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Probing Quintessence using BAO imprint on the cross-correlation of weak
lensing and post-reionization HI 21 cm signal: In this work we investigate the possibility of constraining a thawing
Quintessence scalar field model for dark energy. We propose using the imprint
of baryon acoustic oscillation (BAO) on the cross-correlation of
post-reionization 21-cm signal and galaxy weak lensing convergence field to
tomographically measure the angular diameter distance $D_A(z)$ and the Hubble
parameter $H(z)$. The projected errors in these quantities are then used to
constrain the Quintessence model parameters. We find that independent $600$hrs
radio interferometric observation at four observing frequencies $916 $MHz,
$650$ MHz, $520$ MHz and $430 $MHz with a SKA-1-Mid like radio telescope in
cross-correlation with a deep weak lensing survey covering half the sky may
measure the binned $D_A$ and $H$ at a few percent level of sensitivity. The
Monte Carlo analysis for a power law thawing Quintessence model gives the
$1-\sigma$ marginalized bounds on the initial slope $\lambda_i$,dark energy
density parameter $\Omega_{\phi 0}$ and the shape of the potential $\Gamma$ at
8.63%, 10.08% and 9.75% respectively. The constraints improve to 7.66%, 4.39%
and 5.86% respectively when a joint analysis with SN and other probes is
performed. | On the effect of angular momentum on the prompt cusp formation via the
gravitational collapse: In this work, we extend the model proposed by White concerning the
post-collapse evolution of density peaks while considering the role of angular
momentum. On a timescale smaller than the peak collapse, $t_{0}$, the inner
regions of the peak reach the equilibrium forming a cuspy profile, as in
White's paper, but the power-law density profile is flatter, namely $\rho
\propto r^{-1.52}$, using the specific angular momentum $J$ obtained in
theoretical models of how it evolves in CDM universes, namely $J \propto
M^{2/3}$. The previous result shows how angular momentum influences the slope
of the density profile, and how a slightly flatter profile obtained in
high-resolution numerical simulations, namely $\rho \propto r^{\alpha}$,
$(\alpha \simeq -1.5)$ can be reobtained. Similarly to simulations, in our
model adiabatic contraction was not taken into account. This means that more
comprehensive simulations could give different values for the slope of the
density profile, similar to an improvement of our model. |
Modified Dust and the Small Scale Crisis in CDM: At large scales and for sufficiently early times, dark matter is described as
a pressureless perfect fluid---dust---non-interacting with Standard Model
fields. These features are captured by a simple model with two scalars: a
Lagrange multiplier and another playing the role of the velocity potential.
That model arises naturally in some gravitational frameworks, e.g., the mimetic
dark matter scenario. We consider an extension of the model by means of higher
derivative terms, such that the dust solutions are preserved at the background
level, but there is a non-zero sound speed at the linear level. We associate
this {\it Modified Dust} with dark matter, and study the linear evolution of
cosmological perturbations in that picture. The most prominent effect is the
suppression of their power spectrum for sufficiently large cosmological
momenta. This can be relevant in view of the problems that cold dark matter
faces at sub-galactic scales, e.g., the missing satellites problem. At even
shorter scales, however, perturbations of Modified Dust are enhanced compared
to the predictions of more common particle dark matter scenarios. This is a
peculiarity of their evolution in radiation dominated background. We also
briefly discuss clustering of Modified Dust. We write the system of equations
in the Newtonian limit, and sketch the possible mechanism which could prevent
the appearance of caustic singularities. The same mechanism may be relevant in
light of the core-cusp problem. | A Zeldovich reconstruction method for measuring redshift space
distortions using cosmic voids: Redshift space distortions (RSD) in the void-galaxy correlation $\xi^s$
provide information on the linear growth rate of structure in low density
environments. Accurate modelling of these RSD effects can also allow the use of
voids in competitive Alcock-Paczynski measurements. Linear theory models of
$\xi^s$ are able to provide extremely good descriptions of simulation data on
all scales provided the real space void positions are known. However, by
reference to simulation data we demonstrate the failure of the assumptions
implicit in current models of $\xi^s$ for voids identified directly in redshift
space, as would be simplest using real observational data. To overcome this
problem we instead propose using a density-field reconstruction method based on
the Zeldovich approximation to recover the real space void positions from
redshift space data. We show that this recovers the excellent agreement between
theory and data for $\xi^s$. Performing the reconstruction requires an input
cosmological model so, to be self-consistent, we have to perform reconstruction
for every model to be tested. We apply this method to mock galaxy and void
catalogues in the Big MultiDark $N$-body simulation and consistently recover
the fiducial growth rate to a precision of $3.4\%$ using the simulation volume
of $(2.5\;h^{-1}\mathrm{Gpc})^3$. |
Lyman-$α$ Constraints on Cosmic Heating from Dark Matter
Annihilation and Decay: We derive new constraints on models of decaying and annihilating dark matter
(DM) by requiring that the energy injected into the intergalactic medium (IGM)
not overheat it at late times, when measurements of the Lyman-$\alpha$ forest
constrain the IGM temperature. We improve upon previous analyses by using the
recently developed $\texttt{DarkHistory}$ code package, which self-consistently
takes into account additional photoionization and photoheating processes due to
reionization and DM sources. Our constraints are robust to the uncertainties of
reionization and competitive with leading limits on sub-GeV DM that decays
preferentially to electrons. | Dark energy and Equivalence Principle constraints from astrophysical
tests of the stability of the fine-structure constant: Astrophysical tests of the stability of fundamental couplings, such as the
fine-structure constant $\alpha$, are becoming an increasingly powerful probe
of new physics. Here we discuss how these measurements, combined with local
atomic clock tests and Type Ia supernova and Hubble parameter data, constrain
the simplest class of dynamical dark energy models where the same degree of
freedom is assumed to provide both the dark energy and (through a dimensionless
coupling, $\zeta$, to the electromagnetic sector) the $\alpha$ variation.
Specifically, current data tightly constrains a combination of $\zeta$ and the
present dark energy equation of state $w_0$. Moreover, in these models the new
degree of freedom inevitably couples to nucleons (through the $\alpha$
dependence of their masses) and leads to violations of the Weak Equivalence
Principle. We obtain indirect bounds on the E\"otv\"os parameter $\eta$ that
are typically stronger than the current direct ones. We discuss the
model-dependence of our results and briefly comment on how the forthcoming
generation of high-resolution ultra-stable spectrographs will enable
significantly tighter constraints. |
Excursion set peaks: a self-consistent model of dark halo abundances and
clustering: We describe how to extend the excursion set peaks framework so that its
predictions of dark halo abundances and clustering can be compared directly
with simulations. These extensions include: a halo mass definition which uses
the TopHat filter in real space; the mean dependence of the critical density
for collapse delta_c on halo mass m; and the scatter around this mean value.
All three of these are motivated by the physics of triaxial rather than
spherical collapse. A comparison of the resulting mass function with N-body
results shows that, if one uses delta_c(m) and its scatter as determined from
simulations, then all three are necessary ingredients for obtaining ~10%
accuracy. E.g., assuming a constant value of delta_c with no scatter, as
motivated by the physics of spherical collapse, leads to many more massive
halos than seen in simulations. The same model is also in excellent agreement
with N-body results for the linear halo bias, especially at the high mass end
where the traditional peak-background split argument applied to the mass
function fit is known to underpredict the measured bias by ~10%. In the
excursion set language, our model is about walks centered on special positions
(peaks) in the initial conditions -- we discuss what it implies for the usual
calculation in which all walks contribute to the statistics. | Preferred axis of CMB parity asymmetry in the masked maps: Both WMAP and Planck data show a significant odd-multipole preference in the
large scales of the cosmic microwave background (CMB) temperature anisotropies.
If this pattern originates from cosmological effects, then it can be considered
a crucial clue for a violation in the cosmological principle. By defining
various direction dependent statistics in the full-sky Planck 2015 maps (see,
for instance, Naselsky et al. (2012); W. Zhao (2014)), we found that the CMB
parity asymmetry has a preferred direction, which is independent of the choices
of the statistics. In particular, this preferred axis is strongly aligned with
those in the CMB quadrupole and octopole, as well as that in the CMB kinematic
dipole, which hints to their non-cosmological origin. In realistic
observations, the foreground residuals are inevitable, and should be properly
masked out in order to avoid possible misinterpretation of the results. In this
paper, we extend our previous analyses to the masked Planck 2015 data. By
defining a similar direction dependent statistic in the masked map, we find a
preferred direction of the CMB parity asymmetry, in which the axis also
coincides with that found in the full-sky analysis. Therefore, our conclusions
on the CMB parity violation and its directional properties are confirmed. |
The Dark Side of Reionization: Probing Cooling in the Early Universe: Probing the growth of structure from the epoch of hydrogen recombination to
the formation of the first stars and galaxies is one of the most important
uncharted areas of observational cosmology. Far-IR spectroscopy covering
$\lambda$ 100-500 microns from space, and narrow partial transmission
atmospheric bands available from the ground, opens up the possibility of
probing the molecular hydrogen and metal fine-structure lines from primordial
clouds from which the first stars and galaxies formed at 6 < z $<$ 15. Building
on Spitzer observations of unexpectedly powerful H2 emission from shocks, we
argue that next-generation far-IR space telescopes may open a new window into
the main cloud cooling processes and feedback effects which characterized this
vital, but unexplored epoch. Without this window, we are essential blind to the
dominant cloud cooling which inevitably led to star formation and cosmic
reionization. | Revisiting oldest stars as cosmological probes: new constraints on the
Hubble constant: Despite the tremendous advance of observational cosmology, the value of the
Hubble constant ($H_0$) is still controversial (the so called ``Hubble
tension'') because of the inconsistency between local/late-time measurements
and those derived from the cosmic microwave background. As the age of the
Universe is very sensitive to $H_0$, we explored whether the present-day oldest
stars could place independent constraints on the Hubble constant. To this
purpose, we selected from the literature the oldest objects (globular clusters,
stars, white dwarfs, ultra-faint and dwarf spheroidal galaxies) with accurate
age estimates. Adopting a conservative prior on their formation redshifts ($11
\leq z_{\rm f} \leq 30$) and assuming $\Omega_{\rm M} = 0.3 \pm 0.02$, we
developed a method based on Bayesian statistics to estimate the Hubble
constant. We selected the oldest objects ($>13.3$ Gyr) and estimated $H_0$ both
for each of them individually and for the average ages of homogeneous
subsamples. Statistical and systematic uncertainties were properly taken into
account. The constraints based on individual ages indicate that $H_0<70.6$
km/s/Mpc when selecting the most accurate estimates. If the ages are averaged
and analyzed independently for each subsample, the most stringent constraints
imply $H_0<73.0$ with a probability of 90.3% and errors around 2.5 km/s/Mpc. We
also constructed an ``accuracy matrix'' to assess how the constraints on $H_0$
become more stringent with further improvements in the accuracy of stellar ages
and $\Omega_{\rm M}$. The results show the high potential of the oldest stars
as independent and competitive cosmological probes not only limited to the
Hubble constant. |
Disentangling star formation and merger growth in the evolution of
Luminous Red Galaxies: We introduce a novel technique for empirically understanding galaxy
evolution. We use empirically determined stellar evolution models to predict
the past evolution of the Sloan Digital Sky Survey (SDSS-II) Luminous Red
Galaxy (LRG) sample without any a-priori assumption about galaxy evolution. By
carefully contrasting the evolution of the predicted and observed number and
luminosity densities we test the passive evolution scenario for galaxies of
different luminosity, and determine minimum merger rates. We find that the LRG
population is not purely coeval, with some of galaxies targeted at z<0.23 and
at z>0.34 showing different dynamical growth than galaxies targeted throughout
the sample. Our results show that the LRG population is dynamically growing,
and that this growth must be dominated by the faint end. For the most luminous
galaxies, we find lower minimum merger rates than required by previous studies
that assume passive stellar evolution, suggesting that some of the dynamical
evolution measured previously was actually due to galaxies with non-passive
stellar evolution being incorrectly modelled. Our methodology can be used to
identify and match coeval populations of galaxies across cosmic times, over one
or more surveys. | Constant-rate inflation: primordial black holes from conformal weight
transitions: Constant-rate inflation, including ultra-slow-roll as a special case, has
been widely applied to the formation of primordial black holes with significant
deviation from the standard slow-roll conditions at both the growing and
decaying phases of the power spectrum. We derive analytic solutions for the
curvature perturbations with respect to the late-time scaling dimensions
(conformal weights) constrained by the dilatation symmetry of the de Sitter
background and show that the continuity of conformal weights across different
rolling phases is protected by the adiabatic condition of the inflaton
perturbation. The temporal excitation of subleading states (with the
next-to-lowest conformal weights), recorded as the "steepest growth" of the
power spectrum, is triggered by the entropy production in the transition from
slow-roll to constant-rate phases. |
On the nature of the progenitors of three type II-P supernovae: 2004et,
2006my and 2006ov: The pre-explosion observations of the type II-P supernovae 2006my, 2006ov and
2004et, are re-analysed. In the cases of supernovae 2006my and 2006ov we argue
that the published candidate progenitors are not coincident with their
respective supernova sites in pre-explosion Hubble Space Telescope
observations. We therefore derive upper luminosity and mass limits for the
unseen progenitors of both these supernovae, assuming they are red supergiants:
2006my (log L/Lsun = 4.51; mass < 13Msun) and 2006ov (log L/Lsun = 4.29; mass <
10Msun). In the case of supernova 2004et we show that the yellow-supergiant
progenitor candidate, originally identified in Canada France Hawaii Telescope
images, is still visible ~3 years post-explosion in observations from the
William Herschel Telescope. High-resolution Hubble Space Telescope and Gemini
(North) adaptive optics late-time imagery reveal that this source is not a
single yellow supergiant star, but rather is resolved into at least three
distinct sources. We report the discovery of the unresolved progenitor as an
excess of flux in pre-explosion Isaac Newton Telescope i'-band imaging.
Accounting for the late-time contribution of the supernova using published
optical spectra, we calculate the progenitor photometry as the difference
between the pre- and post-explosion, ground-based observations. We find the
progenitor was most likely a late K to late M-type supergiant of 8 +5/-1 Msun.
In all cases we conclude that future, high-resolution observations of the
supernova sites will be required to confirm these results. | Ages of M33 Star Clusters Based on the HST/WFPC2 Photometry: We present a result of age estimation for star clusters in M33. We obtain
color-magnitude diagrams (CMDs) of resolved stars in 242 star clusters from the
HST/WFPC2 images. We estimate ages of 100 star clusters among these, by fitting
the Padova theoretical isochrones to the observational CMDs. Age distribution
of the star clusters shows a dominant peak at log(t) ~ 7.8. Majority of star
clusters are younger than log(t) = 9.0, while ten star clusters are older than
log(t) ~ 9.0. There are few clusters younger than log(t) = 7 in this study,
which is in contrast with the results based on the integrated photometry of
star clusters in the previous studies. Radial distribution of the cluster ages
shows that young to intermediate-age clusters are found from the center to the
outer region, while old clusters are distributed farther from M33 center. We
discuss briefly the implication of the results with regard to the formation of
M33 cluster system. |
Distinguishing Dark Matter from Unresolved Point Sources in the Inner
Galaxy with Photon Statistics: Data from the Fermi Large Area Telescope suggests that there is an extended
excess of GeV gamma-ray photons in the Inner Galaxy. Identifying potential
astrophysical sources that contribute to this excess is an important step in
verifying whether the signal originates from annihilating dark matter. In this
paper, we focus on the potential contribution of unresolved point sources, such
as millisecond pulsars (MSPs). We propose that the statistics of the
photons---in particular, the flux probability density function (PDF) of the
photon counts below the point-source detection threshold---can potentially
distinguish between the dark-matter and point-source interpretations. We
calculate the flux PDF via the method of generating functions for these two
models of the excess. Working in the framework of Bayesian model comparison, we
then demonstrate that the flux PDF can potentially provide evidence for an
unresolved MSP-like point-source population. | Exploring compensated isocurvature perturbations with CMB spectral
distortion anisotropies: We develop a linear perturbation theory for the spectral $y$-distortions of
the cosmic microwave background (CMB). The $y$-distortions generated during the
recombination epoch are usually negligible because the energy transfer due to
the Compton scattering is strongly suppressed at that time, but they can be
significant if there is a considerable amount of compensated isocurvature
perturbation (CIP), which is not tightly constrained from the present CMB
observations. The linear $y$-distortions explicitly depend on the baryon
density fluctuations, therefore $y$ anisotropies can completely resolve the
degeneracy between the baryon isocurvature perturbations and the cold dark
matter ones. This novel method is free from lensing contaminations that can
affect the previous approach to the CIPs based on the nonlinear modulation of
the CMB anisotropies. We compute the cross correlation functions of the
$y$-distortions with the CMB temperature and the $E$ mode polarization
anisotropies. They are sensitive to the correlated CIPs parameterized by
$f'\equiv\mathcal P_{\rm CIP\zeta}/\mathcal P_{\zeta \zeta}$ with $\mathcal
P_{\zeta \zeta}$ and $\mathcal P_{\rm CIP\zeta}$ being the auto correlation of
the adiabatic perturbations and the cross correlation between them and the
CIPs. We investigate how well the $y$ anisotropies will constrain $f'$ in
future observations such as those provided by a PIXIE-like and a PRISM-like
survey, LiteBIRD and a cosmic variance limited (CVL) survey, taking into
account the degradation in constraining power due to the presence of Sunyaev
Zel'dovich effect from galaxy clusters. For example, our forecasts show that it
is possible to achieve an upper limit of $f'< 2 \times 10^{5}$ at 68% C.L. with
LiteBIRD, and $f'<2\times 10^{4}$ with CVL observations. |
Impacts on Cosmological Constraints from Degeneracies: In this paper, we study the degeneracies among several cosmological
parameters in detail and discuss their impacts on the determinations of these
parameters from the current and future observations. By combining the latest
data sets, including type-Ia supernovae "Union2.1" compilation, WMAP seven-year
data and the baryon acoustic oscillations from the SDSS Data Release Seven, we
perform a global analysis to determine the cosmological parameters, such as the
equation of state of dark energy w, the curvature of the universe \Omega_k, the
total neutrino mass \sum{m_\nu}, and the parameters associated with the power
spectrum of primordial fluctuations (n_s, \alpha_s and r). We pay particular
attention on the degeneracies among these parameters and the influences on
their constraints, by with or without including these degeneracies,
respectively. We find that $w$ and \Omega_k or \sum{m_\nu} are strongly
correlated. Including the degeneracies will significantly weaken the
constraints. Furthermore, we study the capabilities of future observations and
find these degeneracies can be broken very well. Consequently, the constraints
of cosmological parameters can be improved dramatically. | Recurring flares from supermassive black hole binaries: implications for
tidal disruption candidates and OJ 287: I discuss the possibility that accreting supermassive black hole (SMBH)
binaries with sub-parsec separations produce periodically recurring luminous
outbursts that interrupt periods of relative quiescence. This hypothesis is
motivated by two characteristics found generically in simulations of binaries
embedded in prograde accretion discs: (i) the formation of a central,
low-density cavity around the binary, and (ii) the leakage of gas into this
cavity, occurring once per orbit via discrete streams on nearly radial
trajectories. The first feature would reduce the emergent optical/UV flux of
the system relative to active galactic nuclei powered by single SMBHs, while
the second can trigger quasiperiodic fluctuations in luminosity. I argue that
the quasiperiodic accretion signature may be much more dramatic than previously
thought, because the infalling gas streams can strongly shock-heat via
self-collision and tidal compression, thereby enhancing viscous accretion. Any
optically thick gas that is circularized about either SMBH can accrete before
the next pair of streams is deposited, fueling transient, luminous flares that
recur every orbit. Due to the diminished flux in between accretion episodes,
such cavity-accretion flares could plausibly be mistaken for the tidal
disruptions of stars in quiescent nuclei. The flares could be distinguished
from tidal disruption events if their quasiperiodic recurrence is observed, or
if they are produced by very massive SMBHs that cannot disrupt solar-type
stars. They may be discovered serendipitously in surveys such as LSST or
eROSITA. I present a heuristic toy model as a proof of concept for the
production of cavity-accretion flares, and generate mock light curves and
specta. I also apply the model to the active galaxy OJ 287, whose production of
quasiperiodic pairs of optical flares has long fueled speculation that it hosts
a SMBH binary. |
Observational constraints on dark energy with a fast varying equation of
state: We place observational constraints on models with the late-time cosmic
acceleration based on a number of parametrizations allowing fast transitions
for the equation of state of dark energy. In addition to the model of Linder
and Huterer where the dark energy equation of state $w$ monotonically grows or
decreases in time, we propose two new parametrizations in which $w$ has an
extremum. We carry out the likelihood analysis with the three parametrizations
by using the observational data of supernovae type Ia, cosmic microwave
background, and baryon acoustic oscillations. Although the transient cosmic
acceleration models with fast transitions can give rise to the total chi square
smaller than that in the $\Lambda$-Cold-Dark-Matter ($\Lambda$CDM) model, these
models are not favored over $\Lambda$CDM when one uses the Akaike information
criterion which penalizes the extra degrees of freedom present in the
parametrizations. | Volume Statistics as a Probe of Large-Scale Structure: We investigate the application of volume statistics to probe the distribution
of underdense regions in the large-scale structure of the Universe. This
statistic measures the distortion of Eulerian volume elements relative to
Lagrangian ones and can be built from tracer particles using tessellation
methods. We apply Voronoi and Delaunay tessellation to study the clustering
properties of density and volume statistics. Their level of shot-noise
contamination is similar, as both methods take into account all available
tracer particles in the field estimator. The tessellation causes a smoothing
effect in the power spectrum, which can be approximated by a constant window
function on large scales. The clustering bias of the volume statistic with
respect to the dark matter density field is determined and found to be
negative. We further identify the Baryon Acoustic Oscillation (BAO) feature in
the volume statistic. Apart from being smoothed out on small scales, the BAO is
present in the volume power spectrum as well, without any systematic bias.
These observations suggest that the exploitation of volume statistics as a
complementary probe of cosmology is very promising. |
Cosmology with Gravitational Lensing: In these lectures I give an overview of gravitational lensing, concentrating
on theoretical aspects, including derivations of some of the important results.
Topics covered include the determination of surface mass densities of
intervening lenses, as well as the statistical analysis of distortions of
galaxy images by general inhomogeneities (cosmic shear), both in 2D projection
on the sky, and in 3D where source distance information is available. 3D mass
reconstruction and the shear ratio test are also considered, and the
sensitivity of observables to Dark Energy is used to show how its equation of
state may be determined using weak lensing. Finally, the article considers the
prospect of testing Einstein's General Relativity with weak lensing, exploiting
the differences in growth rates of perturbations in different models.}
\abstract{In these lectures I give an overview of gravitational lensing,
concentrating on theoretical aspects, including derivations of some of the
important results. Topics covered include the determination of surface mass
densities of intervening lenses, as well as the statistical analysis of
distortions of galaxy images by general inhomogeneities (cosmic shear), both in
2D projection on the sky, and in 3D where source distance information is
available. 3D mass reconstruction and the shear ratio test are also considered,
and the sensitivity of observables to Dark Energy is used to show how its
equation of state may be determined using weak lensing. Finally, the article
considers the prospect of testing Einstein's General Relativity with weak
lensing, exploiting the differences in growth rates of perturbations in
different models. | On the Possibility of Anisotropic Curvature in Cosmology: In addition to shear and vorticity a homogeneous background may also exhibit
anisotropic curvature. Here a class of spacetimes is shown to exist where the
anisotropy is solely of the latter type, and the shear-free condition is
supported by a canonical, massless 2-form field. Such spacetimes possess a
preferred direction in the sky and at the same time a CMB which is isotropic at
the background level. A distortion of the luminosity distances is derived and
used to test the model against the CMB and supernovae (using the Union
catalog), and it is concluded that the latter exhibit a higher-than-expected
dependence on angular position. It is shown that future surveys could detect a
possible preferred direction by observing ~ 20 / (\Omega_{k0}^2) supernovae
over the whole sky. |
N-Body Simulations of DGP and Degravitation Theories: We perform N-body simulations of theories with infinite-volume extra
dimensions, such as the Dvali-Gabadadze-Porrati (DGP) model and its
higher-dimensional generalizations, where 4D gravity is mediated by massive
gravitons. The longitudinal mode of these gravitons mediates an extra scalar
force, which we model as a density-dependent modification to the Poisson
equation. This enhances gravitational clustering, particularly on scales that
have undergone mild nonlinear processing. While the standard non-linear fitting
algorithm of Smith et al. overestimates this power enhancement on non-linear
scales, we present a modified fitting formula that offers a remarkably good fit
to our power spectra. Due to the uncertainty in galaxy bias, our results are
consistent with precision power spectrum determinations from galaxy redshift
surveys, even for graviton Compton wavelengths as small as 300 Mpc. Our model
is sufficiently general that we expect it to capture the phenomenology of a
wide class of related higher-dimensional gravity scenarios. | The Impact of Feedback on Disk Galaxy Scaling Relations: We use a disk formation model to study the effects of galactic outflows
(a.k.a. feedback) on the rotation velocity - stellar mass - disk size, gas
fraction - stellar mass, and gas phase metalicity - stellar mass scaling
relations of disk galaxies. We show that models without outflows are unable to
explain these scaling relations, having both the wrong slopes and
normalization. The problem can be traced to the model galaxies having too many
baryons. Models with outflows can solve this "over-cooling" problem by removing
gas before it has time to turn into stars. Models with both momentum and energy
driven winds can reproduce the observed scaling relations. However, these
models predict different slopes which, with better observations, may be used to
discriminate between these models. |
Mass assembly in quiescent and star-forming galaxies since z=4 from
UltraVISTA: We estimate the galaxy stellar mass function and stellar mass density for
star-forming and quiescent galaxies with 0.2<z<4. We construct a deep K<24
sample of 220000 galaxies selected using the UltraVISTA DR1 data release. Our
analysis is based on precise 30-band photometric redshifts. By comparing these
photometric redshifts with 10800 spectroscopic redshifts from the zCOSMOS
bright and faint surveys, we find a precision of sigma(dz/(1+z))=0.008 at
i<22.5 and sigma(dz/(1+zs))=0.03 at 1.5<z<4. We derive the stellar mass
function and correct for the Eddington bias. We find a mass-dependent evolution
of the global and star-forming populations. This mass-dependent evolution is a
direct consequence of the star formation being quenched in galaxies more
massive than M>10^10.7Msun. For the mass function of the quiescent galaxies, we
do not find any significant evolution of the high-mass end at z<1; however we
observe a clear flattening of the faint-end slope. From z~3 to z~1, the density
of quiescent galaxies increases over the entire mass range. Their comoving
stellar mass density increases by 1.6 dex between z~3 and z~1 and by less than
0.2dex at z<1. We infer the star formation history from the mass density
evolution and we find an excellent agreement with instantaneous star formation
rate measurements at z<1.5, while we find differences of 0.2dex at z>1.5
consistent with the expected uncertainties. We also develop a new method to
infer the specific star formation rate from the mass function of star-forming
galaxies. We find that the specific star formation rate of 10^10Msun galaxies
increases continuously in the redshift range 1<z<4. Finally, we compare our
results with a semi-analytical model and find that these models overestimate
the density of low mass quiescent galaxies by an order of magnitude, while the
density of low-mass star-forming galaxies is successfully reproduced. | Herschel-ATLAS Galaxy Counts and High Redshift Luminosity Functions: The
Formation of Massive Early Type Galaxies: Exploiting the Herschel-ATLAS Science Demonstration Phase (SDP) survey data,
we have determined the luminosity functions (LFs) at rest-frame wavelengths of
100 and 250 micron and at several redshifts z>1, for bright sub-mm galaxies
with star formation rates (SFR) >100 M_sun/yr. We find that the evolution of
the comoving LF is strong up to z~2.5, and slows down at higher redshifts. From
the LFs and the information on halo masses inferred from clustering analysis,
we derived an average relation between SFR and halo mass (and its scatter). We
also infer that the timescale of the main episode of dust-enshrouded star
formation in massive halos (M_H>3*10^12 M_sun) amounts to ~7*10^8 yr. Given the
SFRs, which are in the range 10^2-10^3 M_sun/yr, this timescale implies final
stellar masses of order of 10^11-10^12 M_sun. The corresponding stellar mass
function matches the observed mass function of passively evolving galaxies at
z>1. The comparison of the statistics for sub-mm and UV selected galaxies
suggests that the dust-free, UV bright phase, is >10^2 times shorter than the
sub-mm bright phase, implying that the dust must form soon after the onset of
star formation. Using a single reference Spectral Energy Distribution (SED; the
one of the z~2.3 galaxy SMM J2135-0102), our simple physical model is able to
reproduce not only the LFs at different redshifts > 1 but also the counts at
wavelengths ranging from 250 micron to ~1 mm. Owing to the steepness of the
counts and their relatively broad frequency range, this result suggests that
the dispersion of sub-mm SEDs of z>1 galaxies around the reference one is
rather small. |
Improving NASA/IPAC Extragalactic Database Redshift Calculations: The NASA/IPAC Extragalactic Database (NED) is an impressive tool for finding
near-exhaustive information on millions of astrophysical objects. Here, we
outline a small systematic error that occurs in NED because a low-redshift
approximation is used when making the correction from redshifts in the
heliocentric frame to the cosmic microwave background (CMB) rest frame. It
means that historically NED systematically misreported the values of CMB-frame
redshifts by up to $\sim10^{-3}z$ (about 0.001 at redshift of 1). This is a
systematic error, and therefore the impact on applications requiring precise
redshifts has the potential to be significant -- for example, a systematic
redshift error of $\sim10^{-4}$ at low redshift could resolve the Hubble
tension. We have consulted with the NED team and they are updating the software
to remove this systematic error so these corrections are accurate at all
redshifts. Here, we explain the changes and how they impact the redshift values
NED currently reports. | Spectroscopy of luminous z>7 galaxy candidates and sources of
contamination in z>7 galaxy searches: We present three bright z+ dropout candidates selected from deep
Near-Infrared (NIR) imaging of the COSMOS 2 square degree field. All three
objects match the 0.8-8um colors of other published z>7 candidates but are
three magnitudes brighter, facilitating further study. Deep spectroscopy of two
of the candidates covering 0.64-1.02um with Keck-DEIMOS and all three covering
0.94-1.10um and 1.52-1.80um with Keck-NIRSPEC detects weak spectral features
tentatively identified as Ly-alpha at z=6.95 and z=7.69 in two of the objects.
