text
stringlengths 89
2.49k
| category
stringclasses 19
values |
---|---|
Weighing neutrinos in $f(R)$ gravity in light of BICEP2: We constrain the neutrino mass in $f(R)$ gravity using the latest
observations from the Planck, BAO and BICEP2 data. We find that the measurement
on the B-modes can break the degeneracy between the massive neutrinos and the
$f(R)$ gravity. We find a non-zero value of the Compton wavelengths $B_{0}$ at
a $68\%$ confidence level for the $f(R)$ model in the presence of massive
neutrinos when the BICEP2 data is used. Furthermore, the tension on the
tensor-to-scalar ratios between the measured values from Plank and BICEP2 is
significantly reconciled in our model. | astro-ph_CO |
Complementary Cosmological Simulations: Cosmic variance limits the accuracy of cosmological N-body simulations,
introducing bias in statistics such as the power spectrum, halo mass function,
or the cosmic shear. We provide new methods to measure and reduce the effect of
cosmic variance in existing and new simulations. We ran pairs of simulations
using phase-shifted initial conditions with matching amplitudes. We set the
initial amplitudes of the Fourier modes to ensure that the average power
spectrum of the pair is equal to the cosmic mean power spectrum from linear
theory. The average power spectrum of a pair of such simulations remains
consistent with the estimated nonlinear spectra of the state-of-the-art methods
even at late times. We also show that the effect of cosmic variance on any
analysis involving a cosmological simulation can be estimated using the
complementary pair of the original simulation. To demonstrate the effectiveness
of our novel technique, we simulated a complementary pair of the original
Millennium run and quantified the degree to which cosmic variance affected its
the power spectrum. The average power spectrum of the original and
complementary Millennium simulation was able to directly resolve the baryon
acoustic oscillation features. | astro-ph_CO |
The Type Ia Supernova Color-Magnitude Relation and Host Galaxy Dust: A
Simple Hierarchical Bayesian Model: Conventional Type Ia supernova (SN Ia) cosmology analyses currently use a
simplistic linear regression of magnitude versus color and light curve shape,
which does not model intrinsic SN Ia variations and host galaxy dust as
physically distinct effects, resulting in low color-magnitude slopes. We
construct a probabilistic generative model for the dusty distribution of
extinguished absolute magnitudes and apparent colors as the convolution of a
intrinsic SN Ia color-magnitude distribution and a host galaxy dust
reddening-extinction distribution. If the intrinsic color-magnitude ($M_B$ vs.
$B-V$) slope $\beta_{int}$ differs from the host galaxy dust law $R_B$, this
convolution results in a specific curve of mean extinguished absolute magnitude
vs. apparent color. The derivative of this curve smoothly transitions from
$\beta_{int}$ in the blue tail to $R_B$ in the red tail of the apparent color
distribution. The conventional linear fit approximates this effective curve
near the average apparent color, resulting in an apparent slope $\beta_{app}$
between $\beta_{int}$ and $R_B$. We incorporate these effects into a
hierarchical Bayesian statistical model for SN Ia light curve measurements, and
analyze a dataset of SALT2 optical light curve fits of 248 nearby SN Ia at z <
0.10. The conventional linear fit obtains $\beta_{app} \approx 3$. Our model
finds a $\beta_{int} = 2.3 \pm 0.3$ and a distinct dust law of $R_B = 3.8 \pm
0.3$, consistent with the average for Milky Way dust, while correcting a
systematic distance bias of $\sim 0.10$ mag in the tails of the apparent color
distribution. Finally, we extend our model to examine the SN Ia luminosity-host
mass dependence in terms of intrinsic and dust components. | astro-ph_CO |
Radio selection of the most distant galaxy clusters: We show that the most distant X-ray detected cluster known to date, ClJ1001
at z=2.506, hosts a strong overdensity of radio sources. Six of them are
individually detected (within 10") in deep 0.75" resolution VLA 3GHz imaging,
with S(3GHz)>8uJy. Of the six, AGN likely affects the radio emission in two
galaxies while star formation is the dominant source powering the remaining
four. We searched for cluster candidates over the full COSMOS 2-square degree
field using radio-detected 3GHz sources and looking for peaks in Sigma5 density
maps. ClJ1001 is the strongest overdensity by far with >10sigma, with a simple
z_phot>1.5 preselection. A cruder photometric rejection of z<1 radio
foregrounds leaves ClJ1001 as the second strongest overdensity, while even
using all radio sources ClJ1001 remains among the four strongest projected
overdensities. We conclude that there are great prospects for future, deep and
wide-area radio surveys to discover large samples of the first generation of
forming galaxy clusters. In these remarkable structures widespread star
formation and AGN activity of massive galaxy cluster members, residing within
the inner cluster core, will ultimately lead to radio continuum as one of the
most effective means for their identification, with detection rates expected in
the ballpark of 0.1-1 per square degree at z>2.5. Samples of hundreds such
high-redshift clusters could potentially constrain cosmological parameters and
test cluster and galaxy formation models. | astro-ph_CO |
Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies: We review the observed demographics and inferred evolution of supermassive
black holes (BHs) found by dynamical modeling of spatially resolved kinematics.
Most influential was the discovery of a tight correlation between BH mass and
the velocity dispersion of the host-galaxy bulge. It and other correlations led
to the belief that BHs and bulges coevolve by regulating each other's growth.
New results are now replacing this simple story with a richer and more
plausible picture in which BHs correlate differently with different galaxy
components. BHs are found in pure-disk galaxies, so classical
(elliptical-galaxy-like) bulges are not necessary to grow BHs. But BHs do not
correlate with galaxy disks. And any correlations with disk-grown pseudobulges
or halo dark matter are so weak as to imply no close coevolution. We suggest
that there are four regimes of BH feedback. 1- Local, stochastic feeding of
small BHs in mainly bulgeless galaxies involves too little energy to result in
coevolution. 2- Global feeding in major, wet galaxy mergers grows giant BHs in
short, quasar-like "AGN" events whose feedback does affect galaxies. This makes
classical bulges and coreless-rotating ellipticals. 3- At the highest BH
masses, maintenance-mode feedback into X-ray gas has the negative effect of
helping to keep baryons locked up in hot gas. This happens in giant,
core-nonrotating ellipticals. They inherit coevolution magic from smaller
progenitors. 4- Independent of any feedback physics, the averaging that results
from successive mergers helps to engineer tight BH correlations. | astro-ph_CO |
Relationship between the CMB, SZ Cluster Counts, and Local Hubble
Parameter Measurements in a Simple Void Model: The discrepancy between the amplitudes of matter fluctuations inferred from
Sunyaev-Zel'dovich (SZ) cluster number counts, the primary temperature, and the
polarization anisotropies of the cosmic microwave background (CMB) measured by
the Planck satellite can be reconciled if the local universe is embedded in an
under-dense region as shown by Lee, 2014. Here using a simple void model
assuming the open Friedmann-Robertson-Walker geometry and a Markov Chain Monte
Carlo technique, we investigate how deep the local under-dense region needs to
be to resolve this discrepancy. Such local void, if exists, predicts the local
Hubble parameter value that is different from the global Hubble constant. We
derive the posterior distribution of the local Hubble parameter from a joint
fitting of the Planck CMB data and SZ cluster number counts assuming the simple
void model. We show that the predicted local Hubble parameter value of $H_{\rm
loc}=70.1\pm0.34~{\rm km\,s^{-1}Mpc^{-1}}$ is in better agreement with direct
local Hubble parameter measurements, indicating that the local void model may
provide a consistent solution to the cluster number counts and Hubble parameter
discrepancies. | astro-ph_CO |
Color and stellar population gradients in galaxies. Correlation with
mass: We analyze the color gradients (CGs) of ~50000 nearby SDSS galaxies. From
synthetic spectral models based on a simplified star formation recipe, we
derive the mean spectral properties, and explain the observed radial trends of
the color as gradients of the stellar population age and metallicity (Z). The
most massive ETGs (M_* > 10^{11} Msun) have shallow CGs in correspondence of
shallow (negative) Z gradients. In the stellar mass range 10^(10.3-10.5) < M_*
< 10^(11) Msun, the Z gradients reach their minimum of ~ -0.5 dex^{-1}. At M_*
~ 10^{10.3-10.5} Msun, color and Z gradient slopes suddenly change. They turn
out to anti-correlate with the mass, becoming highly positive at the very low
masses. We have also found that age gradients anti-correlate with Z gradients,
as predicted by hierarchical cosmological simulations for ETGs. On the other
side, LTGs have gradients which systematically decrease with mass (and are
always more negative than in ETGs), consistently with the expectation from gas
infall and SN feedback scenarios. Z is found to be the main driver of the trend
of color gradients, especially for LTGs, but age gradients are not negligible
and seem to play a significant role too. We have been able to highlight that
older galaxies have systematically shallower age and Z gradients than younger
ones. Our results for high-mass galaxies are in perfect agreement with
predictions based on the merging scenario, while the evolution of LTGs and
younger and less massive ETGs seems to be mainly driven by infall and SN
feedback. (Abridged) | astro-ph_CO |
Dark matter profiles of SPARC galaxies: a challenge to fuzzy dark matter: Stellar and gas kinematics of galaxies are a sensitive probe of the dark
matter distribution in the halo. The popular fuzzy dark matter models predict
the peculiar shape of density distribution in galaxies: specific dense core
with sharp transition to the halo. Moreover, fuzzy dark matter predicts scaling
relations between the dark matter particle mass and density parameters. In this
work, we use a Bayesian framework and several dark matter halo models to
analyse the stellar kinematics of galaxies using the Spitzer Photometry and
Accurate Rotation Curves database. We then employ a Bayesian model comparison
to select the best halo density model. We find that more than half of the
galaxies prefer the fuzzy dark model against standard dark matter profiles
(NFW, Burkert, and cored NFW). While this seems like a success for fuzzy dark
matter, we also find that there is no single value for the particle mass that
provides a good fit for all galaxies. | astro-ph_CO |
Bounds from ISW-galaxy cross-correlations on generalized covariant
Galileon models: Several modified cosmological models exist, which also try to address the
tensions between data and predictions of the $\Lambda$-CDM model. Galileon
models are particular scalar tensor theories that represent one such
possibilities. While it is commonly understood that there may be
inconsistencies between predictions of some Galileon models and observations,
in particular concerning ISW-galaxy cross-correlations, there is no proof yet
that these models are completely ruled out. Indeed, by using a specific
background in the generalized covariant Galileon theory known as the the
tracker solution, here we show that, after imposing all standard theoretical
stability constraints, it is still possible to identify a region in the
parameter space of the model that allows for positive ISW-galaxy
cross-correlations. By a physical interpretation in terms of a chi-square
analysis, we confirm the expectation that in this viable region the predictions
of generalized covariant Galileon theory on the tracker solution background
have higher likelihood when they approach the physics of the $\Lambda$-CDM
model. | astro-ph_CO |
The Dark Matter Density in the Solar Neighborhood reconsidered: Both the gas flaring and the dip in the rotation curve, which was recently
reconfirmed with precise measurements using the VERA VLBI array in Japan,
suggest doughnut-like substructure in the dark matter (DM) halo. A global fit
to all available data shows that the data are indeed best described by an NFW
DM profile complemented by two doughnut-like DM substructures with radii of 4.2
and 12.4 kpc, which coincide with the local dust ring and the Monocerus ring of
stars, respectively. Both regions have been suggested as regions with tidal
streams from "shredded" satellites. If real, the radial extensions of these
nearby ringlike structures enhance the local dark matter density by a factor of
four to about 1.3$\pm0.3$ GeV/cm$^3$.
It is shown that i) this higher DM density is perfectly consistent with the
local gravitational potential determining the surface density and the local
matter density (Oort limit), ii) previous determinations of the surface density
were biased by the assumption of a smoothly varying DM halo and iii) the
s-shaped gas flaring is explained. Such a possible enhancement of the local DM
density is of great interest for direct DM searches and would change the
directional dependence for indirect DM searches. | astro-ph_CO |
On the Evolution of the Cores of Radio Sources and Their Extended Radio
Emission: The work in this paper aims at determining the evolution and possible
co-evolution of radio-loud active galactic nuclei (AGNs) and their cores via
their radio luminosity functions (i.e., total and core RLF respectively). Using
a large combined sample of 1063 radio-loud AGNs selected at low radio
frequency, we investigate the radio luminosity function (RLF) at 408 MHz of
steep-spectrum radio sources. Our results support a luminosity-dependent
evolution. Using core flux density data of the complete sample 3CRR, we
investigate the core RLF at 5.0 GHz. Based on the combined sample with
incomplete core flux data, we also estimate the core RLF using a modified
factor of completeness. Both results are consistent and show that the comoving
number density of radio cores displays a persistent decline with redshift,
implying a negative density evolution. We find that the core RLF is obviously
different from the total RLF at 408 MHz band which is mainly contributed by
extended lobes, implying that the cores and extended lobes could not be
co-evolving at radio emission. | astro-ph_CO |
Evaluating the Calorimeter Model with Broadband, Continuous Spectra of
Starburst Galaxies Observed with the Allen Telescope Array: Although the relationship between the far-infrared and cm-wave radio
luminosities of normal galaxies is one of the most striking correlations in
astronomy, a solid understanding of its physical basis is lacking. In one
interpretation, the "calorimeter model," rapid synchrotron cooling of cosmic
ray electrons is essential in reproducing the observed linear relationship.
Observed radio spectra, however, are shallower than what is expected of cooled
synchrotron emission. In Thompson et al. (2006), a simple parameterized model
is presented to explain how relatively shallow observed spectra might arise
even in the presence of rapid synchrotron cooling by accounting for ionization
losses and other cooling mechanisms. During the commissioning of the 42-element
Allen Telescope Array, we observed the starburst galaxies M82, NGC 253, and Arp
220 at frequencies ranging from 1 to 7 GHz, obtaining unprecedented broadband
continuous radio spectra of these sources. We combine our observations with
high-frequency data from the literature to separate the spectra into thermal
and nonthermal components. The nonthermal components all steepen in the cm-wave
regime and cannot be well-modeled as simple power laws. The model of Thompson
et al. is consistent with our M82 results when plausible parameters are chosen,
and our results in fact significantly shrink the space of allowed model
parameters. The model is only marginally consistent with our NGC 253 data.
