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Do stellar winds play a decisive role in feeding AGN?: While the existence of a starburst-AGN connection is undisputed, there is no
consensus on what the connection is. In this contribution, we begin by noting
that the mechanisms which drive gas inwards in disk galaxies are generally
inefficient at removing angular momentum, leading to stalled inflows. Thus, a
tiered series of such processes is required to bring gas to the smallest
scales, each of which on its own may not correlate with the presence of an AGN.
Similarly, each may be associated with a starburst event, making it important
to discriminate between 'circumnuclear' and 'nuclear' star formation. In this
contribution, we show that stellar feedback on scales of tens of parsecs plays
a critical role in first hindering and then helping accretion. We argue that it
is only after the initial turbulent phases of a starburst that gas from slow
stellar winds can accrete efficiently to smaller scales. This would imply that
the properties of the obscuring torus are directly coupled to star formation
and that the torus must be a complex dynamical entity. We finish by remarking
on other contexts where similar processes appear to be at work. | astro-ph_CO |
Strong Lensing Analysis of PLCK G004.5$-$19.5, a Planck-Discovered
Cluster Hosting a Radio Relic at $z=0.52$: The recent discovery of a large number of galaxy clusters using the
Sunyaev-Zel'dovich (SZ) effect has opened a new era on the study of the most
massive clusters in the Universe. Multi-wavelength analyses are required to
understand the properties of these new sets of clusters, which are a sensitive
probe of cosmology. We aim at a multi-wavelength characterization of PLCK
G004.5$-$19.5, one of the most massive X-ray validated SZ effect-selected
galaxy clusters discovered by the Planck satellite. We have observed PLCK
G004.5$-$19.5 with GMOS on Gemini South for optical imaging and spectroscopy,
and performed a strong lensing analysis. We also searched for associated radio
emission in published catalogs. An analysis of the optical images confirms that
this is a massive cluster, with a dominant central galaxy (the BCG) and an
accompanying red sequence of galaxies, plus a $14''$-long strong lensing arc.
Longslit pectroscopy of 6 cluster members shows that the cluster is at
$z=0.516\pm0.002$. We also targeted the strongly lensed arc, and found $z_{\rm
arc}=1.601$. We use LensTool to carry out a strong lensing analysis, from which
we measure a median Einstein radius $\theta_E(z_s=1.6)\simeq30''$ and estimate
an enclosed mass $M_E=2.45_{-0.47}^{+0.45}\times10^{14}\,M_\odot$. By
extrapolating an NFW profile we find a total mass
$M_{500}^{SL}=4.0_{-1.0}^{+2.1}\times10^{14}M_\odot$. Including a constraint on
the mass from previous X-ray observations yields a slightly higher mass,
$M_{500}^{SL+X}=6.7_{-1.3}^{+2.6}\times10^{14}M_\odot$, marginally consistent
with the value from strong lensing alone. High-resolution radio images from
TGSS at 150~MHz reveal that PLCK G004.5$-$19.5 hosts a powerful radio relic on
scales $\lesssim500$ kpc. Emission at the same location is also detected in low
resolution images at 843~MHz and 1.4~GHz. This is one of the higher redshift
radio relics known to date. | astro-ph_CO |
Dark Energy Constraints in light of Pantheon SNe Ia, BAO, Cosmic
Chronometers and CMB Polarization and Lensing Data: To explore whether there is new physics going beyond the standard
cosmological model or not, we constrain seven cosmological models by combining
the latest and largest Pantheon Type Ia supernovae sample with the data
combination of baryonic acoustic oscillations, cosmic microwave background
radiation, Planck lensing and cosmic chronometers. We find that a spatially
flat universe is preferred in the framework of $\Lambda$CDM cosmology, that the
constrained equation of state of dark energy is very consistent with the
cosmological constant hypothesis, that there is no evidence of dynamical dark
energy, that there is no hint of interaction between dark matter and dark
energy in the dark sector of the universe, and that there does not exist the
sterile neutrinos in the neutrino sector of the universe. We also give the
95$\%$ limit of the total mass of three active neutrinos $\Sigma m_\nu<0.178$
eV. It is clear that there is no any departure from the standard cosmological
model based on current observational datasets. | astro-ph_CO |
A unified solution to the small scale problems of the $Λ$CDM model: We study, by means of the model proposed in Del Popolo (2009), the effect of
baryon physics on the small scale problems of the CDM model. We show that,
using this model, the cusp/core problem, the missing satellite problem (MSP),
the Too Big to Fail (TBTF) problem, and the angular momentum catastrophe can be
reconciled with observations. Concerning the cusp/core problem, the interaction
among dark matter (DM) and baryonic clumps of 1% the mass of the halo, through
dynamical friction (DF), is able to flatten the inner cusp of the density
profiles. We moreover assume that haloes form primarily through quiescent
accretion, in agreement with the spherical collapse model (SCM)-secondary
infall model (SIM) prescriptions. The results of this paper follow from the two
assumptions above. Concerning the MSP and TBTF problem, applying to the Via
Lactea II (VL2) subhaloes a series of corrections similar to those of Brooks et
al. (2013), namely applying a Zolotov et al. (2012)-like correction obtained
with our model, and further correcting for the UV heating and tidal stripping,
we obtain that the number of massive, luminous satellites is in agreement with
the number observed in the MW. The model also produces an angular momentum
distribution in agreement with observations, that is with the distribution of
the angular spin parameter and angular momentum of the dwarfs studied by van
den Bosch, Burkert, & Swaters (2001). In conclusion, the small scale problems
of the CDM model can all be solved by introducing baryon physics. | astro-ph_CO |
Galaxy And Mass Assembly (GAMA): A deeper view of the mass, metallicity,
and SFR relationships: A full appreciation of the role played by gas metallicity (Z), star-formation
rate (SFR), and stellar mass is fundamental to understanding how galaxies form
and evolve. The connections between these three parameters at different
redshifts significantly affect galaxy evolution, and thus provide important
constraints for galaxy evolution models. Using data from the Sloan Digital Sky
Survey-Data Release 7 (SDSS-DR7) and the Galaxy and Mass Assembly (GAMA)
surveys we study the relationships and dependencies between SFR, Z, and stellar
mass, as well as the Fundamental Plane for star-forming galaxies. We combine
both surveys using volume-limited samples up to a redshift of z ~ 0.36. The
GAMA and SDSS surveys complement each other when analyzing the relationships
between SFR, Mass and Z. We present evidence for SFR and metallicity evolution
to z ~ 0.2. We study the dependencies between SFR, Mass, Z, and specific
star-formation rate (SSFR) on the M-Z, M-SFR, M-SSFR, Z-SFR, and Z-SSFR
relations, finding strong correlations between all. Based on those
dependencies, we propose a simple model that allows us to explain the different
behaviour observed between low and high mass galaxies. Finally, our analysis
allows us to confirm the existence of a Fundamental Plane, for which Mass=f(Z,
SFR) in star-forming galaxies. | astro-ph_CO |
Modeling the Nuclear Infrared Spectral Energy Distribution of Type II
Active Galactic Nuclei: We present results from model fitting to the Spectral Energy Distribution
(SED) of a homogeneous sample of Seyfert II galaxies drawn from the $12\mu$m
Galaxy Sample. Imaging and nuclear flux measurements are presented in an
accompanying paper (Videla et al., 2013). Here we add IRS Spitzer observations
to further constrain the SEDs after careful subtraction of a starburst
component. We use the library of CLUMPY torus models from Nenkova et
al.~(2008ab) and also test the two-phase models recently produced by Stalevski
et al.~(2012). We find that photometric and spectroscopic observations in the
mid-IR (>5mu) are crucial to properly constrain the best-fit torus models.
About half of our sources show clear near-IR excess of their SEDs above the
best fit models. This problem can be less severe when using the Stalevski et
al.~(2012) models. It is not clear what is the nature of this emission since
best fitted black body temperatures are very high (~1700-2500 K) and the Type
II classification of our sources would correspond to a small probability to
peer directly into the hottest regions of the torus. Crucially, the derived
torus parameters when using CLUMPY models are quite robust,, independently of
whether the sources require an additional black body component or not. Our
findings suggest that tori are characterized by N_0 > 5, sigma > 40, tau < 25,
i > 40 degrees, Y < 50 and A_v^los ~ 100-300. From these we can determine that
typical torus sizes and masses of 0.1-5.0 pc and 10^{4-6} M_\odot. We find
tentative evidence that those nuclei with a detected Hidden Broad Line Regions
are characterized by lower levels of extinction than those without one.
Finally, we find no correlation between the torus properties and the presence
of circumnuclear or more global star-formation. | astro-ph_CO |
Molecular gas in the inner 0.7kpc-radius ring of M31: The study of the gas kinematic in the central 1.5kpc x 1.5kpc region of M31
has revealed several surprises. The starting point of this investigation was
the detection at the IRAM-30m telescope of molecular gas with very large line
splittings up to 260km/s within the beam (40 pc). In this region, which is
known for its low gas content, we also detect an ionised gas outflow in the
circumnuclear region (within 75pc from the centre) extending to the whole area
in X-ray. Relying on atomic, ionised, and molecular gas, we account for most
observables with a scenario that assumes that a few hundreds Myr ago, M31
underwent a frontal collision with M32, which triggered some star-formation
activity in the centre, and this collision explains the special configuration
of M31 with two rings observed at 0.7kpc and 10kpc. The inner disc (whose
rotation is detected in HI and ionised gas ([NII])) has thus been tilted
(inclination: 43deg, PA: 70deg) with respect to the main disc (inclination:
77deg, PA: 35deg). One of the CO velocity components is compatible with this
inner disc, while the second one comes from a tilted ring-like material with
40deg inclination and PA=-35deg. The relic star formation estimated by previous
works to have occurred more than 100Myr ago could have been triggered by the
collision and could be linked to the outflow detected in the ionised gas. Last,
we demonstrate that the amplitude of the line splittings detected in CO centred
on the systemic velocity with a relatively high spatial resolution (40pc)
cannot be accounted for by a possible weak bar that is roughly aligned along
the minor axis. Although M31 has a triaxial bulge, there are no bar indicators
in the gas component (photometry, no strong skewness of the isovelocities,
etc.). | astro-ph_CO |
Isotropy analyses of the Planck convergence map: The presence of matter in the path of relic photons causes distortions in the
angular pattern of the cosmic microwave background (CMB) temperature
fluctuations, modifying their properties in a slight but measurable way.
Recently, the Planck Collaboration released the estimated convergence map, an
integrated measure of the large-scale matter distribution that produced the
weak gravitational lensing (WL) phenomenon observed in Planck CMB data. We
perform exhaustive analyses of this convergence map calculating the variance in
small and large regions of the sky, but excluding the area masked due to
galactic contaminations, and compare them with the features expected in the set
of simulated convergence maps, also released by the Planck collaboration. Our
goal is to search for sky directions or regions where the WL imprints anomalous
signatures to the variance estimator revealed through a $\chi^2$ analyses at a
statistically significant level. In the local analysis of the Planck
convergence map we identified 8 patches of the sky in disagreement, in more
than 2$\sigma$, with what is observed in the average of the simulations. In
contrast, in the large regions analysis we found no statistically significant
discrepancies, but, interestingly, the regions with the highest $\chi^2$ values
are surrounding the ecliptic poles. Thus, our results show a good agreement
with the features expected by the $\Lambda$CDM concordance model, as given by
the simulations. Yet, the outliers regions found here could suggest that the
data still contain residual contamination, like noise, due to over- or
under-estimation of systematic effects in the simulation data set. | astro-ph_CO |
The SDSS Coadd: 275 deg^2 of Deep SDSS Imaging on Stripe 82: We present details of the construction and characterization of the coaddition
of the Sloan Digital Sky Survey Stripe 82 \ugriz\ imaging data. This survey
consists of 275 deg$^2$ of repeated scanning by the SDSS camera of $2.5\arcdeg$
of $\delta$ over $-50\arcdeg \le \alpha \le 60\arcdeg$ centered on the
Celestial Equator. Each piece of sky has $\sim 20$ runs contributing and thus
reaches $\sim2$ magnitudes fainter than the SDSS single pass data, i.e. to
$r\sim 23.5$ for galaxies. We discuss the image processing of the coaddition,
the modeling of the PSF, the calibration, and the production of standard SDSS
catalogs. The data have $r$-band median seeing of 1.1\arcsec, and are
calibrated to $\le 1%$. Star color-color, number counts, and psf size vs
modelled size plots show the modelling of the PSF is good enough for precision
5-band photometry. Structure in the psf-model vs magnitude plot show minor psf
mis-modelling that leads to a region where stars are being mis-classified as
galaxies, and this is verified using VVDS spectroscopy. As this is a wide area
deep survey there are a variety of uses for the data, including galactic
structure, photometric redshift computation, cluster finding and cross
wavelength measurements, weak lensing cluster mass calibrations, and cosmic
shear measurements. | astro-ph_CO |
Imprint of thawing scalar fields on large scale galaxy overdensity: We investigate the observed galaxy power spectrum for the thawing class of
scalar field models taking into account various general relativistic
corrections that occur on very large scales. We consider the full general
relativistic perturbation equations for the matter as well as the dark energy
fluid. We form a single autonomous system of equations containing both the
background and perturbed equations of motion which we subsequently solve for
different scalar field potentials. First we study the percentage deviation from
$\Lambda$CDM model for different cosmological parameters as well as in the
observed galaxy power spectra on different scales in scalar field models for
various choices of scalar field potentials. Interestingly the difference in
background expansion results enhancement of power from $\Lambda$CDM on small
scales whereas the inclusion of GR corrections results the suppression of power
from $\Lambda$CDM on large scales. This can be useful to distinguish scalar
field models from $\Lambda$CDM with future optical/radio surveys. We also
compare the observed galaxy power spectra for tracking and thawing types of
scalar field using some particular choices for the scalar field potentials. We
show that thawing and tracking models can have large differences in observed
galaxy power spectra on large scales and for smaller redshifts due to different
GR effects. But on smaller scales and for larger redshifts, the difference is
small and is mainly due to difference in background expansion. | astro-ph_CO |
A gravitational-wave limit on the Chandrasekhar mass of dark matter: We explore a new paradigm to study dissipative dark matter models using
gravitational-wave observations. We consider a dark atomic model which predicts
the formation of binary black holes such as GW190425 while obeying constraints
from large-scale structure, and improving on the missing satellite problem.