The third object is placed at z~1.6 based on a 24um and weak optical detection.
A comparison with the spectral energy distributions of known z<7 galaxies,
including objects with strong spectral lines, large extinction, and large
systematic uncertainties in the photometry yields no objects with similar
colors. However, the lambda>1um properties of all three objects can be matched
to optically detected sources with photometric redshifts at z~1.8, so the
non-detection in the i+ and z+ bands are the primary factors which favors a z>7
solution. If any of these objects are at z~7 the bright end of the luminosity
function is significantly higher at z>7 than suggested by previous studies, but
consistent within the statistical uncertainty and the dark matter halo
distribution. If these objects are at low redshift, the Lyman-Break selection
must be contaminated by a previously unknown population of low redshift objects
with very strong breaks in their broad band spectral energy distributions and
blue NIR colors. The implications of this result on luminosity function
evolution at high redshift is discussed. We show that the primary limitation of
z>7 galaxy searches with broad filters is the depth of the available optical
data. |
Constraining Photon Mass by Energy-Dependent Gravitational Light Bending: In the standard model of particle physics, photons are mass-less particles
with a particular dispersion relation. Tests of this claim at different scales
are both interesting and important. Experiments in territory labs and several
exterritorial tests have put some upper limits on photon mass, e.g. torsion
balance experiment in the lab shows that photon mass should be smaller than
$1.2\times 10^{-51}\rm g$. In this work, this claim is tested at a cosmological
scale by looking at strong gravitational lensing data available and an upper
limit of $8.71\times 10^{-39}$g on photon mass was given. Observations of
energy-dependent gravitational lensing with not yet available higher accuracy
astrometry instruments may constrain photon mass better. | HI Selected Galaxies in the Sloan Digital Sky Survey II: The Colors of
Gas-Rich Galaxies: We utilize color information for an HI-selected sample of 195 galaxies to
explore the star formation histories and physical conditions that produce the
observed colors. We show that the HI selection creates a significant offset
towards bluer colors that can be explained by enhanced recent bursts of star
formation. There is also no obvious color bimodality, because the HI selection
restricts the sample to bluer, actively star forming systems, diminishing the
importance of the red sequence. Rising star formation rates are still required
to explain the colors of galaxies bluer than g-r < 0.3. We also demonstrate
that the colors of the bluest galaxies in our sample are dominated by emission
lines and that stellar population synthesis models alone (without emission
lines) are not adequate for reproducing many of the galaxy colors. These
emission lines produce large changes in the r-i colors but leave the g-r color
largely unchanged. In addition, we find an increase in the dispersion of galaxy
colors at low masses that may be the result of a change in the star formation
process in low-mass galaxies. |
Small scales structures and neutrino masses: We review the impact of massive neutrinos on cosmological observables at the
linear order. By means of N-body simulations we investigate the signatures left
by neutrinos on the fully non-linear regime. We present the effects induced by
massive neutrinos on the matter power spectrum, the halo mass function and on
the halo-matter bias in massive neutrino cosmologies. We also investigate the
clustering of cosmic neutrinos within galaxy clusters. | Noether symmetry for Gauss-Bonnet dilatonic gravity: Noether symmetry for Gauss-Bonnet-Dilatonic interaction exists for a constant
dilatonic scalar potential and a linear functional dependence of the coupling
parameter on the scalar field. The symmetry with the same form of the potential
and coupling parameter exists all in the vacuum, radiation and matter dominated
era. The late time acceleration is driven by the effective cos- mological
constant rather than the Gauss-Bonnet term, while the later compensates for the
large value of the effective cosmological constant giving a plausible answer to
the well-known coincidence problem. |
Effects of observer peculiar motion on the isotropic background
frequency spectrum: from monopole to higher multipoles: The observer peculiar motion produces boosting effects in the background
anisotropies with frequency spectral behaviours related to its spectrum. We
study how the frequency spectrum of the background isotropic monopole emission
is modified and transferred to the frequency spectra at higher multipoles, l.
We perform the analysis in terms of spherical harmonic expansion up to a
certain lmax, for various models from radio to far-IR. We derive a system of
linear equations to obtain spherical harmonic coefficients and provide explicit
solutions up to lmax=6 as linear combinations of the signals at N=lmax+1
colatitudes. The associated Legendre polynomials symmetry with respect to
{\pi}/2 is used to separate the system into two subsystems, one for l=0 and
even l, the other for odd l. This improves the solutions accuracy with respect
to an arbitrary colatitudes choice. We apply the method to analytical or
semi-analytical representions of monopole spectra, i.e. to four types of CMB
distortions, four types of extragalactic backgrounds superimposed to the CMB
Planckian spectrum and some combinations of them. We present our results in
terms of spherical harmonic coefficients, relationships between the observed
and intrinsic monopoles, maps, angular power spectra. We compare the method
results with the ones obtained using more computationally demanding numerical
integrations or map generation/inversion. The method is generalized to include
the effect of the observer motion relative to the Sun. Its simplicity and
efficiency can significantly alleviate the computational effort needed for
accurate predictions and for the analysis of future data. We discuss the
superposition of the CMB intrinsic anisotropies and of the effects induced by
the observer motion, exploring for the possibility of constraining the
intrinsic dipole embedded in the kinematic dipole, in the presence of CMB
spectral distortions. | Analytical marginalisation over photometric redshift uncertainties in
cosmic shear analyses: As the statistical power of imaging surveys grows, it is crucial to account
for all systematic uncertainties. This is normally done by constructing a model
of these uncertainties and then marginalizing over the additional model
parameters. The resulting high dimensionality of the total parameter spaces
makes inferring the cosmological parameters significantly more costly using
traditional Monte-Carlo sampling methods. A particularly relevant example is
the redshift distribution, $p(z)$, of the source samples, which may require
tens of parameters to describe fully. However, relatively tight priors can be
usually placed on these parameters through calibration of the associated
systematics. In this paper we show, quantitatively, that a linearisation of the
theoretical prediction with respect to these calibratable systematic parameters
allows us to analytically marginalise over these extra parameters, leading to a
factor $\sim30$ reduction in the time needed for parameter inference, while
accurately recovering the same posterior distributions for the cosmological
parameters that would be obtained through a full numerical marginalisation over
160 $p(z)$ parameters. We demonstrate that this is feasible not only with
current data and current achievable calibration priors but also for future
Stage-IV datasets. |
A possible physical connection between helium-rich stellar populations
of massive globular clusters and the UV upturn of galactic spheroids: We discuss a possible physical connection between helium-rich (Y > 0.35)
stellar populations of massive globular clusters (GCs) and the ultraviolet (UV)
upturn of galactic spheroids by using analytical and numerical models. In our
model, all stars are initially formed as bound or unbound star clusters (SCs)
formed from giant molecular clouds (GMCs) and the SCs can finally become GCs,
open clusters, and field stars depending on physical properties of their host
GMCs. An essential ingredient of the model is that helium-rich stars are formed
almost purely from gas ejected from massive asymptotic giant branch (AGB)
stars. The helium-rich star formation is assumed to occur within massive SCs if
the masses of the progenitor GMCs are larger than a threshold mass (M_thres).
These massive SCs can finally become either massive GCs or helium-rich field
stars depending on whether they are disintegrated or not. Using this model, we
show that if the initial mass functions (IMFs) in galactic spheroids are mildly
top-heavy, then the mass fractions of helium-rich main-sequence stars (F_He)
can be as large as ~ 0.1 for M_thres=10^7 M_sun. F_He is found to depend on
IMFs and M_thres such that it can be larger for shallower IMFs and smaller
M_thres. The inner regions of galactic spheroids show larger F_He in almost all
models. Based on these results, we suggest that if the UV upturn of elliptical
galaxies is due to the larger fractions of helium-rich stars, then the origin
can be closely associated with top-heavy IMFs in the galaxies. | ESO VLT Optical Spectroscopy of BL Lac Objects IV. New spectra and
properties of the full sample: We present the last chapter of a spectroscopy program aimed at deriving the
redshift or a lower limit to the redshift of BL Lac objects using medium
resolution spectroscopy. Here we report new spectra for 33 BL Lac object
candidates obtained in 2008-2009 confirming the BL Lac nature of 25 sources and
for 5 objects we obtained new redshifts. These new observations are combined
with our previous data in order to construct a homogeneous sample of \sim 70 BL
Lacs with high quality spectroscopy. All these spectra can be accessed at the
website http://www.oapd.inaf.it/zbllac/. The average spectrum, beaming
properties of the full sample, discussion on intervening systems and future
perspectives are addressed. |
Sub-millimeter to centimeter excess emission from the Magellanic Clouds.
I. Global spectral energy distribution: In order to reconstruct the global SEDs of the Magellanic Clouds over eight
decades in spectral range, we combined literature flux densities representing
the entire LMC and SMC respectively, and complemented these with maps extracted
from the WMAP and COBE databases covering the missing the 23--90 GHz (13--3.2
mm) and the poorly sampled 1.25--250 THz (240--1.25 micron). We have discovered
a pronounced excess of emission from both Magellanic Clouds, but especially the
SMC, at millimeter and sub-millimeter wavelengths. We also determined accurate
thermal radio fluxes and very low global extinctions for both LMC and SMC.
Possible explanations are briefly considered but as long as the nature of the
excess emission is unknown, the total dust masses and gas-to-dust ratios of the
Magellanic Clouds cannot reliably be determined. | Effects of Massive Neutrinos on the Large-Scale Structure of the
Universe: Cosmological neutrinos strongly affect the evolution of the largest
structures in the Universe, i.e. galaxies and galaxy clusters. We use large
box-size full hydrodynamic simulations to investigate the non-linear effects
that massive neutrinos have on the spatial properties of cold dark matter (CDM)
haloes. We quantify the difference with respect to the concordance LambdaCDM
model of the halo mass function and of the halo two-point correlation function.
We model the redshift-space distortions and compute the errors on the linear
distortion parameter beta introduced if cosmological neutrinos are assumed to
be massless. We find that, if not taken correctly into account and depending on
the total neutrino mass, these effects could lead to a potentially fake
signature of modified gravity. Future nearly all-sky spectroscopic galaxy
surveys will be able to constrain the neutrino mass if it is larger than 0.6
eV, using beta measurements alone and independently of the value of the matter
power spectrum normalisation. In combination with other cosmological probes,
this will strengthen neutrino mass constraints and help breaking parameter
degeneracies. |
Farpoint: A High-Resolution Cosmology Simulation at the Gigaparsec Scale: In this paper we introduce the Farpoint simulation, the latest member of the
Hardware/Hybrid Accelerated Cosmology Code (HACC) gravity-only simulation
family. The domain covers a volume of (1000$h^{-1}$Mpc)$^3$ and evolves close
to two trillion particles, corresponding to a mass resolution of $m_p\sim
4.6\cdot 10^7 h^{-1}$M$_\odot$. These specifications enable comprehensive
investigations of the galaxy-halo connection, capturing halos down to small
masses. Further, the large volume resolves scales typical of modern surveys
with good statistical coverage of high mass halos. The simulation was carried
out on the GPU-accelerated system Summit, one of the fastest supercomputers
currently available. We provide specifics about the Farpoint run and present an
initial set of results. The high mass resolution facilitates precise
measurements of important global statistics, such as the halo
concentration-mass relation and the correlation function down to small scales.
Selected subsets of the simulation data products are publicly available via the
HACC Simulation Data Portal. | Primordial Black Hole Formation during a Strongly Coupled Crossover: The final mass distribution of primordial black holes is sensitive to the
equation of state of the Universe at the scales accessible by the power
spectrum. Motivated by the presence of phase transitions in several beyond the
Standard Model theories, some of which are strongly coupled, we analyze the
production of primordial black holes during such phase transitions, which we
model using the gauge/gravity duality. We focus in the (often regarded as
physically uninteresting) case for which the phase transition is just a smooth
crossover. We find an enhancement of primordial black hole production in the
range $M_{\rm{PBH}}\in[10^{-16},10^{-6}]M_{\odot}$. |
A comparative study of MOND and MOG theories versus the$κ$-model:
An application to galaxy clusters: Many models have been proposed to minimize the dark matter (DM) content in
various astronomical objects at every scale in the Universe. The most widely
known model isMOdified Newtonian Dynamics (MOND). MOND was first published by
Mordehai Milgromin 1983 (Milgrom, 1983; 2015; see also Banik and Zhao, 2022 for
a review). A second concurrent model is modified gravity (MOG), which is a
covariant scalar-tensor-vector (STVG)extension of general relativity (Moffat,
2006; 2020). Other theories also exist but have notbeen broadly applied to a
large list of astronomical objects (Mannheim and Kazanas, 1989;Capozziello and
De Laurentis, 2012; O'Brien and Moss, 2015; Verlinde, 2017). A new model,called
$\kappa$-model, based on very elementary phenomenological considerations, has
recently beenproposed in the astrophysics field. This model shows that the
presence of dark matter canbe considerably minimized with regard to the
dynamics of galaxies (Pascoli, 2022 a,b). The$\kappa$-model belongs to the
general family of theories descended from MOND. Under this familyof theories,
there is no need to develop a highly uncertain dark matter sector of physics
toexplain the observations. | New approaches in the analysis of Dark Matter direct detection data:
scratching below the surface of the most general WIMP parameter space: We show that compatibility between the DAMA modulation result (as well as
less statistically significant excesses such as the CDMS Silicon effect and the
excess claimed by CRESST) with constraints from other experiments can be
achieved by extending the analysis of direct detection data beyond the standard
elastic scattering of a WIMP off nuclei with a spin--dependent or a
spin--independent cross section and with a velocity distribution as predicted
by the Isothermal Sphere model. To do so we discuss several new approaches for
the analysis of Dark Matter direct detection data, with the goal to remove or
reduce its dependence on specific theoretical assumptions, and to extend its
scope: the factorization approach of astrophysics uncertainties, the
classification and study of WIMP-nucleon interactions within non--relativistic
field theory, inelastic scattering and isovector-coupling cancellations
including subdominant two-nucleon NLO effects. Typically, combining two or more
of these ingredients can lead to conclusions which are very different to what
usually claimed in the literature. This shows that we are only starting now to
scratch the surface of the most general WIMP direct detection parameter space. |
Extended Hot Halos Around Isolated Galaxies Observed in the ROSAT
All-Sky Survey: We place general constraints on the luminosity and mass of hot X-ray emitting
gas residing in extended "hot halos" around nearby massive galaxies. We examine
stacked images of 2165 galaxies from the 2MASS Very Isolated Galaxy Catalog
(2MVIG), as well as subsets of this sample based on galaxy morphology and
K-band luminosity. We detect X-ray emission at high confidence (ranging up to
nearly 10\sigma) for each subsample of galaxies. The average L_X within 50 kpc
is 1.0\pm0.1 (statistical) \pm0.2 (systematic) x10^40 erg/s, although the
early-type galaxies are more than twice as luminous as the late-type galaxies.
Using a spatial analysis, we also find evidence for extended emission around
five out of seven subsamples (the full sample, the luminous galaxies,
early-type galaxies, luminous late-type galaxies, and luminous early-type
galaxies) at 92.7%, 99.3%, 89.3%, 98.7%, and 92.1% confidence, respectively.
Several additional lines of evidence also support this conclusion and suggest
that about 1/2 of the total emission is extended, and about 1/3 of the extended
emission comes from hot gas. For the sample of luminous galaxies, which has the
strongest evidence for extended emission, the average hot gas mass is 4x10^9
Msun within 50 kpc and the implied accretion rate is 0.4 Msun/yr. | Dark Energy Survey Supernovae: Simulations and Survey Strategy: We present simulations for the Dark Energy Survey (DES) using a new code
suite (SNANA) that generates realistic supernova light curves accounting for
atmospheric seeing conditions and intrinsic supernova luminosity variations
using MLCS2k2 or SALT2 models. Errors include stat-noise from photo-statistics
and sky noise. We applied SNANA to simulate DES supernova observations and
employed an MLCS-based fitter to obtain the distance modulus for each simulated
light curve. We harnessed the light curves in order to study selection biases
for high-redshift supernovae and to constrain the optimal DES observing
strategy using the Dark Energy Task Force figure of merit. |
The Local Value of $H_0$ in an Inhomogeneous Universe: The effects of local inhomogeneities on low redshift $H_0$ determinations are
studied by estimating the redshift-distance relation of mock sources in N-body
simulations. The results are compared to those obtained using the standard
approach based on Hubble's law. The comparison shows a clear tendency for the
standard approach to yield lower values of $H_0$ than the approach based on the
scheme using light rays. The difference is, however, small. More precisely, it
is found that the overall effect of inhomogeneities on the determination of
$H_0$ is a small increase in the local estimates of about $0.3\%$ compared to
the results obtained with Hubble's law, when based on a typical distribution of
supernovae in the redshift range $0.01 < z < 0.1$. The overall conclusion of
the study is a verification of the results that have earlier been obtained by
using Hubble's law: The effects of inhomogeneities on local $H_0$ estimates are
not significant enough to make it plausible that differences in high- and
low-redshift estimates of $H_0$ are due to small inhomogeneities within the
setting of standard cosmology. | The HectoMAP Cluster Survey: Spectroscopically Identified Clusters and
their Brightest Cluster Galaxies (BCGs): We apply a friends-of-friends (FoF) algorithm to identify galaxy clusters and
we use the catalog to explore the evolutionary synergy between BCGs and their
host clusters. We base the cluster catalog on the dense HectoMAP redshift
survey (2000 redshifts deg$^{-2}$). The HectoMAP FoF catalog includes 346
clusters with 10 or more spectroscopic members. We list these clusters and
their members (5992 galaxies with a spectroscopic redshift). We also include
central velocity dispersions ($\sigma_{*, BCG}$) for all of the FoF cluster
BCGs, a distinctive feature of the HectoMAP FoF catalog. HectoMAP clusters with
higher galaxy number density (80 systems) are all genuine clusters with a
strong concentration and a prominent BCG in Subaru/Hyper Suprime-Cam images.
The phase-space diagrams show the expected elongation along the line-of-sight.
Lower-density systems include some false positives. We establish a connection
between BCGs and their host clusters by demonstrating that
$\sigma_{*,BCG}/\sigma_{cl}$ decreases as a function of cluster velocity
dispersion ($\sigma_{cl}$), in contrast, numerical simulations predict a
constant $\sigma_{*, BCG}/\sigma_{cl}$. Sets of clusters at two different
redshifts show that BCG evolution in massive systems is slow over the redshift
range $z < 0.4$. The data strongly suggest that minor mergers may play an
important role in BCG evolution in these clusters ($\sigma_{cl} \gtrsim 300$ km
s$^{-1}$). For systems of lower mass ($\sigma_{cl} < 300$ km s$^{-1}$), the
data indicate that major mergers may play a significant role. The coordinated
evolution of BCGs and their host clusters provides an interesting test of
simulations in high density regions of the universe. |
The GOGREEN survey: the internal dynamics of clusters of galaxies at
redshift 0.9-1.4: We aim to determine the mass, velocity anisotropy, and pseudo phase-space
density profiles (M(r), beta(r), and Q(r), respectively) of clusters of
galaxies at the highest redshifts investigated in detail so far. We combine the
GOGREEN and GCLASS spectroscopic data-sets for 14 clusters with mass M200 >
10^14 Msolar at redshifts 0.9 < z < 1.4. We stack these 14 clusters into an
ensemble cluster of 581 member galaxies with stellar mass > 10^9.5 M_solar. We
use the MAMPOSSt method and the inversion of the Jeans equation technique to
determine M(r) and beta(r). We then combine the results of the M(r) and beta(r)
analysis to determine Q(r) for the ensemble cluster. The concentration c200 of
the ensemble cluster M(r) is in excellent agreement with predictions from
LambdaCDM cosmological numerical simulations, and with previous determinations
for clusters of similar mass and at similar redshifts, obtained from
gravitational lensing and X-ray data. We see no significant difference between
the total mass density and either the galaxy number density distributions or
the stellar mass distribution. Star-forming galaxies are spatially
significantly less concentrated than quiescent galaxies. The orbits of cluster
galaxies are isotropic near the center and more radial outside. Star-forming
galaxies and galaxies of low stellar mass tend to move on more radially
elongated orbits than quiescent galaxies and galaxies of high stellar mass.
Q(r), determined either using the total mass or the number density profile, is
very close to the power-law behavior predicted by numerical simulations. The
internal dynamics of clusters at the highest redshift probed in detail so far
are very similar to those of lower-redshift clusters, and in excellent
agreement with predictions of numerical simulations. The clusters in our sample
have already reached a high degree of dynamical relaxation. (Abridged) | Probing the rest-frame of the Universe with near-IR cosmic infrared
background: While the cosmic microwave background (CMB) dipole is largely assumed
entirely kinematic, there appears evidence that a part of it is primordial.
Such possibility arises in models implying a tilt, interpreted as a dark flow,
across the observable Universe. The kinematic nature of the entire CMB dipole
can be probed using the dipole of cosmic backgrounds from galaxies after the
last scattering. The near-IR cosmic infrared background (CIB) spectral energy
distribution leads to an amplified dipole compared to the CMB. The CIB dipole
is affected by galaxy clustering, decreasing with fainter, more distant
galaxies, and by Solar System emissions and Galactic dust, which dominate the
net CIB cosmological dipole in the optical/near-IR. We propose a technique that
enables an accurate measurement of the kinematic near-IR CIB dipole. The CIB,
effectively the integrated galaxy light (IGL), would be reconstructed from
resolved galaxies in the forthcoming space-borne wide surveys covering four
bands 0.9 to 2.5 micron. The galaxies will be sub-selected from the identified
magnitude range where the dipole component from galaxy clustering is below the
expected kinematic dipole. Using this technique the dipole can be measured in
each of the bands at the statistical signal-to-noise S/N>50--100 with the
forthcoming Euclid and Roman surveys, isolating CMB dipole's kinematic nature. |
The HectoMAP Cluster Survey - II. X-ray Clusters: We apply a friends-of-friends algorithm to the HectoMAP redshift survey and
cross-identify associated X-ray emission in the ROSAT All-Sky Survey data
(RASS). The resulting flux limited catalog of X-ray cluster survey is complete
to a limiting flux of $\sim3 \times10^{-13}$ erg s$^{-1}$ cm$^{-2}$ and
includes 15 clusters (7 newly discovered) with redshift $z \leq 0.4$. HectoMAP
is a dense survey ($\sim1200$ galaxies deg$^{-2}$) that provides $\sim50$
members (median) in each X-ray cluster. We provide redshifts for the 1036
cluster members. Subaru/Hyper Suprime-Cam imaging covers three of the X-ray
systems and confirms that they are impressive clusters. The HectoMAP X-ray
clusters have an $L_{X} - {\sigma}_{cl}$ scaling relation similar to that of
known massive X-ray clusters. The HectoMAP X-ray cluster sample predicts $\sim
12000 \pm3000$ detectable X-ray clusters in the RASS to the limiting flux,
comparable with previous estimates. | A Spherical Harmonic Analysis of the Ooty Wide Field Array (OWFA)
Visibility Signal: Considering redshifted $21$-cm intensity mapping with the upcoming OWFA whose
field of view subtends $\sim 57^{\circ}$ in the N-S direction, we present a
formalism which relates the measured visibilities to the spherical harmonic
coefficients of the sky signal. We use this to calculate window functions which
relate the two-visibility correlations {\it i.e.} the correlation between the
visibilities measured at two baselines and two frequencies, to different
multipoles of the multi-frequency angular power spectrum
$C_{\ell}(\nu_1,\nu_2)$. The formalism here is validated using simulations. We
also present approximate closed form analytical expressions which can be used
to calculate the window functions. Comparing the widely adopted flat sky
approximation, we find that its predictions match those of our spherical
harmonic formalism to within $16 \%$ across the entire OWFA baseline range. The
match improves at large baselines where we have $< 5 \%$ deviations. |
The Universal Initial Mass Function In The XUV Disk of M83: We report deep Subaru Halpha observations of the XUV disk of M83. These new
observations enable the first complete census of very young stellar clusters
over the entire XUV disk. Combining Subaru and GALEX data with a stellar
population synthesis model, we find that (1) the standard, but
stochastically-sampled, initial mass function (IMF) is preferred over the
truncated IMF, because there are low mass stellar clusters (10^{2-3}Msun) that
host massive O-type stars; that (2) the standard Salpeter IMF and a simple
aging effect explain the counts of FUV-bright and Halpha-bright clusters with
masses >10^3Msun; and that (3) the Halpha to FUV flux ratio over the XUV disk
supports the standard IMF. The Subaru Prime Focus Camera (Suprime-Cam) covers a
large area even outside the XUV disk -- far beyond the detection limit of the
HI gas. This enables us to statistically separate the stellar clusters in the
disk from background contamination. The new data, model, and previous
spectroscopic studies provide overall consistent results with respect to the
internal dust extinction (Av~0.1 mag) and low metallicity (~0.2Zsun) using the
dust extinction curve of SMC. | On the recovery of ISW fluctuations using large-scale structure tracers
and CMB temperature and polarization anisotropies: In this work we present a method to extract the signal induced by the
integrated Sachs-Wolfe (ISW) effect in the cosmic microwave background (CMB).