Assuming the Thompson et al. model, a steep electron energy injection index of
p = -2.5 is ruled out in M82 and NGC 253 to >99% confidence. We describe in
detail the observing procedures, calibration methods, analysis, and consistency
checks used for broadband spectral observations with the Allen Telescope Array. | astro-ph_CO |
Magnetic field amplification by shocks in galaxy clusters: application
to radio relics: Merger shocks induce turbulence in the intra-cluster medium (ICM), and, under
some circumstances, accelerate electrons to relativistic velocities to form
so-called radio relics. Relics are mostly found at the periphery of galaxy
clusters and appear to have magnetic fields at the microGauss level. Here we
investigate the possible origins of these magnetic fields. Turbulence produced
by the shock itself cannot explain the magnitude of these fields. However, we
argue that if the turbulent pressure support in the ICM upstream of the merger
shock is of the order of 10 to 30 percent of the total pressure on scales of a
few times 100 kpc, then vorticity generated by compressive and baroclinic
effects across the shock discontinuity can lead to a sufficient amplification
of the magnetic field. Compressional amplification can explain the large
polarisation of the radio emission more easily than dynamo turbulent
amplification. Finally, clumping of the ICM is shown to have a negligible
effect on magnetic field amplification. | astro-ph_CO |
The Nature of the Warm/Hot Intergalactic Medium I. Numerical Methods,
Convergence, and OVI Absorption: We perform a series of cosmological simulations using Enzo, an Eulerian
adaptive-mesh refinement, N-body + hydrodynamical code, applied to study the
warm/hot intergalactic medium. The WHIM may be an important component of the
baryons missing observationally at low redshift. We investigate the dependence
of the global star formation rate and mass fraction in various baryonic phases
on spatial resolution and methods of incorporating stellar feedback. Although
both resolution and feedback significantly affect the total mass in the WHIM,
all of our simulations find that the WHIM fraction peaks at z ~ 0.5, declining
to 35-40% at z = 0. We construct samples of synthetic OVI absorption lines from
our highest-resolution simulations, using several models of oxygen ionization
balance. Models that include both collisional ionization and photoionization
provide excellent fits to the observed number density of absorbers per unit
redshift over the full range of column densities (10^13 cm-2 <= N_OVI <= 10^15
cm^-2). Models that include only collisional ionization provide better fits for
high column density absorbers (N_OVI > 10^14 cm^-2). The distribution of OVI in
density and temperature exhibits two populations: one at T ~ 10^5.5 K
(collisionally ionized, 55% of total OVI) and one at T ~ 10^4.5 K
(photoionized, 37%) with the remainder located in dense gas near galaxies.
While not a perfect tracer of hot gas, OVI provides an important tool for a
WHIM baryon census. | astro-ph_CO |
Environmental dependence of bulge-dominated galaxy sizes in hierarchical
models of galaxy formation. Comparison with the local Universe: We compare state-of-the-art semi-analytic models of galaxy formation as well
as advanced sub-halo abundance matching models with a large sample of
early-type galaxies from SDSS at z < 0.3. We focus our attention on the
dependence of median sizes of central galaxies on host halo mass. The data do
not show any difference in the structural properties of early-type galaxies
with environment, at fixed stellar mass. All hierarchical models considered in
this work instead tend to predict a moderate to strong environmental
dependence, with the median size increasing by a factor of about 1.5-3 when
moving from low to high mass host haloes. At face value the discrepancy with
the data is highly significant, especially at the cluster scale, for haloes
above log Mhalo > 14. The convolution with (correlated) observational errors
reduces some of the tension. Despite the observational uncertainties, the data
tend to disfavour hierarchical models characterized by a relevant contribution
of disc instabilities to the formation of spheroids, strong gas dissipation in
(major) mergers, short dynamical friction timescales, and very short quenching
timescales in infalling satellites. We also discuss a variety of additional
related issues, such as the slope and scatter in the local size-stellar mass
relation, the fraction of gas in local early-type galaxies, and the general
predictions on satellite galaxies. | astro-ph_CO |
Starlet l1-norm for weak lensing cosmology: We present a new summary statistic for weak lensing observables, higher than
second order, suitable for extracting non-Gaussian cosmological information and
inferring cosmological parameters. We name this statistic the 'starlet
$\ell_1$-norm' as it is computed via the sum of the absolute values of the
starlet (wavelet) decomposition coefficients of a weak lensing map. In
comparison to the state-of-the-art higher-order statistics -- weak lensing peak
counts and minimum counts, or the combination of the two -- the $\ell_1$-norm
provides a fast multi-scale calculation of the full void and peak distribution,
avoiding the problem of defining what a peak is and what a void is: The
$\ell_1$-norm carries the information encoded in all pixels of the map, not
just the ones in local maxima and minima. We show its potential by applying it
to the weak lensing convergence maps provided by the MassiveNus simulations to
get constraints on the sum of neutrino masses, the matter density parameter,
and the amplitude of the primordial power spectrum. We find that, in an ideal
setting without further systematics, the starlet $\ell_1$-norm remarkably
outperforms commonly used summary statistics, such as the power spectrum or the
combination of peak and void counts, in terms of constraining power,
representing a promising new unified framework to simultaneously account for
the information encoded in peak counts and voids. We find that the starlet
$\ell_1$-norm outperforms the power spectrum by $72\%$ on M$_{\nu}$, $60\%$ on
$\Omega_{\rm m}$, and $75\%$ on $A_{\rm s}$ for the Euclid-like setting
considered; it also improves upon the state-of-the-art combination of peaks and
voids for a single smoothing scale by $24\%$ on M$_{\nu}$, $50\%$ on
$\Omega_{\rm m}$, and $24\%$ on $A_{\rm s}$. | astro-ph_CO |
X-ray measurement of the elemental abundances at the outskirts of the
Perseus cluster with Suzaku: We report on the abundance of metals (Mg and Fe) in the intracluster medium
(ICM) at the outskirts (0.2 r200 - 0.8 r200) of the Perseus cluster. The X-ray
spectra were obtained in the Suzaku/XIS mapping observations of this region. We
employ single temperature models to fit all the X-ray spectra. The ICM
temperature smoothly decreases toward the outer region from 6 keV to 4 keV. The
Fe abundance is uniformly distributed at the outskirts (~0.3 solar). The Mg
abundance is ~1 solar at the outskirts. The solar ratios of Mg/Fe of the
outskirts region (Mg/Fe ~4) are a factor of 4 larger than those of the central
region. Various systematic effects, including the spatial fluctuations in the
cosmic X-ray background, are taken into account and evaluated. These our
results have not changed significantly. | astro-ph_CO |
Average Heating Rate of Hot Atmospheres in Distant Clusters by Radio
AGN: Evidence for Continuous AGN Heating: We examine atmospheric heating by radio active galactic nuclei (AGN) in
distant X-ray clusters by cross correlating clusters selected from the 400
Square Degree (400SD) X-ray Cluster survey with radio sources in the NRAO VLA
Sky Survey. Roughly 30% of the clusters show radio emission above a flux
threshold of 3 mJy within a projected radius of 250 kpc. The radio emission is
presumably associated with the brightest cluster galaxy. The mechanical jet
power for each radio source was determined using scaling relations between
radio power and cavity (mechanical) power determined for nearby clusters,
groups, and galaxies with hot atmospheres containing X-ray cavities. The
average jet power of the central radio AGN is approximately $2\times
10^{44}$\ergs. We find no significant correlation between radio power, hence
mechanical jet power, and the X-ray luminosities of clusters in the redshift
range 0.1 -- 0.6. This implies that the mechanical heating rate per particle is
higher in lower mass, lower X-ray luminosity clusters. The jet power averaged
over the sample corresponds to an atmospheric heating of approximately 0.2 keV
per particle within R$_{500}$. Assuming the current AGN heating rate does not
evolve but remains constant to redshifts of 2, the heating rate per particle
would rise by a factor of two. We find that the energy injected from radio AGN
contribute substantially to the excess entropy in hot atmospheres needed to
break self-similarity in cluster scaling relations. The detection frequency of
radio AGN is inconsistent with the presence of strong cooling flows in 400SD
clusters, but does not exclude weak cooling flows. It is unclear whether
central AGN in 400SD clusters are maintained by feedback at the base of a
cooling flow. Atmospheric heating by radio AGN may retard the development of
strong cooling flows at early epochs. | astro-ph_CO |
CfA3: 185 Type Ia Supernova Light Curves from the CfA: We present multi-band photometry of 185 type-Ia supernovae (SN Ia), with over
11500 observations. These were acquired between 2001 and 2008 at the F. L.
Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics (CfA).
This sample contains the largest number of homogeneously-observed and reduced
nearby SN Ia (z < 0.08) published to date. It more than doubles the nearby
sample, bringing SN Ia cosmology to the point where systematic uncertainties
dominate. Our natural system photometry has a precision of 0.02 mag or better
in BVRIr'i' and roughly 0.04 mag in U for points brighter than 17.5 mag. We
also estimate a systematic uncertainty of 0.03 mag in our SN Ia standard system
BVRIr'i' photometry and 0.07 mag for U. Comparisons of our standard system
photometry with published SN Ia light curves and comparison stars, where
available for the same SN, reveal agreement at the level of a few hundredths
mag in most cases. We find that 1991bg-like SN Ia are sufficiently distinct
from other SN Ia in their color and light-curve-shape/luminosity relation that
they should be treated separately in light-curve/distance fitter training
samples. The CfA3 sample will contribute to the development of better
light-curve/distance fitters, particularly in the few dozen cases where
near-infrared photometry has been obtained and, together, can help disentangle
host-galaxy reddening from intrinsic supernova color, reducing the systematic
uncertainty in SN Ia distances due to dust. | astro-ph_CO |
A Halo Model with Environment Dependence: Theoretical Considerations: We present a modification of the standard halo model with the goal of
providing an improved description of galaxy clustering. Recent surveys, like
the Sloan Digital Sky Survey (SDSS) and the Anglo-Australian Two-degree survey
(2dF), have shown that there seems to be a correlation between the clustering
of galaxies and their properties such as metallicity and star formation rate,
which are believed to be environment-dependent. This environmental dependence
is not included in the standard halo model where the host halo mass is the only
variable specifying galaxy properties. In our approach, the halo properties
i.e., the concentration, and the Halo Occupation Distribution --HOD--
prescription, will not only depend on the halo mass (like in the standard halo
model) but also on the halo environment. We examine how different environmental
dependence of halo concentration and HOD prescription affect the correlation
function. We see that at the level of dark matter, the concentration of haloes
affects moderately the dark matter correlation function only at small scales.
However the galaxy correlation function is extremely sensitive to the HOD
details, even when only the HOD of a small fraction of haloes is modified. | astro-ph_CO |
Non-Gaussianity from Isocurvature Perturbations : Analysis of
Trispectrum: Non-Gaussianity may exist in the CDM isocurvature perturbation. We provide
general expressions for the bispectrum and trispectrum of both adiabatic and
isocurvature pertubations. We apply our result to the QCD axion case, and found
a consistency relation between the coefficients of the bispectrum and
trispectrum : tau_{NL}^(iso)~10^3 [f_{NL}^(iso)]^{4/3}, if the axion is
dominantly produced by quantum fluctuation. Thus future observations of the
trispectrum, as well as the bispectrum, will be important for understanding the
origin of the CDM and baryon asymmetry. | astro-ph_CO |
Accretion of Galaxies around Supermassive Black Holes and a Theoretical
Model of the Tully-Fisher and M-Sigma Relations: The observed Tully-Fisher and Faber-Jackson laws between the baryonic mass of
galaxies and the velocity of motion of stars at the edge of galaxies are
explained within the framework of the model of accretion of galaxies around
supermassive black holes (SMBH). The accretion model can also explain the
M-sigma relation between the mass of a supermassive black hole and the velocity
of stars in the bulge. The difference in the mechanisms of origin of elliptical
galaxies with low angular momentum and disk galaxies with high angular momentum
can be associated with 3D and 2D accretion. | astro-ph_CO |
The ability of Lisa, Taiji, and their networks to detect the stochastic
gravitational wave background generated by Cosmic Strings: The cosmic string contributes to our understanding and revelation of the
fundamental structure and evolutionary patterns of the universe, unifying our
knowledge of the cosmos and unveiling new physical laws and phenomena.
Therefore, we anticipate the detection of Stochastic Gravitational Wave
Background (SGWB) signals generated by cosmic strings in space-based detectors.
We have analyzed the detection capabilities of individual space-based
detectors, Lisa and Taiji, as well as the joint space-based detector network,
Lisa-Taiji, for SGWB signals produced by cosmic strings, taking into account
other astronomical noise sources. The results indicate that the Lisa-Taiji
network exhibits superior capabilities in detecting SGWB signals generated by
cosmic strings and can provide strong evidence. The Lisa-Taiji network can
achieve an uncertainty estimation of $\Delta G\mu/G\mu<0.5$ for cosmic string
tension $G\mu\sim4\times10^{-17}$, and can provide evidence for the presence of
SGWB signals generated by cosmic strings at $G\mu\sim10^{-17}$, and strong
evidence at $G\mu\sim10^{-16}$. Even in the presence of only SGWB signals, it
can achieve a relative uncertainty of $\Delta G\mu/G\mu<0.5$ for cosmic string
tension $G\mu<10^{-18}$, and provide strong evidence at $G\mu\sim10^{-17}$. | astro-ph_CO |
An analytical approximation of the luminosity distance in flat
cosmologies with a cosmological constant: We present an analytical approximation formula for the luminosity distance in
spatially flat cosmologies with dust and a cosmological constant. Apart from
the overall factor, the effect of non-zero cosmological constant in our formula
is written simply in terms of a rational function. We also show the approximate
formulae for the Dyer-Roeder distance (empty beam case) and the generalized
angular diameter distance from redshift $z_1$ to $z_2$, which are particularly
useful in analyzing the gravitational lens effects. Our formulae are widely
applicable over the range of the density parameter and the redshift with
sufficiently small uncertainties. In particular, in the range of density
parameter $0.3 \leq \Omega_{\rm m} \leq 1$ and redshift $0.03 \leq z \leq
1000$, the relative error for the luminosity distance by our formula is always
smaller than that of the recent work by Wickramasinghe and Ukwatta (2010).
