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Canonical transformations and squeezing formalism in cosmology: Canonical transformations are ubiquitous in Hamiltonian mechanics, since they
not only describe the fundamental invariance of the theory under phase-space
reparameterisations, but also generate the dynamics of the system. In the first
part of this work we study the symplectic structure associated with linear
canonical transformations. After reviewing salient mathematical properties of
the symplectic group in a pedagogical way, we introduce the squeezing
formalism, and show how any linear dynamics can be cast in terms of an
invariant representation. In the second part, we apply these results to the
case of cosmological perturbations, and focus on scalar field fluctuations
during inflation. We show that different canonical variables select out
different vacuum states, and that this leaves an ambiguity in observational
predictions if initial conditions are set at a finite time in the past. We also
discuss how the effectiveness of the quantum-to-classical transition of
cosmological perturbations depends on the set of canonical variables used to
describe them. | astro-ph_CO |
Active Galactic Nuclei Selected from GALEX Spectroscopy: The Ionizing
Source Spectrum at z~1: We use a complete sample of Lya emission-line selected AGNs obtained from
nine deep blank fields observed with the grism spectrographs on the Galaxy
Evolution Explorer (GALEX) satellite to measure the normalization and spectral
shape of the AGN contribution to the ionizing background (rest-frame
wavelengths 700-900 A) at z~1. Our sample consists of 139 sources selected in
the redshift range z=0.65-1.25 in the near-ultraviolet (NUV; 2371 A central
wavelength) channel. The area covered is 8.2 square degrees to a NUV magnitude
of 20.5 (AB) and 0.92 square degrees at the faintest magnitude limit of 21.8.
The GALEX AGN luminosity function agrees well with those obtained using optical
and X-ray AGN samples, and the measured redshift evolution of the ionizing
volume emissivity is similar to that previously obtained by measuring the GALEX
far-ultraviolet (FUV; 1528 A central wavelength) magnitudes of an X-ray
selected sample. For the first time we are able to construct the shape of the
ionizing background at z~1 in a fully self-consistent way. | astro-ph_CO |
Re-examining the case for neutral gas near the redshift 7 quasar ULAS
J1120+0641: Signs of damping wing absorption attenuating the Lyman-$\alpha$ emission line
of the first known $z \sim 7$ quasar, ULAS J1120+0641, recently provided
exciting evidence of a significantly neutral IGM. This long-awaited signature
of reionization was inferred, in part, from a deficit of flux in the quasar's
Lyman-$\alpha$ emission line based on predictions from a composite of
lower-redshift quasars. The composite sample was chosen based on its C IV
emission line properties; however, as the original study by Mortlock et al.
noted, the composite contained a slight velocity offset in C IV compared to
ULAS J1120+0641. Here we test whether this offset may be related to the
predicted strength of the Lyman-$\alpha$ emission line. We confirm the
significant ($\sim 10$ per cent at r.m.s.) scatter in Lyman-$\alpha$ flux for
quasars of a given C IV velocity and equivalent width found by Mortlock et al.
We further find that among lower-redshift objects chosen to more closely match
the C IV properties of ULAS J1120+0641, its Lyman-$\alpha$ emission falls
within the observed distribution of fluxes. Among lower-redshift quasars chosen
to more closely match in C IV velocity and equivalent width, we find that ULAS
J1120+0641 falls within the observed distribution of Lyman-$\alpha$ emission
line strengths. This suggests that damping wing absorption may not be present,
potentially weakening the case for neutral gas around this object. Larger
samples of z$>$7 quasars may therefore be needed to establish a clearer picture
of the IGM neutral fraction at these redshifts. | astro-ph_CO |
The Effect of Modified Gravity on the Odds of the Bound Violations of
the Turn-Around Radii: The turn-around radii of the galaxy groups show the imprint of a long battle
between their self-gravitational forces and the accelerating space. The
standard $\Lambda$CDM cosmology based on the general relativity (GR) predicts
the existence of an upper bound on the expectation value of the turn-around
radius which is rarely violated by individual galaxy groups. We speculate that
a deviation of the gravitational law from GR on the cosmological scale could
cause an appreciable shift of the mean turn-around radius to higher values and
make the occurrence of the bound violation more probable. Analyzing the data
from high-resolution N-body simulations for two specific models with modified
gravity (MG) and the standard GR+$\Lambda$CDM cosmology, we determine the
turn-around radii of the massive Rockstar groups from the peculiar motions of
the galactic halos located in the bound zone where the fifth force generated by
MG is expected to be at most partially shielded. We detect a $4\sigma$ signal
of difference in the odds of the bound violations between a fiducial MG and the
GR models, proving that the odds of the bound violations increase with the
strength of the fifth force produced by the presence of MG. The advantage of
using the odds of the bound violations as a complementary diagnostics to probe
the nature of gravity is discussed. | astro-ph_CO |
Constraining the mass of light bosonic dark matter using SDSS
Lyman-$α$ forest: If a significant fraction of the dark matter in the Universe is made of an
ultra-light scalar field, named fuzzy dark matter (FDM) with a mass $m_a$ of
the order of $10^{-22}-10^{-21}$ eV, then its de Broglie wavelength is large
enough to impact the physics of large scale structure formation. In particular,
the associated cut-off in the linear matter power spectrum modifies the
structure of the intergalactic medium (IGM) at the scales probed by the
Lyman-$\alpha$ forest of distant quasars. We study this effect by making use of
dedicated cosmological simulations which take into account the hydrodynamics of
the IGM. We explore heuristically the amplitude of quantum pressure for the FDM
masses considered here and conclude that quantum effects should not modify
significantly the non-linear evolution of matter density at the scales relevant
to the measured Lyman-$\alpha$ flux power, and for $m_a \geq 10^{-22}$ eV. We
derive a scaling law between $m_a$ and the mass of the well-studied thermal
warm dark matter (WDM) model that is best adapted to the Lyman-$\alpha$ forest
data, and differs significantly from the one infered by a simple linear
extrapolation. By comparing FDM simulations with the Lyman-$\alpha$ flux power
spectra determined from the BOSS survey, and marginalizing over relevant
nuisance parameters, we exclude FDM masses in the range $10^{-22} \leq m_a <
2.3\times 10^{-21}$ eV at 95 % CL. Adding higher-resolution Lyman-$\alpha$
spectra extends the exclusion range up to $2.9\times 10^{-21}$ eV. This
provides a significant constraint on FDM models tailored to solve the
"small-scale problems" of $\Lambda$CDM. | astro-ph_CO |
Redshift-weighted constraints on primordial non-Gaussianity from the
clustering of the eBOSS DR14 quasars in Fourier space: We present constraints on local primordial non-Gaussianity (PNG),
parametrized through $f^{\rm loc}_{\rm NL}$, using the Sloan Digital Sky Survey
IV extended Baryon Oscillation Spectroscopic Survey Data Release 14 quasar
sample. We measure and analyze the anisotropic clustering of the quasars in
Fourier space, testing for the scale-dependent bias introduced by primordial
non-Gaussianity on large scales. We derive and employ a power spectrum
estimator using optimal weights that account for the redshift evolution of the
PNG signal. We find constraints of $-51<f^{\rm loc}_{\rm NL}<21$ at 95%
confidence level. These are amont the tightest constraints from Large Scale
Structure (LSS) data. Our redshift weighting improves the error bar by 15% in
comparison to the unweighted case. If quasars have lower response to PNG, the
constraint degrades to $-81<f^{\rm loc}_{\rm NL}<26$, with a 40% improvement
over the standard approach. We forecast that the full eBOSS dataset could reach
$\sigma_{f^{\rm loc}_{\rm NL}}\simeq 5\text{-}8$ using optimal methods and full
range of scales. | astro-ph_CO |
Ultra-steep spectrum emission in the merging galaxy cluster Abell 1914: A number of radio observations have revealed the presence of large
synchrotron-emitting sources associated with the intra-cluster medium. There is
strong observational evidence that the emitting particles have been
(re-)accelerated by shocks and turbulence generated during merger events. The
particles that are accelerated are thought to have higher initial energies than
those in the thermal pool but the origin of such mildly relativistic particles
remains uncertain and needs to be further investigated. The galaxy cluster
Abell 1914 is a massive galaxy cluster in which X-ray observations show clear
evidence of merging activity. We carried out radio observations of this cluster
with the LOw Frequency ARay (LOFAR) at 150 MHz and the Giant Metrewave Radio
Telescope (GMRT) at 610 MHz. We also analysed Very Large Array (VLA) 1.4 GHz
data, archival GMRT 325 MHz data, CFHT weak lensing data and Chandra
observations. Our analysis shows that the ultra-steep spectrum source (4C38.39;
$\alpha \lesssim -2$), previously thought to be part of a radio halo, is a
distinct source with properties that are consistent with revived fossil plasma
sources. Finally, we detect some diffuse emission to the west of the source
4C38.39 that could belong to a radio halo. | astro-ph_CO |
[CII] and 12CO(1-0) Emission Maps in HLSJ091828.6+514223: A Strongly
Lensed Interacting System at z=5.24: We present Submillimeter Array (SMA) [CII] 158um and Jansky Very Large Array
(JVLA) $^{12}$CO(1-0) line emission maps for the bright, lensed, submillimeter
source at $z=5.2430$ behind Abell 773: HLSJ091828.6+514223 (HLS0918). We
combine these measurements with previously reported line profiles, including
multiple $^{12}$CO rotational transitions, [CI], water and [NII], providing
some of the best constraints on the properties of the interstellar medium (ISM)
in a galaxy at $z>5$. HLS0918 has a total far-infrared (FIR) luminosity
L_FIR(8-1000um) = (1.6$\pm$0.1)x10^14 L_sun/mu, where the total magnification
mu_total = 8.9$\pm$1.9, via a new lens model from the [CII] and continuum maps.
Despite a HyLIRG luminosity, the FIR continuum shape resembles that of a local
LIRG. We simultaneously fit all of the observed spectral line profiles, finding
four components which correspond cleanly to discrete spatial structures
identified in the maps. The two most redshifted spectral components occupy the
nucleus of a massive galaxy, with a source plane separation <1 kpc. The reddest
dominates the continuum map (de-magnified L_FIR = (1.1$\pm$0.2)x10^13 L_sun),
and excites strong water emission in both nuclear components via a powerful FIR
radiation field from the intense star formation. A third star-forming component
is most likely a region of a merging companion (dV ~ 500 km/s) exhibiting
generally similar gas properties. The bluest component originates from a
spatially distinct region, and photo-dissociation region (PDR) analysis
suggests that it is lower density, cooler and forming stars less vigorously
than the other components. Strikingly, it has very strong [NII] emission which
may suggest an ionized, molecular outflow. This comprehensive view of gas
properties and morphology in HLS0918 previews the science possible for a large
sample of high-redshift galaxies once ALMA attains full sensitivity. | astro-ph_CO |
Analyzing the 21-cm signal brightness temperature in the Universe with
inhomogeneities: We explore the 21-cm signal in our Universe containing inhomogeneous matter
distribution at considerably large scales. Employing Buchert's averaging
procedure in the context of a model of spacetime with multiple inhomogeneous
domains, we evaluate the effect of our model parameters on the observable 21-cm
signal brightness temperature. Our model parameters are constrained through the
Markov Chain Monte Carlo method using the Union 2.1 supernova Ia observational
data. We find that a significant dip in the brightness temperature compared to
the $\Lambda$CDM prediction could arise as an effect of the inhomogeneities
present in the Universe. | astro-ph_CO |
Radio Band Observations of Blazar Variability: The properties of blazar variability in the radio band are studied using the
unique combination of temporal resolution from single dish monitoring and
spatial resolution from VLBA imaging; such measurements, now available in all
four Stokes parameters, together with theoretical simulations, identify the
origin of radio band variability and probe the characteristics of the radio jet
where the broadband blazar emission originates. Outbursts in total flux density
and linear polarization in the optical-to-radio bands are attributed to shocks
propagating within the jet spine, in part based on limited modeling invoking
transverse shocks; new radiative transfer simulations allowing for shocks at
arbitrary angle to the flow direction confirm this picture by reproducing the
observed centimeter-band variations observed more generally, and are of current
interest since these shocks may play a role in the gamma-ray flaring detected
by Fermi. Recent UMRAO multifrequency Stokes V studies of bright blazars
identify the spectral variability properties of circular polarization for the
first time and demonstrate that polarity flips are relatively common.
All-Stokes data are consistent with the production of circular polarization by
linear-to-circular mode conversion in a region that is at least partially
self-absorbed. Detailed analysis of single-epoch, multifrequency, all-Stokes
VLBA observations of 3C 279 support this physical picture and are best
explained by emission from an electron-proton plasma. | astro-ph_CO |
The incidence of cool gas in ~ 1e13 Msun halos: We present the first results of an ongoing spectroscopic follow-up of close
luminous red galaxy (LRGs) and MgII {\lambda}{\lambda} 2796,2803 absorber pairs
for an initial sample of 15 photometrically selected LRGs at physical projected
separations {\rho} \le 350 kpc/h from a QSO sightline. Our moderate-resolution
spectra confirm a physical association between the cool gas (T ~ 1e4 K)
revealed by the presence of MgII absorption features and the LRG halo in five
cases. In addition, we report an empirical estimate of the maximum covering
fraction (\kappa_max) of cool gas in massive, \ge 1e13 Msun/h dark matter halos
hosting LRGs at z ~ 0.5. This study is performed using a sample of foreground
LRGs that are located at {\rho} < 400 kpc/h from a QSO sightline. The LRGs are
selected to have a robust photometric redshift \sigma_z/(1+z_ph) \approx 0.03.