It makes use of the Linear Covariance-Based filter introduced by Barreiro et
al., and combines CMB data with any number of large-scale structure (LSS)
surveys and lensing information. It also exploits CMB polarization to reduce
cosmic variance. The performance of the method has been thoroughly tested with
simulations taking into account the impact of non-ideal conditions such as
incomplete sky coverage or the presence of noise. In particular, three galaxy
surveys are simulated, whose redshift distributions peak at low ($z \simeq
0.3$), intermediate ($z \simeq 0.6$) and high redshift ($z \simeq 0.9$). The
contribution of each of the considered data sets as well as the effect of a
mask and noise in the reconstructed ISW map is studied in detail. When
combining all the considered data sets (CMB temperature and polarization, the
three galaxy surveys and the lensing map), the proposed filter successfully
reconstructs a map of the weak ISW signal, finding a perfect correlation with
the input signal for the ideal case and around 80 per cent, on average, in the
presence of noise and incomplete sky coverage. We find that including CMB
polarization improves the correlation between input and reconstruction although
only at a small level. Nonetheless, given the weakness of the ISW signal, even
modest improvements can be of importance. In particular, in realistic
situations, in which less information is available from the LSS tracers, the
effect of including polarisation is larger. For instance, for the case in which
the ISW signal is recovered from CMB plus only one survey, and taking into
account the presence of noise and incomplete sky coverage, the improvement in
the correlation coefficient can be as large as 10 per cent. |
Primordial non-gaussianity from the bispectrum of 21-cm fluctuations in
the dark ages: A measurement of primordial non-gaussianity will be of paramount importance
to distinguish between different models of inflation. Cosmic microwave
background (CMB) anisotropy observations have set unprecedented bounds on the
non-gaussianity parameter f_NL but the interesting regime f_NL <~ 1 is beyond
their reach. Brightness-temperature fluctuations in the 21-cm line during the
dark ages (z ~ 30-100) are a promising successor to CMB studies, giving access
to a much larger number of modes. They are, however, intrinsically non-linear,
which results in secondary non-gaussianities orders of magnitude larger than
the sought-after primordial signal. In this paper we carefully compute the
primary and secondary bispectra of 21-cm fluctuations on small scales. We use
the flat-sky formalism, which greatly simplifies the analysis, while still
being very accurate on small angular scales. We show that the secondary
bispectrum is highly degenerate with the primordial one, and argue that even
percent-level uncertainties in the amplitude of the former lead to a bias of
order Delta f_NL ~ 10. To tackle this problem we carry out a detailed Fisher
analysis, marginalizing over the amplitudes of a few smooth redshift-dependent
coefficients characterizing the secondary bispectrum. We find that the
signal-to-noise ratio for a single redshift slice is reduced by a factor of ~5
in comparison to a case without secondary non-gaussianities. Setting aside
foreground contamination, we forecast that a cosmic-variance-limited experiment
observing 21-cm fluctuations over 30 < z < 100 with a 0.1-MHz bandwidth and
0.1-arcminute angular resolution could achieve a sensitivity of order
f_NL[local] ~ 0.03, f_NL[equilateral] ~ 0.04, and f_NL[orthogonal] ~ 0.03. | Direction dependence of the power spectrum and its effect on the Cosmic
Microwave Background Radiation: We study several anisotropic inflationary models and their implications for
the observed violation of statistical isotropy in the CMBR data. In two of
these models the anisotropy decays very quickly during the inflationary phase
of expansion. We explicitly show that these models lead to violation of
isotropy only for low l CMBR modes. Our primary aim is to fit the observed
alignment of l=2,3 multipoles to the theoretical models. We use two measures,
based on the power tensor, which contains information about the alignment of
each multipole, to quantify the anisotropy in data. One of the measures uses
the dispersion in eigenvalues of the power tensor. We also define another
measure which tests the overall correlation between two different multipoles.
We perturbatively compute these measures of anisotropy and fix the theoretical
parameters by making a best fit to l=2,3 multipoles. We show that some of the
models studied are able to consistently explain the observed violation of
statistical isotropy. |
A Model for Dipole Modulation of CMBR Polarization: I propose a model of dipole modulation in Cosmic Background Microwave
Radiation (CMBR) polarization fields Q and U. It is shown that the modulation
leads to correlations between l and l multipoles where either l = l or l = l
\pm 1, but the contribution for the case l = l cancels out after summing over
m. We perform a detailed mathematical analysis of the E and B mode correlations
and obtain the final result in a closed form. | The evolutionary connection between QSOs and SMGs: molecular gas in
far-infrared luminous QSOs at z ~ 2.5: We present IRAM Plateau de Bure Interferometer observations of the 12CO(3-2)
emission from two far-infrared luminous QSOs at z ~ 2.5 selected from the
Herschel-ATLAS survey. These far-infrared bright QSOs were selected to have
supermassive black holes (SMBHs) with masses similar to those thought to reside
in sub-millimetre galaxies (SMGs) at z ~ 2.5; making them ideal candidates as
systems in transition from an ultraluminous infrared galaxy phase to a sub-mm
faint, unobscured, QSO. We detect 12CO(3-2) emission from both QSOs and we
compare their baryonic, dynamical and SMBH masses to those of SMGs at the same
epoch. We find that these far-infrared bright QSOs have similar dynamical but
lower gas masses than SMGs. In particular we find that far-infrared bright QSOs
have ~50+-23% less warm/dense gas than SMGs, which combined with previous
results showing the QSOs lack the extended, cool reservoir of gas seen in SMGs,
suggests that they are at a different evolutionary stage. This is consistent
with the hypothesis that far-infrared bright QSOs represent a short (~1Myr) but
ubiquitous phase in the transformation of dust obscured, gas-rich,
starburst-dominated SMGs into unobscured, gas-poor, QSOs. |
Testing the cosmic opacity at higher redshifts: implication from quasars
with available UV and X-ray observations: In this paper, we present a cosmological model-independent test for the
cosmic opacity at high redshifts ($z\sim5$). We achieve this with the
opacity-dependent luminosity distances derived from nonlinear relation between
X-ray and UV emissions of quasars, combined with two types of
opacity-independent luminosity distances derived from the Hubble parameter
measurements and simulated gravitational wave (GW) events achievable with the
Einstein Telescope (ET). In the framework of two phenomenological
parameterizations adopted to describe cosmic opacity at high redshifts, our
main results show that a transparent universe is supported by the current
observational data at 2$\sigma$ confidence level. However, the derived value of
the cosmic opacity is slightly sensitive to the parametrization of $\tau(z)$,
which highlights the importance of choosing a reliable parametrization to
describe the optical depth $\tau(z)$ in the early universe. Compared with the
previous works, the combination of the quasar data and the $H(z)$/GW
observations in similar redshift ranges provides a novel way to confirm a
transparent universe ($\epsilon=0$ at higher redshifts $z\sim 5$), with an
accuracy of $\Delta \epsilon\sim 10^{-2}$. More importantly, our findings
indicate that a strong degeneracy between the cosmic opacity parameter and the
parameters characterizing the $L_{UV}-L_X$ relation of quasars, which
reinforces the necessity of proper calibration for such new type of
high-redshift standard candle (in a cosmological model-independent way). | Sample variance in weak lensing: how many simulations are required?: Constraining cosmology using weak gravitational lensing consists of comparing
a measured feature vector of dimension $N_b$ with its simulated counterpart. An
accurate estimate of the $N_b\times N_b$ feature covariance matrix $\mathbf{C}$
is essential to obtain accurate parameter confidence intervals. When
$\mathbf{C}$ is measured from a set of simulations, an important question is
how large this set should be. To answer this question, we construct different
ensembles of $N_r$ realizations of the shear field, using a common
randomization procedure that recycles the outputs from a smaller number
$N_s\leq N_r$ of independent ray-tracing $N$--body simulations. We study
parameter confidence intervals as a function of ($N_s,N_r$) in the range $1\leq
N_s\leq 200$ and $1\leq N_r\lesssim 10^5$. Previous work has shown that
Gaussian noise in the feature vectors (from which the covariance is estimated)
lead, at quadratic order, to an $O(1/N_r)$ degradation of the parameter
confidence intervals. Using a variety of lensing features measured in our
simulations, including shear-shear power spectra and peak counts, we show that
cubic and quartic covariance fluctuations lead to additional $O(1/N_r^2)$ error
degradation that is not negligible when $N_r$ is only a factor of few larger
than $N_b$. We study the large $N_r$ limit, and find that a single, 240Mpc$/h$
sized $512^3$-particle $N$--body simulation ($N_s=1$) can be repeatedly
recycled to produce as many as $N_r={\rm few}\times10^4$ shear maps whose power
spectra and high-significance peak counts can be treated as statistically
independent. As a result, a small number of simulations ($N_s=1$ or $2$) is
sufficient to forecast parameter confidence intervals at percent accuracy. |
Gravitational effects of condensate dark matter on compact stellar
objects: We study the gravitational effect of non-self-annihilating dark matter on
compact stellar objects. The self-interaction of condensate dark matter can
give high accretion rate of dark matter onto stars. Phase transition to
condensation state takes place when the dark matter density exceeds the
critical value. A compact degenerate dark matter core is developed and alter
the structure and stability of the stellar objects. Condensate dark matter
admixed neutron stars is studied through the two-fuid TOV equation. The
existence of condensate dark matter deforms the mass-radius relation of neutron
stars and lower their maximum baryonic masses and radii. The possible effects
on the Gamma-ray Burst rate in high redshift are discussed. | A Consistent Comparison of Bias Models using Observational Data: We investigate five different models for the dark matter halo bias, ie., the
ratio of the fluctuations of mass tracers to those of the underlying mass, by
comparing their cosmological evolution using optical QSO and galaxy bias data
at different redshifts, consistently scaled to the WMAP7 cosmology. Under the
assumption that each halo hosts one extragalactic mass tracer, we use a
$\chi^2$ minimization procedure to determine the free parameters of the bias
models as well as to statistically quantify their ability to represent the
observational data. Using the Akaike information criterion we find that the
model that represents best the observational data is the Basilakos & Plionis
(2001; 2003) model with the tracer merger extension of Basilakos, Plionis &
Ragone-Figueroa (2008) model. The only other statistically equivalent model, as
indicated by the same criterion, is the Tinker et al. (2010) model. Finally, we
find an average, over the different models, dark matter halo mass that hosts
optical QSOs of: $M_h\simeq 2.7 (\pm 0.6) \times 10^{12} h^{-1} M_{\odot}$,
while the corresponding value for optical galaxies is: $M_h\simeq 6.3 (\pm 2.1)
\times 10^{11} h^{-1} M_{\odot}$. |
The First Stars: Pop III stars are the key to the character of primeval galaxies, the first
heavy elements, the onset of cosmological reionization, and the seeds of
supermassive black holes. Unfortunately, in spite of their increasing
sophistication, numerical models of Pop III star formation cannot yet predict
the masses of the first stars. Because they lie at the edge of the observable
universe, individual Pop III stars will also remain beyond the reach of
telescopes for the foreseeable future, and so their properties remain unknown.
However, it will soon be possible to constrain their masses by the direct
detection of their supernovae and by reconciling their nucleosynthetic yields
to the chemical abundances measured in ancient metal-poor stars in the Galactic
halo, some of which may be bear the ashes of the first stars. Here, I review
current problems on the simulation frontier in Pop III star formation and
discuss the best prospects for constraining their properties observationally in
the near term. | Using the tilted flat-$Λ$CDM and the untilted non-flat
$Λ$CDM inflation models to measure cosmological parameters from a
compilation of observational data: We use the physically-consistent tilted spatially-flat and untilted non-flat
$\Lambda$CDM inflation models to constrain cosmological parameter values with
the Planck 2015 cosmic microwave background (CMB) anisotropy data and recent
Type Ia supernovae measurements, baryonic acoustic oscillations (BAO) data,
growth rate observations, and Hubble parameter measurements. The most dramatic
consequence of including the four non-CMB data sets is the significant
strengthening of the evidence for non-flatness in the non-flat $\Lambda$CDM
model, from 1.8$\sigma$ for the CMB data alone to 5.1$\sigma$ for the full data
combination. The BAO data is the most powerful of the non-CMB data sets in more
tightly constraining model parameter values and in favoring a spatially-closed
Universe in which spatial curvature contributes about a percent to the current
cosmological energy budget. The untilted non-flat $\Lambda$CDM model better
fits the large-angle CMB temperature anisotropy angular spectrum and is more
consistent with the Dark Energy Survey constraints on the current value of the
rms amplitude of mass fluctuations ($\sigma_8$) as a function of the current
value of the nonrelativistic matter density parameter ($\Omega_m$) but does not
provide as good a fit to the smaller-angle CMB temperature anisotropy data as
does the tilted flat-$\Lambda$CDM model. Some measured cosmological parameter
values differ significantly between the two models, including the reionization
optical depth and the baryonic matter density parameter, both of whose
2$\sigma$ ranges (in the two models) are disjoint or almost so. |
Detailed dark matter maps of galaxy cluster substructure and direct
comparison to simulations: Images from the next generation of telescopes will enable strikingly detailed
reconstruction of the dark matter distributions in galaxy cluster cores using
strong gravitational lensing analysis. This will provide a key test of
Lambda-CDM cosmology on cluster scales where tensions currently exist. Observed
dark matter distributions will be compared directly to those realized in
simulations, forgoing any assumptions about light tracing mass. The required
observations are deep, multicolor, and high-resolution, ideally supplemented
with spectra of faint objects. ACS onboard HST is capable of obtaining images
of sufficient quality, but for prohibitive integration times. The next
generation of telescopes promises to efficiently yield the required images. An
analysis method capable of processing the expected large numbers of multiple
images has been developed (see below). The full range of constraints possible
from analyzing these detailed mass maps is a matter of ongoing investigation. | Dark Energy and CMB: The American Physical Society's Division of Particles and Fields initiated a
long-term planning exercise over 2012-13, with the goal of developing the
community's long term aspirations. The sub-group "Dark Energy and CMB" prepared
a series of papers explaining and highlighting the physics that will be studied
with large galaxy surveys and cosmic microwave background experiments. This
paper summarizes the findings of the other papers, all of which have been
submitted jointly to the arXiv. |
Primordial Black Holes in the Excursion Set Theory: We study primordial black holes (PBHs) formation in the excursion set theory
(EST) in a vast range of PBHs masses with and without confirmed constraints on
their abundance. In this work, we introduce a new concept of the first touch in
the context of EST for PBHs formation. This new framework takes into account
the earlier horizon reentry of smaller masses. Our study shows that in the EST,
it is possible to produce PBHs in different mass range, with enhanced power
spectrum, which could make up all dark matter. We also show that in a broad
blue-tilted power spectrum, the production of PBHs is dominated by smaller
masses. Our analysis put an upper limit $\sim\,$0.1 on the amplitude of the
curvature power spectrum at length scales relevant for PBHs formation. | Interpretation and implication of the non-detection of GeV spectrum
excess by Fermi gamma-ray Space Telescope in most GRBs: Since the launch of the Fermi Gamma-ray Space Telescope on 11 June 2008,
significant detections of high energy emission have been reported only in six
Gamma-ray Bursts (GRBs) until now. In this work we show that the lack of
detection of a GeV spectrum excess in almost all GRBs, though somewhat
surprisingly, can be well understood within the standard internal shock model
and several alternatives like the photosphere-internal shock (gradual magnetic
dissipation) model and the magnetized internal shock model. The delay of the
arrival of the >100 MeV photons from some Fermi bursts can be interpreted too.
We then show that with the polarimetry of prompt emission these models may be
distinguishable. In the magnetized internal shock model, high linear
polarization level should be typical. In the standard internal shock model,
high linear polarization level is still possible but much less frequent. In the
photosphere-internal shock model, the linear polarization degree is expected to
be roughly anti-correlated with the weight of the photosphere/thermal
component, which may be a unique signature of this kind of model. We also
briefly discuss the implication of the current Fermi GRB data on the detection
prospect of the prompt PeV neutrinos. The influences of the intrinsic proton
spectrum and the enhancement of the neutrino number at some specific energies,
due to the cooling of pions (muons), are outlined. |
Distribution function of nuclei from $e^\pm$ scattering in the presence
of a strong primordial magnetic field: The amplitude of the primordial magnetic field (PMF) is constrained from
observational limits on primordial nuclear abundances. Within this constraint,
it is possible that nuclear motion is regulated by Coulomb scattering with
electrons and positrons ($e^\pm$'s), while $e^\pm$'s are affected by a PMF
rather than collisions. For example, at a temperature of $10^9$ K, thermal
nuclei typically experience $\sim 10^{21}$ scatterings per second that are
dominated by very small angle scattering leading to minuscule changes in the
nuclear kinetic energy of order $\mathcal{O}$(1) eV. In this paper the upper
limit on the effects of a possible discretization of the $e^\pm$ momenta by the
PMF on the nuclear momentum distribution is estimated under the extreme
assumptions that the momentum of the $e^\pm$ is relaxed before and after
Coulomb scattering to Landau levels, and that during Coulomb scattering the PMF
is neglected. This assumption explicitly breaks the time reversal invariance of
Coulomb scattering, and the Maxwell-Boltzmann distribution is not a trivial
steady state solution of the Boltzmann equation under these assumptions. We
numerically evaluate the collision terms in the Boltzmann equation, and show
that the introduction of a special direction in the $e^\pm$ distribution by the
PMF generates no directional dependence of the collisional destruction term of
nuclei. Large anisotropies in the nuclear distribution function are then
constrained from big bang nucleosynthesis. Ultimately, we conclude that a PMF
does not significantly affect the isotropy or BBN. | Gravitational-wave cosmology across 29 decades in frequency: Quantum fluctuations of the gravitational field in the early Universe,
amplified by inflation, produce a primordial gravitational-wave background
across a broad frequency band. We derive constraints on the spectrum of this
gravitational radiation, and hence on theories of the early Universe, by
combining experiments that cover 29 orders of magnitude in frequency. These
include Planck observations of cosmic microwave background temperature and
polarization power spectra and lensing, together with baryon acoustic
oscillations and big bang nucleosynthesis measurements, as well as new pulsar
timing array and ground-based interferometer limits. While individual
experiments constrain the gravitational-wave energy density in specific
frequency bands, the combination of experiments allows us to constrain
cosmological parameters, including the inflationary spectral index, $n_t$, and
the tensor-to-scalar ratio, $r$. Results from individual experiments include
the most stringent nanohertz limit of the primordial background to date from
the Parkes Pulsar Timing Array, $\Omega_{\rm gw}(f)<2.3\times10^{-10}$.
Observations of the cosmic microwave background alone limit the
gravitational-wave spectral index at 95\% confidence to $n_t\lesssim5$ for a
tensor-to-scalar ratio of $r = 0.11$. However, the combination of all the above
experiments limits $n_t<0.36$. Future Advanced LIGO observations are expected
to further constrain $n_t<0.34$ by 2020. When cosmic microwave background
experiments detect a non-zero $r$, our results will imply even more stringent
constraints on $n_t$ and hence theories of the early Universe. |
Direct Detection of Hawking Radiation from Asteroid-Mass Primordial
Black Holes: Light, asteroid-mass primordial black holes, with lifetimes in the range
between hundreds to several millions times the age of the universe, are
well-motivated candidates for the cosmological dark matter. Using archival
COMPTEL data, we improve over current constraints on the allowed parameter
space of primordial black holes as dark matter by studying their evaporation to
soft gamma-rays in nearby astrophysical structures. We point out that a new
generation of proposed MeV gamma-ray telescopes will offer the unique
opportunity to directly detect Hawking evaporation from observations of nearby
dark matter dense regions and to constrain, or discover, the primordial black
hole dark matter. | Cosmological constraints from Planck galaxy clusters with CMB lensing
mass bias calibration: We present a new cosmological analysis of the galaxy clusters in the Planck
MMF3 cosmology sample with a cosmic microwave background (CMB) lensing
calibration of the cluster masses. As demonstrated by Planck, galaxy clusters
detected via the Sunyaev-Zel'dovich (SZ) effect offer a powerful way to
constrain cosmological parameters such as $\Omega_{\mathrm{m}}$ and $\sigma_8$.
Determining the absolute cluster mass scale is, however, difficult, and some
recent calibrations have yielded cosmological constraints in apparent tension
with constraints in the $\Lambda$CDM model derived from the power spectra of
the primary CMB anisotropies. In order to calibrate the absolute mass scale of
the full Planck cluster sample, we remeasure the masses of all 433 clusters
through their weak lensing signature in the CMB temperature anisotropies as
measured by Planck. We perform a joint Bayesian analysis of the cluster counts
and masses taking as input the estimated cluster masses, SZ signal-to-noise
ratios, and redshifts. Our analysis properly accounts for selection effects in
the construction of the cluster sample. We find $\sigma_8
\left(\Omega_{\mathrm{m}}/0.33\right)^{0.25} = 0.765 \pm 0.035$ and
$1-b_{\mathrm{SZ}} = 0.71 \pm 0.10$, where the mass bias factor
$1-b_{\mathrm{SZ}}$ relates cluster mass to the SZ mass that appears in the
X-ray-calibrated cluster scaling relations. We find no evidence for tension
with the Planck primary CMB constraints on $\Lambda$CDM model parameters. |
Experimental search of bursts of gamma rays from primordial black holes
using different evaporation models: Experimental data of arrays "Andyrchy" and "Carpet-2" of Baksan Neutrino
Observatory (Institute for Nuclear Research), obtained in the regime of a
detection of the single cosmic-ray component, are used for a search of the
bursts of cosmic gamma rays from evaporating primordial black holes. Different
theoretical models of the evaporation process are used for the analysis.
Distributions of the counting rate fluctuations on both arrays agree with the
expectations from the cosmic ray background. The new constraints on the
concentration of evaporating primordial black holes in the local region of
Galaxy are obtained. The comparison of the results of different experiments is
given. | CARS: The CFHTLS-Archive-Research Survey III. First detection of cosmic
magnification in samples of normal high-z galaxies: Weak gravitational lensing (WL) has been established as one of the most
promising probes of cosmology. So far, most studies have exploited the shear
effect of WL leading to coherent distortions of galaxy shapes. But WL also
introduces coherent magnifications. We want to detect this cosmic magnification
effect in large samples of high-redshift galaxies selected from the Deep part
of the CFHTLS. Lyman-break galaxies (LBGs) at z=2.5-5, are used as a background
sample and are cross-correlated to foreground lens galaxies selected by
photo-z's. The signals of LBGs in different magnitude bins are compared to
predictions from WL theory. An optimally weighted correlation function is
estimated by taking into account the slope of external LBG luminosity
functions. For the first time, we detect cosmic magnification in a sample of
normal galaxies. These background sources are also the ones with the highest
redshifts so far used for WL measurements. The amplitude and angular dependence
of the cross-correlation functions agree well with theoretical expectations and
the lensing signal is detected with high significance. In particular, we detect
an anti-correlation between faint LBGs and foreground galaxies which cannot be
caused by redshift overlap. (abridged) |
Extended $Λ$CDM model and viscous dark energy: A Bayesian analysis: We propose an approach considering the nonextensive effects in the context of
the Verlinde theory in order to address an extended cosmological model in the
context of viscous dark energy. Specifically, this model leads to a tiny
perturbation in the dynamics of the expansion of the universe through the
generalized Friedmann equations so-called the extended $\Lambda$CDM model. From
the observational test standpoint, we make a Bayesian analysis of the models of
bulk viscosity for dark energy which follows the Eckart theory of bulk
viscosity. These models are investigated through the context of both models
$\Lambda$CDM and extended $\Lambda$CDM. The Bayesian analysis is performed
using the data of CMB Distance priors, Baryon Acoustic Oscillations
Measurements, Cosmic Chronometers, and SNe Ia distance measurements. | On the nuclear obscuration of H2O maser galaxies: To shed light onto the circumnuclear environment of 22 GHz H2O maser
galaxies, we have analyzed some of their multi-wavelength properties, including
the far infrared luminosity (FIR), the luminosity of the [O III]\lambda5007
emission line, the nuclear X-ray luminosity, and the equivalent width of the
neutral iron Ka emission line (EW (Ka)). Our statistical analysis includes a
total of 85 sources, most of them harboring an active galactic nucleus (AGN).
There are strong anti-correlations between EW (Ka) and two "optical thickness
parameters", i.e. the ratios of the X-ray luminosity versus the presumably more
isotropically radiated [O III] and far infrared (FIR) luminosities. Based on
these anti-correlations, a set of quantitative criteria, EW (Ka) > 300eV,
L_{2-10keV} < 2L_[O III] and L_{FIR} > 600L_{2-10keV} can be established for
Compton-thick nuclear regions. 18 H2O maser galaxies belong to this category.
There are no obvious correlations between the EW (Ka), the [O III] luminosity
and the isotropic H2O maser luminosity. When comparing samples of Seyfert 2s
with and without detected H2O maser lines, there seem to exist differences in
EW (Ka) and the fraction of Compton-thick nuclei. This should be studied
further. For AGN masers alone, there is no obvious correlation between FIR and
H2O maser luminosities. However, including masers associated with star forming
regions, a linear correlation is revealed. Overall, the extragalactic FIR-H2O
data agree with the corresponding relation for Galactic maser sources,
extrapolated by several orders of magnitude to higher luminosities. |
Wandering in the Lyman-alpha Forest: A Study of Dark Matter-Dark
Radiation Interactions: The amplitude of large-scale matter fluctuations inferred from the observed
Sunyaev-Zeldovich (SZ) cluster mass function and from weak gravitational
lensing studies, when taken at face value, is in tension with measurements of
the cosmic microwave background (CMB) and baryon acoustic oscillation (BAO). In
this work, we revisit whether this possible discrepancy can be attributed to
new interactions in the dark matter sector. Focusing on a cosmological model
where dark matter interacts with a dark radiation species until the epoch of
matter-radiation equality, we find that measurements of the Lyman-alpha flux
power spectrum from the Sloan Digital Sky Survey provides no support to the
hypothesis that new dark matter interactions can resolve the possible tension
between CMB and large-scale structure (LSS). Indeed, while the addition of dark
matter-dark radiation interactions leads to an improvement of
$2\Delta\ln\mathcal{L}=12$ with respect to the standard $\Lambda$ cold dark
matter ($\Lambda$CDM) model when only CMB, BAO, and LSS data are considered,
the inclusion of Lyman-alpha data reduces the improvement of the fit to
$2\Delta\ln\mathcal{L}=6$ relative to $\Lambda$CDM. We thus conclude that the
statistical evidence for new dark matter interactions (largely driven by the
Planck SZ dataset) is marginal at best, and likely caused by systematics in the
data. We also perform a Fisher forecast analysis for the reach of a future
dataset composed of a CMB-S4 experiment combined with the Large Synoptic Survey
Telescope galaxy survey. We find that the constraint on the effective number of
fluid-like dark radiation species, $\Delta N_{\rm fluid}$, will be improved by
an order of magnitude compared to current bounds. | Halpha3: an Halpha imaging survey of HI selected galaxies from ALFALFA.