Using LIGO and Virgo gravitational-wave data from 12th September 2015 to 1st
October 2019, we show that interpreting GW190425 as a dark matter black-hole
binary limits the Chandrasekhar mass for dark matter to be below 1.4 $M_\odot$
at $> 99.9\%$ confidence implying that the dark proton is heavier than 0.95
GeV, while also suggesting that the molecular energy-level spacing of dark
molecules lies near $10^{-3}$ eV and constraining the cooling rate of dark
matter at low temperatures. | astro-ph_CO |
Heating of the intergalactic medium by the cosmic microwave background
during cosmic dawn: The intergalactic medium is expected to be at its coldest point before the
formation of the first stars in the universe. Motivated by recent results from
the EDGES experiment, we revisit the standard calculation of the kinetic
temperature of the neutral gas through this period. When the first ultraviolet
(UV) sources turn on, photons redshift into the Lyman lines of neutral hydrogen
and repeatedly scatter within the Lyman-$\alpha$ line. They heat the gas via
atomic recoils, and, through the Wouthuysen-Field effect, set the spin
temperature of the 21-cm hyperfine (spin-flip) line of atomic hydrogen in
competition with the resonant cosmic microwave background (CMB) photons. We
show that the Lyman-$\alpha$ photons also mediate energy transfer between the
CMB photons and the thermal motions of the hydrogen atoms. In the absence of
X-ray heating, this new mechanism is the major correction to the temperature of
the adiabatically cooling gas ($\sim 10 \%$ at $z=17$), and is several times
the size of the heating rate found in previous calculations. We also find that
the effect is more dramatic in non-standard scenarios that either enhance the
radio background above the CMB or invoke new physics to cool the gas in order
to explain the EDGES results. The coupling with the radio background can reduce
the depth of the 21-cm absorption feature by almost a factor of two relative to
the case with no sources of heating, and prevent the feature from developing a
flattened bottom. As an inevitable consequence of the UV background that
generates the absorption feature, this heating should be accounted for in any
theoretical prediction. | astro-ph_CO |
The formation of disks in massive spiral galaxies: The flatness of the rotation curve inside spiral galaxies is interpreted as
the imprint of a halo of invisible matter. Using the deepest observations of
distant galaxies, we have investigated how large disks could have been formed.
Observations include spatially resolved kinematics, detailed morphologies and
photometry from UV to mid-IR. Six Giga-years ago, half of the present-day
spirals had anomalous kinematics and morphologies that considerably affect the
scatter of the Tully Fisher relation. All anomalous galaxies can be modelled
through gas-rich, major mergers that lead to a rebuilt of a new disk. The
spiral-rebuilding scenario is proposed as a new channel to form large disks in
present-day spirals and it accounts for all the observed evolutions since the
last 6 Giga-years. A large fraction of the star formation is linked to merging
events during their whole durations. | astro-ph_CO |
Prospects of testing late-time cosmology with weak lensing of
gravitational waves and galaxy surveys: We investigate the synergy of upcoming galaxy surveys and gravitational wave
(GW) experiments in constraining late-time cosmology, examining the
cross-correlations between the weak lensing of gravitational waves (GW-WL) and
the galaxy fields. Without focusing on any specific GW detector configuration,
we benchmark the requirements for the high-precision measurement of
cosmological parameters by considering several scenarios, varying the number of
detected GW events and the uncertainty on the inference of the source
luminosity distance and redshift. We focus on $\Lambda$CDM and scalar-tensor
cosmologies, using the Effective Field Theory formalism as a unifying language.
We find that, in some of the explored setups, GW-WL contributes to the galaxy
signal by doubling the accuracy on non-$\Lambda$CDM parameters, allowing in the
most favourable scenarios to reach even percent and sub-percent level bounds.
Though the most extreme cases presented here are likely beyond the
observational capabilities of currently planned individual GW detectors, we
show nonetheless that - provided that enough statistics of events can be
accumulated - GW-WL offers the potential to become a cosmological probe
complementary to LSS surveys, particularly for those parameters that cannot be
constrained by other GW probes such as standard sirens. | astro-ph_CO |
Mapping the Clumpy Structures within Submillimeter Galaxies using
Laser-Guide Star Adaptive Optics Spectroscopy: We present the first integral-field spectroscopic observations of
high-redshift submillimeter-selected galaxies (SMGs) using Laser Guide Star
Adaptive Optics (LGS-AO). We target H-alpha emission of three SMGs at redshifts
z~1.4-2.4 with the OH-Suppressing Infrared Imaging Spectrograph (OSIRIS) on
Keck. The spatially-resolved spectroscopy of these galaxies reveals unresolved
broad H-alpha line regions (FWHM>1000 km/s) likely associated with an AGN and
regions of diffuse star formation traced by narrow-line H-alpha emission
(FWHM<500 km/s) dominated by multiple Halpha-bright stellar clumps, each
contributing 1-30% of the total clump-integrated H-alpha emission. We find that
these SMGs host high star-formation rate surface densities, similar to local
extreme sources, such as circumnuclear starbursts and luminous infrared
galaxies. However, in contrast to these local environments, SMGs appear to be
undergoing such intense activity on significantly larger spatial scales as
revealed by extended H-alpha emission over 4-16 kpc. H-alpha kinematics show no
evidence of ordered global motion as would be found in a disk, but rather large
velocity offsets (~few x 100 km/s) between the distinct stellar clumps.
Together with the asymmetric distribution of the stellar clumps around the AGN
in these objects, it is unlikely that we are unveiling a clumpy disk structure
as has been suggested in other high-redshift populations of star-forming
galaxies. The SMG clumps in this sample may correspond to remnants of
originally independent gas-rich systems that are in the process of merging,
hence triggering the ultraluminous SMG phase. | astro-ph_CO |
Stochastic gravitational waves from cosmic string loops in scaling: If cosmic strings are formed in the early universe, their associated loops
emit gravitational waves during the whole cosmic history and contribute to the
stochastic gravitational wave background at all frequencies. We provide a new
estimate of the stochastic gravitational wave spectrum by considering a
realistic cosmological loop distribution, in scaling, as it can be inferred
from Nambu-Goto numerical simulations. Our result takes into account various
effects neglected so far. We include both gravitational wave emission and
backreaction effects on the loop distribution and show that they produce two
distinct features in the spectrum. Concerning the string microstructure, in
addition to the presence of cusps and kinks, we show that gravitational wave
bursts created by the collision of kinks could dominate the signal for wiggly
strings, a situation which may be favoured in the light of recent numerical
simulations. In view of these new results, we propose four prototypical
scenarios, within the margin of the remaining theoretical uncertainties, for
which we derive the corresponding signal and estimate the constraints on the
string tension put by both the LIGO and European Pulsar Timing Array (EPTA)
observations. The less constrained of these scenarios is shown to have a string
tension GU < 7.2 x 10^{-11}, at 95% of confidence. Smooth loops carrying two
cusps per oscillation verify the two-sigma bound GU < 1.0 x 10^{-11} while the
most constrained of all scenarios describes very kinky loops and satisfies GU <
6.7 x 10^{-14} at 95% of confidence. | astro-ph_CO |
Gravity at the horizon: on relativistic effects, CMB-LSS correlations
and ultra-large scales in Horndeski's theory: We address the impact of consistent modifications of gravity on the largest
observable scales, focusing on relativistic effects in galaxy number counts and
the cross-correlation between the matter large scale structure (LSS)
distribution and the cosmic microwave background (CMB). Our analysis applies to
a very broad class of general scalar-tensor theories encoded in the Horndeski
Lagrangian and is fully consistent on linear scales, retaining the full
dynamics of the scalar field and not assuming quasi-static evolution. As
particular examples we consider self-accelerating Covariant Galileons,
Brans-Dicke theory and parameterizations based on the effective field theory of
dark energy, using the \hiclass\, code to address the impact of these models on
relativistic corrections to LSS observables. We find that especially effects
which involve integrals along the line of sight (lensing convergence, time
delay and the integrated Sachs-Wolfe effect -- ISW) can be considerably
modified, and even lead to $\mathcal{O}(1000\%)$ deviations from General
Relativity in the case of the ISW effect for Galileon models, for which
standard probes such as the growth function only vary by $\mathcal{O}(10\%)$.
These effects become dominant when correlating galaxy number counts at
different redshifts and can lead to $\sim 50\%$ deviations in the total signal
that might be observable by future LSS surveys. Because of their integrated
nature, these deep-redshift cross-correlations are sensitive to modifications
of gravity even when probing eras much before dark energy domination. We
further isolate the ISW effect using the cross-correlation between LSS and CMB
temperature anisotropies and use current data to further constrain Horndeski
models (abridged). | astro-ph_CO |
The C-Band All-Sky Survey: The C-Band All-Sky Survey (C-BASS) is an experiment to image the whole sky in
intensity and polarization at 5 GHz. The primary aim of C-BASS is to provide
low-frequency all-sky maps of the Galactic emission which will enable accurate
component separation analysis of both existing and future CMB intensity and
polarization imaging surveys. Here we present an overview of the experiment and
an update on the current status of observations. We present simulation results
showing the expected improvement in the recovery of CMB and foreground signals
when including C-BASS data as an additional low-frequency channel, both for
intensity and polarization. We also present preliminary results from the
northern part of the sky survey. | astro-ph_CO |
Transverse velocities and matter gradient correlations: a new signal and
a new challenge to moving-lens analyses: An observer that is moving towards a high-density region sees, on average, a
higher matter density and more foreground-emitting sources ahead than behind
themself. Consequently, the average abundance and luminosity of objects
producing cosmological signals around an in-falling dark matter halo is larger
in the direction of the halo's motion. In this Letter, we demonstrate this
effect from simulated cosmological maps of the thermal Sunyaev Zel'dovich
effect and the cosmic infrared background. We find that, for a wide range of
halo masses and redshifts, oriented stacked profiles of these foregrounds show
significant, potentially detectable gradients aligned with the transverse
velocity of halos. The signal depends on the halo's mass and redshift, as well
as the physical properties of the cosmic web surrounding the halos. We show
that this signal is sufficiently prominent to be detected in future Cosmic
Microwave Background experiments, therefore offering a new window into the
study of cosmological structures. We argue that the dipolar morphological
structure of this signal, its orientation, as well as its overall large
amplitude, constitute a challenge for the detection of the transverse velocity
through the study of the moving lens effect for stacked halos. | astro-ph_CO |
On the Transverse-Traceless Projection in Lattice Simulations of
Gravitational Wave Production: It has recently been pointed out that the usual procedure employed in order
to obtain the transverse-traceless (TT) part of metric perturbations in lattice
simulations was inconsistent with the fact that those fields live in the
lattice and not in the continuum. It was claimed that this could lead to a
larger amplitude and a wrong shape for the gravitational wave (GW) spectra
obtained in numerical simulations of (p)reheating. In order to address this
issue, we have defined a consistent prescription in the lattice for extracting
the TT part of the metric perturbations. We demonstrate explicitly that the GW
spectra obtained with the old continuum-based TT projection only differ
marginally in amplitude and shape with respect to the new lattice-based ones.
We conclude that one can therefore trust the predictions appearing in the
literature on the spectra of GW produced during (p)reheating and similar
scenarios simulated on a lattice. | astro-ph_CO |
A boosted gravitational-wave background for primordial black holes with
broad mass distributions and thermal features: Primordial black holes (PBHs) with a wide mass distribution imprinted by the
thermal history of the Universe, which naturally produces a high peak at the
solar mass scale, could explain the gravitational-wave events seen by
LIGO/Virgo and up to the totality of the dark matter. We show that compared to
monochromatic or log-normal mass functions, the gravitational wave backgrounds
(GWBs) from early PBH binaries and from late binaries in clusters are strongly
enhanced at low frequency and could even explain the NANOGrav observations.
This enhancement comes from binaries with very low mass ratios, involving
solar-mass and intermediate-mass PBHs at low frequency, solar-mass and
subsolar-mass at high frequency. LISA could distinguish the various models,
while in the frequency band of ground-based detectors, we find that the GWB
from early binaries is just below the current LIGO/Virgo limits and above the
astrophysical background, if they also explain black hole mergers. The GWB from
binaries in clusters is less boosted but has a different spectral index than
for neutron stars, astrophysical black holes or early PBH binaries. It is
detectable with Einstein Telescope or even with the LIGO/Virgo design
sensitivity. | astro-ph_CO |
An inflation model for massive primordial black holes to interpret the
JWST observations: The first observations of the James Webb Space Telescope (JWST) have
identified six massive galaxy candidates with the stellar masses $M_\ast\gtrsim
10^{10}\,M_\odot$ at high redshifts $7.4\lesssim z\lesssim 9.1$, with two most
massive high-$z$ objects having the cumulative comoving number densities
$n_{\rm G}$ up to $1.6\times 10^{-5}\, {\rm Mpc}^{-3}$. The presence of such
massive sources in the early universe challenges the standard $\Lambda$CDM
model since the needed star formation efficiency is unrealistically high. This
tension can be alleviated via the accretion of massive primordial black holes
(PBHs). In this work, with the updated data from the first JWST observations,
we find that the PBHs with mass $10^8\,M_\odot\lesssim M_{\rm PBH}\lesssim
10^{11}\,M_\odot$ can act as the seeds of extremely massive galaxies even with
a low abundance $10^{-7}\lesssim f_{\rm PBH}\lesssim 10^{-3}$. We construct an
ultraslow-roll inflation model and investigate its possibility of producing the
required PBHs. We explore the model in two cases, depending on whether there is
a perfect plateau on the inflaton potential. If the plateau is allowed to
incline slightly, our model can produce the PBHs that cover the required PBH
mass and abundance range to explain the JWST data. | astro-ph_CO |
The velocity shear and vorticity across redshifts and non-linear scales: The evolution of the large scale distribution of matter in the universe is
often characterized by the density field. Here we take a complimentary approach
and characterize it using the cosmic velocity field, specifically the
deformation of the velocity field. The deformation tensor is decomposed into
its symmetric component (known as the "shear tensor") and its anti-symmetric
part (the "vorticity"). Using a high resolution cosmological simulation we
examine the relative orientations of the shear and the vorticity as a function
of spatial scale and redshift. The shear is found to be remarkable stable to
the choice of scale, while the vorticity is found to quickly decay with
increasing spatial scale or redshift. The vorticity emerges out of the linear
regime randomly oriented with respect to the shear eigenvectors. Non-linear
evolution drives the vorticity to lie within the plane defined by the
eigenvector of the fastest collapse. Within that plane the vorticity first gets
aligned with the middle eigenvector and then it moves to be preferentially
aligned with the third eigenvector, of slowest collapse. Finally a scale of
"non-linearity" to be used when calculating properties of the non-linear
deformation tensor at different redshifts is suggested. | astro-ph_CO |
Constraining Chameleon screening using galaxy cluster dynamics: We constrain the Chameleon \textit{screening} mechanism in galaxy clusters,
essentially obtaining limits on the coupling strength $\beta$ and the
asymptotic value of the field $\phi_{\infty}$. For this purpose, we utilized a
collection of the 9 relaxed galaxy clusters within the X-COP compilation in the
redshift range of $z \le 0.1$. We implement the formalism assuming an NFW mass
profile for the dark matter density and study the degeneracy present between
the mass $\M$ and the chameleon coupling with a high degree of improvement in
the constraints for excluded parameter space. We recast our constrain to an
upper limit on the scalaron field in \fofr sub-class of models of $|f_{R0}|\le
9.2\times 10^{-6}$, using all the nine clusters and $|f_{R0}|\le 1.2\times
10^{-5}$ using only 5 clusters with WL priors taken into account, at a $95\%$
confidence level. These bounds are consistent with existing limits in the
literature and tighter than the constraints obtained with the same method by
previous studies. | astro-ph_CO |
XMM-{\em Newton} and FUSE Tentative Evidence for a WHIM filament along
the Line of Sight to PKS~0558-504: We present a possible OVIII X-ray absorption line at $z=0.117 \pm 0.001$
which, if confirmed, will be the first one associated with a broad HI Ly$\beta$
(BLB: FWHM=$160^{+50}_{-30}$ km s$^{-1}$) absorber. The absorber lies along the
line of sight to the nearby ($z=0.1372$) Seyfert 1 galaxy PKS~0558-504,
consistent with being a WHIM filament. The X-ray absorber is marginally
detected in two independent XMM-Newton spectra of PKS~0558-504, a long $\sim
600$ ks Guest-Observer observation and a shorter, $\sim 300$ ks total,
calibration observation, with a combined single line statistical significance
of 2.8$\sigma$ (2.7$\sigma$ and 1.2$\sigma$ in the two spectra, respectively).