Hence, we hope that our formulae will be an efficient and useful tool for
exploring various problems in observational cosmology. | astro-ph_CO |
Weak Lensing Measurements in Simulations of Radio Images: We present a study of weak lensing shear measurements for simulated galaxy
images at radio wavelengths. We construct a simulation pipeline into which we
can input galaxy images of known ellipticity, and with which we then simulate
observations with eMERLIN and the international LOFAR array. The simulations
include the effects of the CLEAN algorithm, uv sampling, observing angle, and
visibility noise, and produce realistic restored images of the galaxies. We
apply a shapelet-based shear measurement method to these images and test our
ability to recover the true source ellipticities. We model and deconvolve the
effective PSF, and find suitable parameters for CLEAN and shapelet
decomposition of galaxies. We demonstrate that ellipticities can be measured
faithfully in these radio simulations, with no evidence of an additive bias and
a modest (10%) multiplicative bias on the ellipticity measurements. Our
simulation pipeline can be used to test shear measurement procedures and
systematics for the next generation of radio telescopes. | astro-ph_CO |
A Universe without Dark Energy and Dark Matter: The universe has evolved to be a filamentary web of galaxies and large
inter-galactic zones of space without matter. The Euclidian nature of the
universe indicates that it is not a 3D manifold within space with an extra
spatial dimension. This justifies our assumption that the FRW space-time
evolves in the inter-galactic zones like separate FRW universes. Thus we do not
necessarily have to consider the entirety of the universe. Our assumption
enables us to prove that: -In the current epoch, space in the intergalactic
zones expands at a constant rate. -In and around galaxies, space expansion is
inhibited. With these results, and an extended Gauss Theorem for a deformed
space, we show that there is no need for the hypothetical Dark Energy (DE) and
Dark Matter (DM) to explain phenomena attributed to them. | astro-ph_CO |
Searching for spin-2 ULDM with gravitational waves interferometers: The detection of gravitational waves from merging binaries has ushered in the
era of gravitational wave interferometer astronomy. Besides these strong,
transient, calamitous events, much weaker signals can be detected if the
oscillations are nearly monochromatic and "continuous", that is, coherent over
a long time. In this work we show that ultra-light dark matter of spin two,
owing to its universal coupling $\alpha$ to Standard Model fields, generates a
signal that is akin to but distinct from a continuous gravitational wave. We
show that this signal could be detected with current and planned gravitational
wave interferometers. In the event of a null detection, current facilities
could constrain the coupling to be below $\alpha\sim10^{-7}$ for frequencies of
tens of Hz, corresponding to dark matter masses around the $10^{-13}$ eV mark.
Future facilities could further lower these upper limits and extend them to
smaller masses down to $10^{-18}$ eV. These limits would be the most stringent
bounds on the spin-2 Yukawa fifth force strength, parametrised by $\alpha$, in
the frequency ranges accessible by gravitational wave interferometers. The
implementation of this type of searches for gravitational wave interferometers
would therefore further our grasp of both dark matter and gravity. | astro-ph_CO |
Constraints on a mixed model of dark matter particles and primordial
black holes from the Galactic 511 keV line: The galactic 511 keV gamma-ray line has been observed since 1970's, and was
identified as the result of electron-positron annihilation, but the origin of
such positrons is still not clear. Apart from the astrophysical explanations,
the possibilities that such positrons come from dark matter (DM) annihilation
are also widely studied. Primordial black hole (PBH) is also an extensively
studied candidate of DM. If PBHs exist, the DM particles may be gravitationally
bound to the PBHs and form halo around PBHs with density spikes. DM
annihilation in these density spikes can enhance the production rate of
positrons from DM particles, but the signal morphology is similar to the
decaying DM. We consider such a mixed model consisting of DM particles and PBHs
and obtain the upper limit from the data of 511 keV gamma-ray line from
INTEGRAL/SPI on the decaying component of DM particles and the constraint on
the PBH abundance. These constraints are general and independent of particle DM
models. For the mixed model consisting of excited DM and PBHs, the constraints
on the PBH abundance can be down to $O(10^{-17})$ for DM particle with mass
around $1~\mathrm{TeV}$, which is more stringent than that obtained from the
extragalactic gamma-ray background. | astro-ph_CO |
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. | astro-ph_CO |
Star formation in galaxy interactions and mergers: This lecture reviews the fundamental physical processes involved in star
formation in galaxy interactions and mergers. Interactions and mergers often
drive intense starbursts, but the link between interstellar gas physics, large
scale interactions, and active star formation is complex and not fully
understood yet. Two processes can drive starbursts: radial inflows of gas can
fuel nuclear starbursts, triggered gas turbulence and fragmentation can drive
more extended starbursts in massive star clusters with high fractions of dense
gas. Both modes are certainly required to account for the observed properties
of starbursting mergers. A particular consequence is that star formation
scaling laws are not universal, but vary from quiescent disks to starbursting
mergers. High-resolution hydrodynamic simulations are used to illustrate the
lectures. | astro-ph_CO |
Exploring 21cm - Lyman Alpha emitter synergies for SKA: We study the signatures of reionization and ionizing properties of the early
galaxies in the cross-correlations between the 21cm emission from the spin-flip
transition of neutral hydrogen (HI) and the underlying galaxy population, in
particular a sub-population of galaxies visible as Lyman Alpha Emitters (LAEs).
With both observables simultaneously derived from a $z\simeq6.6$ hydrodynamical
simulation (GADGET-2) snapshot post-processed with a radiative transfer code
(pCRASH) and a dust model, we perform a parameter study and aim to constrain
both the average intergalactic medium (IGM) ionization state ($1-\langle
\chi_{HI} \rangle$) and the reionization topology (outside-in versus
inside-out). We find that in our model LAEs occupy the densest and most-ionized
regions resulting in a very strong anti-correlation between the LAEs and the
21cm emission. A 1000h SKA-LOW1 - Subaru Hyper Suprime Cam experiment can
provide constraints on $\langle \chi_{HI} \rangle$, allowing us to distinguish
between IGM ionization levels of 50%, 25%, 10% and fully ionized at scales
$r<10$ comoving Mpc (assuming foreground avoidance for SKA). Our results
support the inside-out reionization scenario where the densest knots
(under-dense voids) are ionized first (last) for $\langle \chi_{HI} \rangle >=
0.1$. Further, 1000h SKA-LOW1 observations should be able to confirm the
inside-out scenario by detecting a lower 21cm brightness temperature (by about
2-10 mK) in the densest regions ($> 2$ arcminute scales) hosting LAEs compared
to lower-density regions devoid of them. | astro-ph_CO |
Dark energy in light of the early JWST observations: case for a negative
cosmological constant?: Early data from the James Webb Space Telescope (JWST) has uncovered the
existence of a surprisingly abundant population of very massive galaxies at
extremely high redshift, which are hard to accommodate within the standard
$\Lambda$CDM cosmology. We explore whether the JWST observations may be
pointing towards more complex dynamics in the dark energy (DE) sector.
Motivated by the ubiquity of anti-de Sitter vacua in string theory, we consider
a string-inspired scenario where the DE sector consists of a negative
cosmological constant (nCC) and a evolving component with positive energy
density on top, whose equation of state is allowed to cross the phantom divide.
We show that such a scenario can drastically alter the growth of structure
compared to $\Lambda$CDM, and accommodate the otherwise puzzling JWST
observations if the dynamical component evolves from the quintessence-like
regime in the past to the phantom regime today: in particular, we demonstrate
that the presence of a nCC (which requires a higher density for the evolving
component) plays a crucial role in enhancing the predicted cumulative comoving
stellar mass density. Our work reinforces the enormous potential held by
observations of the abundance of high-$z$ galaxies in probing cosmological
models and new fundamental physics, including string-inspired ingredients. | astro-ph_CO |
Curvaton preheating revisited: We study the thermalization process in the self-interacting curvaton
preheating scenario. We solve the evolution of the system with classical
lattice simulations with a recently released symplectic PyCOOL program during
the resonance and the early thermalization periods and compare the results to
the inflaton preheating. After this we calculate the generated non-gaussianity
with the $\Delta N$ formalism and the separate universe approximation by
running a large number of simulations with slightly different initial values.
The results indicate a high level of non-gaussianity. We also use this paper to
showcase the various post-processing functions included with the PyCOOL program
that is available from https://github.com/jtksai/PyCOOL . | astro-ph_CO |
Simulation-based inference of dynamical galaxy cluster masses with 3D
convolutional neural networks: We present a simulation-based inference framework using a convolutional
neural network to infer dynamical masses of galaxy clusters from their observed
3D projected phase-space distribution, which consists of the projected galaxy
positions in the sky and their line-of-sight velocities. By formulating the
mass estimation problem within this simulation-based inference framework, we
are able to quantify the uncertainties on the inferred masses in a
straightforward and robust way. We generate a realistic mock catalogue
emulating the Sloan Digital Sky Survey (SDSS) Legacy spectroscopic observations
(the main galaxy sample) for redshifts $z \lesssim 0.09$ and explicitly
illustrate the challenges posed by interloper (non-member) galaxies for cluster
mass estimation from actual observations. Our approach constitutes the first
optimal machine learning-based exploitation of the information content of the
full 3D projected phase-space distribution, including both the virialized and
infall cluster regions, for the inference of dynamical cluster masses. We also
present, for the first time, the application of a simulation-based inference
machinery to obtain dynamical masses of around $800$ galaxy clusters found in
the SDSS Legacy Survey, and show that the resulting mass estimates are
consistent with mass measurements from the literature. | astro-ph_CO |
Lagrangian bias of generic large-scale structure tracers: The dark matter halos that host galaxies and clusters form out of initial
high-density patches, providing a biased tracer of the linear matter density
field. In the simplest local bias approximation, the halo field is treated as a
perturbative series in the average overdensity of the Lagrangian patch. In more
realistic models, however, additional quantities will affect the clustering of
halo-patches, and this expansion becomes a function of several stochastic
variables. In this paper, we present a general multivariate expansion scheme
that can parametrize the clustering of any biased Lagrangian tracer, given only
the variables involved and their symmetry (in our case rotational invariance).
This approach is based on an expansion in the orthonormal polynomials
associated with the relevant variables, so that no renormalization of the
coefficients ever occurs. We provide explicit expression for the series
coefficients, or Lagrangian bias parameters, in the case of peaks of the linear
density field. As an application of our formalism, we present a simple
derivation of the original BBKS formula, and compute the non-Gaussian bias in
the presence of a primordial trispectrum of the local shape. | astro-ph_CO |
The growth of density perturbations in the last $\sim$10 billion years
from tomographic large-scale structure data: In order to investigate the origin of the ongoing tension between the
amplitude of matter fluctuations measured by weak lensing experiments at low
redshifts and the value inferred from the cosmic microwave background
anisotropies, we reconstruct the evolution of this amplitude from $z\sim2$
using existing large-scale structure data. To do so, we decouple the linear
growth of density inhomogeneities from the background expansion, and constrain
its redshift dependence making use of a combination of 6 different data sets,
including cosmic shear, galaxy clustering and CMB lensing. We analyze these
data under a consistent harmonic-space angular power spectrum-based pipeline.
We show that current data constrain the amplitude of fluctuations mostly in the
range $0.2<z<0.7$, where it is lower than predicted by Planck. This difference
is mostly driven by current cosmic shear data, although the growth histories
reconstructed from different data combinations are consistent with each other,
and we find no evidence of systematic deviations in any particular experiment.
In spite of the tension with Planck, the data are well-described by the
$\Lambda$CDM model, albeit with a lower value of
$S_8\equiv\sigma_8(\Omega_m/0.3)^{0.5}$. As part of our analysis, we find
constraints on this parameter of $S_8=0.7781\pm0.0094$ (68\% confidence level),
reaching almost percent-level errors comparable with CMB measurements, and
3.4$\sigma$ away from the value found by Planck. | astro-ph_CO |
Pre-galactic metal enrichment - The chemical signatures of the first
stars: The emergence of the first sources of light at redshifts of z ~ 10-30
signaled the transition from the simple initial state of the Universe to one of
increasing complexity. We review recent progress in our understanding of the
formation of the first stars and galaxies, starting with cosmological initial
conditions, primordial gas cooling, and subsequent collapse and fragmentation.
We emphasize the important open question of how the pristine gas was enriched
with heavy chemical elements in the wake of the first supernovae. We conclude
by discussing how the chemical abundance patterns conceivably allow us to probe
the properties of the first stars and subsequent stellar generations, and allow
us to test models of early metal enrichment. | astro-ph_CO |
Dynamics of minimally coupled dark energy in spherical halos of dark
matter: We analyse the evolution of scalar field dark energy in the spherical halos
of dark matter at the late stages of formation of gravitationally bound systems
in the expanding Universe. The dynamics of quintessential dark energy at the
center of dark matter halo strongly depends on the value of effective sound
speed $c_s$ (in units of speed of light). If $c_s\sim1$ (classical scalar
field) then the dark energy in the gravitationally bound systems is only
slightly perturbed and its density is practically the same as in cosmological
background. The dark energy with small value of sound speed ($c_s<0.1$), on the
contrary, is important dynamical component of halo at all stages of their
evolution: linear, non-linear, turnaround, collapse, virialization and later up
to current epoch. These properties of dark energy can be used for constraining
the value of effective sound speed $c_s$ by comparison the theoretical
predictions with observational data related to the large scale gravitationally
bound systems. | astro-ph_CO |
Modeling the clustering of dark-matter haloes in resummed perturbation
theories: We address the issue of the cosmological bias between matter and galaxy
distributions, looking at dark-matter haloes as a first step to characterize
galaxy clustering. Starting from the linear density field at high redshift, we
follow the centre of mass trajectory of the material that will form each halo
at late times (proto-halo). We adopt a fluid-like description for the evolution
of perturbations in the proto-halo distribution, which is coupled to the matter
density field via gravity. We present analytical solutions for the density and
velocity fields, in the context of renormalized perturbation theory. We start
from the linear solution, then compute one-loop corrections for the propagator
and the power spectrum. Finally we analytically resum the propagator and we use
a suitable extension of the time-renormalization-group method (Pietroni 2008)
to resum the power spectrum. For halo masses M<10^{14} Msol/h our results at
z=0 are in good agreement with N-body simulations. Our model is able to predict
the halo-matter cross spectrum with an accuracy of 5 per cent up to k = 0.1
h/Mpc approaching the requirements of future galaxy redshift surveys. | astro-ph_CO |
What we can learn from the spectral index of the tensor mode: If the beginning of inflation is defined at the moment when the vacuum energy
of the inflaton starts to dominate, the energy density of the other fields at
that moment is (by definition) comparable to the inflaton. Although the
fraction will be small at the horizon exit due to the inflationary expansion,
they can alter the scale dependence of the spectrum. At the same time, velocity
of the inflaton field may not coincide with the slow-roll (attractor) velocity.
