simple and
accurate tool to analyse observation data. These formulas are applicable to the
non-thermal electron distributions as well as the standard thermal
distribution. The Boltzmann equation is reduced to a single integral form of
the electron velocity. | Growth factor and galaxy bias from future redshift surveys: a study on
parametrizations: Many experiments in the near future will test dark energy through its effects
on the linear growth of matter perturbations. In this paper we discuss the
constraints that future large-scale redshift surveys can put on three different
parameterizations of the linear growth factor and how these constraints will
help ruling out different classes of dark energy and modified gravity models.
We show that a scale-independent bias can be estimated to a few percent per
redshift slice by combining redshift distortions with power spectrum amplitude,
without the need of an external estimation. We find that the growth rate can be
constrained to within 2-4% for each $\Delta z=0.2$ redshift slice, while the
equation of state $w$ and the index $\gamma$ can be simultaneously estimated
both to within 0.02. We also find that a constant dimensionless coupling
between dark energy and dark matter can be constrained to be smaller than 0.14. |
An analysis of constraints on relativistic species from primordial
nucleosynthesis and the cosmic microwave background: We present constraints on the number of relativistic species from a joint
analysis of cosmic microwave background (CMB) fluctuations and light element
abundances (helium and deuterium) compared to big bang nucleosynthesis (BBN)
predictions. Our BBN calculations include updates of nuclear rates in light of
recent experimental and theoretical information, with the most significant
change occuring for the d(p,gamma)^3He cross section. We calculate a likelihood
function for BBN theory and observations that accounts for both observational
errors and nuclear rate uncertainties and can be easily embedded in
cosmological parameter fitting. We then demonstrate that CMB and BBN are in
good agreement, suggesting that the number of relativistic species did not
change between the time of BBN and the time of recombination. The level of
agreement between BBN and CMB, as well as the agreement with the standard model
of particle physics, depends somewhat on systematic differences among
determinations of the primordial helium abundance. We demonstrate that
interesting constraints can be derived combining only CMB and D/H observations
with BBN theory, suggesting that an improved D/H constraint would be an
extremely valuable probe of cosmology. | No Slip Gravity: A subclass of the Horndeski modified gravity theory we call No Slip Gravity
has particularly interesting properties: 1) a speed of gravitational wave
propagation equal to the speed of light, 2) equality between the effective
gravitational coupling strengths to matter and light, $G_{\rm matter}$ and
$G_{\rm light}$, hence no slip between the metric potentials, yet difference
from Newton's constant, and 3) suppressed growth to give better agreement with
galaxy clustering observations. We explore the characteristics and implications
of this theory, and project observational constraints. We also give a simple
expression for the ratio of the gravitational wave standard siren distance to
the photon standard candle distance, in this theory and others, and enable a
direct comparison of modified gravity in structure growth and in gravitational
waves, an important crosscheck. |
Identifying the Obscured Black-Hole Growth Phase of Distant Massive
Galaxies: It is well established that a dominant phase in the growth of massive
galaxies occurred at high redshift and was heavily obscured by gas and dust.
Many studies have explored the stellar growth of massive galaxies but few have
combined these constraints with the growth of the supermassive black hole
(SMBH; i.e., identified as AGN activity). In this brief contribution we
highlight our work aimed at identifying AGNs in z~2 luminous dust-obscured
galaxies. Using both sensitive X-ray and infrared (IR)-submillimeter (submm)
observations, we show that AGN activity is common in z~2 dust-obscured systems.
With a variety of techniques we have found that the majority of the AGN
activity is heavily obscured, and construct diagnostics based on X-ray-IR data
to identify some of the most heavily obscured AGNs in the Universe (i.e., AGNs
obscured by Compton-thick material; N_H>1.5x10^24 cm^-2). On the basis of these
techniques we show that SMBH growth was typically heavily obscured (N_H>10^23
cm^-2) at z~2, and find that the growth of the SMBH and spheroid was closely
connected, even in the most rapidly evolving systems. | Spectral variability of IRAS 18325-5926 and constraints on the geometry
of the scattering medium: We analyze Suzaku and XMM-Newton data of the highly variable Seyfert 2, IRAS
18325-5926. The spectra of the source are well modeled as a primary component
described as an absorbed power law and a secondary power law component which is
consistent with being scattered emission from an on-axis extended highly
ionized medium. We show that while the primary component varies on a wide range
of timescales from $10^{4} - 10^{8}$ s, the scattered emission is variable only
on timescales longer than $10^{5}$ s. This implies that the extent of the
scattering medium is greater than $10^{16}$ cm. The ratio of the scattered to
primary flux ($\sim 0.03$) implies a column density for the scattering medium
to be $\sim 10^{23}$ cm$^{-2}$. We argue that for such a medium to be highly
ionized it must be located less than $10^{17}$ cm from the X-ray source. Thus
we localize the position and extent of scattering region to be $\sim$ a few
$\times 10^{16}$ cm, with an average particle density of $\sim 10^{6}$
cm$^{-3}$. We consider the physical interpretation of these results and as an
aside, we confirm the presence of a broad Iron line emission in both the {\it
XMM-Newton} and {\it Suzaku} observations. |
Constraints on the sum of neutrino masses using cosmological data
including the latest extended Baryon Oscillation Spectroscopic Survey DR14
quasar sample: We investigate the constraints on the sum of neutrino masses ($\Sigma m_\nu$)
using the most recent cosmological data, which combines the distance
measurement from baryonic acoustic oscillation in the extended Baryon
Oscillation Spectroscopic Survey DR14 quasar sample with the power spectra of
temperature and polarization anisotropies in the cosmic microwave background
from the Planck 2015 data release. We also use other low-redshift observations
including the baryonic acoustic oscillation at relatively low redshifts, the
supernovae of type Ia and the local measurement of Hubble constant. In the
standard cosmological constant $\Lambda$ cold dark matter plus massive neutrino
model, we obtain the $95\%$ \acl{CL} upper limit to be $\Sigma
m_\nu<0.129~\mathrm{eV}$ for the degenerate mass hierarchy, $\Sigma
m_{\nu}<0.159~\mathrm{eV}$ for the normal mass hierarchy, and $\Sigma
m_{\nu}<0.189~\mathrm{eV}$ for the inverted mass hierarchy. Based on Bayesian
evidence, we find that the degenerate hierarchy is positively supported, and
the current data combination can not distinguish normal and inverted
hierarchies. Assuming the degenerate mass hierarchy, we extend our study to
non-standard cosmological models including the generic dark energy, the spatial
curvature, and the extra relativistic degrees of freedom, respectively, but
find these models not favored by the data. | Relativistic Effect in Galaxy Clustering: The general relativistic description of galaxy clustering provides a complete
and unified treatment of all the effects in galaxy clustering such as the
redshift-space distortion, gravitational lensing, Sachs-Wolfe effects, and
their relativistic effects. In particular, the relativistic description
resolves the gauge issues in the standard Newtonian description of galaxy
clustering by providing the gauge-invariant expression for the observed galaxy
number density. The relativistic effect in galaxy clustering is significant on
large scales, in which dark energy models or alternative theories of modified
gravity deviate from general relativity. In this paper, we review the
relativistic effect in galaxy clustering by providing a pedagogical derivation
of the relativistic formula and by computing the observed galaxy two-point
statistics. The relativistic description of galaxy clustering is an essential
tool for testing general relativity and probing the early Universe on large
scales in the era of precision cosmology. |
X-ray spectral features and classification of selected QSOs: We present the results of a systematic analysis of the XMM-Newton spectra of
nearby optically bright QSOs. The objects have been selected from X-ray Galaxy
Catalog Xgal20. It is a catalog of 1172 manually identified and classified
galaxies, obtained as a cross-correlation between the 4XMM-DR9 catalog and the
Hyper-Linked Extragalactic Databases and Archives (HyperLeda) with an X-ray
flux greater than 1E-13 erg/cm^2/s.
The goal of this work is to characterize the X-ray spectral properties of
selected QSOs in the 0.1 - 10 keV energy band. The majority of the sources (6
out of 11), are classified as radio-quiet QSOs. We studied optical spectra,
hardness ratios and performed X-ray spectral fits for the 10 brighter sources.
In most cases, the power law model with absorption is good enough to simulate
observed continua. Although the details of the spectrum in some sources
significantly complicate the model for fitting. The majority of sources have
steep spectra Gamma > 2.1. Extremely steep photon index 2.4 - 2.5 in our sample
occurs for three radio-loud type I quasars. We detected Fe K-alpha line for two
radio-loud type II quasars. We find no strong evidence for spectral hardening
above 2 keV neither for quasars of type I nor for obscured type II. For each
quasar its type was established both based on the features and details of
observed X-ray spectrum and previous data. | New Geometric Representations of the CMB 2pcf: When searching for deviations of statistical isotropy in CMB, a popular
strategy is to write the two-point correlation function (2pcf) as the most
general function of four spherical angles (i.e., two unit vectors) in the
celestial sphere. Then, using a basis of bipolar spherical harmonics,
statistical anisotropy will show up if and only if any coefficient of the
expansion with non-trivial bipolar momentum is detected -- although this
detection will not in general elucidate the origin of the anisotropy. In this
work we show that two new sets of four angles and basis functions exist which
completely specifies the 2pcf, while, at the same time, offering a clearer
geometrical interpretation of the mechanisms generating the signal. Since the
coefficients of these expansions are zero if and only if isotropy holds, they
act as a simple and geometrically motivated null test of statistical isotropy,
with the advantage of allowing cosmic variance to be controlled in a systematic
way. We report the results of the application of these null tests to the latest
temperature data released by the Planck collaboration. |
Cosmic ray heating of intergalactic medium: patchy or uniform?: We study the heating of the intergalactic medium (IGM) surrounding high
redshift star forming galaxies due to cosmic rays (CR). We take into account
the diffusion of low energy cosmic rays and study the patchiness of the
resulting heating. We discuss the case of IGM heating around a high redshift
minihalo ($z\sim 10\hbox{--}20$, M$\sim 10^5\hbox{--}10^7$ M$_\odot$),and put
an upper limit on the diffusion coefficient $D\le 1\times 10^{26}$ cm$^2$
s$^{-1}$ for the heating to be inhomogeneous at $z\sim 10$ and $D\le
5\hbox{--}6 \times 10^{26}$ cm$^2$ s$^{-1}$ at $z\sim 20$. For typical values
of $D$, our results suggest uniform heating by CR at high redshift, although
there are uncertainties in magnetic field and other CR parameters. We also
discuss two cases with continuous star formation, one in which the star
formation rate (SFR) of a galaxy is high enough to make the IGM in the vicinity
photoionized, and another in which the SFR is low enough to keep it neutral but
high enough to cause significant heating by cosmic ray protons. In the neutral
case (low SFR), we find that the resulting heating can make the gas hotter than
the cosmic microwave background (CMB) radiation for $D < 10^{30}$ cm$^2$
s$^{-1}$, within a few kpc of the galaxy, and unlikely to be probed by near
future radio observations. In the case of photoionized IGM (high SFR), the
resulting heating of the gas in the vicinity of high redshift ($z\sim 4)$
galaxies of mass $\ge 10^{12}$ M$_\odot$ can suppress gas infall into the
galaxy. At lower redshifts ($z\sim 0$), an SFR of $\sim 1$ M$_\odot$ yr$^{-1}$
can suppress the infall into galaxies of mass $\le 10^{10}$ M$_\odot$. | A Model-Insensitive Baryon Acoustic Oscillation Feature in the 21 cm
Signal from Reionization: We examine the impact of baryon-dark matter relative velocities on
intergalactic small-scale structure and the 21 cm signal during reionization.
Streaming velocities reduced clumping in the intergalactic medium (IGM) on mass
scales of $\sim 10^4 - 10^8$ M$_{\odot}$. This effect produced a distinct
baryon acoustic oscillation (BAO) feature in the 21 cm power spectrum at wave
numbers $k\sim 0.1$ h/Mpc, near which forthcoming surveys will be most
sensitive. In contrast to the highly uncertain impact of streaming velocities
on star formation, the effect on clumping is better constrained because it is
set mainly by cosmology and straightforward gas dynamics. We quantify the
latter using coupled radiation-hydrodynamic simulations that capture the Jeans
scale of pre-reionization gas. The clumping factor of ionized gas is reduced by
5-10\% in regions with RMS streaming velocities. The suppression peaks $\approx
5$ Myr after a region is reionized, but disappears within 200 Myr due to
pressure smoothing. We model the corresponding impact on the 21 cm signal and
find that the BAO feature is most likely to appear at $\approx$ 10 \%
ionization. During this phase, the feature may appear at the 1 \% (5 \%) level
at $k \sim 0.1 (0.06)$ h/Mpc with an amplitude that varies by a factor of $<
10$ across a range of reionization histories. We also provide a model for the
signal originating from streaming velocity's impact on ionizing sources, which
can vary by 4 orders of magnitude depending on highly uncertain source
properties. We find that the clumping signal probably dominates the source one
unless Population III star formation in $10^6 - 10^8$ M$_{\odot}$ halos
contributed significantly to the first 10\% of reionization. |
The Pantheon+ Analysis: Dependence of Cosmological Constraints on
Photometric-Zeropoint Uncertainties of Supernova Surveys: Type Ia supernovae (SNe Ia) measurements of the Hubble constant, H$_0$, the
cosmological mass density, $\Omega_M$, and the dark energy equation-of-state
parameter, $w$, rely on numerous SNe surveys using distinct photometric systems
across three decades of observation. Here, we determine the sensitivities of
the upcoming SH0ES+Pantheon+ constraints on H$_0$, $\Omega_M$, and $w$ to
unknown systematics in the relative photometric zeropoint calibration between
the 17 surveys that comprise the Pantheon+ supernovae data set. Varying the
zeropoints of these surveys simultaneously with the cosmological parameters, we
determine that the SH0ES+Pantheon+ measurement of H$_0$ is robust against
inter-survey photometric miscalibration, but that the measurements of
$\Omega_M$ and $w$ are not. Specifically, we find that miscalibrated
inter-survey systematics could represent a source of uncertainty in the
measured value of H$_0$ that is no larger than $0.2$ km s$^{-1}$ Mpc$^{-1}$.
This modest increase in H$_0$ uncertainty could not account for the $7$ km
s$^{-1}$ Mpc$^{-1}$ "Hubble Tension" between the SH0ES measurement of H$_0$ and
the Planck $\Lambda$CDM-based inference of H$_0$. However, we find that the
SH0ES+Pantheon+ best-fit values of $\Omega_M$ and $w$ respectively slip, to
first order, by $0.04$ and $-0.17$ per $25$ mmag of inter-survey calibration
uncertainty, underscoring the vital role that cross-calibration plays in
accurately measuring these parameters. Because the Pantheon+ compendium
contains many surveys that share low-$z$ Hubble Flow and Cepheid-paired SNe,
the SH0ES+Pantheon+ joint constraint of H$_0$ is robust against inter-survey
photometric calibration errors, and such errors do not represent an impediment
to jointly using SH0ES+Pantheon+ to measure H$_0$ to 1% accuracy. | The fate of a Universe driven by a linear potential: We study the proposal to solve the coincidence problem in the non-local
version of the vacuum energy sequestering mechanism by means of a scalar field
in a linear potential. We show that there is no solution in the theory
compatible with observations if one requires the scalar field to drive the
present period of acceleration and the collapse. |
Early assembly of the most massive galaxies: The current consensus is that galaxies begin as small density fluctuations in
the early Universe and grow by in situ star formation and hierarchical merging.
Stars begin to form relatively quickly in sub-galactic sized building blocks
called haloes which are subsequently assembled into galaxies. However, exactly
when this assembly takes place is a matter of some debate. Here we report that
the stellar masses of brightest cluster galaxies, which are the most luminous
objects emitting stellar light, some 9 billion years ago are not significantly
different from their stellar masses today. Brightest cluster galaxies are
almost fully assembled 4-5 Gyrs after the Big Bang, having grown to more than
90% of their final stellar mass by this time. Our data conflict with the most
recent galaxy formation models based on the largest simulations of dark matter
halo development. These models predict protracted formation of brightest
cluster galaxies over a Hubble time, with only 22% of the stellar mass
assembled at the epoch probed by our sample. Our findings suggest a new picture
in which brightest cluster galaxies experience an early period of rapid growth
rather than prolonged hierarchical assembly. | Joint estimation of the Epoch of Reionization power spectrum and
foregrounds: The power spectrum of redshifted 21 cm emission brightness temperature
fluctuations is a powerful probe of the Epoch of Reionization (EoR). However,
bright foreground emission presents a significant impediment to its unbiased
recovery from interferometric data. We build on the Bayesian power spectral
estimation methodology introduced in Sims et al. 2016 and demonstrate that
incorporating a priori knowledge of the spectral structure of foregrounds in
the large spectral scale component of the data model enables significantly
improved modelling of the foregrounds without increasing the model complexity.
We explore two astrophysically motivated parametrisations of the large spectral
scale model: (i) a constant plus power law model of the form
$q_{0}+q_{1}(\nu/\nu_{0})^{b_{1}}$ for two values of $b_{1}$: $b_{1} =
<\beta>_\mathrm{GDSE}$ and $b_{1} = <\beta>_\mathrm{EGS}$, the mean spectral
indices of the Galactic diffuse synchrotron emission and extragalactic source
foreground emission, respectively, and (ii) a constant plus double power law
model of the form $q_{0}+q_{1}(\nu/\nu_{0})^{b_{1}}+q_{2}(\nu/\nu_{0})^{b_{2}}$
with $b_{1} = <\beta>_\mathrm{GDSE}$ and $b_{2} = <\beta>_\mathrm{EGS}$. We
estimate the EoR power spectrum from simulated interferometric data consisting
of an EoR signal, Galactic diffuse synchrotron emission, extragalactic sources
and diffuse free-free emission from the Galaxy. We show that, by jointly
estimating a model of the EoR signal with the constant plus double power law
parametrisation of the large spectral scale model, unbiased estimates of the
EoR power spectrum are recoverable on all spatial scales accessible in the data
set, including on the large spatial scales that were found to be contaminated
in earlier work. |
Panchromatic radiative transfer modeling of stars and dust in the
Sombrero galaxy: We present a detailed study of the dust energy balance in the Sombrero galaxy
M104. From a full radiative transfer analysis, including scattering, absorption
and thermal re-emission, we construct models that can reproduce images at
optical/near-infrared wavelengths, the observed stellar SED and the minor axis
extinction profiles in the V and R_C band. A standard model, that contains only
an old stellar population to heat the dust, underestimates the observations of
dust emission at infrared wavelengths by a factor of ~ 3. Supplementing this
basic model with a young stellar component of low star formation activity in
both the inner disk (SFR ~ 0.21 Msun/yr) and dust ring (SFR ~ 0.05 Msun/yr), we
are capable of solving the discrepancy in the dust energy budget of the
Sombrero galaxy at wavelengths shortwards of 100 \mum. To account for the
increased FIR/submm emission beyond 100 \mum, we propose a additional dust
component distributed in quiescent clumps. This model with a clumpy dust
structure predicts three-quarters of the total dust content (~ 2.8 x 10^7 Msun)
to reside in compact dust clouds with no associated embedded sources. Although
the assumption of a clumpy dust structure in the Sombrero galaxy is supported
by high-resolution optical data, we cannot rule out the possibility that dust
grains with a higher dust emissivity account for part of the discrepancy in the
energy budget at submm wavelengths. | Weak gravitational lensing with CO galaxies: Optical weak lensing surveys have become a powerful tool for precision
cosmology, but remain subject to systematic effects that can severely bias
cosmological parameter estimates if not carefully removed. We discuss the
possibility of performing complementary weak lensing surveys at radio/microwave
frequencies, using detections of CO-emitting galaxies with resolved continuum
images from ngVLA. This method has completely different systematic
uncertainties to optical weak lensing shear measurements (e.g. in terms of
blending, PSF, and redshift uncertainties), and can provide additional
information to help disentangle intrinsic alignments from the cosmological
shear signal. A combined analysis of optical and CO galaxy lensing surveys
would therefore provide an extremely stringent validation of highly-sensitive
future surveys with Euclid, LSST, and WFIRST, definitively rejecting biases due
to residual systematic effects. A lensing survey on ngVLA would also provide
valuable spectral (kinematic) and polarimetric information, which can be used
to develop novel cosmological analyses that are not currently possible in the
optical. |
Incompleteness Matters Not: Inference of $H_0$ from BBH-galaxy
cross-correlations: We show how the angular clustering between gravitational-wave standard sirens
and galaxies with known redshifts allows an inference of the Hubble constant,
regardless of whether the host galaxies of any of these sirens are present in
the galaxy catalog. We demonstrate this for the first time with realistic
simulations of gravitational-wave signals from binary black holes in a
three-detector network with Advanced LIGO and Advanced Virgo sensitivities. We
show that with such a network, the cross-correlation technique can be used to
infer the Hubble parameter with a precision of less than 10% (2%) at 90%
confidence with 50 (500) sources, even with a 100% incomplete catalog, which
does not contain the hosts of any of the gravitational-wave events. We compare
our method with the current state-of-the-art techniques used for the inference
of the Hubble parameter from real data. We argue that, if the clustering
information is not used explicitly, the inference of $H_0$ from real data is
expected to be prior-dominated. | Star formation and UV colors of the brightest Cluster Galaxies in the
representative XMM-Newton Cluster Structure Survey: We present UV broadband photometry and optical emission-line measurements for
a sample of 32 Brightest Cluster Galaxies (BCGs) in clusters of the
Representative XMM-Newton Cluster Structure Survey (REXCESS) with z =
0.06-0.18. The REXCESS clusters, chosen to study scaling relations in clusters
of galaxies, have X-ray measurements of high quality. The trends of star
formation and BCG colors with BCG and host properties can be investigated with
this sample. The UV photometry comes from the XMM Optical Monitor, supplemented
by existing archival GALEX photometry. We detected H\alpha and forbidden line
emission in 7 (22%) of these BCGs, in optical spectra. All of the emission-line
BCGs occupy clusters classified as cool cores, for an emission-line incidence
rate of 70% for BCGs in cool core clusters. Significant correlations between
the H\alpha equivalent widths, excess UV production in the BCG, and the
presence of dense, X-ray bright intracluster gas with a short cooling time are
seen, including the fact that all of the H\alpha emitters inhabit systems with
short central cooling times and high central ICM densities. Estimates of the
star formation rates based on H\alpha and UV excesses are consistent with each
other in these 7 systems, ranging from 0.1-8 solar masses per year. The
incidence of emission-line BCGs in the REXCESS sample is intermediate, somewhat
lower than in other X-ray selected samples (-35%), and somewhat higher than but
statistically consistent with optically selected, slightly lower redshift BCG
samples (-10-15%). The UV-optical colors (UVW1-R-4.7\pm0.3) of REXCESS BCGs
without strong optical emission lines are consistent with those predicted from
templates and observations of ellipticals dominated by old stellar populations.