IV. Structure of galaxies in the Local and Coma Superclusters: We present the analysis of the galaxy structural parameters from Halpha3, an
Halpha narrow-band imaging follow-up survey of ~800 galaxies selected from the
HI ALFALFA Survey in the Local and Coma Superclusters. Taking advantage of
Halpha3 which provides the complete census of the recent star-forming, HI-rich
galaxies in the local universe, we aim to investigate the structural parameters
of both the young (<10 Myr) and the old (>1 Gyr) stellar populations. By
comparing the sizes of these stellar components we investigated the spatial
scale on which galaxies are growing at the present cosmological epoch and the
role of the environment in quenching the star-formation activity. We computed
the concentration, asymmetry, and clumpiness structural parameters. To quantify
the sizes we computed half-light radii and a new parameter dubbed EW/r. The
concentration index computed in the r band depends on the stellar mass and on
the Hubble type, these variables being related since most massive galaxies are
bulge dominated thus most concentrated. Going toward later spirals and
irregulars both the concentration index and the stellar mass decrease. Blue
Compact dwarfs represent an exception since they have similar stellar mass but
they are more concentrated than dwarf irregulars. The asymmetry and the
clumpiness increase along the spiral sequence then they decrease going into the
dwarf regime, where the light distribution is smooth and more symmetric. When
measured on Halpha images, the CAS parameters do not exhibit obvious
correlations with Hubble type. We found that the concentration index is the
main parameter that describes the current growth of isolated galaxies but, for
a fixed concentration, the stellar mass plays a second order role. At the
present epoch, massive galaxies are growing inside-out, conversely the dwarfs
are growing on the scale of their already assembled mass. |
The Wyoming Survey for H-alpha. III. A Multi-wavelength Look at
Attenuation by Dust in Galaxies out to z~0.4: We report results from the Wyoming Survey for H-alpha (WySH), a comprehensive
four-square degree survey to probe the evolution of star-forming galaxies over
the latter half of the age of the Universe. We have supplemented the H-alpha
data from WySH with infrared data from the Spitzer Wide-area Infrared
Extragalactic (SWIRE) Survey and ultraviolet data from the Galaxy Evolution
Explorer (GALEX) Deep Imaging Survey. This dataset provides a multi-wavelength
look at the evolution of the attenuation by dust, and here we compare a
traditional measure of dust attenuation (L(TIR)/L(FUV)) to a diagnostic based
on a recently-developed robust star formation rate (SFR) indicator,
[H-alpha_obs+24-micron]/H-alpha_obs. With such data over multiple epochs, the
evolution in the attenuation by dust with redshift can be assessed. We present
results from the ELAIS-N1 and Lockman Hole regions at z~0.16, 0.24, 0.32 and
0.40. While the ensemble averages of both diagnostics are relatively constant
from epoch to epoch, each epoch individually exhibits a larger attenuation by
dust for higher star formation rates. Hence, an epoch to epoch comparison at a
fixed star formation rate suggests a mild decrease in dust attenuation with
redshift. | Baryon effects on the internal structure of LCDM halos in the EAGLE
simulations: We investigate the internal structure and density profiles of halos of mass
$10^{10}-10^{14}~M_\odot$ in the Evolution and Assembly of Galaxies and their
Environment (EAGLE) simulations. These follow the formation of galaxies in a
$\Lambda$CDM Universe and include a treatment of the baryon physics thought to
be relevant. The EAGLE simulations reproduce the observed present-day galaxy
stellar mass function, as well as many other properties of the galaxy
population as a function of time. We find significant differences between the
masses of halos in the EAGLE simulations and in simulations that follow only
the dark matter component. Nevertheless, halos are well described by the
Navarro-Frenk-White (NFW) density profile at radii larger than ~5% of the
virial radius but, closer to the centre, the presence of stars can produce
cuspier profiles. Central enhancements in the total mass profile are most
important in halos of mass $10^{12}-10^{13}M_\odot$, where the stellar fraction
peaks. Over the radial range where they are well resolved, the resulting galaxy
rotation curves are in very good agreement with observational data for galaxies
with stellar mass $M_*<5\times10^{10}M_\odot$. We present an empirical fitting
function that describes the total mass profiles and show that its parameters
are strongly correlated with halo mass. |
Cosmological joint analysis with cosmic growth and expansion rate: The measurements of expansion rate $H(z)$ and the growth rate $f\sigma_8(z)$
describe the evolution of the universe, and both of them can constrain the
cosmological models through data analysis. Due to the lack of data points,
these datasets are combined by the traditional combined method ($\chi^2$
method) to select a best-fitting cosmological model. In 2017, Linder proposed a
joint method, which describes the evolution of the universe through
$H(z)-f\sigma_8$ diagram instead of the redshift z. Compared to individual
datasets, Linder demonstrated the advantages of the joint method to distinguish
cosmologies. In this paper, we compare the significance between the traditional
combined method and Linder's joint method by constraining the density parameter
$\Omega_M$ using Akaike Information Criterion (AIC) and Bayesian Information
Criterion (BIC). The result shows that the joint method is more significant
than the traditional combined method. | The Complete Calibration of the Color-Redshift Relation (C3R2) Survey:
Survey Overview and Data Release 1: A key goal of the Stage IV dark energy experiments Euclid, LSST and WFIRST is
to measure the growth of structure with cosmic time from weak lensing analysis
over large regions of the sky. Weak lensing cosmology will be challenging: in
addition to highly accurate galaxy shape measurements, statistically robust and
accurate photometric redshift (photo-z) estimates for billions of faint
galaxies will be needed in order to reconstruct the three-dimensional matter
distribution. Here we present an overview of and initial results from the
Complete Calibration of the Color-Redshift Relation (C3R2) survey, designed
specifically to calibrate the empirical galaxy color-redshift relation to the
Euclid depth. These redshifts will also be important for the calibrations of
LSST and WFIRST. The C3R2 survey is obtaining multiplexed observations with
Keck (DEIMOS, LRIS, and MOSFIRE), the Gran Telescopio Canarias (GTC; OSIRIS),
and the Very Large Telescope (VLT; FORS2 and KMOS) of a targeted sample of
galaxies most important for the redshift calibration. We focus spectroscopic
efforts on under-sampled regions of galaxy color space identified in previous
work in order to minimize the number of spectroscopic redshifts needed to map
the color-redshift relation to the required accuracy. Here we present the C3R2
survey strategy and initial results, including the 1283 high confidence
redshifts obtained in the 2016A semester and released as Data Release 1. |
Mask Effects on Cosmological Studies with Weak Lensing Peak Statistics: In this paper, we analyze in detail with numerical simulations how the mask
effect can influence the weak lensing peak statistics reconstructed from the
shear measurement of background galaxies. It is found that high peak fractions
are systematically enhanced due to masks, the larger the masked area, the
higher the enhancement. In the case with about $13\%$ of the total masked area,
the fraction of peaks with SNR $\nu\ge 3$ is $\sim 11\%$ in comparison with
$\sim 7\%$ of the mask-free case in our considered cosmological model. This can
induce a large bias on cosmological studies with weak lensing peak statistics.
Even for a survey area of $9\hbox{ deg}^2$, the bias in $(\Omega_m, \sigma_8)$
is already close to $3\sigma$. It is noted that most of the affected peaks are
close to the masked regions. Therefore excluding peaks in those regions can
reduce the bias but at the expense of loosing usable survey areas. Further
investigations find that the enhancement of high peaks number can be largely
attributed to higher noise led by the fewer number of galaxies usable in the
reconstruction. Based on Fan et al. (2010), we develop a model in which we
exclude only those large masks with radius larger than $3\arcmin. For the
remained part, we treat the areas close to and away from the masked regions
separately with different noise levels. It is shown that this two-noise-level
model can account for the mask effect on peak statistics very well and the
cosmological bias is significantly reduced. | Mass distribution and accretion of sub-halos: We use the "Millennium Simulation" to study the mass function of accreted
sub-halos during merger events in the dark halo assembly history. Our study
includes three kinds of sub-halo mergers: (1) mergers that happen to the main
progenitor of dark halos; (2) mergers that happen on the entire merging history
tree of dark halos; and (3) mergers that leave identifiable sub-halos in
present-day dark halos. We estimate the unevolved sub-halo mass functions
(USMFs), for which sub-halo masses are measured at the times of their
accretion. For sub-halos that merge into the main branch of a present-day dark
halo, their USMF can be well described by a universal functional form, in
excellent agreement with previous results. The same conclusion can also be
reached for the USMF of all progenitors that have merged to become sub-halos
during the entire halo merging history. In both cases, the USMFs are also
independent of the redshift of host halos. Due to tidal disruption, only a
small fraction of the accreted halos survive as sub-halos identifiable in the
present-day dark halos. In cluster-sized halos, about 30% of the survived
sub-halos are sub-subhalos, and this fraction decreases with decreasing halo
mass. For given halo and sub-halo masses, the accretion time has very broad
distribution, but the survived sub-halos are all accreted quite recently. |
Stellar and total baryon mass fractions in groups and clusters since
redshift 1: We investigate if the discrepancy between estimates of the total baryon mass
fraction obtained from observations of the cosmic microwave background (CMB)
and of galaxy groups/clusters persists when a large sample of groups is
considered.
To this purpose, 91 candidate X-ray groups/poor clusters at redshift 0.1 < z
< 1 are selected from the COSMOS 2 deg^2 survey, based only on their X-ray
luminosity and extent. This sample is complemented by 27 nearby clusters with a
robust, analogous determination of the total and stellar mass inside R_500. The
total sample of 118 groups and clusters with z < 1 spans a range in M_500 of
~10^13--10^15 M_sun. We find that the stellar mass fraction associated with
galaxies at R_500 decreases with increasing total mass as (M_500)^-0.37 \pm
0.04, independent of redshift. Estimating the total gas mass fraction from a
recently derived, high quality scaling relation, the total baryon mass fraction
(f_500^stars+gas=f_500^stars+f_500^gas) is found to increase by ~ 25% when
M_500 increases from <M>=5 X 10^13 M_sun to <M> = 7 X 10^14 M_sun. After
consideration of a plausible contribution due to intra--cluster light (11--22%
of the total stellar mass), and gas depletion through the hierarchical assembly
process (10% of the gas mass), the estimated values of the total baryon mass
fraction are still lower than the latest CMB measure of the same quantity
(WMAP5), at a significance level of 3.3\sigma for groups of <M>=5 X
10^13~M_sun. The discrepancy decreases towards higher total masses, such that
it is 1\sigma at <M>= 7 X 10^14~M_sun. We discuss this result in terms of
non--gravitational processes such as feedback and filamentary heating. | CMB lensing bi-spectrum: assessing analytical predictions against
full-sky lensing simulations: Cosmic microwave background (CMB) lensing is an integrated effect whose
kernel is greater than half the peak value in the range $1<z<5$. Measuring this
effect offers a powerful tool to probe the large-scale structure of the
Universe at high redshifts. With the increasing precision of ongoing CMB
surveys, other statistics than the lensing power spectrum, in particular the
lensing bi-spectrum, will be measured at high statistical significance. This
will provide ways to improve the constraints on cosmological models and lift
degeneracies. Following on an earlier paper, we test analytical predictions of
the CMB lensing bi-spectrum against full-sky lensing simulations, and discuss
their validity and limitation in detail. The tree-level prediction of
perturbation theory agrees with the simulation only up to $\ell\sim 200$, but
the one-loop order allows capturing the simulation results up to $\ell\sim
600$. We also show that analytical predictions based on fitting formulas for
the matter bi-spectrum agree reasonably well with simulation results, although
the precision of the agreement depends on the configurations and scales
considered. For instance, the agreement is at the $10\%$-level for the
equilateral configuration at multipoles up to $\ell\sim2000$, but the
difference in the squeezed limit raises to more than a factor of two at
$\ell\sim2000$. This discrepancy appears to come from limitations in the
fitting formula of the matter bi-spectrum. We also find that the analytical
prediction for the post-Born correction to the bi-spectrum is in good agreement
with the simulation. We conclude by discussing the bi-spectrum prediction in
some theories of modified gravity. |
The Concentration-Mass Relation of Massive, Dynamically Relaxed Galaxy
Clusters: Agreement Between Observations and $Λ$CDM Simulations: The relationship linking a galaxy cluster's total mass with the concentration
of its mass profile and its redshift is a fundamental prediction of the Cold
Dark Matter (CDM) paradigm of cosmic structure formation. However, confronting
those predictions with observations is complicated by the fact that simulated
clusters are not representative of observed samples where detailed mass profile
constraints are possible. In this work, we calculate the
Symmetry-Peakiness-Alignment (SPA) morphology metrics for maps of X-ray
emissivity from THE THREE HUNDRED project hydrodynamical simulations of galaxy
clusters at four redshifts, and thereby select a sample of morphologically
relaxed, simulated clusters, using observational criteria. These clusters have
on average earlier formation times than the full sample, confirming that they
are both morphologically and dynamically more relaxed than typical. We
constrain the concentration-mass-redshift relation of both the relaxed and
complete sample of simulated clusters, assuming power-law dependences on mass
($\kappa_m$) and $1+z$ ($\kappa_\zeta$), finding $\kappa_m = -0.12 \pm 0.07$
and $\kappa_\zeta = -0.27 \pm 0.19$ for the relaxed subsample. From an
equivalently selected sample of massive, relaxed clusters observed with ${\it
Chandra}$, we find $\kappa_m = -0.12 \pm 0.08$ and $\kappa_\zeta = -0.48 \pm
0.19$, in good agreement with the simulation predictions. The simulated and
observed samples also agree well on the average concentration at a pivot mass
and redshift providing further validation of the $\Lambda$CDM paradigm in the
properties of the largest gravitationally collapsed structures observed. This
also represents the first clear detection of decreasing concentration with
redshift, a longstanding prediction of simulations, in data. | The Impact of Anisotropic Redshift Distributions on Angular Clustering: A leading way to constrain physical theories from cosmological observations
is to test their predictions for the angular clustering statistics of matter
tracers, a technique that is set to become ever more central with the next
generation of large imaging surveys. Interpretation of this clustering requires
knowledge of the projection kernel, or the redshift distribution of the
sources, and the typical assumption is an isotropic redshift distribution for
the objects. However, variations in the kernel are expected across the survey
footprint due to photometric variations and residual observational systematic
effects. We develop the formalism for anisotropic projection and present
several limiting cases that elucidate the key aspects. We quantify the impact
of anisotropies in the redshift distribution on a general class of angular
two-point statistics. In particular, we identify a mode-coupling effect that
can add power to auto-correlations, including galaxy clustering and cosmic
shear, and remove it from certain cross-correlations. If the projection
anisotropy is primarily at large scales, the mode-coupling depends upon its
variance as a function of redshift; furthermore, it is often of similar shape
to the signal. In contrast, the cross-correlation of a field whose selection
function is anisotropic with another one featuring no such variations -- such
as CMB lensing -- is immune to these effects. We discuss explicitly several
special cases of the general formalism including galaxy clustering,
galaxy-galaxy lensing, cosmic shear and cross-correlations with CMB lensing,
and publicly release a code to compute the biases. |
Non-Gaussianity consistency relations and their consequences for the
peaks: Strong deviations from scale invariance and the appearance of high peaks in
the primordial power spectrum have been extensively studied for generating
primordial black holes (PBHs) or gravitational waves (GWs). It is also
well-known that the effect of non-linearities can be significant in both
phenomena. In this paper, we advocate the existence of a general single-field
consistency relation that relates the amplitude of non-Gaussianity in the
squeezed limit $f_{\text{NL}}$ to the power spectrum and remains valid when
almost all other consistency relations are violated. In particular, it is
suitable for studying scenarios where scale invariance is strongly violated. We
discuss the general and model-independent consequences of the consistency
relation on the behavior of $f_{\text{NL}}$ at different scales. Specifically,
we study the size, sign and slope of $f_{\text{NL}}$ at the scales where the
power spectrum peaks and argue that generally the peaks of $f_{\text{NL}}$ and
the power spectrum occur at different scales. As an implication of our results,
we argue that non-linearities can shift or extend the range of scales
responsible for the production of PBHs or GWs, relative to the window as
determined by the largest peak of the power spectrum, and may also open up new
windows for both phenomena. | Evidence for Line-of-Sight Frequency Decorrelation of Polarized Dust
Emission in $Planck$ Data: If a single line of sight (LOS) intercepts multiple dust clouds of different
spectral energy distributions and magnetic field orientations, the frequency
scaling of each of the Stokes $Q$ and $U$ parameters of thermal dust emission
may be different ("LOS frequency decorrelation"). We present first evidence for
LOS frequency decorrelation in $Planck$ data. We use independent,
neutral-hydrogen--measurements of the number of clouds per LOS and the magnetic
field orientation in each cloud to select two sets of sightlines: (i) a target
sample (pixels likely to exhibit LOS frequency decorrelation); (ii) a control
sample (pixels lacking complex LOS structure). We test the null hypothesis that
LOS frequency decorrelation is not detectable in $Planck$ 353 and 217~GHz
polarization data at high Galactic latitudes. The data reject this hypothesis
at high significance. The detection is robust against choice of CMB map and
map-making pipeline. The observed change in polarization angle due to LOS
frequency decorrelation is detectable above the $Planck$ noise level. The
probability that the detected effect is due to noise alone ranges from $5\times
10^{-2}$ to $4\times 10^{-7}$, depending on the CMB subtraction algorithm and
treatment of residual systematics; correcting for residual systematics
increases the significance of the effect. The LOS decorrelation effect is
stronger for sightlines with more misaligned magnetic fields, as expected. We
estimate that an intrinsic variation of $\sim15\%$ in the ratio of 353 to
217~GHz polarized emission between clouds is sufficient to reproduce the
measured effect. Our finding underlines the importance of ongoing studies to
map the 3D structure of the magnetized dusty ISM that could help component
separation methods to account for frequency decorrelation effects in CMB
polarization studies. |
Mapping the radial structure of AGN tori: We present mid-IR interferometric observations of 6 type 1 AGNs at multiple
baseline lengths of 27--130m, reaching high angular resolutions up to
lambda/B~0.02 arcseconds. For two of the targets, we have simultaneous near-IR
interferometric measurements as well. The multiple baseline data directly probe
the radial distribution of the material on sub-pc scales. Within our sample,
which is small but spans over ~2.5 orders of magnitudes in the UV/optical
luminosity L of the central engine, the radial distribution clearly and
systematically changes with luminosity. First, we show that the brightness
distribution at a given mid-IR wavelength seems to be rather well described by
a power law, which makes a simple Gaussian or ring size estimation quite
inadequate. Here we instead use a half-light radius R_1/2 as a representative
size. We then find that the higher luminosity objects become more compact in
normalized half-light radii R_1/2 /R_in in the mid-IR, where R_in is the dust
sublimation radius empirically given by the L^1/2 fit of the near-IR
reverberation radii. This means that, contrary to previous studies, the
physical mid-IR emission size (e.g. in pc) is not proportional to L^1/2, but
increases with L much more slowly, or in fact, nearly constant at 13 micron.
Combining the size information with the total flux specta, we infer that the
radial surface density distribution of the heated dust grains changes from a
steep ~r^-1 structure in high luminosity objects to a shallower ~r^0 structure
in those of lower luminosity. The inward dust temperature distribution does not
seem to smoothly reach the sublimation temperature -- on the innermost scale of
~R_in, a relatively low temperature core seems to co-exist with a slightly
distinct brightness concentration emitting roughly at the sublimation
temperature. | Self-calibration method for II and GI types of intrinsic alignments of
galaxies: We introduce a self-calibration method that can be applied to the intrinsic
ellipticity--intrinsic ellipticity (II) and gravitational shear -- intrinsic
ellipticity (GI) types of intrinsic alignment of galaxies. The method combines
previous self-calibration techniques with modifications to one of them in order
to use auto-spectra in addition to cross-spectra between redshift bins. This
allows one to use the self-calibration while preserving all the constraining
power of cosmic shear from surveys. We show that the new method provides more
flexibility in using various redshift bin widths. We perform cosmological
parameter constraint forecast when this method is applied to the Large Synoptic
Survey Telescope (LSST). Compared to the original self-calibration, we find
that the new method provides further significant reduction in any residual
shift in the cosmological parameters (e.g. factors of $2-4$ for the dark energy
equation of state) which is promising for accurate cosmology. |
CosmoReionMC: A package for estimating cosmological and astrophysical
parameters using CMB, Lyman-α absorption and global 21 cm data: We present a Markov Chain Monte Carlo (MCMC)-based parameter estimation
package, CosmoReionMC, to jointly constrain cosmological parameters of the
$\Lambda$CDM model and the astrophysical parameters related to hydrogen
reionization. The package is based on a previously developed physically
motivated semi-analytical model for reionization, a similar semi-analytical
model for computing the global 21~cm signal during the cosmic dawn and using an
appropriately modified version of the publicly available CAMB for computing the
CMB anisotropies. These calculations are then coupled to an MCMC ensemble
sampler \texttt{emcee} to compute the posterior distributions of the model
parameter. The model has twelve free parameters in total: five cosmological and
seven related to the stellar populations. We constrain the parameters by
matching the theoretical predictions with CMB data from Planck, observations
related to the quasar absorption spectra and, for the first time, the global
21~cm signal from EDGES. We find that incorporating the quasar spectra data in
the analysis tightens the bounds on the electron scattering optical depth
$\tau$ and consequently the normalization $A_s$ of the primordial matter power
spectrum (or equivalently $\sigma_8$). Furthermore, when we include the EDGES
data in the analysis, we find that an early population of metal-free stars with
efficient radio emission is necessary to match the absorption amplitude. The
CosmoReionMC package should have interesting future applications, e.g., probing
non-standard extensions to the $\Lambda$CDM model. | Submillimetre Photometry of 323 Nearby Galaxies from the Herschel
Reference Survey: The Herschel Reference Survey (HRS) is a guaranteed time Herschel key project
aimed at studying the physical properties of the interstellar medium in
galaxies of the nearby universe. This volume limited, K-band selected sample is
composed of galaxies spanning the whole range of morphological types (from
ellipticals to late-type spirals) and environments (from the field to the
centre of the Virgo Cluster). We present flux density measurements of the whole
sample of 323 galaxies of the HRS in the three bands of the Spectral and
Photometric Imaging Receiver (SPIRE), at 250, 350 and 500 microns. Aperture
photometry is performed on extended galaxies and point spread function (PSF)
fitting on timeline data for unresolved objects; we carefully estimate errors
and upper limits. The flux densities are found to be in good agreement with
those of the HeViCS and KINGFISH key projects in all SPIRE bands, and of the
Planck consortium at 350 and 550 microns, for the galaxies in common. This
submillimetre catalogue of nearby galaxies is a benchmark for the study of the
dust properties in the local universe, giving the zero redshift reference for
any cosmological survey. |
Towards an Observational Appraisal of String Cosmology: We review the current observational status of string cosmology when
confronted with experimental datasets. We begin by defining common
observational parameters and discuss how they are determined for a given model.
Then we review the observable footprints of several string theoretic models,
discussing the significance of various potential signals. Throughout we comment
on present and future prospects of finding evidence for string theory in
cosmology, and on significant issues for the future. | First Galaxy-Galaxy Lensing Measurement of Satellite Halo Mass in the
CFHT Stripe-82 Survey: We select satellite galaxies from the galaxy group catalog constructed with
the SDSS spectroscopic galaxies and measure the tangential shear around these
galaxies with source catalog extracted from CFHT/MegaCam Stripe-82 Survey to
constrain the mass of subhalos associated with them. The lensing signal is
measured around satellites in groups with masses in the range [10^{13},
5x10^{14}]h^{-1}M_{sun}, and is found to agree well with theoretical
expectation. Fitting the data with a truncated NFW profile, we obtain an
average subhalo mass of log M_{sub}= 11.68 \pm 0.67 for satellites whose
projected distances to central galaxies are in the range [0.1, 0.3] h^{-1}Mpc,
and log M_{sub}= 11.68 \pm 0.76 for satellites with projected halo-centric
distance in [0.3, 0.5] h^{-1}Mpc. The best-fit subhalo masses are comparable to
the truncated subhalo masses assigned to satellite galaxies using abundance
matching and about 5 to 10 times higher than the average stellar mass of the
lensing satellite galaxies. |
Confronting sound speed resonance with pulsar timing arrays: The stochastic signal detected by pulsar timing arrays (PTAs) has raised
great interest in understanding its physical origin. Assuming the signal is a
cosmological gravitational-wave background produced by overly large primordial
curvature perturbations, we investigate the sound speed resonance effect with
an oscillatory behavior using the combined PTA data from NANOGrav 15-yr data
set, PPTA DR3, and EPTA DR2. We find that the stochastic signal can be
explained by the induced gravitational waves sourced by the sound speed
resonance mechanism, with the oscillation frequency $f_* \in [1.51, 4.90]
\times 10^{-7}$Hz and the start time of oscillation $|\tau_0| \in [2.05, 106]
\times 10^7$s | Fast generation of mock galaxy catalogues with COLA: We investigate the feasibility of using COmoving Lagrangian Acceleration
(COLA) technique to efficiently generate galaxy mock catalogues that can
accurately reproduce the statistical properties of observed galaxies. Our
proposed scheme combines the subhalo abundance matching (SHAM) procedure with
COLA simulations, utilizing only three free parameters: the scatter magnitude
($\sigma_{\rm scat}$) in SHAM, the initial redshift ($z_{\rm init}$) of the
COLA simulation, and the time stride ($da$) used by COLA. In this
proof-of-concept study, we focus on a subset of BOSS CMASS NGC galaxies within
the redshift range $z\in [0.45, 0.55]$. We perform $\mathtt{GADGET}$ simulation
and low-resolution COLA simulations with various combinations of $(z_{\rm
init}, da)$, each using $1024^{3}$ particles in an $800~h^{-1}{\rm Mpc}$ box.
By minimizing the difference between COLA mock and CMASS NGC galaxies for the
monopole of the two-point correlation function (2PCF), we obtain the optimal
$\sigma_{\rm scat}$. We have found that by setting $z_{\rm init}=29$ and
$da=1/30$, we achieve a good agreement between COLA mock and CMASS NGC galaxies
within the range of 4 to $20~h^{-1}{\rm Mpc}$, with a computational cost two
orders of magnitude lower than that of the N-body code. Moreover, a detailed
verification is performed by comparing various statistical properties, such as
anisotropic 2PCF, three-point clustering, and power spectrum multipoles, which
shows similar performance between GADGET mock and COLA mock catalogues with the
CMASS NGC galaxies. Furthermore, we assess the robustness of the COLA mock
catalogues across different cosmological models, demonstrating consistent
results in the resulting 2PCFs. Our findings suggest that COLA simulations are
a promising tool for efficiently generating mock catalogues for emulators and
machine learning analyses in exploring the large-scale structure of the
Universe. |
Searching for dark matter - dark energy interactions: going beyond the
conformal case: We consider a generic cosmological model which allows for non-gravitational
direct couplings between dark matter and dark energy. The distinguishing
cosmological features of these couplings can be probed by current cosmological
observations, thus enabling us to place constraints on this generic interaction
which is composed of the conformal and disformal coupling functions. We perform
a global analysis in order to independently constrain the conformal, disformal,
and mixed interactions between dark matter and dark energy by combining current
data from: Planck observations of the cosmic microwave background radiation
anisotropies, a combination of measurements of baryon acoustic oscillations, a
supernovae Type Ia sample, a compilation of Hubble parameter measurements
estimated from the cosmic chronometers approach, direct measurements of the
expansion rate of the Universe today, and a compilation of growth of structure
measurements. We find that in these coupled dark energy models, the influence
of the local value of the Hubble constant does not significantly alter the
inferred constraints when we consider joint analyses that include all
cosmological probes. Moreover, the parameter constraints are remarkably
improved with the inclusion of the growth of structure data set measurements.
We find no compelling evidence for an interaction within the dark sector of the
Universe. | Beyond the standard $Λ$CDM cosmology: the observed structure of DM
halos and the shape of the power spectrum: Recent advances in observational astronomy allow to study various groups of
Dark Matter (DM) dominated objects from the dwarf spheroidal (dSph) galaxies to
clusters of galaxies that span the mass range from $10^{6} M_{\odot}$ to
$10^{15} M_{\odot}$. To analyze data of this divers collection of objects we
used a simple toy model of spherical DM halo formation that was initially
proposed by Peebles. This model introduced the concept of the epoch or redshift
of halo formation. Using this concept we analyzed selected sample of DM
dominated objects and we have found empirical correlations between the virial
mass, $M_{vir}$, of halos and basic parameters of their cores, namely, the mean
DM density, pressure and entropy. These correlations are a natural result of
similar evolution of all such objects. It is driven mainly by gravitational
interactions what implies a high degree of self similarity of both the process
of halos formation and their internal structure.
We confirmed the CDM--like shape of both the small and large scale power
spectrum. However, our reconstruction of the evolutionary history of observed
objects differs from expectations of the standard $\Lambda$CDM cosmology and
requires either a multicomponent composition of DM or a more complex primordial
power spectrum of density perturbations with significant excess of power at
scales of clusters of galaxies and larger. We demonstrated that a model with
suitable combination of the heavy DM particles (CDM) and DM particles with
large damping scale (HDM) could provide a successful description of the
observational data in a wide range of masses. |
Observational Feasibility of 4D Einstein-Gauss-Bonnet Cosmology:
Bouncing and Non-Bouncing Universes: This paper analyzes the possibility of bouncing and non-bouncing universes in
the framework of four-dimensional Einstein-Gauss-Bonnet (4D-EGB) gravity,
corresponding respectively to negative and positive coupling constants
$\lambda$ of the Gauss-Bonnet term. We also use the Horndeski-type
scalar-tensor theory to assess the role of a scalar charge $C$ as a geometrical
contribution to the radiation in the Universe. We modify the expansion history
of the universe to allow for modifications induced by the 4D-EGB gravity. Using
Planck measurements of the cosmic microwave background anisotropies as well as
various datasets of baryonic acoustic oscillations, we set the upper bounds
$\lambda \le 10^{-16} \text{(km/s/Mpc)}^{-2} $ and $\lambda \le 10^{-30}
\text{(km/s/Mpc)}^{-2} $ for the non-bouncing and bouncing scenarios. The upper
limit in the latter case is mainly driven by the requirement to conservatively
respect the thermal history at energy scales of the standard model of particle
physics. We also find that the contribution of the geometrical radiation-like
term of the model cannot exceed 10\% of the current radiation in the Universe.
This study shows the feasibility of a bouncing universe, even with a normal
matter sector, in the 4D-EGB gravity. More theoretical investigation is
required to further explore possible observational predictions of the model
that can distinguish between general relativity and 4D-EGB gravity. | The mass function of nearby black hole candidates: The mass function of super-massive black holes in our cosmic neighborhood is
required to understand the statistics of their activity and consequently the
origin of the ultra high energy particles. We determine a mass function of
black hole candidates from the entire sky except for the Galactic plane. Using
the 2MASS catalogue as a starting point, and the well established correlation
between black hole mass and the bulge of old population of stars, we derive a
list of nearby black hole candidates within the redshift range z < 0.025, then
do a further selection based on the Hubble-type, and give this as a catalogue
elsewhere. The final list of black hole candidates above a mass of M_BH >
3*10^{6} M_sol has 5,829 entries; moreover doing a further Hubble type
correction to account for the selection effects cuts down the number to 2,919
black hole candidates. We also correct for volume, so that this mass function
is a volume limited distribution to redshift 0.025 The differential mass
function of nearby black hole candidates is a curved function, with a straight
simple power-law of index -3 above 10^{8} M_sol, growing progressively flatter
towards lower masses, turning off towards a gap below 3*10^{6} M_sol, and then
extending into the range where nuclear star clusters replace black holes. The
shape of this mass function can be explained in a simple merger picture.