We determine \kappa_max based on the incidence of MgII absorption systems that
occur within z_ph +/- 3sigma_z in the spectra of the background QSOs. Despite
the large uncertainties in z_ph, this experiment provides a conservative upper
limit to the covering fraction of cool gas in the halos of LRGs. We find that
\kappa_max \approx 0.07 at W_r(2796) \ge 1.0 A and \kappa_max \approx 0.18 at
W_r(2796) \ge 0.5 A, averaged over 400 kpc/h radius. Our study shows that while
cool gas is present in \ge 1e13 Msun/h halos, the mean covering fraction of
strong absorbers is no more than 7%. | astro-ph_CO |
Dynamical processes in galaxy centers: How does the gas get in nuclear regions to fuel black holes? How efficient is
the feedback? The different processes to cause rapid gas inflow (or outflow) in
galaxy centers are reviewed. Non axisymmetries can be created or maintained by
internal disk instabilities, or galaxy interactions. Simulations and
observations tell us that the fueling is a chaotic and intermittent process,
with different scenarios and time-scales, according to the various radial
scales across a galaxy. | astro-ph_CO |
Inflation with an extra light scalar field after Planck: Bayesian inference techniques are used to investigate situations where an
additional light scalar field is present during inflation and reheating. This
includes (but is not limited to) curvaton-type models. We design a numerical
pipeline where $\simeq 200$ inflaton setups $\times\, 10$ reheating scenarios
$= 2000$ models are implemented and we present the results for a few
prototypical potentials. We find that single-field models are remarkably robust
under the introduction of light scalar degrees of freedom. Models that are
ruled out at the single-field level are not improved in general, because good
values of the spectral index and the tensor-to-scalar ratio can only be
obtained for very fine-tuned values of the extra field parameters and/or when
large non-Gaussianities are produced. The only exception is quartic large-field
inflation, so that the best models after Planck are of two kinds: plateau
potentials, regardless of whether an extra field is added or not, and quartic
large-field inflation with an extra light scalar field, in some specific
reheating scenarios. Using Bayesian complexity, we also find that more
parameters are constrained for the models we study than for their single-field
versions. This is because the added parameters not only contribute to the
reheating kinematics but also to the cosmological perturbations themselves, to
which the added field contributes. The interplay between these two effects lead
to a suppression of degeneracies that is responsible for having more
constrained parameters. | astro-ph_CO |
Semi-blind Bayesian inference of CMB map and power spectrum: We present a new blind formulation of the Cosmic Microwave Background (CMB)
inference problem. The approach relies on a phenomenological model of the
multi-frequency microwave sky without the need for physical models of the
individual components. For all-sky and high resolution data, it unifies parts
of the analysis that have previously been treated separately, such as component
separation and power spectrum inference. We describe an efficient sampling
scheme that fully explores the component separation uncertainties on the
inferred CMB products such as maps and/or power spectra. External information
about individual components can be incorporated as a prior giving a flexible
way to progressively and continuously introduce physical component separation
from a maximally blind approach. We connect our Bayesian formalism to existing
approaches such as Commander, SMICA and ILC, and discuss possible future
extensions. | astro-ph_CO |
The Entrainment-Limited Evolution of FR II Sources: Maximum Sizes and A
Possible Connection to FR Is: We construct a simple theoretical model to investigate how entrainment
gradually erodes high-speed FR II jets. This process is described by embedding
a mixing-layer model developed originally to describe FR I objects in a
self-similar model for the lobe structure of classical FR II sources. Following
the classical FR II models, we assume that the lobe is dominated by the
particles injected from the central jet. The entrainment produces a boundary
shear layer which acts at the interface between the dense central jet and the
less denser surrounding lobe, and the associated erosion of the jet places
interesting limits on the maximum size of FR II sources. The model shows that
this limit depends mainly on the initial bulk velocity of the relativistic jet
triggered. The bulk velocities of FR IIs suggested by our model are in good
agreement with that obtained from direct pc-scale observations on ordinary
radio galaxies and quasars. Finally, we discuss how FR IIs may evolve into FR
Is upon reaching their maximum, entrainment-limited sizes. | astro-ph_CO |
The spectral index of polarized diffuse Galactic emission between 30 and
44 GHz: We present an estimate of the polarized spectral index between the Planck 30
and 44 GHz surveys in $3.7^\circ$ pixels across the entire sky. We use an
objective reference prior that maximises the impact of the data on the
posterior and multiply this by a maximum entropy prior that includes
information from observations in total intensity by assuming a polarization
fraction. Our parametrization of the problem allows the reference prior to be
easily determined and also provides a natural method of including prior
information. The spectral index map is consistent with those found by others
between surveys at similar frequencies. Across the entire sky we find an
average temperature spectral index of $-2.99\pm0.03(\pm1.12)$ where the first
error term is the statistical uncertainty on the mean and the second error term
(in parentheses) is the extra intrinsic scatter in the data. We use a
clustering algorithm to identify pixels with actual detections of the spectral
index. The average spectral index in these pixels is $-3.12\pm0.03(\pm0.64)$
and then when also excluding pixels within $10^\circ$ of the Galactic plane we
find $-2.92(\pm0.03)$. We find a statistically significant difference between
the average spectral indices in the North and South Fermi bubbles. Only
including pixels identified by the clustering algorithm, the average spectral
index in the southern bubble is $-3.00\pm0.05(\pm0.35)$, which is similar to
the average across the whole sky. In the northern bubble we find a much harder
average spectral index of $-2.36\pm0.09(\pm0.63)$. Therefore, if the bubbles
are features in microwave polarization they are not symmetric about the
Galactic plane. | astro-ph_CO |
Microwave Spectro-Polarimetry of Matter and Radiation across Space and
Time: This paper discusses the science case for a sensitive spectro-polarimetric
survey of the microwave sky. Such a survey would provide a tomographic and
dynamic census of the three-dimensional distribution of hot gas, velocity
flows, early metals, dust, and mass distribution in the entire Hubble volume,
exploit CMB temperature and polarisation anisotropies down to fundamental
limits, and track energy injection and absorption into the radiation background
across cosmic times by measuring spectral distortions of the CMB blackbody
emission. In addition to its exceptional capability for cosmology and
fundamental physics, such a survey would provide an unprecedented view of
microwave emissions at sub-arcminute to few-arcminute angular resolution in
hundreds of frequency channels, a data set that would be of immense legacy
value for many branches of astrophysics. We propose that this survey be
carried-out with a large space mission featuring a broad-band polarised imager
and a moderate resolution spectro-imager at the focus of a 3.5m aperture
telescope actively cooled to about 8K, complemented with absolutely-calibrated
Fourier Transform Spectrometer modules observing at degree-scale angular
resolution in the 10-2000 GHz frequency range. We propose two observing modes:
a survey mode to map the entire sky as well as a few selected wide fields, and
an observatory mode for deeper observations of regions of specific interest. | astro-ph_CO |
Prospects for Detecting Dark Matter Halo Substructure with Pulsar Timing: One of the open questions of modern cosmology is the nature and properties of
the Dark Matter halo and its substructures. In this work we study the
gravitational effect of dark matter substructures on pulsar timing
observations. Since millisecond pulsars are stable and accurate emitters, they
have been proposed as plausible astrophysical tools to probe the gravitational
effects of dark matter structures. We study this effect on pulsar timing
through Shapiro time delay (or Integrated Sachs-Wolfe (ISW) effect) and Doppler
effects statistically, showing that the latter dominates the signal. For this
task, we relate the power spectrum of pulsar frequency change to the matter
power spectrum on small scales, which we compute using the stable clustering
hypothesis. We compare this power spectrum with the reach of current and future
observations of pulsar timing designed for gravitational wave (GW) detection.
Our results show that while current observations are unable to detect these
signals, the sensitivity of the upcoming Square Kilometer Array (SKA) is only a
factor of few weaker than our optimistic predictions. | astro-ph_CO |
The GALEX Arecibo SDSS Survey V: The Relation between the HI Content of
Galaxies and Metal Enrichment at their Outskirts: We have obtained long-slit spectra of 174 star-forming galaxies with stellar
masses greater than 10^10 M_\odot from the GALEX Arecibo SDSS (GASS) survey.
These galaxies have both HI and H_2 mass measurements. The average metallicity
profile is strikingly flat out to R_90, the radius enclosing 90% of the r-band
light. Metallicity profiles which decline steadily with radius are found
primarily for galaxies in our sample with low stellar mass (Log(M_*)<10.2),
concentration, and/or mean stellar mass density. Beyond ~R_90, however, around
10 percent of the galaxies in our sample exhibit a sharp downturn in
metallicity. Remarkably, we find that the magnitude of the outer metallicity
drop is well correlated with the total HI content of the galaxy (measured as
f_HI=M_HI/M_*). We examine the radial profiles of stellar population ages and
star formation rate densities, and conclude that the galaxies with largest
outer metallicity drops are actively growing their stellar disks, with mass
doubling times across the whole disk only one third as long as a typical GASS
galaxy. We also describe a correlation between local stellar mass density and
metallicity, which is valid across all galaxies in our sample. We argue that
much of the recent stellar mass growth at the edges of these galaxies can be
linked to the accretion or radial transport of relatively pristine gas from
beyond the galaxies' stellar disks. | astro-ph_CO |
VIPERS: An Unprecedented View of Galaxies and Large-Scale Structure
Halfway Back in the Life of the Universe: The VIMOS Public Extragalactic Redshift Survey (VIPERS) is an ongoing ESO
Large Programme to map in detail the large-scale distribution of galaxies at
0.5 < z <1.2. With a combination of volume and sampling density that is unique
for these redshifts, it focuses on measuring galaxy clustering and related
cosmological quantities as part of the grand challenge of understanding the
origin of cosmic acceleration. VIPERS has also been designed to guarantee a
broader legacy, allowing detailed investigations of the properties and
evolutionary trends of z~1 galaxies. The survey strategy exploits the specific
advantages of the VIMOS spectrograph at the VLT, aiming at a final sample of
nearly 100,000 galaxy redshifts to iAB = 22.5 mag, which represents the largest
redshift survey ever performed with ESO telescopes. In this introductory
article we describe the survey construction, together with early results based
on a first sample of ~55,000 galaxies. | astro-ph_CO |
Dust-to-metal ratios in damped Lyman-alpha absorbers: Fresh clues to the
origins of dust and optical extinction towards gamma-ray bursts: Motivated by the anomalous dust-to-metal ratios derived in the literature for
gamma-ray burst (GRB) damped Lyman-alpha absorbers (DLAs), we measure these
ratios using the dust-depletion pattern observed in UV/optical afterglow
spectra associated with the ISM at the GRB host-galaxy redshifts. Our sample
consists of 20 GRB absorbers and a comparison sample of 72 QSO-DLAs with
redshift 1.2 < z < 4.0 and down to Z = 0.002 Z_Sol metallicities. The
dust-to-metal ratio in QSO- and GRB-DLAs increases both with metallicity and
metal column density, spanning ~10--110% of the Galactic value and pointing to
a non universal dust-to-metal ratio. The low values of dust-to-metal ratio
suggest that low-metallicity systems have lower dust fractions than typical
spiral galaxies and perhaps that the dust in these systems is produced
inefficiently, i.e. by grain growth in the low-metallicity regime with
negligible contribution from supernovae (SNe) and asymptotic giant branch (AGB)
stars. On the other hand, some GRB- and QSO-DLAs show high dust-to-metal ratio
values out to z ~ 4, requiring rapid dust production, such as in SN ejecta, but
also in AGB winds and via grain growth for the highest metallicity systems.
GRB-DLAs overall follow the dust-to-metal-ratio properties of QSO-DLAs, GRBs
probing up to larger column and volume densities. For comparison, the
dust-to-metal ratio that we derive for the SMC and LMC are ~82--100% and ~98%
of the Galactic value, respectively. The literature dust-to-metal ratio of the
low-metallicity galaxy I Zw 18 (< 37%) is consistent with the distribution that
we find. The dust extinction Av increases steeply with the column density of
iron in dust, N(Fe)dust, calculated from relative metal abundances, confirming
that dust extinction is mostly occurring in the host galaxy ISM. Most GRB-DLAs
display log N(Fe)dust > 14.7, above which several QSO-DLAs reveal H2
(abridged). | astro-ph_CO |
Clusters, Groups, and Filaments in the Chandra Deep Field-South up to
Redshift 1: We present a comprehensive structure detection analysis of the 0.3 square
degree area of the MUSYC-ACES field which covers the Chandra Deep Field-South
(CDFS). Using a density-based clustering algorithm on the MUSYC and ACES
photometric and spectroscopic catalogues we find 62 over-dense regions up to
redshifts of 1, including, clusters, groups and filaments. All structures are
confirmed using the DBSCAN method, including the detection of nine structures
previously reported in the literature. We present a catalogue of all structures
present including their central position, mean redshift, velocity dispersions,
and classification based on their morphological and spectroscopic
distributions. In particular we find 13 galaxy clusters and 6 large
groups/small clusters. Comparison of these massive structures with published
XMM-Newton imaging (where available) shows that $80\%$ of these structures are
associated with diffuse, soft-band (0.4 - 1 keV) X-ray emission including
$90\%$ of all objects classified as clusters. The presence of soft-band X-ray
emission in these massive structures (${\rm M}_{200} \geq 4.9 \times 10^{13}
{\rm M}_{\odot}$) provides a strong independent confirmation of our methodology
and classification scheme. Nearly $60\%$ of the clusters, groups and filaments
are detected in the known enhanced density regions of the CDFS at
$z\simeq0.13$, $z\simeq0.52$, $0.68$, and $0.73$. Additionally, all of the
clusters, bar the most distant, are found in these over-dense redshifts
regions. Many of the clusters and groups exhibit signs of on-going formation
seen in their velocity distributions, position within the detected cosmic web
and in one case through the presence of tidally disrupted central galaxies
exhibiting trails of stars. These results all provide strong support for
hierarchical structure formation up to redshifts of 1. | astro-ph_CO |
Symbolic Implementation of Extensions of the $\texttt{PyCosmo}$
Boltzmann Solver: $\texttt{PyCosmo}$ is a Python-based framework for the fast computation of
cosmological model predictions. One of its core features is the symbolic
representation of the Einstein-Boltzmann system of equations. Efficient
$\texttt{C/C++}$ code is generated from the $\texttt{SymPy}$ symbolic
expressions making use of the $\texttt{sympy2c}$ package. This enables easy
extensions of the equation system for the implementation of new cosmological
models. We illustrate this with three extensions of the $\texttt{PyCosmo}$
Boltzmann solver to include a dark energy component with a constant equation of
state, massive neutrinos and a radiation streaming approximation. We describe
the $\texttt{PyCosmo}$ framework, highlighting new features, and the symbolic
implementation of the new models. We compare the $\texttt{PyCosmo}$ predictions
for the $\Lambda$CDM model extensions with $\texttt{CLASS}$, both in terms of
accuracy and computational speed. We find a good agreement, to better than 0.1%
when using high-precision settings and a comparable computational speed. Links
to the Python Package Index (PyPI) page of the code release and to the PyCosmo
Hub, an online platform where the package is installed, are available at:
https://cosmology.ethz.ch/research/software-lab/PyCosmo.html. | astro-ph_CO |
Reconstructing Redshift Distributions with Cross-Correlations: Tests and
an Optimized Recipe: Many of the cosmological tests to be performed by planned dark energy
experiments will require extremely well-characterized photometric redshift
measurements. Current estimates are that the true mean redshift of the objects
in each photo-z bin must be known to better than 0.002(1+z) if errors in
cosmological measurements are not to be degraded. A conventional approach is to
calibrate these photometric redshifts with large sets of spectroscopic
redshifts. However, at the depths probed by Stage III surveys (such as DES),
let alone Stage IV (LSST, JDEM, Euclid), existing large redshift samples have
all been highly (25-60%) incomplete. A powerful alternative approach is to
exploit the clustering of galaxies to perform photometric redshift
calibrations. Measuring the two-point angular cross-correlation between objects
in some photometric redshift bin and objects with known spectroscopic redshift
allows the true redshift distribution of a photometric sample to be
reconstructed in detail, even if it includes objects too faint for spectroscopy
or if spectroscopic samples are highly incomplete. We test this technique using
mock DEEP2 Galaxy Redshift survey light cones constructed from the Millennium
Simulation semi-analytic galaxy catalogs. From this realistic test, we find
that the true redshift distribution of a photometric sample can, in fact, be
determined accurately with cross-correlation techniques. We also compare the
empirical error in the reconstruction of redshift distributions to previous
analytic predictions, finding that additional components must be included in