We see no trend in UV-optical colors with optical luminosity, R-K color, X-ray
temperature, redshift, or offset between X-ray centroid and X-ray peak (<w>). |
Separate Universe calibration of the dependence of halo bias on cosmic
web anisotropy: We use the Separate Universe technique to calibrate the dependence of linear
and quadratic halo bias $b_1$ and $b_2$ on the local cosmic web environment of
dark matter haloes. We do this by measuring the response of halo abundances at
fixed mass and cosmic web tidal anisotropy $\alpha$ to an infinite wavelength
initial perturbation. We augment our measurements with an analytical framework
developed in earlier work which exploits the near-Lognormal shape of the
distribution of $\alpha$ and results in very high precision calibrations. We
present convenient fitting functions for the dependence of $b_1$ and $b_2$ on
$\alpha$ over a wide range of halo mass for redshifts $0\leq z\leq1$. Our
calibration of $b_2(\alpha)$ is the first demonstration to date of the
dependence of non-linear bias on the local web environment. Motivated by
previous results which showed that $\alpha$ is the primary indicator of halo
assembly bias for a number of halo properties beyond halo mass, we then extend
our analytical framework to accommodate the dependence of $b_1$ and $b_2$ on
any such secondary property which has, or can be monotonically transformed to
have, a Gaussian distribution. We demonstrate this technique for the specific
case of halo concentration, finding good agreement with previous results. Our
calibrations will be useful for a variety of halo model analyses focusing on
galaxy assembly bias, as well as analytical forecasts of the potential for
using $\alpha$ as a segregating variable in multi-tracer analyses. | Evidence for possible systematic underestimation of uncertainties in
extragalactic distances and its cosmological implications: 1. We find that any two distance moduli measurements for the same galaxy
differ from each other by 2.07 times the reported one sigma uncertainty on
average.
2. This average difference between distance moduli measurements of the same
galaxy as a multiple of reported uncertainty is growing with time of
publication, rising to 3.00 times the reported one sigma uncertainty for all
distances reported from 2014 to 2018.
3. This average difference between distance moduli measurements of the same
galaxy as a multiple of reported one sigma uncertainty is highest for the
standard candles (3.01) including Cepheids (4.26), Type Ia Supernovae (2.85),
and Tip of the Red Giant Branch (2.82).
4. This data points to a possible systematic underestimation of uncertainties
in extragalactic distances.
5. The results also give a possible way out of the Hubble-Lemaitre tension by
advocating for increasing the error bars on Hubble-Lemaitre constant measured
via distance ladders of standard candles and rulers. |
Cosmic web alignments with the shape, angular momentum and peculiar
velocities of dark matter haloes: We study the alignment of dark matter haloes with the cosmic web
characterized by the tidal and velocity shear fields. We focus on the alignment
of their shape, angular momentum and peculiar velocities. We use a cosmological
N-body simulation that allows to study dark matter halos spanning almost five
orders of magnitude in mass ($10^{9}$-$10^{14}$) $h^{-1}$$M_{\odot}$ and
spatial scales of $(0.5$-$1.0)$ $h^{-1}$ Mpc to define the cosmic web. We find
that the halo shape presents the strongest alignment along the smallest tidal
eigenvector, e.g. along filaments and walls, with a signal that gets stronger
as the halo mass increases. In the case of the velocity shear field only
massive halos $>10^{12}$ $h^{-1}$$M_{\odot}$ tend to have their shapes aligned
along the largest tidal eigenvector; that is, perpendicular to filaments and
walls. For the angular momentum we find alignment signals only for halos more
massive than $10^{12}$ $h^{-1}$$M_{\odot}$ both in the tidal and velocity shear
webs where the preferences are for it to be parallel to the middle eigenvector;
perpendicular to filaments and parallel to walls. Finally, the peculiar
velocities show a strong alignment along the smallest tidal eigenvector for all
halo masses; halos move along filaments and walls. In the velocity shear the
same alignment is present but weaker and only for haloes less massive than
$10^{12}$ $h^{-1}$$M_{\odot}$. Our results clearly show that the two different
algorithms we used to define the cosmic web describe different physical aspects
of non-linear collapse and should be used in a complementary way to understand
the effect of the cosmic web on galaxy evolution. | Observational constraints on the progenitor metallicities of
core-collapse supernovae: We present constraints on the progenitor metallicities of core-collapse
supernovae. To date, nearly all metallicity constraints have been inferred from
indirect methods such as metallicity gradients in host galaxies, luminosities
of host galaxies, or derived global galaxy metallicities. Here, progenitor
metallicities are derived from optical spectra taken at the sites of nearby
supernovae, from the ratio of strong emission lines found in their host HII
regions.We present results from the spectra of 74 host HII regions and discuss
the implications that these have on the nature of core-collapse supernova
progenitors. Overall, while we find that the mean metallicity of type Ibc
environments is higher than that of type II events, this difference is smaller
than observed in previous studies. There is only a 0.06 dex difference in the
mean metallicity values, at a statistical significance of ~1.5 sigma, while
using a KS-test we find that the two metallicity distributions are marginally
consistent with being drawn from the same parent population (probability >10%).
This argues that progenitor metallicity is not a dominant parameter in deciding
supernovae type, with progenitor mass and/or binarity playing a much more
significant role. |
Systematic Problems With Using Dark Matter Simulations to Model Stellar
Halos: The limits of available computing power have forced models for the structure
of stellar halos to adopt one or both of the following simplifying assumptions:
(1) stellar mass can be "painted" onto dark matter particles in progenitor
satellites; (2) pure dark matter simulations that do not form a luminous galaxy
can be used. We estimate the magnitude of the systematic errors introduced by
these assumptions using a controlled set of stellar halo models where we
independently vary whether we look at star particles or painted dark matter
particles, and whether we use a simulation in which a baryonic disk galaxy
forms or a matching pure dark matter simulation that does not form a baryonic
disk. We find that the "painting" simplification reduces the halo concentration
and internal structure, predominantly because painted dark matter particles
have different kinematics than star particles even when both are buried deep in
the potential well of the satellite. The simplification of using pure dark
matter simulations reduces the concentration further, but increases the
internal structure, and results in a more prolate stellar halo. These
differences can be a factor of 1.5-7 in concentration (as measured by the
half-mass radius) and 2-7 in internal density structure. Given this level of
systematic uncertainty, one should be wary of overinterpreting differences
between observations and the current generation of stellar halo models based on
dark matter only simulations when such differences are less than an order of
magnitude. | The distribution of dark matter and gas spanning six megaparsecs around
the post-merger galaxy cluster MS0451-03: Using the largest mosaic of Hubble Space Telescope images around a galaxy
cluster, we map the distribution of dark matter throughout a $\sim$$6\times6$
Mpc$^2$ area centred on the cluster MS 0451-03 ($z=0.54$,
$M_{200}=1.65\times10^{15} \rm{M}_\odot$). Our joint strong- and weak-lensing
analysis shows three possible filaments extending from the cluster,
encompassing six group-scale substructures. The dark-matter distribution in the
cluster core is elongated, consists of two distinct components, and is
characterized by a concentration parameter of $c_{200}=3.79\pm0.36$. By
contrast, XMM-Newton observations show the gas distribution to be more
spherical, with excess entropy near the core, and a lower concentration of
$c_{200}=2.35^{+0.89}_{-0.70}$ (assuming hydrostatic equilibrium). Such a
configuration is predicted in simulations of major mergers 2-7Gyr after the
first core passage, when the two dark-matter halos approach second turnaround,
and before their gas has relaxed. This post-merger scenario finds further
support in optical spectroscopy of the cluster's member galaxies, which shows
that star formation was abruptly quenched 5 Gyr ago. MS 0451-03 will be an
ideal target for future studies of the growth of structure along filaments,
star-formation processes after a major merger, and the late-stage evolution of
cluster collisions. |
Ending inflation with a bang: Higgs vacuum decay in $R^2$ gravity: According to the current experimental data, the Higgs vacuum appears to be
metastable due to the development of a second lower ground state in its
potential. Consequently, vacuum decay would induce the nucleation of true
vacuum bubbles with catastrophic consequences for our Universe and therefore we
are motivated to study possible stabilising mechanisms in the early universe.
In our latest investigation (2207.00696), we studied the electroweak
metastability in the context of the observationally favoured model of
Starobinsky inflation. Following the motivation and techniques from our first
study (2011.037633), we obtained constraints on the Higgs curvature coupling
$\xi$, while embedding the SM on the modified gravity scenario $R+R^2$, which
introduces Starobinsky inflation naturally. This had significant repercussions
for the effective Higgs potential in the form of additional negative terms that
destabilize the false vacuum. Another important aspect lay in the definition
for the end of inflation, as bubble nucleation is most prominent during its
very last moments. Our results dictated that these stronger lower $\xi$-bounds
are very sensitive to the final moments of inflation, where spacetime deviates
increasingly from de Sitter. | An alternative validation strategy for the Planck cluster catalog and
$y$-distortion maps: We present an all sky map of the $y$-type distortion calculated from the full
mission Planck HFI (High Frequency Instrument) data using the recently proposed
approach to component separation based on parametric model fitting and model
selection. This simple model selection approach allows us to distinguish
between carbon monoxide (CO) line emission and $y$-type distortion, something
that is not possible using the internal linear combination based methods. We
create a mask to cover the regions of significant CO emission relying on the
information in the $\chi^2$ map obtained when fitting for the $y$-distortion
and CO emission to the lowest four HFI channels. We revisit the second Planck
cluster catalog and try to quantify the quality of the cluster candidates in an
approach that is similar in spirit to Aghanim et al. (2014). We find that at
least $93\%$ of the clusters in the cosmology sample are free of CO
contamination. We also find that $59\%$ of unconfirmed candidates may have
significant contamination from molecular clouds. We agree with Planck
collaboration (2015) for the worst offenders. We suggest an alternative
validation strategy of measuring and subtracting the CO emission from the
Planck cluster candidates using radio telescopes thus improving the reliability
of the catalog. Our CO mask and annotations to the Planck cluster catalog
identifying cluster candidates with possible CO contamination are made publicly
available. |
Mid-Infrared Spectroscopy of Two Lensed Star-forming Galaxies: We present low-resolution, rest-frame ~ 5 - 12 micron Spitzer/IRS spectra of
two lensed z ~ 2 UV-bright star-forming galaxies, SDSS J120602.09+514229.5 and
SDSS J090122.37+181432.3. Using the magnification boost from lensing, we are
able to study the physical properties of these objects in greater detail than
is possible for unlensed systems. In both targets, we detect strong PAH
emission at 6.2, 7.7, and 11.3 microns, indicating the presence of vigorous
star formation. For J1206, we find a steeply rising continuum and significant
[S IV] emission, suggesting that a moderately hard radiation field is powering
continuum emission from small dust grains. The strength of the [S IV] emission
also implies a sub-solar metallicity of ~ 0.5 Z_{Sun}, confirming published
rest-frame optical measurements. In J0901, the PAH lines have large rest-frame
equivalent widths (> 1 micron) and the continuum rises slowly with wavelength,
suggesting that any AGN contribution to L_{IR} is insignificant, in contrast to
the implications of optical emission-line diagnostics. Using [O III] line flux
as a proxy for AGN strength, we estimate that the AGN in J0901 provides only a
small fraction of its mid-infrared continuum flux. By combining the detection
of [Ar II] with an upper limit on [Ar III] emission, we infer a metallicity of
> 1.3 Z_{Sun}. This work highlights the importance of combining rest-frame
optical and mid-IR spectroscopy in order to understand the detailed properties
of star-forming galaxies at high redshift. | The clustering of galaxies in the SDSS-III Baryon Oscillation
Spectroscopic Survey: Measuring D_A and H at z=0.57 from the Baryon Acoustic
Peak in the Data Release 9 Spectroscopic Galaxy Sample: We present measurements of the angular diameter distance to and Hubble
parameter at z=0.57 from the measurement of the baryon acoustic peak in the
correlation of galaxies from the Sloan Digital Sky Survey III Baryon
Oscillation Spectroscopic Survey. Our analysis is based on a sample from Data
Release 9 of 264,283 galaxies over 3275 square degrees in the redshift range
0.43<z<0.70. We use two different methods to provide robust measurement of the
acoustic peak position across and along the line of sight in order to measure
the cosmological distance scale. We find D_A(0.57) = 1408 +/- 45 Mpc and
H(0.57) = 92.9 +/- 7.8 km/s/Mpc for our fiducial value of the sound horizon.
These results from the anisotropic fitting are fully consistent with the
analysis of the spherically averaged acoustic peak position presented in
Anderson et al, 2012. Our distance measurements are a close match to the
predictions of the standard cosmological model featuring a cosmological
constant and zero spatial curvature. |
Probing the Weak Gravity Conjecture in the Cosmic Microwave Background: The weak gravity conjecture imposes severe constraints on natural inflation.
A trans-Planckian axion decay constant can only be realized if the potential
exhibits an additional (subdominant) modulation with sub-Planckian periodicity.
The resulting wiggles in the axion potential generate a characteristic
modulation in the scalar power spectrum of inflation which is logarithmic in
the angular scale. The compatibility of this modulation is tested against the
most recent Cosmic Microwave Background (CMB) data by Planck and BICEP/Keck.
Intriguingly, we find that the modulation completely resolves the tension of
natural inflation with the CMB. A Bayesian model comparison reveals that
natural inflation with modulations describes all existing data equally well as
the cosmological standard model $\Lambda$CDM. In addition, the bound of a
tensor-to-scalar ratio r > 0.002 correlated with a striking small-scale
suppression of the scalar power spectrum occurs. Future CMB experiments could
directly probe the modulation through their improved sensitivity to smaller
angular scales and possibly the measurement of spectral distortions. They
could, thus, verify a key prediction of the weak gravity conjecture and provide
dramatic new insights into the theory of quantum gravity. | Escape of Lyman continuum radiation from local galaxies - Detection of
leakage from the young starburst Tol 1247-232: The escape fraction of hydrogen ionizing photons (f_esc) from galaxies has
been suggested to be evolving with time, but the picture is far from clear.
While evidence for significant escape fractions has been found at high
redshifts in several studies, the picture looks different in the more nearby
universe. Here, we apply a new background subtraction routine on archival data
from the Far Ultraviolet Spectroscopic Explorer (FUSE), in order to study local
galaxies in search for possible Lyman Continuum (LyC) leakage. In the process,
for the first time a stacked spectrum in the LyC is produced for local
galaxies. With this small sample, we also make a more tentative approach to
look for possible correlations between f_esc and physical parameters such as
internal absorption E(B-V)_i, mass, H I mass, specific star formation rate
(SSFR), metallicity, and Ly-alpha emission. Eight star forming galaxies with
redshifts z > 0.015 from the FUSE archive were re-examined. Also, a sub-sample
of an additional four galaxies with lower redshifts were included, for which
the escape fraction was estimated from residual flux in the low ionization
interstellar C II(1036{\AA}) line. Out of the eight galaxies, only one was
found to have significant LyC leakage, Tol 1247-232 (S/N=5.2). This is the
second detection of a leaking galaxy in the local universe. We find an absolute
escape fraction for Tol 1247-232 of f_esc = 2.4(+0.9/-0.8) %. The stacked
sample show an excess in the LyC with f_esc = 1.4(+0.6/-0.5) %, but we note
that there might be important selection biases involved. With the small sample,
we suggest a possible trend for higher f_esc with lower mass and with enhanced
SSFR. None of the galaxies with high values of E(B-V)_i were found to show any
sign of leakage. |
An update on adiabatic modes in cosmology and $δ$N formalism: In this paper, we generalize the Weinberg's procedure to determine the
comoving curvature perturbation $\cal R$ to non-attractor inflationary regimes.
We show that both modes of $\cal R$ are related to a symmetry of the
perturbative equations in the Newtonian gauge. As a byproduct, we clarify that
adiabaticity does not generally imply constancy of $\cal R$, not even in the
$k\rightarrow 0$ limit. We then show that there exist non-equivalent
definitions of $\delta N$ that would reproduce $\mathcal{R}$ or the uniform
density curvature perturbation $\zeta$ at linear order. We have then shown that
the perturbative $\delta N$ definition in terms of difference between the
number of e-foldings of different gauges, can be extended non-perturbatively at
leading order in gradient expansion. Nevertheless, the computer friendly
definition in terms of the difference of e-foldings obtained from the evolution
of a local FRW Universe, respectively with perturbed and un-perturbed initial
conditions, might only give information about the linear order curvature
perturbations, contrary to what stated in the literature. | STRIDES: Automated uniform models for 30 quadruply imaged quasars: Gravitational time delays provide a powerful one step measurement of $H_0$,
independent of all other probes. One key ingredient in time delay cosmography
are high accuracy lens models. Those are currently expensive to obtain, both,
in terms of computing and investigator time (10$^{5-6}$ CPU hours and $\sim$
0.5-1 year, respectively). Major improvements in modeling speed are therefore
necessary to exploit the large number of lenses that are forecast to be
discovered over the current decade. In order to bypass this roadblock, building
on the work by Shajib et al. (2019), we develop an automated modeling pipeline
and apply it to a sample of 30 quadruply imaged quasars and one lensed compact
galaxy, observed by the Hubble Space Telescope in multiple bands. Our automated
pipeline can derive models for 30/31 lenses with few hours of human time and
<100 CPU hours of computing time for a typical system. For each lens, we
provide measurements of key parameters and predictions of magnification as well
as time delays for the multiple images. We characterize the
cosmography-readiness of our models using the stability of differences in
Fermat potential (proportional to time delay) w.r.t. modeling choices. We find
that for 10/30 lenses our models are cosmography or nearly cosmography grade
(<3% and 3-5% variations). For 6/30 lenses the models are close to cosmography
grade (5-10%). These results are based on informative priors and will need to
be confirmed by further analysis. However, they are also likely to improve by
extending the pipeline modeling sequence and options. In conclusion, we show
that uniform cosmography grade modeling of large strong lens samples is within
reach. |
Direct Measurements of the magnification produced by galaxy clusters as
gravitational lenses: Weak lensing is one of the best available diagnostic tools to measure the
total density profiles of distant clusters of galaxies. Unfortunately, it
suffers from the well-known mass-sheet degeneracy, so that weak lensing
analyses cannot lead to fully reliable determinations of the total mass of the
clusters. One possible way to set the relevant scale of the density profile
would be to make a direct measurement of the magnification produced by the
clusters as gravitational lenses. In this paper we revisit a suggestion made a
few years ago for this general purpose, based on the use of the Fundamental
Plane as a standard rod for early-type galaxies. Here we move one step further,
beyond the simple outline of the idea given earlier, and quantify some
statistical properties of this innovative diagnostic tool, with the final goal
of identifying clear guidelines for a future observational test on concrete
cases, which turns out to be well within the current instrument capabilities.
The study is carried out by discussing the statistical properties of
Fundamental Plane measurements for a sample of early-type source galaxies
behind a massive cluster, for which a weak lensing analysis is assumed to be
available. We proceed to study the best strategy to use Fundamental Plane
measurements to determine the mass scale of a given cluster and find that the
optimal choice is that of a sample of early-type galaxies behind the cluster
distributed approximately uniformly in the sky. We also show that substructures
do not contribute much to the magnification signal that we are looking for, but
only add a modest amount of scatter. We find that for a massive cluster (M >
10^15 M_Sun) located at redshift 0.3 +/- 0.1, a set of about 20 Fundamental
Plane measurements, combined with a good weak lensing analysis, should be able
to lead to a mass determination with a precision of 20% or better. | On the universality of density profiles: We use the secondary infall model described in Del Popolo (2009), which takes
into account the effect of dynamical friction, ordered and random angular
momentum, baryons adiabatic contraction and dark matter baryons interplay, to
study how in- ner slopes of relaxed LCDM dark matter (DM) halos with and
without baryons (baryons+DM, and pure DM) depend on redshift and on halo mass.
We apply the quoted method to structures on galactic scales and clusters of
galaxies scales. We find that the inner logarithmic density slope, of dark
matter halos with baryons has a significant dependence on halo mass and
redshift with slopes ranging from 0 for dwarf galaxies to 0.4 for objects of M
= 10^13M_solar and 0.94 for M = 10^15M_solar clusters of galaxies. Structures
slopes increase with increasing redshift and this trend reduces going from
galaxies to clusters. In the case of density profiles constituted just of dark
matter the mass and redshift dependence of slope is very slight. In this last
case, we used the Merrit et al. (2006) analysis who compared N-body density
profiles with various parametric models finding systematic variation in profile
shape with halo mass. This last analysis suggests that the galaxy-sized halos
obtained with our model have a different shape parameter, i.e. a different mass
distribution, than the cluster-sized halos, obtained with the same model. The
results of the present paper argue against universality of density profiles
constituted by dark matter and baryons and confirm claims of a systematic
variation in profile shape with halo mass, for dark matter halos. |
The age problem in $Λ$CDM model: The age problem in the $\Lambda$CDM model is re-examined. We define the
elapsed time $T$ of an object is its age plus the age of the Universe when it
was born. Therefore in any cosmology, $T$ must be smaller than the age of the
Universe. For the old quasar APM 08279+5255 at $z=3.91$, previous studies have
determined the best-fit value of $T$, 1 $\sigma$ lower limit and the lowest
limit to $T$ are 2.3, 2.0 and 1.7 Gyr, respectively. Constrained from
SNIa$+R+A+d$, SNIa$+R+A+d+H(z)$, and WMAP5+2dF+SNLS+HST+BBN, the $\Lambda$CDM
model can only accommodate $T(z=3.91)=1.7$ Gyr at 1 $\sigma$ deviation.