When fitted with our self-consistent hybrid-photoionization WHIM models, the
combined XMM-{\em Newton} spectrum is consistent with the presence of OVIII
K$\alpha$ at $z=(0.117 \pm 0.001)$. This model gives best fitting temperature
and equivalent H column density of the absorber of log$T=6.56_{-0.17}^{+0.19}$
K, and logN$_H=(21.5 \pm 0.3) (Z/Z_{0.01\odot})^{-1}$ cm$^{-2}$. The
statistical sigificance of this single X-ray detection is increased by the
detection of broad and complex HI Ly$\beta$ absorption in archival FUSE spectra
of PKS~0558-504, at redshifts $z=0.1183 \pm 0.0001$ consistent with the
best-fitting redshift of the X-ray absorber. The single line statistical
significance of this line is 4.1$\sigma$ (3.7$\sigma$ if systematics are
considered), and thus the combined (HI+OVIII) statistical significance of the
detection is of 5.0$\sigma$.
The detection of both metal and H lines at a consistent redshift, in this hot
absorbing system, allows us to speculate on its metallicity. By associating the
bulk of the X-ray absorber with the BLB line detected in the FUSE spectrum at
$z_{BLB}=0.1183 \pm 0.0001$, we obtain a metallicity of 1-4\% Solar. | astro-ph_CO |
Effects of dark matter pressure on the ellipticity of cosmic voids: The dark matter in or around the cosmic voids affects their shapes. The
thermodynamical properties of dark matter can alter the ellipticity of cosmic
voids. Here, applying the dark matter equation of state from the
pseudo-isothermal density profile of galaxies, we explore the shapes of cosmic
voids with the non zero pressure dark matter in different cosmological models.
For this purpose, the linear growth of density perturbation in the presence of
dark matter pressure is calculated. In addition, the matter transfer function
considering the dark matter pressure, as well as the linear matter power
spectrum in the presence of the dark matter pressure are presented. Employing
these results, the probability density distribution for the ellipticity of
cosmic voids with the non zero pressure dark matter is calculated. Our
calculations verify that the dark matter pressure leads to more spherical
shapes for the cosmic voids. | astro-ph_CO |
The intergalactic medium in the cosmic web: The intergalactic medium (IGM) accounts for ~90% of baryons at all epochs and
yet its three dimensional distribution in the cosmic web remains mostly
unknown. This is so because the only feasible way to observe the bulk of the
IGM is through intervening absorption line systems in the spectra of bright
background sources, which limits its characterization to being one-dimensional.
Still, an averaged three dimensional picture can be obtained by combining and
cross-matching multiple one-dimensional IGM information with three-dimensional
galaxy surveys. Here, we present our recent and current efforts to map and
characterize the IGM in the cosmic web using galaxies as tracers of the
underlying mass distribution. In particular, we summarize our results on: (i)
IGM around star-forming and non-star-forming galaxies; (ii) IGM within and
around galaxy voids; and (iii) IGM in intercluster filaments. With these
datasets, we can directly test the modern paradigm of structure formation and
evolution of baryonic matter in the Universe. | astro-ph_CO |
Dynamical Delays Between Starburst and AGN Activity in Galaxy Nuclei: Observations of AGN have suggested a possible delay between the peak of star
formation (on some scale) and AGN activity. Inefficient fueling (and/or
feedback) from fast stellar winds has been invoked to explain this, but we
argue this is unlikely in bright systems accreting primarily cold dense gas. We
show that such a delay can arise even in bright quasars for purely dynamical
reasons. If some large-scale process produces rapid inflow, smaller scales will
quickly become gas-dominated. As the gas density peaks, so does the SFR.
However, gravitational torques which govern further inflow are relatively
inefficient in gas-dominated systems; as more gas is turned into stars, the
stars provide an efficient angular momentum sink allowing more rapid inflow.
Moreover, the gas provided to the central regions in mergers or strong disk
instabilities will typically be ~100 times larger than that needed to fuel the
BH; the system is effectively in the 'infinite gas supply' limit. BH growth can
therefore continue for some time while the gas supply exhausts, until it has
significantly depleted to the point where the BH is finally 'starved.' Both of
these effects act together with comparable magnitude, and mean that the peak of
BH growth can lag the peak in the SFR measured at a given scale by a timescale
corresponding to the gas exhaustion time on that scale (~ 10-100 local
dynamical times). This predicts that the inferred delay will vary in a specific
manner with the radius over which the star formation rate is measured. We
discuss possible implications for the role of AGN feedback in suppressing star
formation activity. | astro-ph_CO |
A flexible subhalo abundance matching model for galaxy clustering in
redshift space: We develop an extension of subhalo abundance matching (SHAM) capable of
accurately reproducing the real and redshift-space clustering of galaxies in a
state-of-the-art hydrodynamical simulation. Our method uses a low-resolution
gravity-only simulation and it includes orphan and tidal disruption
prescriptions for satellite galaxies, and a flexible amount of galaxy assembly
bias. Furthermore, it includes recipes for star formation rate (SFR) based on
the dark matter accretion rate. We test the accuracy of our model against
catalogues of stellar-mass- and SFR-selected galaxies in the TNG300
hydrodynamic simulation. By fitting a small number of free parameters, our
extended SHAM reproduces the projected correlation function and redshift-space
multipoles for number densities $10^{-3} - 10^{-2}\, h^{3}{\rm Mpc}^{-3}$, at
$z=1$ and $z=0$, and for scales $r \in [0.3 - 20] h^{-1}{\rm Mpc}$.
Simultaneously, the SHAM results also retrieve the correct halo occupation
distribution, the level of galaxy assembly bias, and higher-order statistics
present in the TNG300 galaxy catalogues. As an application, we show that our
model simultaneously fits the projected correlation function of the SDSS in 3
disjoint stellar mass bins, with an accuracy similar to that of TNG300
galaxies. This SHAM extension can be used to get accurate clustering prediction
even when using low and moderate-resolution simulations. | astro-ph_CO |
Impact of blending on weak lensing measurements with the Vera C. Rubin
Observatory: Upcoming deep optical surveys such as the Vera C. Rubin Observatory Legacy
Survey of Space and Time will scan the sky to unprecedented depths and detect
billions of galaxies. This amount of detections will however cause the apparent
superposition of galaxies on the images, called blending, and generate a new
systematic error due to the confusion of sources. As consequences, the
measurements of individual galaxies properties such as their redshifts or
shapes will be impacted, and some galaxies will not be detected. However,
galaxy shapes are key quantities, used to estimate masses of large scale
structures, such as galaxy clusters, through weak gravitational lensing. This
work presents a new catalog matching algorithm, called friendly, for the
detection and characterization of blends in simulated LSST data for the DESC
Data Challenge 2. By identifying a specific type of blends, we show that
removing them from the data may partially correct the amplitude of the
$\Delta\Sigma$ weak lensing profile that could be biased low by around 20% due
to blending. This would result in impacting clusters weak lensing mass estimate
and cosmology. | astro-ph_CO |
Low mass WIMP search with EDELWEISS-III: First Results: We present the first search for low mass WIMPs using the Germanium bolometers
of the EDELWEISS-III experiment. Upgrades to the detectors and the electronics
enhance the background discrimination and the low energy sensitivity with
respect to EDELWEISS-II. A multivariate analysis is implemented to fully
exploit the detector's potential, reaching a sensitivity of 1.6 $\times
10^{-5}$ pb for a WIMP mass of 7 GeV/c$^2$ with a fraction of the data set,
unblinded for background modeling and analysis tuning. | astro-ph_CO |
HERschel Observations of Edge-on Spirals (HEROES). I: Far-infrared
morphology and dust mass determination: Context. Edge-on spiral galaxies with prominent dust lanes provide us with an
excellent opportunity to study the distribution and properties of the dust
within them. The HEROES project was set up to observe a sample of seven large
edge-on galaxies across various wavelengths for this investigation.
Aims. Within this first paper, we present the Herschel observations and
perform a qualitative and quantitative analysis on them, and we derive some
global properties of the far infrared and submillimetre emission.
Methods. We determine horizontal and vertical profiles from the Herschel
observations of the galaxies in the sample and describe the morphology.
Modified black-body fits to the global fluxes, measured using aperture
photometry, result in dust temperatures and dust masses. The latter values are
compared to those that are derived from radiative transfer models taken from
the literature.
Results. On the whole, our Herschel flux measurements agree well with
archival values. We find that the exponential horizontal dust distribution
model often used in the literature generally provides a good description of the
observed horizontal profiles. Three out of the seven galaxies show signatures
of extended vertical emission at 100 and 160 {\mu}m at the 5{\sigma} level, but
in two of these it is probably due to deviations from an exactly edge-on
orientation. Only for NGC 4013, a galaxy in which vertically extended dust has
already been detected in optical images, we can detect vertically extended
dust, and the derived scaleheight agrees with the value estimated through
radiative transfer modelling. Our analysis hints at a correlation between the
dust scaleheight and its degree of clumpiness, which we infer from the
difference between the dust masses as calculated from modelling of optical data
and from fitting the spectral energy distribution of Herschel datapoints. | astro-ph_CO |
The starburst-AGN connection in the merger galaxy Mrk 938: an infrared
and X-ray view: Mrk938 is a luminous infrared galaxy in the local Universe believed to be the
remnant of a galaxy merger. It shows a Seyfert 2 nucleus and intense star
formation according to optical spectroscopic observations. We have studied this
galaxy using new Herschel far-IR imaging data in addition to archival X-ray,
UV, optical, near-IR and mid-IR data. Mid- and far-IR data are crucial to
characterise the starburst contribution, allowing us to shed new light on its
nature and to study the coexistence of AGN and starburst activity in the local
Universe. The decomposition of the mid-IR Spitzer spectrum shows that the AGN
bolometric contribution to the mid-IR and total infrared luminosity is small
(Lbol(AGN)/LIR~0.02), which agrees with previous estimations. We have
characterised the physical nature of its strong infrared emission and
constrained it to a relatively compact emitting region of <2kpc. It is in this
obscured region where most of the current star formation activity is taking
place as expected for LIRGs. We have used Herschel imaging data for the first
time to constrain the cold dust emission with unprecedented accuracy. We have
fitted the integrated far-IR spectral energy distribution and derived the
properties of the dust, obtaining a dust mass of 3x10^7Msun. The far-IR is
dominated by emission at 35K, consistent with dust heated by the on-going star
formation activity. | astro-ph_CO |
Modelling the dusty universe II: The clustering of
submillimetre-selected galaxies: We combine the GALFORM semi-analytical model of galaxy formation, which
predicts the star formation and merger histories of galaxies, the GRASIL
spectro-photometric code, which calculates the spectral energy distributions
(SEDs) of galaxies self-consistently including reprocessing of radiation by
dust, and artificial neural networks (ANN), to investigate the clustering
properties of galaxies selected by their emission at submillimetre wavelengths
(SMGs). We use the Millennium Simulation to predict the spatial and angular
distribution of SMGs. At redshift z = 2, we find that these galaxies are
strongly clustered, with a comoving correlation length of r0 = 5.6 \pm 0.9
Mpc/h for galaxies with 850{\mu}m flux densities brighter than 5 mJy, in
agreement with observations. We predict that at higher redshifts these galaxies
trace denser and increasingly rarer regions of the universe. We present the
predicted dependence of the clustering on luminosity, submillimetre colour,
halo and total stellar masses. Interestingly, we predict tight relations
between correlation length and halo and stellar masses, independent of sub-mm
luminosity. | astro-ph_CO |
Probing the time dependence of dark energy: A new method to investigate a possible time-dependence of the dark energy
equation of state $w$ is proposed. We apply this methodology to two of the most
recent data sets of type Ia supernova (Union2 and SDSS) and the baryon acoustic
oscillation peak at $z = 0.35$. For some combinations of these data, we show
that there is a clear departure from the standard $\Lambda$CDM model at
intermediary redshifts, although a non-evolving dark energy component ($dw/dz =
0$) cannot be ruled out by these data. The approach developed here may be
useful to probe a possible evolving dark energy component when applied to
upcoming observational data. | astro-ph_CO |
Mocking the Weak Lensing universe: the LensTools python computing
package: We present a newly developed software package which implements a wide range
of routines frequently used in Weak Gravitational Lensing (WL). With the
continuously increasing size of the WL scientific community we feel that easy
to use Application Program Interfaces (APIs) for common calculations are a
necessity to ensure efficiency and coordination across different working
groups. Coupled with existing open source codes, such as CAMB and Gadget2,
LensTools brings together a cosmic shear simulation pipeline which,
complemented with a variety of WL feature measurement tools and parameter
sampling routines, provides easy access to the numerics for theoretical studies
of WL as well as for experiment forecasts. Being implemented in python,
LensTools takes full advantage of a range of state--of--the art techniques
developed by the large and growing open--source software community
(scipy,pandas,astropy,scikit-learn,emcee). We made the LensTools code available
on the Python Package Index and published its documentation on
http://lenstools.readthedocs.io | astro-ph_CO |
Observational Hints of a Pre--Inflationary Scale?: We argue that the lack of power exhibited by cosmic microwave background
(CMB) anisotropies at large angular scales might be linked to the onset of
inflation. We highlight observational features and theoretical hints that
support this view, and present a preliminary estimate of the physical scale
that would underlie the phenomenon. | astro-ph_CO |
HeII emission in Lyman-alpha nebulae: AGN or cooling radiation?: We present a study of an extended Lyman-alpha (Lya) nebula located in a known
overdensity at z~2.38. The data include multiwavelength photometry covering the
rest-frame spectral range from 0.1 to 250um, and deep optical spectra of the
sources associated with the extended emission. Two galaxies are associated with
the Lya nebula. One of them is a dust enshrouded AGN, while the other is a
powerful starburst, forming stars at >~600 Msol/yr. We detect the HeII emission
line at 1640A in the spectrum of the obscured AGN, but detect no emission from
other highly ionized metals (CIV or NV) as is expected from an AGN. One
scenario that simultaneously reproduces the width of the detected emission
lines, the lack of CIV emission, and the geometry of the emitting gas, is that
the HeII and the Lya emission are the result of cooling gas that is being
accreted on the dark matter halo of the two galaxies, Ly1 and Ly2. Given the
complexity of the environment associated with our Lya nebula it is possible
that various mechanisms of excitation are at work simultaneously. | astro-ph_CO |
On the extended structure of the Phoenix dwarf galaxy: We present the star formation history (SFH) and its variations with
galactocentric distance for the Local Group dwarf galaxy of Phoenix.