Integrating this mass function over the redshift range, from which it has been
derived, gives a total number of black holes with z < 0.025, and M_BH > 10^{7}
M_sol of about 2.4*10^{4}, or, if we just average uniformly, 0.6 for every
square degree on the sky. In different models many of these are candidates for
ultra high energy particles sources. If a very small fraction of the
super-massive black holes produces ultra high energy cosmic rays, this should
be enough to observe the highly inhomogeneous distribution of the galaxies. |
The Globular Cluster Populations of Giant Galaxies: Mosaic Imaging of
Five Moderate-Luminosity Early-Type Galaxies: This paper presents results from wide-field imaging of the globular cluster
(GC) systems of five intermediate-luminosity (M_V ~-21 to -22) early-type
galaxies. The aim is to accurately quantify the global properties of the GC
systems by measuring them out to large radii. We obtained BVR imaging of four
lenticular galaxies (NGC 5866, NGC 4762, NGC 4754, NGC 3384) and one elliptical
galaxy (NGC 5813) using the KPNO 4m telescope and MOSAIC imager and traced the
GC population to projected galactocentric radii ranging from ~20 kpc to 120
kpc. We combine our imaging with Hubble Space Telescope data to measure the GC
surface density close to the galaxy center. We calculate the total number of
GCs (N_GC) from the integrated radial profile and find N_GC = 340 +/- 80 for
NGC 5866, N_GC = 2900 +/- 400 for NGC 5813, N_GC = 270 +/- 30 for NGC 4762,
N_GC = 115 +/- 15$ for NGC 4754, and N_GC = 120 +/- 30 for NGC 3384. The
measured GC specific frequencies are S_N between 0.6 and 3.6 and T in the range
0.9 to 4.2. These values are consistent with the mean specific frequencies for
the galaxies' morphological types found by our survey and other published data.
Three galaxies (NGC 5866, NGC 5813, NGC 4762) had sufficient numbers of GC
candidates to investigate color bimodality and color gradients in the GC
systems. NGC 5813 shows strong evidence (>3 sigma) for bimodality and a B-R
color gradient resulting from a more centrally concentrated red (metal-rich) GC
subpopulation. We find no evidence for statistically significant color
gradients in the other two galaxies. | Constraints on ultra-slow-roll inflation with the NANOGrav 15-Year
Dataset: Ultra-slow-roll~(USR) inflation predicts an exponential amplification of
scalar perturbations at small scales, which leads to a stochastic gravitational
wave background~(SGWB) through the coupling of the scalar and tensor modes at
the second-order expansion of the Einstein equation. In this work, we search
for such a scalar-induced SGWB from the NANOGrav 15-year (NG15) dataset, and
find that the SGWB from USR inflation could explain the observed data. We place
constraints on the amplitude of the scalar power spectrum to $P_{\mathrm{Rp}} >
10^{-1.80}$ at $95\%$ confidence level (C.L.) at the scale of $k\sim 20\,
\mathrm{pc}^{-1}$. We find that $\log_{10} P_{\mathrm{Rp}}$ degenerates with
the peak scale $\log_{10} k_{\mathrm{p}}$. We also obtain the parameter space
allowed by the data in the USR inflationary scenario, where the $e$-folding
numbers of the duration of the USR phase has a lower limit $\Delta N > 2.80$
($95\%$ C.L.) when the USR phase ends at $N\approx 20$. Since the priors for
the model parameters %in the USR model are uncertain, we do not calculate the
Bayes factors. Instead, to quantify the goodness of fit, we calculate the
maximum values of the log-likelihood for USR inflation, bubble collision of the
cosmological phase transition, and inspiraling supermassive black hole binaries
(SMBHBs), respectively. Our results imply that the SGWB from USR inflation can
fit the data better than the one from SMBHBs. |
A Compressed Sensing Approach to 3D Weak Lensing: (Abridged) Weak gravitational lensing is an ideal probe of the dark universe.
In recent years, several linear methods have been developed to reconstruct the
density distribution in the Universe in three dimensions, making use of
photometric redshift information to determine the radial distribution of lensed
sources. In this paper, we aim to address three key issues seen in these
methods; namely, the bias in the redshifts of detected objects, the line of
sight smearing seen in reconstructions, and the damping of the amplitude of the
reconstruction relative to the underlying density. We consider the problem
under the framework of compressed sensing (CS). Under the assumption that the
data are sparse in an appropriate dictionary, we construct a robust estimator
and employ state-of-the-art convex optimisation methods to reconstruct the
density contrast. For simplicity in implementation, and as a proof of concept
of our method, we reduce the problem to one-dimension, considering the
reconstruction along each line of sight independently. Despite the loss of
information this implies, we demonstrate that our method is able to accurately
reproduce cluster haloes up to a redshift of z=1, deeper than state-of-the-art
linear methods. We directly compare our method with these linear methods, and
demonstrate minimal radial smearing and redshift bias in our reconstructions,
as well as a reduced damping of the reconstruction amplitude as compared to the
linear methods. In addition, the CS framework allows us to consider an
underdetermined inverse problem, thereby allowing us to reconstruct the density
contrast at finer resolution than the input data. | A New Method to Measure Hubble Parameter $H(z)$ using Fast Radio Bursts: The Hubble parameter $H(z)$ is directly related to the expansion of our
Universe. It can be used to study dark energy and constrain cosmology models.
In this paper, we propose that $H(z)$ can be measured using fast radio bursts
(FRBs) with redshift measurements. We use dispersion measures contributed by
the intergalactic medium, which is related to $H(z)$, to measure Hubble
parameter. We find that 500 mocked FRBs with dispersion measures and redshift
information can accurately measure Hubble parameters using Monte Carlo
simulation. The maximum deviation of $H(z)$ from standard $\Lambda$CDM model is
about 6\% at redshift $z= 2.4$. We also test our method using Monte Carlo
simulation. Kolmogorov-Smirnov (K-S) test is used to check the simulation. The
$p$-value of K-S test is 0.23, which confirms internal consistency of the
simulation. In future, more localizations of FRBs make it as an attractive
cosmological probe. |
Gravitational wave background from coalescence of black hole binaries
population: This paper has been withdrawn by the authors because it had major revisions. | Herschel observations of Cen A: stellar heating of two extragalactic
dust clouds: We present the first results of a multi-wavelength survey, incoporating
Herschel-SPIRE, Spitzer, GALEX and ATCA observations, of a 1 deg x 1 deg field
centred on Centaurus A. As well as detecting the inner lobes of the active
galactic nucleus (AGN) jet and counterjet, we have found two clouds, bright at
sub-mm wavelengths, ~15 kpc from the centre of Cen A that are co-aligned with
the jets. Flux measurements at Herschel wavelengths have proved vital in
constraining fits to the Spectral Energy Distributions (SEDs). The clouds are
well fit by a single-temperature, modified blackbody spectrum (beta=2)
indicating that we are looking at two cold dust clouds on the outskirts of Cen
A. The temperature and masses of the clouds are: T_{north} = 12.6^{+1.1}_{-1.2}
K, T_{south} = 15.1^{+1.7}_{-1.6} K; log(M_{north} / M_o) = 5.8^{+0.2}_{-0.2},
log(M_{south} / M_o) = 5.6^{+0.2}_{-0.2} and the gas-dust ratio for both clouds
is ~100. The measured values for the northern dust cloud are consistent with
previous measurements from ISO while the southern cloud is a new sub-mm
detection. The two dust clouds are located at the termini of the partial HI
ring that surrounds Cen A which is also where the gas column density peaks...
abridged |
SNe Data Analysis in Variable Speed of Light Cosmologies without
Cosmological Constant: In this work, we aim to show the possibilities of the variable speed of light
(VSL) theory in explaining the type Ia supernovae observations without
introducing dark energy. The speed of light is assumed to be scale factor
dependent, which is the most popular assumption in VSL theory. We show the
modified calculation of the distance modulus, and the validity of the
redshift-scale factor relation in VSL theory. Three different models of VSL are
tested SNe data-sets with proper constraints on the model parameters. The
comparison of the three models and flat $\Lambda$CDM in distance modulus is
showed. Some basic problems and the difficulties of the confirmation of the VSL
theory are also discussed | Probing the evolution of galaxy clusters using SZ effect and non-thermal
emission: first results from A1413: Mass is the most fundamental property of galaxy clusters. However, measuring
it is still a challenge. Calibrating mass from intracluster medium observables
such as the Sunyaev-Zel'dovich (SZ) effect is subject to uncertainty and biases
because of the hydrostatic equilibrium assumption. On the other hand, merging
cluster systems have been shown to exhibit radio emission which implies a link
with disturbances from hydrostatic equilibrium. We present work on studying
deviations of galaxy cluster gas pressure profile from the average (universal)
pressure profile using an example of galaxy cluster Abell 1413 with SZ effect
data from the Arcminute Microkelvin Imager and Planck. This cluster has also
been observed at low radio frequency with the Murchison Widefield Array
allowing the investigation of links between gas pressure profile deviations and
the presence of radio emission. |
Periodic Fast Radio Bursts from Axion Emission by Cosmic Superstrings: We propose that the periodic fast radio bursts of FRB 180916.J0158+65 are
sourced by axion emission (mass $m_{a} \sim 10^{-14}$ eV) from cosmic
superstrings. Some of the emitted axions are converted to photons by magnetic
fields as they travel along the line of sight to Earth. An impulsive burst of
axion emission generates a photon signal typically lasting for milliseconds and
varying with frequency in the observed manner. We find a range of parameters in
our cosmic string network model consistent with the properties of FRB
180916.J0158+65. We suggest followup gravitational wave observations to test
our model. | Quasar Radio-Loudness and the Elliptical Core Problem: The dichotomy between radio-loud and radio-quiet QSOs is not simply one of
host morphology. While spiral galaxies almost exclusively host radio-quiet
QSOs, ellipticals can host either radio-louds or radio-quiets. We find that a
combination of accretion rate and host scale determines which type of QSO a
given elliptical galaxy will host. QSOs with high x-ray luminosities (above
10^44.5 erg/s at 0.5 keV) are mostly radio-loud. But those with low
luminosities divide fairly neatly in size (measured by the half-light radius,
r_e). Those larger than about 10 kpc are radio-loud, while smaller ones are
radio-quiet. It has recently been found that core and coreless ellipticals are
also divided near this limit. This implies that for low-luminosity QSOs,
radio-louds are found in core ellipticals, while radio-quiets are in coreless
ellipticals and spirals. This segregation also shows up strongly for
low-redshift objects, and in general, there is a loss over time of coreless,
radio-loud QSOs. Since the presence or absence of a core may be tied to the
galactic merger history, we have an evolutionary explanation for the
differences between radio-loud and radio-quiet QSOs. |
Dark matter concentrations and a search for cores in Milky Way dwarf
satellites: We investigate the mass distributions within eight classical Milky Way dwarf
spheroidal galaxies (MW dSphs) using an equilibrium Jeans analysis and we
compare our results to the mass distributions predicted for subhalos in
dissipationless \Lambda CDM simulations. In order to match the dark matter
density concentrations predicted, the stars in these galaxies must have a
fairly significant tangential velocity dispersion anisotropy (\beta ~-1.5). For
the limiting case of an isotropic velocity dispersion (\beta =0), the classical
MW dSphs predominantly prefer to live in halos that are less concentrated than
\Lambda CDM predictions. We also investigate whether the dSphs prefer to live
in halos with constant density cores in the limit of isotropic velocity
dispersion. Interestingly, even in this limit, not all of the dSphs prefer
large constant-density cores: the Sculptor dSph prefers a cusp while Carina,
Draco and Leo I prefer cores. The other four dSphs do not show a statistically
significant preference for either cuspy or cored profiles. Finally, we
re-examine the hypothesis that the density profiles of these eight MW dSphs can
be quantified by a common dark matter halo. | Inflation with scalar-tensor theory of gravity: The latest released data from Planck in 2018, put up tighter constraints on
inflationary parameters. In the present article, the in-built symmetry of the
non-minimally coupled scalar-tensor theory of gravity is used to fix the
coupling parameter, the functional Brans-Dicke parameter, and the potential of
the theory. It is found that all the three different power-law potentials and
one exponential, pass these constraints comfortably, and also gracefully exit
from inflation. |
Emergent universe scenario and the low CMB multipoles: In this work we study superinflation in the context of the emergent universe
(EU) scenario. The existence of a superinflating phase before the onset of
slow-roll inflation arises in any emergent universe model. We found that the
superinflationary period in the EU scenario produces a suppression of the CMB
anisotropies at large scale which could be responsible for the observed lack of
power at large angular scales of the CMB. | A marked correlation function for constraining modified gravity models: Future large scale structure surveys will provide increasingly tight
constraints on our cosmological model. These surveys will report results on the
distance scale and growth rate of perturbations through measurements of Baryon
Acoustic Oscillations and Redshift-Space Distortions. It is interesting to ask:
what further analyses should become routine, so as to test as-yet-unknown
models of cosmic acceleration? Models which aim to explain the accelerated
expansion rate of the Universe by modifications to General Relativity often
invoke screening mechanisms which can imprint a non-standard density dependence
on their predictions. This suggests density-dependent clustering as a `generic'
constraint. This paper argues that a density-marked correlation function
provides a density-dependent statistic which is easy to compute and report and
requires minimal additional infrastructure beyond what is routinely available
to such survey analyses. We give one realization of this idea and study it
using low order perturbation theory. We encourage groups developing modified
gravity theories to see whether such statistics provide discriminatory power
for their models. |
Stellar Clusters in M83: Formation, evolution, disruption and the
influence of environment: We study the stellar cluster population in two adjacent fields in the nearby,
face-on spiral galaxy, M83, using WFC3/HST imaging. The clusters are selected
through visual inspection to be centrally concentrated, symmetric, and resolved
on the images, which allows us to differentiate between clusters and likely
unbound associations. We compare our sample with previous studies and show that
the differences between the catalogues are largely due to the inclusion of
large numbers of diffuse associations within previous catalogues. The
luminosity function of the clusters is well approximated by a power-law with
index, -2, over most of the observed range, however a steepening is seen at M_V
= -9.3 and -8.8 in the inner and outer fields, respectively. Additionally, we
show that the cluster population is inconsistent with a pure power-law mass
distribution, but instead exhibits a truncation at the high mass end. If
described as a Schechter function, the characteristic mass is 1.6 and 0.5 *
10^5 Msun, for the inner and outer fields, respectively, in agreement with
previous estimates of other cluster populations in spiral galaxies. Comparing
the predictions of the mass independent disruption (MID) and mass dependent
disruption (MDD) scenarios with the observed distributions, we find that both
models can accurately fit the data. However, for the MID case, the fraction of
clusters destroyed (or mass lost) per decade in age is dependent on the
environment, hence, the age/mass distributions of clusters are not universal.
In the MDD case, the disruption timescale scales with galactocentric distance
(being longer in the outer regions of the galaxy) in agreement with analytic
and numerical predictions. Finally, we discuss the implications of our results
on other extragalactic surveys, focussing on the fraction of stars that form in
clusters and the need (or lack thereof) for infant mortality. | The Sloan Lens ACS Survey. X. Stellar, Dynamical, and Total Mass
Correlations of Massive Early-type Galaxies: We use stellar masses, photometry, lensing, and velocity dispersions to
investigate empirical correlations for the final sample of 73 early-type lens
galaxies (ETGs) from the SLACS survey. The traditional correlations
(Fundamental Plane [FP] and its projections) are consistent with those found
for non-lens galaxies, supporting the thesis that SLACS lens galaxies are
representative of massive ETGs. The addition of strong lensing estimates of the
total mass allows us to gain further insights into their internal structure: i)
the mean slope of the total mass density profile is <gamma'> = 2.078+/-0.027
with an intrinsic scatter of 0.16+/-0.02; ii) gamma' correlates with effective
radius and central mass density, in the sense that denser galaxies have steeper
profiles; iii) the dark matter fraction within reff/2 is a monotonically
increasing function of galaxy mass and size; iv) the dimensional mass M_dim is
proportional to the total mass, and both increase more rapidly than stellar
mass M*; v) the Mass Plane (MP), obtained by replacing surface brightness with
surface mass density in the FP, is found to be tighter and closer to the virial
relation than the FP and the M*P, indicating that the scatter of those
relations is dominated by stellar population effects; vi) we construct the
Fundamental Hyper-Plane by adding stellar masses to the MP and find the M*
coefficient to be consistent with zero and no residual intrinsic scatter. Our
results demonstrate that the dynamical structure of ETGs is not scale invariant
and that it is fully specified by the total mass, r_eff, and sigma. Although
the basic trends can be explained qualitatively in terms of varying star
formation efficiency as a function of halo mass and as the result of dry and
wet mergers, reproducing quantitatively the observed correlations and their
tightness may be a significant challenge for galaxy formation models. |
A Kiloparsec-Scale Binary Active Galactic Nucleus Confirmed by the
Expanded Very Large Array: We report the confirmation of a kpc-scale binary active galactic nucleus
(AGN) with high-resolution radio images from the Expanded Very Large Array
(EVLA). SDSS J150243.1+111557 is a double-peaked [O III] AGN at z = 0.39
selected from the Sloan Digital Sky Survey. Our previous near-infrared adaptive
optics imaging reveals two nuclei separated by 1.4" (7.4 kpc), and our optical
integral-field spectroscopy suggests that they are a type-1--type-2 AGN pair.
However, these data alone cannot rule out the single AGN scenario where the
narrow emission-line region associated with the secondary is photoionized by
the broad-line AGN in the primary. Our new EVLA images at 1.4, 5.0, and 8.5 GHz
show two steep-spectrum compact radio sources spatially coincident with the
optical nuclei. The radio power of the type-2 AGN is an order-of-magnitude in
excess of star-forming galaxies with similar extinction-corrected [O II] 3727
luminosities, indicating that the radio emission is powered by accretion.
Therefore, SDSS J150243.1+111557 is one of the few confirmed kpc-scale binary
AGN systems. Spectral-energy-distribution modeling shows that SDSS
J150243.1+111557 is a merger of two ~10^{11} M_sun galaxies. With both black
hole masses around 10^8 Msun, the AGNs are accreting at ~10 times below the
Eddington limit. | Effects of grain size distribution on the interstellar dust mass growth: Grain growth by the accretion of metals in interstellar clouds (called `grain
growth') could be one of the dominant processes that determine the dust content
in galaxies. The importance of grain size distribution for the grain growth is
demonstrated in this paper. First, we derive an analytical formula that gives
the grain size distribution after the grain growth in individual clouds for any
initial grain size distribution. The time-scale of the grain growth is very
sensitive to grain size distribution, since the grain growth is mainly
regulated by the surface to volume ratio of grains. Next, we implement the
results of grain growth into dust enrichment models of entire galactic system
along with the grain formation and destruction in the interstellar medium,
finding that the grain growth in clouds governs the dust content in nearby
galaxies unless the grain size is strongly biased to sizes larger than $\sim
0.1 \micron$ or the power index of the grain size distribution is shallower
than $\sim -2.5$. The grain growth in clouds contributes to the rapid increase
of dust-to-gas ratio at a certain metallicity level (called critical
metallicity in Asano et al. 2011 and and Inoue 2011), which we find to be
sensitive to grain size distribution. Thus, the grain growth efficiently
increase the dust mass not only in nearby galaxies but also in high-redshift
quasars, whose metallicities are larger than the critical value. Our recipe for
the grain growth is applicable for any grain size distribution and easily
implemented into any framework of dust enrichment in galaxies. |
Galactic chemical evolution in hierarchical formation models - I.
Early-type galaxies in the local Universe: We study the metallicities and abundance ratios of early-type galaxies in
cosmological semi-analytic models (SAMs) within the hierarchical galaxy
formation paradigm. To achieve this we implemented a detailed galactic chemical
evolution (GCE) model and can now predict abundances of individual elements for
the galaxies in the semi-analytic simulations. This is the first time a SAM
with feedback from Active Galactic Nuclei (AGN) has included a chemical
evolution prescription that relaxes the instantaneous recycling approximation.
We find that the new models are able to reproduce the observed mass-metallicity
(M*-[Z/H]) relation and, for the first time in a SAM, we reproduce the observed
positive slope of the mass-abundance ratio (M*-[$alpha$/Fe]) relation. Our
results indicate that in order to simultaneously match these observations of
early-type galaxies, the use of both a very mildly top-heavy IMF (i.e., with a
slope of x=1.15 as opposed to a standard x=1.3), and a lower fraction of
binaries that explode as Type Ia supernovae appears to be required. We also
examine the rate of supernova explosions in the simulated galaxies. In
early-type (non-star forming) galaxies, our predictions are also consistent
with the observed SNe rates. However, in star-forming galaxies, a higher
fraction of SN Ia binaries than in our preferred model is required to match the
data. If, however, we deviate from the classical model and introduce a
population of SNe Ia with very short delay times, our models simultaneously
produce a good match to the observed metallicities, abundance ratios and SN
rates. | Non-Gaussian estimates of tensions in cosmological parameters: We discuss how to efficiently and reliably estimate the level of agreement
and disagreement on parameter determinations from different experiments, fully
taking into account non-Gaussianities in the parameter posteriors. We develop
two families of scalable algorithms that allow us to perform this type of
calculations in increasing number of dimensions and for different levels of
tensions. One family of algorithms rely on kernel density estimates of
posterior distributions while the other relies on machine learning modeling of
the posterior distribution with normalizing flows. We showcase their
effectiveness and accuracy with a set of benchmark examples and find both
methods agree with each other and the true tension within $0.5\sigma$ in
difficult cases and generally to $0.2\sigma$ or better. This allows us to study
the level of internal agreement between different measurements of the
clustering of cosmological structures from the Dark Energy Survey and their
agreement with measurements of the Cosmic Microwave Background from the Planck
satellite. |
The Origin of the Mass-Metallicity relation: an analytical approach: The existence of a mass-metallicity (MZ) relation in star forming galaxies at
all redshift has been recently established. We aim at studying some possible
physical mechanisms contributing to the MZ relation by adopting analytical
solutions of chemical evolution models including infall and outflow. We explore
the hypotheses of a variable galactic wind rate, infall rate and yield per
stellar generation (i.e. a variation in the IMF), as possible causes for the MZ
relation. By means of analytical models we compute the expected O abundance for
galaxies of a given total baryonic mass and gas mass.The stellar mass is
derived observationally and the gas mass is derived by inverting the Kennicutt
law of star formation, once the star formation rate is known. Then we test how
the parameters describing the outflow, infall and IMF should vary to reproduce
the MZ relation, and we exclude the cases where such a variation leads to
unrealistic situations. We find that a galactic wind rate increasing with
decreasing galactic mass or a variable IMF are both viable solutions for the MZ
relation. A variable infall rate instead is not acceptable. It is difficult to
disentangle among the outflow and IMF solutions only by considering the MZ
relation, and other observational constraints should be taken into account to
select a specific solution. For example, a variable efficiency of star
formation increasing with galactic mass can also reproduce the MZ relation and
explain the downsizing in star formation suggested for ellipticals. The best
solution could be a variable efficiency of star formation coupled with galactic
winds, which are indeed observed in low mass galaxies. | EDGES and JWST with 21cm global signal emulator: The 21cm global signal is an important probe to reveal the properties of the
first astrophysical objects and the processes of the structure formation from
which one can constrain astrophysical and cosmological parameters. To extract
the information of such parameters, one needs to efficiently evaluate the 21cm
global signal for statistical analysis. First we developed an artificial neural
network-based emulator to predict the 21cm global signal, which works with
significantly less computational cost and high precision. Then we apply our
emulator to demonstrate the parameter estimation based on the Bayesian analysis
by using the publicly available EDGES low-band data. We find that the result is
sensitive to the foreground model, the assumption of noise, and the frequency
range used in the analysis. The Bayesian evidence suggests the models with
higher order polynomial function and enhanced noise are preferred. We also
compare models suggested from the EDGES low-band data and the ones from recent
JWST measurements of the galaxy luminosity function at $z=16$. We find that the
model which produces the 21cm absorption line at $z\approx15$ is well
consistent with the central value of the observed luminosity function at
$z=16$. |
Detection of Exoplanets in M31 with Pixel-Lensing: The Event Pa-99-N2
Case: We show that exoplanets in the M31 galaxy may be detected with the
pixel-lensing method by using telescopes making high cadence observations of an
ongoing microlensing event. Although the mean mass for detectable exoplanets is
about $2 M_{\rm {J}}$, even small mass exoplanets ($M_{\rm P} < 20 M_{\oplus}$)
can cause significant deviations, which are observable with large telescopes.
We reanalysed the POINT-AGAPE microlensing event PA-99-N2. First, we test the
robustness of the binary lens conclusion for this light curve. Second, we show
that for such long duration and bright microlensing events, the efficiency for
finding planetary-like deviations is strongly enhanced. | A Sparse Spectroscopic Supernova Survey: Supernova cosmology surveys are traditionally time consuming, especially for
the critical spectroscopic data. However, a single spectrum at maximum light
may provide accurate distance estimation if recent developments hold. This
could open up a new type of supernova cosmology survey, with a useful
interaction between the spectra and a focus on specific redshifts. We optimize
the redshift selection and show that this condensed survey could efficiently
deliver highly accurate dark energy constraints. |
Responses in Large-Scale Structure: We introduce a rigorous definition of general power-spectrum responses as
resummed vertices with two hard and $n$ soft momenta in cosmological
perturbation theory. These responses measure the impact of long-wavelength
perturbations on the local small-scale power spectrum. The kinematic structure
of the responses (i.e., their angular dependence) can be decomposed
unambiguously through a "bias" expansion of the local power spectrum, with a
fixed number of physical response coefficients, which are only a function of
the hard wavenumber $k$. Further, the responses up to $n$-th order completely
describe the $(n+2)$-point function in the squeezed limit, i.e. with two hard
and $n$ soft modes, which one can use to derive the response coefficients. This
generalizes previous results, which relate the angle-averaged squeezed limit to
isotropic response coefficients. We derive the complete expression of first-
and second-order responses at leading order in perturbation theory, and present
extrapolations to nonlinear scales based on simulation measurements of the
isotropic response coefficients. As an application, we use these results to
predict the non-Gaussian part of the angle-averaged matter power spectrum
covariance ${\rm Cov}^{\rm NG}_{\ell = 0}(k_1,k_2)$, in the limit where one of
the modes, say $k_2$, is much smaller than the other. Without any free
parameters, our model results are in very good agreement with simulations for
$k_2 \lesssim 0.06\ h/{\rm Mpc}$, and for any $k_1 \gtrsim 2 k_2$. The
well-defined kinematic structure of the power spectrum response also permits a
quick evaluation of the angular dependence of the covariance matrix. While we
focus on the matter density field, the formalism presented here can be
generalized to generic tracers such as galaxies. | Towards detection of relativistic effects in galaxy number counts using
kSZ Tomography: High-resolution, low-noise observations of the cosmic microwave background
(CMB) planned for the near-future will enable new cosmological probes based on
re-scattered CMB photons -- the secondary CMB. At the same time, enormous
galaxy surveys will map out huge volumes of the observable Universe. Using the
technique of kinetic Sunyaev Zel'dovich (kSZ) tomography these new probes can
be combined to reconstruct the remote dipole field, the CMB dipole as observed
from different vantage points in our Universe. The volume accessible to future
galaxy surveys is large enough that general relativistic corrections to the
observed distribution of galaxies must be taken into account. These corrections
are interesting probes of gravity in their own right, but can also obscure
potential signatures of primordial non-Gaussianity. In this paper, we
demonstrate that correlations between the reconstructed remote dipole field and
the observed galaxy number counts can in principle be used to detect general
relativistic corrections. We show that neglecting general relativistic
corrections leads to an $\mathcal{O}(1)$ bias on the inferred amplitude of
primordial non-Gaussianity, $f_{\rm NL}$. In addition, we demonstrate that the
reconstructed remote dipole field can provide useful constraining power on
various bias parameters appearing in the galaxy number counts, and can
significantly mitigate the effects of alignment bias. |
Do quasar X-ray and UV flux measurements provide a useful test of
cosmological models?: The recent compilation of quasar (QSO) X-ray and UV flux measurements include
QSOs that appear to not be standardizable via the X-ray luminosity and UV
luminosity ($L_X-L_{UV}$) relation and so should not be used to constrain
cosmological model parameters. Here we show that the largest of seven
sub-samples in this compilation, the SDSS-4XMM QSOs that contribute about 2/3
of the total QSOs, have $L_X-L_{UV}$ relations that depend on the cosmological
model assumed and also on redshift, and is the main cause of the similar
problem discovered earlier for the full QSO compilation. The second and third
biggest sub-samples, the SDSS-Chandra and XXL QSOs that together contribute
about 30% of the total QSOs, appear standardizable, but provide only weak
constraints on cosmological parameters that are not inconsistent with the
standard spatially-flat $\Lambda$CDM model or with constraints from
better-established cosmological probes. | Non-Gaussian error bars in galaxy surveys -- II: (Abridged) Estimating the uncertainty on the matter power spectrum internally
(i.e. directly from the data) is made challenging by the simple fact that
galaxy surveys offer at most a few independent samples. In addition, surveys
have non-trivial geometries, which make the interpretation of the observations
even trickier, but the uncertainty can nevertheless be worked out within the
Gaussian approximation. With the recent realization that Gaussian treatments of
the power spectrum lead to biased error bars about the dilation of the baryonic
acoustic oscillation scale, efforts are being directed towards developing
non-Gaussian analyses, mainly from N-body simulations so far. Unfortunately,
there is currently no way to tell how the non-Gaussian features observed in the
simulations compare to those of the real Universe, and it is generally hard to
tell at what level of accuracy the N-body simulations can model complicated
non-linear effects such as mode coupling and galaxy bias. We propose in this
paper a novel method that aims at measuring non-Gaussian error bars on the
matter power spectrum directly from galaxy survey data. We utilize known
symmetries of the 4-point function, Wiener filtering and principal component
analysis to estimate the full covariance matrix from only four independent
fields with minimal prior assumptions. With the noise filtering techniques and
only four fields, we are able to recover the Fisher information obtained from a
large N=200 sample to within 20 per cent, for k < 1.0 h/Mpc. Finally, we
provide a prescription to extract a noise-filtered, non-Gaussian, covariance
matrix from a handful of fields in the presence of a survey selection function. |
On the total cosmological information in galaxy clustering: an
analytical approach: Beyond the linear regime of structure formation, part of cosmological
information encoded in galaxy clustering becomes inaccessible to the usual
power spectrum. "Sufficient statistics", A*, were introduced recently to
recapture the lost, and ultimately extract all, cosmological information. We
present analytical approximations for the A* and traditional power spectra as
well as for their covariance matrices in order to calculate analytically their
cosmological information content in the context of Fisher information theory.