Constrained from WMAP5 results only, the $\Lambda$CDM model can only
accommodate $T(z=3.91)=1.7$ Gyr at 2 $\sigma$ deviation. In all these cases, we
found that $\Lambda$CDM model accommodates the total age (14 Gyr for $z=0$) of
the Universe estimated from old globular clusters, but cannot accommodate
statistically the 1 $\sigma$ lower limit to the best-fit age of APM~08279+5255
at $z=3.91$. These results imply that the $\Lambda$CDM model may suffer from an
age problem. | Probing below the neutrino floor with the first generation of stars: We show that the mere observation of the first stars (Pop III stars) in the
universe can be used to place tight constraints on the strength of the
interaction between dark matter and regular, baryonic matter. We apply this
technique to a candidate Pop III stellar complex discovered with the Hubble
Space Telescope at $z \sim 7$ and find bounds that are competitive with, or
even stronger than, current direct detection experiments, such as XENON1T, for
dark matter particles with mass ($m_X$) larger than about $100$ GeV. We also
show that the discovery of sufficiently massive Pop III stars could be used to
bypass the main limitations of direct detection experiments: the neutrino
background to which they will be soon sensitive. |
Sensitivity of the Hubble Constant Determination to Cepheid Calibration: Motivated by the large observed diversity in the properties of extra-galactic
extinction by dust, we re-analyse the Cepheid calibration used to infer the
Hubble constant, $H_0$, from Type Ia supernovae, using Cepheid data in 19 Type
Ia supernova host galaxies from Riess et al (2016) and anchor data from Riess
et al (2016, 2019, 2021). Unlike the SH0ES team, we do not enforce a fixed
universal color-luminosity relation to correct the Cepheid magnitudes. Instead,
we focus on a data driven method, where the optical colors and near infrared
magnitudes of the Cepheids are used to derive individual color-luminosity
relations for each Type Ia supernova host and anchor galaxy. We present two
different analyses, one based on Wesenheit magnitudes resulting in $H_0=73.2\pm
1.3$ km/s/Mpc, a $4.2\,\sigma$ tension with the value inferred from the cosmic
microwave background. In the second approach, we calibrate an individual
extinction law for each galaxy with non-informative priors using color
excesses, yielding $H_0=73.9\pm 1.8$ km/s/Mpc, in $3.4\,\sigma$ tension with
the Planck value.
Although the two methods yield similar results, in the latter approach the
Hubble constant inferred from the individual Cepheid absolute distance
calibrator galaxies range from $H_0=68.1\pm 3.5$ km/s/Mpc to $H_0=76.7\pm 2.0$
km/s/Mpc. Taking the correlated nature of $H_0$ inferred from individual
anchors into account and allowing for individual extinction laws, the Milky Way
anchor is in $2.1\,\sigma - 3.1\,\sigma$ tension with the NGC 4258 and the
Large Magellanic Cloud anchors, depending on prior assumptions regarding the
color-luminosity relations and the method used for quantifying the tension. | A model with two periods of inflation: A scenario with two subsequent periods of inflationary expansion in the very
early universe is examined. The model is based on a potential motivated by
symmetries being found in field theory at high energy. For various parameter
sets of the potential the spectra of scalar and tensor perturbations that are
expected to originate from this scenario are calculated. Also the beginning of
the reheating epoch connecting the second inflation with thermal equilibrium is
studied. Perturbations with wavelengths leaving the horizon around the
transition between the two inflations are special: It is demonstrated that the
power spectrum at such scales deviates significantly from expectations based on
measurements of the cosmic microwave background (CMB). This supports the
conclusion that parameters for which this part of the spectrum leaves
observable traces in the CMB must be excluded. Parameters entailing a very
efficient second inflation correspond to standard small-field inflation and can
meet observational constraints. Particular attention is paid to the case where
the second inflation leads solely to a shift of the observable spectrum from
the first inflation. A viable scenario requires this shift to be small. |
EFTofLSS meets simulation-based inference: $σ_8$ from biased
tracers: Cosmological inferences typically rely on explicit expressions for the
likelihood and covariance of the data vector, which normally consists of a set
of summary statistics. However, in the case of nonlinear large-scale structure,
exact expressions for either likelihood or covariance are unknown, and even
approximate expressions can become very cumbersome, depending on the scales and
summary statistics considered. Simulation-based inference (SBI), in contrast,
does not require an explicit form for the likelihood but only a prior and a
simulator, thereby naturally circumventing these issues. In this paper, we
explore how this technique can be used to infer $\sigma_8$ from a Lagrangian
effective field theory (EFT) based forward model for biased tracers. The power
spectrum and bispectrum are used as summary statistics to obtain the posterior
of the cosmological, bias and noise parameters via neural density estimation.
We compare full simulation-based inference with cases where the data vector is
drawn from a Gaussian likelihood with sample and analytical covariances. We
conclude that, for $k_{\text{max}}=0.1h\text{Mpc}^{-1}$ and
$0.2h\text{Mpc}^{-1}$, the form of the covariance is more important than the
non-Gaussianity of the likelihood, although this conclusion is expected to
depend on the cosmological parameter inferred, the summary statistics
considered and range of scales probed. | Probing Large-Angle Correlations with the Microwave Background
Temperature and Lensing Cross Correlation: A lack of correlations in the microwave background temperature between sky
directions separated by angles larger than 60 degrees has recently been
confirmed by data from the Planck satellite. This feature arises as a random
occurrence within the standard LCDM cosmological model less than 0.3 per cent
of the time, but so far no other compelling theory to explain this observation
has been proposed. Here we investigate the theoretical cross-correlation
function between microwave background temperature and the gravitational lensing
potential of the microwave background, which in contrast to the temperature
correlation function depends strongly on gravitational potential fluctuations
interior to our Hubble volume. For standard LCDM cosmology, we generate random
sky realizations of the microwave temperature and gravitational lensing,
subject to the constraint that the temperature correlation function matches
observations, and compare with random skies lacking this constraint. The
distribution of large-angle temperature-lensing correlation functions in these
two cases is different, and the two cases can be clearly distinguished in
around 40 per cent of model realizations. We present an a priori procedure for
using similar large-angle correlations between other types of data, to
determine whether the lack of large-angle correlations is a statistical fluke
or points to a shortcoming of the standard cosmological model. |
Cosmological simulations of self-interacting Bose-Einstein condensate
dark matter: Fully 3D cosmological simulations of scalar field dark matter with
self-interactions, also known as Bose-Einstein condensate dark matter, are
performed using a set of effective hydrodynamic equations. These are derived
from the non-linear Schr\"odinger equation by performing a smoothing operation
over scales larger than the de Broglie wavelength, but smaller than the
self-interaction Jeans' length. The dynamics on the de Broglie scale become an
effective thermal energy in the hydrodynamic approximation, which is assumed to
be subdominant in the initial conditions, but become important as structures
collapse and the fluid is shock-heated. The halos that form have
Navarro-Frenk-White envelopes, while the centers become cored due to the fluid
pressures (thermal + self-interaction). The core radii are mostly determined by
the self-interaction Jeans' length, even though the effective thermal energy
eventually dominates over the self-interaction energy everywhere, a result that
is insensitive to the initial smallness of the thermal energy. Scaling
relations for the simulated population of halos are compared with Milky Way
dwarf spheroidals and nearby galaxies, assuming a Burkert halo profile, and are
found to not match, also for core radii $R_c\approx 1\text{kpc}$, which has
generally been the value expected to resolve the cusp-core issue. However, the
simulations have a limited volume, and therefore a limited halo mass range,
include no baryonic physics, and use fiducial cold dark matter initial
conditions with a cut-off near the Jeans' length at $z=50$, all of which can
affect the halo properties. [Abridged] | Probing the gravitational wave background from cosmic strings with LISA: Cosmic string networks offer one of the best prospects for detection of
cosmological gravitational waves (GWs). The combined incoherent GW emission of
a large number of string loops leads to a stochastic GW background (SGWB),
which encodes the properties of the string network. In this paper we analyze
the ability of the Laser Interferometer Space Antenna (LISA) to measure this
background, considering leading models of the string networks. We find that
LISA will be able to probe cosmic strings with tensions $G\mu \gtrsim
\mathcal{O}(10^{-17})$, improving by about $6$ orders of magnitude current
pulsar timing arrays (PTA) constraints, and potentially $3$ orders of magnitude
with respect to expected constraints from next generation PTA observatories. We
include in our analysis possible modifications of the SGWB spectrum due to
different hypotheses regarding cosmic history and the underlying physics of the
string network. These include possible modifications in the SGWB spectrum due
to changes in the number of relativistic degrees of freedom in the early
Universe, the presence of a non-standard equation of state before the onset of
radiation domination, or changes to the network dynamics due to a string
inter-commutation probability less than unity. In the event of a detection,
LISA's frequency band is well-positioned to probe such cosmic events. Our
results constitute a thorough exploration of the cosmic string science that
will be accessible to LISA. |
X-Ray Studies of the Abell 3158 Galaxy Cluster with eROSITA: The most nearby clusters are the best places to study physical and enrichment
effects in the faint cluster outskirts. A3158 located at z=0.059 is quite
extended with a characteristic radius r$_{200}$=23.95 arcmin. In 2019, A3158
was observed as a calibration target in a pointed observation with the eROSITA
telescope onboard the SRG mission.
We determined 1d temperature, abundance and normalisation profiles from
eROSITA and XMM-Newton and Chandra data as well as 2d maps of temperature
distribution from eROSITA data. The velocity dispersion was determined and the
cluster mass was calculated.
The overall temperature was measured to be 4.725$\pm$ 0.035 keV. The profiles
of eROSITA all agree on a ~10% level with those determined with XMM-Newton and
Chandra data. From the temperature map we see that the cluster lacks a cool
core, as noted before. The presence of a previously detected off-centre cool
clump West of the central cluster region is observed. Furthermore there is a
bow shaped edge near the location of the cool gas clump West of the cluster
centre. An extension of gas is detected for the first time further out in the
West. The velocity dispersion of the cluster was measured to be 1058$\pm$41 km
s$^{-1}$. The total mass was determined as $M_{200}$=1.38$\pm$ 0.25x10$^{15}$
$M_{\odot}$. The mass estimate from the M-T relation is significantly lower at
M$_{200}$=5.09$\pm$ 0.59x10$^{14}M_{\odot}$. An extended X-ray source located
South of the cluster also coincides with a galaxy overdensity with redshifts in
the range 0.05<z<0.07. These are indications that the cluster may be undergoing
merger activity. Another extended source located North of the cluster is
detected in X-rays and coincides with an overdensity of galaxies with redshifts
in the range of 0.070<z<0.077. This is likely a background cluster not related
to A3158. Additionally a known SPT cluster at z=0.53 was detected. | Unavoidable CMB spectral features and blackbody photosphere of our
Universe: Spectral features in the CMB energy spectrum contain a wealth of information
about the physical processes in the early Universe, z < 2 x 10^6. The CMB
spectral distortions are complementary to all other probes of cosmology. In
fact, most of the information contained in the CMB spectrum is inaccessible by
any other means. This review outlines the main physics behind the spectral
features in the CMB throughout the history of the Universe, concentrating on
the distortions which are inevitable and must be present at a level observable
by the next generation of proposed CMB experiments. The spectral distortions
considered here include spectral features from cosmological recombination,
resonant scattering of CMB by metals during reionization which allows us to
measure their abundances, y-type distortions during and after reionization and
\mu-type and i-type (intermediate between \mu and y) distortions created at
redshifts z > 1.5 x 10^4. |
Thinking Outside the Box: Effects of Modes Larger than the Survey on
Matter Power Spectrum Covariance: Considering the matter power spectrum covariance matrix, it has recently been
found that there is a potentially dominant effect on mildly non-linear scales
due to power in modes of size equal to and larger than the survey volume. This
{\it beat coupling} effect has been derived analytically in perturbation theory
and while it has been tested with simulations, some questions remain
unanswered. Moreover, there is an additional effect of these large modes, which
has so far not been included in analytic studies, namely the effect on the
estimated {\it average} density which enters the power spectrum estimate. In
this article, we work out analytic, perturbation theory based expressions
including both the beat coupling and this {\it local average effect} and we
show that while, when isolated, beat coupling indeed causes large excess
covariance in agreement with the literature, in a realistic scenario this is
compensated almost entirely by the local average effect, leaving only $\sim 10
%$ of the excess. We test our analytic expressions by comparison to a suite of
large N-body simulations. For the variances, we find excellent agreement with
the analytic expressions for $k < 0.2 h$Mpc$^{-1}$ at $z=0.5$, while the
correlation coefficients agree to beyond $k=0.4 h$Mpc$^{-1}$. As expected, the
range of agreement increases towards higher redshift and decreases slightly
towards $z=0$. We finish by including the large-mode effects in a full
covariance matrix description for arbitrary survey geometry and confirming its
validity using simulations. This may be useful as a stepping stone towards
building an actual galaxy (or other tracer's) power spectrum covariance matrix.
[abridged] | ARCADE 2 Measurement of the Extra-Galactic Sky Temperature at 3-90 GHz: The ARCADE 2 instrument has measured the absolute temperature of the sky at
frequencies 3, 8, 10, 30, and 90 GHz, using an open-aperture cryogenic
instrument observing at balloon altitudes with no emissive windows between the
beam-forming optics and the sky. An external blackbody calibrator provides an
{\it in situ} reference. Systematic errors were greatly reduced by using
differential radiometers and cooling all critical components to physical
temperatures approximating the CMB temperature. A linear model is used to
compare the output of each radiometer to a set of thermometers on the
instrument. Small corrections are made for the residual emission from the
flight train, balloon, atmosphere, and foreground Galactic emission. The ARCADE
2 data alone show an extragalactic rise of $50\pm7$ mK at 3.3 GHz in addition
to a CMB temperature of $2.730\pm .004$ K. Combining the ARCADE 2 data with
data from the literature shows a background power law spectrum of $T=1.26\pm
0.09$ [K] $(\nu/\nu_0)^{-2.60\pm 0.04}$ from 22 MHz to 10 GHz ($\nu_0=1$ GHz)
in addition to a CMB temperature of $2.725\pm .001$ K. |
Shot noise and reconstruction of the acoustic peak: We study the effect of noise in the density field, such as would arise from a
finite number density of tracers, on reconstruction of the acoustic peak within
the context of Lagrangian perturbation theory. Reconstruction performs better
when the density field is determined from denser tracers, but the gains
saturate at n~1e-4(h/Mpc)^3. For low density tracers it is best to use a large
smoothing scale to define the shifts, but the optimum is very broad. | Cosmological evolution of orientations of cluster-sized dark matter
haloes and their central galaxies in the Horizon-AGN simulation: It is known observationally that the major axes of galaxy clusters and their
brightest cluster galaxies are roughly aligned with each other. To understand
the origin of the alignment, we identify 40 cluster-sized dark matter (DM)
haloes with masses higher than $5\times10^{13}~M_{\odot}$ and their central
galaxies (CGs) at $z\approx 0$ in the Horizon-AGN cosmological hydrodynamical
simulation. We trace the progenitors at 50 different epochs between $0<z<5$. We
then fit their shapes and orientations with a triaxial ellipsoid model. While
the orientations of both DM haloes and CGs change significantly due to repeated
mergers and mass accretions, their relative orientations are well aligned at
each epoch even at high redshifts, $z>1$. The alignment becomes tighter with
cosmic time; the major axes of the CGs and their host DM haloes at present are
aligned on average within $\sim 30^{\circ}$ in the three dimensional space and
$\sim 20^{\circ}$ in the projected plane. The orientations of the major axes of
DM haloes on average follow one of the eigen-vectors of the surrounding tidal
field that corresponds to the {\it slowest collapsing} (or even stretching)
mode, and the alignment with the tidal field also becomes tighter. This implies
that the orientations of CGs and DM haloes at the present epoch are largely
imprinted in the primordial density field of the Universe, whereas strong
dynamical interactions such as mergers are important to explain their mutual
alignment at each epoch. |
Exploring the cosmic dawn and epoch of reionization with 21cm line: The dark age of the universe, when no luminous object had existed, ended with
the birth of the first stars, galaxies, and blackholes. This epoch is called
cosmic dawn. Cosmic reionization is the major transition of the intergalactic
medium (IGM) in the universe driven by ionizing photons emitted from luminous
objects. Although the epoch through the dark age to reionization is a milestone
in the universe, our knowledge of this epoch has not been sufficient yet.
Cosmic 21cm signal, which is emitted from neutral hydrogen, is expected to open
a new window for this epoch. In this review paper, we first introduce the basic
physics of the 21cm line and how first stars impact on the 21cm line signal.
Next, we briefly summarize how we extract astrophysical information from the
21cm line signal by means of statistical and machine learning approaches. We
also discuss the synergy between the 21cm line signal and other emission lines.
Finally, we summarize the current status of 21cm experiments. | Dark Photon Oscillations in Our Inhomogeneous Universe: A dark photon may kinetically mix with the ordinary photon, inducing
oscillations with observable imprints on cosmology. Oscillations are resonantly
enhanced if the dark photon mass equals the ordinary photon plasma mass, which
tracks the free electron number density. Previous studies have assumed a
homogeneous Universe; in this Letter, we introduce for the first time an
analytic formalism for treating resonant oscillations in the presence of
inhomogeneities of the photon plasma mass. We apply our formalism to determine
constraints from Cosmic Microwave Background photons oscillating into dark
photons, and from heating of the primordial plasma due to dark photon dark
matter converting into low-energy photons. Including the effect of
inhomogeneities demonstrates that prior homogeneous constraints are not
conservative, and simultaneously extends current experimental limits into a
vast new parameter space. |
Critical constraint on inflationary magnetogenesis: Recently, there are several reports that the cosmic magnetic fields on Mpc
scale in void region is larger than $\sim 10^{-15}$G with an uncertainty of a
few orders from the current blazar observations. On the other hand, in
inflationary magnetogenesis models, additional primordial curvature
perturbations are inevitably produced from iso-curvature perturbations due to
generated electromagnetic fields. We explore such induced curvature
perturbations in a model independent way and obtained a severe upper bound for
the energy scale of inflation from the observed cosmic magnetic fields and the
observed amplitude of the curvature perturbation, as $\rho_{\rm inf}^{1/4} <
30{\rm GeV} \times (B_{\rm obs}/10^{-15}{\rm G})^{-1}$ where $B_{\rm obs}$ is
the strength of the magnetic field at present. Therefore, without a dedicated
low energy inflation model or an additional amplification of magnetic fields
after inflation, inflationary magnetogenesis on Mpc scale is generally
incompatible with CMB observations. | The HI-halo mass relation at redshift $z \sim 1$ from the Minkowski
functionals of 21 cm intensity maps: The mean and the scatter of the HI content of a dark-matter halo as a
function of the halo mass are useful statistics that can be used to test models
of structure and galaxy formation. We investigate the possibility of
constraining this HI-halo mass relation (HIHMR) from intensity maps of the
redshifted 21 cm line. In particular, we use the geometry and topology of the
brightness-temperature isocontours in a single frequency channel as quantified
by the Minkowski functionals. First, we generate mock maps from a large N-body
simulation considering the impact of thermal noise and foreground removal. We
then use the Fisher information formalism to forecast constraints on a
parametric model for the HIHMR. We consider a 20,000 deg$^2$ survey (originally
proposed for dark-energy science) conducted with the Square Kilometre Array
Phase 1 (SKA-1) MID observatory operating in single-dish mode. For a channel
bandwidth of 2 MHz, we show that an integration time of a few$\,\times\,10^4$ s
per pointing is sufficient to image the smoothed HI distribution at redshift $z
\simeq 1$ and to measure the HIHMR in a nearly optimal way from the Minkowski
functionals. Tighter constraints on some of the parameters can be obtained by
using also an independent measurement of the mean HI density. Combining the
results from different frequency channels provides exquisite constraints on the
evolution of the HIHMR, especially in the central frequency range of the data
cube. |
Tracing Inflows and Outflows with Absorption Lines in Circumgalactic Gas: We examine how HI and metal absorption lines within low-redshift galaxy halos
trace the dynamical state of circumgalactic gas, using cosmological
hydrodynamic simulations that include a well-vetted heuristic model for
galactic outflows. We categorize inflowing, outflowing, and ambient gas based
on its history and fate as tracked in our simulation. Following our earlier
work showing that the ionisation level of absorbers was a primary factor in
determining the physical conditions of absorbing gas, we show here that it is
also a governing factor for its dynamical state. Low-ionisation metal absorbers
(e.g. MgII) tend to arise in gas that will fall onto galaxies within several
Gyr, while high-ionisation metal absorbers (e.g. OVI) generally trace material
that was deposited by outflows many Gyr ago. Inflowing gas is dominated by
enriched material that was previously ejected in an outflow, hence accretion at
low redshifts is typically substantially enriched. Recycling wind material is
preferentially found closer to galaxies, and is more dominant in lower-mass
halos since high-mass halos have more hot gas that is able to support itself
against infall. Low-mass halos also tend to re-eject more of their accreted
material, owing to our outflow prescription that employs higher mass loading
factors for lower-mass galaxies. Typical HI absorbers trace unenriched ambient
material that is not participating in the baryon cycle, but stronger HI
absorbers arise in cool, enriched inflowing gas. Instantaneous radial velocity
measures of absorbers are generally poor at distinguishing between inflowing
and outflowing gas, except in the case of very recent outflows. These results
suggest that probing halo gas using a range of absorbers can provide detailed
information about the amount and physical conditions of material that is
participating in the baryon cycle. | Dust Obscuration in Lyman Break Galaxies at z~4: Measuring star formation rates (SFRs) in high-z galaxies with their
rest-frame ultraviolet (UV) continuum can be uncertain because of dust
obscuration. Prior studies had used the submillimeter emission at 850 um to
determine the intrinsic SFRs of rest-frame UV selected galaxies, but the
results suffered from the low sensitivity and poor resolution (~15''). Here, we
use ultradeep Very Large Array 1.4 GHz images with ~1''-2'' resolutions to
measure the intrinsic SFRs. We perform stacking analyses in the radio images
centered on ~3500 Lyman break galaxies (LBGs) at z~4 in the Great Observatories
Origins Deep Survey-North and South fields selected with Hubble Space
Telescope/Advanced Camera for Surveys data. The stacked radio flux is very low,
0.08+/-0.15 uJy, implying a mean SFR of 6+/-11 M/yr. This is comparable to the
uncorrected mean UV SFRs of 5 M/yr, implying that the z~4 LBGs have little dust
extinction. The low SFR and dust extinction support the previous results that
z~4 LBGs are in general not submillimeter galaxies. We further show that there
is no statistically significant excess of dust-hidden star-forming components
within ~22 kpc from the LBGs. |
Chandra Observations of a 1.9 kpc Separation Double X-ray Source in a
Candidate Dual AGN Galaxy at z=0.16: We report Chandra observations of a double X-ray source in the z=0.1569
galaxy SDSS J171544.05+600835.7. The galaxy was initially identified as a dual
AGN candidate based on the double-peaked [O III] emission lines, with a
line-of-sight velocity separation of 350 km/s, in its Sloan Digital Sky Survey
spectrum. We used the Kast Spectrograph at Lick Observatory to obtain two
longslit spectra of the galaxy at two different position angles, which reveal
that the two AGN emission components have not only a velocity offset, but also
a projected spatial offset of 1.9 kpc/h70 on the sky. Chandra/ACIS observations
of two X-ray sources with the same spatial offset and orientation as the
optical emission suggest the galaxy most likely contains Compton-thick dual
AGN, although the observations could also be explained by AGN jets. Deeper
X-ray observations that reveal Fe K lines, if present, would distinguish
between the two scenarios. The observations of a double X-ray source in SDSS
J171544.05+600835.7 are a proof of concept for a new, systematic detection
method that selects promising dual AGN candidates from ground-based
spectroscopy that exhibits both velocity and spatial offsets in the AGN
emission features. | Fast motions of galaxies in the Coma I cloud: a case of Dark Attractor?: We notice that nearby galaxies having high negative peculiar velocities are
distributed over the sky very inhomogeneously. A part of this anisotropy is
caused by the "Local Velocity Anomaly", i.e. by the bulk motion of nearby
galaxies away from the Local Void. But a half of the fast-flying objects reside
within a small region RA = [11.5h, 13.0h], Dec. = [+20\circ, +40\circ], known
as the Coma I cloud. According to Makarov & Karachentsev (2011), this complex
contains 8 groups, 5 triplets, 10 pairs and 83 single galaxies with the total
mass of 4.7\star10^13M\odot. We use 122 galaxies in the Coma I region with
known distances and radial velocities VLG < 3000 km/s to draw the Hubble
relation for them. The Hubble diagram shows a Z-shape effect of infall with an
amplitude of +200 km/s on the nearby side and -700 km/s on the back side. This
phenomena can be understood as the galaxy infall towards a dark attractor with
the mass of \sim 2\star10^14M\odot situated at a distance of 15 Mpc from us.