error budgets to match the simulation results. We conclude by presenting a
step-by-step, optimized recipe for reconstructing redshift distributions using
standard correlation measurements. | astro-ph_CO |
On approximations of the redshift-space bispectrum and power spectrum
multipoles covariance matrix: We investigate, in dark matter and galaxy mocks, the effects of approximating
the galaxy power spectrum-bispectrum estimated covariance as a diagonal matrix,
for an analysis that aligns with the specifications of recent and upcoming
galaxy surveys. We find that, for a joint power spectrum and bispectrum
data-vector, with corresponding $k$-ranges of $0.02<k\,[h{\rm Mpc}^{-1}]<0.15$
and $0.02<k\,[h{\rm Mpc}^{-1}]<0.12$ each, the diagonal covariance
approximation recovers $\sim 10\%$ larger error-bars on the parameters
$\{\sigma_8,f,\alpha_\parallel,\alpha_\bot\}$ with respect to the full
covariance case, while still underestimating the corresponding true errors on
the recovered parameters by $\sim 10\%$. This is caused by the diagonal
approximations weighting the elements of the data-vector in a sub-optimal way,
resulting in a less efficient estimator, with poor coverage properties, than
the maximum likelihood estimator featuring the full covariance matrix. We
further investigate intermediate approximations to the full covariance matrix,
with up to $\sim 80\%$ of the matrix elements being zero, which could be
advantageous for theoretical and hybrid approaches. We expect these results to
be qualitatively insensitive to variations of the total cosmological volume,
depending primarily on the bin size and shot-noise, thus making them
particularly significant for present and future galaxy surveys. | astro-ph_CO |
The Efficacy of Galaxy Shape Parameters in Photometric Redshift
Estimation: A Neural Network Approach: We present a determination of the effects of including galaxy morphological
parameters in photometric redshift estimation with an artificial neural network
method. Neural networks, which recognize patterns in the information content of
data in an unbiased way, can be a useful estimator of the additional
information contained in extra parameters, such as those describing morphology,
if the input data are treated on an equal footing. We use imaging and five band
photometric magnitudes from the All-wavelength Extended Groth Strip
International Survey. It is shown that certain principal components of the
morphology information are correlated with galaxy type. However, we find that
for the data used the inclusion of morphological information does not have a
statistically significant benefit for photometric redshift estimation with the
techniques employed here. The inclusion of these parameters may result in a
trade-off between extra information and additional noise, with the additional
noise becoming more dominant as more parameters are added. | astro-ph_CO |
Effect of low mass dark matter particles on the Sun: We study the effect of dark matter (DM) particles in the Sun, focusing in
particular on the possible reduction of the solar neutrinos flux due to the
energy carried away by DM particles from the innermost regions of the Sun, and
to the consequent reduction of the temperature of the solar core. We find that
in the very low-mass range between 4 and 10 GeV, recently advocated to explain
the findings of the DAMA and CoGent experiments, the effects on neutrino fluxes
are detectable only for DM models with very small, or vanishing,
self-annihilation cross section, such as the so-called asymmetric DM models,
and we study the combination of DM masses and Spin Dependent cross sections
which can be excluded with current solar neutrino data. Finally, we revisit the
recent claim that DM models with large self-interacting cross sections can lead
to a modification of the position of the convective zone, alleviating or
solving the solar composition problem. We show that when the `geometric' upper
limit on the capture rate is correctly taken into account, the effects of DM
are reduced by orders of magnitude, and the position of the convective zone
remains unchanged. | astro-ph_CO |
Forecasting Constraints on the Evolution of the Hubble Parameter and the
Growth Function by Future Weak Lensing Surveys: The cosmological information encapsulated within a weak lensing signal can be
accessed via the power spectrum of the so called convergence. We use the Fisher
information matrix formalism with the convergence power spectrum as the
observable to predict how future weak lensing surveys will constrain the
expansion rate and the growth function as functions of redshift without using
any specific model to parameterize these two quantities. To do this, we divide
redshift space into bins and linearly interpolate the functions with the
centers of the redshift bins as sampling points, using a fiducial set of
parameters. At the same time, we use these redshift bins for power spectrum
tomography, where we analyze not only the power spectrum in each bin but also
their cross-correlation in order to maximize the extracted information. We find
that a small number of bins with the given photometric redshift mea- surement
precision is sufficient to access most of the information content and that the
projected constraints are comparable to current constraints from X-ray cluster
growth data. This way, the weak lensing data alone might be able to rule out
some modified gravity theories only at the 2{\sigma} level, but when including
priors from surveys of the cosmic microwave background radiation this would
improve to a 3{\sigma} level. | astro-ph_CO |
Relativistic Electron Scattering and Big Bang Nucleosynthesis: This paper is superseded by Arxiv:1911.07334. Big-bang nucleosynthesis (BBN)
is a valuable tool to constrain the physics of the early universe and is the
only probe of the radiation-dominated epoch. A fundamental assumption in BBN is
that the nuclear velocity distributions obey Maxwell-Boltzmann statistics as
they do in stars. In this letter, however, we point out that there is a
fundamental difference between stellar reaction rates and BBN reaction rates.
Specifically, the BBN epoch is characterized by a dilute baryon plasma for
which the velocity distribution of nuclei is mainly determined by the dominant
Coulomb scattering with mildly relativistic electrons. This modifies the
nuclear velocity distributions and significantly alters the thermonuclear
reaction rates, and hence, the light-element abundances. We show that this
novel result alters all previous calculations of light-element abundances from
BBN, and indeed exacerbates the discrepancies between BBN and inferred
primordial light-element abundances possibly suggesting the need for new
physics in the early universe. | astro-ph_CO |
Recovery of 21 cm intensity maps with sparse component separation: 21 cm intensity mapping has emerged as a promising technique to map the
large-scale structure of the Universe. However, the presence of foregrounds
with amplitudes orders of magnitude larger than the cosmological signal
constitutes a critical challenge. Here, we test the sparsity-based algorithm
Generalised Morphological Component Analysis (GMCA) as a blind component
separation technique for this class of experiments. We test the GMCA
performance against realistic full-sky mock temperature maps that include,
besides astrophysical foregrounds, also a fraction of the polarized part of the
signal leaked into the unpolarized one, a very troublesome foreground to
subtract, usually referred to as polarization leakage. To our knowledge, this
is the first time the removal of such component is performed with no prior
assumption. We assess the success of the cleaning by comparing the true and
recovered power spectra, in the angular and radial directions. In the best
scenario looked at, GMCA is able to recover the input angular (radial) power
spectrum with an average bias of $\sim 5\%$ for $\ell>25$ ($20 - 30 \%$ for
$k_{\parallel} \gtrsim 0.02 \,h^{-1}$Mpc), in the presence of polarization
leakage. Our results are robust also when up to $40\%$ of channels are missing,
mimicking a Radio Frequency Interference (RFI) flagging of the data. Having
quantified the notable effect of polarisation leakage on our results, in
perspective we advocate the use of more realistic simulations when testing 21
cm intensity mapping capabilities. | astro-ph_CO |
Orthogonal BipoSH measures : Scrutinizing sources of isotropy violation: The two point correlation function of the CMB temperature anisotropies is
generally assumed to be statistically isotropic (SI). Deviations from this
assumption could be traced to physical or observational artefacts and
systematic effects. Measurement of non-vanishing power in the BipoSH spectra is
a standard statistical technique to search for isotropy violations. Although
this is a neat tool allowing a blind search for SI violations in the CMB sky,
it is not easy to discern the cause of isotropy violation using this measure.
In this article, we propose a novel technique of constructing orthogonal BipoSH
estimators, which can be used to discern between models of isotropy violation. | astro-ph_CO |
Dark energy and dark matter perturbations in singular universes: We discuss the evolution of density perturbations of dark matter and dark
energy in cosmological models which admit future singularities in a finite
time. Up to now geometrical tests of the evolution of the universe do not
differentiate between singular universes and $\Lambda$CDM scenario. We solve
perturbation equations using the gauge invariant formalism. The analysis shows
that the detailed reconstruction of the evolution of perturbations within
singular cosmologies, in the dark sector, exhibit important differences between
the singular universes models and the $\Lambda$CDM cosmology. This is
encouraging for further examination and gives hope for discriminating between
those models with future galaxy weak lensing experiments like the Dark Energy
Survey (DES) and Euclid or CMB observations like PRISM and CoRE. | astro-ph_CO |
Turbulent formation of protogalaxies at the plasma to gas transition: The standard model of gravitational structure formation is based on the Jeans
1902 acoustic theory, neglecting crucial effects of viscosity, turbulence and
diffusion. A Jeans length scale L_J emerges that exceeds the scale of causal
connection ct during the plasma epoch. Photon-viscous forces initially dominate
all others including gravity. The first structures formed were at density
minima by fragmentation when the viscous-gravitional scale L_SV matched ct at
30,000 years to produce protosupercluster voids and protosuperclusters. Weak
turbulence produced at expanding void boundaries guides the morphology of
smaller fragments down to protogalaxy size just before transition to gas at
300,000 years. The observed 10^20 meter size of protogalaxies reflects the
plasma Kolmogorov scale with Nomura linear and spiral morphology. On transition
to gas the kinematic viscosity decreases so the protogalaxies fragment into
Jeans scale clouds, each with a trillion earth-mass planets. The planets form
stars near the cores of the protogalaxies. High resolution images of planetary
nebula and supernova remnants reveal thousands of frozen hydrogen-helium dark
matter planets. Galaxy mergers show frictional trails of young globular
clusters formed in place, proving that dark matter halos of galaxies consist of
dark matter planets in metastable clumps. | astro-ph_CO |
Redshifted 21-cm bispectrum II: Impact of the spin temperature
fluctuations and redshift space distortions on the signal from the Cosmic
Dawn: We present a study of the 21-cm signal bispectrum (which quantifies the
non-Gaussianity in the signal) from the Cosmic Dawn (CD). For our analysis, we
have simulated the 21-cm signal using radiative transfer code GRIZZLY, while
considering two types of sources (mini-QSOs and HMXBs) for Ly$\alpha$ coupling
and the X-ray heating of the IGM. Using this simulated signal, we have, for the
first time, estimated the CD 21-cm bispectra for all unique $k$-triangles and
for a range of $k$ modes. We observe that the redshift evolution of the
bispectra magnitude and sign follow a generic trend for both source models.
However, the redshifts at which the bispectra magnitude reach their maximum and
minimum values and show their sign reversal depends on the source model. When
the Ly$\alpha$ coupling and the X-ray heating of the IGM occur simultaneously,
we observe two consecutive sign reversals in the bispectra for small
$k$-triangles (irrespective of the source models). One arising at the beginning
of the IGM heating and the other at the end of Ly$\alpha$ coupling saturation.
This feature can be used in principle to constrain the CD history and/or to
identify the specific CD scenarios. We also quantify the impact of the spin
temperature ($T_{\rm S}$) fluctuations on the bispectra. We find that $T_{\rm
S}$ fluctuations have maximum impact on the bispectra magnitude for small
$k$-triangles and at the stage when Ly$\alpha$ coupling reaches saturation.
Furthermore, we are also the first to quantify the impact of redshift space
distortions (RSD), on the CD bispectra. We find that the impact of RSD on the
CD 21-cm bispectra is significant ($> 20\%$) and the level depends on the
stages of the CD and the $k$-triangles for which the bispectra are being
estimated. | astro-ph_CO |
Magnetic fields from cosmological bulk flows: We explore the possibility that matter bulk flows could generate the required
vorticity in the electron-proton-photon plasma to source cosmic magnetic fields
through the Harrison mechanism. We analyze the coupled set of perturbed Maxwell
and Boltzmann equations for a plasma in which the matter and radiation
components exhibit relative bulk motions at the background level. We find that,
to first order in cosmological perturbations, bulk flows with velocities
compatible with current Planck limits ($\beta<8.5\times 10^{-4}$ at $95\%$ CL)
could generate magnetic fields with an amplitude $10^{-21}$ G on 10 kpc
comoving scales at the time of completed galaxy formation which could be
sufficient to seed a galactic dynamo mechanism. | astro-ph_CO |
Signatures of Modified Gravity on the 21-cm Power Spectrum at
Reionisation: Scalar modifications of gravity have an impact on the growth of structure.
Baryon and Cold Dark Matter (CDM) perturbations grow anomalously for scales
within the Compton wavelength of the scalar field. In the late time Universe
when reionisation occurs, the spectrum of the 21cm brightness temperature is
thus affected. We study this effect for chameleon-f(R) models, dilatons and
symmetrons. Although the f(R) models are more tightly constrained by solar
system bounds, and effects on dilaton models are negligible, we find that
symmetrons where the phase transition occurs before z_* ~ 12 will be detectable
for a scalar field range as low as 5 kpc. For all these models, the detection
prospects of modified gravity effects are higher when considering modes
parallel to the line of sight where very small scales can be probed. The study
of the 21 cm spectrum thus offers a complementary approach to testing modified
gravity with large scale structure surveys. Short scales, which would be highly
non-linear in the very late time Universe when structure forms and where
modified gravity effects are screened, appear in the linear spectrum of 21 cm
physics, hence deviating from General Relativity in a maximal way. | astro-ph_CO |
$γ$ gravity: Steepness control: We investigate a simple generalization of the metric exponential $f(R)$
gravity theory that is cosmologically viable and compatible with solar system
tests of gravity. We show that, as compared to other viable $f(R)$ theories,
its steep dependence on the Ricci scalar $R$ facilitates agreement with
structure constraints, opening the possibility of $f(R)$ models with
equation-of-state parameter that could be differentiated from a cosmological
constant ($w_{de}=-1$) with future surveys at both background and perturbative
levels. | astro-ph_CO |
Turnaround radius in $Λ$CDM, and dark matter cosmologies II: the
role of dynamical friction: This paper is an extension of the paper by Del Popolo, Chan, and Mota (2020)
to take account the effect of dynamical friction. We show how dynamical
friction changes the threshold of collapse, $\delta_c$, and the turn-around
radius, $R_t$. We find numerically the relationship between the turnaround
radius, $R_{\rm t}$, and mass, $M_{\rm t}$, in $\Lambda$CDM, in dark energy
scenarios, and in a $f(R)$ modified gravity model. Dynamical friction gives
rise to a $R_{\rm t}-M_{\rm t}$ relation differing from that of the standard
spherical collapse. In particular, dynamical friction amplifies the effect of
shear, and vorticity already studied in Del Popolo, Chan, and Mota (2020). A
comparison of the $R_{\rm t}-M_{\rm t}$ relationship for the $\Lambda$CDM, and
those for the dark energy, and modified gravity models shows, that the $R_{\rm
t}-M_{\rm t}$ relationship of the $\Lambda$CDM is similar to that of the dark
energy models, and small differences are seen when comparing with the $f(R)$
models. The effect of shear, rotation, and dynamical friction is particularly
evident at galactic scales, giving rise to a difference between the $R_{\rm
t}-M_{\rm t}$ relation of the standard spherical collapse of the order of
$\simeq 60\%$. Finally, we show how the new values of the $R_{\rm t}-M_{\rm t}$
influence the constraints to the $w$ parameter of the equation of state. | astro-ph_CO |
Filament Hunting: Integrated HI 21cm Emission From Filaments Inferred by
Galaxy Surveys: Large scale filaments, with lengths that can reach tens of Mpc, are the most
prominent features in the cosmic web. These filaments have only been observed
indirectly through the positions of galaxies in large galaxy surveys or through
absorption features in the spectra of high redshift sources. In this study we
propose to go one step further and directly detect intergalactic medium
filaments through their emission in the HI 21cm line. We make use of high
resolution cosmological simulations to estimate the intensity of this emission
in low redshift filaments and use it to make predictions for the direct
detectability of specific filaments previously inferred from galaxy surveys, in
particular the Sloan Digital Sky Survey. Given the expected signal of these
filaments our study shows that HI emission from large filaments can be observed
by current and next generation radio telescopes. We estimate that gas in
filaments of length $l \gtrsim$ 15 $h^{-1}$Mpc with relatively small
inclinations to the line of sight ($\lesssim 10^\circ$) can be observed in
$\sim40-100$ hours with telescopes such as GMRT or EVLA, potentially providing
large improvements over our knowledge of the astrophysical properties of these
filaments. Due to their large field of view and sufficiently long integration
times, upcoming HI surveys with the Apertif and ASKAP instruments will be able
to detect large filaments independently of their orientation and curvature.