Those dynamics could be ubiquitous but can easily alter the scale dependence of
the spectrum. Since the scale dependence is currently used to constrain or even
exclude inflation models, it is very important to measure its shift, which is
due to the dynamics that does not appear in the original inflation model.
Considering typical examples, we show that the spectral index of the tensor
mode is a useful measure of such effect. Precise measurement of the higher
runnings of the scalar mode will be helpful in discriminating the source. | astro-ph_CO |
Regularization Scheme Dependence of the Counterterms in the Galaxy Bias
Expansion: In this paper we explore how different regularization prescriptions affect
the counterterms in the renormalization of the galaxy bias expansion. We work
in the context of primordial local non-Gaussianity including non-linear
gravitational evolution. We carry out the one-loop renormalization of the field
$\delta_\rho^2$ (i.e. the square of the matter overdensity field) up to third
order in gravitational evolution. Three regularization schemes are considered
and their impact on the values of the counterterms is studied. We explicitly
verify that the coefficients of the non-boost invariant operators are
regularization scheme independent. | astro-ph_CO |
The large-scale diffuse radio emission in A781: A781 belongs to a complex system characterized by extended X-ray emissions
that may form part of line of clusters of galaxies along a filament. The aim of
this work is to investigate the possible presence of extended, diffuse
synchrotron radio emission connected to the intra-cluster medium of A781. We
studied the radio continuum emission and the spectral index properties in
proximity of the A781 by analyzing archival Very Large Array observations at
1400 and 325 MHz. The main cluster of the system is permeated by diffuse
low-surface brightness radio emission which is classified, being located close
to the center, as a radio halo. The diffuse emission presents the typical
extension and radio power of the other halos known in the literature.
Interestingly, the radio halo appears to be linked to a peripheral patch
previously found in the literature. The spectrum of this peripheral emission
shows a radial steepening which may confirm that this source is indeed a
cluster relic. | astro-ph_CO |
The X-ray spectral properties of the AGN population in the XMM-Newton
bright serendipitous survey: We present here a detailed X-ray spectral analysis of the AGN belonging to
the XMM-Newton bright survey (XBS) that comprises more than 300 AGN up to
redshift ~ 2.4. We performed an X-ray analysis following two different
approaches: by analyzing individually each AGN X-ray spectrum and by
constructing average spectra for different AGN types. From the individual
analysis, we find that there seems to be an anti correlation between the
spectral index and the sources' hard X-ray luminosity, such that the average
photon index for the higher luminosity sources (> 10E44 erg/s) is significantly
flatter than the average for the lower luminosity sources. We also find that
the intrinsic column density distribution agrees with AGN unified schemes,
although a number of exceptions are found (3% of the whole sample), which are
much more common among optically classified type 2 AGN. We also find that the
so-called "soft-excess", apart from the intrinsic absorption, constitutes the
principal deviation from a power-law shape in AGN X-ray spectra and it clearly
displays different characteristics, and likely a different origin, for
unabsorbed and absorbed AGN. Regarding the shape of the average spectra, we
find that it is best reproduced by a combination of an unabsorbed (absorbed)
power law, a narrow Fe Kalpha emission line and a small (large) amount of
reflection for unabsorbed (absorbed) sources. We do not significantly detect
any relativistic contribution to the line emission and we compute an upper
limit for its equivalent width (EW) of 230 eV at the 3 sigma confidence level.
Finally, by dividing the type 1 AGN sample into high- and low-luminosity
sources, we marginally detect a decrease in the narrow Fe Kalpha line EW and in
the amount of reflection as the luminosity increases, the "so-called"
Iwasawa-Taniguchi effect. | astro-ph_CO |
Statistical anisotropy of CMB as a probe of conformal rolling scenario: Search for the statistical anisotropy in the CMB data is a powerful tool for
constraining models of the early Universe. In this paper we focus on the
recently proposed cosmological scenario with conformal rolling. We consider two
sub-scenarios, one of which involves a long intermediate stage between
conformal rolling and conventional hot epoch. Primordial scalar perturbations
generated within these sub-scenarios have different direction-dependent power
spectra, both characterized by a single parameter h^2. We search for the
signatures of this anisotropy in the seven-year WMAP data using quadratic
maximum likelihood method, first applied for similar purposes by Hanson and
Lewis. We confirm the large quadrupole anisotropy detected in V and W bands,
which has been argued to originate from systematic effects rather than from
cosmology. We construct an estimator for the parameter h^2. In the case of the
sub-scenario with the intermediate stage we set an upper limit h^2 < 0.045 at
the 95% confidence level. The constraint on h^2 is much weaker in the case of
another sub-scenario, where the intermediate stage is absent. | astro-ph_CO |
Polar Ring Galaxies in the Galaxy Zoo: We report observations of 16 candidate polar ring galaxies (PRGs) identified
by the Galaxy Zoo project in the Sloan Digital Sky Survey (SDSS) database. Deep
images of five galaxies are available in the SDSS Stripe82 database, while to
reach similar depth we observed the remaining galaxies with the 1.8-m Vatican
Advanced Technology Telescope. We derive integrated magnitudes and u-r colours
for the host and ring components and show continuum-subtracted H\alpha+[NII]
images for seven objects. We present a basic morphological and environmental
analysis of the galaxies and discuss their properties in comparison with other
types of early-type galaxies. Follow-up photometric and spectroscopic
observations will allow a kinematic confirmation of the nature of these systems
and a more detailed analysis of their stellar populations. | astro-ph_CO |
Constraining Dust and Molecular Gas Properties in Lyman Alpha Blobs at
z~3: In order to constrain the bolometric luminosities, dust properties and
molecular gas content of giant Lyman alpha nebulae, the so-called Lyman alpha
blobs, we have carried out a study of dust continuum and CO line emission in
two well-studied representatives of this population at z ~ 3: a Lya blob
discovered by its strong Spitzer MIPS 24um detection (LABd05; Dey et al. 2005)
and the Steidel blob 1 (SSA22-LAB01; Steidel et al. 2000). We find that the
spectral energy distribution of LABd05 is well described by an AGN-starburst
composite template with L(FIR) = (4.0 +/- 0.5) x 10^12 Lsun, comparable to
high-z sub-millimeter galaxies and ultraluminous infrared galaxies. New
APEX/LABOCA 870um measurements rule out the reported SCUBA detection of the
SSA22-LAB01 (S[850um] = 16.8 mJy) at the > 4sigma level. Consistent with this,
ultra-deep Plateau de Bure Interferometer (PdBI) observations with ~2arcsec
spatial resolution also fail to detect any 1.2mm continuum source down to
~0.45mJy per beam (3sigma). Combined with the existing (sub)mm observations in
the literature, we conclude that the FIR luminosity of SSA22-LAB01 remains
uncertain. No CO line is detected in either case down to integrated flux limits
of (Snu dV) < 0.25--1.0 Jy km/s, indicating a modest molecular gas reservoir,
M(H_2) < 1--3 x 10^10 Msun. The non-detections exclude, with high significance
(12 sigma), the previous tentative detection of a CO(4-3) line in the
SSA22-LAB01. The increased sensitivity afforded by ALMA will be critical in
studying molecular gas and dust in these interesting systems. | astro-ph_CO |
Effects of boosting on extragalactic components: methods and statistical
studies: In this work we examine the impact of our motion with respect to the CMB rest
frame on statistics of CMB maps by examining the one-, two-, three- and four-
point statistics of simulated maps of the CMB and Sunyaev-Zeldovich (SZ)
effects. We validate boosting codes by comparing their outcomes for temperature
and polarization power spectra up to $\ell \simeq 6000$. We derive and validate
a new analytical formula for the computation of the boosted power spectrum of a
signal with a generic frequency dependence. As an example we show how this
increases the boosting correction to the power spectrum of CMB intensity
measurements by $\sim 30\%$ at 150 GHz. We examine the effect of boosting on
thermal and kinetic SZ power spectra from semianalytical and hydrodynamical
simulations; the boosting correction is generally small for both simulations,
except when considering frequencies near the tSZ null. For the non-Gaussian
statistics, in general we find that boosting has no impact with two exceptions.
We find that, whilst the statistics of the CMB convergence field are
unaffected, quadratic estimators that are used to measure this field can become
biased at the $O(1)\%$ level by boosting effects. We present a simple
modification to the standard estimators that removes this bias. Second,
bispectrum estimators can receive a systematic bias from the Doppler induced
quadrupole when there is anisotropy in the sky -- in practice this anisotropy
comes from masking and inhomogenous noise. This effect is unobservable and
already removed by existing analysis methods. | astro-ph_CO |
Non-Gaussian Scatter in Cluster Scaling Relations: We investigate the impact of non-Gaussian scatter in the cluster
mass-observable scaling relation on the mass and redshift distribution of
clusters detected by wide area surveys. We parameterize non-Gaussian scatter by
incorporating the third and forth moments (skewness and kurtosis) into the
distribution P(Mobs|M). We demonstrate that for low scatter mass proxies the
higher order moments do not significantly affect the observed cluster mass and
redshift distributions. However, for high scatter mass indicators it is
necessary for the survey limiting mass threshold to be less than 10^14 h^-1
Msol to prevent the skewness from having a significant impact on the observed
number counts, particularly at high redshift. We also show that an unknown
level of non-Gaussianity in the scatter is equivalent to an additional
uncertainty on the variance in P(Mobs|M) and thus may limit the constraints
that can be placed on the dark energy equation of state parameter w.
Furthermore, positive skewness flattens the mass function at the high mass end,
and so one must also account for skewness in P(Mobs|M) when using the shape of
the mass function to constrain cluster scaling-relations. | astro-ph_CO |
A new probe of Axion-Like Particles: CMB polarization distortions due to
cluster magnetic fields: We propose using the upcoming Cosmic Microwave Background (CMB) ground based
experiments to detect the signal of ALPs (Axion like particles) interacting
with magnetic fields in galaxy clusters. The conversion between CMB photons and
ALPs in the presence of the cluster magnetic field can cause a polarized
spectral distortion in the CMB around a galaxy cluster. The strength of the
signal depends upon the redshift of the galaxy cluster and will exhibit a
distinctive spatial profile around it depending upon the structure of electron
density and magnetic field. This distortion produces a different shape from the
other known spectral distortions like $y$-type and $\mu$-type and hence are
separable from the multi-frequency CMB observation. The spectrum is close to
kinematic Sunyaev-Zeldovich (kSZ) signal but can be separated from it using the
polarization information. For the future ground-based CMB experiments such as
Simons Observatory and CMB-S4, we estimate the measurability of this signal in
the presence of foreground contamination, instrument noise and CMB
anisotropies. This new avenue can probe the photon-ALP coupling over the ALP
mass range from $10^{-13}$ eV to $10^{-12}$ eV with two orders of magnitude
better accuracy from CMB-S4 than the current existing bounds. | astro-ph_CO |
Bayesian inferences of galaxy formation from the K-band luminosity and
HI mass functions of galaxies: constraining star formation and feedback: We infer mechanisms of galaxy formation for a broad family of semi-analytic
models (SAMs) constrained by the K-band luminosity function and HI mass
function of local galaxies using tools of Bayesian analysis. Even with a broad
search in parameter space the whole model family fails to match to constraining
data. In the best fitting models, the star formation and feedback parameters in
low-mass haloes are tightly constrained by the two data sets, and the analysis
reveals several generic failures of models that similarly apply to other
existing SAMs. First, based on the assumption that baryon accretion follows the
dark matter accretion, large mass-loading factors are required for haloes with
circular velocities lower than 200 km/s, and most of the wind mass must be
expelled from the haloes. Second, assuming that the feedback is powered by
Type-II supernovae with a Chabrier IMF, the outflow requires more than 25% of
the available SN kinetic energy. Finally, the posterior predictive
distributions for the star formation history are dramatically inconsistent with
observations for masses similar to or smaller than the Milky-Way mass. The
inferences suggest that the current model family is still missing some key
physical processes that regulate the gas accretion and star formation in
galaxies with masses below that of the Milky Way. | astro-ph_CO |
The background Friedmannian Hubble constant in relativistic
inhomogeneous cosmology and the age of the Universe: In relativistic inhomogeneous cosmology, structure formation couples to
average cosmological expansion. A conservative approach to modelling this
assumes an Einstein--de Sitter model (EdS) at early times and extrapolates this
forward in cosmological time as a "background model" against which average
properties of today's Universe can be measured. This requires adopting an
early-epoch--normalised background Hubble constant $H_1^{bg}$. Here, we show
that the $\Lambda$CDM model can be used as an observational proxy to estimate
$H_1^{bg}$ rather than choose it arbitrarily. We assume (i) an EdS model at
early times; (ii) a zero dark energy parameter; (iii) bi-domain scalar
averaging---division of the spatial sections into over- and underdense regions;
and (iv) virialisation (stable clustering) of collapsed regions. We find
$H_1^{bg}= 37.7 \pm 0.4$ km/s/Mpc (random error only) based on a Planck
$\Lambda$CDM observational proxy. Moreover, since the scalar-averaged expansion
rate is expected to exceed the (extrapolated) background expansion rate, the
expected age of the Universe should be much less than $2/(3 H_1^{bg}) = 17.3$
Gyr. The maximum stellar age of Galactic Bulge microlensed low-mass stars (most
likely: 14.7 Gyr; 68\% confidence: 14.0--15.0 Gyr) suggests an age about a Gyr
older than the (no-backreaction) $\Lambda$CDM estimate. | astro-ph_CO |
Relativistic static magnetized finite thin disk: An infinite family of
exact solutions: An infinite family of relativistic finite thin disk model with magnetic field
is presented. The model is obtained for solving the Einstein-Maxwell equations
for static spacetimes by means of the Horsk\'y-Mitskievitch generating
conjecture. The vacuum limit of these obtained solutions is the well known
Morgan and Morgan solution. The obtained expressions are simply written in
terms of oblate spheroidal coordinates. The mass of the disks are finite and
the energy-momentum tensor agrees with all the energy conditions. The magnetic
field and the circular velocity are evaluated explicitly. All the physical
quantities obtained shown an acceptable | astro-ph_CO |
The evolution of dusty torus covering factor in quasars: We have assembled a large sample of 5996 quasars at redshift 2.0=< z <= 2.4
(high-z) or 0.7=< z <= 1.1 (low-z) from SDSS data release nine and seven quasar
catalogs. The spectral energy distribution (SED) of quasars were constructed by
collecting WISE, UKIDSS, and GALEX photometric data in addition to SDSS, from
which the IR luminosity at 1-7 \mu m and bolometric luminosity at 1100 \AA - 1
\mu m were calculated. A red tail is clearly seen in the distributions of the
spectral index in 1100 \AA - 1 \mu m both for high-z and low-z sources, which
is likely due to red or reddened quasars. The covering factor of dusty torus is
estimated as the ratio of the IR luminosity to the bolometric luminosity. We
found significant anti-correlations between the covering factor and bolometric
luminosity, in both high-z and low-z quasars, however they follow different
tracks. At overlapped bolometric luminosity, the covering factor of high-z
quasars are systematically larger than those of low-z quasars, implying an
evolution of covering factor with redshift. | astro-ph_CO |
On the tension between growth rate and CMB data: We analyze the claimed tension between redshift space distorsions
measurements of $f(z)\sigma_8(z)$ and the predictions of standard $\Lambda$CDM
(Planck 2015 and 2018) cosmology. We consider a dataset consisting of 17 data
points extending up to redshift $z=1.52$ and corrected for the Alcock-Paczynski
effect. Thus, calculating the evolution of the growth factor in a $w$CDM
cosmology, we find that the tension for the best fit parameters $w$, $\Omega_m$
and $\sigma_8$ with respect to the Planck 2018 $\Lambda$CDM parameters is below
$2\sigma$ in all the marginalized confidence regions. | astro-ph_CO |
Detection of Cosmic Magnification via Galaxy Shear -- Galaxy Number
Density Correlation from HSC Survey Data: We propose a novel method to detect cosmic magnification signals by
cross-correlating foreground convergence fields constructed from galaxy shear
measurements with background galaxy positional distributions, namely
shear-number density correlation. We apply it to the Hyper Suprime-Cam Subaru
Strategic Program (HSC-SSP) survey data. With 27 non-independent data points
and their full covariance, $\chi_0^2\approx 34.1$ and $\chi_T^2\approx 24.0$
with respect to the null and the cosmological model with the parameters from
HSC shear correlation analyses in Hamana et al. 2020 (arXiv:1906.06041),
respectively. The Bayes factor of the two is $\log_{10}B_{T0}\approx 2.2$
assuming equal model probabilities of null and HSC cosmology, showing a clear
detection of the magnification signals. Theoretically, the ratio of the
shear-number density and shear-shear correlations can provide a constraint on
the effective multiplicative shear bias $\bar m$ using internal data
themselves. We demonstrate the idea with the signals from our HSC-SSP mock
simulations and rescaling the statistical uncertainties to a survey of
$15000\deg^2$. For two-bin analyses with background galaxies brighter than
$m_{lim}=23$, the combined analyses lead to a forecasted constraint of
$\sigma(\bar m) \sim 0.032$, $2.3$ times tighter than that of using the
shear-shear correlation alone. Correspondingly, $\sigma(S_8)$ with
$S_8=\sigma_8(\Omega_\mathrm{m}/0.3)^{0.5}$ is tightened by $\sim 2.1$ times.