The existence of large void between the Coma and Virgo clusters affects
probably the Hubble flow around the Coma I also. |
New Projections for Dark Matter Searches with Paleo-Detectors: Paleo-detectors are a proposed experimental technique to search for dark
matter (DM). In lieu of the conventional approach of operating a tonne-scale
real-time detector to search for DM-induced nuclear recoils, paleo-detectors
take advantage of small samples of naturally occurring rocks on Earth that have
been deep underground ($\gtrsim 5$ km), accumulating nuclear damage tracks from
recoiling nuclei for $\mathcal{O}(1)$ Gyr. Modern microscopy techniques promise
the capability to read out nuclear damage tracks with nanometer resolution in
macroscopic samples. Thanks to their $\mathcal{O}(1)$ Gyr integration times,
paleo-detectors could constitute nuclear recoil detectors with keV recoil
energy thresholds and 100 kilotonne-yr exposures. This combination would allow
paleo-detectors to probe DM-nucleon cross sections orders of magnitude below
existing upper limits from conventional direct detection experiments. In this
article, we use improved background modeling and a new spectral analysis
technique to update the sensitivity forecast for paleo-detectors. We
demonstrate the robustness of the sensitivity forecast to the (lack of)
ancillary measurements of the age of the samples and the parameters controlling
the backgrounds, systematic mismodeling of the spectral shape of the
backgrounds, and the radiopurity of the mineral samples. Specifically, we
demonstrate that even if the uranium concentration in paleo-detector samples is
$10^{-8}$ (per weight), many orders of magnitude larger than what we expect in
the most radiopure samples obtained from ultra basic rock or marine evaporite
deposits, paleo-detectors could still probe DM-nucleon cross sections below
current limits. For DM masses $\lesssim 10$ GeV/$c^2$, the sensitivity of
paleo-detectors could still reach down all the way to the conventional neutrino
floor in a Xe-based direct detection experiment. | A Halo Occupation Interpretation Of Quasars At $z\sim1.5$ Using Very
Small Scale Clustering Information: We combine the most precise small scale ($< 100\, \rm h^{-1}kpc$) quasar
clustering constraintsto date with recent measurements at large scales ($> 1\,
\rm h^{-1}Mpc$) from the extended Baryon Oscillation Spectroscopic Survey
(eBOSS) to better constrain the satellite fraction of quasars at $z\sim 1.5$ in
the halo occupation formalism. We build our Halo Occupation Distribution (HOD)
framework based on commonly used analytic forms for the one and two-halo terms
with two free parameters: the minimum halo mass that hosts a central quasar and
the fraction of satellite quasars that are within one halo. Inspired by recent
studies that propose a steeper density profile for the dark matter haloes that
host quasars, we explore HOD models at kiloparsec scales and best-fit
parameters for models with $10\times$ higher concentration parameter. We find
that an HOD model with a satellite fraction of $f_{\rm sat} =
0.071_{-0.004}^{+0.009}$ and minimum mass of $\rm M_{m} = 2.31_{-0.38}^{+0.41}
\times 10^{12}\, \, \rm h^{-1} M_{\odot}$ for the host dark matter haloes best
describes quasar clustering (on all scales) at $z \sim 1.5$. Our results are
marginally inconsistent with earlier work that studied brighter quasars,
hinting at a luminosity-dependence to the one-halo term. |
Progress in Measurements of the Gravitational Bending of Radio Waves
Using the VLBA: We have used the Very Long Baseline Array (VLBA) at 43, 23 and 15 GHz to
measure the solar gravitational deflection of radio waves among four radio
sources during an 18-day period in October 2005. Using phase-referenced radio
interferometry to fit the measured phase delay to the propagation equation of
the parameterized post-Newtonian (PPN) formalism, we have determined the
deflection parameter gamma = 0.9998 +/- 0.0003$ (68% confidence level), in
agreement with General Relativity. The results come mainly from 43 GHz
observations where the refraction effects of the solar corona were negligible
beyond 3 degrees from the sun. The purpose of this experiment is three-fold: to
improve on the previous results in the gravitational bending experiments near
the solar limb; to examine and evaluate the accuracy limits of terrestrial VLBI
techniques; and to determine the prospects and outcomes of future experiments.
Our conclusion is that a series of improved designed experiments with the VLBA
could increase the presented accuracy by at least a factor of 4. | A 20 GHz bright sample for δ > +72°: I. Catalogue: During 2010-2011, the Medicina 32-m dish hosted the 7-feed 18-26.5 GHz
receiver built for the Sardinia Radio Telescope, with the goal to perform its
commissioning. This opportunity was exploited to carry out a pilot survey at 20
GHz over the area for {\delta} > + 72.3{\deg}. This paper describes all the
phases of the observations, as they were performed using new hardware and
software facilities. The map-making and source extraction procedures are
illustrated. A customised data reduction tool was used during the follow-up
phase, which produced a list of 73 confirmed sources down to a flux density of
115 mJy. The resulting catalogue, here presented, is complete above 200 mJy.
Source counts are in agreement with those provided by the AT20G survey. This
pilot activity paves the way to a larger project, the K-band Northern Wide
Survey (KNoWS), whose final aim is to survey the whole Northern Hemisphere down
to a flux limit of 50 mJy (5{\sigma}). |
Dissecting the Thermal SZ Power Spectrum by Halo Mass and Redshift in
SPT-SZ Data and Simulations: We explore the relationship between the thermal Sunyaev-Zel'dovich (tSZ)
power spectrum amplitude and the halo mass and redshift of galaxy clusters in
South Pole Telescope (SPT) data, in comparison with three $N$-body simulations
combined with semi-analytical gas models of the intra-cluster medium.
Specifically, we calculate both the raw and fractional power contribution to
the full tSZ power spectrum amplitude at $\ell = 3000$ from clusters as a
function of halo mass and redshift. We use nine mass bins in the range $1
\times 10^{14}\ M_\odot\ h^{-1} < M_{500} < 2 \times 10^{15}\ M_\odot\ h^{-1}$,
and two redshift bins defined by $0.25 < z < 0.59$ and $0.59 < z < 1.5$. We
additionally divide the raw power contribution in each mass bin by the number
of clusters in that bin, as a metric for comparison of different gas models. At
lower masses, the SPT data prefers a model that includes a mass-dependent bound
gas fraction component and relatively high levels of AGN feedback, whereas at
higher masses there is a preference for a model with a lower amount of feedback
and a complete lack of non-thermal pressure support. The former provides the
best fit to the data overall, in regards to all metrics for comparison. Still,
discrepancies exist and the data notably exhibits a steep mass-dependence which
all of the simulations fail to reproduce. This suggests the need for additional
mass- and redshift-dependent adjustments to the gas models of each simulation,
or the potential presence of contamination in the data at halo masses below the
detection threshold of SPT-SZ. Furthermore, the data does not demonstrate
significant redshift evolution in the per-cluster tSZ power spectrum
contribution, in contrast to self-similar model predictions. | Diffuse supernova neutrinos at underground laboratories: I review the physics of the Diffuse Supernova Neutrino flux (or Background,
DSNB), in the context of future searches at the next generation of neutrino
observatories. The theory of the DSNB is discussed in its fundamental elements,
namely the cosmological rate of supernovae, neutrino production inside a core
collapse supernova, redshift, and flavor oscillation effects. The current upper
limits are also reviewed, and results are shown for the rates and energy
distributions of the events expected at future liquid argon and liquid
scintillator detectors of O(10) kt mass, and water Cherenkov detectors up to a
0.5 Mt mass. Perspectives are given on the significance of future observations
of the DSNB, both at the discovery and precision phases, for the investigation
of the physics of supernovae and of the properties of the neutrino. |
Power spectrum of the maxBCG sample: detection of acoustic oscillations
using galaxy clusters: We use the direct Fourier method to calculate the redshift-space power
spectrum of the maxBCG cluster catalog -- currently by far the largest existing
galaxy cluster sample. The total number of clusters used in our analysis is
12,616. After accounting for the radial smearing effect caused by photometric
redshift errors and also introducing a simple treatment for the nonlinear
effects, we show that currently favored low matter density "concordance" LCDM
cosmology provides a very good fit to the estimated power. Thanks to the large
volume (~0.4 h^{-3}Gpc^{3}), high clustering amplitude (linear effective bias
parameter b_{eff} ~3x(0.85/sigma_8)), and sufficiently high sampling density
(~3x10^{-5} h^{3}Mpc^{-3}) the recovered power spectrum has high enough signal
to noise to allow us to find evidence (~2 sigma CL) for the baryonic acoustic
oscillations (BAO). In case the clusters are additionally weighted by their
richness the resulting power spectrum has slightly higher large-scale amplitude
and smaller damping on small scales. As a result the confidence level for the
BAO detection is somewhat increased: ~2.5 sigma. The ability to detect BAO with
relatively small number of clusters is encouraging in the light of several
proposed large cluster surveys. | Measuring our Peculiar Velocity by "Pre-deboosting" the CMB: It was recently shown that our peculiar velocity \beta with respect to the
CMB induces mixing among multipoles and off-diagonal correlations at all scales
which can be used as a measurement of \beta, which is independent of the
standard measurement using the CMB temperature dipole. The proposed techniques
rely however on a perturbative expansion which breaks down for \ell \gtrsim
1/(\beta) \approx 800. Here we propose a technique which consists of deboosting
the CMB temperature in the time-ordered data and show that it extends the
validity of the perturbation analysis multipoles up to \ell \sim 10000. We also
obtain accurate fitting functions for the mixing between multipoles valid in a
full non-linear treatment. Finally we forecast the achievable precision with
which these correlations can be measured in a number of current and future CMB
missions. We show that Planck could measure the velocity with a precision of
around 60 km/s, ACTPol in 4 years around 40 km/s, while proposed future
experiments could further shrink this error bar by over a factor of around 2. |
NGC 4262: a Virgo galaxy with an extended ultraviolet ring: The Galaxy Ultraviolet Explorer (GALEX) satellite has recently shown the
presence of an extended, outer ring studded with UV-bright knots surrounding
the lenticular galaxy NGC 4262. Such a structure---not detected in the
optical---is coupled with a ring of atomic (HI) gas. We want to show that both
star-forming and HI rings surrounding this SB0 galaxy share the same radial
distance from the galaxy center and spatial orientation. We want also to model
the kinematics of the ring(s) and of the galaxy body. We make use of archive
FUV and NUV GALEX data plus HI observations from the literature. We confirm
that the UV-bright and atomic gas rings of NGC 4262 have the same extent and
projected spatial orientation. Their kinematics is not coupled with that of the
galaxy stars. It is possible that NGC 4262 has undergone a major gas stripping
event in the past which gave origin to the present "necklace" of UV-bright
knots. | Primordial Non-Gaussianity from LAMOST Surveys: The primordial non-Gaussianity (PNG) in matter density perturbation is a very
powerful probe of the physics of the very early Universe. The local PNG can
induce a distinct scale-dependent bias on the large scale structure
distribution of galaxies and quasars, which could be used for constraining it.
We study the detection limits on PNG from the surveys of the LAMOST telescope.
The cases of the main galaxy survey, the luminous red galaxy (LRG) survey, and
the quasar survey of different magnitude limits are considered. We find that
the MAIN1 sample (i.e. the main galaxy survey with one magnitude deeper than
the SDSS main galaxy survey, or r<18.8) could only provide very weak constraint
on PNG. For the MAIN2 sample (r<19.8) and the LRG survey, the 2\sigma (95.5%)
limit on the PNG parameter f_{NL} are |f_{NL}|<145 and |f_{NL}|<114
respectively, comparable to the current limit from cosmic microwave background
(CMB) data. The quasar survey could provide much more stringent constraint, and
we find that the 2\sigma limit for |f_{NL}| is between 50 and 103, depending on
the magnitude limit of the survey. With Planck-like priors on cosmological
parameters, the quasar survey with g<21.65 would improve the constraints to
|f_{NL}|<43 (2\sigma). We also discuss the possibility of further tightening
the constraint by using the relative bias method proposed by Seljak(2008). |
Testable dark energy predictions from current data: Given a class of dark energy models, constraints from one set of cosmic
acceleration observables make predictions for other observables. Here we
present the allowed ranges for the expansion rate H(z), distances D(z), and the
linear growth function G(z) (as well as other, derived growth observables) from
the current combination of cosmological measurements of supernovae, the cosmic
microwave background, baryon acoustic oscillations, and the Hubble constant.
With a cosmological constant as the dark energy and assuming near-minimal
neutrino masses, the growth function is already predicted to better than 2%
precision at any redshift, with or without spatial curvature. Direct
measurements of growth that match this precision offer the opportunity to
stringently test and potentially rule out a cosmological constant. While
predictions in the broader class of quintessence models are weaker, it is
remarkable that they are typically within a factor of 2-3 of forecasts for
future space-based supernovae and Planck CMB measurements. In particular,
measurements of growth at any redshift, or the Hubble constant H_0, that exceed
LambdaCDM predictions by substantially more than 2% would rule out not only a
cosmological constant but also the whole quintessence class, with or without
curvature and early dark energy. Barring additional systematic errors hiding in
the data, such a discovery would require more exotic explanations of cosmic
acceleration such as phantom dark energy, dark energy clustering, or
modifications of gravity. | Testing the effects from dark radiation: In this letter, the effects of dark radiation (DR) are tested. Theoretically,
the phase-space analysis method is applied to check whether the model is
consist with the history of our universe which shows positive results.
Observationally, by using the observational data ($SNLS$ (SuperNovae Legacy
Survey), $WMAP9$(Wilkinson Microwave Anisotropy Probe 9 Years Result), $PLANCK$
(Planck First Data Release), $BAO$ (Baryon Acoustic Oscillations), $H(z)$
(Hubble Parameter Data) and $BBN$ (Big Bang Nucleosynthesis)), the dark
radiation is found to have the effect of wiping out the tension between the
$SNLS$ data and the other data in flat $\Lambda CDM$ model. The effects of dark
radiation also make the best fit value of $N_{eff}$ slightly larger than 3.04. |
A 2% Distance to z=0.35 by Reconstructing Baryon Acoustic Oscillations -
I : Methods and Application to the Sloan Digital Sky Survey: We apply the reconstruction technique to the clustering of galaxies from the
SDSS DR7 LRG sample, sharpening the baryon acoustic oscillation (BAO) feature
and achieving a 1.9% measurement of the distance to z=0.35. This is the first
application of reconstruction of the BAO feature in a galaxy redshift survey.
We update the reconstruction algorithm of Eisenstein et al, 2007 to account for
the effects of survey geometry as well as redshift-space distortions and
validate it on 160 LasDamas simulations. We demonstrate that reconstruction
sharpens the BAO feature in the angle averaged galaxy correlation function,
reducing the nonlinear smoothing scale \Sigma_nl from 8.1 Mpc/h to 4.4 Mpc/h.
Reconstruction also significantly reduces the effects of redshift-space
distortions at the BAO scale, isotropizing the correlation function. This
sharpened BAO feature yields an unbiased distance estimate (< 0.2%) and reduces
the scatter from 3.3% to 2.1%. We demonstrate the robustness of these results
to the various reconstruction parameters, including the smoothing scale, the
galaxy bias and the linear growth rate. Applying this reconstruction algorithm
to the SDSS LRG DR7 sample improves the significance of the BAO feature in
these data from 3.3 sigma for the unreconstructed correlation function, to 4.2
sigma after reconstruction. We estimate a relative distance scale D_V/r_s to
z=0.35 of 8.88+/-0.17, where r_s is the sound horizon and D_V = (D_A^2/H)^{1/3}
is a combination of the angular diameter distance D_A and Hubble parameter H.
Assuming a sound horizon of 154.25 Mpc, this translates into a distance
measurement D_V (z=0.35) = 1.356+/-0.025 Gpc. We find that reconstruction
reduces the distance error in the DR7 sample from 3.5% to 1.9%, equivalent to a
survey with three times the volume of SDSS. | The Local Hole: a galaxy under-density covering 90% of sky to ~200 Mpc: We investigate the `Local Hole', an anomalous under-density in the local
galaxy environment, by extending our previous galaxy $K-$band number-redshift
and number-magnitude counts to $\approx 90\%$ of the sky. Our redshift samples
are taken from the 2MASS Redshift Survey (2MRS) and the 2M++ catalogues,
limited to $K<11.5$. We find that both surveys are in good agreement, showing
an $\approx 21-22\%$ under-density at $z<0.075$ when compared to our
homogeneous counts model that assumes the same luminosity function and other
parameters as in our earlier papers. Using the Two Micron All Sky Survey
(2MASS) for $n(K)$ galaxy counts, we measure an under-density relative to this
model of $20\pm 2 \%$ at $K<11.5$, which is consistent in both form and scale
with the observed $n(z)$ under-density. To examine further the accuracy of the
counts model, we compare its prediction for the fainter $n(K)$ counts of the
Galaxy and Mass Assembly (GAMA) survey. We further compare these data with a
model assuming the parameters of a previous study where little evidence for the
Local Hole was found. At $13<K<16$ we find a significantly better fit for our
model, arguing for our higher luminosity function normalisation. Although our
implied under-density of $\approx 20\%$ means local measurements of the Hubble
Constant have been over-estimated by $\approx3$\%, such a scale of
under-density is in tension with a global $\Lambda$CDM cosmology at an
$\approx3\sigma$ level. |
Constraints on the electron-to-proton mass ratio variation at the epoch
of reionization: Far infrared fine-structure transitions of CI and CII and rotational
transitions of CO are used to probe hypothetical variations of the
electron-to-proton mass ratio mu = m_e/m_p at the epoch of reionization (z >
6). A constraint on Delta mu/mu = (mu_obs - mu_lab)/mu_lab = (0.7 +/-
1.2)x10^-5 (1sigma) obtained at <z> = 6.31 is the most stringent up-to-date
limit on the variation of mu at such high redshift. For all available estimates
of Delta mu/mu ranging between z = 0 and z = 1100, - the epoch of
recombination, - a regression curve Delta mu/mu = k_mu (1+z)^p, with k_mu =
(1.6 +/- 0.3) x10^-8 and p = 2.00 +/- 0.03, is deduced. If confirmed, this
would imply a dynamical nature of dark matter/dark energy. | A numerical study of the effects of primordial non-Gaussianities on weak
lensing statistics: While usually cosmological initial conditions are assumed to be Gaussian,
inflationary theories can predict a certain amount of primordial
non-Gaussianity which can have an impact on the statistical properties of the
lensing observables. In order to evaluate this effect, we build a large set of
realistic maps of different lensing quantities starting from light-cones
extracted from large dark-matter only N-body simulations with initial
conditions corresponding to different levels of primordial local
non-Gaussianity strength $f_{\rm NL}$. Considering various statistical
quantities (PDF, power spectrum, shear in aperture, skewness and bispectrum) we
find that the effect produced by the presence of primordial non-Gaussianity is
relatively small, being of the order of few per cent for values of $|f_{\rm
NL}|$ compatible with the present CMB constraints and reaching at most 10-15
per cent for the most extreme cases with $|f_{\rm NL}|=1000$. We also discuss
the degeneracy of this effect with the uncertainties due to the power spectrum
normalization $\sigma_8$ and matter density parameter $\Omega_{\rm m}$, finding
that an error in the determination of $\sigma_8$ ($\Omega_{\rm m}$) of about 3
(10) per cent gives differences comparable with non-Gaussian models having
$f_{\rm NL}=\pm 1000$. These results suggest that the possible presence of an
amount of primordial non-Gaussianity corresponding to $|f_{\rm NL}|=100$ is not
hampering a robust determination of the main cosmological parameters in present
and future weak lensing surveys, while a positive detection of deviations from
the Gaussian hypothesis is possible only breaking the degeneracy with other
cosmological parameters and using data from deep surveys covering a large
fraction of the sky. |
Forecast constraints on the baryonic feedback effect from the future
kinetic Sunyaev-Zel'dovich effect detection: The baryonic feedback effect is an important systematic error in the weak
lensing (WL) analysis. It contributes partly to the $S_8$ tension in the
literature. With the next generations of large scale structure (LSS) and CMB
experiments, the high signal-to-noise kinetic Sunyaev-Zel'dovich (kSZ) effect
detection can tightly constrain the baryon distribution in and around dark
matter halos, and quantify the baryonic effect in the weak lensing statistics.
In this work, we apply the Fisher matrix technique to predict the future kSZ
constraints on 3 kSZ-sensitive Baryon Correction Model (BCM) parameters. Our
calculations show that, in combination with next generation LSS surveys, the
3rd generation CMB experiments such as AdvACT and Simon Observatory can
constrain the matter power spectrum damping $S(k)$ to the precision of
$\sigma_S(k)<0.8\%\sqrt{37.8{\rm Gpc}^3h^{-3}/V}$ at $k\lesssim 10h/$Mpc, where
$V$ is the overlapped survey volume between the future LSS and CMB surveys. For
the 4th generation CMB surveys such as CMB-S4 and CMB-HD, the constraint will
be enhanced to $\sigma_S(k)<0.4\%\sqrt{37.8{\rm Gpc}^3h^{-3}/V}$. If
extra-observations, e.g. X-ray detection and thermal SZ observation, can
effectively fix the gas density profile slope parameter $\delta$, the
constraint on $S(k)$ will be further boosted to
$\sigma_S(k)<0.3\%\sqrt{37.8{\rm Gpc}^3h^{-3}/V}$ and
$\sigma_S(k)<0.1\%\sqrt{37.8{\rm Gpc}^3h^{-3}/V}$ for the 3rd and 4th
generation CMB surveys. | Surface Brightness Fluctuations as Primary and Secondary Distance
Indicators: The surface brightness fluctuations (SBF) method measures the variance in a
galaxy's light distribution arising from fluctuations in the numbers and
luminosities of individual stars per resolution element. Once calibrated for
stellar population effects, SBF measurements with HST provide distances to
early-type galaxies with unrivaled precision. Optical SBF data from HST for the
Virgo and Fornax clusters give the relative distances of these nearby fiducial
clusters with 2% precision and constrain their internal structures.