Color-magnitude diagram was obtained from WFPC2@HST reaching the oldest main
sequence turnoffs. The IAC-star and IAC-pop codes and the MinnIAC suite have
been used to obtain the star formation rate as a function of time, metallicity,
and radius. We find that Phoenix has had ongoing but gradually decreasing star
formation over nearly a Hubble time. The highest level of star formation
occurred from the formation of the galaxy till 10.5 Gyr ago, when 50% of the
total star formation had already taken place. From that moment, star formation
continues at a significant level until 6 Gyr ago, and at a very low level till
the present time. The chemical enrichment law shows a trend of slowly
increasing metallicity as a function of time till 8--6 Gyr ago, when Z starts
to increase steeply to the current value.
Young stars are found in the inner region of the galaxy only, but
intermediate-age and old stars can be found at all galactocentric distances.
This study shows that star formation started at all galactocentric distances in
Phoenix at an early epoch. Our results are compatible with a scenario in which
the star formation region envelope slowly shrinks as time goes on, possibly as
a natural result of pressure support reduction as gas supply diminishes. As a
consequence, star formation stopped first in outer regions and the scale-length
of the stellar mass density distribution decreased with time. No traces of a
true, old halo are apparent in Phoenix either in its stellar age distribution
or in the stellar mass density distribution, at least out to 0.5 kpc (about 2.5
scale-lengths) from the center. | astro-ph_CO |
Lagrangian Formulation of the Eulerian-EFT: We study the counter terms in the Eulerian version of the EFT of Large Scale
Structure. We reformulate the equations to solve for the displacement of fluid
elements as a bookkeeping variable and study the structure of the counter terms
in this formulation. We show that in many cases the time dependence of the
amplitude of the counter terms is irrelevant, as solutions obtained for various
time dependences differ by terms that can be reabsorbed by higher order counter
terms. We show that including all effects due to the non-locality in time and
the time dependence of the counter terms there are six new parameters relevant
for the two loop power spectrum calculation. We give explicit expressions for
all these terms and study the contributions to them from large and small modes.
We show that the shape of all these terms is very similar. | astro-ph_CO |
Inflationary Freedom and Cosmological Neutrino Constraints: The most stringent bounds on the absolute neutrino mass scale come from
cosmological data. These bounds are made possible because massive relic
neutrinos affect the expansion history of the universe and lead to a
suppression of matter clustering on scales smaller than the associated free
streaming length. However, the resulting effect on cosmological perturbations
is relative to the primordial power spectrum of density perturbations from
inflation, so freedom in the primordial power spectrum affects neutrino mass
constraints. Using measurements of the cosmic microwave background, the galaxy
power spectrum and the Hubble constant, we constrain neutrino mass and number
of species for a model independent primordial power spectrum. Describing the
primordial power spectrum by a 20-node spline, we find that the neutrino mass
upper limit is a factor three weaker than when a power law form is imposed, if
only CMB data are used. The primordial power spectrum itself is constrained to
better than 10 % in the wave vector range $k \approx 0.01 - 0.25$ Mpc$^{-1}$.
Galaxy clustering data and a determination of the Hubble constant play a key
role in reining in the effects of inflationary freedom on neutrino constraints.
The inclusion of both eliminates the inflationary freedom degradation of the
neutrino mass bound, giving for the sum of neutrino masses $\Sigma m_\nu <
0.18$ eV (at 95 % confidence level, Planck+BOSS+$H_0$), approximately
independent of the assumed primordial power spectrum model. When allowing for a
free effective number of species, $N_{eff}$, the joint constraints on $\Sigma
m_\nu$ and $N_{eff}$ are loosened by a factor 1.7 when the power law form of
the primordial power spectrum is abandoned in favor of the spline
parametrization. | astro-ph_CO |
Halo velocity profiles in screened modified gravity theories: Screened modified gravity predicts potentially large signatures in the
peculiar velocity field that makes it an interesting probe to test gravity on
cosmological scales. We investigate the signatures induced by the Symmetron and
a Chameleon $f(R)$ model in the peculiar velocity field using $N$-body
simulations. By studying fifth force and halo velocity profiles we identify
three general categories of effects found in screened modified gravity models:
a fully screened regime where we recover $\Lambda$CDM to high precision, an
unscreened regime where the fifth force is in full operation, and, a partially
screened regime where screening occurs in the inner part of a halo, but the
fifth force is active at larger radii. These three regimes can be pointed out
very clearly by analyzing the deviation in the maximum cluster velocity.
Observationally, the partially screened regime is of particular interest since
an uniform increase of the gravitational force - as present in the unscreened
regime - is degenerate with the (dynamical) halo mass estimate, and, thus, hard
to detect. | astro-ph_CO |
Euclid: Forecasts for $k$-cut $3 \times 2$ Point Statistics: Modelling uncertainties at small scales, i.e. high $k$ in the power spectrum
$P(k)$, due to baryonic feedback, nonlinear structure growth and the fact that
galaxies are biased tracers poses a significant obstacle to fully leverage the
constraining power of the {\it Euclid} wide-field survey. $k$-cut cosmic shear
has recently been proposed as a method to optimally remove sensitivity to these
scales while preserving usable information. In this paper we generalise the
$k$-cut cosmic shear formalism to $3 \times 2$ point statistics and estimate
the loss of information for different $k$-cuts in a $3 \times 2$ point analysis
of the {\it Euclid} data. Extending the Fisher matrix analysis
of~\citet{blanchard2019euclid}, we assess the degradation in constraining power
for different $k$-cuts. We work in the idealised case and assume the galaxy
bias is linear, the covariance is Gaussian, while neglecting uncertainties due
to photo-z errors and baryonic feedback. We find that taking a $k$-cut at $2.6
\ h \ {\rm Mpc} ^{-1}$ yields a dark energy Figure of Merit (FOM) of 1018. This
is comparable to taking a weak lensing cut at $\ell = 5000$ and a galaxy
clustering and galaxy-galaxy lensing cut at $\ell = 3000$ in a traditional $3
\times 2$ point analysis. We also find that the fraction of the observed
galaxies used in the photometric clustering part of the analysis is one of the
main drivers of the FOM. Removing $50 \% \ (90 \%)$ of the clustering galaxies
decreases the FOM by $19 \% \ (62 \%)$. Given that the FOM depends so heavily
on the fraction of galaxies used in the clustering analysis, extensive efforts
should be made to handle the real-world systematics present when extending the
analysis beyond the luminous red galaxy (LRG) sample. | astro-ph_CO |
Kinematical models of latetime cosmology and the statefinder diagnostic: The present work deals with kinematical models of latetime cosmology. It is
based on purely phenomenological assumption about the deceleration parameter.
The models are confronted to observational data sets of type Ia supernovae
distance modulus measurements and measurements of Hubble parameter at different
redshift. Constraints on the cosmological parameters are obtained by Markov
Chanin Monte Charlo (MCMC) analysis using the observation data sets. The values
of present Hubble parameter, deceleration parameter and the redshift of
transition from decelerated to accelerated phase of expansion are estimated for
the present kinematical models. Further the properties of dark energy for the
present models are explored with general relativistic assumptions. The dark
energy diagnostics, namely the Om diagnostic and the statefinder are adopted
for a comparison of the present models. A phase space constructed of two
different statefinder parameters breaks the degeneracy of the models. It is
observed that the kinematical models attain the corresponding {\Lambda}CDM
value on the phase space in the course of evolution. The evolution of matter
density contrast at linear level has also been studied for the present
kinematical models. | astro-ph_CO |
The luminosity distance-redshift relation up to second order in the
Poisson gauge with anisotropic stress: We present the generalization of previously published results, about the
perturbed redshift and the luminosity-redshift relation up to second order in
perturbation theory, for the case of the Poisson gauge and in the presence of
anisotropic stress. The results are therefore valid for general dark energy
models and (most) modified gravity models. We use an innovative approach based
on the recently proposed "geodesic light-cone" gauge. We then compare our
finding with other results, which recently appeared in the literature, for the
particular case of vanishing anisotropic stress. Arriving at a common accepted
expression for the non-linear and relativistic corrections to the redshift and
distance-redshift relation is of fundamental importance in view of future
cosmological surveys. Thanks to these surveys the Universe will be further
probed with high precision and at very different scales, where non-linear and
relativistic effects can play a key role. | astro-ph_CO |
Suzaku X-Ray Observations of the Accreting NGC 4839 Group of Galaxies
and the Radio Relic in the Coma Cluster: Based on Suzaku X-ray observations, we study the hot gas around the NGC4839
group of galaxies and the radio relic in the outskirts of the Coma cluster. We
find a gradual decline in the gas temperature from 5 keV around NGC4839 to 3.6
keV at the radio relic, across which there is a further, steeper drop down to
1.5 keV. This drop as well as the observed surface brightness profile are
consistent with a shock with Mach number M = 2.2 pm 0.5 and velocity vs = (1410
pm 110) km s^-1. A lower limit of B > 0.33 mu G is derived on the magnetic
field strength around the relic from upper limits to inverse Compton X-ray
emission. Although this suggests that the non-thermal electrons responsible for
the relic are generated by diffusive shock acceleration (DSA), the relation
between the measured Mach number and the electron spectrum inferred from radio
observations are inconsistent with that expected from the simplest,
test-particle theory of DSA. Nevertheless, DSA is still viable if it is
initiated by the injection of a pre-existing population of non-thermal
electrons. Combined with previous measurements, the temperature profile of Coma
in the southwest direction is shallower outside NGC4839 and also slightly
shallower in the outermost region. The metal abundance around NGC4839 is
confirmed to be higher than in its vicinity, implying a significant peak in the
abundance profile that decreases to 0.2 solar toward the outskirts. We
interpret these facts as due to ram pressure stripping of metal-enriched gas
from NGC4839 as it falls into Coma. The relic shock may result from the
combined interaction of pre-existing intracluster gas, gas associated with NGC
4839, and cooler gas flowing in from the large-scale structure filament in the
southwest. | astro-ph_CO |
The Local Group as a time machine: studying the high-redshift Universe
with nearby galaxies: We infer the UV luminosities of Local Group galaxies at early cosmic times
($z \sim 2$ and $z \sim 7$) by combining stellar population synthesis modeling
with star formation histories derived from deep color-magnitude diagrams
constructed from Hubble Space Telescope (HST) observations. Our analysis
provides a basis for understanding high-$z$ galaxies - including those that may
be unobservable even with the James Webb Space Telescope (JWST) - in the
context of familiar, well-studied objects in the very low-$z$ Universe. We find
that, at the epoch of reionization, all Local Group dwarfs were less luminous
than the faintest galaxies detectable in deep HST observations of blank fields.
We predict that JWST will observe $z \sim 7$ progenitors of galaxies similar to
the Large Magellanic Cloud today; however, the HST Frontier Fields initiative
may already be observing such galaxies, highlighting the power of gravitational
lensing. Consensus reionization models require an extrapolation of the observed
blank-field luminosity function at $z \approx 7$ by at least two orders of
magnitude in order to maintain reionization. This scenario requires the
progenitors of the Fornax and Sagittarius dwarf spheroidal galaxies to be
contributors to the ionizing background at $z \sim 7$. Combined with numerical
simulations, our results argue for a break in the UV luminosity function from a
faint-end slope of $\alpha \sim -2$ at $M_{\rm UV} < -13$ to $\alpha \sim -1.2$
at lower luminosities. Applied to photometric samples at lower redshifts, our
analysis suggests that HST observations in lensing fields at $z \sim 2$ are
capable of probing galaxies with luminosities comparable to the expected
progenitor of Fornax. | astro-ph_CO |
The detectability of dark matter annihilation with Fermi using the
anisotropy energy spectrum of the gamma-ray background: The energy-dependence of the anisotropy (the anisotropy energy spectrum) of
the large-scale diffuse gamma-ray background can reveal the presence of
multiple source populations. Annihilating dark matter in the substructure of
the Milky Way halo could give rise to a modulation in the anisotropy energy
spectrum of the diffuse gamma-ray emission measured by Fermi, enabling the
detection of a dark matter signal. We determine the detectability of a
dark-matter-induced modulation for scenarios in which unresolved blazars are
the primary contributor to the measured emission above ~1 GeV and find that in
some scenarios pair-annihilation cross sections of order the value expected for
thermal relic dark matter can produce a detectable feature. We anticipate that
the sensitivity of this technique to specific dark matter models could be
improved by tailored likelihood analysis methods. | astro-ph_CO |
Robust model comparison disfavors power law cosmology: Late-time power law expansion has been proposed as an alternative to the
standard cosmological model and shown to be consistent with some low-redshift
data. We test power law expansion against the standard flat $\Lambda$CDM
cosmology using goodness-of-fit and model comparison criteria. We consider Type
Ia supernova (SN Ia) data from two current compilations (JLA and Union2.1)
along with a current set of baryon acoustic oscillation (BAO) measurements that
includes the high-redshift Lyman-$\alpha$ forest measurements from BOSS
quasars. We find that neither power law expansion nor $\Lambda$CDM is strongly
preferred over the other when the SN Ia and BAO data are analyzed separately
but that power law expansion is strongly disfavored by the combination. We
treat the $R_\text{h} = ct$ cosmology (a constant rate of expansion) separately
and find that it is conclusively disfavored by all combinations of data that
include SN Ia observations and a poor overall fit when systematic errors in the
SN Ia measurements are ignored, despite a recent claim to the contrary. We
discuss this claim and some concerns regarding hidden model dependence in the
SN Ia data. | astro-ph_CO |
A blinding solution for inference from astronomical data: This paper presents a joint blinding and deblinding strategy for inference of
physical laws from astronomical data. The strategy allows for up to three
blinding stages, where the data may be blinded, the computations of theoretical
physics may be blinded, and --assuming Gaussianly distributed data-- the
covariance matrix may be blinded. We found covariance blinding to be
particularly effective, as it enables the blinder to determine close to exactly
where the blinded posterior will peak. Accordingly, we present an algorithm
which induces posterior shifts in predetermined directions by hiding
untraceable biases in a covariance matrix. The associated deblinding takes the
form of a numerically lightweight post-processing step, where the blinded
posterior is multiplied with deblinding weights. We illustrate the blinding
strategy for cosmic shear from KiDS-450, and show that even though there is no
direct evidence of the KiDS-450 covariance matrix being biased, the famous
cosmic shear tension with Planck could easily be induced by a
mischaracterization of correlations between $\xi_-$ at the highest redshift and
all lower redshifts. The blinding algorithm illustrates the increasing
importance of accurate uncertainty assessment in astronomical inferences, as
otherwise involuntary blinding through biases occurs. | astro-ph_CO |
Searching for Cosmic Strings in CMB Anisotropy Maps using Wavelets and
Curvelets: We use wavelet and curvelet transforms to extract signals of cosmic strings
from cosmic microwave background (CMB) temperature anisotropy maps, and to
study the limits on the cosmic string tension which various ongoing CMB
temperature anisotropy experiments will be able to achieve. We construct sky
maps with size and angular resolution corresponding to various experiments.