Importantly, the joint constraint on $\bar m$ is nearly independent of
cosmological parameters. Our studies therefore point to the importance of
including the shear-number density correlation in weak lensing analyses, which
can provide valuable consistency tests of observational data, and thus to
solidify the derived cosmological constraints. | astro-ph_CO |
H0 Revisited: I reanalyse the Riess et al. (2011, hereafter R11) Cepheid data using the
revised geometric maser distance to NGC 4258 of Humphreys et al. (2013). I
explore different outlier rejection criteria designed to give a reduced
chi-squared of unity and compare the results with the R11 rejection algorithm,
which produces a reduced chi-squared that is substantially less than unity and,
in some cases, to underestimates of the errors on parameters. I show that there
are sub-luminous low metallicity Cepheids in the R11 sample that skew the
global fits of the period-luminosity relation. This has a small but
non-negligible impact on the global fits using NGC 4258 as a distance scale
anchor, but adds a poorly constrained source of systematic error when using the
Large Magellanic Cloud (LMC) as an anchor. I also show that the small Milky Way
(MW) Cepheid sample with accurate parallax measurements leads to a distance to
NGC 4258 that is in tension with the maser distance. I conclude that H0 based
on the NGC 4258 maser distance is H0 = 70.6 +/- 3.3 km/s/Mpc compatible within
1 sigma with the recent determination from Planck for the base six-parameter
LCDM cosmology. If the H-band period-luminosity relation is assumed to be
independent of metallicity and the three distance anchors are combined, I find
H0 = 72.5 +/- 2.5 km/s/Mpc, which differs by 1.9 sigma from the Planck value.
The differences between the Planck results and these estimates of H0 are not
large enough to provide compelling evidence for new physics at this stage. | astro-ph_CO |
Growth of matter perturbations in the extended viscous dark energy
models: In this work, we study the extended viscous dark energy models in the context
of matter perturbations. To do this, we assume an alternative interpretation of
the flat Friedmann-Lema\^itre-Robertson-Walker Universe, through the
nonadditive entropy and the viscous dark energy. We implement the relativistic
equations to obtain the growth of matter fluctuations for a smooth version of
dark energy. As result, we show that the matter density contrast evolves
similarly to the $\Lambda$CDM model in high redshift; in late time, it is
slightly different from the standard model. Using the latest geometrical and
growth rate observational data, we carry out a Bayesian analysis to constrain
parameters and compare models. We see that our viscous models are compatible
with cosmological probes, and the $\Lambda$CDM recovered with a $1\sigma$
confidence level. The viscous dark energy models relieve the tension of $H_0$
in $2 \sim 3 \sigma$. Yet, by involving the $\sigma_8$ tension, some models can
alleviate it. In the model selection framework, the data discards the extended
viscous dark energy models. | astro-ph_CO |
SDSS superclusters: morphology and galaxy content: We compare the galaxy populations in superclusters of different morphology in
the nearby Universe (180 < d < 270 Mpc) to see whether the inner structure and
overall morphology of superclusters are important in shaping galaxy properties
in superclusters. Supercluster morphology has been found with Minkowski
functionals. We analyse the probability density distributions of colours,
morphological types, stellar masses, star formation rates (SFR) of galaxies,
and the peculiar velocities of the main galaxies in groups in superclusters of
filament and spider types, and in the field. We show that the fraction of red,
early-type, low SFR galaxies in filament-type superclusters is higher than in
spider-type superclusters; in low-density global environments their fraction is
lower than in superclusters. In all environments the fraction of red, high
stellar mass, and low SFR galaxies in rich groups is higher than in poor
groups. In superclusters of spider morphology red, high SFR galaxies have
higher stellar masses than in filament-type superclusters. Groups of equal
richness host galaxies with larger stellar masses, a larger fraction of
early-type and red galaxies, and a higher fraction of low SFR galaxies, if they
are located in superclusters of filament morphology. The peculiar velocities of
the main galaxies in groups from superclusters of filament morphology are
higher than in those of spider morphology. Groups with higher peculiar
velocities of their main galaxies in filament-type superclusters are located in
higher density environment than those with low peculiar velocities. There are
significant differences between galaxy populations of the individual richest
superclusters. Therefore both local (group) and global (supercluster)
environments and even supercluster morphology play an important role in the
formation and evolution of galaxies. | astro-ph_CO |
The state of the dark energy equation of state circa 2023: We critically examine the state of current constraints on the dark energy
(DE) equation of state (EoS) $w$. Our study is partially motivated by the
observation that, while broadly consistent with the cosmological constant value
$w=-1$, several independent probes appear to point towards a slightly phantom
EoS ($w \sim -1.03$). We pay attention to the apparent preference for phantom
DE from Planck Cosmic Microwave Background (CMB) data alone, whose origin we
study in detail and attribute to a wide range of (physical and geometrical)
effects. We deem the combination of Planck CMB, Baryon Acoustic Oscillations,
Type Ia Supernovae, and Cosmic Chronometers data to be particularly
trustworthy, inferring from this final consensus dataset
$w=-1.013^{+0.038}_{-0.043}$, in excellent agreement with the cosmological
constant value. Overall, despite a few scattered hints, we find no compelling
evidence forcing us away from the cosmological constant (yet). | astro-ph_CO |
The supermassive black hole mass - Sérsic index relations for bulges
and elliptical galaxies: Scaling relations between supermassive black hole mass, M_BH, and host galaxy
properties are a powerful instrument for studying their coevolution. A complete
picture involving all of the black hole scaling relations, in which each
relation is consistent with the others, is necessary to fully understand the
black hole-galaxy connection. The relation between M_BH and the central light
concentration of the surrounding bulge, quantified by the S\'ersic index n, may
be one of the simplest and strongest such relations, requiring only
uncalibrated galaxy images. We have conducted a census of literature S\'ersic
index measurements for a sample of 54 local galaxies with directly measured
M_BH values. We find a clear M_BH - n relation, despite an appreciable level of
scatter due to the heterogeneity of the data. Given the current M_BH - L_sph
and the L_sph - n relations, we have additionally derived the expected M_BH - n
relations, which are marginally consistent at the 2 sigma level with the
observed relations. Elliptical galaxies and the bulges of disc galaxies are
each expected to follow two distinct bent M_BH - n relations due to the
S\'ersic/core-S\'ersic divide. For the same central light concentration, we
predict that M_BH in the S\'ersic bulges of disc galaxies are an order
magnitude higher than in S\'ersic elliptical galaxies if they follow the same
M_BH - L_sph relation. | astro-ph_CO |
Gas and dark matter in the Sculptor group: NGC 55: We present new, sensitive HI observations of the Sculptor group galaxy NGC 55
with the Australia Telescope Compact Array. We achieve a 5 sigma HI column
density sensitivity of 10^19 cm^-2 over a spectral channel width of 8 km/s for
emission filling the 158" x 84" synthesised beam. Our observations reveal for
the first time the full extent of the HI disc of NGC 55 at this sensitivity and
at a moderately high spatial resolution of about 1 kpc.
The HI disc of NGC 55 appears to be distorted on all scales. There is a
strong east-west asymmetry in the column density distribution along the major
axis, suggesting that the disc is under the influence of ram-pressure forces.
We also find evidence of streaming motions of the gas along the bar of NGC 55.
The fitting of tilted rings to the velocity field reveals a strong warping of
the outer gas disc which could be the result of tidal interaction with either
NGC 300 or a smaller satellite galaxy. Finally, we find a large number of
distinct clumps and spurs across the entire disc, indicating that internal or
external processes, such as satellite accretion or gas outflows, have stirred
up the gas disc.
We also detect several isolated HI clouds within about 20 kpc projected
distance from NGC 55. Their dynamical properties and apparent concentration
around NGC 55 suggest that most of the clouds are forming a circum-galactic
population similar to the high-velocity clouds of the Milky Way and M31,
although two of the clouds could be foreground objects and part of the
Magellanic Stream. While it is difficult to determine the origin of these
clouds, our data seem to favour either tidal stripping or gas outflows as the
source of the gas. | astro-ph_CO |
ALFALFA HI Data Stacking II. HI content of the host galaxies of AGN: We use a stacking technique to measure the average HI content of a
volume-limited sample of 1871 AGN host galaxies from a parent sample of
galaxies selected from the SDSS and GALEX imaging surveys with stellar masses
greater than 10^10 M_sun and redshifts in the range 0.025<z<0.05. HI data are
available from the Arecibo Legacy Fast ALFA (ALFALFA) survey. In previous work,
we found that the HI gas fraction in galaxies correlates most strongly with the
combination of optical/UV colour and stellar surface mass density. We therefore
build a control sample of non-AGN matched to the AGN hosts in these two
properties. We study trends in HI gas mass fraction (M(HI)/M_*), where M_* is
the stellar mass) as a function of black hole accretion rate indicator
L[OIII]/M(BH). We find no significant difference in HI content between AGN and
control samples at all values of black hole accretion rate probed by the
galaxies in our sample. This indicates that AGN do not influence the
large-scale gaseous properties of galaxies in the local Universe. We have
studied the variation in HI mass fraction with black hole accretion rate in the
blue and red galaxy populations. In the blue population, the HI gas fraction is
independent of accretion rate, indicating that accretion is not sensitive to
the properties of the interstellar medium of the galaxy on large scales.
However, in the red population accretion rate and gas fraction do correlate.
The measured gas fractions in this population are not too different from the
ones expected from a stellar mass loss origin, implying that the fuel supply in
the red AGN population could be a mixture of mass loss from stars and gas
present in disks. | astro-ph_CO |
Galaxy properties in clusters. II. Backsplash Galaxies: We explore the properties of galaxies on the outskirts of clusters and their
dependence on recent dynamical history in order to understand the real impact
that the cluster core has on the evolution of galaxies. We analyse the
properties of more than 1000 galaxies brighter than $M_{^{0.1}r}$=-19.6 on the
outskirts of 90 clusters ($1<r/r_{vir}<2$) in the redshift range $0.05<z<0.10$.
Using the line of sight velocity, we selected high and low velocity subsamples.