Observations in hand will allow us to tie the Coma cluster, the standard of
comparison for distant cluster studies, into the same precise relative distance
scale. The SBF method can be calibrated in an absolute sense either empirically
from Cepheids or theoretically from stellar population models. The agreement
between the model and empirical zero points has improved dramatically,
providing an independent confirmation of the Cepheid distance scale. SBF is
still brighter in the near-IR, and an ongoing program to calibrate the method
for the F110W and F160W passbands of the WFC3 IR channel will enable accurate
distance derivation whenever a large early-type galaxy or bulge is observed in
these passbands at distances reaching well out into the Hubble flow. |
A Systematic Look at the Effects of Radiative Feedback on Disc Galaxy
Formation: Galaxy formation models and simulations rely on various feedback mechanisms
to reproduce the observed baryonic scaling relations and galaxy morphologies.
Although dwarf galaxy and giant elliptical properties can be explained using
feedback from supernova and active galactic nuclei, Milky Way-sized galaxies
still represent a challenge to current theories of galaxy formation. In this
paper, we explore the possible role of feedback from stellar radiation in
regulating the main properties of disk galaxies such as our own Milky Way. We
have performed a suite of cosmological simulations of the same $\sim10^{12}
{\rm M}_{\odot}$ halo selected based on its rather typical mass accretion
history. We have implemented radiative feedback from young stars using a crude
model of radiative transfer for ultraviolet (UV) and infrared (IR) radiation.
However, the model is realistic enough such that the dust opacity plays a
direct role in regulating the efficiency of our feedback mechanism. We have
explored various models for the dust opacity, assuming different constant dust
temperatures, as well as a varying dust temperature model. We find that while
strong radiative feedback appears as a viable mechanism to regulate the stellar
mass fraction in massive galaxies, it also prevents the formation of discs with
reasonable morphologies. In models with strong stellar radiation feedback,
stellar discs are systematically too thick while the gas disc morphology is
completely destroyed due to the efficient mixing between the feedback-affected
gas and its surroundings. At the resolution of our simulation suite, we find it
impossible to preserve spiral disc morphology while at the same time expelling
enough baryons to satisfy the abundance matching constraints. | Primordial black holes and gravitational waves from resonant
amplification during inflation: We present a new realization of the resonant production of primordial black
holes as well as gravitational waves in a two-stage inflation model consisting
of a scalar field \phi with an axion-monodromy-like periodic structure in the
potential that governs the first stage and another field \chi with a
hilltop-like potential that dominates the second stage. The parametric
resonance seeded by the periodic structure at the first stage amplifies the
perturbations of both fields inside the Hubble radius. While the evolution of
the background trajectory experiences a turn as the oscillatory barrier height
increases, the amplified perturbations of \chi remain as they are and
contribute to the final curvature perturbation. It turns out that the
primordial power spectrum displays a significant resonant peak on small scales,
which can lead to an abundant production of primordial black holes.
Furthermore, gravitational waves are also generated from the resonantly
enhanced field perturbations during inflation, the amplitude of which may be
constrained by future gravitational wave interferometers. |
GRB 090426: Discovery of a jet break in a short burst afterglow: Context: The link between the duration of GRBs and the nature of their
progenitors remains disputed. Short bursts (with durations of less than ~2 s)
are less frequently observed, technically more difficult to localize, and
exhibit significantly fainter afterglows. Aims: It is of critical importance to
establish whether the burst duration can reliably distinguish the different GRB
population models of collapsars and compact stellar mergers. The Swift GRB
090426 provides an unique opportunity to address this question. Its duration
(T_90=1.28 s) places GRB 090426 firmly in the short burst population, while the
high redshift (z=2.609), host galaxy properties, and prompt emission spectral
characteristics are more similar to those of long-duration GRBs. Methods: On
the basis of data obtained with the Tautenburg 2m telescope (Germany) and the
7-channel imager GROND (La Silla, Chile), we compiled the most finely sampled
light curve available for a short burst optical/NIR afterglow. The light curve
was then analysed in a standard fashion. GROND and XRT data were used to
determine the broad-band spectral energy distribution of the afterglow across
more than three orders of magnitude. Results: Our data show that a light curve
break exists at 0.4 days, which is followed by a steep decay. This light curve
decay is achromatic in the optical/NIR bands, and interpreted as a post-jet
break phase. The X-ray data do not disagree with this interpretation.
Conclusions: The half-opening angle of the suspected jet as well as the
luminosity of the optical afterglow provide additional evidence that GRB 090426
is probably linked to the death of a massive star rather than to the merger of
two compact objects. | Excess of high-$z$ galaxies as a test for bumpy power spectrum of
density perturbations: Modified matter power spectra with approximately Gaussian bump on sub-Mpc
scales can be a result of a complex inflation. We consider five spectra with
different Gaussian amplitudes $A$ and locations $k_0$ and run N-body
simulations in a cube $(5 Mpc/h)^3$ at $z>8$ to reveal the halo mass functions
and their evolution with redshift. We have found that the Sheth-Tormen formula
provides a good approximation to a such kind of halo mass functions. In the
considered models the dark matter halo formation starts much more earlier than
in $\Lambda$CDM, which in turn can result in an earlier star formation and a
nuclear activity in galaxies and can be detected and tested by, e.g., JWST. At
$z=0$ the halo mass functions are hardly distinguishable from the standard
$\Lambda$CDM, therefore the models with the bumpy spectra can be identified in
observations by their excess in number of bright sources at high redshift only. |
Group galaxy number density profiles far out: is the 'one-halo' term NFW
out to $>10$ virial radii?: While the density profiles (DPs) of $\Lambda$CDM haloes obey the NFW law out
to roughly one virial radius, $r_{\rm vir}$, the structure of their outer parts
is still poorly understood, since the 1-halo term describing the halo itself is
dominated by the 2-halo term representing the other haloes picked up. Using a
semi-analytical model, we measure the real-space `1-halo' number DP of groups
out to $20\,r_{\rm vir}$ by assigning each galaxy to its nearest group with
mass above $M_{\rm a}$, in units of the group $r_{\rm vir}$. If $M_{\rm a}$ is
small (large), the outer DP of groups falls rapidly (slowly). We find that
there is an optimal $M_{\rm a}$ for which the stacked DP resembles the NFW
model to $0.1$ dex accuracy out to $\simeq 13\,r_{\rm vir}$. We find similar
long-range NFW surface DPs (out to $\simeq 10\,r_{\rm vir}$) in the SDSS
observations using a galaxy assignment scheme that combines the non-linear
virialized regions of groups with their linear outer parts. The optimal $M_{\rm
a}$ scales as the minimum mass of the groups that are stacked to the power
$0.25-0.3$. Our results suggest that the NFW model does not solely originate
from violent relaxation. Moreover, populating haloes with galaxies using HOD
models must proceed out to larger radii than usually done. | K-mouflage Imprints on Cosmological Observables and Data Constraints: We investigate cosmological constraints on K-mouflage models of modified
gravity. We consider two scenarios: one where the background evolution is free
to deviate from $\Lambda$CDM (K-mouflage) and another one which reproduces a
$\Lambda$CDM expansion (K-mimic), implementing both of them into the EFTCAMB
code. We discuss the main observational signatures of these models and we
compare their cosmological predictions to different datasets, including CMB,
CMB lensing, SNIa and different galaxy catalogues. We argue about the
possibility of relieving the $H_0$ and weak lensing tensions within these
models, finding that K-mouflage scenarios effectively ease the tension on the
Hubble Constant. Our final 95\% C.L. bounds on the $\epsilon_{2,0}$ parameter
that measures the overall departure from $\Lambda$CDM (corresponding to
$\epsilon_{2,0}=0$) are $-0.04\leq \epsilon_{2,0} <0$ for K-mouflage and $0<
\epsilon_{2,0} <0.002$ for K-mimic. In the former case the main constraining
power comes from changes in the background expansion history, while in the
latter case the model is strongly constrained by measurements of the amplitude
of matter perturbations. The sensitivity of these cosmological constraints
closely matches that of solar system probes. We show that these constraints
could be significantly tightened with future ideal probes like CORE. |
Mixing of blackbodies: Increasing our view of inflation to 17 e-folds
with spectral distortions from Silk damping: Silk damping in the early Universe, before and during recombination, erases
anisotropies in the cosmic microwave background (CMB) on small scales. This
power, which disappears from anisotropies, appears in the monopole as y-type,
i-type and \mu-type distortions. The observation of the CMB spectral
distortions will thus make available to us the information about the primordial
power spectrum on scales corresponding to the comoving wavenumbers $8< k < 10^4
Mpc^{-1}$ increasing our total view of inflation, when combined with CMB
anisotropies, to span 17 e-folds. These distortions can be understood simply as
mixing of blackbodies of different temperatures and the subsequent
comptonization of the resulting distortions. | Lensing-like tensions in the Planck legacy release: We analyze the final release of the Planck satellite data to constrain the
gravitational lensing potential in a model-independent manner. The amount of
lensing determined from the smoothing of the acoustic peaks in the temperature
and polarization power spectra is 2$\sigma$ too high when compared with the
measurements using the lensing reconstruction and 2.8$\sigma$ too high when
compared with $\Lambda$CDM expectation based on the "unlensed" portion of the
temperature and polarization power spectra. The largest change from the
previous data release is the $\Lambda$CDM expectation, driven by improved
constraints to the optical depth to reionization. The anomaly still is
inconsistent with actual gravitational lensing, given that the lensing
reconstruction constraints are discrepant independent of the model. Within the
context of $\Lambda$CDM, improvements in its parameter constraints from lensing
reconstruction bring this tension to 2.1$\sigma$ and from further adding baryon
acoustic oscillation and Pantheon supernova data to a marginally higher
2.2$\sigma$. Once these other measurements are included, marginalizing this
lensing-like anomaly cannot substantially resolve tensions with low-redshift
measurements of $H_0$ and $S_8$ in $\Lambda$CDM, $\Lambda$CDM+$N_\mathrm{eff}$
or $\Lambda$CDM+$\sum m_\nu$; furthermore the artificial strengthening of
constraints on $\sum m_\nu$ is less than 20%. |
Gas rotation in galaxy clusters: signatures and detectability in X-rays: We study simple models of massive galaxy clusters in which the intracluster
medium (ICM) rotates differentially in equilibrium in the cluster gravitational
potential. We obtain the X-ray surface brightness maps, evaluating the isophote
flattening due to the gas rotation. Using a set of different rotation laws, we
put constraint on the amplitude of the rotation velocity, finding that rotation
curves with peak velocity up to \sim 600 km s^-1 are consistent with the
ellipticity profiles of observed clusters. We convolve each of our models with
the instrument response of the X-ray Calorimeter Spectrometer on board the
ASTRO-H to calculate the simulated X-ray spectra at different distance from the
X-ray centre. We demonstrate that such an instrument will allow us to measure
rotation of the ICM in massive clusters, even with rotation velocities as low
as \sim 100 km s^-1 | Weak Lensing Reconstruction by Counting DECaLS Galaxies: Alternative to weak lensing measurements through cosmic shear, we present a
weak lensing convergence $\hat{\kappa}$ map reconstructed through cosmic
magnification effect in DECaLS galaxies of the DESI imaging surveys DR9. This
is achieved by linearly weighing $12$ maps of galaxy number overdensity in
different magnitude bins of $grz$ photometry bands. The weight is designed to
eliminate the mean galaxy deterministic bias, minimize galaxy shot noise while
maintaining the lensing convergence signal. We also perform corrections of
imaging systematics in the galaxy number overdensity. The $\hat{\kappa}$ map
has $8365$ deg$^2$ sky coverage. Given the low number density of DECaLS
galaxies, the $\hat{\kappa}$ map is overwhelmed by shot noise and the map
quality is difficult to evaluate using the lensing auto-correlation.
Alternatively, we measure its cross-correlation with the cosmic shear catalogs
of DECaLS galaxies of DESI imaging surveys DR8, which has $8365$ deg$^2$
overlap in sky coverage with the $\hat{\kappa}$ map. We detect a
convergence-shear cross-correlation signal with $S/N\simeq 10$. The analysis
also shows that the galaxy intrinsic clustering is suppressed by a factor
$\mathcal{O}(10^2)$ and the residual galaxy clustering contamination in the
$\hat{\kappa}$ map is consistent with zero. Various tests with different galaxy
and shear samples, and the Akaike information criterion analysis all support
the lensing detection. So is the imaging systematics corrections, which enhance
the lensing signal detection by $\sim 30\%$. We discuss various issues for
further improvement of the measurements. |
Foreground Model and Antenna Calibration Errors in the Measurement of
the Sky-Averaged λ21 cm Signal at z~20: The most promising near-term observable of the cosmic dark age prior to
widespread reionization (z~15-200) is the sky-averaged \lambda 21 cm background
arising from hydrogen in the intergalactic medium. Though an individual antenna
could in principle detect the line signature, data analysis must separate
foregrounds that are orders of magnitude brighter than the \lambda 21 cm
background (but that are anticipated to vary monotonically and gradually with
frequency). Using more physically motivated models for foregrounds than in
previous studies, we show that the intrinsic "spectral smoothness" of the
foregrounds is likely not a concern, and that data analysis for an ideal
antenna should be able to detect the \lambda 21 cm signal after deprojecting a
~5th order polynomial in log(\nu). However, we find that the foreground signal
is corrupted by the frequency-dependent response of a real antenna. The
frequency dependence complicates modeling of foregrounds commonly based on the
assumption of spectral smoothness. Much of our study focuses on the
Large-aperture Experiment to detect the Dark Age (LEDA), which combines both
radiometric and interferometric measurements. We show that statistical
uncertainty remaining after fitting antenna gain patterns to interferometric
measurements does not compromise extraction of the \lambda 21 cm signal for a
range of cosmological models after fitting a 7th order polynomial to
radiometric data. Our results generalize to most efforts to measure the
sky-averaged spectrum. | Testing growth rate dependence in cosmological perturbation theory using
scale-free models: We generalize previously derived analytic results for the one-loop power
spectrum (PS) in scale-free models (with linear PS $P(k) \propto k^n$) to a
broader class of such models in which part of the matterlike component driving
the Einstein de Sitter expansion does not cluster. These models can be
conveniently parametrized by $\alpha$, the constant logarithmic linear growth
rate of fluctuations (with $\alpha=1$ in the usual case). For $-3< n<-1$, where
the one-loop PS is both infrared and ultraviolet convergent and thus explicitly
self-similar, it is characterized conveniently by a single numerical
coefficient $c(n, \alpha)$. We compare the analytical predictions for $c(n=-2,
\alpha)$ with results from a suite of $N$-body simulations with $\alpha \in
[0.25, 1]$ performed with an appropriately modified version of the GADGET code.
Although the simulations are of small ($256^3$) boxes, the constraint of
self-similarity allows the identification of the converged PS at a level of
accuracy sufficient to test the analytical predictions for the $\alpha$
dependence of the evolved PS. Good agreement for the predicted dependence on
$\alpha$ of the PS is found. To treat the UV sensitivity of results which grows
as one approaches $n =-1$, we derive exact results incorporating a
regularization $k_c$ and obtain expressions for $c(n, \alpha, k_c/k)$. Assuming
that this regularization is compatible with self-similarity allows us to infer
a predicted functional form of the PS equivalent to that derived in effective
field theory (EFT). The coefficient of the leading EFT correction at one loop
has a strong dependence on $\alpha$, with a change in sign at $\alpha \approx
0.16$, providing a potentially stringent test of EFT. |
Dark Mass Creation During EWPT Via Dark Energy Interaction: We add Dark Matter Dark Energy terms with a quintessence field interacting
with a Dark Matter field to a MSSM EW Lagrangian previously used to calculate
the magnetic field created during the EWPT. From the expectation value of the
quintessence field we estimate the Dark Matter mass for parameters used in
previous work on Dark Matter-Dark Energy interactions. | A Generalized Doppler and Aberration Kernel for Frequency-Dependent
Cosmological Observables: We introduce a $\textit{frequency-dependent}$ Doppler and aberration
transformation kernel for the harmonic multipoles of a general cosmological
observable with spin weight $s$, Doppler weight $d$ and arbitrary frequency
spectrum. In the context of Cosmic Microwave Background (CMB) studies, the
frequency-dependent formalism allows to correct for the motion-induced
aberration and Doppler effects on individual frequency maps with different
masks. It also permits to deboost background radiations with non-blackbody
frequency spectra, like extragalactic foregrounds and CMB spectra with
primordial spectral distortions. The formalism can also be used to correct
individual E and B polarization modes and account for motion-induced E/B mixing
of polarized observables with $d\neq1$ at different frequencies.
We apply the generalized aberration kernel on polarized and unpolarized CMB
specific intensity at 100 and 217 GHz and show that the motion-induced effects
typically increase with the frequency of observation. In all-sky CMB
experiments, the frequency-dependence of the motion-induced effects for a
blackbody spectrum are overall negligible. However in a cut-sky analysis,
ignoring the frequency dependence can lead to percent level error in the
polarized and unpolarized power spectra over all angular scales. In the
specific cut-sky used in our analysis ($b > 45^\circ, f_\text{sky}\simeq14\%$),
and for the dipole-inferred velocity $\beta=0.00123$ typically attributed to
our peculiar motion, the Doppler and aberration effects can change polarized
and unpolarized power spectra of specific intensity in the CMB rest frame by
$1-2\%$, but we find the polarization cross-leakage between E and B modes to be
negligible. |
The Impact of New d(p,γ)He3 Rates on Big Bang Nucleosynthesis: We consider the effect on Big Bang Nucleosynthesis (BBN) of new measurements
of the $d(p,\gamma){}^3$He cross section by the LUNA Collaboration. These have
an important effect on the primordial abundance of D/H which is also sensitive
to the baryon density at the time of BBN. We have re-evaluated the thermal rate
for this reaction, using a world average of cross section data, which we
describe with model-independent polynomials; our results are in good agreement
with a similar analysis by LUNA. We then perform a full likelihood analysis
combining BBN and Planck cosmic microwave background (CMB) likelihood chains
using the new rate combined with previous measurements and compare with the
results using previous rates. Concordance between BBN and CMB measurements of
the anisotropy spectrum using the old rates was excellent. The predicted
deuterium abundance at the Planck value of the baryon density was $({\rm
D/H})_{\rm BBN+CMB}^{\rm old} = (2.57 \pm 0.13) \times 10^{-5}$ which can be
compared with the value determined from quasar absorption systems $({\rm
D/H})_{\rm obs} = (2.55 \pm 0.03) \times 10^{-5} $. Using the new rates we find
$({\rm D/H})_{\rm BBN+CMB} = (2.51 \pm 0.11) \times 10^{-5}$. We thus find
consistency among BBN theory, deuterium and ${}^4$He observations, and the CMB,
when using reaction rates fit in our data-driven approach. We also find that
the new reaction data tightens the constraints on the number of relativistic
degrees of freedom during BBN, giving the effective number of light neutrino
species $N_\nu = 2.880 \pm 0.144$ in good agreement with the Standard Model of
particle physics. Finally, we note that the observed deuterium abundance
continues to be more precise than the BBN+CMB prediction, whose error budget is
now dominated by $d(d,n){}^3$He and $d(d,p){}^{3}{\rm H}$. | Modified Gravity Tomography: We consider the effect of a scalar field degree of freedom on the dynamics of
gravity from small to large scales. We show that the effects of modified
gravity can be completely captured by the time variations of the scalar field
mass and its coupling to matter. This leads to a parameterisation of modified
gravity where local constraints are easy to analyse and large scale scale
structure effects apparent. |
Improving Dark Energy Constraints with High Redshift Type Ia Supernovae
from CANDELS and CLASH: Aims. We investigate the degree of improvement in dark energy constraints
that can be achieved by extending Type Ia Supernova (SN Ia) samples to
redshifts z > 1.5 with the Hubble Space Telescope (HST), particularly in the
ongoing CANDELS and CLASH multi-cycle treasury programs.
Methods. Using the popular CPL parametrization of the dark energy, w = w0
+wa(1-a), we generate mock SN Ia samples that can be projected out to higher
redshifts. The synthetic datasets thus generated are fitted to the CPL model,
and we evaluate the improvement that a high-z sample can add in terms of
ameliorating the statistical and systematic uncertainties on cosmological
parameters.
Results. In an optimistic but still very achievable scenario, we find that
extending the HST sample beyond CANDELS+CLASH to reach a total of 28 SN Ia at z
> 1.0 could improve the uncertainty in the wa parameter by up to 21%. The
corresponding improvement in the figure of merit (FoM) would be as high as 28%.
Finally, we consider the use of high-redshift SN Ia samples to detect
non-cosmological evolution in SN Ia luminosities with redshift, finding that
such tests could be undertaken by future spacebased infrared surveys using the
James Webb Space Telescope (JWST). | Lyman break galaxy close and interacting pairs at z ~ 3: To date, the identification of interactions at z ~ 3 and above has relied on
morphological analysis. Here, we present five serendipitous spectroscopic z ~ 3
Lyman break galaxy (LBG) pairs with projected proper separations < 15 h^-1 kpc
in our survey of nine separate Keck fields. The data consist of 140 of our
highest signal-to-noise ratio LBG spectra and ~500 of our most confident
colour-selected LBGs. We show that the pairs are composed of two distinct close
and/or interacting LBGs from a detailed analysis of the rest-frame ultraviolet
spectra and images. In addition, we show that the pair number and separation
distribution is expected from (1) the angular correlation function when applied
to our survey and ~2500 colour-selected LBGs from the literature and (2) an
analysis of a carefully matched high-resolution hybrid numerical and analytical
cosmological simulation. Because the spectroscopic slitlets have random
orientations with respect to the close pairs on the sky, the serendipitous
pairs provide an unbiased sampling of the underlying close pair fraction.