Furthermore, our estimates indicate that a more powerful future radio telescope
like SKA-2 can be used to map most of these filaments, which will allow them to
be used as a strong cosmological probe. | astro-ph_CO |
RXJ 0921+4529: a binary quasar or gravitational lens?: We report the new spectroscopic observations of the gravitational lens RXJ
021+4529 with the multi-mode focal reducer SCORPIO of the SAO RAS 6-m
telescope. The new spectral observations were compared with the previously
observed spectra of components A and B of RXJ 0921+4529, i.e. the same
components observed in different epochs. We found a significant difference in
the spectrum between the components that cannot be explained with microlensing
and/or spectral variation. We conclude that RXJ 0921+4529 is a binary quasar
system, where redshifts of quasars A and B are 1.6535 +/- 0.0005 and 1.6625 +/-
0.0015, respectively. | astro-ph_CO |
The contribution of star-forming galaxies to the cosmic radio background: Recent measurements of the temperature of the sky in the radio band, combined
with literature data, have convincingly shown the existence of a cosmic radio
background with an amplitude of $\sim 1$ K at 1 GHz and a spectral energy
distribution that is well described by a power law with index $\alpha \simeq
-0.6$. The origin of this signal remains elusive, and it has been speculated
that it could be dominated by the contribution of star-forming galaxies at high
redshift \change{if the far infrared-radio correlation $q(z)$ evolved} in time.
\change{We fit observational data from several different experiments by the
relation $q(z) \simeq q_0 - \beta \log(1+z)$ with $q_0 = 2.783 \pm 0.024$ and
$\beta = 0.705 \pm 0.081$ and estimate the total radio emission of the whole
galaxy population at any given redshift from the cosmic star formation rate
density at that redshift. It is found that} star-forming galaxies can only
account for $\sim$13 percent of the observed intensity of the cosmic radio
background. | astro-ph_CO |
Millennium Simulation Dark Matter Haloes: Multi-fractal and Lacunarity
Analysis with Homogeneity Transition: We investigate from the fractal viewpoint the way in which the dark matter is
grouped at z = 0 in the Millennium dark matter cosmological simulation. The
determination of the cross to homogeneity in the Millennium Simulation data is
described from the behaviour of the fractal dimension and the lacunarity. We
use the sliding window technique to calculate the fractal mass-radius
dimension, the pre-factor F and the lacunarity of this fractal relation.
Besides, we determinate the multi-fractal dimension and the lacunarity
spectrum, including their dependence with radial distance. This calculations
show a radial distance dependency of all the fractal quantities, with
heterogeneity clustering of dark matter haloes up to depths of 100 Mpc/h. The
dark matter haloes clustering in the Millennium Simulation shows a radial
distance dependency, with two regions clearly defined. The lacunarity spectrum
for values of the structure parameter q >= 1 shows regions with relative
maxima, revealing the formation of clusters and voids in the dark matter haloes
distribution. With the use of the multi-fractal dimension and the lacunarity
spectrum, the transition to homogeneity at depths between 100 Mpc/h and 120
Mpc/h for the Millennium Simulation dark matter haloes is detected. | astro-ph_CO |
The effects of peculiar velocities on the morphological properties of
large-scale structure: It is known that the large-scale structure (LSS) mapped by a galaxy redshift
survey is subject to distortions by galaxies' peculiar velocities. Besides the
signatures generated in common N-point statistics, such as the anisotropy in
the galaxy 2-point correlation function, the peculiar velocities also induce
distinct features in LSS's morphological properties, which are fully described
by four Minkowski functionals (MFs), i.e., the volume, surface area, integrated
mean curvature and Euler characteristic (or genus). In this work, by using
large suite of N-body simulations, we present and analyze these important
features in the MFs of LSS on both (quasi-)linear and non-linear scales, with a
focus on the latter. We also find the MFs can give competitive constraints on
cosmological parameters compared to the power spectrum, probablly due to the
non-linear information contained. For galaxy number density similar to the DESI
BGS galaxies, the constraint on $\sigma_8$ from the MFs with one smoothing
scale can be better by $\sim 50\%$ than from the power spectrum. These findings
are important for the cosmological applications of MFs of LSS, and probablly
open up a new avenue for studying the peculiar velocity field itself. | astro-ph_CO |
MC^2: A deeper look at ZwCl 2341.1+0000 with Bayesian galaxy clustering
and weak lensing analyses: ZwCl 2341.1+0000, a merging galaxy cluster with disturbed X-ray morphology
and widely separated ($\sim$3 Mpc) double radio relics, was thought to be an
extremely massive ($10-30 \times 10^{14} M_\odot$) and complex system with
little known about its merger history. We present JVLA 2-4 GHz observations of
the cluster, along with new spectroscopy from our Keck/DEIMOS survey, and apply
Gaussian Mixture Modeling to the three-dimensional distribution of 227
confirmed cluster galaxies. After adopting the Bayesian Information Criterion
to avoid overfitting, which we discover can bias total dynamical mass estimates
high, we find that a three-substructure model with a total dynamical mass
estimate of $9.39 \pm 0.81 \times 10^{14} M_\odot$ is favored. We also present
deep Subaru imaging and perform the first weak lensing analysis on this system,
obtaining a weak lensing mass estimate of $5.57 \pm 2.47 \times 10^{14}
M_\odot$. This is a more robust estimate because it does not depend on the
dynamical state of the system, which is disturbed due to the merger. Our
results indicate that ZwCl 2341.1+0000 is a multiple merger system comprised of
at least three substructures, with the main merger that produced the radio
relics occurring near to the plane of the sky, and a younger merger in the
North occurring closer to the line of sight. Dynamical modeling of the main
merger reproduces observed quantities (relic positions and polarizations,
subcluster separation and radial velocity difference), if the merger axis angle
of $\sim$10$^{+34}_{-6}$ degrees and the collision speed at pericenter is
$\sim$1900$^{+300}_{-200}$ km/s. | astro-ph_CO |
Extrasolar planets as a probe of modified gravity: We propose a new method to test modified gravity theories, taking advantage
of the available data on extrasolar planets. We computed the deviations from
the Kepler third law and use that to constrain gravity theories beyond General
Relativity. We investigate gravity models which incorporate three screening
mechanisms: the Chameleon, the Symmetron and the Vainshtein. We find that data
from exoplanets orbits are very sensitive to the screening mechanisms putting
strong constraints in the parameter space for the Chameleon models and the
Symmetron, complementary and competitive to other methods, like interferometers
and solar system. With the constraints on Vainshtein we are able to work beyond
the hypothesis that the crossover scale is of the same order of magnitude than
the Hubble radius $r_c \sim H_0^{-1}$, which makes the screening work
automatically, testing how strong this hypothesis is and the viability of other
scales. | astro-ph_CO |
Bayesian angular power spectrum analysis of interferometric data: We present a Bayesian angular power spectrum and signal map inference engine
which can be adapted to interferometric observations of anisotropies inthe
cosmic microwave background, 21 cm emission line mapping of galactic brightness
fluctuations, or 21 cm absorption line mapping of neutral hydrogen in the dark
ages. The method uses Gibbs sampling to generate a sampled representation of
the angular power spectrum posterior and the posterior of signal maps given a
set of measured visibilities in the uv-plane. We use a mock interferometric CMB
observation to demonstrate the validity of this method in the flat-sky
approximation when adapted to take into account arbitrary coverage of the
uv-plane, mode-mode correlations due to observations on a finite patch, and
heteroschedastic visibility errors. The computational requirements scale as
O(n_p log n_p) where n_p measures the ratio of the size of the detector array
to the inter-detector spacing, meaning that Gibbs sampling is a promising
technique for meeting the data analysis requirements of future cosmology
missions. | astro-ph_CO |
Features in single field slow-roll inflation: We compare the effects of local features (LF) and branch features (BF) of the
inflaton potential on the spectrum of primordial perturbations. We show that LF
affect the spectrum in a narrow range of scales while BF produce a step between
large and small scales with respect to the featureless spectrum. We comment on
the possibility of distinguishing between these two types of feature models
from the analysis of the Cosmic Microwave Background (CMB) radiation data.
We also show that there exists a quantitative similarity between the
primordial spectra predicted by two of the BF potentials considered. This could
lead to a degeneracy of their predicted CMB temperature spectra which could
make difficult to discriminate between the models from a CMB analysis. We
comment on the possibility that the degeneracy can be broken when higher order
terms in the perturbations are considered. In this sense non-Gaussianity may
play an important role in discerning between different inflationary models
which predict similar spectra. | astro-ph_CO |
Primordial feature constraints from BOSS+eBOSS: Understanding the universe in its pristine epoch is crucial in order to
obtain a concise comprehension of the late-time universe. Although current data
in cosmology are compatible with Gaussian primordial perturbations whose power
spectrum follows a nearly scale-invariant power law, this need not be the case
when a fundamental theoretical construction is assumed. These extended models
lead to sharp features in the primordial power spectrum, breaking its scale
invariance. In this work, we obtain combined constraints on four primordial
feature models by using the final data release of the BOSS galaxies and eBOSS
quasars. By pushing towards the fundamental mode of these surveys and using the
larger eBOSS volume, we were able to extend the feature parameter space (i.e.
the feature frequency $\omega$) by a factor of four compared to previous
analyses using BOSS. While we did not detect any significant features, previous
work showed that next-generation galaxy surveys such as DESI will improve the
sensitivity to features by a factor of 7, and will also extend the parameter
space by a factor of 2.5. | astro-ph_CO |
Morphological quenching of star formation: making early-type galaxies
red: We point out a natural mechanism for quenching of star formation in
early-type galaxies. It automatically links the color of a galaxy with its
morphology and does not require gas consumption, removal or termination of gas
supply. Given that star formation takes place in gravitationally unstable gas
disks, it can be quenched when a disk becomes stable against fragmentation to
bound clumps. This can result from the growth of a stellar spheroid, for
instance by mergers. We present the concept of morphological quenching (MQ)
using standard disk instability analysis, and demonstrate its natural
occurrence in a cosmological simulation using an efficient zoom-in technique.
We show that the transition from a stellar disk to a spheroid can be sufficient
to stabilize the gas disk, quench star formation, and turn an early-type galaxy
red and dead while gas accretion continues. The turbulence necessary for disk
stability can be stirred up by sheared perturbations within the disk in the
absence of bound star-forming clumps. While gas stripping processes are limited
to dense groups and clusters, and other quenching mechanisms like AGN feedback,
virial shock heating and gravitational heating, are limited to halos more
massive than 10^12 Mo, the MQ can explain the appearance of red ellipticals
even in less massive halos and in the field. The dense gas disks observed in
some of today's red ellipticals may be the relics of this mechanism, whereas
red galaxies with quenched gas disks are expected to be more frequent at high
redshift. | astro-ph_CO |
Probing high-redshift galaxies with Ly$α$ intensity mapping: We present a study of the cosmological Ly$\alpha$ emission signal at $z > 4$.
Our goal is to predict the power spectrum of the spatial fluctuations that
could be observed by an intensity mapping survey. The model uses the latest
data from the HST legacy fields and the abundance matching technique to
associate UV emission and dust properties with the halos, computing the
emission from the interstellar medium (ISM) of galaxies and the intergalactic
medium (IGM), including the effects of reionization, self-consistently. The
Ly$\alpha$ intensity from the diffuse IGM emission is 1.3 (2.0) times more
intense than the ISM emission at $z = 4(7)$; both components are fair tracers
of the star-forming galaxy distribution. However the power spectrum is
dominated by ISM emission on small scales ($k > 0.01 h{\rm Mpc}^{-1}$) with
shot noise being significant only above $k = 1 h{\rm Mpc}^{-1}$. At very lange
scales ($k < 0.01h{\rm Mpc}^{-1}$) diffuse IGM emission becomes important. The
comoving Ly$\alpha$ luminosity density from IGM and galaxies, $\dot \rho_{{\rm
Ly}\alpha}^{\rm IGM} = 8.73(6.51) \times 10^{40} {\rm erg}{\rm s}^{-1}{\rm
Mpc}^{-3}$ and $\dot \rho_{{\rm Ly}\alpha}^{\rm ISM} = 6.62(3.21) \times
10^{40} {\rm erg}{\rm s}^{-1}{\rm Mpc}^{-3}$ at $z = 4(7)$, is consistent with
recent SDSS determinations. We predict a power $k^3 P^{{\rm Ly}\alpha}(k,
z)/2\pi^2 = 9.76\times 10^{-4}(2.09\times 10^{-5}){\rm nW}^2{\rm m}^{-4}{\rm
sr}^{-2}$ at $z = 4(7)$ for $k = 0.1 h {\rm Mpc}^{-1}$. | astro-ph_CO |
The connection between gamma-ray emission and millimeter flares in
Fermi/LAT blazars: We compare the gamma-ray photon flux variability of northern blazars in the
Fermi/LAT First Source Catalog with 37 GHz radio flux density curves from the
Metsahovi quasar monitoring program. We find that the relationship between
simultaneous millimeter (mm) flux density and gamma-ray photon flux is
different for different types of blazars. The flux relation between the two
bands is positively correlated for quasars and does not exist for BLLacs.