Theoretical predictions indicate that a significant fraction of the first
subsample should be backsplash galaxies, that is, objects that have already
orbited near the cluster centre. A significant proportion of the sample of high
relative velocity HV galaxies seems to be composed of infalling objects. Our
results suggest that, at fixed stellar mass, late type galaxies in the low
velocity LV sample are systematically older, redder and have formed fewer stars
during the last 3 Gyrs than galaxies in the HV sample. This result is
consistent with models that assume that the central regions of clusters are
effective in quenching the star formation by means of processes such as ram
pressure stripping or strangulation. At fixed stellar mass, LV galaxies show
some evidence of having higher surface brightness and smaller size than HV
galaxies. These results are consistent with the scenario where galaxies that
have orbited the central regions of clusters are more likely to suffer tidal
effects, producing loss of mass as well as a redistribution of matter towards
more compact configurations. Finally, we found a higher fraction of ET galaxies
in the LV sample, supporting the idea that the central region of clusters of
galaxies may contribute to the transformation of morphological types towards
earlier types. | astro-ph_CO |
The Galactic Halo in Mixed Dark Matter Cosmologies: A possible solution to the small scale problems of the cold dark matter (CDM)
scenario is that the dark matter consists of two components, a cold and a warm
one. We perform a set of high resolution simulations of the Milky Way halo
varying the mass of the WDM particle ($m_{\rm WDM}$) and the cosmic dark matter
mass fraction in the WDM component ($\bar{f}_{\rm W}$). The scaling ansatz
introduced in combined analysis of LHC and astroparticle searches postulates
that the relative contribution of each dark matter component is the same
locally as on average in the Universe (e.g. $f_{\rm W,\odot} = \bar{f}_{\rm
W}$). Here we find however, that the normalised local WDM fraction ($f_{\rm
W,\odot}$ / $\bar{f}_{\rm W}$) depends strongly on $m_{\rm WDM}$ for $m_{\rm
WDM} <$ 1 keV. Using the scaling ansatz can therefore introduce significant
errors into the interpretation of dark matter searches. To correct this issue a
simple formula that fits the local dark matter densities of each component is
provided. | astro-ph_CO |
Cosmology from weak lensing of CMB: The weak lensing effect on the cosmic microwave background (CMB) induces
distortions in spatial pattern of CMB anisotropies, and statistical properties
of CMB anisotropies become a weakly non-Gaussian field. We first summarize the
weak lensing effect on the CMB (CMB lensing) in the presence of scalar, vector
and tensor perturbations. Then we focus on the lensing effect on CMB statistics
and methods to estimate deflection angles and their power spectrum. We end by
summarizing recent observational progress and future prospect. | astro-ph_CO |
The Mira Distance Ladder: Here we provide a review of Mira variables, their basic properties, and
Period-Luminosity Relations with an emphasis on their role in measuring the
Hubble Constant. The usage of multiple independent distance indicators and
methods is crucial to cross-checking systematic uncertainties in distance
measurements and in reinforcing previous findings of the Hubble tension. To
this end, Mira variables serve as an alternative Type Ia Supernova calibrator
to the more commonly-used Cepheid variables or Tip of the Red Giant Branch
method. They also have the potential to expand the number of local SN Ia
calibrators by calibrating previously-inaccessible SNe Ia. Short-period ($P
\lesssim 400$ d) O-rich Miras are a ubiquitous older population that can reach
galaxies not hosting the younger Cepheids variables or out of reach to the old
but fainter Tip of the Red Giant Branch. With the current and upcoming focus on
infrared observations, Miras, which can be discovered and characterized using
exclusively near-infrared and infrared observations, will be particularly
useful in obtaining distances to astrophysical objects. Long-period Miras ($P
\gtrsim 400$ d) are highly luminous variables that have the potential to
measure $H_0$ directly, excluding Type Ia SNe altogether in the distance
ladder. | astro-ph_CO |
Mitigating the impact of the CIB on galaxy cluster SZ detection with
spectrally constrained matched filters: Galaxy clusters detected through the thermal Sunyaev-Zeldovich (tSZ) effect
are a powerful cosmological probe from which constraints on cosmological
parameters such as $\Omega_{\mathrm{m}}$ and $\sigma_8$ can be derived. The
measured cluster tSZ signal can be, however, contaminated by Cosmic Infrared
Background (CIB) emission, as the CIB is spatially correlated with the cluster
tSZ field. We quantify the extent of this contamination by applying the
iterative multi-frequency matched filter (iMMF) cluster-finding method to mock
Planck-like data from the Websky simulation. We find a significant bias in the
retrieved cluster tSZ observables (signal-to-noise and Compton-$y$ amplitude),
at the level of about $0.5\, \sigma$ per cluster. This CIB-induced bias
translates into about $20$% fewer detections than expected if all the Planck
HFI channels are used in the analysis, which can potentially bias derived
cosmological constraints. We introduce a spectrally constrained iMMF, or
sciMMF, which proves to be highly effective at suppressing this CIB-induced
bias from the tSZ cluster observables by spectrally deprojecting the
cluster-correlated CIB at the expense of a small signal-to-noise penalty. Our
sciMMF is also robust to modelling uncertainties, namely to the choice of
deprojection spectral energy distribution. With it, CIB-free cluster catalogues
can be constructed and used for cosmological inference. We provide a publicly
available implementation of our sciMMF as part of the SZiFi package. | astro-ph_CO |
Principal components of dark energy with SNLS supernovae: the effects of
systematic errors: We study the effects of current systematic errors in Type Ia supernova (SN
Ia) measurements on dark energy (DE) constraints using current data from the
Supernova Legacy Survey (SNLS). We consider how SN systematic errors affect
constraints from combined SN Ia, baryon acoustic oscillations (BAO), and cosmic
microwave background (CMB) data, given that SNe Ia still provide the strongest
constraints on DE but are arguably subject to more significant systematics than
the latter two probes. We focus our attention on the temporal evolution of DE
described in terms of principal components (PCs) of the equation of state,
though we examine a few of the more common, simpler parametrizations as well.
We find that the SN Ia systematics degrade the total generalized figure of
merit (FoM), which characterizes constraints in multi-dimensional DE parameter
space, by a factor of two to three. Nevertheless, overall constraints obtained
on more than five PCs are very good even with current data and systematics. We
further show that current constraints are robust to allowing for the finite
detection significance of the BAO feature in galaxy surveys. | astro-ph_CO |
Energetic galaxy-wide outflows in high-redshift ultra-luminous infrared
galaxies hosting AGN activity: We present integral field spectroscopy observations, covering the [O
III]4959,5007 emission-line doublet of eight high-redshift (z=1.4-3.4)
ultra-luminous infrared galaxies (ULIRGs) that host Active Galactic Nuclei
(AGN) activity, including known sub-millimetre luminous galaxies (SMGs). The
targets have moderate radio luminosities that are typical of high-redshift
ULIRGs (L(1.4GHz)=10^(24)-10^(25)W/Hz) and therefore are not radio-loud AGN. We
de-couple kinematic components due to the galaxy dynamics and mergers from
those due to outflows. We find evidence in the four most luminous systems (L([O
III])>~10^(43)erg/s) for the signatures of large-scale energetic outflows:
extremely broad [O III] emission (FWHM ~ 700-1400km/s) across ~4-15kpc, with
high velocity offsets from the systemic redshifts (up to ~850km/s). The four
less luminous systems have lower quality data displaying weaker evidence for
spatially extended outflows. We estimate that these outflows are potentially
depositing energy into their host galaxies at considerable rates
(~10^(43)-10^(45)erg/s); however, due to the lack of constraints on the density
of the outflowing material and the structure of the outflow, these estimates
should be taken as illustrative only. Based on the measured maximum velocities
(v(max)~400-1400km/s) the outflows observed are likely to unbind some fraction
of the gas from their host galaxies, but are unlikely to completely remove gas
from the galaxy haloes. By using a combination of energetic arguments and a
comparison to ULIRGs without clear evidence for AGN activity, we show that the
AGN activity could be the dominant power source for driving all of the observed
outflows, although star formation may also play a significant role in some of
the sources. | astro-ph_CO |
Inferences of $H_0$ in presence of a non-standard recombination: Measurements of the Hubble parameter from the distance ladder are in tension
with indirect measurements based on the cosmic microwave background (CMB) data
and the inverse distance ladder measurements at 3-4 $\sigma$ level. We consider
phenomenological modification to the timing and width of the recombination
process and show that they can significantly affect this tension. This
possibility is appealing, because such modification affects both the distance
to the last scattering surface and the calibration of the baryon acoustic
oscillations (BAO) ruler. Moreover, because only a very small fraction of the
most energetic photons keep the early universe in the plasma state, it is
possible that such modification could occur without affecting the energy
density budget of the universe or being incompatible with the very tight limits
on the departure from the black-body spectrum of CMB. In particular, we find
that under this simplified model, with a conservative subset of Planck data
alone, $H_0=73.44_{-6.77}^{+5.50}~{\rm km\ s}^{-1}\ {\rm Mpc}^{-1}$ and in
combination with BAO data $H_0=68.86_{-1.35}^{+1.31}~{\rm km\ s}^{-1}\ {\rm
Mpc}^{-1}$, decreasing the tension to $\sim 2\sigma$ level. However, when
combined with Planck lensing reconstruction and high-$\ell$ polarization data,
the tension climbs back to $\sim 2.7\sigma$, despite the uncertainty on
non-ladder $H_0$ measurement more than doubling. | astro-ph_CO |
First Constraints on Small-Scale Non-Gaussianity from UV Galaxy
Luminosity Functions: UV luminosity functions provide a wealth of information on the physics of
galaxy formation in the early Universe. Given that this probe indirectly tracks
the evolution of the mass function of dark matter halos, it has the potential
to constrain alternative theories of structure formation. One of such scenarios
is the existence of primordial non-Gaussianity at scales beyond those probed by
observations of the Cosmic Microwave Background. Through its impact on the halo
mass function, such small-scale non-Gaussianity would alter the abundance of
galaxies at high redshifts. In this work we present an application of UV
luminosity functions as measured by the Hubble Space Telescope to constrain the
non-Gaussianity parameter $f_\mathrm{NL}$ for wavenumbers above a cut-off scale
$k_{\rm cut}$. After marginalizing over the unknown astrophysical parameters
and accounting for potential systematic errors, we arrive at a $2\sigma$ bound
of $f_{\rm NL}=71^{+426}_{-237}$ for a cut-off scale $k_{\rm
cut}=0.1\,\mathrm{Mpc}^{-1}$ in the bispectrum of the primordial gravitational
potential. Moreover, we perform forecasts for the James Webb Space Telescope
and the Nancy Grace Roman Space Telescope, finding an expected improvement of a
factor $3-4$ upon the current bound. | astro-ph_CO |
Redshift and distances in a ΛCDM cosmology with non-linear
inhomogeneities: Motivated by the dawn of precision cosmology and the wealth of forthcoming
high precision and volume galaxy surveys, in this paper we study the effects of
inhomogeneities on light propagation in a flat \Lambda CDM background. To this
end we use exact solutions of Einstein's equations (Meures & Bruni 2011) where,
starting from small fluctuations, inhomogeneities arise from a standard growing
mode and become non-linear. While the matter distribution in these models is
necessarily idealised, there is still enough freedom to assume an arbitrary
initial density profile along the line of sight. We can therefore model
over-densities and voids of various sizes and distributions, e.g. single
harmonic sinusoidal modes, coupled modes, and more general distributions in a
\Lambda CDM background. Our models allow for an exact treatment of the light
propagation problem, so that the results are unaffected by approximations and
unambiguous. Along lines of sight with density inhomogeneities which average
out on scales less than the Hubble radius, we find the distance redshift
relation to diverge negligibly from the Friedmann-Lemaitre-Robertson-Walker
(FLRW) result. On the contrary, if we observe along lines of sight which do not
have the same average density as the background, we find large deviations from
the FLRW distance redshift relation. Hence, a possibly large systematic might
be introduced into the analysis of cosmological observations, e.g. supernovae,
if we observe along lines of sight which are typically more or less dense than
the average density of the Universe. In turn, this could lead to wrong
parameter estimation: even if the Cosmological Principle is valid, the
identification of the true FLRW background in an inhomogeneous universe maybe
more difficult than usually assumed. | astro-ph_CO |
The Stellar Halos of Massive Elliptical Galaxies II: Detailed Abundance
Ratios at Large Radius: We study the radial dependence in stellar populations of 33 nearby early-type
galaxies with central stellar velocity dispersions sigma* > 150 km/s. We
measure stellar population properties in composite spectra, and use ratios of
these composites to highlight the largest spectral changes as a function of
radius. Based on stellar population modeling, the typical star at 2 R_e is old
(~10 Gyr), relatively metal poor ([Fe/H] -0.5), and alpha-enhanced
([Mg/Fe]~0.3). The stars were made rapidly at z~1.5-2 in shallow potential
wells. Declining radial gradients in [C/Fe], which follow [Fe/H], also arise
from rapid star formation timescales due to declining carbon yields from
low-metallicity massive stars. In contrast, [N/Fe] remains high at large
radius. Stars at large radius have different abundance ratio patterns from
stars in the center of any present-day galaxy, but are similar to Milky Way
thick disk stars. Our observations are thus consistent with a picture in which
the stellar outskirts are built up through minor mergers with disky galaxies
whose star formation is truncated early (z~1.5-2). | astro-ph_CO |
The contribution of star-forming galaxies to fluctuations in the cosmic
background light: Star-forming galaxies which are too faint to be detected individually produce
intensity fluctuations in the cosmic background light. This contribution needs
to be taken into account as a foreground when using the primordial signal to
constrain cosmological parameters. The extragalactic fluctuations are also
interesting in their own right as they depend on the star formation history of
the Universe and the way in which this connects with the formation of cosmic
structure. We present a new framework which allows us to predict the occupation
of dark matter haloes by star-forming galaxies and uses this information, in
conjunction with an N-body simulation of structure formation, to predict the
power spectrum of intensity fluctuations in the infrared background. We compute
the emission from galaxies at far-infrared, millimetre and radio wavelengths.
Our method gives accurate predictions for the clustering of galaxies both for
the one halo and two halo terms. We illustrate our new framework using a
previously published model which reproduces the number counts and redshift
distribution of galaxies selected by their emission at $850\,\mu$m. Without
adjusting any of the model parameters, the predictions show encouraging
agreement at high frequencies and on small angular scales with recent estimates
of the extragalactic fluctuations in the background made from early data
analysed by the Planck Collaboration. There are, however, substantial
discrepancies between the model predictions and observations on large angular
scales and at low frequencies, which illustrates the usefulness of the
intensity fluctuations as a constraint on galaxy formation models. | astro-ph_CO |
The VIMOS Public Extragalactic Redshift Survey (VIPERS): A quiescent
formation of massive red-sequence galaxies over the past 9 Gyr: We explore the evolution of the Colour-Magnitude Relation (CMR) and
Luminosity Function (LF) at 0.4<z<1.3 from the VIMOS Public Extragalactic
Redshift Survey (VIPERS) using ~45,000 galaxies with precise spectroscopic
redshifts down to i'_AB<22.5 over ~10.32 deg^2 in two fields. From z=0.5 to
z=1.3 the LF and CMR are well defined for different galaxy populations and
M^*_B evolves by ~1.04(1.09)+/-0.06(0.10) mag for the total (red) galaxy
sample. We compare different criteria for selecting early-type galaxies (ETGs):
(1) fixed cut in rest-frame (U-V) colours, (2) evolving cut in (U-V) colours,
(3) rest-frame (NUV-r')-(r'-K) colour selection, and (4) SED classification.