Finally, we discover two Ly-a emitters (LAEs) in our slitlets and find that
they reside within 50 projected h^-1 kpc of LBGs. In this work, we uncover a
strong relationship between Ly-a emission and pair separation. All confirmed
and all candidate LBG pairs with separations of < 15 projected h^-1 kpc exhibit
Ly-a in emission and we find an overabundance of Ly-a emission in pairs with <
50 projected h^-1 kpc separations. This relationship suggests a picture in
which a measurable fraction of the Ly-a emission of LBGs, and potentially LAEs,
is generated via interaction mechanisms. As a result, serendipitous
spectroscopic close pairs provide a unique means to help identify and study
high-redshift galaxy interactions using conventional ground-based optical data. |
Chemical complexity in NGC1068: We aimed to study the chemistry of the circumnuclear molecular gas of
NGC1068, and to compare it with those of the starburst galaxies M82 and NGC253.
Using the IRAM-30m telescope, we observed the inner 2 kpc of NGC1068 between
86.2 GHz and 115.6 GHz. We identified 35 spectral features, corresponding to 24
different molecular species. Among them, HC3N, SO, N2H+, CH3CN, NS, 13CN, and
HN13C are detected for the first time in NGC1068. Assuming local thermodynamic
equilibrium (LTE), we calculated the column densities of the detected
molecules, as well as the upper limits to the column densities of some
undetected species. The comparison among the chemistries of NGC1068, M82, and
NGC253, suggests that, apart from X-rays, shocks also determine the chemistry
of NGC1068. We propose the column density ratio between CH3CCH and HC3N as a
prime indicator of the imprints of starburst and AGN environments in the
circumnuclear interstellar medium. This ratio is, at least, 64 times larger in
M82 than in NGC1068, and, at least, 4 times larger in NGC253 than in NGC1068.
Finally, we used the UCL_CHEM and UCL_PDR chemical codes to constrain the
origin of the species, as well as to test the influence of UV radiation fields
and cosmic rays on the observed abundances. | Host galaxy colour gradients and accretion disc obscuration in AEGIS z~1
X-ray-selected active galactic nuclei: We describe the effect of AGN light on host galaxy optical and UV-optical
colours, as determined from X-ray-selected AGN host galaxies at z~1, and
compare the AGN host galaxy colours to those of a control sample matched to the
AGN sample in both redshift and stellar mass. We identify as X-ray-selected
AGNs 8.7 +4/-3 per cent of the red-sequence control galaxies, 9.8 +/-3 per cent
of the blue-cloud control galaxies, and 14.7 +4/-3 per cent of the green-valley
control galaxies. The nuclear colours of AGN hosts are generally bluer than
their outer colours, while the control galaxies exhibit redder nuclei. AGNs in
blue-cloud host galaxies experience less X-ray obscuration, while AGNs in
red-sequence hosts have more, which is the reverse of what is expected from
general considerations of the interstellar medium. Outer and integrated colours
of AGN hosts generally agree with the control galaxies, regardless of X-ray
obscuration, but the nuclear colours of unobscured AGNs are typically much
bluer, especially for X-ray luminous objects. Visible point sources are seen in
many of these, indicating that the nuclear colours have been contaminated by
AGN light and that obscuration of the X-ray radiation and visible light are
therefore highly correlated. Red AGN hosts are typically slightly bluer than
red-sequence control galaxies, which suggests that their stellar populations
are slightly younger. We compare these colour data to current models of AGN
formation. The unexpected trend of less X-ray obscuration in blue-cloud
galaxies and more in red-sequence galaxies is problematic for all AGN feedback
models, in which gas and dust is thought to be removed as star formation shuts
down. [See paper for full abstract.] |
A Multi-Wavelength Study of Low Redshift Clusters of Galaxies I.
Comparison of X-ray and Mid-Infrared Selected AGNs: Clusters of galaxies have long been used as laboratories for the study of
galaxy evolution, but despite intense, recent interest in feedback between AGNs
and their hosts, the impact of environment on these relationships remains
poorly constrained. We present results from a study of AGNs and their host
galaxies found in low-redshift galaxy clusters. We fit model spectral energy
distributions (SEDs) to the combined visible and mid-infrared (MIR) photometry
of cluster members and use these model SEDs to determine stellar masses and
star-formation rates (SFRs). We identify two populations of AGNs, the first
based on their X-ray luminosities (X-ray AGNs) and the second based on the
presence of a significant AGN component in their model SEDs (IR AGNs). We find
that the two AGN populations are nearly disjoint; only 8 out of 44 AGNs are
identified with both techniques. We further find that IR AGNs are hosted by
galaxies with similar masses and SFRs but higher specific SFRs (sSFRs) than
X-ray AGN hosts. The relationship between AGN accretion and host star-formation
in cluster AGN hosts shows no significant difference compared to the
relationship between field AGNs and their hosts. The projected radial
distributions of both AGN populations are consistent with the distribution of
other cluster members. We argue that the apparent dichotomy between X-ray and
IR AGNs can be understood as a combination of differing extinction due to cold
gas in the host galaxies of the two classes of AGNs and the presence of weak
star-formation in X-ray AGN hosts. | A general relativistic signature in the galaxy bispectrum: the local
effects of observing on the lightcone: Next-generation galaxy surveys will increasingly rely on the galaxy
bispectrum to improve cosmological constraints, especially on primordial
non-Gaussianity. A key theoretical requirement that remains to be developed is
the analysis of general relativistic effects on the bispectrum, which arise
from observing galaxies on the past lightcone, {as well as from relativistic
corrections to the dynamics}. {As an initial step towards a fully relativistic
analysis of the galaxy bispectrum, we compute for the first time the local
relativistic lightcone effects on the bispectrum,} which come from Doppler and
gravitational potential contributions. For the galaxy bispectrum, the problem
is much more complex than for the power spectrum, since we need the lightcone
corrections at second order. Mode-coupling contributions at second order mean
that relativistic corrections can be non-negligible at smaller scales than in
the case of the power spectrum. In a primordial Gaussian universe, we show that
the local lightcone corrections for squeezed shapes at $z\sim1$ mean that the
bispectrum can differ from the Newtonian prediction by $\gtrsim 10\%$ when the
short modes are $k\lesssim (50\,{\rm Mpc})^{-1}$. These relativistic projection
effects, if ignored in the analysis of observations, could be mistaken for
primordial non-Gaussianity. For upcoming surveys which probe equality scales
and beyond, {all relativistic lightcone effects and relativistic dynamical
corrections should be included} for an accurate measurement of primordial
non-Gaussianity. |
Measuring $H_0$ using X-ray and SZ effect observations of dynamically
relaxed galaxy clusters: We use a sample of 14 massive, dynamically relaxed galaxy clusters to
constrain the Hubble Constant, $H_0$, by combining X-ray and Sunyaev-Zel'dovich
(SZ) effect signals measured with Chandra, Planck and Bolocam. This is the
first such analysis to marginalize over an empirical, data-driven prior on the
overall accuracy of X-ray temperature measurements, while our restriction to
the most relaxed, massive clusters also minimizes astrophysical systematics.
For a cosmological-constant model with $\Omega_m = 0.3$ and $\Omega_{\Lambda} =
0.7$, we find $H_0 = 67.3^{+21.3}_{-13.3}$ km/s/Mpc, limited by the temperature
calibration uncertainty (compared to the statistically limited constraint of
$H_0 = 72.3^{+7.6}_{-7.6}$ km/s/Mpc). The intrinsic scatter in the X-ray/SZ
pressure ratio is found to be $13 \pm 4$ per cent ($10 \pm 3$ per cent when two
clusters with significant galactic dust emission are removed from the sample),
consistent with being primarily due to triaxiality and projection. We discuss
the prospects for reducing the dominant systematic limitation to this analysis,
with improved X-ray calibration and/or precise measurements of the relativistic
SZ effect providing a plausible route to per cent level constraints on $H_0$. | Characteristic Lengths of Magnetic Field in Magnetohydrodynamic
Turbulence: In the framework of turbulence dynamo, flow motions amplify a weak seed
magnetic field through the stretching of field lines. Although the
amplification process has been a topic of active research, less attention has
been paid to the length scales of magnetic field. In this paper, we described a
numerical study on characteristic lengths of magnetic field in
magnetohydrodynamic turbulence. We considered the case of very weak or zero
mean magnetic field, which is applicable to the turbulence in the intergalactic
space. Our findings are as follows. (1) At saturation, the peak of magnetic
field spectrum occurs at $\sim L_0/2$, where $L_0$ is the energy injection
scale, while the most energy containing scale is $\sim L_0/5$. The peak scale
of spectrum of projected, two-dimensional field is $\sim L_0$. (2) During the
stage of magnetic field amplification, the energy equipartition scale shows a
power-law increase of $\sim t^{1.5}$, while the integral and curvature scales
show a linear increase. The equipartition, integral, and curvature scales
saturate at $\sim L_0$, $\sim 0.3L_0$, and $\sim 0.15L_0$, respectively. (3)
The coherence length of magnetic field defined in the Faraday rotation measure
(RM) due to the intergalactic magnetic field (IGMF) is related to the integral
scale. We presented a formula that expresses the standard deviation of RM,
$\sigma_{RM}$, in terms of the integral scale and rms strength of the IGMF, and
estimated that $\sigma_{RM}$ would be $\sim 100$ and $\sim$ a few rad m$^{-2}$
for clusters and filaments, respectively. |
A Self-Calibrating Halo-Based Group Finder: Application to SDSS: We apply a new galaxy group finder to the Main Galaxy Sample of the SDSS.
This algorithm introduces new freedom to assign halos to galaxies that is
self-calibrated by comparing the catalog to complementary data. These include
galaxy clustering data and measurements of the total satellite luminosity from
deep imaging data. We present constraints on the galaxy-halo connection for
star-forming and quiescent populations. The results of the self-calibrated
group catalog differ in several key ways from previous group catalogs and halo
occupation analyses. The transition halo mass scale, where half of halos
contain quiescent central galaxies, is at M_h~10^12.4 Msol/h, significantly
higher than other constraints. Additionally, the width of the transition from
predominantly star-forming halos to quiescent halos occurs over a narrower
range in halo mass. Quiescent central galaxies in low-mass halos are
significantly more massive than star-forming centrals at the same halo mass,
but this difference reverses above the transition halo mass. We find that the
scatter in logM* at fixed M_h is ~0.2 dex for massive halos, in agreement with
previous estimates, but rises sharply at lower halo masses. The halo masses
assigned by the group catalog are in good agreement with weak lensing estimates
for star-forming and quiescent central galaxies. We discuss possible
improvements to the algorithm made clear by this first application to data. The
group catalog is made publicly available. | Higher Derivative Mimetic Gravity: We study cosmological perturbations in mimetic gravity in the presence of
classified higher derivative terms which can make the mimetic perturbations
stable. We show that the quadratic higher derivative terms which are
independent of curvature and the cubic higher derivative terms which come from
curvature corrections are sufficient to remove instabilities in mimetic
perturbations. The advantage of working with the classified higher derivative
terms is that we can control both the background and the perturbation equations
allowing us to construct the higher derivative extension of mimetic dark matter
and the mimetic nonsingular bouncing scenarios. The latter can be thought as a
new higher derivative effective action for the loop quantum cosmology scenario
in which the equations of motion coincide with those suggested by loop quantum
cosmology. We investigate a possible connection between the mimetic cosmology
and the Randall-Sundrum cosmology. |
Cosmological Constraints on Variable Warm Dark Matter: Although $\Lambda$CDM model is very successful in many aspects, it has been
seriously challenged. Recently, warm dark matter (WDM) remarkably rose as an
alternative of cold dark matter (CDM). In the literature, many attempts have
been made to determine the equation-of-state parameter (EoS) of WDM. However,
in most of the previous works, it is usually assumed that the EoS of dark
matter (DM) is constant (and usually the EoS of dark energy is also constant).
Obviously, this assumption is fairly restrictive. It is more natural to assume
a variable EoS for WDM (and dark energy). In the present work, we try to
constrain the EoS of variable WDM with the current cosmological observations.
We find that the best fits indicate WDM, while CDM is still consistent with the
current observational data. However, $\Lambda$CDM is still better than WDM
models from the viewpoint of goodness-of-fit. So, in order to distinguish WDM
and CDM, the further observations on the small/galactic scale are required. On
the other hand, in this work we also consider WDM whose EoS is constant, while
the role of dark energy is played by various models. We find that the
cosmological constraint on the constant EoS of WDM is fairly robust. | Searching for Dark Clumps with Gravitational-Wave Detectors: Dark compact objects ("clumps") transiting the Solar System exert
accelerations on the test masses (TM) in a gravitational-wave (GW) detector. We
reexamine the detectability of these clump transits in a variety of current and
future GW detectors, operating over a broad range of frequencies. TM
accelerations induced by clump transits through the inner Solar System have
frequency content around $f \sim \mu$Hz. Some of us [arXiv:2112.11431] recently
proposed a GW detection concept with $\mu$Hz sensitivity, based on
asteroid-to-asteroid ranging. From the detailed sensitivity projection for this
concept, we find both analytically and in simulation that purely gravitational
clump-matter interactions would yield one detectable transit every $\sim 20$
yrs, if clumps with mass $m_{\text{cl}} \sim 10^{14} \text{kg}$ saturate the
dark-matter (DM) density. Other (proposed) GW detectors using local TMs and
operating in higher frequency bands are sensitive to smaller clump masses and
have smaller rates of discoverable signals. We also consider the case of clumps
endowed with an additional attractive long-range clump-matter fifth force
significantly stronger than gravity (but evading known fifth-force
constraints). For the $\mu$Hz detector concept, we use simulations to show
that, for example, a clump-matter fifth-force $\sim 10^3$ times stronger than
gravity with a range of $\sim\text{AU}$ would boost the rate of detectable
transits to a few per year for clumps in the mass range $10^{11} \text{kg}
\lesssim m_{\text{cl}} \lesssim 10^{14} \text{kg}$, even if they are a $\sim
1$% sub-component of the DM. The ability of $\mu$Hz GW detectors to probe
asteroid-mass-scale dark objects that may otherwise be undetectable bolsters
the science case for their development. |
Scale-dependent bias in the BAO-scale intergalactic neutral hydrogen: I discuss fluctuations in the neutral hydrogen (HI) density of the z~2.3
intergalactic medium and show that their relation to cosmic overdensity is
strongly scale-dependent. This behaviour arises from a linearized version of
the well-known "proximity effect", in which bright sources suppress atomic
hydrogen density. Using a novel, systematic and detailed linear-theory
radiative transfer calculation, I demonstrate how HI density consequently
anti-correlates with total matter density when averaged on scales exceeding the
Lyman-limit mean-free-path.
The radiative transfer thumbprint is highly distinctive and should be
measurable in the Lyman-alpha forest. Effects extend to sufficiently small
scales to generate significant distortion of the correlation function shape
around the baryon acoustic oscillation peak, although the peak location shifts
only by 1.2 percent for a mean source bias of b_j=3. The distortion changes
significantly with b_j and other astrophysical parameters; measuring it should
provide a helpful observational constraint on the nature of ionizing photon
sources in the near future. | The mass-richness relation of optically-selected clusters from weak
gravitational lensing and abundance with Subaru HSC first-year data: Constraining the relation between the richness $N$ and the halo mass $M$ over
a wide redshift range for optically-selected clusters is a key ingredient for
cluster-related science in optical surveys, including the Subaru Hyper
Suprime-Cam (HSC) survey. We measure stacked weak lensing profiles around 1747
HSC CAMIRA clusters over a redshift range of $0.1\leq z_{\rm cl}\leq 1.0$ with
$N\geq 15$ using the HSC first-year shear catalog covering $\sim$$140$ ${\rm
deg^2}$. The exquisite depth and image quality of the HSC survey allow us to
measure lensing signals around the high-redshift clusters at $0.7\leq z_{\rm
cl}\leq 1.0$ with a signal-to-noise ratio of 19 in the comoving radius range
$0.5\lesssim R\lesssim 15 h^{-1}{\rm Mpc}$. We constrain richness-mass
relations $P(\ln N|M,z)$ of the HSC CAMIRA clusters assuming a log-normal
distribution without informative priors on model parameters, by jointly fitting
to the lensing profiles and abundance measurements under both Planck and WMAP
cosmological models. We show that our model gives acceptable $p$-values when we
add redshift dependent terms which are proportional to $\ln (1+z)$ and $[\ln
(1+z)]^{2}$ into the mean and scatter relations of $P(\ln N|M,z)$. Such terms
presumably originate from the variation of photometric redshift errors as a
function of the redshift. We show that the constraints on the mean relation
$\langle M|N \rangle$ are consistent between the Planck and WMAP models,
whereas the scatter values $\sigma_{\ln M|N}$ for the Planck model are
systematically larger than those for the WMAP model. We also show that the
scatter values for the Planck model increase toward lower richness values,
whereas those for the WMAP model are consistent with constant values as a
function of richness. This result highlights the importance of the scatter in
the mass-richness relation for cluster cosmology. |
Detection of An Unidentified Emission Line in the Stacked X-ray spectrum
of Galaxy Clusters: We detect a weak unidentified emission line at E=(3.55-3.57)+/-0.03 keV in a
stacked XMM spectrum of 73 galaxy clusters spanning a redshift range 0.01-0.35.
MOS and PN observations independently show the presence of the line at
consistent energies. When the full sample is divided into three subsamples
(Perseus, Centaurus+Ophiuchus+Coma, and all others), the line is significantly
detected in all three independent MOS spectra and the PN "all others" spectrum.
It is also detected in the Chandra spectra of Perseus with the flux consistent
with XMM (though it is not seen in Virgo). However, it is very weak and located
within 50-110eV of several known faint lines, and so is subject to significant
modeling uncertainties. On the origin of this line, we argue that there should
be no atomic transitions in thermal plasma at this energy. An intriguing
possibility is the decay of sterile neutrino, a long-sought dark matter
particle candidate. Assuming that all dark matter is in sterile neutrinos with
m_s=2E=7.1 keV, our detection in the full sample corresponds to a neutrino
decay mixing angle sin^2(2theta)=7e-11, below the previous upper limits.
However, based on the cluster masses and distances, the line in Perseus is much
brighter than expected in this model. This appears to be because of an
anomalously bright line at E=3.62 keV in Perseus, possibly an Ar XVII
dielectronic recombination line, although its flux would be 30 times the
expected value and physically difficult to understand. In principle, such an
anomaly might explain our line detection in other subsamples as well, though it
would stretch the line energy uncertainties. Another alternative is the above
anomaly in the Ar line combined with the nearby 3.51 keV K line also exceeding
expectation by factor 10-20. Confirmation with Chandra and Suzaku, and
eventually Astro-H, are required to determine the nature of this new
line.(ABRIDGED) | Blazars distance indications from Fermi and TeV data: A new method to constrain the distance of blazars with unknown redshift using
combined observations in the GeV and TeV regimes will be presented. The
underlying assumption is that the Very High Energy (VHE) spectrum corrected for
the absorption of TeV photons by the Extragalactic Background Light (EBL) via
photon-photon interaction should still be softer than the extrapolation of the
gamma-ray spectrum observed by Fermi/LAT. Starting from the observed spectral
data at VHE, the EBL-corrected spectra are derived as a function of the
redshift z and fitted with power laws. Comparing the redshift dependent VHE
slopes with the power law fits to the LAT data an upper limit to the source
redshift can be derived. The method is applied to all TeV blazars detected by
LAT with known distance and an empirical law describing the relation between
the upper limits and the true redshifts is derived. This law can be used to
estimate the distance of unknown redshift blazars: as an example, the distance
of PKS 1424+240 is inferred. |
Globular cluster systems as tracers of environmental effects on Virgo
early-type dwarfs: Early-type dwarfs (dEs) are by far the most abundant galaxy population in
nearby clusters. Whether these objects are primordial, or the recent
end-products of the different physical mechanisms that can transform galaxies
once they enter these high-density environments, is still a matter of debate.
Here we present a novel approach to test these scenarios by comparing the
properties of the globular cluster systems (GCSs) of Virgo dEs and their
potential progenitors with simple predictions from gravitational and
hydrodynamical interaction models. We show that low-mass (Mstar < 2E8 Msun) dEs
have GCSs consistent with being the descendants of gas-stripped late-type
dwarfs. On the other hand, higher mass dEs have properties -including the high
mass specific frequencies of their GCSs and their concentrated spatial
distribution within Virgo- incompatible with a recent, environmentally-driven
evolution. They mostly comprise nucleated systems, but also dEs with recent
star formation and/or disc features. Bright, nucleated dEs appear to be a
population that has long resided within the cluster potential well, but have
surprisingly managed to retain very rich and spatially extended GCSs - possibly
an indication of high total masses. Our analysis does not favour violent
evolutionary mechanisms that result in significant stellar mass losses, but
more gentle processes involving gas removal by a combination of internal and
external factors, and highlights the relevant role of initial conditions.
Additionally, we briefly comment on the origin of luminous cluster S0s. | Gravitational Wave Hotspots: Ranking Potential Locations of
Single-Source Gravitational Wave Emission: The steadily improving sensitivity of pulsar timing arrays (PTAs) suggests
that gravitational waves (GWs) from supermassive black hole binary (SMBHB)
systems in the nearby universe will be de- tectable sometime during the next
decade. Currently, PTAs assume an equal probability of detection from every sky
position, but as evidence grows for a non-isotropic distribution of sources, is
there a most likely sky position for a detectable single source of GWs? In this
paper, a collection of galactic catalogs is used to calculate various metrics
related to the detectability of a single GW source resolv- able above a GW
background, assuming that every galaxy has the same probability of containing a
SMBHB. Our analyses of these data reveal small probabilities that one of these
sources is currently in the PTA band, but as sensitivity is improved regions of
consistent probability density are found in predictable locations, specifically
around local galaxy clusters. |
Discovery of Hydrogen Fluoride in the Cloverleaf Quasar at z = 2.56: We report the first detection of hydrogen fluoride (HF) toward a high
redshift quasar. Using the Caltech Submillimeter Observatory (CSO) we detect
the HF J = 1 - 0 transition in absorption toward the Cloverleaf, a broad
absorption line (BAL) quasi-stellar object (QSO) at z=2.56. The detection is
statistically significant at the ~ 6 sigma level. We estimate a lower limit of
4 \times 1014 cm-2 for the HF column density and using a previous estimate of
the hydrogen column density, we obtain a lower limit of 1.7 \times 10-9 for the
HF abundance. This value suggests that, assuming a Galactic N(HF)/NH ratio, HF
accounts for at least ~10% of the fluorine in the gas phase along the line of
sight to the Cloverleaf quasar. This observation corroborates the prediction
that HF should be a good probe of the molecular gas at high redshift.