Furthermore, we find that the levels of gamma-ray emission in high states
depend on the phase of the high frequency radio flare, with the brightest
gamma-ray events coinciding with the initial stages of a mm flare. The mean
observed delay from the beginning of a mm flare to the peak of the gamma-ray
emission is about 70 days, which places the average location of the gamma-ray
production at or downstream of the radio core. We discuss alternative scenarios
for the production of gamma-rays at distances of parsecs along the length the
jet. | astro-ph_CO |
On the Primordial Black Hole Mass Function for Broad Spectra: We elaborate on the mass function of primordial black holes in the case in
which the power spectrum of the curvature perturbation is broad. For the case
of a broad and flat spectrum, we argue that such a mass function is peaked at
the smallest primordial black mass which can be formed and possesses a tail
decaying like $M^{-3/2}$, where $M$ is the mass of the primordial black hole. | astro-ph_CO |
Nonsingular bouncing cosmologies in light of BICEP2: We confront various nonsingular bouncing cosmologies with the recently
released BICEP2 data and investigate the observational constraints on their
parameter space. In particular, within the context of the effective field
approach, we analyze the constraints on the matter bounce curvaton scenario
with a light scalar field, and the new matter bounce cosmology model in which
the universe successively experiences a period of matter contraction and an
ekpyrotic phase. Additionally, we consider three nonsingular bouncing
cosmologies obtained in the framework of modified gravity theories, namely the
Ho\v{r}ava-Lifshitz bounce model, the $f(T)$ bounce model, and loop quantum
cosmology. | astro-ph_CO |
The radial and azimuthal profiles of Mg II absorption around 0.5 < z <
0.9 zCOSMOS galaxies of different colors, masses and environments: We map the radial and azimuthal distribution of Mg II gas within 200 kpc
(physical) of 4000 galaxies at redshifts 0.5 < z < 0.9 using co-added spectra
of more than 5000 background galaxies at z > 1. We investigate the variation of
Mg II rest frame equivalent width as a function of the radial impact parameter
for different subsets of foreground galaxies selected in terms of their
rest-frame colors and masses. Blue galaxies have a significantly higher average
Mg II equivalent width at close galactocentric radii as compared to the red
galaxies. Amongst the blue galaxies, there is a correlation between Mg II
equivalent width and galactic stellar mass of the host galaxy. We also find
that the distribution of Mg II absorption around group galaxies is more
extended than that for non-group galaxies, and that groups as a whole have more
extended radial profiles than individual galaxies. Interestingly, these effects
can be satisfactorily modeled by a simple superposition of the absorption
profiles of individual member galaxies, assuming that these are the same as
those of non-group galaxies, suggesting that the group environment may not
significantly enhance or diminish the Mg II absorption of individual galaxies.
We show that there is a strong azimuthal dependence of the Mg II absorption
within 50 kpc of inclined disk-dominated galaxies, indicating the presence of a
strongly bipolar outflow aligned along the disk rotation axis. There is no
significant dependence of Mg II absorption on the apparent inclination angle of
disk-dominated galaxies. | astro-ph_CO |
Optical and HI properties of isolated galaxies in the 2MIG catalog. I.
General relationships: We analyze empirical relationships between the optical, near infrared, and HI
characteristics of isolated galaxies from the 2MIG Catalog covering the entire
sky. Data on morphological types, K_S-, and B-magnitudes, linear diameters, HI
masses, and rotational velocities are examined. The regression parameters,
dispersions, and correlation coefficients are calculated for pairs of these
characteristics. The resulting relationships can be used to test the
hierarchical theory of galaxy formation through numerous mergers of cold dark
matter. | astro-ph_CO |
Relativistic effects in the power spectrum of the large scale structure: The forthcoming Stage-IV experiments aim to map the large scale structure of
the Universe at high precision. The scales explored require a relativistic
description, in addition to statistical tools for their analysis. In this
thesis, we study the effects of adding relativistic and primordial
non-Gaussianity contributions to the power spectrum. We begin by reviewing the
standard cosmology, then we present the cosmological and Newtonian perturbation
theory, which are necessary mathematical tools in the computation of our main
results. Afterwards we present the main contributions to this thesis. First, we
present solutions to the Einstein equations in the long-wavelength
approximation, this allow us to obtain expressions for the relativistic density
power spectrum at second and third order, these expressions also include
contributions from primordial non-Gaussianity, in terms of the parameters
$f_{\mathrm{NL}}$ and $g_{\mathrm{NL}}$. These results are complemented with
the well known Newtonian solutions for the density contrast and are used in the
computation of the total (relativistic + Newtonian) one-loop power spectrum.
For completeness we also calculate the bispectrum at tree-level. We discuss the
possibility of these relativistic effects being detectable with the future
surveys considering different limiting values for $f_{\mathrm{NL}}$ and
$g_{\mathrm{NL}}$. Subsequently, we compute the real space galaxy power
spectrum, including relativistic and primordial non-Gaussianity effects. These
effects come from the relativistic one-loop power spectrum terms and from
factors of the non-linear bias parameter $b_{\mathrm{NL}}$. We use our
modelling to assess the ability of Stage-IV surveys to constrain primordial
non-Gaussianity. Finally, we show how this non-linear bias parameter can
effectively renormalize diverging relativistic contributions at large scales. | astro-ph_CO |
Deep Chandra observation of the galaxy cluster WARPJ1415.1+3612 at z=1:
an evolved cool-core cluster at high-redshift: Using the deepest (370 ksec) Chandra observation of a high-redshift galaxy
cluster, we perform a detailed characterization of the intra-cluster medium
(ICM) of WARPJ1415.1+3612 at z=1.03. We also explore the connection between the
ICM core properties and the radio/optical properties of the brightest cluster
galaxy (BCG). We perform a spatially resolved analysis of the ICM to obtain
temperature, metallicity and surface brightness profiles. Using the deprojected
temperature and density profiles we accurately derive the cluster mass at
different overdensities. In addition to the X-ray data, we use archival radio
VLA imaging and optical GMOS spectroscopy of the central galaxy to investigate
the feedback between the central galaxy and the ICM. The X-ray spectral
analysis shows a significant temperature drop towards the cluster center, with
a projected value of Tc = 4.6 \pm 0.4 keV, and a remarkably high central iron
abundance peak, Zc= 3.6 Zsun. The central cooling time is shorter than 0.1 Gyr
and the entropy is equal to 9.9 keV cm2. We detect a strong [OII] emission line
in the optical spectra of the BCG with an equivalent width of -25 \AA, for
which we derive a star formation rate within the range 2 - 8 Msun/yr. The VLA
data reveals a central radio source coincident with the BCG and a faint
one-sided jet-like feature with an extent of 80 kpc. The analysis presented
shows that WARPJ1415 has a well developed cool core with ICM properties similar
to those found in the local Universe. Its properties and the clear sign of
feedback activity found in the central galaxy in the optical and radio bands,
show that feedback processes are already established at z~1. In addition, the
presence of a strong metallicity peak shows that the central regions have been
promptly enriched by star formation processes in the central galaxy already at
z > 1. | astro-ph_CO |
HerMES: dust attenuation and star formation activity in UV-selected
samples from z~4 to z~1.5: We study the link between observed ultraviolet luminosity, stellar mass, and
dust attenuation within rest-frame UV-selected samples at z~ 4, 3, and 1.5. We
measure by stacking at 250, 350, and 500 um in the Herschel/SPIRE images from
the HerMES program the average infrared luminosity as a function of stellar
mass and UV luminosity. We find that dust attenuation is mostly correlated with
stellar mass. There is also a secondary dependence with UV luminosity: at a
given UV luminosity, dust attenuation increases with stellar mass, while at a
given stellar mass it decreases with UV luminosity. We provide new empirical
recipes to correct for dust attenuation given the observed UV luminosity and
the stellar mass. Our results also enable us to put new constraints on the
average relation between star formation rate and stellar mass at z~ 4, 3, and
1.5. The star formation rate-stellar mass relations are well described by power
laws (SFR~ M^0.7), with the amplitudes being similar at z~4 and z~3, and
decreasing by a factor of 4 at z~1.5 at a given stellar mass. We further
investigate the evolution with redshift of the specific star formation rate.
Our results are in the upper range of previous measurements, in particular at
z~3, and are consistent with a plateau at 3<z<4. Current model predictions
(either analytic, semi-analytic or hydrodynamic) are inconsistent with these
values, as they yield lower predictions than the observations in the redshift
range we explore. We use these results to discuss the star formation histories
of galaxies in the framework of the Main Sequence of star-forming galaxies. Our
results suggest that galaxies at high redshift (2.5<z<4) stay around 1 Gyr on
the Main Sequence. With decreasing redshift, this time increases such that z=1
Main Sequence galaxies with 10^8<M_*/Msun<10^10 stay on the Main Sequence until
z=0. | astro-ph_CO |
A nearby GRB host prototype for z~7 Lyman-break galaxies: Spitzer-IRS
and X-shooter spectroscopy of the host galaxy of GRB031203: Gamma-ray burst (GRB) host galaxies have been studied extensively in optical
photometry and spectroscopy. Here we present the first mid-infrared spectrum of
a GRB host, HG031203. It is one of the nearest GRB hosts at z=0.1055, allowing
both low and high-resolution spectroscopy with Spitzer-IRS. Medium resolution
UV-to-K-band spectroscopy with the X-shooter spectrograph on the VLT is also
presented, along with Spitzer IRAC and MIPS photometry, as well as radio and
sub-mm observations. These data allow us to construct a UV-to-radio spectral
energy distribution with almost complete spectroscopic coverage from 0.3-35
micron of a GRB host galaxy for the first time, potentially valuable as a
template for future model comparisons. The IRS spectra show strong,
high-ionisation fine structure line emission indicative of a hard radiation
field in the galaxy, suggestive of strong ongoing star-formation and a very
young stellar population. The selection of HG031203 via the presence of a GRB
suggests that it might be a useful analogue of very young star-forming galaxies
in the early universe, and hints that local BCDs may be used as more reliable
analogues of star-formation in the early universe than typical local
starbursts. We look at the current debate on the ages of the dominant stellar
populations in z~7 and z~8 galaxies in this context. The nebular line emission
is so strong in HG031203, that at z~7, it can reproduce the spectral energy
distributions of z-band dropout galaxies with elevated IRAC 3.6 and 4.5 micron
fluxes without the need to invoke a 4000A break. | astro-ph_CO |
CNN photometric redshifts in the SDSS at $r\leq 20$: We release photometric redshifts, reaching $\sim$0.7, for $\sim$14M galaxies
at $r\leq 20$ in the 11,500 deg$^2$ of the SDSS north and south galactic caps.
These estimates were inferred from a convolution neural network (CNN) trained
on $ugriz$ stamp images of galaxies labelled with a spectroscopic redshift from
the SDSS, GAMA and BOSS surveys. Representative training sets of $\sim$370k
galaxies were constructed from the much larger combined spectroscopic data to
limit biases, particularly those arising from the over-representation of
Luminous Red Galaxies. The CNN outputs a redshift classification that offers
all the benefits of a well-behaved PDF, with a width efficiently signaling
unreliable estimates due to poor photometry or stellar sources. The dispersion,
mean bias and rate of catastrophic failures of the median point estimate are of
order $\sigma_{\rm MAD}=0.014$, <$\Delta z_{\rm norm}$>$=0.0015$, $\eta(|\Delta
z_{\rm norm}|>0.05)=4\%$ on a representative test sample at $r<19.8$,
out-performing currently published estimates. The distributions in narrow
intervals of magnitudes of the redshifts inferred for the photometric sample
are in good agreement with the results of tomographic analyses. The inferred
redshifts also match the photometric redshifts of the redMaPPer galaxy clusters
for the probable cluster members. The CNN input and output are available at:
https://deepdip.iap.fr/treyer+2023. | astro-ph_CO |
Time variation of the Equation of State for Dark Energy: The time variation of the equation of state ($w_Q$) for the dark energy is
analyzed by the current values of parameters $\Omega_Q $, $w_Q $ and their time
derivatives. In the future, detailed feature of the dark energy could be
observed, so we have considered the second derivatives of $w_Q$ for two types
of potential: One is an inverse power-law type ($V=M^{4+\alpha}/Q^{\alpha}$)
and the other is an exponential one ($V=M^4\exp{(\beta M/Q)}$). The first
derivative $dw_Q/da$ and the second derivative $d^2 w_Q/da^2$ for both
potentials are derived. The first derivative is estimated by the observed two
parameters $\Delta=w_Q+1$ and $\Omega_Q$, with the assuming for $Q_0$. In the
limit $\Delta \rightarrow 0$, the first derivative is null and, under the
tracker approximation, the second derivative also becomes null. For the inverse
power potential $V=M^{4+\alpha}/Q^{\alpha}$, the observed first and second
derivatives are used to determine the potential parameter $M$ and $\alpha$. For
the potential of $V=M^4\exp{(\beta M/Q)}$, the second derivative is estimated
by the observed parameters $\Delta$, $\Omega_Q$ and $dw_Q/da$. | astro-ph_CO |
Studying the Dynamical Properties of 20 Nearby Galaxy Clusters: Using SDSS-DR7, we construct a sample of 42382 galaxies with redshifts in the
region of 20 galaxy clusters. Using two successive iterative methods, the
adaptive kernel method and the spherical infall model, we obtained 3396
galaxies as members belonging to the studied sample. The 2D projected map for
the distribution of the clusters members is introduced using the 2D adaptive
kernel method to get the clusters centers. The cumulative surface number
density profile for each cluster is fitted well with the generalized King
model. The core radii of the clusters' sample are found to vary from 0.18 Mpc
$\mbox{h}^{-1}$ (A1459) to 0.47 Mpc $\mbox{h}^{-1}$ (A2670) with mean value of
0.295 Mpc $\mbox{h}^{-1}$.
The infall velocity profile is determined using two different models, Yahil
approximation and Praton model. Yahil approximation is matched with the
distribution of galaxies only in the outskirts (infall regions) of many
clusters of the sample, while it is not matched with the distribution within
the inner core of the clusters. Both Yahil approximation and Praton model are
matched together in the infall region for about 9 clusters in the sample but
they are completely unmatched for the clusters characterized by high central
density. For these cluster, Yahil approximation is not matched with the
distribution of galaxies, while Praton model can describe well the infall
pattern of such clusters. | astro-ph_CO |
Precision cosmology from large-scale structure of the Universe: Large scale structure of the Universe becomes a leading source of precision
cosmological information. We present two particular tools that can be used in
cosmological analyses of the redshift space galaxy clustering data: a new
open-source code CLASS-PT and the theoretical error approach. CLASS-PT computes
one-loop power auto- and cross-power spectra for matter fields and biased
tracers in real and redshift spaces. We show that the code meets the precision
standards set by the upcoming high-precision large-scale structure surveys. The
theoretical error likelihood approach allows one to analyze galaxy clustering
data without having to measure the scale cut $k_{\rm max}$. This approach takes
into account that theoretical uncertainties affect parameter estimation
gradually, which helps optimize data analysis and ensures that all available
cosmological information is extracted. | astro-ph_CO |
Observational constraints on K-inflation models: We extend the ModeCode software of Mortonson, Peiris and Easther to enable
numerical computation of perturbations in K-inflation models, where the scalar
field no longer has a canonical kinetic term. Focussing on models where the
kinetic and potential terms can be separated into a sum, we compute slow-roll
predictions for various models and use these to verify the numerical code. A
Markov chain Monte Carlo analysis is then used to impose constraints from WMAP7
data on the addition of a term quadratic in the kinetic energy to the
Lagrangian of simple chaotic inflation models. For a quadratic potential, the
data do not discriminate against addition of such a term, while for a quartic
(\lambda \phi^4) potential inclusion of such a term is actually favoured.
