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Revealing the Dark Matter Halo with Axion Direct Detection: The next generation of axion direct detection experiments may rule out or
confirm axions as the dominant source of dark matter. We develop a general
likelihood-based framework for studying the time-series data at such
experiments, with a focus on the role of dark-matter astrophysics, to search
for signatures of the QCD axion or axion like particles. We illustrate how in
the event of a detection the likelihood framework may be used to extract
measures of the local dark matter phase-space distribution, accounting for
effects such as annual modulation and gravitational focusing, which is the
perturbation to the dark matter phase-space distribution by the gravitational
field of the Sun. Moreover, we show how potential dark matter substructure,
such as cold dark matter streams or a thick dark disk, could impact the signal.
For example, we find that when the bulk dark matter halo is detected at
5$\sigma$ global significance, the unique time-dependent features imprinted by
the dark matter component of the Sagittarius stream, even if only a few percent
of the local dark matter density, may be detectable at $\sim$2$\sigma$
significance. A co-rotating dark disk, with lag speed $\sim$50 km$/$s, that is
$\sim$20$\%$ of the local DM density could dominate the signal, while colder
but as-of-yet unknown substructure may be even more important. Our likelihood
formalism, and the results derived with it, are generally applicable to any
time-series based approach to axion direct detection. | astro-ph_CO |
Type Ia Supernova Colors and Ejecta Velocities: Hierarchical Bayesian
Regression with Non-Gaussian Distributions: We investigate the statistical dependence of the peak intrinsic colors of
Type Ia supernovae (SN Ia) on their expansion velocities at maximum light,
measured from the Si II 6355 spectral feature. We construct a new hierarchical
Bayesian regression model, accounting for the random effects of intrinsic
scatter, measurement error, and reddening by host galaxy dust, and implement a
Gibbs sampler and deviance information criteria to estimate the correlation.
The method is applied to the apparent colors from BVRI light curves and Si II
velocity data for 79 nearby SNe Ia. The apparent color distributions of high
(HV) and normal velocity (NV) supernovae exhibit significant discrepancies for
B-V and B-R, but not other colors. Hence, they are likely due to intrinsic
color differences originating in the B-band, rather than dust reddening. The
mean intrinsic B-V and B-R color differences between HV and NV groups are 0.06
+/- 0.02 and 0.09 +/- 0.02 mag, respectively. A linear model finds significant
slopes of -0.021 +/- 0.006 and -0.030 +/- 0.009 mag/(1000 km/s) for intrinsic
B-V and B-R colors versus velocity, respectively. Since the ejecta velocity
distribution is skewed towards high velocities, these effects imply
non-Gaussian intrinsic color distributions with skewness up to +0.3. Accounting
for the intrinsic color-velocity correlation results in corrections to A_V
extinction estimates as large as -0.12 mag for HV SNe Ia and +0.06 mag for NV
events. Velocity measurements from SN Ia spectra have potential to diminish
systematic errors from the confounding of intrinsic colors and dust reddening
affecting supernova distances. | astro-ph_CO |
Detailed Calculation of Primordial Black Hole Formation During
First-Order Cosmological Phase Transitions: We recently presented a new mechanism for primordial black hole formation
during a first-order phase transition in the early Universe, which relies on
the build-up of particles which are predominantly reflected from the advancing
bubble wall. In this companion paper we provide details of the supporting
numerical calculations. After describing the general mechanism, we discuss the
criteria that need to be satisfied for a black hole to form. We then set out
the Boltzmann equation that describes the evolution of the relevant phase space
distribution function, carefully describing our treatment of the Liouville
operator and the collision term. Finally, we show that black holes will form
for a wide range of parameters. | astro-ph_CO |
The Data Release of the Sloan Digital Sky Survey-II Supernova Survey: This paper describes the data release of the Sloan Digital Sky Survey-II
(SDSS-II) Supernova Survey conducted between 2005 and 2007. Light curves,
spectra, classifications, and ancillary data are presented for 10,258 variable
and transient sources discovered through repeat ugriz imaging of SDSS Stripe
82, a 300 deg2 area along the celestial equator. This data release is comprised
of all transient sources brighter than r~22.5 mag with no history of
variability prior to 2004. Dedicated spectroscopic observations were performed
on a subset of 889 transients, as well as spectra for thousands of transient
host galaxies using the SDSS-III BOSS spectrographs. Photometric
classifications are provided for the candidates with good multi-color light
curves that were not observed spectroscopically. From these observations, 4607
transients are either spectroscopically confirmed, or likely to be, supernovae,
making this the largest sample of supernova candidates ever compiled. We
present a new method for SN host-galaxy identification and derive host-galaxy
properties including stellar masses, star-formation rates, and the average
stellar population ages from our SDSS multi-band photometry. We derive SALT2
distance moduli for a total of 1443 SN Ia with spectroscopic redshifts as well
as photometric redshifts for a further 677 purely-photometric SN Ia candidates.