Measurements of the HF abundance as a function of redshift are urgently needed
to better constrain the fluorine nucleosynthesis mechanism(s). | Central mass-to-light ratios and dark matter fractions in early-type
galaxies: Dynamical studies of local ETGs and the Fundamental Plane point to a strong
dependence of M/L ratio on luminosity (and stellar mass) with a relation of the
form $M/L \propto L^{\gamma}$. The "tilt" $\gamma$ may be caused by various
factors, including stellar population properties, IMF, rotational support,
luminosity profile non-homology and dark matter (DM) fraction. We evaluate the
impact of all these factors using a large uniform dataset of local ETGs from
Prugniel & Simien (1997). We take particular care in estimating the stellar
masses, using a general star formation history, and comparing different
population synthesis models. We find that the stellar M/L contributes little to
the tilt. We estimate the total M/L using simple Jeans dynamical models, and
find that adopting accurate luminosity profiles is important but does not
remove the need for an additional tilt component, which we ascribe to DM. We
survey trends of the DM fraction within one effective radius, finding it to be
roughly constant for galaxies fainter than $M_B \sim -20.5$, and increasing
with luminosity for the brighter galaxies; we detect no significant differences
among S0s and fast- and slow-rotating ellipticals. We construct simplified
cosmological mass models and find general consistency, where the DM transition
point is caused by a change in the relation between luminosity and effective
radius. A more refined model with varying galaxy star formation efficiency
suggests a transition from total mass profiles (including DM) of faint galaxies
distributed similarly to the light, to near-isothermal profiles for the bright
galaxies. These conclusions are sensitive to various systematic uncertainties
which we investigate in detail, but are consistent with the results of dynamics
studies at larger radii. |
Recombinations to the Rydberg States of Hydrogen and Their Effect During
the Cosmological Recombination Epoch: In this paper we discuss the effect of recombinations to highly excited
states (n > 100) in hydrogen during the cosmological recombination epoch. For
this purpose, we developed a new ODE solver for the recombination problem,
based on an implicit Gear's method. This solver allows us to include up to 350
l-resolved shells or ~61 000 separate levels in the hydrogen model and to solve
the recombination problem for one cosmology in ~27 hours. This is a huge
improvement in performance over our previous recombination code, for which a
100-shell computation (5050 separate states) already required ~150 hours on a
single processor. We show that for 350 shells down to redshift z ~200 the
results for the free electron fraction have practically converged. The final
modification in the free electron fraction at z ~200 decreases from about
\DeltaNe/Ne ~2.8% for 100 shells to \DeltaNe/Ne ~1.6% for 350 shells. However,
the associated changes in the CMB power spectra at large multipoles l are
rather small, so that for accurate computations in connection with the analysis
of Planck data already ~100 shells are expected to be sufficient. Nevertheless,
the total value of \tau could still be affected at a significant level. We also
briefly investigate the effect of collisions on the recombination dynamics.
With our current estimates for the collisional rates we find a correction of
\DeltaNe/Ne ~ -0.088% at z ~ 700, which is mainly caused by l-changing
collisions with protons. Furthermore, we present results on the cosmological
recombination spectrum, showing that at low frequencies collisional processes
are important. However, the current accuracy of collisional rates is
insufficient for precise computations of templates for the recombination
spectrum at \nu<~1 GHz, and also the effect of collisions on the recombination
dynamics suffers from the uncertainty in these rates. | SED fitting with Markov Chain Monte Carlo: Methodology and Application
to z=3.1 Lyman Alpha Emitting Galaxies: We present GalMC, a MCMC algorithm designed to fit the spectral energy
distributions (SED) of galaxies to infer physical properties such as age,
stellar mass, dust reddening, metallicity, redshift, and star formation rate.
We describe the features of the code and the extensive tests conducted to
ensure that our procedure leads to unbiased parameter estimation and accurate
evaluation of uncertainties. We compare its performance to grid-based
algorithms, showing that the efficiency in CPU time is ~ 100 times better for
MCMC for a three dimensional parameter space and increasing with the number of
dimensions. We use GalMC to fit the stacked SEDs of two samples of Lyman Alpha
Emitters (LAEs) at redshift z=3.1. Our fit reveals that the typical LAE
detected in the IRAC 3.6 micron band has age = 0.67 [0.37 - 1.81] Gyr and
stellar mass = 3.2 [2.5 - 4.2] x 10^9 M_Sun, while the typical LAE not detected
at 3.6 micron has age = 0.06 [0.01-0.2] Gyr and stellar mass = 2 [1.1 - 3.4] x
10^8 M_Sun. The SEDs of both stacks are consistent with the absence of dust.
The data do not significantly prefer exponential with respect to constant star
formation history. The stellar populations of these two samples are consistent
with the previous study by Lai et al, with some differences due to the improved
modeling of the stellar populations. A constraint on the metallicity of z=3.1
LAEs from broad-band photometry, requiring Z < Z_Sun at 95% confidence, is
found here for the first time. |
Optical identifications of high-redshift galaxy clusters from Planck
Sunyaev-Zeldovich survey: We present the results of optical identifications and spectroscopic redshifts
measurements for galaxy clusters from 2-nd Planck catalogue of
Sunyaev-Zeldovich sources (PSZ2), located at high redshifts, $z\approx0.7-0.9$.
We used the data of optical observations obtained with Russian-Turkish 1.5-m
telescope (RTT150), Sayan observatory 1.6-m telescope, Calar Alto 3.5-m
telescope and 6-m SAO RAS telescope (Bolshoi Teleskop Alt-azimutalnyi, BTA).
Spectroscopic redshift measurements were obtained for seven galaxy clusters,
including one cluster, PSZ2 G126.57+51.61, from the cosmological sample of PSZ2
catalogue. In central regions of two clusters, PSZ2 G069.39+68.05 and PSZ2
G087.39-34.58, the strong gravitationally lensed background galaxies are found,
one of them at redshift $z=4.262$. The data presented below roughly double the
number of known galaxy clusters in the second Planck catalogue of
Sunyaev-Zeldovich sources at high redshifts, $z\approx0.8$. | Observational rotation curves and density profiles vs. the Thomas-Fermi
galaxy structure theory: The Thomas-Fermi approach to galaxy structure determines selfconsistently the
fermionic warm dark matter (WDM) gravitational potential given the distribution
function f(E). This framework is appropriate for macroscopic quantum systems:
neutron stars, white dwarfs and WDM galaxies. Compact dwarf galaxies follow
from the quantum degenerate regime, while dilute and large galaxies from the
classical Boltzmann regime. We find analytic scaling relations for the main
galaxy magnitudes as halo radius r_h, mass M_h and phase space density. The
observational data for a large variety of galaxies are all well reproduced by
these theoretical scaling relations. For the compact dwarfs, our results show
small deviations from the scaling due to quantum macroscopic effects. We
contrast the theoretical curves for the circular velocities and density
profiles with the observational ones. All these results are independent of any
WDM particle physics model, they only follow from the gravity interaction of
the WDM particles and their fermionic nature. The theory rotation and density
curves reproduce very well for r < r_h the observations of 10 different and
independent sets of data for galaxy masses from 5x10^9 Msun till 5x10^{11}
Msun. Our normalized circular velocity curves turn to be universal functions of
r/r_h for all galaxies and reproduce very well the observational curves for r <
r_h. Conclusion: the Thomas-Fermi approach correctly describes the galaxy
structures (Abridged). |
Modeling the Kinematics of Distant Galaxies: Evolution of galaxies is one of the most actual topics in astrophysics. Among
the most important factors determining the evolution are two galactic
components which are difficult or even impossible to detect optically: the
gaseous disks and the dark matter halo. We use deep Hubble Space Telescope
images to construct a two-component (bulge + disk) model for stellar matter
distribution of galaxies. Properties of the galactic components are derived
using a three-dimensional galaxy modeling software, which also estimates disk
thickness and inclination angle. We add a gas disk and a dark matter halo and
use hydrodynamical equations to calculate gas rotation and dispersion profiles
in the resultant gravitational potential. We compare the kinematic profiles
with the Team Keck Redshift Survey observations. In this pilot study, two
galaxies are analyzed deriving parameters for their stellar components; both
galaxies are found to be disk-dominated. Using the kinematical model, the gas
mass and stellar mass ratio in the disk are estimated. | Clustering-based redshift estimation: application to VIPERS/CFHTLS: We explore the accuracy of the clustering-based redshift estimation proposed
by M\'enard et al. (2013) when applied to VIPERS and CFHTLS real data. This
method enables us to reconstruct redshift distributions from measurement of the
angular clus- tering of objects using a set of secure spectroscopic redshifts.
We use state of the art spectroscopic measurements with iAB < 22.5 from the
VIMOS Public Extragalactic Redshift Survey (VIPERS) as reference population to
infer the redshift distribution of galaxies from the Canada-France-Hawaii
Telescope Legacy Survey (CFHTLS) T0007 release. VIPERS provides a nearly
representative sample to the flux limit iAB < 22.5 at redshift > 0.5 which
allows us to test the accuracy of the clustering-based red- shift
distributions. We show that this method enables us to reproduce the true mean
color-redshift relation when both populations have the same magnitude limit. We
also show that this technique allows the inference of redshift distributions
for a population fainter than the one of reference and we give an estimate of
the color-redshift mapping in this case. This last point is of great interest
for future large redshift surveys which suffer from the need of a complete
faint spectroscopic sample. |
Spin-based removal of instrumental systematics in 21cm intensity mapping
surveys: Upcoming cosmological intensity mapping surveys will open new windows on the
Universe, but they must first overcome a number of significant systematic
effects, including polarization leakage. We present a formalism that uses scan
strategy information to model the effect of different instrumental systematics
on the recovered cosmological intensity signal for `single-dish'
(autocorrelation) surveys. This modelling classifies different systematics
according to their spin symmetry, making it particularly relevant for dealing
with polarization leakage. We show how to use this formalism to calculate the
expected contamination from different systematics as a function of the scanning
strategy. Most importantly, we show how systematics can be disentangled from
the intensity signal based on their spin properties via map-making. We
illustrate this, using a set of toy models, for some simple instrumental
systematics, demonstrating the ability to significantly reduce the
contamination to the observed intensity signal. Crucially, unlike existing
foreground removal techniques, this approach works for signals that are
non-smooth in frequency, e.g. polarized foregrounds. These map-making
approaches are simple to apply and represent an orthogonal and complementary
approach to existing techniques for removing systematics from upcoming 21cm
intensity mapping surveys. | Correlation of inflation-produced magnetic fields with scalar
fluctuations: If the conformal invariance of electromagnetism is broken during inflation,
then primordial magnetic fields may be produced. If this symmetry breaking is
generated by the coupling between electromagnetism and a scalar field---e.g.
the inflaton, curvaton, or the Ricci scalar---then these magnetic fields may be
correlated with primordial density perturbations, opening a new window to the
study of non-gaussianity in cosmology. In order to illustrate, we couple
electromagnetism to an auxiliary scalar field in a de Sitter background. We
calculate the power spectra for scalar-field perturbations and magnetic fields,
showing how a scale-free magnetic field spectrum with rms amplitude of ~nG at
Mpc scales may be achieved. We explore the Fourier-space dependence of the
cross-correlation between the scalar field and magnetic fields, showing that
the dimensionless amplitude, measured in units of the power spectra, can grow
as large as ~500 H_I/M, where H_I is the inflationary Hubble constant and M is
the effective mass scale of the coupling. |
Cosmological Constraints from Galaxy Cluster Sparsity, Cluster Gas Mass
Fraction and Baryon Acoustic Oscillations Data: In recent years, the availability of large, complete cluster samples has
enabled numerous cosmological parameter inference analyses using cluster number
counts. These have provided constraints on the cosmic matter density $\Omega_m$
and the amplitude of matter density fluctuations $\sigma_8$ alternative to
those obtained from other standard probes. However, systematics uncertainties,
such as the mass calibration bias and selection effects, may still
significantly affect these data analyses. Hence, it is timely to explore other
proxies of galaxy cluster cosmology that can provide cosmological constraints
complementary to those obtained from cluster number counts. Here, we use
measurements of the cluster sparsity from weak lensing mass estimates of the
LC$^2$-{\it single} and HSC-XXL cluster catalogs to infer constraints on a flat
$\Lambda$CDM model. The cluster sparsity has the advantage of being insensitive
to selection and mass calibration bias. On the other hand, it primarily
constrains a degenerate combination of $\Omega_m$ and $\sigma_8$ (along
approximately constant curves of $S_8=\sigma_8\sqrt{\Omega_m/0.3}$), and to
less extent the reduced Hubble parameter $h$. Hence, in order to break the
internal parameter degeneracies we perform a combined likelihood analysis of
cluster sparsities with cluster gas mass fraction measurements and BAO data. We
find marginal constraints that are competitive with those from other standard
cosmic probes: $\Omega_m=0.316\pm 0.013$, $\sigma_8=0.757\pm 0.067$
(corresponding to $S_8=0.776\pm 0.064$) and $h=0.696\pm 0.017$ at $1\sigma$.
Moreover, assuming a conservative Gaussian prior on the mass bias of gas mass
fraction data, we find a lower limit on the gas depletion factor
$Y_{b,500c}\gtrsim 0.89$. | Painting with baryons: augmenting N-body simulations with gas using deep
generative models: Running hydrodynamical simulations to produce mock data of large-scale
structure and baryonic probes, such as the thermal Sunyaev-Zeldovich (tSZ)
effect, at cosmological scales is computationally challenging. We propose to
leverage the expressive power of deep generative models to find an effective
description of the large-scale gas distribution and temperature. We train two
deep generative models, a variational auto-encoder and a generative adversarial
network, on pairs of matter density and pressure slices from the BAHAMAS
hydrodynamical simulation. The trained models are able to successfully map
matter density to the corresponding gas pressure. We then apply the trained
models on 100 lines-of-sight from SLICS, a suite of N-body simulations
optimised for weak lensing covariance estimation, to generate maps of the tSZ
effect. The generated tSZ maps are found to be statistically consistent with
those from BAHAMAS. We conclude by considering a specific observable, the
angular cross-power spectrum between the weak lensing convergence and the tSZ
effect and its variance, where we find excellent agreement between the
predictions from BAHAMAS and SLICS, thus enabling the use of SLICS for tSZ
covariance estimation. |
Cosmological and kinematical criteria for the ICRF2 sources selection: The most precise realization of inertial reference frame in astronomy is the
catalogue of 212 defining extragalactic radiosources with coordinates obtained
during VLBI observation runs in 1979-1995. IAU decided on the development of
the second realization of the ICRF2 catalogue. The criteria of best sources
selection (in terms of coordinates stability) must be defined as the first aim.
The selected sources have to keep stable the coordinate axes of inertial
astronomical frame.
Here we propose new criteria of source selection for the new ICRF catalogue.
The first one we call as "cosmological" and the second one as "kinematical".
The physical basis of these criteria is based on the assumption that apparent
motion of quasars (at angular scale of the order of hundred microarcseconds) is
connected with real motion inside quasars. Therefore apparent angular motion
corresponds to real physical motion of a "hot spot" inside a radio source. It
is shown that interval of redshift $0.8 \div 3.0$ is the most favorable in
terms that physical shift inside such sources corresponds to minimal apparent
angular shift of a "hot spot". Among "cosmologically" selected sources we
propose to select motionless sources and sources with linear motion which are
predictable and stable over long time interval.
To select sources which satisfies such conditions we analyzed known redshifts
of sources and time series obtained by our code and by different centers of
analysis of VLBI data. As a result of these analyses we select 137 sources as a
basis for the ICRF2 catalogue. | JWST high redshift galaxy observations have a strong tension with Planck
CMB measurements: JWST high redshift galaxy observations predict a higher star formation
efficiency than the standard cosmology does, which poses a new tension to
$\Lambda$CDM. We find that the situation is worse than expected. The true
situation is that the Planck CMB measurement has a strong tension with JWST
high redshift galaxy observations. Specifically, we make a trial to alleviate
this tension by considering alternative cosmological models including dark
matter-baryon interaction, $f(R)$ gravity and dynamical dark energy. Within
current cosmological constraints from Planck-2018 CMB data, we find that these
models all fail to explain such a large tension. A possible scenario to escape
from cosmological constraints is the extended Press-Schechter formalism, where
we consider the local environmental effect on the early formation of massive
galaxies. Interestingly, we find that an appropriate value of nonlinear
environmental overdensity of a high redshift halo can well explain this
tension. |
Validating the Fisher approach for stage IV spectroscopic surveys: In recent years forecasting activities have become a very important tool for
designing and optimising large scale structure surveys. To predict the
performance of such surveys, the Fisher matrix formalism is frequently used as
a fast and easy way to compute constraints on cosmological parameters. Among
them lies the study of the properties of dark energy which is one of the main
goals in modern cosmology. As so, a metric for the power of a survey to
constrain dark energy is provided by the Figure of merit (FoM). This is defined
as the inverse of the surface contour given by the joint variance of the dark
energy equation of state parameters $\{w_0,w_a\}$ in the
Chevallier-Polarski-Linder parameterisation, which can be evaluated from the
covariance matrix of the parameters. This covariance matrix is obtained as the
inverse of the Fisher matrix. Inversion of an ill-conditioned matrix can result
in large errors on the covariance coefficients if the elements of the Fisher
matrix have been estimated with insufficient precision. The conditioning number
is a metric providing a mathematical lower limit to the required precision for
a reliable inversion, but it is often too stringent in practice for Fisher
matrices with size larger than $2\times2$. In this paper we propose a general
numerical method to guarantee a certain precision on the inferred constraints,
like the FoM. It consists on randomly vibrating (perturbing) the Fisher matrix
elements with Gaussian perturbations of a given amplitude, and then evaluating
the maximum amplitude that keeps the FoM within the chosen precision. The steps
used in the numerical derivatives and integrals involved in the calculation of
the Fisher matrix elements can then be chosen accordingly in order to keep the
precision of the Fisher matrix elements below this maximum amplitude... | Disformally coupled inflation: A disformal coupling between two scalar fields is considered in the context
of cosmological inflation. The coupling introduces novel derivative
interactions mixing the kinetic terms of the fields but without introducing
superluminal or unstable propagation of the two scalar fluctuation modes.
Though the typical effect of the disformal coupling is to inhibit one of the
fields from inflating the universe, the energy density of the other field can
drive viable near Sitter -inflation in the presence of nontrivial disformal
dynamics, in particular when one assumes exponential instead of power-law form
for the couplings. The linear perturbation equations are written for the
two-field system, its canonical degrees of freedom are quantised, their spectra
are derived and the inflationary predictions are reported for numerically
solved exponential models. A generic prediction is low tensor-to-scalar ratio. |
Rosella: A mock catalogue from the P-Millennium simulation: The scientific exploitation of the Dark Energy Spectroscopic Instrument
Bright Galaxy Survey (DESI BGS) data requires the construction of mocks with
galaxy population properties closely mimicking those of the actual DESI BGS
targets. We create a high fidelity mock galaxy catalogue, including information
about galaxies and their host dark matter subhaloes. The mock catalogue uses
subhalo abundance matching (SHAM) with scatter to populate the P-Millennium
N-body simulation with galaxies at the median BGS redshift of ~ 0.2, using
formation redshift information to assign (g-r) rest-frame colours. The mock
provides information about r-band absolute magnitudes, (g-r) rest-frame
colours, 3D positions and velocities of a complete sample of DESI BGS galaxies
in a volume of (542 Mpc/h)^3, as well as the masses of host dark matter haloes.
This P-Millennium DESI BGS mock catalogue is ideally suited for the tuning of
approximate mocks unable to resolve subhaloes that DESI BGS galaxies reside in,
to test for systematics in analysis pipelines and to interpret
(non-cosmological focused) DESI BGS analysis. | Exploiting the full potential of photometric quasar surveys: Optimal
power spectra through blind mitigation of systematics: We present optimal measurements of the angular power spectrum of the XDQSOz
catalogue of photometric quasars from the Sloan Digital Sky Survey. These
measurements rely on a quadratic maximum likelihood estimator that
simultaneously measures the auto- and cross-power spectra of four redshift
samples, and provides minimum-variance, unbiased estimates even at the largest
angular scales. Since photometric quasars are known to be strongly affected by
systematics such as spatially-varying depth and stellar contamination, we
introduce a new framework of extended mode projection to robustly mitigate the
impact of systematics on the power spectrum measurements. This technique
involves constructing template maps of potential systematics, decorrelating
them on the sky, and projecting out modes which are significantly correlated
with the data. Our method is able to simultaneously process several thousands
of nonlinearly-correlated systematics, and mode projection is performed in a
blind fashion. Using our final power spectrum measurements, we find a good
agreement with theoretical predictions, and no evidence for further
contamination by systematics. Extended mode projection not only obviates the
need for aggressive sky and quality cuts, but also provides control over the
level of systematics in the measurements, enabling the search for small signals
of new physics while avoiding confirmation bias. |
Unequal-mass mergers of dark matter haloes with rare and frequent
self-interactions: Dark matter (DM) self-interactions have been proposed to solve problems on
small length scales within the standard cold DM cosmology. Here, we investigate
the effects of DM self-interactions in merging systems of galaxies and galaxy
clusters with equal and unequal mass ratios. We perform N-body DM-only
simulations of idealized setups to study the effects of DM self-interactions
that are elastic and velocity-independent. We go beyond the commonly adopted
assumption of large-angle (rare) DM scatterings, paying attention to the impact
of small-angle (frequent) scatterings on astrophysical observables and related
quantities. Specifically, we focus on DM-galaxy offsets, galaxy--galaxy
distances, halo shapes, morphology, and the phase--space distribution.
Moreover, we compare two methods to identify peaks: one based on the
gravitational potential and one based on isodensity contours. We find that the
results are sensitive to the peak finding method, which poses a challenge for
the analysis of merging systems in simulations and observations, especially for
minor mergers. Large DM-galaxy offsets can occur in minor mergers, especially
with frequent self-interactions. The subhalo tends to dissolve quickly for
these cases. While clusters in late merger phases lead to potentially large
differences between rare and frequent scatterings, we believe that these
differences are non-trivial to extract from observations. We therefore study
the galaxy/star populations which remain distinct even after the DM haloes have
coalesced. We find that these collisionless tracers behave differently for rare
and frequent scatterings, potentially giving a handle to learn about the
micro-physics of DM. | Synoptic Sky Surveys and the Diffuse Supernova Neutrino Background:
Removing Astrophysical Uncertainties and Revealing Invisible Supernovae: The cumulative (anti)neutrino production from all core-collapse supernovae
within our cosmic horizon gives rise to the diffuse supernova neutrino
background (DSNB), which is on the verge of detectability. The observed flux
depends on supernova physics, but also on the cosmic history of supernova
explosions; currently, the cosmic supernova rate introduces a substantial
(+/-40%) uncertainty, largely through its absolute normalization. However, a
new class of wide-field, repeated-scan (synoptic) optical sky surveys is coming
online, and will map the sky in the time domain with unprecedented depth,
completeness, and dynamic range. We show that these surveys will obtain the
cosmic supernova rate by direct counting, in an unbiased way and with high
statistics, and thus will allow for precise predictions of the DSNB. Upcoming
sky surveys will substantially reduce the uncertainties in the DSNB source
history to an anticipated +/-5% that is dominated by systematics, so that the
observed high-energy flux thus will test supernova neutrino physics. The
portion of the universe (z < 1) accessible to upcoming sky surveys includes the
progenitors of a large fraction (~ 87%) of the expected 10-26 MeV DSNB event
rate. We show that precision determination of the (optically detected) cosmic
supernova history will also make the DSNB into a strong probe of an extra flux
of neutrinos from optically invisible supernovae, which may be unseen either
due to unexpected large dust obscuration in host galaxies, or because some
core-collapse events proceed directly to black hole formation and fail to give
an optical outburst. |
Star formation in M33: the radial and local relations with the gas: In the Local Group spiral galaxy M33, we investigate the correlation between
the star formation rate (SFR) surface density, Sigma_SFR, and the gas density
Sigma_gas (molecular, atomic, and total). We also explore whether there are
other physical quantities, such as the hydrostatic pressure and dust optical
depth, which establish a good correlation with Sigma_SFR. We use the Ha,
far-ultraviolet (FUV), and bolometric emission maps to infer the SFR locally at
different spatial scales, and in radial bins using azimuthally averaged values.