Regardless of the method we measure a consistent evolution of the red-sequence
(RS). Between 0.4<z<1.3 we find a moderate evolution of the RS intercept of
Delta(U-V)=0.28+/-0.14 mag, favouring exponentially declining star formation
(SF) histories with SF truncation at 1.7<=z<=2.3. Together with the rise in the
ETG number density by 0.64 dex since z=1, this suggests a rapid build-up of
massive galaxies (M>10^11 M_sun) and expeditious RS formation over a short
period of ~1.5 Gyr starting before z=1. This is supported by the detection of
ongoing SF in ETGs at 0.9<z<1.0, in contrast with the quiescent red stellar
populations of ETGs at 0.5<z<0.6. There is an increase in the observed CMR
scatter with redshift, two times larger than in galaxy clusters and at variance
with theoretical models. We discuss possible physical mechanisms that support
the observed evolution of the red galaxy population. Our findings point out
that massive galaxies have experienced a sharp SF quenching at z~1 with only
limited additional merging. In contrast, less-massive galaxies experience a mix
of SF truncation and minor mergers which build-up the low- and
intermediate-mass end of the CMR. | astro-ph_CO |
Observational Constraints on Varying-alpha Domain Walls: We consider the possibility that current hints of spatial variations of the
fine structure constant at high redshift, based on VLT/UVES and Keck/HIRES
observations, could be caused by a biased domain wall network described by a
scalar field non-minimally coupled to the electromagnetic field. We show that
in order to be responsible for the reported spatial variations of the fine
structure constant, the fractional contribution of the domain wall network to
the energy density of the Universe should be tightly constrained within the
range $10^{-10} < \Omega_{w0} < 10^{-5}$. We also show that the domain wall
dynamics should be essentially frictionless, so that its characteristic scale
is in the order of the Hubble radius at the present time. | astro-ph_CO |
Star Formation Indicators and Line Equivalent Width in Lyman Alpha
Galaxies: The equivalent width (EW) of the Lyman Alpha (Lya) line is directly related
to the ratio of star formation rates determined from Lya flux and UV flux
density [SFR(Lya)/SFR(UV)]. We use published data --in the literature EW and
SFR(Lya)/SFR(UV) are treated as independent quantities-- to show that the
predicted relation holds for the vast majority of observed Lya emitting
galaxies (LAEs). We show that the relation between EW and SFR(Lya)/SFR(UV)
applies irrespective of a galaxy's `true' underlying star formation rate, and
that its only source of scatter is the variation in the spectral slope of the
UV continuum between individual galaxies. The derived relation, when combined
with the observed EW distribution, implies that the ratio SFR(UV)/SFR(Lya) is
described well by a log-normal distribution with a standard deviation of
~0.3-0.35. This result is useful when modelling the statistical properties of
LAEs. We further discuss why the relation between EW and SFR(Lya)/SFR(UV) may
help identifying galaxies with unusual stellar populations. | astro-ph_CO |
The nature of gas and stars in the circumnuclear regions of AGN: a
chemical approach: Aim of this communication is to describe the first results of a
work-in-progress regarding the chemical properties of gas and stars in the
circumnuclear regions of nearby galaxies. Different techniques have been
employed to estimate the abundances of chemical elements in the gaseous and
stellar components of nuclear surroundings in different classes of galaxies
according to the level of activity of the nucleus (normal or passive, star
forming galaxies and AGNs). | astro-ph_CO |
CANDELS: Constraining the AGN-Merger Connection with Host Morphologies
at z~2: Using HST/WFC3 imaging taken as part of the Cosmic Assembly Near-infrared
Deep Extragalactic Legacy Survey (CANDELS), we examine the role that major
galaxy mergers play in triggering active galactic nuclei (AGN) activity at z~2.
Our sample consists of 72 moderate-luminosity (Lx ~ 1E42-1E44 erg/s) AGN at
1.5<z<2.5 that are selected using the 4 Msec Chandra observations in the
Chandra Deep Field South, the deepest X-ray observations to date. Employing
visual classifications, we have analyzed the rest-frame optical morphologies of
the AGN host galaxies and compared them to a mass-matched control sample of 216
non-active galaxies at the same redshift. We find that most of the AGN reside
in disk galaxies (51.4%), while a smaller percentage are found in spheroids
(27.8%). Roughly 16.7% of the AGN hosts have highly disturbed morphologies and
appear to be involved in a major merger or interaction, while most of the hosts
(55.6%) appear relatively relaxed and undisturbed. These fractions are
statistically consistent with the fraction of control galaxies that show
similar morphological disturbances. These results suggest that the hosts of
moderate-luminosity AGN are no more likely to be involved in an ongoing merger
or interaction relative to non-active galaxies of similar mass at z~2. The high
disk fraction observed among the AGN hosts also appears to be at odds with
predictions that merger-driven accretion should be the dominant AGN fueling
mode at z~2, even at moderate X-ray luminosities. Although we cannot rule out
that minor mergers are responsible for triggering these systems, the presence
of a large population of relatively undisturbed disk-like hosts suggests that
secular processes play a greater role in fueling AGN activity at z~2 than
previously thought. | astro-ph_CO |
Rapid-response mode VLT/UVES spectroscopy of super iron-rich gas exposed
to GRB 080310. Evidence of ionization in action and episodic star formation
in the host: We analyse high-resolution near-UV and optical spectra of the afterglow of
GRB 080310, obtained with the Very Large Telescope Ultraviolet and Visual
Echelle Spectrograph (VLT/UVES), to investigate the circumburst environment and
the interstellar medium of the gamma-ray burst (GRB) host galaxy. The VLT
rapid-response mode (RRM) enabled the observations to start only 13 minutes
after the Swift trigger and a series of four exposures to be collected before
dawn. A low neutral-hydrogen column-density (log N (HI) = 18.7) is measured at
the host-galaxy redshift of z = 2.42743. At this redshift, we also detect a
large number of resonance ground-state absorption lines (e.g., CII, MgII, AlII,
SiII, CrII, CIV, SiIV), as well as time-varying absorption from the
fine-structure levels of FeII. Time-varying absorption from a highly excited
FeIII energy level (7S3), giving rise to the so-called UV34 line triplet, is
also detected, for the first time in a GRB afterglow. The CrII ground-state and
all observed FeII energy levels are found to depopulate with time, whilst the
FeIII 7S3 level is increasingly populated. This absorption-line variability is
clear evidence of ionization by the GRB, which is for the first time
conclusively observed in a GRB afterglow spectrum. We derive ionic column
densities at each epoch of observations by fitting absorption lines with a
four-component Voigt-profile model. We perform CLOUDY photo-ionization
modelling of the expected pre-burst ionic column densities, to estimate that,
before the onset of the burst, [C/H] = -1.3 \pm 0.2, [O/H] < -0.8, [Si/H] =
-1.2 \pm 0.2, [Cr/H] = +0.7 \pm 0.2, and [Fe/H] = +0.2 \pm 0.2 for the
integrated line profile, indicating strong overabundances of iron and chromium.
For one of the components, we observe even more extreme ratios of [Si/Fe] \leq
-1.47 and [C/Fe] \leq -1.74. [abridged] | astro-ph_CO |
The Origin of Dark Matter Halo Profiles: A longstanding puzzle of fundamental importance in modern cosmology has been
the origin of the nearly universal density profiles of dark matter halos found
in N-body simulations -- the so-called NFW profile. We show how this behavior
may be understood, simply, by applying adiabatic contraction to peaks of
Gaussian random fields. We argue that dynamical friction acts to reduce
enormously the effect of random scatter in the properties of initial peaks,
providing a key simplification. We compare our model predictions with results
of the ultra-high resolution Via Lactea-II N-body simulation, and find superb
agreement. We show how our model may be used to predict the distribution of
halo properties like concentration. Our results suggest that many of the basic
properties of halo structure may be understood using extremely simple physics. | astro-ph_CO |
A Spectroscopic Search for Leaking Lyman Continuum at z~0.7: We present the results of rest-frame, UV slitless spectroscopic observations
of a sample of 32 z~0.7 Lyman break galaxy (LBG) analogs in the COSMOS field.
The spectroscopic search was performed with the Solar Blind Channel (SBC) on
Hubble Space Telescope. We report the detection of leaking Lyman continuum
(LyC) radiation from an AGN-starburst composite. While we find no direct
detections of LyC emission in the remainder of our sample, we achieve
individual lower limits (3 sigma) of the observed non-ionizing UV to LyC flux
density ratios, f_{nu}(1500A)/f_{nu}(830A) of 20 to 204 (median of 73.5) and
378.7 for the stack. Assuming an intrinsic Lyman break of 3.4 and an
intergalactic medium (IGM) transmission of LyC photons along the line of sight
to the galaxy of 85% we report an upper limit for the relative escape fraction
in individual galaxies of 0.02 - 0.19 and a stacked 3 sigma upper limit of
0.01. We find no indication of a relative escape fraction near unity as seen in
some LBGs at z~3. Our UV spectra achieve the deepest limits to date at any
redshift for the escape fraction in individual sources. The contrast between
these z~0.7 low escape fraction LBG analogs with z~3 LBGs suggests that either
the processes conducive to high escape fractions are not being selected for in
the z<1 samples or the average escape fraction is decreasing from z~3 to z~1.
We discuss possible mechanisms which could affect the escape of LyC photons. | astro-ph_CO |
21 cm Intensity Mapping with the DSA-2000: Line intensity mapping is a promising probe of the universe's large-scale
structure. We explore the sensitivity of the DSA-2000, a forthcoming array
consisting of over 2000 dishes, to the statistical power spectrum of neutral
hydrogen's 21 cm emission line. These measurements would reveal the
distribution of neutral hydrogen throughout the near-redshift universe without
necessitating resolving individual sources. The success of these measurements
relies on the instrument's sensitivity and resilience to systematics. We show
that the DSA-2000 will have the sensitivity needed to detect the 21 cm power
spectrum at z=0.5 and across power spectrum modes of 0.03-31.32 h/Mpc with 0.1
h/Mpc resolution. We find that supplementing the nominal array design with a
dense core of 200 antennas will expand its sensitivity at low power spectrum
modes and enable measurement of Baryon Acoustic Oscillations (BAOs). Finally,
we present a qualitative discussion of the DSA-2000's unique resilience to
sources of systematic error that can preclude 21 cm intensity mapping. | astro-ph_CO |
The strong environmental dependence of black hole scaling relations: We investigate how the scaling relations between central black hole mass
(Mbh) and host galaxy properties (velocity dispersion, bulge stellar mass and
bulge luminosity) depend on the large scale environment. For each of a sample
of 69 galaxies with dynamical black hole measurements we compile four
environmental measures (nearest neighbor distance, fixed aperture number
density, total halo mass, and central/satellite). We find that central and
satellite galaxies follow distinctly separate scalings in each of the three
relations we have examined. The Mbh - sigma relation of central galaxies is
significantly steeper (6.38 +/- 0.49) than that of satellite galaxies (4.91 +/-
0.49), but has a similar intercept. This behavior remains even after
restricting to a sample of only early type galaxies or after removing the 8
brightest cluster galaxies. The Mbh - sigma relation shows more modest
differences when splitting the sample based on the other environmental
indicators, suggesting that they are driven by the underlying satellite/central
fractions. Separate relations for centrals and satellites are also seen in the
power law scaling between black hole mass and bulge stellar mass or bulge
luminosity. We suggest that gas rich, low mass galaxies undergo a period of
rapid black hole growth in the process of becoming satellites. If central
galaxies on the current Mbh - sigma relation are representative progenitors of
the satellite population, the observations imply that a sigma = 120 km/s galaxy
must nearly triple its central black hole mass. The elevated black hole masses
of massive central galaxies are then a natural consequence of the accretion of
satellites. | astro-ph_CO |
Probing the Early Universe with Axion Physics and Gravitational Waves: We show results for the expected reach of the network of experiments that is
being set up globally with the aim of detecting the "invisible" axion, in light
of a non-standard thermal history of the universe. Assuming that the axion is
the dark matter, we discuss the reach of a successful detection by a given
experimental setup in a particular axion mass window for different
modifications of the cosmological background before primordial nucleosynthesis
occurred. Results are presented both in the case where the present energy
budget in cold axions is produced through the vacuum realignment mechanism
alone, or in the case in which axionic strings also provide with additional
contributions to the axion energy density. We also show that in some
cosmological models, the spectrum of gravitational waves from the axionic
string network would be within reach of the future network of detectors like
LISA and DECIGO-BBO. We conclude that some scenarios describing the early
universe can be probed jointly by the experimental efforts on axion detection
and by gravity wave multi-messenger astronomy. | astro-ph_CO |
Hubble flow variations as a test for inhomogeneous cosmology: Context. Backreactions from large-scale inhomogeneities may provide an
elegant explanation for the observed accelerated expansion of the universe
without the need to introduce dark energy. Aims. We propose a cosmological test
for a specific model of inhomogeneous cosmology, called timescape cosmology.
Using large-scale galaxy surveys such as SDSS and 2MRS, we test the variation
of expansion expected in the $\Lambda$-CDM model versus a more generic
differential expansion using our own calibrations of bounds suggested by
timescape cosmology. Method. Our test measures the systematic variations of the
Hubble flow towards distant galaxies groups as a function of the matter
distribution in the lines of sight to those galaxy groups. We compare the
observed systematic variation of the Hubble flow to mock catalogues from the
Millennium Simulation in the case of the $\Lambda$-CDM model, and a deformed
version of the same simulation that exhibits more pronounced differential
expansion. Results. We perform a series of statistical tests, ranging from
linear regressions to Kolmogorov-Smirnov tests, on the obtained data. They
consistently yield results preferring $\Lambda$-CDM cosmology over our
approximated model of timescape cosmology. Conclusions. Our analysis of
observational data shows no evidence that the variation of expansion differs
from that of the standard $\Lambda$-CDM model. | astro-ph_CO |
Growth of structures using redshift space distortion in $f(T)$ Cosmology: Cosmology faces a pressing challenge with the Hubble constant ($H_0$)
tension, where the locally measured rate of the Universe's expansion does not
align with predictions from the cosmic microwave background (CMB) calibrated
with $\Lambda$CDM model. Simultaneously, there is a growing tension involving
the weighted amplitude of matter fluctuations, known as $S_{8,0}$ tension.