Overall, constraints on such a term from present data are found to be extremely
weak. | astro-ph_CO |
Large Scale Anomalies in the Microwave Background: Causation and
Correlation: Most treatments of large scale anomalies in the microwave sky are a
posteriori, with unquantified look-elsewhere effects. We contrast these with
physical models of specific inhomogeneities in the early universe which then
generate apparent anomalies. Physical models predict correlations between
candidate anomalies, as well as the corresponding signals in polarization and
large scale structure, reducing the impact of cosmic variance. We compute the
apparent spatial curvature associated with large-scale inhomogeneities and show
that it is typically small, allowing for a self-consistent analysis. Focussing
on a single large plane wave inhomogeneity, we show this can contribute to
low-l mode alignment and odd-even asymmetry in the power spectra and the best
fit inhomogeneity accounts for a significant part of the claimed odd-even
asymmetry. We argue that this approach can be generalized to provide a more
quantitative assessment of potential large scale anomalies in the universe. | astro-ph_CO |
Sample variance, source clustering and their influence on the counts of
faint radio sources: The shape of the curves defined by the counts of radio sources per unit area
as a function of their flux density was one of the earliest cosmological
probes. Radio source counts continue to be an area of interest, used to study
the relative populations of galaxy types in the Universe (as well as
investigate any cosmological evolution in luminosity functions). They are a
vital consideration for determining how source confusion may limit the depth of
a radio interferometer observation, and are essential for characterising
extragalactic foregrounds in CMB experiments. There is currently no consensus
as to the relative populations of the faintest (sub-mJy) source types, where
the counts turn-up. Most of the source counts in this regime are gathered from
multiple observations that each use a deep, single pointing with a radio
interferometer. These independent measurements show large amounts of scatter
(factors ~ a few) that significantly exceeds their stated uncertainties. In
this article we use a simulation of the extragalactic radio continuum emission
to assess the level at which sample variance may be the cause of the scatter.
We find that the scatter induced by sample variance in the simulated counts
decreases towards lower flux density bins as the raw source counts increase.
The field-to-field variations are significant, and could even be the sole cause
at >100 {\mu}Jy. We present a method for evaluating the flux density limit that
a survey must reach in order to reduce the count uncertainty induced by sample
variance to a specific value. We also derive a method for correcting Poisson
errors on counts in order to include the uncertainties due to the cosmological
clustering of sources. An empirical constraint on the effect of sample variance
at these low luminosities is unlikely to arise until the completion of new
large-scale surveys with next-generation radio telescopes. | astro-ph_CO |
There was movement that was stationary, for the four-velocity had passed
around: Is the Doppler interpretation of galaxy redshifts in a
Friedmann-Lemaitre-Robertson-Walker (FLRW) model valid in the context of the
approach to comoving spatial sections pioneered by de Sitter, Friedmann,
Lemaitre and Robertson, i.e. according to which the 3-manifold of comoving
space is characterised by both its curvature and topology? Holonomy
transformations for flat, spherical and hyperbolic FLRW spatial sections are
proposed. By quotienting a simply-connected FLRW spatial section by an
appropriate group of holonomy transformations, the Doppler interpretation in a
non-expanding Minkowski space-time, obtained via four-velocity parallel
transport along a photon path, is found to imply that an inertial observer is
receding from herself at a speed greater than zero, implying contradictory
world-lines. The contradiction in the multiply-connected case occurs for
arbitrary redshifts in the flat and spherical cases, and for certain large
redshifts in the hyperbolic case. The link between the Doppler interpretation
of redshifts and cosmic topology can be understood physically as the link
between parallel transport along a photon path and the fact that the comoving
spatial geodesic corresponding to a photon's path can be a closed loop in an
FLRW model of any curvature. Closed comoving spatial loops are fundamental to
cosmic topology. | astro-ph_CO |
The lack of star formation gradients in galaxy groups up to z~1.6: In the local Universe, galaxy properties show a strong dependence on
environment. In cluster cores, early type galaxies dominate, whereas
star-forming galaxies are more and more common in the outskirts. At higher
redshifts and in somewhat less dense environments (e.g. galaxy groups), the
situation is less clear. One open issue is that of whether and how the star
formation rate (SFR) of galaxies in groups depends on the distance from the
centre of mass. To shed light on this topic, we have built a sample of X-ray
selected galaxy groups at 0<z<1.6 in various blank fields (ECDFS, COSMOS,
GOODS). We use a sample of spectroscopically confirmed group members with
stellar mass M >10^10.3 M_sun in order to have a high spectroscopic
completeness. As we use only spectroscopic redshifts, our results are not
affected by uncertainties due to projection effects. We use several SFR
indicators to link the star formation (SF) activity to the galaxy environment.
Taking advantage of the extremely deep mid-infrared Spitzer MIPS and
far-infrared Herschel PACS observations, we have an accurate, broad-band
measure of the SFR for the bulk of the star-forming galaxies. We use
multi-wavelength SED fitting techniques to estimate the stellar masses of all
objects and the SFR of the MIPS and PACS undetected galaxies. We analyse the
dependence of the SF activity, stellar mass and specific SFR on the
group-centric distance, up to z~1.6, for the first time. We do not find any
correlation between the mean SFR and group-centric distance at any redshift. We
do not observe any strong mass segregation either, in agreement with
predictions from simulations. Our results suggest that either groups have a
much smaller spread in accretion times with respect to the clusters and that
the relaxation time is longer than the group crossing time. | astro-ph_CO |
Multiple scattering Sunyaev-Zeldovich signal II: relativistic effects: We study the multiple scattering Sunyaev-Zeldovich (SZ) signature, extending
our previous analysis to high-temperature clusters. We consistently treat the
anisotropy of the ambient radiation field caused by the first scattering and
also consider lowest order kinematic terms. We show that due to temperature
corrections monopole through octupole anisotropy of the singly scattered SZ
signal attain different spectra in the second scattering. The difference
becomes more pronounced at high temperature, and thus could be used to
constrain individual line of sight moments of the electron density and
temperature profiles. While very challenging from the observational point of
view, this further extends the list of possible SZ observables that will be
important for 3D cluster-profile reconstruction, possibly helping to break
geometric degeneracies caused by projection effects. We also briefly discuss
the scattering of primordial CMB anisotropies by SZ clusters. | astro-ph_CO |
On the ISW-cluster cross-correlation in future surveys: We investigate the cosmological information contained in the
cross-correlation between the Integrated Sachs-Wolfe (ISW) of the Cosmic
Microwave Background (CMB) anisotropy pattern and galaxy clusters from future
wide surveys. Future surveys will provide cluster catalogues with a number of
objects comparable with galaxy catalogues currently used for the detection of
the ISW signal by cross-correlation with the CMB anisotropy pattern. By
computing the angular power spectra of clusters and the corresponding
cross-correlation with CMB, we perform a signal-to-noise ratio (SNR) analysis
for the ISW detection as expected from the eROSITA and the Euclid space
missions. We discuss the dependence of the SNR of the ISW-cluster
cross-correlation on the specifications of the catalogues and on the reference
cosmology. We forecast that the SNRs for ISW-cluster cross-correlation are
alightly smaller compared to those which can be obtained from future galaxy
surveys but the signal is expected to be detected at high significance, i.e.
more than $> 3\,\sigma$. We also forecast the joint constraints on parameters
of model extensions of the concordance $\Lambda$CDM cosmology by combining CMB
and the ISW-cluster cross-correlation. | astro-ph_CO |
Constraint on $f(R)$ Gravity through the Redshift Space Distortion: In this paper, a specific family of $f(R)$ models that can produce the
$\Lambda$CDM background expansion history is constrained by using the currently
available geometric and dynamic probes. The scale dependence of the growth rate
$f(z,k)$ in this specific family of $f(R)$ model is shown. Therefore to
eliminate the scale dependence of $f\sigma_8(z)$ in theory, which usually is
defined as the product of $f(z,k)$ and $\sigma_8(z)$, we define
$f\sigma_8(z)=d\sigma_8(z)/d\ln a$ which is obviously scale independent and
reproduces the conventional definition in the standard $\Lambda$CDM cosmology.
In doing so, under the assumption that future probes having the same best fit
values as the current ten data points of $f\sigma_8(z)$, even having $20\%$
error bars enlarged, we find a preliminary constraint
$f_{R0}=-2.58_{-0.58}^{+2.14}\times 10^{-6}$ in $1\sigma$ regions. This
indicates the great potential that redshift space distortions have in
constraining modified gravity theories. We also discuss the nonlinear matter
power spectrum based on different halo fit models. | astro-ph_CO |
Cross identification between X-ray and Optical Clusters of Galaxies in
the SDSS DR7 Field: We use the ROSAT all sky survey X-ray cluster catalogs and the optical SDSS
DR7 galaxy and group catalogs to cross-identify X-ray clusters with their
optical counterparts, resulting in a sample of 201 X-ray clusters in the sky
coverage of SDSS DR7. We investigate various correlations between the optical
and X-ray properties of these X-ray clusters, and find that the following
optical properties are correlated with the X-ray luminosity: the central galaxy
luminosity, the central galaxy mass, the characteristic group luminosity
($\propto \Lx^{0.43}$), the group stellar mass ($\propto \Lx^{0.46}$), with
typical 1-$\sigma$ scatter of $\sim 0.67$ in $\log \Lx$. Using the observed
number distribution of X-ray clusters, we obtain an unbiased scaling relation
between the X-ray luminosity, the central galaxy stellar mass and the
characteristic satellite stellar mass as ${\log L_X} = -0.26 + 2.90 [\log
(M_{\ast, c} + 0.26 M_{\rm sat}) -12.0]$ (and in terms of luminosities, as
${\log L_X} = -0.15 + 2.38 [\log (L_{c} + 0.72 L_{\rm sat}) -12.0]$). We find
that the systematic difference between different halo mass estimations, e.g.,
using the ranking of characteristic group stellar mass or using the X-ray
luminosity scaling relation can be used to constrain cosmology. Comparing the
properties of groups of similar stellar mass (or optical luminosities) and
redshift that are X-ray luminous or under-luminous, we find that X-ray luminous
groups have more faint satellite galaxies and higher red fraction in their
satellites. The cross-identified X-ray clusters together with their optical
properties are provided in Appendix B. | astro-ph_CO |
Constraint on noncommutative spacetime from PLANCK data: We constrain the energy scale of noncommutativity of spacetime using CMB data
from PLANCK. We find that PLANCK data puts the lower bound on the
noncommutativity energy scale to about 20 TeV, which is about a factor of two
larger than a previous constraint that was obtained using data from WMAP, ACBAR
and CBI. We further show that inclusion of data of $E$ mode of CMB polarization
will not significantly change the constraint. | astro-ph_CO |
Outflowing Galactic Winds in Post-starburst and AGN Host Galaxies at
0.2<z<0.8: We present Keck/LRIS-B spectra for a sample of ten AEGIS X-ray AGN host
galaxies and thirteen post-starburst galaxies from SDSS and DEEP2 at 0.2<z<0.8
in order to investigate the presence, properties, and influence of outflowing
galactic winds at intermediate redshifts. We focus on galaxies that either host
a low-luminosity AGN or have recently had their star formation quenched to test
whether these galaxies have winds of sufficient velocity to potentially clear
gas from the galaxy. We find, using absorption features of Fe II, Mg II, and Mg
I, that six of the ten (60%) X-ray AGN host galaxies and four of the thirteen
(31%) post-starburst galaxies have outflowing galactic winds, with typical
velocities of ~200 km/s. We additionally find that most of the galaxies in our
sample show line emission, possibly from the wind, in either Fe II* or Mg II. A
total of 100% of our X-ray AGN host sample (including four red sequence
galaxies) and 77% of our post-starburst sample has either blueshifted
absorption or line emission. Several K+A galaxies have small amounts of cool
gas absorption at the systemic velocity, indicating that not all of the cool
gas has been expelled. We conclude that while outflowing galactic winds are
common in both X-ray low-luminosity AGN host galaxies and post-starburst
galaxies at intermediate redshifts, the winds are likely driven by supernovae
(as opposed to AGN) and do not appear to have sufficiently high velocities to
quench star formation in these galaxies. | astro-ph_CO |
Constraining primordial magnetic fields with distortions of the
black-body spectrum of the cosmic microwave background: pre- and
post-decoupling contributions: Observational limits on $y$- and $\mu$-type distortions can constrain
properties of magnetic fields in the early universe. For a Gaussian, random,
and non-helical field, $\mu$ and $y$ are calculated a function of the
present-day strength of the field, $B_0$, smoothed over a certain Gaussian
width, $k_c^{-1}$, and spectral index, $n_B$, defined by $P_B(k)\propto
k^{n_B}$. For $n_B=-2.9$ and $k_c^{-1}=1 {\rm Mpc}$, the COBE/FIRAS limit on
$\mu$ yields $B_0<40$ nG, whereas the projected PIXIE limit on $\mu$ would
yield $B_0<0.8$ nG. For non-scale-invariant spectra, constraints can be
stronger. For $B_0=1$ nG with $k_c^{-1}=1 {\rm Mpc}$, the COBE/FIRAS limit on
$\mu$ excludes a wide range of spectral indices given by $n_B>-2.6$. After
decoupling, energy dissipation is due to ambipolar diffusion and decaying MHD
turbulence, creating a $y$-type distortion. The distortion is completely
dominated by decaying MHD turbulence, and is of order $y\approx 10^{-7}$ for a
few nG field smoothed over the damping scale at the decoupling epoch,
$k_{d,dec}\approx 290 (B_0/1 {\rm nG})^{-1} {\rm Mpc}^{-1}$. This contribution
is as large as those of the known contributions such as reionization and
virialized objects at lower redshifts. The projected PIXIE limit on $y$ would
exclude $B_0>1.0$ and 0.6 nG for $n_B=-2.9$ and -2.3, respectively, and
$B_0>0.6$ nG for $n_B\geq 2$. The current limits on the optical depth to
Thomson scattering restrict the predicted $y$-type distortion to be $y\lesssim
10^{-8}$. (Abridged) | astro-ph_CO |
Orbiting Circum-galactic Gas as a Signature of Cosmological Accretion: We use cosmological SPH simulations to study the kinematic signatures of cool
gas accretion onto a pair of well-resolved galaxy halos. Cold-flow streams and
gas-rich mergers produce a circum-galactic component of cool gas that generally
orbits with high angular momentum about the galaxy halo before falling in to
build the disk. This signature of cosmological accretion should be observable
using background-object absorption line studies as features that are offset
from the galaxy's systemic velocity by ~100 km/s. Accreted gas typically
co-rotates with the central disk in the form of a warped, extended cold flow
disk, such that the observed velocity offset is in the same direction as galaxy
rotation, appearing in sight lines that avoid the galactic poles. This
prediction provides a means to observationally distinguish accreted gas from
outflow gas: the accreted gas will show large one-sided velocity offsets in
absorption line studies while radial/bi-conical outflows will not (except
possibly in special polar projections). This rotation signature has already
been seen in studies of intermediate redshift galaxy-absorber pairs; we suggest
that these observations may be among the first to provide indirect
observational evidence for cold accretion onto galactic halos. Cold mode halo
gas typically has ~3-5 times more specific angular momentum than the dark
matter. The associated cold mode disk configurations are likely related to
extended HI/XUV disks seen around galaxies in the local universe. The fraction
of galaxies with extended cold flow disks and associated offset absorption-line
gas should decrease around bright galaxies at low redshift, as cold mode
accretion dies out. | astro-ph_CO |
Fast radio bursts as a cosmic probe?: We discuss the possibility of using fast radio bursts (FRBs), if
cosmological, as a viable cosmic probe. We find out that the contribution of
the host galaxies to the detected dispersion measures can be inapparent for the
FRBs not from galaxy centers or star forming regions. The inhomogeneity of the
intergalactic medium (IGM), however, causes significant deviation of the
dispersion measure from that predicted in the simplified homogeneous IGM model
for individual event. Fortunately, with sufficient FRBs along different
sightlines but within a very narrow redshift interval (e.g., $\Delta z \sim
0.05$ or $\Delta z \sim 0.05(1+z)$), the mean from averaging observed
dispersion measures does not suffer such a problem and hence may be used as a
cosmic probe. We show that in the optimistic case (e.g., tens FRBs in each
$\Delta z$ have been measured; the most distant FRBs were at redshift $\geq 3$;
the host galaxies and the FRB sources contribute little to the detected
dispersion measures) and with all the uncertainties (i.e. the inhomogeneity of
the IGM, the contribution and uncertainty of host galaxies as well as the
evolution and error of $f_{\rm IGM}$) considered, FRBs could help constrain the
equation of state of dark energy. | astro-ph_CO |
Inhomogeneous initial conditions for inflation: A wibbly-wobbly
timey-wimey path to salvation: We use the 3+1 formalism of numerical relativity to investigate the
robustness of Starobinsky and Higgs inflation to inhomogeneous initial
conditions, in the form of either field gradient or kinetic energy density.