Our approach allows the precise quantitative comparison of the techniques with
each other and to the total information in the data, and provides insights into
sufficient statistics. In particular, we find that while the A* power spectrum
has a similar shape to the usual galaxy power spectrum, its amplitude is
strongly modulated by small scale statistics. This effect is mostly responsible
for the ability of the A* power spectrum to recapture the information lost for
the usual power spectrum. We use our framework to forecast the best achievable
cosmological constraints for projected surveys as a function of their galaxy
density, and compare the information content of the two power spectra. We find
that sufficient statistics extract all cosmological information, resulting in
an approximately factor of ~2 gain for dense projected surveys at low redshift.
This increase in the effective volume of projected surveys is consistent with
previous numerical calculations. | The Coyote Universe Extended: Precision Emulation of the Matter Power
Spectrum: Modern sky surveys are returning precision measurements of cosmological
statistics such as weak lensing shear correlations, the distribution of
galaxies, and cluster abundance. To fully exploit these observations, theorists
must provide predictions that are at least as accurate as the measurements, as
well as robust estimates of systematic errors that are inherent to the modeling
process. In the nonlinear regime of structure formation, this challenge can
only be overcome by developing a large-scale, multi-physics simulation
capability covering a range of cosmological models and astrophysical processes.
As a first step to achieving this goal, we have recently developed a prediction
scheme for the matter power spectrum (a so-called emulator), accurate at the 1%
level out to k~1/Mpc and z=1 for wCDM cosmologies based on a set of
high-accuracy N-body simulations. It is highly desirable to increase the range
in both redshift and wavenumber and to extend the reach in cosmological
parameter space. To make progress in this direction, while minimizing
computational cost, we present a strategy that maximally re-uses the original
simulations. We demonstrate improvement over the original spatial dynamic range
by an order of magnitude, reaching k~10 h/Mpc, a four-fold increase in redshift
coverage, to z=4, and now include the Hubble parameter as a new independent
variable. To further the range in k and z, a new set of nested simulations run
at modest cost is added to the original set. The extension in h is performed by
including perturbation theory results within a multi-scale procedure for
building the emulator. This economical methodology still gives excellent error
control, ~5% near the edges of the domain of applicability of the emulator. A
public domain code for the new emulator is released as part of the work
presented in this paper. |
Global alignments of parsec-scale AGN radio jets and their polarization
planes: A number of works reported on the existence of a large scale alignment of the
polarization plane of extragalactic sources as well as the alignment of
radio-sources structural axes. However, both claims and their interpretation
remain controversial. For the first time we explore the parsec-scale jets
alignments. Additionally, we use archival polarimetric data at different
wavelengths in order to compare relative orientations of the jets and the
polarization planes of their emission. Using the flux density distribution in
very long baseline interferometry (VLBI) radio maps from the Astrogeo database,
we determine the parsec-scale jet orientation for the largest sample of active
galactic nuclei (AGN) to date. Employing the method of parallel transport and a
sample statistics characterizing the jet orientation dispersion among
neighbors, we test whether the identified jets are significantly aligned. We
show that the parsec-scale jets in our sample do not demonstrate any
significant global alignments. Moreover, the jet direction is found to be
weakly correlated with the polarization plane direction at different
frequencies. | Probing Dynamics of Boson Stars by Fast Radio Bursts and Gravitational
Wave Detection: Boson stars may consist of a new type of light singlet scalar particles with
nontrivial self-interactions, and may compose a fraction of the dark matter in
the Universe. In this work, we study the dynamics of boson stars with Liouville
and logarithmic scalar self-interaction potentials as benchmarks. We perform a
numerical analysis as well as a semi-analytic study on how the compactness and
the total mass will deviate from that of the usual boson stars formed with a
quartic repulsive self-interaction. We apply the recently suggested Swampland
conjecture to examine whether boson stars with such benchmark potentials belong
to the Landscape of a quantum gravity. Using the mass constraint on the
macroscopic compact halo object (MACHO) and the cold dark matter (CDM)
isocurvature mode constraint from the cosmic microwave background (CMB), we
derive the allowed mass range of scalar particles which compose the boson star.
We further analyze applications of the lensing of fast radio bursts (FRBs) and
the gravitational wave (GW) detection to probe the presence of such boson stars
and constrain the parameter space of their corresponding models. We discuss how
the two types of boson star potentials can be discriminated by the FRB and GW
measurements. |
Weakening gravity for dark matter in a type-II minimally modified
gravity: We propose a new cosmological framework in which the strength of the
gravitational force acted on dark matter at late time can be weaker than that
on the standard matter fields without introducing extra gravitational degrees
of freedom. The framework integrates dark matter into a type-II minimally
modified gravity that was recently proposed as a dark energy mimicker. The idea
that makes such a framework possible consists of coupling a dark matter
Lagrangian and a cosmological constant to the metric in a canonically
transformed frame of general relativity (GR). On imposing a gauge fixing
constraint, which explicitly breaks the temporal diffeomorphism invariance, we
keep the number of gravitational degrees of freedom to be two, as in GR. We
then make the inverse canonical transformation to bring the theory back to the
original frame, where one can add the standard matter fields. This framework
contains two free functions of time which specify the generating functional of
the above mentioned canonical transformation and which are then used in order
to realize desired time evolutions of both the Hubble expansion rate $H(z)$ and
the effective gravitational constant for dark matter $G_{\rm eff}(z)$. The aim
of this paper is therefore to provide a new framework to address the two
puzzles present in today's cosmology, i.e. the $H_0$ tension and the $S_8$
tension, simultaneously. When the dark matter is cold in this framework, we dub
the corresponding cosmological model the V Canonical Cold Dark Matter (VCCDM),
as the cosmological constant $\Lambda$ in the standard $\Lambda$CDM is replaced
by a function $V(\phi)$ of an auxiliary field $\phi$ and the CDM is minimally
coupled to the metric in a canonically transformed frame. | Evidence for Morphology and Luminosity Transformation of Galaxies at
High Redshifts: We study the galaxy morphology-luminosity-environmental relation and its
redshift evolution using a spectroscopic sample of galaxies in the Great
Observatories Origins Deep Survey (GOODS). In the redshift range of $0.4\leq
z\leq1.0$ we detect conformity in morphology between neighboring galaxies. The
realm of conformity is confined within the virialized region associated with
each galaxy plus dark matter halo system. When a galaxy is located within the
virial radius of its nearest neighbor galaxy, its morphology strongly depends
on the neighbor's distance and morphology: the probability for a galaxy to be
an early type ($f_E$) strongly increases as it approaches an early-type
neighbor, but tends to decrease as it approaches a late-type neighbor. We find
that $f_E$ evolves much faster in high density regions than in low density
regions, and that the morphology-density relation becomes significantly weaker
at $z\approx 1$. This may be because the rate of galaxy-galaxy interactions is
higher in high density regions, and a series of interactions and mergers over
the course of galaxy life eventually transform late types into early types. We
find more isolated galaxies are more luminous, which supports luminosity
transformation through mergers at these redshifts. Our results are consistent
with those from nearby galaxies, and demonstrate that galaxy-galaxy
interactions have been strongly affecting the galaxy evolution over a long
period of time. |
The Real Problem with MOND: Gravitational potentials in the cosmos are deeper than expected from observed
visible objects, a phenomenon usually attributed to dark matter, presumably in
the form of a new fundamental particle. Until such a particle is observed, the
jury remains out on dark matter, and modified gravity models must be
considered. The class of models reducing to MOdified Newtonian Dynamics (MOND)
in the weak field limit does an excellent job fitting the rotation curves of
galaxies, predicting the relation between baryonic mass and velocity in
gas-dominated galaxies, and explaining the properties of the local group.
Several of the initial challenges facing MOND have been overcome, while others
remain. Here I point out the most severe challenge facing MOND. | Interacting Viscous Dark Energy in Bianchi Type-III Universe: In this paper we study the evolution of the equation of state of viscous dark
energy in the scope of Bianchi type III space-time. We consider the case when
the dark energy is minimally coupled to the perfect fluid as well as direct
interaction with it. The viscosity and the interaction between the two fluids
are parameterized by constants $\zeta_{0}$ and $\sigma$ respectively. We have
made a detailed investigation on the cosmological implications of this
parametrization. To differentiate between different dark energy models, we have
performed a geometrical diagnostic by using the statefinder pair $\{s, r\}$. |
Core Fragmentation in Simplest Superfluid Dark Matter Scenario: We study the structure of galactic halos within a scalar dark matter model,
endowed with a repulsive quartic self-interaction, capable of undergoing the
superfluid phase transition in high-density regions. We demonstrate that the
thermalized cores are prone to fragmentation into superfluid droplets due to
the Jeans instability. Furthermore, since cores of astrophysical size may be
generated only when most of the particles comprising the halo reside in a
highly degenerate phase-space, the well-known bound on the dark matter
self-interaction cross section inferred from the collision of clusters needs to
be revised, accounting for the enhancement of the interaction rate due to
degeneracy. As a result, generation of kpc-size superfluid solitons, within the
parameter subspace consistent with the Bullet Cluster bound, requires dark
matter particles to be ultra-light. | Early Universe with CMB polarization: The Universe is the grandest conceivable scale on which the human mind can
strive to understand nature. The amazing aspect of cosmology, the branch of
science that attempts to understand the origin and evolution of the Universe,
is that it is largely comprehensible by applying the same basic laws of physics
that we use for other branches of physics. The observed cosmic microwave
background (CMB) is understood by applying the basic laws of radiative
processes and transfer, masterfully covered in the classic text by S.
Chandrasekhar, in the cosmological context. In addition to the now widely
acclaimed temperature anisotropy, there is also linear polarization information
imprinted on the observed Cosmic Microwave background. CMB polarization already
has addressed, and promises to do a lot more, to unravel the deepest
fundamental queries about physics operating close to the origin of the
Universe. |
Screened Fifth Forces Mediated by Dark Matter-Baryon Interactions:
Theory and Astrophysical Probes: We derive the details of a new screening mechanism where the interactions of
baryons and dark matter can be screened according to the local dark matter
density. In this mechanism, the value of Newton's constant is dark matter
density-dependent, allowing for the possibility that astrophysical phenomena
are very different in galaxies less dense than the Milky Way. The parameterized
post Newtonian parameter $\gamma$, which quantifies the difference between
kinematical and lensing probes, also depends on dark matter density. We
calculate the effects of varying $G$ on various stages of stellar evolution,
focusing on observables that impact cosmology: the Cepheid period--luminosity
relation and the supernova Ia magnitude--redshift relation. Other potential
tests of the model are also investigated including main-sequence, post-main
sequence, and low mass dwarf stars. Finally, we discuss how extragalactic tests
of $\gamma$ could provide complementary constraints. | The Breakdown Scale of HI Bias Linearity: The 21 cm intensity mapping experiments promise to obtain the large-scale
distribution of HI gas at the post-reionization epoch. In order to reveal the
underlying matter density fluctuations from the HI mapping, it is important to
understand how HI gas traces the matter density distribution. Both nonlinear
halo clustering and nonlinear effects modulating HI gas in halos may determine
the scale below which the HI bias deviates from linearity. We employ three
approaches to generate the mock HI density from a large-scale N-body simulation
at low redshifts, and demonstrate that the assumption of HI linearity is valid
at the scale corresponding to the first peak of baryon acoustic oscillations,
but breaks down at $k \gtrsim 0.1\,h\, {\rm Mpc}^{-1}$. The nonlinear effects
of halo clustering and HI content modulation counteract each other at small
scales, and their competition results in a model-dependent "sweet-spot"
redshift near $z$=1 where the HI bias is scale-independent down to small
scales. We also find that the linear HI bias scales approximately linearly with
redshift for $z\le 3$. |
The Little Rip: We examine models in which the dark energy density increases with time (so
that the equation-of-state parameter w satisfies w < -1), but w approaches -1
asymptotically, such that there is no future singularity. We refine previous
calculations to determine the conditions necessary to produce this evolution.
Such models can display arbitrarily rapid expansion in the near future, leading
to the destruction of all bound structures (a "little rip"). We determine
observational constraints on these models and calculate the point at which the
disintegration of bound structures occurs. For the same present-day value of w,
a big rip with constant w disintegrates bound structures earlier than a little
rip. | The $H_0$ tension alleviated through ultra-light primordial black holes:
an information insight through gravitational waves: The Hawking evaporation of ultra-light primordial black holes (PBH)
dominating the early Universe before Big Bang Nucleosynthesis can potentially
increase the effective number of extra neutrino species $\Delta N_\mathrm{eff}$
through the emission of dark radiation degrees of freedom alleviating in this
way the $H_0$ tension problem. Interestingly, these light PBHs can form a gas
of Poisson distributed compact objects which can induce a gravitational-wave
(GW) background due to second order gravitational interactions. Therefore, by
considering the contribution to $\Delta N_\mathrm{eff}$ due to the production
of the aforementioned GW background we revisit in this work the constraints on
the relevant parameters at hand, namely the PBH mass, $m_\mathrm{PBH}$, the
initial PBH abundance at PBH formation time, $\Omega_\mathrm{PBH,f}$ and the
number of DR radiation degrees of freedom, $g_\mathrm{DR}$ by accounting at the
same time for the relevant upper bounds constraints on $\Delta N_\mathrm{eff}$
from the Planck collaboration. |
Non-Gaussianity after many-field reheating: We numerically investigate reheating after quadratic inflation with up to 65
fields, focusing on the production of non-Gaussianity. We consider several sets
of initial conditions, masses and decay rates. As expected we find that the
reheating phase can have a significant effect on the non-Gaussian signal, but
that for this number of fields a detectable level of non-Gaussianity requires
the initial conditions, mass range and decay rates to be ordered in a
particular way. We speculate on whether this might change in the N-flation
limit. | The Misalignments between Matter and Galaxy Distributions in Triaxial
Clusters: A Signature of a Possible Fifth Force?: The standard structure formation model based on a LCDM cosmology predicts
that the galaxy clusters have triaxial shapes and that the cluster galaxies
have a strong tendency to be located preferentially along the major axes of
host cluster's dark matter distributions due to the gravitational tidal effect.
The predicted correlations between dark matter and galaxy distributions in
triaxial clusters are insensitive to the initial cosmological parameters and to
the galaxy bias, and thus can provide a unique test-bed for the nonlinear
structure formation of the LCDM cosmology. Recently, Oguri et al. determined
robustly the dark matter distributions in the galaxy clusters using the two
dimensional weak lensing shear fitting and showed that the orientations of the
cluster galaxy distributions are only very weakly correlated with those of the
underlying dark matter distributions determined robustly, which is in contrast
to with the LCDM-based prediction. We reanalyze and compare quantitatively the
observational result with the LCDM-based prediction from the Millennium Run
simulation with the help of the bootstrap resampling and generalized
chi^{2}-statistics. The hypothesis that the observational result is consistent
with the LCDM-based prediction is ruled out at the 99% confidence level. A
local fifth force induced by a non-minimal coupling between dark energy and
dark matter might be responsible for the observed misalignments between dark
matter and galaxy distributions in triaxial clusters. |
Neutrinos in Non-linear Structure Formation - The Effect on Halo
Properties: We use N-body simulations to find the effect of neutrino masses on halo
properties, and investigate how the density profiles of both the neutrino and
the dark matter components change as a function of the neutrino mass. We
compare our neutrino density profiles with results from the N-one-body method
and find good agreement. We also show and explain why the Tremaine-Gunn bound
for the neutrinos is not saturated. Finally we study how the halo mass function
changes as a function of the neutrino mass and compare our results with the
Sheth-Tormen semi-analytic formulae. Our results are important for surveys
which aim at probing cosmological parameters using clusters, as well as future
experiments aiming at measuring the cosmic neutrino background directly. | Cold dust clumps in dynamically hot gas: We present clumps of dust emission from Herschel observations of the Large
Magellanic Cloud (LMC) and their physical and statistical properties. We
catalog cloud features seen in the dust emission from Herschel observations of
the LMC, the Magellanic type irregular galaxy closest to the Milky Way, and
compare these features with HI catalogs from the ATCA+Parkes HI survey. Using
an automated cloud-finding algorithm, we identify clouds and clumps of dust
emission and examine the cumulative mass distribution of the detected dust
clouds. The mass of cold dust is determined from physical parameters that we
derive by performing spectral energy distribution fits to 250, 350, and 500
micronm emission from SPIRE observations using DUSTY and GRASIL radiative
transfer calculation with dust grain size distributions for graphite/silicate
in low-metallicity extragalactic environments. The dust cloud mass spectrum
follows a power law distribution with an exponent of gamma=-1.8 for clumps
larger than 400 solar mass and is similar to the HI mass distribution. This is
expected from the theory of ISM structure in the vicinity of star formation. |
Infrared-red Cores in Nearby Elliptical Galaxies: We present the Spitzer Space Telescope Infrared Array Camera (IRAC)
observations for a sample of local elliptical galaxies to study later stages of
AGN activities. A sample of 36 elliptical galaxies is selected from the Palomar
spectroscopic survey. We detect nuclear non-stellar infrared emission in 9 of
them. There is unambiguous evidence of circumnuclear dust in these 9 galaxies
in their optical images. We also find a remarkable correlation between the
infrared excess emission and the nuclear radio/X-ray emission, suggesting that
infrared excess emission is tightly related with nuclear activity. Possible
origin of infrared excess emission from hot dust heated by the central AGN is
supported by spectral indices of IR excess emission. | The Knotted Sky II: Does BICEP2 require a nontrivial primordial power
spectrum?: An inflationary gravitational wave background consistent with BICEP2 is
difficult to reconcile with a simple power-law spectrum of primordial scalar
perturbations. Tensor modes contribute to the temperature anisotropies at
multipoles with $l\lesssim 100$, and this effect --- together with a prior on
the form of the scalar perturbations --- was the source of previous bounds on
the tensor-to-scalar ratio. We compute Bayesian evidence for combined fits to
BICEP2 and Planck for three nontrivial primordial spectra: a) a running
spectral index, b) a cutoff at fixed wavenumber, and c) a spectrum described by
a linear spline with a single internal knot. We find no evidence for a cutoff,
weak evidence for a running index, and significant evidence for a "broken"
spectrum. Taken at face-value, the BICEP2 results require two new inflationary
parameters in order to describe both the broken scale invariance in the
perturbation spectrum and the observed tensor-to-scalar ratio. Alternatively,
this tension may be resolved by additional data and more detailed analyses. |
Exploring the liminality: properties of haloes and subhaloes in
borderline $f(R)$ gravity: We investigate the properties of dark matter haloes and subhaloes in an
$f(R)$ gravity model with $|f_{R0}|=10^{-6}$, using a very high-resolution
N-body simulation. The model is a borderline between being cosmologically
interesting and yet still consistent with current data. We find that the halo
mass function in this model has a maximum 20% enhancement compared with the
$\Lambda$CDM predictions between $z=1$ and $z=0$. Because of the chameleon
mechanism which screens the deviation from standard gravity in dense
environments, haloes more massive than $10^{13}h^{-1}M_\odot$ in this $f(R)$
model have very similar properties to haloes of similar mass in $\Lambda$CDM,
while less massive haloes, such as that of the Milky Way, can have steeper
inner density profiles and higher velocity dispersions due to their weaker
screening. The halo concentration is remarkably enhanced for low-mass haloes in
this model due to a deepening of the total gravitational potential. Contrary to
the naive expectation, the halo formation time $z_f$ is later for low-mass
haloes in this model, a consequence of these haloes growing faster than their
counterparts in $\Lambda$CDM at late times and the definition of $z_f$.
Subhaloes, especially those less massive than $10^{11}h^{-1}M_\odot$, are
substantially more abundant in this $f(R)$ model for host haloes less massive
than $10^{13}h^{-1}M_\odot$. We discuss the implications of these results for
the Milky Way satellite abundance problem. Although the overall halo and
subhalo properties in this borderline $f(R)$ model are close to their
$\Lambda$CDM predictions, our results suggest that studies of the Local Group
and astrophysical systems, aided by high-resolution simulations, can be
valuable for further tests of it. | Revisiting Generalized Chaplygin Gas as a Unified Dark Matter and Dark
Energy Model: In this paper, we revisit generalized Chaplygin gas (GCG) model as a unified
dark matter and dark energy model. The energy density of GCG model is given as
$\rho_{GCG}/\rho_{GCG0}=[B_{s}+(1-B_{s})a^{-3(1+\alpha)}]^{1/(1+\alpha)}$,
where $\alpha$ and $B_s$ are two model parameters which will be constrained by
type Ia supernova as standard candles, baryon acoustic oscillation as standard
rulers and the seventh year full WMAP data points. In this paper, we will not
separate GCG into dark matter and dark energy parts any more as adopted in the
literatures. By using Markov Chain Monte Carlo method, we find the result:
$\alpha=0.00126_{- 0.00126- 0.00126}^{+ 0.000970+ 0.00268}$ and $B_s= 0.775_{-
0.0161- 0.0338}^{+ 0.0161+ 0.0307}$. |
High-Resolution Panchromatic Spectral Models of Galaxies including
Photoionisation and Dust: An updated version of the dust radiation transfer code Sunrise, including
models for star-forming regions and a self-consistent calculation of the
spatially dependent dust and PAH emission, is presented. Given a hydrodynamic
simulation of a galaxy, this model can calculate a realistic 2-dimensional
ultraviolet--submillimeter spectral energy distribution of the galaxy,
including emission lines from HII regions, from any viewpoint. To model the
emission from star-forming regions, the MAPPINGSIII photoionization code is
used. The high wavelength resolution (~ 1000 wavelengths) is made possible by
the polychromatic Monte-Carlo algorithm employed by Sunrise. From the 2-D
spectral energy distributions, images in any filter bands or integrated galaxy
SEDs can be created. Using a suite of hydrodynamic simulations of disc
galaxies, the output broad-band images and spectral energy distributions are
compared with observed galaxies from the multiwavelength SINGS and SLUGS galaxy
surveys. Overall, the output spectral energy distributions show a good match
with observed galaxies in colours ranging from GALEX far-UV to SCUBA
submillimeter wavelengths. The only possible exception is the 160 micron/850
micron colour, which the simulations underestimate by a factor "of order 5"
compared to the SINGS sample. However, the simulations here agree with the
SLUGS galaxies, which consistently have significantly larger amounts of cold
dust than the SINGS galaxies. The Sunrise model can be used to generate
simulated observations of arbitrary hydrodynamic galaxy simulations. In this
way, predictions of galaxy formation theories can be directly tested against
observations of galaxies. | Predictions for BAO distance estimates from the cross-correlation of the
Lyman-alpha forest and redshifted 21-cm emission: We investigate the possibility of using the cross-correlation of the
Lyman-alpha forest and redshifted 21-cm emission to detect the baryon acoustic
oscillation (BAO). The standard Fisher matrix formalism is used to determine
the accuracy with which it will be possible to measure cosmological distances
using this signal. Earlier predictions indicate that it will be possible to
measure the dilation factor D_V with 1.9 % accuracy at z=2.5 from the BOSS
Lyman-alpha forest auto-correlation. In this paper we investigate if it is
possible to improve the accuracy using the cross-correlation.