Most of the local analysis is done using the highest spatial resolution allowed
by gas surveys, 180 pc. The Kennicutt-Schmidt (KS) law, Sigma_SFR \propto
(Sigma_gas)^n is analyzed by three statistical methods. At all spatial scales,
with Ha emission as a SFR tracer, the KS indices n are always steeper than
those derived with the FUV and bolometric emissions. We attribute this to the
lack of Ha emission in low luminosity regions where most stars form in small
clusters with an incomplete initial mass function at their high mass end. For
azimuthally averaged values the depletion timescale for the molecular gas is
constant, and the KS index is n_H2 = 1.1 +- 0.1. Locally, at a spatial
resolution of 180 pc, the correlation between Sigma_SFR and Sigma_gas is
generally poor, even though it is tighter with the molecular and total gas than
with the atomic gas alone. Considering only positions where the CO J=1-0 line
is above the 2-sigma detection threshold and taking into account uncertainties
in Sigma_H2 and Sigma_SFR, we obtain a steeper KS index than obtained with
radial averages: n_H2 = 2.22 +- 0.07 (for FUV and bolometric SFR tracers),
flatter than that relative to the total gas (n_Htot = 2.59 +- 0.05). [abridged] | Rapid numerical solutions for the Mukhanov-Sasaki equation: We develop a novel technique for numerically computing the primordial power
spectra of comoving curvature perturbations. By finding suitable analytic
approximations for different regions of the mode equations and stitching them
together, we reduce the solution of a differential equation to repeated matrix
multiplication. This results in a wavenumber-dependent increase in speed which
is orders of magnitude faster than traditional approaches at intermediate and
large wavenumbers. We demonstrate the method's efficacy on the challenging case
of a stepped quadratic potential with kinetic dominance initial conditions. |
Sparse Inpainting and Isotropy: Sparse inpainting techniques are gaining in popularity as a tool for
cosmological data analysis, in particular for handling data which present
masked regions and missing observations. We investigate here the relationship
between sparse inpainting techniques using the spherical harmonic basis as a
dictionary and the isotropy properties of cosmological maps, as for instance
those arising from cosmic microwave background (CMB) experiments. In
particular, we investigate the possibility that inpainted maps may exhibit
anisotropies in the behaviour of higher-order angular polyspectra. We provide
analytic computations and simulations of inpainted maps for a Gaussian
isotropic model of CMB data, suggesting that the resulting angular trispectrum
may exhibit small but non-negligible deviations from isotropy. | Limits on spin-dependent WIMP-nucleon cross section obtained from the
complete LUX exposure: We present experimental constraints on the spin-dependent WIMP-nucleon
elastic cross sections from the total 129.5 kg-year exposure acquired by the
Large Underground Xenon experiment (LUX), operating at the Sanford Underground
Research Facility in Lead, South Dakota (USA). A profile likelihood ratio
analysis allows 90% CL upper limits to be set on the WIMP-neutron (WIMP-proton)
cross section of $\sigma_n$ = 1.6$\times 10^{-41}$ cm$^{2}$ ($\sigma_p$ =
5$\times 10^{-40}$ cm$^{2}$) at 35 GeV$c^{-2}$, almost a sixfold improvement
over the previous LUX spin-dependent results. The spin-dependent WIMP-neutron
limit is the most sensitive constraint to date. |
Transverse Sizes of CIV Absorption Systems Measured from Multiple QSO
Sightlines: We present tomography of the circum-galactic metal distribution at redshift
1.7 to 4.5 derived from echellete spectroscopy of binary quasars. We find CIV
systems at similar redshifts in paired sightlines more often than expected for
sightline-independent redshifts. As the separation of the sightlines increases
from 36 kpc to 907 kpc, the amplitude of this clustering decreases. At the
largest separations, the CIV systems cluster similar to Lyman-break galaxies
(Adelberger et al. 2005a). The CIV systems are significantly less correlated
than these galaxies, however, at separations less than R_1 ~ 0.42 +/- 0.15 h-1
comoving Mpc. Measured in real space, i.e., transverse to the sightlines, this
length scale is significantly smaller than the break scale estimated from the
line-of-sight correlation function in redshift space (Scannapieco et al.
2006a). Using a simple model, we interpret the new real-space measurement as an
indication of the typical physical size of enriched regions. We adopt this size
for enriched regions and fit the redshift-space distortion in the line-of-sight
correlation function. The fitted velocity kick is consistent with the peculiar
velocity of galaxies as determined by the underlying mass distribution and
places an upper limit on the outflow (or inflow) speed of metals. The implied
time scale for dispersing metals is larger than the typical stellar ages of
Lyman-break galaxies (Shapley et al. 2001), and we argue that enrichment by
galaxies at z > 4.3 played a greater role in dispersing metals. To further
constrain the growth of enriched regions, we discuss empirical constraints on
the evolution of the CIV correlation function with cosmic time. This study
demonstrates the potential of tomography for measuring the metal enrichment
history of the circum-galactic medium. | Real-time cosmography with redshift derivatives: The drift in the redshift of objects passively following the cosmological
expansion has long been recognized as a key model-independent probe of
cosmology. Here, we study the cosmological relevance of measurements of time or
redshift derivatives of this drift, arguing that the combination of first and
second redshift derivatives is a powerful test of the $\Lambda$CDM cosmological
model. In particular, the latter can be obtained numerically from a set of
measurements of the drift at different redshifts. We show that, in the
low-redshift limit, a measurement of the derivative of the drift can provide a
constraint on the jerk parameter, which is $j=1$ for flat $\Lambda$CDM, while
generically $j\neq1$ for other models. We emphasize that such a measurement is
well within the reach of the ELT-HIRES and SKA Phase 2 array surveys. |
General Modified Gravity With 21cm Intensity Mapping: Simulations and
Forecast: Line intensity mapping opens up a new and exciting window for probing
cosmology and fundamental physics during the Epoch of Reionisation, extending
to redshifts previously untested by galaxy surveys. The power spectra of these
line fluctuations are a promising tool to test gravity over a large range of
scales and redshifts. We simulate cosmological volumes of 21cm fluctuations in
general parametrisations of modified gravity, in order to calculate the
corresponding power spectra, where additional parameters are the initial
condition of matter perturbations $\alpha$ and the scale-dependent modified
gravity parameter $Y$ (also known as $G_\mathrm{eff}$) that measures deviations
from GR in the Poisson equation. We show the impact of these model-independent
modifications of gravity, to either delay or expedite reionisation. For the
21cm intensity mapping survey to be performed by the SKA mission, we forecast
the ability of line intensity mapping to constrain the parameters $Y$ and
$\alpha$ at redshifts $z=6-11$, where $Y$ is assumed constant during this epoch
(but without requiring constancy at all times). In our most conservative
scenario, the $Y$ parameter can be constrained at the tens of percent level,
while for improved modelling of foregrounds as well as of the (mildly)
non-linear regime, up to sub-percent level constraints are attainable. We show
the impact of jointly estimating reionisation model parameters and
corresponding parameter correlations, as well as of foreground removal. We
note, that tomography is crucial to break degeneracies and for constraints not
to degrade significantly when adding reionisation model parameters, with most
constraining power coming from the redshift bins $z=7-10$ where the shape of
the 21cm power spectrum is evolving fastest. | Star formation in M33 (HerM33es): Within the key project "Herschel M33 extended survey" (HerM33es), we are
studying the physical and chemical processes driving star formation and
galactic evolution in the nearby galaxy M33, combining the study of local
conditions affecting individual star formation with properties only becoming
apparent on global scales. Here, we present recent results obtained by the
HerM33es team. Combining Spitzer and Herschel data ranging from 3.6um to 500um,
along with HI, Halpha, and GALEX UV data, we have studied the dust at high
spatial resolutions of 150pc, providing estimators of the total infrared (TIR)
brightness and of the star formation rate. While the temperature of the warm
dust at high brightness is driven by young massive stars, evolved stellar
populations appear to drive the temperature of the cold dust. Plane-parallel
models of photon dominated regions (PDRs) fail to reproduce fully the [CII],
[OI], and CO maps obtained in a first spectroscopic study of one 2'x2'
subregion of M33, located on the inner, northern spiral arm and encompassing
the HII region BCLMP302. |
Mid-Infrared Selection of Active Galactic Nuclei with the Wide-Field
Infrared Survey Explorer. II. Properties of WISE-Selected Active Galactic
Nuclei in the NDWFS Boötes Field: Stern et al.(2012) presented a study of WISE selection of AGN in the 2 deg^2
COSMOS field, finding that a simple criterion W1-W2>=0.8 provides a highly
reliable and complete AGN sample for W2<15.05, where the W1 and W2 passbands
are centered at 3.4 and 4.6 microns, respectively. Here we extend this study
using the larger 9 deg^2 NOAO Deep Wide-Field Survey Bootes field which also
has considerably deeper WISE observations than the COSMOS field, and find that
this simple color-cut significantly loses reliability at fainter fluxes. We
define a modified selection criterion combining the W1-W2 color and the W2
magnitude to provide highly reliable or highly complete AGN samples for fainter
WISE sources. In particular, we define a color-magnitude cut that finds 130+/-4
deg^-2 AGN candidates for W2<17.11 with 90% reliability. Using the extensive UV
through mid-IR broad-band photometry available in this field, we study the
spectral energy distributions of WISE AGN candidates. As expected, the WISE AGN
selection is biased towards objects where the AGN dominates the bolometric
luminosity output, and that it can identify highly obscured AGN. We study the
distribution of reddening in the AGN sample and discuss a formalism to account
for sample incompleteness based on the step-wise maximum-likelihood method of
Efstathiou et al.(1988). The resulting dust obscuration distributions depend
strongly on AGN luminosity, consistent with the trend expected for a Simpson
(2005) receding torus. At L_AGN~3x10^44 erg/s, 29+/-7% of AGN are observed as
Type 1, while at ~4x10^45 erg/s the fraction is 64+/-13%. The distribution of
obscuration values suggests that dust in the torus is present as both a diffuse
medium and in optically thick clouds. | Modeling Increased Metal Production in Galaxy Clusters with
Pair-Instability Supernovae: Galaxy clusters contain much more metal per star, typically 3 times as much,
than is produced in normal galaxies. We set out to determine what changes are
needed to the stellar mass function and supernovae rates to account for this
excess metal. In particular, we vary the Type Ia supernovae rate, IMF slope,
upper and lower mass cutoffs, and the merger rate of massive stars. We then use
existing simulation results for metal production from AGB stars, Type Ia SNe
and core-collapse SNe to calculate the total amount of each element produced
per solar mass of star formation. For models with very massive stars, we also
include metal production from pair-instability supernovae (PISNe).We find that
including PISNe makes it much easier to increase the amount of metal produced
per stellar mass. Therefore a separate population of high-mass stars is not
needed to produce the high amounts of metal found in galaxy clusters. We also
find that including at least some PISNe increases the abundance of
intermediate-mass elements relative to both oxygen and iron, consistent with
observations of ICM abundances. |
Comparing galactic satellite properties in hydrodynamical and Nbody
simulations: In this work, we examine the different properties of galactic satellites in
hydrodynamical and pure dark matter simulations. We use three pairs of
simulations (collisional and collision-less) starting from identical initial
conditions. We concentrate our analysis on pairs of satellites in the hydro and
Nbody runs that form from the same Lagrangian region. We look at the radial
positions, mass loss as a function of time and orbital parameters of these
"twin" satellites. We confirm an overall higher radial density of satellites in
the hydrodynamical runs, but find that trends in the mass loss and radial
position of these satellites in the inner and outer region of the parent halo
differ from the pure dark matter case. In the outskirts of the halo (~70% of
the virial radius) satellites experience a stronger mass loss and higher
dynamical friction in pure dark matter runs. The situation is reversed in the
central region of the halo, where hydrodynamical satellites have smaller
apocenter distances and suffer higher mass stripping. We partially ascribe this
bimodal behaviour to the delayed infall time for hydro satellites, which on
average cross the virial radius of the parent halo 0.7 Gyrs after their dark
matter twins. Finally, we briefly discuss the implications of the different set
of satellite orbital parameters and mass loss rates in hydrodynamical
simulations within the context of thin discs heating and destruction. | Is dark matter with long-range interactions a solution to all
small-scale problems of ΛCDM cosmology?: The cold dark matter (DM) paradigm describes the large-scale structure of the
universe remarkably well. However, there exists some tension with the observed
abundances and internal density structures of both field dwarf galaxies and
galactic satellites. Here, we demonstrate that a simple class of DM models may
offer a viable solution to all of these problems simultaneously. Their key
phenomenological properties are velocity-dependent self-interactions mediated
by a light vector messenger and thermal production with much later kinetic
decoupling than in the standard case. |
Self-calibrating BAO measurements in the presence of Small Displacement
Interlopers: Baryon Acoustic Oscillation (BAO) observations offer a robust method for
measuring cosmological expansion. However, the BAO signal in a sample of
galaxies can be diluted and shifted by interlopers - galaxies that have been
assigned the wrong redshifts. Because of the slitless spectroscopic method
adopted by the Roman and Euclid space telescopes, the galaxy samples resulting
from single line detections will have relatively high fractions of interloper
galaxies. Interlopers with a small displacement between true and false redshift
have the strongest effect on the measured clustering. In order to model the BAO
signal, the fraction of such interlopers and their clustering need to be
accurately known. We introduce a new method to self-calibrate these quantities
by shifting the contaminated sample towards or away from us along the line of
sight by the interloper offset, and measuring the cross-correlations between
these shifted samples. The contributions from the different components are
shifted in scale in this cross-correlation compared to the auto-correlation of
the contaminated sample, enabling the decomposition and extraction of the
component terms. We demonstrate the application of the method using numerical
simulations and show that an unbiased BAO measurement can be extracted. Unlike
previous attempts to model the effects of contaminants, self-calibration allows
us to make fewer assumptions about the form of the contaminants such as their
bias. | Simulations of solitonic core mergers in ultra-light axion dark matter
cosmologies: Using three-dimensional simulations, we study the dynamics and final
structure of merging solitonic cores predicted to form in ultra-light axion
dark matter halos. The classical, Newtonian equations of motion of a
self-gravitating scalar field are described by the Schr\"odinger-Poisson
equations. We investigate mergers of ground state (boson star) configurations
with varying mass ratios, relative phases, orbital angular momenta and initial
separation with the primary goal to understand the mass loss of the emerging
core by gravitational cooling. Previous results showing that the final density
profiles have solitonic cores and NFW-like tails are confirmed. In binary
mergers, the final core mass does not depend on initial phase difference or
angular momentum and only depends on mass ratio, total initial mass, and total
energy of the system. For non-zero angular momenta, the otherwise spherical
cores become rotating ellipsoids. The results for mergers of multiple cores are
qualitatively identical. |
Importance of upgraded energy reconstruction for direct dark matter
searches with liquid xenon detectors: The usual nuclear recoil energy reconstruction employed by liquid xenon dark
matter search experiments relies only on the primary scintillation photon
signal. Energy reconstruction based on both the photon and electron signals
yields a more accurate representation of search results. For a dark matter
particle mass m~10 GeV, a nuclear recoil from a scattering event is more likely
to be observed in the lower left corner of the typical search box, rather than
near the nuclear recoil calibration centroid. In this region of the search box,
the actual nuclear recoil energies are smaller than the usual energy scale
suggests, by about a factor x2. Recent search results from the XENON100
experiment are discussed in light of these considerations. | A search for cosmological anisotropy using the Lyman alpha forest from
SDSS quasar spectra: The Cosmological Principle, the combined assumptions of cosmological isotropy
and homogeneity, underpins the standard model of Big Bang cosmology with which
we interpret astronomical observations. A new test of isotropy over the
redshift range $2<z<4$ and across large angular scales on the sky is presented.
We use the cosmological distribution of neutral hydrogen, as probed by the
Ly$\alpha$ forest seen towards distant quasars. The Sloan Digital Sky Survey
provides the largest dataset of quasar spectra available to date. We use
combined information from Data Releases 12 and 14 to select a sample of 142,661
quasars most suitable for this purpose. The scales covered by the data extend
beyond post-inflation causality scales, thus probing initial conditions in the
early universe. We identify significant spatially correlated systematic effects
that can emulate cosmological anisotropy. Once these systematics have been
accounted for, the data are found to be consistent with isotropy, providing an
important independent check on the standard model, consistent with results from
cosmic microwave background data. |
Testing theories in barred spiral galaxies: According to one version of the recently proposed "manifold" theory that
explains the origin of spirals and rings in relation to chaotic orbits,
galaxies with stronger bars should have a higher spiral arms pitch angle when
compared to galaxies with weaker bars. A sub-sample of barred-spiral galaxies
in the Ohio State University Bright Galaxy Survey, was used to analyze the
spiral arms pitch angle. These were compared with bar strengths taken from the
literature. It was found that the galaxies in which the spiral arms maintain a
logarithmic shape for more than 70$\degr$ seem to corroborate the predicted
trend. | The UVES Large Program for Testing Fundamental Physics II: Constraints
on a Change in μ Towards Quasar HE 0027-1836: We present an accurate analysis of the H2 absorption lines from the zabs ~
2.4018 damped Ly{\alpha} system towards HE 0027-1836 observed with the Very
Large Telescope Ultraviolet and Visual Echelle Spectrograph (VLT/UVES) as a
part of the European Southern Observatory Large Programme "The UVES large
programme for testing fundamental physics" to constrain the variation of
proton-to-electron mass ratio, {\mu} = mp/me. We perform cross-correlation
analysis between 19 individual exposures taken over three years and the
combined spectrum to check the wavelength calibration stability. We notice the
presence of a possible wavelength dependent velocity drift especially in the
data taken in 2012. We use available asteroids spectra taken with UVES close to
our observations to confirm and quantify this effect. We consider single and
two component Voigt profiles to model the observed H2 absorption profiles. We
use both linear regression analysis and Voigt profile fitting where
{\Delta}{\mu}/{\mu} is explicitly considered as an additional fitting
parameter. The two component model is marginally favored by the statistical
indicators and we get {\Delta}{\mu}/{\mu} = (-2.5 +/- 8.1(stat) +/- 6.2(sys))
ppm. When we apply the correction to the wavelength dependent velocity drift we
find {\Delta}{\mu}/{\mu} = (-7.6 +/- 8.1(stat) +/- 6.3(sys)) ppm. It will be
important to check the extent to which the velocity drift we notice in this
study is present in UVES data used for previous {\Delta}{\mu}/{\mu}
measurements. |
Thermal relics as hot, warm and cold dark matter in power-law $f(R)$
gravity: We investigate the thermal relics as hot, warm and cold dark matter in
$\mathscr{L}=\varepsilon^{2-2\beta}R^\beta+{16\pi}m_{\text{Pl}}^{-2}\mathscr{L}_m$
gravity, where $\varepsilon$ is a constant balancing the dimension of the field
equation, and $1<\beta<(4+\sqrt{6})/5$ for the positivity of energy density and
temperature. If light neutrinos serve as hot/warm relics, the entropic number
of statistical degrees of freedom $g_{*s}$ at freeze-out and thus the predicted
fractional energy density $\Omega_\psi h^2$ are $\beta-$dependent, which
relaxes the standard mass bound $\Sigma m_\nu$. For cold relics, by exactly
solve the simplified Boltzmann equation in both relativistic and
nonrelativistic regimes, we show that the Lee-Weinberg bound for the mass of
heavy neutrinos can be considerably relaxed, and the 'WIMP miracle" for weakly
interacting massive particles (WIMPs) gradually invalidates as $\beta$ deviates
from $\beta=1^+$. The whole framework reduces to become that of GR in the limit
$\beta\to 1^+$. | The History of Star Forming Galaxies and their Environment as seen by
Spitzer: A Review: The advent of the Spitzer Space Telescope has revolutionized our
understanding of the history of star formation and galaxy mass assembly in the
Universe. The tremendous leap in sensitivity from previous mid-to-far IR
missions has allowed Spitzer to perform deeper, and wider, surveys than
previously possible at these wavelengths. In this brief review I highlight some
of the key results to come out of these surveys, and the implications these
have for current models of galaxy formation and evolution. |
Can the quasi-molecular mechanism of recombination decrease the Hubble
tension?: In the recently suggested non-standard, quasi-molecular mechanism of
recombination, the presence of neighboring proton increases the ionization
energy and decreases the final recombination rate of hydrogen. Both these two
effects can lead to the larger value of the present expansion rate of the
universe obtained using CMB data and standard cosmological model, and thus are
able to reduce or resolve the Hubble tension problem. We note also that due to
the quasi-molecular channel the recombination began earlier, what potentially
can solve the sigma-eight tension, since the CMB-predicted value of the late
matter density will be decreased. | Low Ionization Emission Lines in Quasars: Clues from OI 8446 and the
CaII Triplet: The formation of low emission lines in quasars and active galactic nuclei is
still an open issue. Aided by the organizing power of the 4D eigenvector 1
scheme, we review basic developments since the 1980s, devoting special
attention to the CaII IR triplet and the OI 8446 emission lines. Coverage of
these lines is cumbersome since they are shifted in an inconvenient IR domain
already at modest redshifts (~ 0.2). Their detection is also difficult since
they are faint and often buried in the Ca II absorption of the host galaxy. We
discuss how these lines can provide unambiguous constraints on the physical
conditions of the broad line emitting regions of quasars when detected in
emission, and summarise preliminary results for a sample of luminous,
intermediate redshift quasars. |
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