Sub-Hubble and Hubble-sized fluctuations generically lead to inflation after an
oscillatory phase between gradient and kinetic energies. Hubble-sized
inhomogeneities also produce contracting regions that may end up forming
primordial black holes, subsequently diluted by inflation. We analyse the
dynamics of the preinflation era and the generation of vector and tensor
fluctuations. Our analysis further supports the robustness of inflation to any
size of inhomogeneity, in the field, velocity or equation of state. At large
field values, the preinflation dynamics only marginally depends on the field
potential and it is expected that such behaviour is universal and applies to
any inflation potential of plateau-type, favoured by CMB observations after
Planck. | astro-ph_CO |
Multi-messenger constraints on dark matter annihilation into
electron-positron pairs: We investigate the production of electrons and positrons in the Milky Way
within the context of dark matter annihilation. Upper limits on the relevant
cross-section are obtained by combining observational data at different
wavelengths (from Haslam, WMAP, and Fermi all-sky intensity maps) with recent
measurements of the electron and positron spectra in the solar neighbourhood by
PAMELA, Fermi, and HESS. We consider synchrotron emission in the radio and
microwave bands, as well as inverse Compton scattering and final-state
radiation at gamma-ray energies. According to our results, the dark matter
annihilation cross-section into electron-positron pairs should not be higher
than the canonical value for a thermal relic if the mass of the dark matter
candidate is smaller than a few GeV. In addition, we also derive a stringent
upper limit on the inner logarithmic slope, alpha, of the density profile of
the Milky Way dark matter halo (alpha < 1 if m_dm < 5 GeV, alpha < 1.3 if m_dm
< 100 GeV and alpha < 1.5 if m_dm < 2 TeV) assuming that cross-section = 3 x
10^(-26) cm^3 s(-1). A logarithmic slope steeper than alpha about 1.5 is hardly
compatible with a thermal relic lighter than about 1 TeV, regardless of the
dominant annihilation channel. | astro-ph_CO |
Analyzing the Hubble tension through hidden sector dynamics in the early
universe: The recent analysis from the SH0ES Collaboration has confirmed the existence
of a Hubble tension between measurements at high redshift ($z> 1000$) and at
low redshift ($z<1$) at the $5\sigma$ level with the low redshift measurement
giving a higher value. In this work we propose a particle physics model that
can help alleviate the Hubble tension via an out-of-equilibrium hidden sector
coupled to the visible sector. The particles that populate the dark sector
consist of a dark fermion, which acts as dark matter, a dark photon, a massive
scalar and a massless pseudo-scalar. Assuming no initial population of
particles in the dark sector, feeble couplings between the visible and the
hidden sectors via kinetic mixing populate the dark sector even though the
number densities of hidden sector particles never reach their equilibrium
distribution and the two sectors remain at different temperatures. A
cosmologically consistent analysis is presented where a correlated evolution of
the visible and the hidden sectors with coupled Boltzmann equations involving
two temperatures, one for the visible sector and the other for the hidden
sector, is carried out. The relic density of the dark matter constituted of
dark fermions is computed in this two-temperature formalism. As a consequence,
BBN predictions are upheld with a minimal contribution to $\Delta N_{\rm eff}$.
However, the out-of-equilibrium decay of the massive scalar to the massless
pseudo-scalar close to the recombination time causes an increase in $\Delta
N_{\rm eff}$ that can help weaken the Hubble tension. | astro-ph_CO |
The First Stars May Shed Light on Dark Matter: Recent observations of hydrogen absorption that occurred when the first stars
turned on may give insights into the nature of dark matter. | astro-ph_CO |
The smearing scale in Laguerre reconstructions of the correlation
function: To a good approximation, on large cosmological scales the evolved two-point
correlation function of biased tracers is related to the initial one by a
convolution. For Gaussian initial conditions, the smearing kernel is Gaussian,
so if the initial correlation function is parametrized using simple polynomials
then the evolved correlation function is a sum of generalized Laguerre
functions of half-integer order. This motivates an analytic Laguerre
reconstruction algorithm which previous work has shown is fast and accurate.
This reconstruction requires as input the width of the smearing kernel. We show
that the method can be extended to estimate the width of the smearing kernel
from the same dataset. This estimate, and associated uncertainties, can then be
used to marginalize over the distribution of reconstructed shapes, and hence
provide error estimates on the value of the distance scale which are not tied
to a particular cosmological model. We also show that if, instead, we
parametrize the evolved correlation function using simple polynomials, then the
initial one is a sum of Hermite polynomials, again enabling fast and accurate
deconvolution. If one is willing to use constraints on the smearing scale from
other datasets, then marginalizing over its value is simpler for Hermite
reconstruction, potentially providing further speed-up in cosmological
analyses. | astro-ph_CO |
On the Masses of Galaxies in the Local Universe: We compare estimates of stellar mass, Mstar, and dynamical mass,Mdyn,for a
sample of galaxies from the Sloan Digital Sky Survey (SDSS). We assume
dynamical homology (i.e., Mdyn = dispersion**2 * Reff, and we find a tight but
strongly non-linear relation: the best fit relation is Mstar = Mdyn**0.73, with
an observed scatter of 0.15 dex. We also find that, at fixed Mstar, the ratio
Mstar/Mdyn depends strongly on galaxy structure, as parameterized by Sersic
index, n. The size of the differential effect is on the order of 0.6 dex across
2 < n < 10. The apparent n-dependence of Mstar/Mdyn is similar to expectations
from simple models, indicating that assuming homology gives the wrong dynamical
mass. We have also derived dynamical mass estimates that explicitly account for
differences in galaxies' profiles. Using this `structure-corrected' dynamical
mass estimator, M(dyn,n), the best fit relation is Mstar = M(dyn,n)**(0.92 +-
0.08) with an observed scatter of 0.13 dex. While the data are thus consistent
with a linear relation, they do prefer a slightly shallower slope. Further, we
see only a small residual trend in Mstar/M(dyn,n) with n. We find no
statistically significant systematic trends in Mstar/M(dyn,n) as a function of
observed quantities (e.g, apparent magnitude, redshift), or as a function of
tracers of stellar populations. The net differential bias in Mstar/M(dyn,n)
across a wide range of stellar populations and star formation activities is <=
0.12 dex. The very good agreement between stellar mass and structure-corrected
dynamical mass strongly suggests that: 1.) galaxy non-homology has a major
impact on dynamical mass estimates, and 2. there are not strong systematic
biases in the stellar mass-to-light ratios derived from broadband optical SEDs.
Further, these results suggest that that the central dark-to-luminous mass
ratio has a relatively weak mass dependence. | astro-ph_CO |
Low Masses and High Redshifts: The Evolution of the Mass-Metallicity
Relation: We present the first robust measurement of the high redshift mass-metallicity
(MZ) relation at 10^{8}< M/M_{\sun} < 10^{10}, obtained by stacking spectra of
83 emission-line galaxies with secure redshifts between 1.3 < z < 2.3. For
these redshifts, infrared grism spectroscopy with the Hubble Space Telescope
Wide Field Camera 3 is sensitive to the R23 metallicity diagnostic:
([OII]3726,3729 + [OIII] 4959,5007)/H\beta. Using spectra stacked in four mass
quartiles, we find a MZ relation that declines significantly with decreasing
mass, extending from 12+log(O/H) = 8.8 at M=10^{9.8} M_{\sun} to 12+log(O/H)=
8.2 at M=10^{8.2} M_{\sun}. After correcting for systematic offsets between
metallicity indicators, we compare our MZ relation to measurements from the
stacked spectra of galaxies with M>10^{9.5} M_{\sun} and z~2.3. Within the
statistical uncertainties, our MZ relation agrees with the z~2.3 result,
particularly since our somewhat higher metallicities (by around 0.1 dex) are
qualitatively consistent with the lower mean redshift z=1.76 of our sample. For
the masses probed by our data, the MZ relation shows a steep slope which is
suggestive of feedback from energy-driven winds, and a cosmological downsizing
evolution where high mass galaxies reach the local MZ relation at earlier
times. In addition, we show that our sample falls on an extrapolation of the
star-forming main sequence (the SFR-M_{*} relation) at this redshift. This
result indicates that grism emission-line selected samples do not have
preferentially high SFRs. Finally, we report no evidence for evolution of the
mass-metallicity-SFR plane; our stack-averaged measurements show excellent
agreement with the local relation. | astro-ph_CO |
The Effective Theory of Inflation and the Dark Matter Status in the
Standard Model of the Universe: We present here the effective theory of inflation `a la Ginsburg-Landau in
which the inflaton potential is a polynomial. The slow-roll expansion becomes a
systematic 1/N expansion where N ~ 60. The spectral index and the ratio of
tensor/scalar fluctuations are n_s - 1 = O(1/N), r = O(1/N) while the running
turns to be d n_s/d \ln k = O(1/N^2) and can be neglected. The energy scale of
inflation M ~ 0.7 10^{16} GeV is completely determined by the amplitude of the
scalar adiabatic fluctuations. A complete analytic study plus the Monte Carlo
Markov Chains (MCMC) analysis of the available CMB+LSS data showed: (a) the
spontaneous breaking of the phi -> - phi symmetry of the inflaton potential.
(b) a lower bound for r: r > 0.023 (95% CL) and r > 0.046 (68% CL). (c) The
preferred inflation potential is a double well, even function of the field with
a moderate quartic coupling yielding as most probable values: n_s = 0.964, r =
0.051. This value for r is within reach of forthcoming CMB observations. We
investigate the DM properties using cosmological theory and the galaxy
observations. Our DM analysis is independent of the particle physics model for
DM and it is based on the DM phase-space density rho_{DM}/sigma^3_{DM}. We
derive explicit formulas for the DM particle mass m and for the number of
ultrarelativistic degrees of freedom g_d (hence the temperature) at decoupling.
We find that m turns to be at the keV scale. The keV scale DM is
non-relativistic during structure formation, reproduces the small and large
scale structure but it cannot be responsible of the e^+ and pbar excess in
cosmic rays which can be explained by astrophysical mechanisms (Abridged). | astro-ph_CO |
Euclid Preparation. XXVIII. Forecasts for ten different higher-order
weak lensing statistics: Recent cosmic shear studies have shown that higher-order statistics (HOS)
developed by independent teams now outperform standard two-point estimators in
terms of statistical precision thanks to their sensitivity to the non-Gaussian
features of large-scale structure. The aim of the Higher-Order Weak Lensing
Statistics (HOWLS) project is to assess, compare, and combine the constraining
power of ten different HOS on a common set of $Euclid$-like mocks, derived from
N-body simulations. In this first paper of the HOWLS series, we computed the
nontomographic ($\Omega_{\rm m}$, $\sigma_8$) Fisher information for the
one-point probability distribution function, peak counts, Minkowski
functionals, Betti numbers, persistent homology Betti numbers and heatmap, and
scattering transform coefficients, and we compare them to the shear and
convergence two-point correlation functions in the absence of any systematic
bias. We also include forecasts for three implementations of higher-order
moments, but these cannot be robustly interpreted as the Gaussian likelihood
assumption breaks down for these statistics. Taken individually, we find that
each HOS outperforms the two-point statistics by a factor of around two in the
precision of the forecasts with some variations across statistics and
cosmological parameters. When combining all the HOS, this increases to a $4.5$
times improvement, highlighting the immense potential of HOS for cosmic shear
cosmological analyses with $Euclid$. The data used in this analysis are
publicly released with the paper. | 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 |
Pressure Support vs. Thermal Broadening in the Lyman-alpha Forest II:
Effects of the Equation of State on Transverse Structure: We examine the impact of gas pressure on the transverse coherence of
high-redshift (2 <= z <= 4) Lyman-alpha forest absorption along neighboring
lines of sight that probe the gas Jeans scale (projected separation Delta r <=
500 kpc/h comoving; angular separation Delta theta <= 30"). We compare
predictions from two smoothed particle hydrodynamics (SPH) simulations that
have different photoionization heating rates and thus different
temperature-density relations in the intergalactic medium (IGM). We also
compare spectra computed from the gas distributions to those computed from the
pressureless dark matter. The coherence along neighboring sightlines is
markedly higher for the hotter, higher pressure simulation, and lower for the
dark matter spectra. We quantify this coherence using the flux
cross-correlation function and the conditional distribution of flux decrements
as a function of transverse and line-of-sight (velocity) separation. Sightlines
separated by Delta theta <= 15" are ideal for probing this transverse
coherence. Higher pressure decreases the redshift-space anisotropy of the flux
correlation function, while higher thermal broadening increases the anisotropy.
In contrast to the longitudinal (line-of-sight) structure of the Lya forest,
the transverse structure on these scales is dominated by pressure effects
rather than thermal broadening. With the rapid recent growth in the number of
known close quasar pairs, paired line-of-sight observations offer a promising
new route to probe the IGM temperature-density relation and test the
unexpectedly high temperatures that have been inferred from single sightline
analyses. | astro-ph_CO |
CMB Polarization Systematics, Cosmological Birefringence and the
Gravitational Waves Background: Cosmic Microwave Background experiments must achieve very accurate
calibration of their polarization reference frame to avoid biasing the
cosmological parameters. In particular, a wrong or inaccurate calibration might
mimic the presence of a gravitational wave background, or a signal from
cosmological birefringence, a phenomenon characteristic of several
non-standard, symmetry breaking theories of electrodynamics that allow for
\textit{in vacuo} rotation if the polarization direction of the photon.