Resolving both tensions within one framework would boost confidence in any one
particular model. In this work, we analyse constraints in $f(T)$ gravity, a
framework that shows promise in shedding light on cosmic evolution. We
thoroughly examine prominent $f(T)$ gravity models using a combination of data
sources, including Pantheon+ (SN), cosmic chronometers (CC), baryonic acoustic
oscillations (BAO) and redshift space distortion (RSD) data. We use these
models to derive a spectrum of $H_0$ and $S_{8,0}$ values, aiming to gauge
their ability to provide insights into, and potentially address, the challenges
posed by the $H_0$ and $S_{8,0}$ tensions. | astro-ph_CO |
What is the super-sample covariance? A fresh perspective for
second-order shear statistics: Cosmological analyses of second-order weak lensing statistics require precise
and accurate covariance estimates. These covariances are impacted by two
sometimes neglected terms: A negative contribution to the Gaussian covariance
due to finite survey area and the super-sample covariance (SSC) which for the
power spectrum contains the impact by Fourier modes larger than the survey
window. We show here that these two effects are connected and can be seen as
correction terms to the "large-field-approximation", the asymptotic case of an
infinitely large survey area. We describe the two terms collectively as
"Finite-Field-Terms".
We derive the covariance of second-order shear statistics from first
principles. For this, we use an estimator in real space without relying on an
estimator for the power spectrum. The resulting covariance does not scale
inversely with the survey area, as naively assumed. This scaling is only
correct under the large-field approximation when the contribution of the
finite-field terms tends to zero. Furthermore, all parts of the covariance, not
only the SSC, depend on the power- and trispectrum at all modes, including
those larger than the survey. We also show that it is generally impossible to
transform an estimate for the power spectrum covariance into the covariance of
a real-space statistic. Such a transformation is only possible in the
asymptotic case of the "large-field approximation".
Additionally, we find that the total covariance of a real-space statistic can
be calculated using correlation functions estimates on spatial scales smaller
than the survey window. Consequently, estimating covariances of real-space
statistics, in principle, does not require information on spatial scales larger
than the survey area. We demonstrate that this covariance estimation method is
equivalent to the standard sample covariance method. | astro-ph_CO |
CMB distortion anisotropies due to the decay of primordial magnetic
fields: We investigate the power spectrum of the distortion of Cosmic Microwave
Background (CMB) due to the decay of the primordial magnetic fields. It is
known that there are two-types of the CMB distortions, so-called \mu- and
y-types and we find that the signal of the y-type distortion becomes larger
than that of the \mu-type one. We also discuss cross power spectra between the
CMB distortions and the CMB temperature anisotropy, which are naturally
generated due to the existence of the primordial magnetic fields. We find that
such cross power spectra have small amplitudes compared with the auto-power
spectra of the CMB distortions because of the Silk damping effect of the
temperature anisotropy. We also investigate the possibility of detecting such
signal in the future CMB experiments, including not only absolutely calibrated
experiments such as PIXIE but also relatively calibrated experiments such as
LiteBIRD and CMBpol. | astro-ph_CO |
Suppression of Star Formation in the central 200 kpc of a z = 1.4 Galaxy
Cluster [Erratum added]: We present the results of an extended narrow-band H{\alpha} study of the
massive galaxy cluster XMMU J2235.3-2557 at z = 1.39. This paper represents a
follow up study to our previous investigation of star-formation in the cluster
centre, extending our analysis out to a projected cluster radius of 1.5 Mpc.
Using the Near InfraRed Imager and Spectrograph (NIRI) on Gemini North we
obtained deep H narrow-band imaging corresponding to the rest-frame wavelength
of H{\alpha} at the cluster's redshift. We identify a total of 163 potential
cluster members in both pointings, excluding stars based on their near-IR
colours derived from VLT/HAWK-I imaging. Of these 163 objects 14 are
spectroscopically confirmed cluster members, and 20% are excess line-emitters.
We find no evidence of star formation activity within a radius of 200 kpc of
the brightest cluster galaxy in the cluster core. Dust-corrected star formation
rates (SFR) of excess emitters outside this cluster quenching radius, RQ \sim
200 kpc, are on average <SFR> = 2.7 \pm 1.0 M\odot yr-1, but do not show
evidence of increasing star-formation rates toward the extreme 1.5 Mpc radius
of the cluster. No individual cluster galaxy exceeds an SFR of 6 M\odot yr-1 .
Massive galaxies (log M\ast /M\odot > 10.75) all have low specific SFRs (SSFRs,
i.e. SFR per unit stellar mass). At fixed stellar mass, galaxies in the cluster
centre have lower SSFRs than the rest of the cluster galaxies, which in turn
have lower SSFRs than field galaxies at the same redshift by a factor of a few
to 10. For the first time we can demonstrate through measurements of individual
SFRs that already at very early epochs (at an age of the Universe of \sim4.5
Gyr) the suppression of star-formation is an effect of the cluster environment
which persists at fixed galaxy stellar mass. [Erratum added after the original
paper] | astro-ph_CO |
A common colour-magnitude relation from giant elliptical galaxies to
globular clusters?: We discuss the existence of a common colour-magnitude relation (CMR) of
metal-poor globular clusters and early-type galaxies, i.e. giant ellipticals,
normal ellipticals and lenticulars, dwarf ellipticals and lenticulars, and
dwarf spheroidals. Such CMR would cover a range of ~ 14 mag, extending from the
brightest galaxies, down to the globular clusters on the fainter side. | astro-ph_CO |
Application of the iterative reconstruction to simulated galaxy fields: We apply an iterative reconstruction method to galaxy mocks in redshift space
obtained from $N$-body simulations. Comparing the two-point correlation
functions for the reconstructed density field, we find that although the
performance is limited by shot noise and galaxy bias compared to the matter
field, the iterative method can still reconstruct the initial linear density
field from the galaxy field better than the standard method both in real and in
redshift space. Furthermore, the iterative method is able to reconstruct both
the monopole and quadrupole more precisely, unlike the standard method. We see
that as the number density of galaxies gets smaller, the performance of
reconstruction gets worse due to the sparseness. However, the precision in the
determination of bias ($\sim20\%$) hardly impacts on the reconstruction
processes. | astro-ph_CO |
Cosmic Dawn: Studies of the Earliest Galaxies and Their Role in Cosmic
Reionization: I review recent progress and challenges in studies of the earliest galaxies,
seen when the Universe was less than 1 billion years old. Can they be used as
reliable tracers of the physics of cosmic reionization thereby complementing
other, more direct, probes of the evolving neutrality of the intergalactic
medium? Were star-forming galaxies the primary agent in the reionization
process and what are the future prospects for identifying the earliest systems
devoid of chemical enrichment? Ambitious future facilities are under
construction for exploring galaxies and the intergalactic medium in the
redshift range 6 to 20, corresponding to what we now consider the heart of the
reionization era. I review what we can infer about this period from current
observations and in the near-future with existing facilities, and conclude with
a list of key issues where future work is required. | astro-ph_CO |
A candle in the wind: a radio filament in the core of the A3562 galaxy
cluster: Using a MeerKAT observation of the galaxy cluster A3562 (a member of the
Shapley Supercluster), we have discovered a narrow, long and straight, very
faint radio filament, which branches out at a straight angle from the tail of a
radio galaxy located in projection near the core of the cluster. The radio
filament spans 200 kpc and aligns with a sloshing cold front seen in the
X-rays, staying inside the front in projection. The radio spectral index along
the filament appears uniform (within large uncertainties) at $\alpha\simeq
-1.5$. We propose that the radio galaxy is located outside the cold front, but
dips its tail under the front. The tangential wind that blows there may stretch
the radio plasma from the radio galaxy into a filamentary structure. Some
reacceleration is needed in this scenario to maintain the radio spectrum
uniform. Alternatively, the cosmic ray electrons from that spot in the tail can
spread along the cluster magnetic field lines, straightened by that same
tangential flow, via anomalously fast diffusion. Our radio filament can provide
constraints on this process. We also uncover a compact radio source at the
Brightest Cluster Galaxy (BCG) that is 2--3 orders of magnitude less luminous
than those in typical cluster central galaxies -- probably an example of a BCG
starved of accretion fuel by gas sloshing. | astro-ph_CO |
Cosmological distances with general-relativistic ray tracing: framework
and comparison to cosmographic predictions: In this work we present the first results from a new ray-tracing tool to
calculate cosmological distances in the context of fully nonlinear general
relativity. We use this tool to study the ability of the general cosmographic
representation of luminosity distance, as truncated at third order in redshift,
to accurately capture anisotropies in the "true" luminosity distance. We use
numerical relativity simulations of cosmological large-scale structure
formation which are free from common simplifying assumptions in cosmology. We
find the general, third-order cosmography is accurate to within 1% for
redshifts to z\approx 0.034 when sampling scales strictly above 100 Mpc/h,
which is in agreement with an earlier prediction. We find the inclusion of
small-scale structure generally spoils the ability of the third-order
cosmography to accurately reproduce the full luminosity distance for wide
redshift intervals, as might be expected. For a simulation sampling small-scale
structures, we find a +/- 5% variance in the monopole of the ray-traced
luminosity distance at z \approx 0.02. Further, all 25 observers we study here
see a 9--20% variance in the luminosity distance across their sky at z \approx
0.03, which reduces to 2--5% by z \approx 0.1. These calculations are based on
simulations and ray tracing which adopt fully nonlinear general relativity, and
highlight the potential importance of fair sky-sampling in low-redshift
isotropic cosmological analysis. | astro-ph_CO |
Proper Size of the Visible Universe in FRW Metrics with Constant
Spacetime Curvature: In this paper, we continue to examine the fundamental basis for the
Friedmann-Robertson-Walker (FRW) metric and its application to cosmology,
specifically addressing the question: What is the proper size of the visible
universe? There are several ways of answering the question of size, though
often with an incomplete understanding of how far light has actually traveled
in reaching us today from the most remote sources. The difficulty usually
arises from an inconsistent use of the coordinates, or an over-interpretation
of the physical meaning of quantities such as the so-called proper distance
R(t)=a(t)r, written in terms of the (unchanging) co-moving radius r and the
universal expansion factor a(t). In this paper, we use the five non-trivial FRW
metrics with constant spacetime curvature (i.e., the static FRW metrics, but
excluding Minkowski) to prove that in static FRW spacetimes in which expansion
began from an initial signularity, the visible universe today has a proper size
equal to R_h(t_0/2), i.e., the gravitational horizon at half its current age.
The exceptions are de Sitter and Lanczos, whose contents had pre-existing
positions away from the origin. In so doing, we confirm earlier results showing
the same phenomenon in a broad range of cosmologies, including LCDM, based on
the numerical integration of null geodesic equations through an FRW metric. | astro-ph_CO |
A Search for Magnetized Quark Nuggets (MQNs), a Candidate for Dark
Matter, Accumulating in Iron Ore: A search has been carried out for Magnetized Quark Nuggets (MQNs)
accumulating in iron ore over geologic time. MQNs, which are theoretically
consistent with the Standard Models of Physics and of Cosmology, have been
suggested as dark-matter candidates. Indirect evidence of MQNs has been
previously inferred from observations of magnetars and of non-meteorite impact
craters. It is shown in this paper that MQNs can accumulate in taconite (iron
ore) and be transferred into ferromagnetic rod-mill liners during processing of
the ore. When the liners are recycled to make fresh steel, they are heated to
higher than the Curie temperature so that their ferromagnetic properties are
destroyed. The MQNs would then be released and fall into the ferromagnetic
furnace bottom where they would be trapped. Three such furnace bottoms have
been magnetically scanned to search for the magnetic anomalies consistent with
trapped MQNs. The observed magnetic anomalies are equivalent to an accumulation
rate of ~1 kg of MQNs per 1.2 x $10^8$ kg of taconite ore processed. The
results are consistent with MQNs but there could be other, unknown
explanations. We propose an experiment and calculations to definitively test
the MQN hypothesis for dark matter. | astro-ph_CO |
Neutrino masses from CMB B-mode polarization and cosmic growth rate: Constraints on neutrino masses are estimated based on future observations of
the cosmic microwave background (CMB), which includes the B-mode polarization
produced by CMB lensing from the Planck satellite, and the growth rate of
cosmic structure from the Euclid redshift survey by using the Markov-Chain
Monte-Carlo (MCMC) method. The error in the bound on the total neutrino mass is
estimated to be $\Delta\sum m_{\nu} = 0.075$ eV with a 68\% confidence level.
By using the growth rate rather than the galaxy power spectrum, accurate
constraints are obtained, since the growth rate is less influenced by the
uncertainty regarding galaxy bias than by the galaxy power spectrum. | astro-ph_CO |
Lensing convergence in galaxy clustering in LambdaCDM and beyond: We study the impact of neglecting lensing magnification in galaxy clustering
analyses for future galaxy surveys, considering the LambdaCDM model and two
extensions: massive neutrinos and modifications of General Relativity. Our
study focuses on the biases on the constraints and on the estimation of the
cosmological parameters. We perform a comprehensive investigation of these two
effects for the upcoming photometric and spectroscopic galaxy surveys Euclid
and SKA for different redshift binning configurations. We also provide a
fitting formula for the magnification bias of SKA. Our results show that the
information present in the lensing contribution does improve the constraints on
the modified gravity parameters whereas the lensing constraining power is
negligible for the LambdaCDM parameters. For photometric surveys the estimation
is biased for all the parameters if lensing is not taken into account. This
effect is particularly significant for the modified gravity parameters.
Conversely for spectroscopic surveys the bias is below one sigma for all the
parameters. Our findings show the importance of including lensing in galaxy
clustering analyses for testing General Relativity and to constrain the
parameters which describe its modifications. | astro-ph_CO |
Reconstructing the dark energy potential: Dark energy equation of state can be effectively described by that of a
barotropic fluid. The barotropic fluid model describes the background evolution
and the functional form of the equation of state parameter is well constrained
by the observations. Equally viable explanations of dark energy are via scalar
field models, both canonical and non-canonical; these scalar field models being
low energy descriptions of an underlying high energy theory. In this paper, we
attempt to reconcile the two approaches to dark energy by way of reconstructing
the evolution of the scalar field potential. For this analysis, we consider
canonical quintessence scalar field and the phantom field for this
reconstruction. We attempt to understand the analytical or semi-analytical
forms of scalar field potentials corresponding to typical well behaved
parameterisations of dark energy using the constraints from recent
observations. | astro-ph_CO |