We use a simple parametrization of the Lyman-alpha forest survey which very
loosely matches some properties of BOSS and predicts delta D_V/D_V = 2.0 % for
the auto-correlation at z=2.5. For the redshifted 21-cm observations we
consider individual antennas of size 2 m * 2 m distributed such that the
baselines within 250 m are uniformly sampled. It is assumed that the
observations span z=2 to 3 and covers the 10,000 deg^2 sky coverage of BOSS. We
find that for 2 years of observation with an array of 2,000 antennas, the
cross-correlation is 1.7 times more sensitive than the Lyman-alpha forest
auto-correlation. The cross-correlation is 2.7 times more sensitive than the
auto-correlation if we have 4,000 antennas and 4 years of observation. In
conclusion, we find that it is possible to significantly increase the accuracy
of the distance estimates by considering the cross-correlation signal. |
The LABOCA Survey of the Extended Chandra Deep Field South: We present a sensitive 870 micron survey of the Extended Chandra Deep Field
South (ECDFS) using LABOCA on the APEX telescope. The LABOCA ECDFS
Submillimetre Survey (LESS) covers the full 30' x 30' field size of the ECDFS
and has a uniform noise level of 1.2 mJy/beam. LESS is thus the largest
contiguous deep submillimetre survey undertaken to date. The noise properties
of our map show clear evidence that we are beginning to be affected by
confusion noise. We present a catalog of 126 SMGs detected with a significance
level above 3.7 sigma. The ECDFS exhibits a deficit of bright SMGs relative to
previously studied blank fields but not of normal star-forming galaxies that
dominate the extragalactic background light (EBL). This is in line with the
underdensities observed for optically defined high redshift source populations
in the ECDFS (BzKs, DRGs,optically bright AGN and massive K-band selected
galaxies). The differential source counts in the full field are well described
by a power law with a slope of alpha=-3.2, comparable to the results from other
fields. We show that the shape of the source counts is not uniform across the
field. The integrated 870 micron flux densities of our source-count models
account for >65% of the estimated EBL from COBE measurements. We have
investigated the clustering of SMGs in the ECDFS by means of a two-point
correlation function and find evidence for strong clustering on angular scales
<1'. Assuming a power law dependence for the correlation function and a typical
redshift distribution for the SMGs we derive a spatial correlation length of
r_0=13+/-6 h^-1 Mpc. | UV/Optical/IR Color Sequences Along the Tidal Ring/Arm of Arp 107: We construct UV/optical/IR spectral energy distributions for 29 star forming
regions in the interacting galaxy Arp 107, using GALEX UV, Sloan Digitized Sky
Survey optical, and Spitzer infrared images. In an earlier study utilizing only
the Spitzer data, we found a sequence in the mid-infrared colors of
star-forming knots along the strong tidal arm in this system. In the current
study, we find sequences in the UV/optical colors along the tidal arm that
mirror those in the mid-infrared, with blue UV/optical colors found for regions
that are red in the mid-infrared, and vice versa. With single-burst stellar
population synthesis models, we find a sequence in the average stellar age
along this arm, with younger stars preferentially located further out in the
arm. Models that allow two populations of different ages and dust attenuations
suggest that there may be both a young component and an older population
present in these regions. Thus the observed color sequences may be better
interpreted as a sequence in the relative proportion of young and old stars
along the arm, with a larger fraction of young stars near the end. Comparison
with star forming regions in other interacting galaxies shows that the Arp 107
regions are relatively quiescent, with less intense star formation than in many
other systems. |
Effective Field Theory of Dark Energy: a Review: The discovery of cosmic acceleration has triggered a consistent body of
theoretical work aimed at modeling its phenomenology and understanding its
fundamental physical nature. In recent years, a powerful formalism that
accomplishes both these goals has been developed, the so-called effective field
theory of dark energy. It can capture the behavior of a wide class of modified
gravity theories and classify them according to the imprints they leave on the
smooth background expansion history of the Universe and on the evolution of
linear perturbations. The effective field theory of dark energy is based on a
Lagrangian description of cosmological perturbations which depends on a number
of functions of time, some of which are non-minimal couplings representing
genuine deviations from General Relativity. Such a formalism is thus
particularly convenient to fit and interpret the wealth of new data that will
be provided by future galaxy surveys. Despite its recent appearance, this
formalism has already allowed a systematic investigation of what lies beyond
the General Relativity landscape and provided a conspicuous amount of
theoretical predictions and observational results. In this review, we report on
these achievements. | Precision measurement of the local bias of dark matter halos: We present accurate measurements of the linear, quadratic, and cubic local
bias of dark matter halos, using curved "separate universe" N-body simulations
which effectively incorporate an infinite-wavelength overdensity. This can be
seen as an exact implementation of the peak-background split argument. We
compare the results with the linear and quadratic bias measured from the
halo-matter power spectrum and bispectrum, and find good agreement. On the
other hand, the standard peak-background split applied to the Sheth & Tormen
(1999) and Tinker et al. (2008) halo mass functions matches the measured linear
bias parameter only at the level of 10%. The prediction from the excursion
set-peaks approach performs much better, which can be attributed to the
stochastic moving barrier employed in the excursion set-peaks prediction. We
also provide convenient fitting formulas for the nonlinear bias parameters
$b_2(b_1)$ and $b_3(b_1)$, which work well over a range of redshifts. |
Orbital parameters of infalling satellite haloes in the hierarchical
$Λ$CDM model: We present distributions of orbital parameters of infalling satellites of
$\Lambda$CDM haloes in the mass range $10^{12}-10^{14}$M$_\odot$, which
represent the initial conditions for the subsequent evolution of substructures
within the host halo. We use merger trees constructed in a high resolution
cosmological N-body simulation to trace satellite haloes, and identify the time
of infall. We find signficant trends in the distribution of orbital parameters
with both the host halo mass and the ratio of satellite-to-host halo masses.
For all host halo masses, satellites whose infall mass is a larger fraction of
the host halo mass have more eccentric, radially biased orbits. At fixed
satellite-to-host halo mass ratio, high mass haloes are biased towards
accreting satellites on slightly more radial orbits. To charactise the orbital
distributions fully requires fitting the correlated bivariate distribution of
two chosen orbital parameters (e.g. radial and tangential velocity or energy
and angular momentum). We provide simple fits to one choice of the bivariate
distributions, which when transformed faithfully, captures the behaviour of any
of the projected one-dimensional distributions. | Angular correlation functions of X-ray point-like sources in the full
exposure XMM-LSS field: Our aim is to study the large-scale structure of different types of AGN using
the medium-deep XMM-LSS survey. We measure the two-point angular correlation
function of ~ 5700 and 2500 X-ray point-like sources over the ~ 11 sq. deg.
XMM-LSS field in the soft (0.5-2 keV) and hard (2-10 keV) bands. For the
conversion from the angular to the spatial correlation function we used the
Limber integral equation and the luminosity-dependent density evolution model
of the AGN X-ray luminosity function. We have found significant angular
correlations with the power-law parameters gamma = 1.81 +/- 0.02, theta_0 =
1.3" +/- 0.2" for the soft, and gamma = 2.00 +/- 0.04, theta_0 = 7.3" +/- 1.0"
for the hard bands. The amplitude of the correlation function w(theta) is
higher in the hard than in the soft band for f_x < 10^-14 erg s^-1 cm^-2 and
lower above this flux limit. We confirm that the clustering strength theta_0
grows with the flux limit of the sample, a trend which is also present in the
amplitude of the spatial correlation function, but only for the soft band. In
the hard band, it remains almost constant with r_0 = 10h^-1$ Mpc, irrespective
of the flux limit. Our analysis of AGN subsamples with different hardness
ratios shows that the sources with a hard-spectrum are more clustered than
soft-spectrum ones. This result may be a hint that the two main types of AGN
populate different environments. Finally, we find that our clustering results
correspond to an X-ray selected AGN bias factor of ~ 2.5 for the soft-band
sources (at a median z = 1.1) and ~ 3.3 for the hard-band sources (at a median
z = 1), which translates into a host dark matter halo mass of ~ 10^13 h^-1 M_o
and ~ 10^13.7 h^-1 M_o for the soft and hard bands, respectively. |
Molecular Gas in Submillimetre-Faint, Star-Forming Ultraluminous
Galaxies at z>1: [abridged] We present interferometric CO observations of twelve z~2
submillimetre-faint, star-forming radio galaxies (SFRGs) which are thought to
be ultraluminous infrared galaxies (ULIRGs) possibly dominated by warmer dust
(T_dust ~> 40 K) than submillimetre galaxies (SMGs) of similar luminosities.
Four other CO-observed SFRGs are included from the literature, and all
observations are taken at the Plateau de Bure Interferometer (PdBI) in the
compact configuration. Ten of the sixteen SFRGs observed in CO (63%) are
detected at >4sigma with a mean inferred molecular gas mass of ~2*10^10 M_sun.
SFRGs trend slightly above the local ULIRG L_FIR-L'_CO relation. Since SFRGs
are about two times fainter in radio luminosity but exhibit similar CO
luminosities to SMGs, this suggests SFRGs are slightly more efficient star
formers than SMGs at the same redshifts. SFRGs also have a narrow mean CO line
width, 320+-80km/s. SFRGs bridge the gap between properties of very luminous
>5*10^12 L_sun SMGs and those of local ULIRGs and are consistent with
intermediate stage major mergers. We suspect that more moderate-luminosity
SMGs, not yet surveyed in CO, would show similar molecular gas properties to
SFRGs. The AGN fraction of SFRGs is consistent with SMGs and is estimated to be
0.3+-0.1, suggesting that SFRGs are observed near the peak phase of star
formation activity and not in a later, post-SMG enhanced AGN phase. This CO
survey of SFRGs serves as a pilot project for the much more extensive survey of
Herschel and SCUBA-2 selected sources which only partially overlap with SMGs.
Better constraints on CO properties of a diverse high-z ULIRG population are
needed from ALMA to determine the evolutionary origin of extreme starbursts,
and what role ULIRGs serve in catalyzing the formation of massive stellar
systems in the early Universe. | Star Formation Efficiency at Intermediate Redshift: Star formation is evolving very fast in the second half of the Universe, and
it is yet unclear whether this is due to evolving gas content, or evolving star
formation efficiency (SFE). We have carried out a survey of ultra-luminous
galaxies (ULIRG) between z=0.2 and 1, to check the gas fraction in this domain
of redshift which is still poorly known.
Our survey with the IRAM-30m detected 33 galaxies out of 69, and we derive a
significant evolution of both the gas fraction and SFE of ULIRGs over the whole
period, and in particular a turning point around z=0.35.
The result is sensitive to the CO-to-H2, conversion factor adopted, and both
gas fraction and SFE have comparable evolution, when we adopt the low starburst
conversion factor of \alpha =0.8 Mo/(K km/s pc^2). Adopting a higher \alpha
will increase the role of the gas fraction.
Using \alpha =0.8, the SFE and the gas fraction for z=0.2-1.0 ULIRGs are
found to be significantly higher, by a factor 3, than for local ULIRGs, and are
comparable to high redshift ones. We compare this evolution to the expected
cosmic H2 abundance and the cosmic star formation history. |
X-ray AGN in the XMM-LSS galaxy clusters: no evidence of AGN suppression: We present a study of the overdensity of X-ray selected AGN in 33 galaxy
clusters in the XMM-LSS field, up to redhift z=1.05. Previous studies have
shown that the presence of X-ray selected AGN in rich galaxy clusters is
suppressed. In the current study we investigate the occurrence of X-ray
selected AGN in low and moderate X-ray luminosity galaxy clusters. Due to the
wide contiguous XMM-LSS survey area we are able to extend the study to the
cluster outskirts. We therefore determine the projected overdensity of X-ray
point-like sources out to 6r_{500} radius. To provide robust statistical
results we also use a stacking analysis of the cluster projected overdensities.
We investigate whether the observed X-ray overdensities are to be expected by
estimating also the corresponding optical galaxy overdensities. We find a
positive X-ray projected overdensity at the first radial bin, which is however
of the same amplitude as that of optical galaxies. Therefore, no suppression of
X-ray AGN activity with respect to the field is found, implying that the
mechanisms responsible for the suppression are not so effective in lower
density environments. After a drop to roughly the background level between 2
and 3r_{500}, the X-ray overdensity exhibits a rise at larger radii,
significantly larger than the corresponding optical overdensity. Finally, using
redshift information of all optical counterparts, we derive the spatial
overdensity profile of the clusters. We find that the agreement between X-ray
and optical overdensities in the first radial bin is also suggested in the
3-dimensional analysis. However, we argue that the X-ray overdensity "bump" at
larger radial distance is probably a result of flux boosting by gravitational
lensing of background QSOs. For high redshift clusters an enhancement of X-ray
AGN activity in their outskirts is still possible. | Spherical Collapse Approach for Non-standard Cold Dark Matter Models and
Enhanced Early Galaxy Formation in JWST: We examine the impact of two alternative dark matter models that possess
distinct non-zero equations of state, one constant and the other
time-dependent, on the nonlinear regime using the spherical collapse approach.
Specifically, we compare these models to standard cold dark matter (CDM) by
analyzing their influence on the linear density threshold for nonrelativistic
component collapse and virial overdensity. Additionally, we explore the number
count of collapsed objects, or dark matter halos, which is analogous to the
number count of galaxy clusters. Finally, in light of recent discoveries by the
James Webb Space Telescope (JWST), which indicate the potential for more
efficient early galaxy formation at higher redshifts, we have been
investigating how alternative dark matter assumptions can enhance structure
formation efficiency during the early times. |
A note about the back-reaction of inhomogeneities on the expansion of
the Universe: In this short note we summarize the arguments against a significant
back-reaction of inhomogeneities on the acceleration of the Universe. We also
present a quick way to access the importance of back-reaction using the Fourier
space presentation of inhomogeneities and properties of their power spectrum. | The role of pressure anisotropy in the turbulent intracluster medium: In low-density plasma environments, such as the intracluster medium (ICM),
the Larmour frequency is much larger than the ion-ion collision frequency. In
such a case, the thermal pressure becomes anisotropic with respect to the
magnetic field orientation and the evolution of the turbulent gas is more
correctly described by a kinetic approach. A possible description of these
collisionless scenarios is given by the so-called kinetic magnetohydrodynamic
(KMHD) formalism, in which particles freely stream along the field lines, while
moving with the field lines in the perpendicular direction. In this way a
fluid-like behavior in the perpendicular plane is restored. In this work, we
study fast growing magnetic fluctuations in the smallest scales which operate
in the collisionless plasma that fills the ICM. In particular, we focus on the
impact of a particular evolution of the pressure anisotropy and its
implications for the turbulent dynamics of observables under the conditions
prevailing in the ICM. We present results from numerical simulations and
compare the results which those obtained using an MHD formalism. |
Can a supervoid explain the Cold Spot?: The discovery of a void of size $\sim200\;h^{-1}$Mpc and average density
contrast of $\sim-0.1$ aligned with the Cold Spot direction has been recently
reported. It has been argued that, although the first-order integrated
Sachs-Wolfe (ISW) effect of such a void on the CMB is small, the second-order
Rees-Sciama (RS) contribution exceeds this by an order of magnitude and can
entirely explain the observed Cold Spot temperature profile. In this paper we
examine this surprising claim using both an exact calculation with the
spherically symmetric Lema\^itre-Tolman-Bondi metric, and perturbation theory
about a background Friedmann-Robertson-Walker (FRW) metric. We show that both
approaches agree well with each other, and both show that the dominant
temperature contribution of the postulated void is an unobservable dipole
anisotropy. If this dipole is subtracted, we find that the remaining
temperature anisotropy is dominated by the linear ISW signal, which is orders
of magnitude larger than the second-order RS effect, and that the total
magnitude is too small to explain the observed Cold Spot profile. We calculate
the density and size of a void that would be required to explain the Cold Spot,
and show that the probability of existence of such a void is essentially zero
in $\Lambda$CDM. We identify the importance of \emph{a posteriori} selection
effects in the identification of the Cold Spot, but argue that even after
accounting for them, a supervoid explanation of the Cold Spot is always
disfavoured relative to a random statistical fluctuation on the last scattering
surface. | A Hubble constant measurement from superluminal motion of the jet in
GW170817: The Hubble constant ($H_0$) measures the current expansion rate of the
Universe, and plays a fundamental role in cosmology. Tremendous effort has been
dedicated over the past decades to measure $H_0$. Notably, Planck cosmic
microwave background (CMB) and the local Cepheid-supernovae distance ladder
measurements determine $H_0$ with a precision of $\sim 1\%$ and $\sim 2\%$
respectively. A $3$-$\sigma$ level of discrepancy exists between the two
measurements, for reasons that have yet to be understood. Gravitational wave
(GW) sources accompanied by electromagnetic (EM) counterparts offer a
completely independent standard siren (the GW analogue of an astronomical
standard candle) measurement of $H_0$, as demonstrated following the discovery
of the neutron star merger, GW170817. This measurement does not assume a
cosmological model and is independent of a cosmic distance ladder. The first
joint analysis of the GW signal from GW170817 and its EM localization led to a
measurement of $H_0=74^{+16}_{-8}$ km/s/Mpc (median and symmetric $68\%$
credible interval). In this analysis, the degeneracy in the GW signal between
the source distance and the weakly constrained viewing angle dominated the
$H_0$ measurement uncertainty. Recently, Mooley et al. (2018) obtained tight
constraints on the viewing angle using high angular resolution imaging of the
radio counterpart of GW170817. Here we obtain a significantly improved
measurement $H_0=68.9^{+4.7}_{-4.6}$ km/s/Mpc by using these new radio
observations, combined with the previous GW and EM data. We estimate that 15
more localized GW170817-like events (comparable signal-to-noise ratio,
favorable orientation), having radio images and light curve data, will
potentially bring resolution to the tension between the Planck and
Cepheid-supernova measurements, as compared to 50-100 GW events without such
data. |
The Compton-Thick Seyfert 2 Nucleus of NGC3281: Torus Constraints from
the 9.7$μ$m Silicate Absorption: We present mid infrared (Mid-IR) spectra of the Compton-thick Seyfert 2
galaxy NGC\,3281, obtained with the Thermal-Region Camera Spectrograph (T-ReCS)
at the Gemini South telescope. The spectra present a very deep silicate
absorption at 9.7\,$\mu$m, and [S{\sc\,iv]}\,10.5\,$\mu$m and
[Ne{\sc\,ii]}\,12.7\,$\mu$m ionic lines, but no evidence of PAH emission. We
find that the nuclear optical extinction is in the range 24 $\leq$ A$_{V}$
$\leq$ 83\,mag. A temperature T = 300\,K was found for the black-body dust
continuum component of the unresolved 65\,pc nucleus and at 130\,pc SE, while
the region at 130\,pc reveals a colder temperature (200\,K). We describe the
nuclear spectrum of NGC\,3281 using a clumpy torus model that suggests that the
nucleus of this galaxy hosts a dusty toroidal structure. According to this
model, the ratio between the inner and outer radius of the torus in NGC\,3281
is $R_0/R_d$ = 20, with {\bf 14} clouds in the equatorial radius with optical
depth of $\tau_{V}$ = 40\,mag. We would be looking in the direction of the
torus equatorial radius ($i$ = {\bf 60$^{\circ}$}), which has outer radius of
R$_{0}\,\sim$ 11\,pc. The column density is N$_{H}\approx$\,{\bf
1.2}\,$\times\,10^{24}\,cm^{-2}$ and iron K$\alpha$ equivalent width ($\approx$
0.5 - 1.2\,keV) are used to check the torus geometry. Our findings indicate
that the X-ray absorbing column density, which classifies NGC\,3281 as a
Compton-thick source, may also be responsible for the absorption at 9.7\,$\mu$m
providing strong evidence that the silicate dust responsible for this
absorption can be located in the AGN torus. | Neutrinos and dark energy after Planck and BICEP2: data consistency
tests and cosmological parameter constraints: The detection of the B-mode polarization of the cosmic microwave background
(CMB) by the BICEP2 experiment implies that the tensor-to-scalar ratio $r$
should be involved in the base standard cosmology. In this paper, we extend the
$\Lambda$CDM+$r$+neutrino/dark radiation models by replacing the cosmological
constant with the dynamical dark energy with constant $w$. Four neutrino plus
dark energy models are considered, i.e., the $w$CDM+$r+\sum m_\nu$, $w$CDM+r +
$N_{\rm eff}$, $w$CDM+r + $\sum m_\nu$ + $N_{\rm eff}$, and $w$CDM+r + $N_{\rm
eff}$ + $m_{\nu,{\rm sterile}}^{\rm eff}$ models. The current observational
data considered in this paper include the Planck temperature data, the WMAP
9-year polarization data, the baryon acoustic oscillation data, the Hubble
constant direct measurement data, the Planck Sunyaev-Zeldovich cluster counts
data, the Planck CMB lensing data, the cosmic shear data, and the BICEP2
polarization data. We test the data consistency in the four cosmological
models, and then combine the consistent data sets to perform joint constraints
on the models. We focus on the constraints on the parameters $w$, $\sum m_\nu$,
$N_{\rm eff}$, and $m_{\nu,{\rm sterile}}^{\rm eff}$. |
Gravitational waves from binary black holes in a self-interacting scalar
dark matter cloud: We investigate the imprints of accretion and dynamical friction on the
gravitational-wave signals emitted by binary black holes embedded in a scalar
dark matter cloud. As a key feature in this work, we focus on scalar fields
with a repulsive self-interaction that balances against the self-gravity of the
cloud. To a first approximation, the phase of the gravitational-wave signal
receives extra correction terms at $-3$PN, $-4$PN and $-5.5$PN orders, relative
to the prediction of vacuum general relativity, due to cloud gravity, accretion
and dynamical friction. Future observations by LISA and B-DECIGO have the
potential to detect these effects for a large range of scalar
masses~$m_\mathrm{DM}$ and self-interaction couplings~$\lambda_4$. This would
correspond to scenarios with dark matter clouds smaller than $0.1$ pc, which
would be difficult to detect by other probes. | The mid-infrared Tully-Fisher relation: Spitzer Surface Photometry: The availability of photometric imaging of several thousand galaxies with the
Spitzer Space Telescope enables a mid-infrared calibration of the correlation
between luminosity and rotation in spiral galaxies. The most important
advantage of the new calibration in the 3.6 micron band, IRAC ch.1, is
photometric consistency across the entire sky. Additional advantages are
minimal obscuration, observations of flux dominated by old stars, and
sensitivity to low surface brightness levels due to favorable backgrounds.
Through Spitzer cycle 7 roughly 3000 galaxies had been observed and images of
these are available at the Spitzer archive. In cycle 8 a program called Cosmic
Flows with Spitzer has been initiated that will increase by 1274 the available
sample of spiral galaxies with inclinations greater than 45 degrees from
face-on suitable for distance measurements. This paper describes procedures
based on the photometry package Archangel that are being employed to analyze
both the archival and the new data in a uniform way. We give results for 235
galaxies, our calibrator sample for the Tully-Fisher relation. Galaxy
magnitudes are determined with uncertainties held below 0.05 mag for normal
spiral systems. A subsequent paper will describe the calibration of the [3.6]
luminosity-rotation relation. |
Polarization Diagnostics for Cool Core Cluster Emission Lines: The nature of the interaction between low-excitation gas filaments at ~10^4
K, seen in optical line emission, and diffuse X-ray emitting coronal gas at
~10^7 K in the centers of galaxy clusters remains a puzzle. The presence of a
strong, empirical correlation between the two gas phases is indicative of a
fundamental relationship between them, though as yet of undetermined cause. The
cooler filaments, originally thought to have condensed from the hot gas, could
also arise from a merger or the disturbance of cool circumnuclear gas by
nuclear activity. Here, we have searched for intrinsic line emission
polarization in cool core galaxy clusters as a diagnostic of fundamental
transport processes. Drawing on developments in solar astrophysics, direct
energetic particle impact induced polarization holds the promise to
definitively determine the role of collisional processes such as thermal
conduction in the ISM physics of galaxy clusters, while providing insight into
other highly anisotropic excitation mechanisms such as shocks, intense
radiation fields and suprathermal particles. Under certain physical conditions,
theoretical calculations predict of order ten percent polarization. Our
observations of the filaments in four nearby cool core clusters place stringent
upper limits (<0.1%) on the presence of emission line polarization, requiring
that if thermal conduction is operative, the thermal gradients are not in the
saturated regime. This limit is consistent with theoretical models of the
thermal structure of filament interfaces. | Galaxy evolution in groups and clusters: satellite star formation
histories and quenching timescales in a hierarchical Universe: Satellite galaxies in groups and clusters are more likely to have low star
formation rates (SFR) and lie on the red-sequence than central (field)
galaxies. Using galaxy group/cluster catalogs from SDSS DR7, together with a
cosmological N-body simulation to track satellite orbits, we examine the star
formation histories and quenching timescales of satellites of M_star > 5 x 10^9
M_sun at z=0. We first explore satellite infall histories: group preprocessing
and ejected orbits are critical aspects of satellite evolution, and properly
accounting for these, satellite infall typically occurred at z~0.5, or ~5 Gyr
ago. To obtain accurate initial conditions for the SFRs of satellites at their
time of first infall, we construct an empirical parametrization for the
evolution of central galaxy SFRs and quiescent fractions. With this, we
constrain the importance and efficiency of satellite quenching as a function of
satellite and host halo mass, finding that satellite quenching is the dominant
process for building up all quiescent galaxies at M_star < 10^10 M_sun. We then
constrain satellite star formation histories, finding a 'delayed-then-rapid'
quenching scenario: satellite SFRs evolve unaffected for 2-4 Gyr after infall,
after which star formation quenches rapidly, with an e-folding time of < 0.8
Gyr. These quenching timescales are shorter for more massive satellites but do
not depend on host halo mass: the observed increase in satellite quiescent
fraction with halo mass arises simply because of satellites quenching in a
lower mass group prior to infall (group preprocessing), which is responsible
for up to half of quenched satellites in massive clusters. Because of the long
time delay before quenching starts, satellites experience significant stellar
mass growth after infall, nearly identical to central galaxies. This fact
provides key physical insight into the subhalo abundance matching method. |
AGN Driven Weather and Multiphase Gas in the Core of the NGC 5044 Galaxy
Group: A deep Chandra observation of the X-ray bright group, NGC 5044, shows that
the central region of this group has been strongly perturbed by repeated AGN
outbursts. These recent AGN outbursts have produced many small X-ray cavities,
cool filaments and cold fronts. We find a correlation between the coolest X-ray
emitting gas and the morphology of the Ha filaments. The Ha filaments are
oriented in the direction of the X-ray cavities, suggesting that the warm gas
responsible for the Halpha emission originated near the center of NGC 5044 and
was dredged up behind the buoyant, AGN-inflated X-ray cavities. A detailed
spectroscopic analysis shows that the central region of NGC 5044 contains
spatially varying amounts of multiphase gas. The regions with the most
inhomogeneous gas temperature distribution tend to correlate with the extended
235 MHz and 610 MHz radio emission detected by the GMRT. This may result from
gas entrainment within the radio emitting plasma or mixing of different
temperature gas in the regions surrounding the radio emitting plasma by AGN
induced turbulence. Accounting for the effects of multiphase gas, we find that
the abundance of heavy elements is fairly uniform within the central 100 kpc,
with abundances of 60-80% solar for all elements except oxygen, which has a
significantly sub-solar abundance. In the absence of continued AGN outbursts,
the gas in the center of NGC 5044 should attain a more homogeneous distribution
of gas temperature through the dissipation of turbulent kinetic energy and heat
conduction in approximately 10e8 yr. The presence of multiphase gas in NGC 5044
indicates that the time between recent AGN outbursts has been less than
approximately 10e8 yr. | Dark Energy Survey Year 3 results: curved-sky weak lensing mass map
reconstruction: We present reconstructed convergence maps, \textit{mass maps}, from the Dark
Energy Survey (DES) third year (Y3) weak gravitational lensing data set. The
mass maps are weighted projections of the density field (primarily dark matter)
in the foreground of the observed galaxies. We use four reconstruction methods,
each is a \textit{maximum a posteriori} estimate with a different model for the
prior probability of the map: Kaiser-Squires, null B-mode prior, Gaussian
prior, and a sparsity prior. All methods are implemented on the celestial
sphere to accommodate the large sky coverage of the DES Y3 data. We compare the
methods using realistic $\Lambda$CDM simulations with mock data that are
closely matched to the DES Y3 data. We quantify the performance of the methods
at the map level and then apply the reconstruction methods to the DES Y3 data,
performing tests for systematic error effects. The maps are compared with
optical foreground cosmic-web structures and are used to evaluate the lensing
signal from cosmic-void profiles. The recovered dark matter map covers the
largest sky fraction of any galaxy weak lensing map to date. |
Unveiling the Nature of Submillimeter Galaxy SXDF850.6: We present an 880 micron Submillimeter Array (SMA) detection of the
submillimeter galaxy SXDF850.6. SXDF850.6 is a bright source (S(850 micron) = 8
mJy) detected in the SCUBA Half Degree Extragalactic Survey (SHADES), and has
multiple possible radio counterparts in its deep radio image obtained at the
VLA. Our new SMA detection finds that the submm emission coincides with the
brightest radio emission that is found ~8" north of the coordinates determined
from SCUBA. Despite the lack of detectable counterparts in deep UV/optical
images, we find a source at the SMA position in near-infrared and longer
wavelength images. We perform SED model fits to UV-optical-IR photometry (u, B,
V, R, i', z', J, H, K, 3.6 micron, 4.5 micron, 5.8 micron, and 8.0 micron) and
to submm-radio photometry (850 micron, 880 micron, 1100 micron, and 21 cm)
independently, and we find both are well described by starburst templates at a
redshift of z ~= 2.2 (+/- 0.3). The best-fit parameters from the UV-optical-IR
SED fit are a redshift of z = 1.87 (+0.15/-0.07), a stellar mass of M_star =
2.5 +2.2/-0.3 x 10^11 M_sun, an extinction of A_V = 3.0 (+0.3/-1.0) mag, and an
age of 720 (+1880/-210) Myr. The submm-radio SED fit provides a consistent
redshift of z ~ 1.8-2.5, an IR luminosity of L_IR = (7-26) x 10^12 L_sun, and a
star formation rate of 1300-4500 M_sun/yr. These results suggest that SXDF850.6
is a mature system already having a massive amount of old stellar population
constructed before its submm bright phase and is experiencing a dusty
starburst, possibly induced by major mergers. | Upper limits on a radio halo in Abell 3667 at 1.4 GHz: The presence of a radio halo in the massive, merging cluster Abell 3667 has
recently become a focus of debate in the literature following a putative halo
detection at 2.4 GHz despite a lack of detection at a range of lower
frequencies between 120 MHz and 1.8 GHz. Here we develop a new method to place
limits on radio haloes via generation of a realistic synthetic halo based on
the brightness distribution of real haloes. The model generated extends on
previous methods in the literature producing a single elliptical halo model,
capable of being injected into mosaic as well as single observations. Applying
this model to the deepest data available 1.4 GHz data for A3667 we derive an
upper limit halo power of P$_{1.4} \leq 5.55 \times 10^{23}$ W Hz$^{-1}$. We
discuss the result in the context of current scaling relation between the X-ray
and radio properties of galaxy clusters and find that the lack of a halo in
A3667 places the cluster on the border of the so-called `off-state' region in
which clusters are expected not to host any diffuse emission. |
Hunting Dark Matter in ultra-compact structures within the Milky-Way: The local environment is ideal for searching out compact dark structures via
the microlensing and multi-frequency emissions as these objects are expected to
be faint and microlensing experiments have already hinted at their possibility.