These maps contain the signals of a scaling solution of long string segments
with a given string tension $G \mu$, the contribution of the dominant Gaussian
primordial cosmological fluctuations, and pixel by pixel white noise with an
amplitude corresponding to the instrumental noise of the various experiments.
In the case that we include white noise, we find that the curvelets are more
powerful than wavelets. For maps with Planck specification, we obtain bounds on
the string tension comparable to what was obtained by the Planck collaboration.
Experiments with better angular resolution such as the South Pole Telescope
third generation (SPT-3G) survey will be able to yield stronger limits. For
maps with a specification of SPT-3G we find that string signals will be visible
down to a string tension of $G \mu = 1.4 \times 10^{-7}$. | astro-ph_CO |
Paradigms and Scenarios for the Dark Matter Phenomenon: Well known scaling laws among the structural properties of the dark and the
luminous matter in disc systems are too complex to be arisen by two inert
components that just share the same gravitational field. This brings us to
critically focus on the 30-year-old paradigm, that, resting on a priori
knowledge of the nature of Dark Matter (DM), has led us to a restricted number
of scenarios, especially favouring the collisionless $\Lambda$ Cold Dark Matter
one. Motivated by such observational evidence, we propose to resolve the dark
matter mystery by following a new Paradigm: the nature of DM must be
guessed/derived by deeply analyzing the properties of the dark and luminous
mass distribution at galactic scales. The immediate application of this
paradigm leads us to propose the existence of a direct interaction between Dark
and Standard Model particles, which has finely shaped the inner regions of
galaxies. | astro-ph_CO |
The Atlas3D project - X. On the origin of the molecular and ionised gas
in early-type galaxies: We make use of interferometric CO and HI observations, and optical
integral-field spectroscopy to probe the origin of the molecular and ionised
interstellar medium (ISM) in local early-type galaxies (ETGs). We find that
36\pm5% of our sample of fast rotating ETGs have their ionised gas
kinematically misaligned with respect to the stars, setting a strong lower
limit on the importance of externally acquired gas (e.g. from mergers and cold
accretion). Slow rotators have a flat distribution of misalignments, indicating
that the dominant source of gas is external. The molecular, ionised and atomic
gas in all the detected galaxies are always kinematically aligned, even when
they are misaligned from the stars, suggesting that all these three phases of
the ISM share a common origin. In addition, we find that the origin of the cold
and warm gas in fast-rotating ETGs is strongly affected by environment, despite
the molecular gas detection rate and mass fractions being fairly independent of
group/cluster membership. Galaxies in dense groups and the Virgo cluster nearly
always have their molecular gas kinematically aligned with the stellar
kinematics, consistent with a purely internal origin. In the field, however,
kinematic misalignments between the stellar and gaseous components indicate
that >46% of local fast-rotating ETGs have their gas supplied from external
sources. We discuss several scenarios which could explain the environmental
dichotomy, but find it difficult to simultaneously explain the kinematic
misalignment difference and the constant detection rate. Furthermore, our
results suggest that galaxy mass may be an important independent factor
associated with the origin of the gas, with the most massive fast-rotating
galaxies in our sample (M_K<-24 mag; stellar mass of >8x10^10 Msun) always
having kinematically aligned gas. (abridged) | astro-ph_CO |
The 21cm Signature of a Cosmic String Loop: Cosmic string loops lead to nonlinear baryon overdensities at early times,
even before the time which in the standard LCDM model corresponds to the time
of reionization. These overdense structures lead to signals in 21cm redshift
surveys at large redshifts. In this paper, we calculate the amplitude and shape
of the string loop-induced 21cm brightness temperature. We find that a string
loop leads to a roughly elliptical region in redshift space with extra 21cm
emission. The excess brightness temperature for strings with a tension close to
the current upper bound can be as high as 1 degree K for string loops generated
at early cosmological times (times comparable to the time of equal matter and
radiation) and observed at a redshift of z + 1 = 30. The angular extent of
these predicted "bright spots" is of the order 0.1 degree for a value of the
string tension equal to the current upper bound. These signals should be
detectable in upcoming high redshift 21cm surveys. | astro-ph_CO |
Description of CRESST-III Data: In CRESST-III, 10 cryogenic detector modules optimized for low energy
thresholds were operated for almost two years (May 2016 - February 2018).
Together with this document we are publishing data from the best performing
detector module which has a nuclear recoil threshold of 30.1eV. With this
data-set we were able to set limits on the cross-section for spin-dependent and
spin-independent elastic scattering of dark matter particles off nuclei at dark
matter masses down to 160MeV/c$^2$. We publish the energies of all events after
data selection as well as of all events within the acceptance region for
dark-matter searches. In this document we describe how to use these data sets. | astro-ph_CO |
K2: A new method for the detection of galaxy clusters based on CFHTLS
multicolor images: We have developed a new method, K2, optimized for the detection of galaxy
clusters in multicolor images. Based on the Red Sequence approach, K2 detects
clusters using simultaneous enhancements in both colors and position. The
detection significance is robustly determined through extensive Monte-Carlo
simulations and through comparison with available cluster catalogs based on two
different optical methods, and also on X-ray data. K2 also provides
quantitative estimates of the candidate clusters' richness and photometric
redshifts. Initially K2 was applied to 161 sq deg of two color gri images of
the CFHTLS-Wide data. Our simulations show that the false detection rate, at
our selected threshold, is only ~1%, and that the cluster catalogs are ~80%
complete up to a redshift of 0.6 for Fornax-like and richer clusters and to z
~0.3 for poorer clusters. Based on Terapix T05 release gri photometric
catalogs, 35 clusters/sq deg are detected, with 1-2 Fornax-like or richer
clusters every two square degrees. Catalogs containing data for 6144 galaxy
clusters have been prepared, of which 239 are rich clusters. These clusters,
especially the latter, are being searched for gravitational lenses -- one of
our chief motivations for cluster detection in CFHTLS. The K2 method can be
easily extended to use additional color information and thus improve overall
cluster detection to higher redshifts. The complete set of K2 cluster catalogs,
along with the supplementary catalogs for the member galaxies, are available on
request from the authors. | astro-ph_CO |
Line intensity mapping: a "novel" window to the cosmic web: Intensity mapping has been attracting increasing interest as a way to study
galaxy evolution and the large scale structure of the Universe. Instead of
detecting individual galaxies, we measure the integrated emission from a volume
of the universe. Contrary to galaxy surveys, it includes light from the
faintest objects in the cosmic web. We will start this overview by introducing
line intensity mapping and review its current observational status. We will
enumerate the most prominent emission lines for intensity mapping and discuss
how to model their observed signal. The prospects of using this technique in
the near future are very good with a wide range of experiments in different
parts of the electromagnetic spectrum. As for any other observational tool,
intensity mapping is not free of systematic uncertainties, some of which are
intrinsic to it. We will briefly discuss them as well as the means to deal with
foreground and background contamination. Here, we will focus on the science
cases for intensity mapping in the post-reionization universe. These range from
the history of star formation to measuring the acoustic scale and the
fundamental physics. | astro-ph_CO |
Galaxy Distributions as Fractal Systems: This paper discusses if large scale galaxy distribution samples containing
almost one million objects can be characterized as fractal systems. The
analysis performed by Teles et al. (2021; arXiv:2012.07164) on the UltraVISTA
DR1 survey is extended here to the SPLASH and COSMOS2015 catalogs, hence adding
750k new galaxies with measured redshifts to the studied samples. The standard
$\Lambda$CDM cosmology having $H_0=(70\pm5)$ km/s/Mpc and number density tools
required for describing these galaxy distributions as single fractal systems
with dimension $D$ are adopted. We use the luminosity distance $d_L$, redshift
distance $d_z$ and galaxy area distance (transverse comoving distance) $d_G$ as
relativistic distance definitions to derive galaxy number densities in the
redshift interval $0.1\le z\le4$ at volume limited subsamples defined by
absolute magnitudes in the K-band. Similar to the findings of Teles et al.
(2021; arXiv:2012.07164), the results show two consecutive redshift scales
where galaxy distribution data behave as single fractal structures. For $z<1$
we found $D=1.00\pm0.12$ for the SPLASH galaxies, and $D=1,39\pm0.19$ for the
COSMOS2015. For $1\le z\le4$ we respectively found $D=0.83^{+0.36}_{-0.37}$ and
$D=0.54^{+0.27}_{-0.26}$. These results were verified to be robust under the
assumed Hubble constant uncertainty. Calculations considering blue and red
galaxies subsamples in both surveys showed that the fractal dimensions of blue
galaxies as basically unchanged, but the ones for the red galaxies changed
mostly to smaller values, meaning that $D$ may be seen as a more intrinsic
property of the distribution of objects in the Universe, therefore allowing for
the fractal dimension to be used as a tool to study different populations of
galaxies. All results confirm the decades old theoretical prediction of a
decrease in the fractal dimension for $z>1$. | astro-ph_CO |
Renegade Subhaloes in the Local Group: Using a dark matter only Constrained Local UniversE Simulation (CLUES) we
examine the existence of subhaloes that change their affiliation from one of
the two prominent hosts in the Local Group (i.e. the Milky Way and the
Andromeda galaxy) to the other, and call these objects "renegade subhaloes". In
light of recent claims that the two Magellanic Clouds (MCs) may have originated
from another region (or even the outskirts) of the Local Group or that they
have been spawned by a major merger in the past of the Andromeda galaxy, we
investigate the nature of such events. However, we cannot confirm that renegade
subhaloes enter as deep into the potential well of their present host nor that
they share the most simplest properties with the MCs, namely mass and relative
velocity. Our simulation rather suggests that these renegade subhaloes appear
to be flying past one host before being pulled into the other. A merger is not
required to trigger such an event, it is rather the distinct environment of our
simulated Local Group facilitating such behavior. Since just a small fraction
of the full z=0 subhalo population are renegades, our study indicates that it
will be intrinsically difficult to distinguish them despite clear differences
in their velocity, radial distribution, shape and spin parameter distributions. | astro-ph_CO |
Mid-Infrared Properties of the Swift Burst Alert Telescope Active
Galactic Nuclei Sample of the Local Universe. I. Emission-Line Diagnostics: We compare mid-infrared emission-line properties, from high-resolution
Spitzer spectra of a hard X-ray (14 -- 195 keV) selected sample of nearby (z <
0.05) AGN detected by the Burst Alert Telescope (BAT) aboard Swift. The
luminosity distribution for the mid-infrared emission-lines, [O IV] 25.89
micron, [Ne II] 12.81 micron, [Ne III] 15.56 micron and [Ne V] 14.32/24.32
micron, and hard X-ray continuum show no differences between Seyfert 1 and
Seyfert 2 populations, however six newly discovered BAT AGNs are under-luminous
in [O IV], most likely the result of dust extinction in the host galaxy. The
overall tightness of the mid-infrared correlations and BAT fluxes and
luminosities suggests that the emission lines primarily arise in gas ionized by
the AGN. We also compare the mid-infrared emission-lines in the BAT AGNs with
those from published studies of ULIRGs, PG QSOs, star-forming galaxies and
LINERs. We find that the BAT AGN sample fall into a distinctive region when
comparing the [Ne III]/[Ne II] and the [O IV]/[Ne III] ratios. These line
ratios are lower in sources that have been previously classified in the
mid-infrared/optical as AGN than those found for the BAT AGN, suggesting that,
in our X-ray selected sample, the AGN represents the main contribution to the
observed line emission. These ratios represent a new emission line diagnostic
for distinguishing between AGN and star forming galaxies. | astro-ph_CO |
Doppler boosted dust emission and CIB-galaxy cross-correlations: a new
probe of cosmology and astrophysics: We identify a new cosmological signal, the Doppler-boosted Cosmic Infrared
Background (DB-CIB), arising from the peculiar motion of the galaxies whose
thermal dust emission source the cosmic infrared background (CIB). This new
observable is an independent probe of the cosmic velocity field, highly
analogous to the well-known kinematic Sunyaev-Zel'dovich (kSZ) effect.
Interestingly, DB-CIB does not suffer from the 'kSZ optical depth degeneracy',
making it immune from the complex astrophysics of galaxy formation. We forecast
that the DB-CIB effect is detectable in the cross-correlation of CCAT-Prime and
DESI-like experiments. We show that it also acts as a new CMB foreground which
can bias future kSZ cross-correlations, if not properly accounted for. | astro-ph_CO |
The Clustering Evolution of Primordial Black Holes: Primordial black holes might comprise a significant fraction of the dark
matter in the Universe and be responsible for the gravitational wave signals
from black hole mergers observed by the LIGO/Virgo collaboration. The spatial
clustering of primordial black holes might affect their merger rates and have a
significant impact on the constraints on their masses and abundances. We
provide some analytical treatment of the primordial black hole spatial
clustering evolution, compare our results with some of the existing N-body
numerical simulations and discuss the implications for the black hole merger
rates. If primordial black holes contribute to a small fraction of the dark
matter, primordial black hole clustering is not relevant. On the other hand,
for a large contribution to the dark matter, we argue that the clustering may
increase the late time Universe merger rate to a level compatible with the
LIGO/Virgo detection rate. As for the early Universe merger rate of black hole
binaries formed at primordial epochs, clustering alleviates the LIGO/Virgo
constraints, but does not evade them. | astro-ph_CO |
A Nonminimal Coupling Model and its Short-Range Solar System Impact: The objective of this work is to present the effects of a nonminimally
coupled model of gravity on a Solar System short range regime. For this reason,
this study is only valid when the cosmological contribution is considered
irrelevant. The action functional of the model involves two functions $f^1(R)$
and $f^2(R)$ of the Ricci scalar curvature $R$, where the last one multiplies
the matter Lagrangian.
Using a Taylor expansion around $R=0$ for both functions $f^1(R)$ and
$f^2(R)$, it was found that the metric around a spherical object is a
perturbation of the weak-field Schwarzschild metric. The $tt$ component of the
metric, a Newtonian plus a Yukawa perturbation term, is constrained using the
available observational results.