Noteworthly, several authors have claimed that the BOOMERanG 2003 (B2K)
published polarized power spectra of the CMB may hint at cosmological
birefringence. Such analyses, however, do not take into account the reported
calibration uncertainties of the BOOMERanG focal plane. We develop a formalism
to include this effect and apply it to the BOOMERanG dataset, finding a
cosmological rotation angle $\alpha=-4.3^\circ\pm4.1^\circ$. We also
investigate the expected performances of future space borne experiment, finding
that an overall miscalibration larger then $1^\circ$ for Planck and $0.2\circ$
for EPIC, if not properly taken into account, will produce a bias on the
constraints on the cosmological parameters and could misleadingly suggest the
presence of a GW background. | astro-ph_CO |
Dark Sector to Restore Cosmological Concordance: We develop a new phenomenological model that addresses current tensions
between observations of the early and late Universe. Our scenario features: (i)
a decaying dark energy fluid (DDE), which undergoes a transition at $z \sim
5,000$, to raise today's value of the Hubble parameter -- addressing the $H_0$
tension, and (ii) an ultra-light axion (ULA), which starts oscillating at
$z\gtrsim 10^4$, to suppress the matter power spectrum -- addressing the $S_8$
tension. Our Markov Chain Monte Carlo analyses show that such a Dark Sector
model fits a combination of Cosmic Microwave Background (CMB), Baryon Acoustic
Oscillations, and Large Scale Structure (LSS) data slightly better than the
$\Lambda$CDM model, while importantly reducing both the $H_0$ and $S_8$
tensions with late universe probes ($\lesssim 3\sigma$). Combined with
measurements from cosmic shear surveys, we find that the discrepancy on $S_8$
is reduced to the $1.4\sigma$ level, and the value of $H_0$ is further raised.
Adding local supernovae measurements, we find that the $H_0$ and $S_8$ tensions
are reduced to the $1.4\sigma$ and $1.2\sigma$ level respectively, with a
significant improvement $\Delta\chi^2\simeq -18$ compared to the $\Lambda$CDM
model. With this complete dataset, the DDE and ULA are detected at $\simeq
4\sigma$ and $\simeq2\sigma$, respectively. We discuss a possible particle
physics realization of this model, with a dark confining gauge sector and its
associated axion, although embedding the full details within microphysics
remains an urgent open question. Our scenario will be decisively probed with
future CMB and LSS surveys. | astro-ph_CO |
AGN feedback in clusters: shock and sound heating: Observations support the view that feedback, in the form of radio outbursts
from active nuclei in central galaxies, prevents catastrophic cooling of gas
and rapid star formation in many groups and clusters of galaxies. Variations in
jet power drive a succession of weak shocks that can heat regions close to the
active galactic nuclei (AGN). On larger scales, shocks fade into sound waves.
The Braginskii viscosity determines a well-defined sound damping rate in the
weakly magnetized intracluster medium (ICM) that can provide sufficient heating
on larger scales. It is argued that weak shocks and sound dissipation are the
main means by which radio AGN heat the ICM, in which case, the power spectrum
of AGN outbursts plays a central role in AGN feedback. | astro-ph_CO |
A detailed study of the bridge of excess X-ray emission between the
galaxy clusters Abell 2029 and Abell 2033: We examine Suzaku, XMM-Newton, and Chandra observations of the Abell
2029/2033 system to investigate the nature of a bridge of X-ray emission
joining the two galaxy clusters. By modelling the contributions from the
outskirts of the two clusters, and excluding the emission from the southern
infalling group and the background group LOS9, we find a significant excess of
X-ray emission between the two clusters at the level of 6.5-7.0$\sigma$,
depending on the choice of model, that cannot be explained by the overlap of
the clusters. This excess component to the surface brightness is consistent
with being emission from a filament with roughly 1.0 Mpc wide. The derived
emission measure for the gas associated with the filament yields an average gas
density of $3.7^{+1.0}_{-0.7} \times 10^{-5}$ cm$^{-3}$, corresponding roughly
to 160 times the mean baryon density of the Universe. The Suzaku X-ray spectrum
of the excess emission indicates that it is significantly colder
($1.4_{-0.5}^{+0.7}$ keV) than the cluster outskirts emission from the two
clusters ($\sim$ 5 keV), statistically consistent with the temperature expected
from the hottest and densest parts of the warm-hot intergalactic medium (WHIM).
The geometry, density, and temperature are similar to those found from X-ray
studies of the Abell 222/223 filament. | astro-ph_CO |
O-V-S-Z and friends: Non-Gaussianity from inhomogeneous reionization: We calculate the cosmic microwave background (CMB) bispectrum due to
inhomogeneous reionization. We calculate all the terms that can contribute to
the bispectrum that are products of first order terms on all scales in
conformal Newtonian gauge. We also correctly account for the de-correlation
between the matter density and initial conditions using perturbation theory up
to third order. We find that the bispectrum is of local type as expected. For a
reasonable model of reionization, in which the Universe is completely ionized
by redshift z_{ri} ~ 8 with optical depth to the last scattering surface
\tau_0=0.087 the signal to noise for detection of the CMB temperature
bispectrum is S/N ~ 0.1 and confusion in the estimation of primordial
non-Gaussianity is f_{NL} ~ -0.1. For an extreme model with z_{ri} ~ 12.5,
\tau_0=0.14 we get S/N ~ 0.5 and f_{NL} ~ -0.2. | astro-ph_CO |
Velocity Bias from the Small Scale Clustering of SDSS-III BOSS Galaxies: We present the measurements and modelling of the projected and redshift-space
clustering of CMASS galaxies in the Sloan Digital Sky Survey-III Baryon
Oscillation Spectroscopic Survey Data Release 11. For a volume-limited luminous
red galaxy sample in the redshift range of $0.48<z<0.55$, we perform halo
occupation distribution modelling of the small- and intermediate-scale
($0.1$--$60h^{-1}{\rm {Mpc}}$) projected and redshift-space two-point
correlation functions, with an accurate model built on high resolution $N$-body
simulations. To interpret the measured redshift-space distortions, the
distribution of galaxy velocities must differ from that of the dark matter
inside haloes of $\sim 10^{13}$--$10^{14}h^{-1}{\rm M_{\odot}}$, i.e. the data
require the existence of galaxy velocity bias. Most notably, central galaxies
on average are not at rest with respect to the core of their host haloes
(defined by the inner 25% of particles around the halo potential minimum), but
rather move around it with a 1D velocity dispersion of $0.22^{+0.03}_{-0.04}$
times that of the dark matter, implying a spatial offset from the centre at the
level of $\lesssim$1% of the halo virial radius. The luminous satellite
galaxies move more slowly than the dark matter, with velocities
$0.86^{+0.08}_{-0.03}$ times those of the dark matter, which suggests that the
velocity and spatial distributions of these satellites cannot both be unbiased.
The constraints mainly arise from the Fingers-of-God effect at nonlinear scales
and the smoothing to the Kaiser effect in the translinear regime; the
robustness of the results is demonstrated by a variety of tests. In addition,
no clear evidence is found for a strong luminosity dependence of the velocity
bias. We discuss the implications of the existence of galaxy velocity bias for
investigations of galaxy formation and cosmology. | astro-ph_CO |
A New Era in Extragalactic Background Light Measurements: The Cosmic
History of Accretion, Nucleosynthesis and Reionization: (Brief Summary) What is the total radiative content of the Universe since the
epoch of recombination? The extragalactic background light (EBL) spectrum
captures the redshifted energy released from the first stellar objects,
protogalaxies, and galaxies throughout cosmic history. Yet, we have not
determined the brightness of the extragalactic sky from UV/optical to
far-infrared wavelengths with sufficient accuracy to establish the radiative
content of the Universe to better than an order of magnitude. Among many
science topics, an accurate measurement of the EBL spectrum from optical to
far-IR wavelengths, will address: What is the total energy released by stellar
nucleosynthesis over cosmic history? Was significant energy released by
non-stellar processes? Is there a diffuse component to the EBL anywhere from
optical to sub-millimeter? When did first stars appear and how luminous was the
reionization epoch? Absolute optical to mid-IR EBL spectrum to an
astrophysically interesting accuracy can be established by wide field imagingat
a distance of 5 AU or above the ecliptic plane where the zodiacal foreground is
reduced by more than two orders of magnitude. | astro-ph_CO |
Probing X-ray irradiation in the nucleus of NGC 1068 with observations
of high-J lines of dense gas tracers: With the incorporation of high-J molecular lines, we aim to constrain the
physical conditions of the dense gas in the central region of the Seyfert 2
galaxy NGC 1068 and to determine signatures of the AGN or the starburst
contribution.
We used the James Clerk Maxwell Telescope to observe the J=4-3 transition of
HCN, HNC, and HCO+, as well as the CN N_J=2_{5/2}-1_{3/2} and
N_J=3_{5/2}-2_{5/2}, in NGC 1068.
We estimate the excitation conditions of HCN, HNC, and CN, based on the line
intensity ratios and radiative transfer models.
We find that the bulk emission of HCN, HNC, CN, and the high-J HCO+ emerge
from dense gas n(H_2)>=10^5 cm^-3). However, the low-J HCO+ lines (dominating
the HCO+ column density) trace less dense (n(H_2)<10^5 cm^-3) and colder
(T_K<=20 K) gas, whereas the high-J HCO+ emerges from warmer (>30 K) gas than
the other molecules.
The HCO+ J=4-3 line intensity, compared with the lower transition lines and
with the HCN J=4-3 line, support the influence of a local XDR environment. The
estimated N(CN)/N(HCN)~1-4 column density ratios are indicative of an XDR/AGN
environment with a possible contribution of grain-surface chemistry induced by
X-rays or shocks. | astro-ph_CO |
The Large-scale Distribution of Cool Gas around Luminous Red Galaxies: We present a measurement of the correlation function between luminous red
galaxies and cool gas traced by Mg II \lambda \lambda 2796, 2803 absorption, on
scales ranging from about 30 kpc to 20 Mpc. The measurement is based on
cross-correlating the positions of about one million red galaxies at z~0.5 and
the flux decrements induced in the spectra of about 10^5 background quasars
from the Sloan Digital Sky Survey. We find that: (i) This galaxy-gas
correlation reveals a change of slope on scales of about 1 Mpc, consistent with
the expected transition from a dark matter halo dominated environment to a
regime where clustering is dominated by halo-halo correlations. Assuming that,
on average, the distribution of Mg II gas follows that of dark matter up to a
gas-to-mass ratio, we find the standard halo model to provide an accurate
description of the gas distribution over three orders of magnitude in scale.
Within this framework we estimate the average host halo mass of luminous red
galaxies to be about 10^{13.5} M_solar, in agreement with other methods. We
also find the Mg II gas-to-mass ratio around LRGs to be consistent with the
cosmic value estimated on Mpc scales. Combining our galaxy-gas correlation and
the galaxy-mass correlation function from galaxy-galaxy lensing analyses we can
directly measure the Mg II gas-to-mass ratio as a function of scale and reach
the same conclusion. (ii) From line-width estimates, we show that the velocity
dispersion of the gas clouds also shows the expected 1- and 2-halo behaviors.
On large scales the gas distribution follows the Hubble flow, whereas on small
scales we observe the velocity dispersion of the Mg II gas clouds to be lower
than that of collisionless dark matter particles within their host halo. This
is in line with the fact that cool clouds are subject to the pressure of the
virialized hot gas. | astro-ph_CO |
Random versus holographic fluctuations of the background metric. II.
Note on the dark energies arising due to microstructure of space-time: Over the last few years a certain class of dark-energy models decaying
inversely proportional to the square of the horizon distance emerged on the
basis either of Heisenberg uncertainty relations or of the uncertainty relation
between the four-volume and the cosmological constant. The very nature of these
dark energies is understood to be the same, namely it is the energy of
background space/metric fluctuations. Putting together these uncertainty
relations one finds that the model of random fluctuations of the background
metric is favored over the holographic one. | astro-ph_CO |
A detailed view of filaments and sheets in the warm-hot intergalactic
medium. I. Pancake formation: Numerical simulations predict a considerable fraction of the missing baryons
at redshift z ~ 0 resting in the so called warm-hot intergalactic medium
(WHIM). The filaments and sheets of the WHIM have high temperatures 10^5 - 10^7
K) and a high degree of ionization while having only low to intermediate
densities. The particular physical conditions of the WHIM structures, e.g.
density and temperature profiles, velocity fields, are expected to leave their
special imprint on spectroscopic observations. In order to get further insight
into these conditions, we perform hydrodynamical simulations of the WHIM.
Instead of analyzing large simulations of cosmological structure formation, we
simulate particular well-defined structures and study the impact of different
physical processes as well as of the scale dependencies. We start with the
comprehensive study of the one-dimensional collapse (pancake) and examine the
influence of radiative cooling, heating due to an UV background, and thermal
conduction. We investigate the effect of small scale perturbations given
according to the initial cosmological power spectrum. If the initial
perturbation length scale L exceeds ~ 2 Mpc the collapse leads to shock
confined structures. As a result of radiative cooling and of heating due to an
UV background a relatively cold and dense core forms in the one-dimensional
case. The properties of the core (extension, density, and temperature) are
correlated with L. For larger L the core sizes are more concentrated. Thermal
conduction enhances this trend and may even result in an evaporation of the
core. Our estimates predict that a core may start to evaporate for perturbation
lengths larger than L ~ 30 Mpc. The obtained detailed profiles for density and
temperature for prototype WHIM structures allow for the determination of
possible spectral signatures by the WHIM. | astro-ph_CO |
Measuring lensing ratios with future cosmological surveys: The ratio between the CMB lensing/galaxy counts and the galaxy shear/galaxy
counts cross-correlations combines the information from different cosmological
probes to infer cosmographic measurements that are less dependent on
astrophysical uncertainties and can constrain the geometry of the Universe. We
discuss the future perspectives for the measurement of this lensing ratio as
previously introduced, i.e. with the use of the Limber and flat-sky
approximations and neglecting all the effects on the galaxy survey from
observing on the past lightcone. We then show how the cosmological information
in this estimator is affected by the Limber approximation and by the inclusion
of the redshift space distorsions (RSD) and magnification lensing contributions
to the galaxy number counts. We find that the magnification lensing
contribution induces a multipole dependence of the lensing ratio that we show
to be detectable at a statistical significant level combining post-$Planck$ CMB
surveys and a Euclid-like experiment. We propose an improved estimator which
takes into account this angular scale dependence. Using this extended
formalism, we present forecasts for upcoming and future cosmological surveys
and we show at which extent the lensing ratio information can improve the CMB
constraints on cosmological parameters. We get that for extended cosmological
models where the neutrino mass, the spatial curvature and the dark energy
equation of state are allowed to vary, the constraints from $Planck$ on these
parameters and on $H_0$ can be reduced by $\sim 40\%$ with the inclusion of a
single lensing ratio and by $\sim 60-70\%$ adding the joint measurement of 9
lensing ratios with a Euclid-like survey. We also find that neglegcting the
contribution from magnification lensing can induce a bias on the derived
cosmological parameters in a combined analysis. | astro-ph_CO |