In the case that these objects are composed of Dark Matter (DM) then there are
both few limits on their abundance but many consequences of their existence or
non-existence on both local and cosmic scales. In this work we examine the
possibility of Ultra-Compact Mini-Halos (UCMHs) formed in the early universe.
These objects can persist to the present epoch due to their large central
density inuring them to the worst effects of later tidal stripping. As such,
these objects could constitute probes of many details of early universe
physics, such as primordial phase-transitions, inflation, small scale
exploration of the primordial density perturbation field and non-Gaussianity of
these density perturbations. The fact that they are also highly dark
matter-dominated objects means that they are attractive objects of study in the
continuing hunt for the nature of Dark Matter (DM) through indirect detection.
Another reason to study such objects in the local environment is found in the
conjecture that encounters with UCMHs could induce catastrophic events on
planets within our solar system, e.g. mass-extinction events on Earth. We will
outline a strategy for multi-frequency UCMH searches within the region of the
Milky-Way in which Gaia can accurately reconstruct microlens masses. This
methodology ensures that any candidate UCMH DM emission should correlate to
some unidentified microlensing object with determinable mass and demonstrate
that large-scale volcanic extinctions on Earth due to UCMHs are unlikely but
that it is possible for loss of the Martian geodynamo to be driven encounters
with such compact objects. | Impact of calibration errors on CMB component separation using FastICA
and ILC: The separation of emissions from different astrophysical processes is an
important step towards the understanding of observational data. This topic of
component separation is of particular importance in the observation of the
relic Cosmic Microwave Background Radiation, as performed by the WMAP satellite
and the more recent Planck mission, launched May 14th, 2009 from Kourou and
currently taking data. When performing any sort of component separation, some
assumptions about the components must be used. One assumption that many
techniques typically use is knowledge of the frequency scaling of one or more
components. This assumption may be broken in the presence of calibration
errors. Here we compare, in the context of imperfect calibration, the recovery
of a clean map of emission of the Cosmic Microwave Background from
observational data with two methods: FastICA (which makes no assumption of the
frequency scaling of the components), and an `Internal Linear Combination'
(ILC), which explicitly extracts a component with a given frequency scaling. We
find that even in the presence of small calibration errors with a Planck-style
mission, the ILC method can lead to inaccurate CMB reconstruction in the high
signal-to-noise regime, because of partial cancellation of the CMB emission in
the recovered map. While there is no indication that the failure of the ILC
will translate to other foreground cleaning or component separation techniques,
we propose that all methods which assume knowledge of the frequency scaling of
one or more components be careful to estimate the effects of calibration
errors. |
MASSIV: Mass Assemby Survey with SINFONI in VVDS. I. Survey description
and global properties of the 0.9 < z < 1.8 galaxy sample: Understanding how galaxies evolve and assemble their mass across cosmic time
is still a fundamental unsolved issue. To get insight into the various
processes of galaxy mass assembly, the Mass Assembly Survey with SINFONI in
VVDS (MASSIV) aims at probing the kinematical and chemical properties of a
significant and representative sample of high-redshift (0.9 < z < 1.8)
star-forming galaxies. This paper presents the selection function, the
observing strategy and the global properties of the MASSIV sample. This sample
contains 84 star-forming galaxies, selected from the VIMOS VLT Deep Survey
(VVDS) and observed with the SINFONI IFU at the VLT. We present the redshift
distribution, and derive the stellar masses and SED-based star formation rates
(SFR). Integrated metallicities and the presence of type-2 AGNs are
investigated using composite 1D spectra built from VIMOS and SINFONI
observations. The MASSIV selection function, based on star formation criteria
([OII] emission-line strength up to z~1.5 and colors/UV absorption lines at
higher redshifts), provides a good representation of "normal" star-forming
galaxies with SED-based SFRs between 5 and 400 Msun/yr in the stellar mass
regime 10^9 - 10^11 Msun. Analysis of typical emission-line ratios performed on
composite spectra reveals that the contamination by type-2 AGNs is very low and
that the integrated metallicity of the galaxies follows the well-known
mass-metallicity relation. The MASSIV sample has been built upon a simple
selection function, fully representative of the star-forming galaxy population
at 0.9 < z < 1.8 for SFR > 5 Msun/yr. Together with the size of the sample, the
spatially-resolved SINFONI data therefore enables us to discuss global, volume
averaged, galaxy kinematic and chemical properties all accross the mass and SFR
range of the survey to derive robust conclusions on galaxy mass assembly over
cosmological timescales. | Dark Radiation candidates after Planck: Recent Cosmic Microwave Background (CMB) results from the Planck satellite,
combined with previous CMB data and Hubble constant measurements from the
Hubble Space Telescope, provide a constraint on the effective number of
relativistic degrees of freedom of Neff=3.62^{+0.50}_{-0.48} at 95% CL. These
new measurements provide a unique opportunity to place limits on models
containing relativistic species at the decoupling epoch. Here we review the
bounds or the allowed parameter regions in sterile neutrino models, hadronic
axion models as well as on extended dark sectors with additional light species
based on the latest Planck CMB observations. |
Cosmological constraints on generalized Chaplygin gas model: Markov
Chain Monte Carlo approach: We use the Markov Chain Monte Carlo method to investigate a global
constraints on the generalized Chaplygin gas (GCG) model as the unification of
dark matter and dark energy from the latest observational data: the
Constitution dataset of type supernovae Ia (SNIa), the observational Hubble
data (OHD), the cluster X-ray gas mass fraction, the baryon acoustic
oscillation (BAO), and the cosmic microwave background (CMB) data. In a
non-flat universe, the constraint results for GCG model are,
$\Omega_{b}h^{2}=0.0235^{+0.0021}_{-0.0018}$ ($1\sigma$) $^{+0.0028}_{-0.0022}$
$(2\sigma)$, $\Omega_{k}=0.0035^{+0.0172}_{-0.0182}$ ($1\sigma$)
$^{+0.0226}_{-0.0204}$ $(2\sigma)$, $A_{s}=0.753^{+0.037}_{-0.035}$ ($1\sigma$)
$^{+0.045}_{-0.044}$ $(2\sigma)$, $\alpha=0.043^{+0.102}_{-0.106}$ ($1\sigma$)
$^{+0.134}_{-0.117}$ $(2\sigma)$, and $H_{0}=70.00^{+3.25}_{-2.92}$ ($1\sigma$)
$^{+3.77}_{-3.67}$ $(2\sigma)$, which is more stringent than the previous
results for constraint on GCG model parameters. Furthermore, according to the
information criterion, it seems that the current observations much support
$\Lambda$CDM model relative to the GCG model. | Analysis of the Spectral Energy Distributions of Fermi bright blazars: Blazars are a small fraction of all extragalactic sources but, unlike other
objects, they are strong emitters across the entire electromagnetic spectrum.
In this study we have conducted a detailed investigation of the broad-band
spectral properties of the gamma-ray selected blazars of the Fermi-LAT Bright
AGN Sample (LBAS). By combining the accurately estimated Fermi gamma-ray
spectra with Swift, radio, NIR-Optical and hard-X/gamma-ray data, collected
within three months of the LBAS data taking period, we were able to assemble
high-quality and quasi-simultaneous Spectral Energy Distributions (SED) for 48
LBAS blazars. |
Disk galaxies at z=2 in OWLS: We use the OWLS (OverWhelmingly Large Simulations) set of cosmological
Nbody/gasdynamical simulations to study the properties of simulated galaxies at
z=2. We focus on the effect of supernova feedback from evolving stars on the
baryonic mass and angular momentum content of galaxies that assemble at the
center of 1e11-3e12 h^{-1}M_\odot halos. Our main finding is that the mass and
angular momentum of such galaxies are strongly coupled, in a way that is
approximately independent of feedback: varying the feedback implementation
leads, in a given halo, to large variations in galaxy mass but leaves the
galaxy mass-angular momentum correlation largely unaltered. In particular, the
ratio between the angular momentum of a galaxy and that of its surrounding halo
(j_d=J_gal/J_vir) correlates closely with the galaxy mass (expressed in units
of the virial mass of the halo; m_d=M_gal/M_vir). This correlation differs
substantially from the m_d=j_d assumption commonly adopted in semianalytic
models of galaxy formation. We use these results to infer the sizes of disk
galaxies at z=2 expected in the LCDM scenario and to interpret recent
observations of extended disks at z~2 by the SINS collaboration | Gas fraction and star formation efficiency at z < 1.0: After new observations of 39 galaxies at z = 0.6-1.0 obtained at the IRAM 30m
telescope, we present our full CO line survey covering the redshift range 0.2 <
z < 1. Our aim is to determine the driving factors accounting for the steep
decline in the star formation rate during this epoch. We study both the gas
fraction, defined as Mgas/(Mgas+Mstar), and the star formation efficiency (SFE)
defined by the ratio between far-infrared luminosity and molecular gas mass
(LFIR/M(H2), i.e. a measure for the inverse of the gas depletion time. The
sources are selected to be ultra-luminous infrared galaxies (ULIRGs), with LFIR
greater than 10^12 Lo and experiencing starbursts. When we adopt a standard
ULIRG CO-to-H2 conversion factor, their molecular gas depletion time is less
than 100 Myr. Our full survey has now filled the gap of CO observations in the
0.2<z<1 range covering almost half of cosmic history. The detection rate in the
0.6 < z < 1 interval is 38% (15 galaxies out of 39), compared to 60% for the
0.2<z<0.6 interval. The average CO luminosity is L'CO = 1.8 10^10 K km/s pc^2,
corresponding to an average H2 mass of 1.45 10^10 Mo. From observation of 7
galaxies in both CO(2-1) and CO(4-3), a high gas excitation has been derived;
together with the dust mass estimation, this supports the choice of our low
ULIRG conversion factor between CO luminosity and H2, for our sample sources.
We find that both the gas fraction and the SFE significantly increase with
redshift, by factors of 3 +-1 from z=0 to 1, and therefore both quantities play
an important role and complement each other in cosmic star formation evolution. |
Searching for Non-axisymmetries in NGC 6503: A Weak End-on Bar: The isolation, simple apparent structure, and low luminosity of the nearby
spiral galaxy NGC 6503 make it an ideal candidate for an in-depth kinematic and
photometric study. We introduce a new publicly available code, DiskFit, that
implements procedures for fitting non-axisymmetries in either kinematic or
photometric data. We use DiskFit to analyze new Halpha and CO velocity field
data as well as HI kinematics from Greisen et al. to search for non-circular
motions in the disc of NGC 6503. We find NGC 6503 to have remarkably regular
gas kinematics that are well-described by rotation only. We also use DiskFit
and a new Ks-band image of NGC 6503 to constrain photometric models of the
disc, bar and bulge. We find the galaxy to be photometrically dominated by the
disc. We find NGC 6503 to contain a faint bar and an exponential bulge which
together contribute only ~5% of the total galaxy light. The combination of our
kinematic and photometric DiskFit models suggest that NGC 6503 contains a weak,
end-on bar that may have produced its Type II surface brightness profile but is
unlikely to be responsible for its strong sigma-drop. | Distinguishing standard and modified gravity cosmologies with machine
learning: We present a convolutional neural network to classify distinct cosmological
scenarios based on the statistically similar weak-lensing maps they generate.
Modified gravity (MG) models that include massive neutrinos can mimic the
standard concordance model ($\Lambda$CDM) in terms of Gaussian weak-lensing
observables. An inability to distinguish viable models that are based on
different physics potentially limits a deeper understanding of the fundamental
nature of cosmic acceleration. For a fixed redshift of sources, we demonstrate
that a machine learning network trained on simulated convergence maps can
discriminate between such models better than conventional higher-order
statistics. Results improve further when multiple source redshifts are
combined. To accelerate training, we implement a novel data compression
strategy that incorporates our prior knowledge of the morphology of typical
convergence map features. Our method fully distinguishes $\Lambda$CDM from its
most similar MG model on noise-free data, and it correctly identifies among the
MG models with at least 80% accuracy when using the full redshift information.
Adding noise lowers the correct classification rate of all models, but the
neural network still significantly outperforms the peak statistics used in a
previous analysis. |
Gemini K-band NIRI Adaptive Optics Observations of Massive Galaxies at 1
< z < 2: We present deep K-band adaptive-optics observations of eight very massive (M*
~ 4 x 10^11 Msun) galaxies at 1 < z < 2 utilizing the Gemini NIRI/Altair Laser
Guide System. These systems are selected from the Palomar Observatory
Wide-Field Infrared (POWIR) survey, and are amongst the most massive field
galaxies at these epochs. The depth and high spatial resolution of our images
allow us to explore for the first time the stellar mass surface density
distribution of massive distant galaxies from 1 to 15 kpc on an individual
galaxy basis, rather than on stacked images. We confirm that some of these
massive objects are extremely compact with measured effective radii between
0."1 - 0."2, giving sizes which are < 2 kpc, a factor of ~ 7 smaller in
effective radii than similar mass galaxies today. Examining stellar mass
surface densities as a function of fixed physical aperture, we find an
over-density of material within the inner profiles, and an under-density in the
outer profile, within these high-z galaxies compared with similar mass galaxies
in the local universe. Consequently, massive galaxies should evolve in a way to
decrease the stellar mass density in their inner region, and at the same time
creating more extensive outer light envelopes. We furthermore show that ~ 38%
+- 20% of our sample contains evidence for a disturbed outer stellar matter
distribution suggesting that these galaxies are undergoing a recent dynamical
episode, such as a merger or accretion event. We calculate that massive
galaxies at z < 2 will undergo on the order of five of these events, a much
higher rate than observed for major mergers, suggesting that these galaxies are
growing in size and stellar mass in part through minor mergers during this
epoch. | On the perturbation theory in spatially closed background: In this article,we investigate some features of the perturbation theory in
spatially closed universe. We will show that the perturbative field equations
in a spatially closed universe always have two independent adiabatic solutions
provided that the wavelengths of perturbation modes are very longer than the
Hubble horizon. It will be revealed that these adiabatic solutions do not
depend on the curvature directly. We also propound a new interpretation for the
curvature perturbation in terms of the unperturbed geometry. |
Large-scale imprint of relativistic effects in the cosmic magnification: Apart from the known weak gravitational lensing effect, the cosmic
magnification acquires relativistic corrections owing to Doppler, integrated
Sachs-Wolfe, time-delay and other (local) gravitational potential effects,
respectively. These corrections grow on very large scales and high redshifts z,
which will be the reach of forthcoming surveys. In this work, these
relativistic corrections are investigated in the magnification angular power
spectrum, using both (standard) noninteracting dark energy (DE), and
interacting DE (IDE). It is found that for noninteracting DE, the relativistic
corrections can boost the magnification large-scale power by ~ 40% at z = 3,
and increases at lower z. It is also found that the IDE effect is sensitive to
the relativistic corrections in the magnification power spectrum, particularly
at low z---which will be crucial for constraints on IDE. Moreover, the results
show that if relativistic corrections are not taken into account, this may lead
to an incorrect estimate of the large-scale imprint of IDE in the cosmic
magnification; including the relativistic corrections can enhance the true
potential of the cosmic magnification as a cosmological probe. | Spectator dark matter in non-standard cosmologies: It has been shown that the observed dark matter (DM) abundance can be
produced by amplification of quantum fluctuations of an energetically
subdominant scalar field during inflation. In this paper, we study the
robustness of this "spectator dark matter" scenario to changes in the expansion
rate of the early Universe. Compared to the standard radiation-dominated (RD)
scenario, two aspects will change: the DM energy density evolves differently as
a function of time, and also the DM isocurvature perturbation spectrum will be
different from the result in the RD case. These can impose sizeable changes to
the values of model parameters which allow the field to constitute all DM while
simultaneously satisfying all observational constraints. We study both free and
self-interacting DM in scenarios with non-standard expansion and quantify the
changes to the cases with a standard cosmological history. We also discuss
testability of the scenario through primordial DM isocurvature and
non-Gaussianity. |
Nature of X-shaped sources: The nature of X-shaped sources is a matter of considerable debate: it has
even been proposed that they provide evidence for black hole mergers$ / $spin
reorientation, and therefore constrain the rate of strong gravitational wave
events (Merritt & Ekers 2002). Based on morphological and spectral
characteristics of these sources, currently a strong contender to explain the
nature of these sources is the `alternative' model of Lal & Rao (2007), in
which these sources consist of two pairs of jets, which are associated with two
unresolved AGNs. Detailed morphological and spectral results on
milliarcsecond-scales (mas) provide a crucial test of this model, and hence
these sources are excellent candidates to study on mas; {\it i.e.}, to detect
he presence/absence of double nuclei/AGNs, signs of helical/disrupted jets,
thereby, to investigate spatially resolved/unresolved binary AGN systems and
providing clues to understanding the physics of merging of AGNs on mas. We
conducted a systematic study of a large sample of known X-shaped, comparison FR
II radio galaxies, and newly discovered X-shaped candidate sources using Giant
Metrewave Radio Telescope and Very Large Array at several radio frequencies. In
our new observations of `comparison' FR II radio galaxies we find that almost
all of our targets show standard spectral steepening as a function of distance
from the hotspot. However, one source, 3C 321, has a low-surface-brightness
extension that shows a flatter spectral index than the high-surface-brightness
hotspots$ / $lobes, as found in `known' X-shaped sources. | Relativistic Resonant Relations between Massive Black Hole Binary and
Extreme Mass Ratio Inspiral: One component of a massive black hole binary (MBHB) might capture a small
third body, and then a hierarchical, inclined triple system would be formed.
With the post-Newtonian approximation including radiation reaction, we analyzed
the evolution of the triple initially with small eccentricities. We found that
an essentially new resonant relation could arise in the triple system. Here
relativistic effects are crucial. Relativistic resonances, including the new
one, stably work even for an outer MBHB of comparable masses, and significantly
change the orbit of the inner small body. |
Evidence for Secular Evolution of Disc Structural Parameters in Massive
Barred Galaxies: We address the effects of bar-driven secular evolution in discs by comparing
their properties in a sample of nearly 700 unbarred and barred (42 +- 3 per
cent of the population) massive disc galaxies (M* > 10^10 Msun). We make use of
accurate structural parameters derived from i-band bulge/disc/bar
decompositions to show that, as a population, barred discs tend to have fainter
central surface brightness (Delta mu_0 ~ 0.25 mag), and disc scale lengths that
are ~15 per cent larger than those of unbarred galaxies of the same stellar
mass. The corresponding distributions of mu_0 and h are statistically
inconsistent at the 5.2 sigma and 3.8 sigma levels, respectively. Bars rarely
occur in high-surface brightness discs, with less than 5 per cent of the barred
population having mu_0 < 19.5 mag arcsec^-2 -- compared to 20 per cent for
unbarred galaxies. They tend to reside in moderately blue discs, with a bar
fraction that peaks at (g-i)_disc ~ 0.95 mag and mildly declines for both bluer
and redder colours. These results demonstrate noticeable structural differences
between the discs of barred and unbarred galaxies, which we argue are the
result of bar-driven evolution -- in qualitative agreement with longstanding
theoretical expectations. | Non-minimally Coupled Pseudoscalar Inflaton: We consider a scenario in which the inflaton $\phi$ is a pseudoscalar field
non-minimally coupled to gravity through a term of the form ${\cal X} R
\phi^2$. The pseudoscalar is also coupled to a $U(1)$ gauge field (or an
ensemble of ${\cal N}$ gauge fields) through an axial coupling of the form
$\phi F \tilde{F}$. After M. M. Anber and L. Sorbo, Phys. Rev. D 81, 043534
(2010), Ref. [1], it is well known that this axial coupling leads to a
production of gauge particles which acts as a friction term in the dynamics of
the inflaton, producing a slow-roll regime even in presence of a steep
potential. A remarkable result in this scenario, is that the spectrum of the
chiral gravitational waves sourced by the scalar-gauge field interplay can be
enhanced due to the non-minimal coupling with gravity, leading to measurable
signatures, while maintaining agreement with current observational constraints
on $n_s$ and $r$. The inclusion of non-minimal coupling could be helpful to
alleviate tensions with non-Gaussianity bounds in models including axial
couplings. |
Searching for variations in the fine-structure constant and the
proton-to-electron mass ratio using quasar absorption lines: (abridged) Quasar absorption lines provide a precise test of the assumed
constancy of the fundamental constants of physics. We have investigated
potential changes in the fine-structure constant, alpha, and the
proton-to-electron mass ratio, mu.
The many-multiplet method allows one to use optical fine-structure
transitions to constrain (Delta alpha)/alpha at better than the 10^(-5) level.
We present a new analysis of 154 quasar absorbers with 0.2 < z <3.7 in VLT/UVES
spectra. From these absorbers we find 2.2 sigma evidence for angular variations
in alpha under a dipole+monopole model. Combined with previous Keck/HIRES
observations, we find 4.1 sigma evidence for angular (and therefore spatial)
variations in alpha, with maximal increase of alpha occurring in the direction
RA=(17.3 +/- 1.0) hr, dec=(-61 +/- 10) deg. Under a model where the observed
effect is proportional to the lookback-time distance the significance increases
to 4.2 sigma. Dipole models fitted to the VLT and Keck samples and models
fitted to z<1.6 and z>1.6 sub-samples independently yield consistent estimates
of the dipole direction, which suggests that the effect is not caused by
telescope systematics. We consider a number of systematic effects and show that
they are unable to explain the observed dipole effect.
We have used spectra of the quasars Q0405-443, Q0347-383 and Q0528-250 from
VLT/UVES to investigate the absorbers at z=2.595, 3.025 and 2.811 in these
spectra respectively. We find that (Delta mu)/mu=(10.1 +/- 6.6) x 10^(-6), (8.2
+/- 7.5) x 10^(-6) and (-1.4 +/- 3.9) x 10^(-6) in these absorbers
respectively. A second spectrum of Q0528-250 provides an additional constraint
of (Delta mu)/mu=(0.2 +/- 3.2_stat +/- 1.9_sys) x 10^(-6). The weighted mean of
these values yields (Delta mu)/mu=(1.7 +/- 2.4) x 10^(-6), the most precise
constraint on evolution in mu at z>1. | The Carnegie Supernova Project: Light Curve Fitting with SNooPy: In providing an independent measure of the expansion history of the Universe,
the Carnegie Supernova Project (CSP) has observed 71 high-z Type Ia supernovae
(SNe Ia) in the near-infrared bands Y and J. These can be used to construct
rest-frame i-band light curves which, when compared to a low-z sample, yield
distance moduli that are less sensitive to extinction and/or decline-rate
corrections than in the optical. However, working with NIR observed and i-band
rest frame photometry presents unique challenges and has necessitated the
development of a new set of observational tools in order to reduce and analyze
both the low-z and high-z CSP sample. We present in this paper the methods used
to generate uBVgriYJH light-curve templates based on a sample of 24
high-quality low-z CSP SNe. We also present two methods for determining the
distances to the hosts of SN Ia events. A larger sample of 30 low-z SNe Ia in
the Hubble Flow are used to calibrate these methods. We then apply the method
and derive distances to seven galaxies that are so nearby that their motions
are not dominated by the Hubble flow. |
Optimal limits on f_{NL}^{local} from WMAP 5-year data: We have applied the optimal estimator for f_{NL}^{local} to the 5 year WMAP
data. Marginalizing over the amplitude of foreground templates we get -4 <
f_{NL}^{local} < 80 at 95% CL. Error bars of previous (sub-optimal) analyses
are roughly 40% larger than these. The probability that a Gaussian simulation,
analyzed using our estimator, gives a result larger in magnitude than the one
we find is 7%. Our pipeline gives consistent results when applied to the three
and five year WMAP data releases and agrees well with the results from our own
sub-optimal pipeline. We find no evidence of any residual foreground
contamination. | Constraint on a cosmological variation in the proton-to-electron mass
ratio from electronic CO absorption: Carbon monoxide (CO) absorption in the sub-damped Lyman-$\alpha$ absorber at
redshift $z_{abs} \simeq 2.69$, toward the background quasar SDSS
J123714.60+064759.5 (J1237+0647), was investigated for the first time in order
to search for a possible variation of the proton-to-electron mass ratio, $\mu$,
over a cosmological time-scale. The observations were performed with the Very
Large Telescope/Ultraviolet and Visual Echelle Spectrograph with a
signal-to-noise ratio of 40 per 2.5 kms$^{-1}$ per pixel at $\sim 5000$ \AA.
Thirteen CO vibrational bands in this absorber are detected: the A$^{1}\Pi$ -
X$^{1}\Sigma^{+}$ ($\nu'$,0) for $\nu' = 0 - 8$, B$^{1}\Sigma^{+}$ -
X$^{1}\Sigma^{+}$ (0,0), C$^{1}\Sigma^{+}$ - X$^{1}\Sigma^{+}$ (0,0), and
E$^{1}\Pi$ - X$^{1}\Sigma^{+}$ (0,0) singlet-singlet bands and the
d$^{3}\Delta$ - X$^{1}\Sigma^{+}$ (5,0) singlet-triplet band. An updated
database including the most precise molecular inputs needed for a
$\mu$-variation analysis is presented for rotational levels $J = 0 - 5$,
consisting of transition wavelengths, oscillator strengths, natural lifetime
damping parameters, and sensitivity coefficients to a variation of the
proton-to-electron mass ratio. A comprehensive fitting method was used to fit
all the CO bands at once and an independent constraint of $\Delta\mu/\mu = (0.7
\pm 1.6_{stat} \pm 0.5_{syst}) \times 10^{-5}$ was derived from CO only. A
combined analysis using both molecular hydrogen and CO in the same J1237+0647
absorber returned a final constraint on the relative variation of
$\Delta\mu/\mu = (-5.6 \pm 5.6_{stat} \pm 3.1_{syst}) \times 10^{-6}$, which is
consistent with no variation over a look-back time of $\sim 11.4$ Gyrs. |
Gravitational Waves Induced by non-Gaussian Scalar Perturbations: We study gravitational waves (GWs) induced by non-Gaussian curvature
perturbations. We calculate the density parameter per logarithmic frequency
interval, $\Omega_\text{GW}(k)$, given that the power spectrum of the curvature
perturbation $\mathcal{P}_\mathcal{R}(k)$ has a narrow peak at some small scale
$k_*$, with a local-type non-Gaussianity, and constrain the nonlinear parameter
$f_\text{NL}$ with the future LISA sensitivity curve as well as with
constraints from the abundance of the primordial black holes (PBHs). We find
that the non-Gaussian contribution to $\Omega_\text{GW}$ increases as $k^3$,
peaks at $k/k_*=4/\sqrt{3}$, and has a sharp cutoff at $k=4k_*$. The
non-Gaussian part can exceed the Gaussian part if
$\mathcal{P}_\mathcal{R}(k)f_\text{NL}^2\gtrsim1$. If both a slope
$\Omega_\text{GW}(k)\propto k^\beta$ with $\beta\sim3$ and the multiple-peak
structure around a cutoff are observed, it can be recognized as a smoking gun
of the primordial non-Gaussianity. We also find that if PBHs with masses of
$10^{20}\text{g}$ to $10^{22}\text{g}$ are identified as cold dark matter of
the Universe, the corresponding GWs must be detectable by LISA-like detectors,
irrespective of the value of $\mathcal{P}_\mathcal{R}$ or $f_\text{NL}$. | Calculation of primordial abundances of light nuclei including a heavy
sterile neutrino: We include the coupling of a heavy sterile neutrino with active neutrinos in
the calculation of primordial abundances of light-nuclei. We calculate neutrino
distribution functions and primordial abundances, as functions depending on a
renormalization of the sterile neutrino distribution function $(a)$, the
sterile neutrino mass $(m_s)$ and the mixing angle $(\phi)$. Using the
observable data, we set constrains on these parameters, which have the values
$a < 0.60$, $\sin^2 \phi=0.15$ and $m_s \approx 4$ keV, for a fixed value of
the baryon to photon ratio. When the baryon to photon ratio is allowed to vary,
its extracted value is in agreement with the values constrained by Planck
observations and by the Wilkinson Microwave Anisotropy Probe (WMAP). It is
found that the anomaly in the abundance of $^7$Li persists, in spite of the
inclusion of a heavy sterile neutrino. |
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