First it is shown that this effect is null when the characteristic mass
scales of each function $f^1(R)$ and $f^2(R)$ are identical. Besides, the
conclusion is that the nonminimal coupling only affects the Yukawa contribution
strength and not its range and that the Starobinsky model for inflation is not
experimentally constrained. Moreover, the geodetic precession effect, obtained
also from the radial perturbation of the metric, reveals to be of no relevance
for the constraints. | astro-ph_CO |
Cosmological constraints from the tomographic cross-correlation of DESI
Luminous Red Galaxies and Planck CMB lensing: We use luminous red galaxies selected from the imaging surveys that are being
used for targeting by the Dark Energy Spectroscopic Instrument (DESI) in
combination with CMB lensing maps from the Planck collaboration to probe the
amplitude of large-scale structure over $0.4\le z\le 1$. Our galaxy sample,
with an angular number density of approximately $500\,\mathrm{deg}^{-2}$ over
18,000 sq.deg., is divided into 4 tomographic bins by photometric redshift and
the redshift distributions are calibrated using spectroscopy from DESI. We fit
the galaxy autospectra and galaxy-convergence cross-spectra using models based
on cosmological perturbation theory, restricting to large scales that are
expected to be well described by such models. Within the context of
$\Lambda$CDM, combining all 4 samples and using priors on the background
cosmology from supernova and baryon acoustic oscillation measurements, we find
$S_8=\sigma_8(\Omega_m/0.3)^{0.5}=0.73\pm 0.03$. This result is lower than the
prediction of the $\Lambda$CDM model conditioned on the Planck data. Our data
prefer a slower growth of structure at low redshift than the model predictions,
though at only modest significance. | astro-ph_CO |
Dark energy with rigid voids versus relativistic voids alone: The standard model of cosmology is dominated - at the present epoch - by dark
energy. Its voids are rigid and Newtonian within a relativistic background. The
model prevents them from becoming hyperbolic. Observations of rapid velocity
flows out of voids are normally interpreted within the standard model that is
rigid in comoving coordinates, instead of allowing the voids' density parameter
to drop below critical and their curvature to become negative. Isn't it time to
advance beyond nineteenth century physics and relegate dark energy back to the
"no significant evidence" box? | astro-ph_CO |
Breaking the self-averaging properties of spatial galaxy fluctuations in
the Sloan Digital Sky Survey - Data Release Six: Statistical analyses of finite sample distributions usually assume that
fluctuations are self-averaging, i.e. that they are statistically similar in
different regions of the given sample volume. By using the scale-length method,
we test whether this assumption is satisfied in several samples of the Sloan
Digital Sky Survey Data Release Six. We find that the probability density
function (PDF) of conditional fluctuations, filtered on large enough spatial
scales (i.e., r>30 Mpc/h), shows relevant systematic variations in different
sub-volumes of the survey. Instead for scales r<30 Mpc/h the PDF is
statistically stable, and its first moment presents scaling behavior with a
negative exponent around one. Thus while up to 30 Mpc/h galaxy structures have
well-defined power-law correlations, on larger scales it is not possible to
consider whole sample average quantities as meaningful and useful statistical
descriptors. This situation is due to the fact that galaxy structures
correspond to density fluctuations which are too large in amplitude and too
extended in space to be self-averaging on such large scales inside the sample
volumes: galaxy distribution is inhomogeneous up to the largest scales, i.e. r
~ 100 Mpc/h, probed by the SDSS samples. We show that cosmological corrections,
as K-corrections and standard evolutionary corrections, do not qualitatively
change the relevant behaviors. Finally we show that the large amplitude galaxy
fluctuations observed in the SDSS samples are at odds with the predictions of
the standard LCDM model of structure formation.(Abridged version). | astro-ph_CO |
MASSIV: Mass Assembly Survey with SINFONI in VVDS. IV. Fundamental
relations of star-forming galaxies at 1<z< 1.6: How mass assembly occurs in galaxies and which process(es) contribute to this
activity are among the most highly debated questions in galaxy formation
theories. This has motivated our survey MASSIV of 0.9<z<1.9 star-forming
galaxies selected from the purely flux-limited VVDS redshift survey. For the
first time, we derive the relations between galaxy size, mass, and internal
velocity, and the baryonic Tully-Fisher relation, from a statistically
representative sample of star-forming galaxies. We find a dynamical mass that
agrees with those of rotating galaxies containing a gas fraction of ~20%,
perfectly consistent with the content derived using the Kennicutt-Schmidt
formulation and the expected evolution. Non-rotating galaxies have more compact
sizes for their stellar component, and are less massive than rotators, but do
not have statistically different sizes for their gas-component. We measure a
marginal evolution in the size-stellar mass and size-velocity relations in
which discs become evenly smaller with cosmic time at fixed stellar mass or
velocity, and are less massive at a given velocity than in the local Universe.
The scatter in the Tully-Fisher relation is smaller when we introduce the S05
index, which we interpret as evidence of an increase in the contribution to
galactic kinematics of turbulent motions with cosmic time. We report a
persistently large scatter for rotators in our relations, that we suggest is
intrinsic, and possibly caused by complex physical mechanism(s) at work in our
stellar mass/luminosity regime and redshift range. Our results consistently
point towards a mild, net evolution of these relations, comparable to those
predicted by cosmological simulations of disc formation for at least 8Gyr and a
dark halo strongly coupled with galactic spectrophotometric properties. | astro-ph_CO |
Galaxy Zoo 2: detailed morphological classifications for 304,122
galaxies from the Sloan Digital Sky Survey: We present the data release for Galaxy Zoo 2 (GZ2), a citizen science project
with more than 16 million morphological classifications of 304,122 galaxies
drawn from the Sloan Digital Sky Survey. Morphology is a powerful probe for
quantifying a galaxy's dynamical history; however, automatic classifications of
morphology (either by computer analysis of images or by using other physical
parameters as proxies) still have drawbacks when compared to visual inspection.
The large number of images available in current surveys makes visual inspection
of each galaxy impractical for individual astronomers. GZ2 uses classifications
from volunteer citizen scientists to measure morphologies for all galaxies in
the DR7 Legacy survey with m_r>17, in addition to deeper images from SDSS
Stripe 82. While the original Galaxy Zoo project identified galaxies as
early-types, late-types, or mergers, GZ2 measures finer morphological features.
These include bars, bulges, and the shapes of edge-on disks, as well as
quantifying the relative strengths of galactic bulges and spiral arms. This
paper presents the full public data release for the project, including measures
of accuracy and bias. The majority (>90%) of GZ2 classifications agree with
those made by professional astronomers, especially for morphological T-types,
strong bars, and arm curvature. Both the raw and reduced data products can be
obtained in electronic format at http://data.galaxyzoo.org . | astro-ph_CO |
Combining cluster observables and stacked weak lensing to probe dark
energy: Self-calibration of systematic uncertainties: We develop a new method of combining cluster observables (number counts and
cluster-cluster correlation functions) and stacked weak lensing signals of
background galaxy shapes, both of which are available in a wide-field optical
imaging survey. Assuming that the clusters have secure redshift estimates, we
show that the joint experiment enables a self-calibration of important
systematic errors including the source redshift uncertainty and the cluster
mass-observable relation, by adopting a single population of background source
galaxies for the lensing analysis. It allows us to use the relative strengths
of stacked lensing signals at different cluster redshifts for calibrating the
source redshift uncertainty, which in turn leads to accurate measurements of
the mean cluster mass in each bin. In addition, our formulation of stacked
lensing signals in Fourier space simplifies the Fisher matrix calculations, as
well as the marginalization over the cluster off-centering effect, the most
significant uncertainty in stacked lensing. We show that upcoming wide-field
surveys yield stringent constraints on cosmological parameters including dark
energy parameters, without any priors on nuisance parameters that model
systematic uncertainties. Specifically, the stacked lensing information
improves the dark energy FoM by a factor of 4, compared to that from the
cluster observables alone. The primordial non-Gaussianity parameter can also be
constrained with a level of f_NL~10. In this method, the mean source redshift
is well calibrated to an accuracy of 0.1 in redshift, and the mean cluster mass
in each bin to 5-10% accuracies, which demonstrates the success of the
self-calibration of systematic uncertainties from the joint experiment.
(Abridged) | astro-ph_CO |
Observational Constraints on Warm Inflation in Loop Quantum Cosmology: By incorporating quantum aspects of gravity, Loop Quantum Cosmology (LQC)
provides a self-consistent extension of the inflationary scenario, allowing for
modifications in the primordial inflationary power spectrum with respect to the
standard General Relativity one. We investigate such modifications and explore
the constraints imposed by the Cosmic Microwave Background (CMB) Planck
Collaboration data on the Warm Inflation (WI) scenario in the LQC context. We
obtain useful relations between the dissipative parameter of WI and the bounce
scale parameter of LQC. We also find that the number of required e-folds of
expansion from the bounce instant till the moment the observable scales crossed
the Hubble radius during inflation can be smaller in WI than in CI. In
particular, we find that this depends on how large is the dissipation in WI,
with the amount of required e-folds decreasing with the increasing of the
dissipation value. Furthermore, by performing a Monte Carlo Markov Chain
analysis for the considered WI models, we find good agreement of the model with
the data. This shows that the WI models studied here can explain the current
observations also in the context of LQC. | astro-ph_CO |
A limit on Planck-scale froth with ESPRESSO: Some models of quantum gravity predict that the very structure of spacetime
is `frothy' due to quantum fluctuations. Although the effect is expected to be
tiny, if these spacetime fluctuations grow over a large distance, the initial
state of a photon, such as its energy, is gradually washed out as the photon
propagates. Thus, in these models, even the most monochromatic light source
would gradually disperse in energy due to spacetime fluctuations over large
distances. In this paper, we use science verification observations obtained
with ESPRESSO at the Very Large Telescope to place a novel bound on the growth
of spacetime fluctuations. To achieve this, we directly measure the width of a
narrow Fe II absorption line produced by a quiescent gas cloud at redshift
z=2.34, corresponding to a comoving distance of ~5.8 Gpc. Using a heuristic
model where the energy fluctuations grow as sigma_E / E = (E/E_P)^alpha, where
E_P = 1.22 x 10^28 eV is the Planck energy, we rule out models with alpha <
0.634, including models where the quantum fluctuations grow as a random walk
process (alpha = 0.5). Finally, we present a new formalism where the
uncertainty accrued at discrete spacetime steps is drawn from a continuous
distribution. We conclude, if photons take discrete steps through spacetime and
accumulate Planck-scale uncertainties at each step, then our ESPRESSO
observations require that the step size must be at least >10^13.2 L_P, where
L_P is the Planck length. | astro-ph_CO |
Galaxies in LCDM with Halo Abundance Matching: luminosity-velocity
relation, baryonic mass-velocity relation, velocity function and clustering: It has long been regarded as difficult for a cosmological model to account
simultaneously for the galaxy luminosity, mass, and velocity distributions. We
revisit this issue using a modern compilation of observational data along with
the best available large-scale cosmological simulation of dark matter. We find
that the standard cosmological model, used in conjunction with halo abundance
matching (HAM) and simple dynamical corrections, fits all basic statistics of
galaxies with circular velocities Vcirc > 80 km/s. Our observational constraint
is the luminosity-velocity relation which allows all types of galaxies to be
included. We have compiled data for a variety of galaxies ranging from dwarf
irregulars to giant ellipticals. The data present a clear monotonic
luminosity-velocity relation from 50 km/s to 500 km/s, with a bend below 80
km/s and a systematic offset between late- and early-type galaxies. For
comparison to theory, we employ our LCDM "Bolshoi" simulation of dark matter,
which has unprecedented mass and force resolution. We use halo abundance
matching to assign rank-ordered galaxy luminosities to the dark matter halos.
The resulting predictions for the luminosity-velocity relation are in excellent
agreement with the available data on both early-type and late-type galaxies for
the luminosity range from Mr = -14-22. We also compare our predictions for the
"cold" baryon mass (i.e., stars and cold gas) of galaxies as a function of
circular velocity with the available observations, again finding a very good
agreement. The predicted circular velocity function is in agreement with the
galaxy velocity function for 80-400 km/s. However, we find that the dark matter
halos with Vcirc < 80 km/s are much more abundant than observed galaxies with
the same Vcirc . We find that the two-point correlation function of galaxies in
our model matches very well the results from the SDSS. | astro-ph_CO |
Galaxy Kinematics and Mass Calibration in Massive SZE Selected Galaxy
Clusters to z=1.3: The galaxy phase-space distribution in galaxy clusters provides insights into
the formation and evolution of cluster galaxies, and it can also be used to
measure cluster mass profiles. We present a dynamical study based on $\sim$3000
passive, non-emission line cluster galaxies drawn from 110 galaxy clusters. The
galaxy clusters were selected using the Sunyaev-Zel'dovich effect (SZE) in the
2500~deg$^2$ SPT-SZ survey and cover the redshift range $0.2 < z < 1.3$. We
model the clusters using the Jeans equation, while adopting NFW mass profiles
and a broad range of velocity dispersion anisotropy profiles. The data prefer
velocity dispersion anisotropy profiles that are approximately isotropic near
the center and increasingly radial toward the cluster virial radius, and this
is true for all redshifts and masses we study. The pseudo-phase-space density
profile of the passive galaxies is consistent with expectations for dark matter
particles and subhalos from cosmological $N$-body simulations. The dynamical
mass constraints are in good agreement with external mass estimates of the SPT
cluster sample from either weak lensing, velocity dispersions, or X-ray $Y_X$
measurements. However, the dynamical masses are lower (at the 2.2$\sigma$
level) when compared to the mass calibration favored when fitting the SPT
cluster data to a $\Lambda$CDM model with external cosmological priors,
including CMB anisotropy data from Planck. The discrepancy grows with redshift,
where in the highest redshift bin the ratio of dynamical to SPT+Planck masses
is $\eta=0.63^{+0.13}_{-0.08}\pm0.06$ (statistical and systematic),
corresponding to a $2.6\sigma$ discrepancy. | astro-ph_CO |
The squeezed matter bispectrum covariance with responses: We present a calculation of the angle-averaged squeezed matter bispectrum
covariance ${\rm Cov}\left(B_{m}(k_1, k_1', s_1), B_{m}(k_2, k_2',
s_2)\right)$, $s_i \ll k_i,k_i'$ ($i=1,2$), that uses matter power spectrum
responses to describe the coupling of large- to short-scale modes in the
nonlinear regime. The covariance is given by a certain configuration of the
6-point function, which we show is dominated by response-type mode-coupling
terms in the squeezed bispectrum limit. The terms that are not captured by
responses are small, effectively rendering our calculation complete and
predictive for linear $s_1,s_2$ values and any nonlinear values of
$k_1,k_1',k_2,k_2'$. Our numerical results show that the squeezed bispectrum
super-sample covariance is only a negligible contribution. We also compute the
power spectrum-bispectrum cross-covariance using responses. Our derivation for
the squeezed matter bispectrum is the starting point to calculate analytical
covariances for more realistic galaxy clustering and weak-lensing applications.
It can also be used in cross-checks of numerical ensemble estimates of the
general bispectrum covariance, given that it is effectively noise-free and
complete in the squeezed limit. | astro-ph_CO |
Neural network reconstructions for the Hubble parameter, growth rate and
distance modulus: This paper introduces a new approach to reconstruct cosmological functions
using artificial neural networks based on observational measurements with
minimal theoretical and statistical assumptions. By using neural networks, we
can generate computational models of observational datasets, and then we
compare them with the original ones to verify the consistency of our method.
This methodology is applicable to even small-size datasets. In particular, we
test the proposed method with data coming from cosmic chronometers, $f\sigma_8$
measurements, and the distance modulus of the Type Ia supernovae. Furthermore,
we introduce a first approach to generate synthetic covariance matrices through
a variational autoencoder, using the systematic covariance matrix of the Type
Ia supernova compilation. | astro-ph_CO |
Constraining Dark Matter-Baryon Scattering with Linear Cosmology: We derive constraints on elastic scattering between baryons and dark matter
using the cosmic microwave background (CMB) data from the Planck satellite and
the Lyman-alpha forest data from the Sloan Digital Sky Survey. Elastic
scattering allows baryons and dark matter to exchange momentum, affecting the
dynamics of linear density perturbations in the early Universe. We derive
constraints to scattering cross sections of the form sigma \propto v^n,
allowing for a wide range of velocity dependencies with n between -4 and 2. We
improve and correct previous estimates where they exist, including
velocity-independent cross section as well as dark matter millicharge and
electromagnetic dipole moments. Lyman-alpha forest data dominates the
constraints for n>-3, where the improvement over CMB data alone can be several
orders of magnitude. Dark matter-baryon scattering cannot affect the halo mass
function on mass scales M>10^{12} M_{solar}. Our results imply,
model-independently, that a baryon in the halo of a galaxy like our own Milky
Way, does not scatter from dark matter particles during the age of the galaxy. | astro-ph_CO |
3D spectroscopy of merger Seyfert galaxy Mrk 334: nuclear starburst,
superwind and the circumnuclear cavern: We are presenting new results on kinematics and structure of the Mrk 334
Seyfert galaxy. Panoramic (3D) spectroscopy is performed at the 6-m telescope
of the Special Astrophysical Observatory of the Russian Academy of Sciences
using the MPFS integral-field spectrograph and scanning Fabry--Perot
interferometer. The deep images have revealed that Mrk 334 is observed during
the final stage of its merging with a massive companion. A possible mass ratio
ranges from 1/5 to 1/3. The merger has triggered mass redistribution in the
disk resulting in an intensification of nuclear activity and in a burst of star
formation in the inner region of the galaxy. The circumnuclear starburst is so
intense that its contribution to the gas ionization exceeds that contribution
of the AGN. We interpret the nuclear gas outflow with velocities of ~200 km/s
as a galactic superwind that accompanies the violent star formation. This
suggestion is consistent with the asymmetric X-ray brightness distribution in
Mrk 334. The trajectory of the fragments of the disrupted satellite in the
vicinity of the main galaxy nucleus can be traced. In the galaxy disk a cavern
is found that is filled with a low-density ionized gas. We consider this region
to be the place where the remnants of the companion have recently penetrated
through the gaseous disk of the main galaxy. | astro-ph_CO |
Computing First-Passage Times with the Functional Renormalisation Group: We use Functional Renormalisation Group (FRG) techniques to analyse the
behaviour of a spectator field, $\sigma$, during inflation that obeys an
overdamped Langevin equation. We briefly review how a derivative expansion of
the FRG can be used to obtain Effective Equations of Motion (EEOM) for the one-
and two-point function and derive the EEOM for the three-point function. We
show how to compute quantities like the amplitude of the power spectrum and the
spectral tilt from the FRG. We do this explicitly for a potential with multiple
barriers and show that in general many different potentials will give identical
predictions for the spectral tilt suggesting that observations are agnostic to
localised features in the potential. Finally we use the EEOM to compute
first-passage time (FPT) quantities for the spectator field. The EEOM for the
one- and two-point function are enough to accurately predict the average time
taken $\left\langle \mathcal{N}\right\rangle$ to travel between two field
values with a barrier in between and the variation in that time $\delta
\mathcal{N}^2$. It can also accurately resolve the full PDF for time taken
$\rho (\mathcal{N})$, predicting the correct exponential tail. This suggests
that an extension of this analysis to the inflaton can correctly capture the
exponential tail that is expected in models producing Primordial Black Holes. | astro-ph_CO |
XMM-Newton RGS observation of the warm absorber in Mrk 279: The Seyfert 1 galaxy Mrk 279 was observed by XMM-Newton in November 2005 in
three consecutive orbits, showing significant short-scale variability (average
soft band variation in flux ~20%). The source is known to host a two-component
warm absorber with distinct ionisation states from a previous Chandra
observation. We aim to study the warm absorber in Mrk 279 and investigate any
possible response to the short-term variations of the ionising flux, and to
assess whether it has varied on a long-term time scale with respect to the
Chandra observation. We find no significant changes in the warm absorber on
neither short time scales (~2 days) nor at longer time scales (two and a half
years), as the variations in the ionic column densities of the most relevant
elements are below the 90% confidence level. The variations could still be
present but are statistically undetected given the signal-to-noise ratio of the
data. Starting from reasonable standard assumptions we estimate the location of
the absorbing gas, which is likely to be associated with the putative dusty
torus rather than with the Broad Line Region if the outflowing gas is moving at
the escape velocity or larger. | astro-ph_CO |
The Greater Impact of Mergers on the Growth of Massive Galaxies:
Implications for Mass Assembly and Evolution Since z~1: Using deep infrared observations conducted with the MOIRCS on the Subaru
Telescope in GOODS-N combined with public surveys in GOODS-S, we investigate
the dependence on stellar mass, M_*, and galaxy type of the close pair fraction
(5 kpc < r < 20 kpc) and implied merger rate. In common with some recent
studies we find that the fraction of paired systems that could result in major
mergers is low (~4%) and does not increase significantly with redshift to
z~1.2, with (1+z)^{1.6 \pm 1.6}. Our key finding is that massive galaxies with
M_* > 1E11 Msun are more likely to host merging companions than less massive
systems (M_* ~ 1E10 Msun). We find evidence for a higher pair fraction for red,
spheroidal hosts compared to blue, late-type systems, in line with expectations
based on clustering at small scales. So-called "dry" mergers between early-type
galaxies represent nearly 50% of close pairs with M_* > 3E10 Msun at z~0.5, but
less than 30% at z~1. This result can be explained by the increasing abundance
of red, early-type galaxies at these masses. We compare the volumetric merger
rate of galaxies with different masses to mass-dependent trends in galaxy
evolution, finding that major mergers cannot fully account for the formation of
spheroidal galaxies since z~1. In terms of mass assembly, major mergers
contribute little to galaxy growth below M_* ~ 3E10 Msun but are more
significant among galaxies with M_* > 1E11 Msun, 30% of which have undergone
mostly dry mergers over the observed redshift range. Overall, the relatively
more rapid coalescence of high mass galaxies mirrors the expected hierarchical
growth of halos and is consistent with recent model predictions, even if the
downsizing of star formation and morphological evolution involves additional
physical processes. | astro-ph_CO |
The Population of Viscosity- and Gravitational Wave-Driven Supermassive
Black Hole Binaries Among Luminous AGN: Supermassive black hole binaries (SMBHBs) in galactic nuclei are thought to
be a common by-product of major galaxy mergers. We use simple disk models for
the circumbinary gas and for the binary-disk interaction to follow the orbital
decay of SMBHBs with a range of total masses (M) and mass ratios (q), through
physically distinct regions of the disk, until gravitational waves (GWs) take
over their evolution. Prior to the GW-driven phase, the viscous decay is in the
stalled "secondary-dominated" regime. SMBHBs spend a non-negligible fraction of
10^7 years at orbital periods t_var between a day and a year. A dedicated
optical or X-ray survey could identify coalescing SMBHBs statistically, as a
population of periodically variable quasars, whose abundance N_var is
proportional to t_var^alpha, in a range of periods t_var around tens of weeks.
SMBHBs with M < 10^7 M_sun, with 0.5 < alpha < 1.5, would probe the physics of
viscous orbital decay, whereas the detection of a population of higher-mass
binaries, with alpha=8/3, would confirm that their decay is driven by GWs. The
lowest mass SMBHBs (M < 10^{5-6} M_sun) enter the GW-driven regime at short
orbital periods, in the frequency band of the Laser Interferometric Space
Antenna (LISA). While viscous processes are strongly sub-dominant in the last
few years of coalescence, they could reduce the amplitude of any unresolved
background of near-stationary LISA sources. We discuss constraints on the SMBHB
population available from existing data, and the sensitivity and sky coverage
requirements for a detection in future surveys. SMBHBs may also be identified
from velocity shifts in their spectra; we discuss the expected abundance of
SMBHBs as a function of their orbital velocity. | astro-ph_CO |
Evolution of magnetic fields in galaxies in the frame of hierarchical
structure formation cosmology: future tests with the SKA: Results from simulations of hierarchical structure formation cosmology
provide a tool to develop an evolutionary model of regular magnetic fields
coupled to galaxy formation and evolution. We use the dynamo theory to derive
the timescales of amplification and ordering of magnetic fields in disk and
puffy galaxies. Galaxies similar to the Milky Way formed their disks at
$z\approx10$ and regular fields of $\mu$G strength and a few kpc coherence
length were generated within 2 Gyr (at $z\approx3$), but field ordering up to
the coherence scale of the galaxy size took another 6 Gyr (at $z\approx0.5$).
Giant galaxies formed their disk already at $z\approx10$, allowing more
efficient dynamo generation of strong regular fields (with kpc coherence
length) already at $z\approx4$. Dwarf galaxies should have hosted fully
coherent fields at $z\approx1$. This evolutionary scenario and number of
predictions of the model can be tested by measurements of polarized synchrotron
emission and Faraday rotation with the planned Square Kilometre Array. This
model is used to simulate the evolution of regular fields in disk galaxies and
the polarized radio sky as part of the Square Kilometer Array Design Studies
(SKADS). | astro-ph_CO |
Stacking catalog sources in WMAP data: We stack WMAP 7-year temperature data around extragalactic point sources,
showing that the profiles are consistent with WMAP's beam models, in
disagreement with the findings of Sawangwit & Shanks (2010). These results
require that the source sample's selection is not biased by CMB fluctuations.
We compare profiles from sources in the standard WMAP catalog, the WMAP catalog
selected from a CMB-free combination of data, and the NVSS catalog, and
quantify the agreement with fits to simple parametric beam models. We estimate
the biases in source profiles due to alignments with positive CMB fluctuations,
finding them roughly consistent with those biases found with the WMAP standard
catalog. Addressing those biases, we find source spectral indices significantly
steeper than those used by WMAP, with strong evidence for spectral steepening
above 61 GHz. Such changes modify the power spectrum correction required for
unresolved point sources, and tend to weaken somewhat the evidence for
deviation from a Harrison-Zel'dovich primordial spectrum, but more analysis is
required. Finally, we discuss implications for current CMB experiments. | astro-ph_CO |
Models of Stephan's Quintet: Hydrodynamic Constraints on the Group's
Evolution: We present smoothed particle hydrodynamic models of the interactions in the
compact galaxy group, Stephan's Quintet. This work is extension of the earlier
collisionless N-body simulations of Renaud et al. in which the large-scale
stellar morphology of the group was modeled with a series of galaxy-galaxy
interactions in the simulations. Including thermohydrodynamic effects in this
work, we further investigate the dynamical interaction history and evolution of
the intergalactic gas of Stephan's Quintet. The major features of the group,
such as the extended tidal features and the group-wide shock, enabled us to
constrain the models reasonably well, while trying to reproduce multiple
features of the system. We found that reconstructing the two long tails
extending from NGC 7319 toward NGC 7320c one after the other in two separate
encounters is very difficult and unlikely, because the second encounter usually
destroys or distorts the already-generated tidal structure. Our models suggest
the two long tails may be formed simultaneously from a single encounter between
NGC 7319 and 7320c, resulting in a thinner and denser inner tail than the outer
one. The tails then also run parallel to each other as observed. The model
results support the ideas that the group-wide shock detected in
multi-wavelength observations between NGC 7319 and 7318b and the starburst
region north of NGC 7318b are triggered by the high-speed collision between NGC
7318b and the intergalactic gas. Our models show that a gas bridge is formed by
the high-speed collision and clouds in the bridge continue to interact for some
tens of millions of years after the impact. This produces many small shocks in
that region, resulting a much longer cooling time than that of a single impact
shock. | astro-ph_CO |
Efficient self-resonance instability from axions: It was recently shown that a coherent oscillation of an axion can cause an
efficient parametric resonance, leading to a prominent emission of the
gravitational waves (GWs). In this paper, conducting the Floquet analysis, we
investigate the parametric resonance instability, which potentially triggers
the emission of the GWs from axions. Such a resonance instability takes place,
when the time evolution of the background field significantly deviates from the
harmonic oscillation. Therefore, the resonance instability cannot be described
by the Mathieu equation, whose stability/instability chart is well known. In
this paper, introducing an explicitly calculable parameter $\tilde{q}$, which
can be used to classify different types of the parametric resonance described
by the general Hill's equation, we investigate the stability/instability chart
for the general Hill's equation. This can also apply to the case where the
background oscillation is anharmonic. We show that the flapping resonance
instability, which takes place for $\tilde{q}=O(1)$, typically leads to the
most significant growth of the inhomogeneous modes among the self-resonance
instability. We also investigate whether the flapping resonance takes place for
the cosine potential or not. | astro-ph_CO |
Molecular gas mass functions of normal star forming galaxies since z~3: We use deep far-infrared data from the PEP/GOODS-Herschel surveys and rest
frame ultraviolet photometry to study the evolution of the molecular gas mass
function of normal star forming galaxies. Computing the molecular gas mass,
M(mol), by scaling star formation rates (SFR) through depletion timescales, or
combining IR luminosity and obscuration properties as in Nordon et al., we
obtain M(mol) for roughly 700, z=0.2-3.0 galaxies near the star forming "main
sequence". The number density of galaxies follows a Schechter function of
M(mol). The characteristic mass M* is found to strongly evolve up to z~1, and
then to flatten at earlier epochs, resembling the infrared luminosity evolution
of similar objects. At z~1, our result is supported by an estimate based on the
stellar mass function of star forming galaxies and gas fraction scalings from
the PHIBSS survey. We compare our measurements to results from current models,
finding better agreement with those that are treating star formation laws
directly rather than in post-processing. Integrating the mass function, we
study the evolution of the M(mol) density and its density parameter Omega(mol). | astro-ph_CO |
The XMM-LSS catalogue: X-ray sources and associated multiwavelength
data. Version II: We present the final release of the multi-wavelength XMM-LSS data
set,covering the full survey area of 11.1 square degrees, with X-ray data
processed with the latest XMM-LSS pipeline version. The present publication
supersedes the Pierre et al.(2007) catalogue pertaining to the initial 5 square
degrees. We provide X-ray source lists in the customary energy bands (0.5-2 and
2-10 keV) for a total of 6721 objects in the deep full-exposure catalogue and
5572 in the 10ks-limited one, above a detection likelihood of 15 in at least
one band. We also provide a multiwavelength catalogue, cross-correlating our
list with IR, NIR, optical and UV catalogues. Customary data products (X-ray
FITS images, CFHTLS and SWIRE thumbnail images) are made available together
with our interactively queriable database in Milan, while a static snapshot of
the catalogues will be supplied to CDS, as soon as final acceptance is
completed. | astro-ph_CO |
Beyond Assembly Bias: Exploring Secondary Halo Biases for Cluster-size
Haloes: Secondary halo bias, commonly known as 'assembly bias,' is the dependence of
halo clustering on a halo property other than mass. This prediction of the
Lambda-Cold Dark Matter cosmology is essential to modelling the galaxy
distribution to high precision and interpreting clustering measurements. As the
name suggests, different manifestations of secondary halo bias have been
thought to originate from halo assembly histories. We show conclusively that
this is incorrect for cluster-size haloes. We present an up-to-date summary of
secondary halo biases of high-mass haloes due to various halo properties
including concentration, spin, several proxies of assembly history, and subhalo
properties. While concentration, spin, and the abundance and radial
distribution of subhaloes exhibit significant secondary biases, properties that
directly quantify halo assembly history do not. In fact, the entire assembly
histories of haloes in pairs are nearly identical to those of isolated haloes.
In general, a global correlation between two halo properties does not predict
whether or not these two properties exhibit similar secondary biases. For
example, assembly history and concentration (or subhalo abundance) are
correlated for both paired and isolated haloes, but follow slightly different
conditional distributions in these two cases. This results in a secondary halo
bias due to concentration (or subhalo abundance), despite the lack of assembly
bias in the strict sense for cluster-size haloes. Due to this complexity,
caution must be exercised in using any one halo property as a proxy to study
the secondary bias due to another property. | astro-ph_CO |
Photodissociation of H2 in Protogalaxies: Modeling Self-Shielding in 3D
Simulations: The ability of primordial gas to cool in proto-galactic haloes exposed to
Lyman-Werner (LW) radiation is critically dependent on the self-shielding of
H_2. We perform radiative transfer calculations of LW line photons,
post-processing outputs from three-dimensional adaptive mesh refinement (AMR)
simulations of haloes with T_vir > 10^4 K at redshifts around z=10. We
calculate the optically thick photodissociation rate numerically, including the
effects of density, temperature, and velocity gradients in the gas, as well as
line overlap and shielding of H_2 by HI, over a large number of sight-lines. In
low-density regions (n<10^4 cm^-3) the dissociation rates exceed those obtained
using most previous approximations by more than an order of magnitude; the
correction is smaller at higher densities. We trace the origin of the
deviations primarily to inaccuracies of (i) the most common fitting formula
(Draine & Bertoldi 1996) for the suppression of the dissociation rate and (ii)
estimates for the effective shielding column density from local properties of
the gas. The combined effects of gas temperature and velocity gradients are
comparatively less important, typically altering the spherically averaged rate
only by a factor of less than two. We present a simple modification to the DB96
fitting formula for the optically thick rate which improves agreement with our
numerical results to within approx. 15 per cent, and can be adopted in future
simulations. We find that estimates for the effective shielding column can be
improved by using the local Sobolev length. Our correction to the H_2
self-shielding reduces the critical LW flux to suppress H_2-cooling in
T_vir>10^4 K haloes by an order of magnitude; this increases the number of such
haloes in which supermassive (approx. M=10^5 M_sun) black holes may have
formed. | astro-ph_CO |
H0LiCOW XII. Lens mass model of WFI2033-4723 and blind measurement of
its time-delay distance and $H_0$: We present the lens mass model of the quadruply-imaged gravitationally lensed
quasar WFI2033-4723, and perform a blind cosmographical analysis based on this
system. Our analysis combines (1) time-delay measurements from 14 years of data
obtained by the COSmological MOnitoring of GRAvItational Lenses (COSMOGRAIL)
collaboration, (2) high-resolution $\textit{Hubble Space Telescope}$ imaging,
(3) a measurement of the velocity dispersion of the lens galaxy based on
ESO-MUSE data, and (4) multi-band, wide-field imaging and spectroscopy
characterizing the lens environment. We account for all known sources of
systematics, including the influence of nearby perturbers and complex
line-of-sight structure, as well as the parametrization of the light and mass
profiles of the lensing galaxy. After unblinding, we determine the effective
time-delay distance to be $4784_{-248}^{+399}~\mathrm{Mpc}$, an average
precision of $6.6\%$. This translates to a Hubble constant $H_{0} =
71.6_{-4.9}^{+3.8}~\mathrm{km~s^{-1}~Mpc^{-1}}$, assuming a flat $\Lambda$CDM
cosmology with a uniform prior on $\Omega_\mathrm{m}$ in the range [0.05, 0.5].
This work is part of the $H_0$ Lenses in COSMOGRAIL's Wellspring (H0LiCOW)
collaboration, and the full time-delay cosmography results from a total of six
strongly lensed systems are presented in a companion paper (H0LiCOW XIII). | astro-ph_CO |
Detecting Damped Lyman-$α$ Absorbers with Gaussian Processes: We develop an automated technique for detecting damped Lyman-$\alpha$
absorbers (DLAs) along spectroscopic lines of sight to quasi-stellar objects
(QSOs or quasars). The detection of DLAs in large-scale spectroscopic surveys
such as SDSS-III sheds light on galaxy formation at high redshift, showing the
nucleation of galaxies from diffuse gas. We use nearly 50 000 QSO spectra to
learn a novel tailored Gaussian process model for quasar emission spectra,
which we apply to the DLA detection problem via Bayesian model selection. We
propose models for identifying an arbitrary number of DLAs along a given line
of sight. We demonstrate our method's effectiveness using a large-scale
validation experiment, with excellent performance. We also provide a catalog of
our results applied to 162 858 spectra from SDSS-III data release 12. | astro-ph_CO |
The Atlas3D project -- I. A volume-limited sample of 260 nearby
early-type galaxies: science goals and selection criteria: The Atlas3D project is a multi-wavelength survey combined with a theoretical
modeling effort. The observations span from the radio to the millimeter and
optical, and provide multi-colour imaging, two-dimensional kinematics of the
atomic (HI), molecular (CO) and ionized gas (Hbeta, [OIII] and [NI]), together
with the kinematics and population of the stars (Hbeta, Fe5015 and Mgb), for a
carefully selected, volume-limited (1.16*10^5 Mpc^3) sample of 260 early-type
(elliptical E and lenticular S0) galaxies (ETGs). The models include
semi-analytic, N-body binary mergers and cosmological simulations of galaxy
formation. Here we present the science goals for the project and introduce the
galaxy sample and the selection criteria. The sample consists of nearby (D<42
Mpc) morphologically-selected ETGs extracted from a parent sample of 871
galaxies (8% E, 22% S0 and 70% spirals) brighter than M_K<-21.5 mag (stellar
mass M_Star>6*10^9 M_Sun). We analyze possible selection biases and we conclude
that the parent sample is essentially complete and statistically representative
of the nearby galaxy population. We present the size-luminosity relation for
the spirals and ETGs and show that the ETGs in the Atlas3D sample define a
tight red sequence in a colour-magnitude diagram, with few objects in the
transition from the blue cloud. We describe the strategy of the SAURON
integral-field observations and the extraction of the stellar kinematics with
the pPXF method. We give an overview of the characteristics of the other main
datasets already available for our sample and of the ongoing modelling
projects. | astro-ph_CO |
Beauty is Distractive: Particle production during multifield inflation: We consider a two-dimensional model of inflation, where the inflationary
trajectory is "deformed" by a grazing encounter with an Extra Species/Symmetry
Point (ESP) after the observable cosmological scales have left the Hubble
radius. The encounter entails a sudden production of particles, whose
backreaction causes a bending of the trajectory and a temporary decrease in
speed, both of which are sensitive to initial conditions. This "modulated"
effect leads to an additional contribution to the curvature perturbation, which
can be dominant if the encounter is close. We compute associated
non-Gaussianities, the bispectrum and its scale dependence as well as the
trispectrum, which are potentially detectable in many cases. In addition, we
consider a direct modulation of the coupling to the light field at the ESP via
a modulaton field, a mixed scenario whereby the modulaton is identified with a
second inflaton, and an extended Extra Species Locus (ESL); all of these
scenarios lead to similar additional contributions to observables. We conclude
that inflaton interactions throughout inflation are strongly constrained if
primordial non-Gaussianities remain unobserved in current experiments such as
PLANCK. If they are observed, an ESP encounter leaves additional signatures on
smaller scales which may be used to identify the model. | astro-ph_CO |
Detectability of 21cm-signal during the Epoch of Reionization with
21cm-Lyman-α emitter cross-correlation. II. Foreground contamination: Cross-correlation between the redshifted 21 cm signal and Lyman-{\alpha}
emitters (LAEs) is powerful tool to probe the Epoch of Reionization (EoR).
Although the cross-power spectrum (PS) has an advantage of not correlating with
foregrounds much brighter than the 21 cm signal, the galactic and
extra-galactic foregrounds prevent detection since they contribute to the
variance of the cross PS. Therefore, strategies for mitigating foregrounds are
required. In this work, we study the impact of foreground avoidance on the
measurement of the 21 cm-LAE cross-correlation. We then simulate the 21 cm
observation as observed by the Murchison Widefield Array (MWA). The point
source foreground is modelled from the GaLactic and Extragalactic All-sky
Murchison Widefield Array (GLEAM) survey catalogue, and the diffuse foreground
is evaluated using a parametric model. For LAE observations, we assume a large
survey of the Subaru Hyper Supreme-Cam (HSC), with spectroscopic observations
of the Prime Focus Spectrograph (PFS). To predict the 21 cm signal, we employ a
numerical simulation combining post processed radiative transfer and radiation
hydrodynamics. Using these models, the signal-to-noise ratio of 2D PS shows the
foreground contamination dominates the error of cross-PS even in the so-called
`EoR window'. We find that at least 99% of the point source foreground and 80%
of the galactic diffuse foreground must be removed to measure the EoR signal at
large scales $k<0.5 h \rm Mpc^{-1}$. Additionally, a sensitivity 80 times
larger than that of the MWA operating with 128 tiles and 99% of the point
source foreground removal are required for a detection at small scales. | astro-ph_CO |
The Kolmogorov-Smirnov test for the CMB: We investigate the statistics of the cosmic microwave background using the
Kolmogorov-Smirnov test. We show that, when we correctly de-correlate the data,
the partition function of the Kolmogorov stochasticity parameter is compatible
with the Kolmogorov distribution and, contrary to previous claims, the CMB data
are compatible with Gaussian fluctuations with the correlation function given
by standard Lambda-CDM. We then use the Kolmogorov-Smirnov test to derive upper
bounds on residual point source power in the CMB, and indicate the promise of
this statistics for further datasets, especially Planck, to search for
deviations from Gaussianity and for detecting point sources and Galactic
foregrounds. | astro-ph_CO |
Primordial blackholes and gravitational waves for an inflection-point
model of inflation: In this article we provide a new closed relationship between cosmic abundance
of primordial gravitational waves and primordial blackholes originated from
initial inflationary perturbations for inflection-point models of inflation
where inflation occurs below the Planck scale. The current Planck constraint on
tensor-to-scalar ratio, running of the spectral tilt, and from the abundance of
dark matter content in the universe, we can deduce a strict bound on the
current abundance of primordial blackholes to be within a range, $9.99712\times
10^{-3}<\Omega_{PBH}h^{2}<9.99736\times 10^{-3}$. | astro-ph_CO |
4MOST Consortium Survey 8: Cosmology Redshift Survey (CRS): The 4MOST Cosmology Redshift Survey (CRS) will perform stringent cosmological
tests via spectroscopic clustering measurements that will complement the best
lensing, cosmic microwave background and other surveys in the southern
hemisphere. The combination of carefully selected samples of bright galaxies,
luminous red galaxies, emission-line galaxies and quasars, totalling about 8
million objects over the redshift range $z = 0.15$ to $3.5$, will allow
definitive tests of gravitational physics. Many key science questions will be
addressed by combining CRS spectra of these targets with data from current or
future facilities such as the Large Synoptic Survey Telescope, the Square
Kilometre Array and the Euclid mission. | astro-ph_CO |
The NEWFIRM Medium-band Survey: Photometric Catalogs, Redshifts and the
Bimodal Color Distribution of Galaxies out to z~3: We present deep near-infrared (NIR) medium-bandwidth photometry over the
wavelength range 1-1.8 microns in the All-wavelength Extended Groth strip
International Survey (AEGIS) and Cosmic Evolution Survey (COSMOS) fields. The
observations were carried out as part of the NEWFIRM Medium-Band Survey (NMBS),
an NOAO survey program on the Mayall 4m telescope on Kitt Peak using the NOAO
Extremely Wide-Field Infrared Imager (NEWFIRM). In this paper, we describe the
full details of the observations, data reduction and photometry for the survey.
We also present a public K-selected photometric catalog, along with accurate
photometric redshifts. The redshifts are computed with 37 (20) filters in the
COSMOS (AEGIS) fields, combining the NIR medium-bandwidth data with existing
ultraviolet (UV; Galaxy Evolution Explorer), visible and NIR
(Canada-France-Hawaii Telescope and Subaru) and mid-IR (Spitzer/IRAC) imaging.
We find excellent agreement with publicly available spectroscopic redshifts,
with sigma_z/(1+z)~1-2% for ~4000 galaxies at z=0-3. The NMBS catalogs contain
~13,000 galaxies at z>1.5 with accurate photometric redshifts and rest-frame
colors. Due to the increased spectral resolution obtained with the five NIR
medium-band filters, the median 68% confidence intervals of the photometric
redshifts of both quiescent and star-forming galaxies are a factor of ~2 times
smaller when comparing catalogs with medium-band NIR photometry to NIR
broadband photometry. We show evidence for a clear bimodal color distribution
between quiescent and star-forming galaxies that persists to z~3, a higher
redshift than has been probed so far. | astro-ph_CO |
Ricci focusing, shearing, and the expansion rate in an almost
homogeneous Universe: The Universe is inhomogeneous, and yet it seems to be incredibly
well-characterised by a homogeneous relativistic model. One of the current
challenges is to accurately characterise the properties of such a model. In
this paper we explore how inhomogeneities may affect the overall optical
properties of the Universe by quantifying how they can bias the
redshift-distance relation in a number of toy models that mimic the real
Universe. The models that we explore are statistically homogeneous on large
scales. We find that the effect of inhomogeneities is of order of a few
percent, which can be quite important in precise estimation of cosmological
parameters. We discuss what lessons can be learned to help us tackle a more
realistic inhomogeneous universe. | astro-ph_CO |
The stellar-to-halo mass relation for Local Group galaxies: We contend that a single power law halo mass distribution is appropriate for
direct matching to the stellar masses of observed Local Group dwarf galaxies,
allowing the determination of the slope of the stellar mass-halo mass relation
for low mass galaxies. Errors in halo masses are well defined as the Poisson
noise of simulated local group realisations, which we determine using
constrained local universe simulations (CLUES). For the stellar mass range
10$^7$<M*<10$^8$M$_\odot$, for which we likely have a complete census of
observed galaxies, we find that the stellar mass-halo mass relation follows a
power law with slope of 3.1, significantly steeper than most values in the
literature. The steep relation between stellar and halo masses indicates that
Local Group dwarf galaxies are hosted by dark matter halos with a small range
of mass. Our methodology is robust down to the stellar mass to which the census
of observed Local Group galaxies is complete, but the significant uncertainty
in the currently measured slope of the stellar-to halo mass relation will
decrease dramatically if the Local Group completeness limit was
$10^{6.5}$M$\odot$ or below, highlighting the importance of pushing such limit
to lower masses and larger volumes. | astro-ph_CO |
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