Using the spectroscopically confirmed subset of the three-year SDSS-II SN Ia
sample and assuming a flat Lambda-CDM cosmology, we determine Omega_M = 0.315
+/- 0.093 (statistical error only) and detect a non-zero cosmological constant
at 5.7 sigmas. | astro-ph_CO |
Imprints of Oscillatory Bispectra on Galaxy Clustering: Long-short mode coupling during inflation, encoded in the squeezed bispectrum
of curvature perturbations, induces a dependence of the local, small-scale
power spectrum on long-wavelength perturbations, leading to a scale-dependent
halo bias. While this scale dependence is absent in the large-scale limit for
single-field inflation models that satisfy the consistency relation, certain
models such as resonant non-Gaussianity show a peculiar behavior on
intermediate scales. We reconsider the predictions for the halo bias in this
model by working in Conformal Fermi Coordinates, which isolate the physical
effects of long-wavelength perturbations on short-scale physics. We find that
the bias oscillates with scale with an envelope similar to that of equilateral
non-Gaussianity. Moreover, the bias shows a peculiar modulation with the halo
mass. Unfortunately, we find that upcoming surveys will be unable to detect the
signal because of its very small amplitude. We also discuss non-Gaussianity due
to interactions between the inflaton and massive fields: our results for the
bias agree with those in the literature. | astro-ph_CO |
Improved Modeling of the Kinematic Sunyaev-Zel'dovich Projected-Fields
signal and its Cosmological Dependence: Over the past decade, the kinematic Sunyaev-Zel'dovich (kSZ) effect has
emerged as an observational probe of the distribution of baryons and velocity
fields in the late Universe. Of the many ways to detect the kSZ, the
'projected-fields kSZ estimator' has the promising feature of not being limited
to galaxy samples with accurate redshifts. The current theoretical modeling of
this estimator involves an approximate treatment only applicable at small
scales. As the measurement fidelity rapidly improves, we find it necessary to
move beyond the original treatment and hence derive an improved theoretical
model for this estimator without these previous approximations. We show that
the differences between the predicted signal from the two models are
scale-dependent and will be significant for future measurements from the Simons
Observatory and CMB-S4 in combination with galaxy data from WISE or the Rubin
Observatory, which have high forecasted signal-to-noise ratios ($>100$). Thus,
adopting our improved model in future analyses will be important to avoid
biases. Equipped with our model, we explore the cosmological dependence of this
kSZ signal for future measurements. With a Planck prior, residual uncertainty
on $\Lambda$CDM parameters leads to $\sim7\%$ marginalized uncertainties on the
signal amplitude, compared to a sub-percent level forecasted with a fixed
cosmology. To illustrate the potential of this kSZ estimator as a cosmological
probe, we forecast initial constraints on $\Lambda$CDM parameters and the sum
of neutrino masses, paving the way for jointly fitting both baryonic
astrophysics and cosmology in future analyses. | astro-ph_CO |
Velocity-Density Correlations from the cosmicflows-3 Distance Catalog
and the 2MASS Redshift Survey: The peculiar velocity of a mass tracer is on average aligned with the dipole
modulation of the surrounding mass density field. We present a first
measurement of the correlation between radial peculiar velocities of objects in
the cosmicflows-3 catalog and the dipole moment of the 2MRS galaxy distribution
in concentric spherical shells centered on these objects. Limiting the analysis
to cosmicflows-3 objects with distances of $100 \rm Mpc h^{-1}$, the
correlation function is detected at a confidence level $> 4\sigma$. The
measurement is found consistent with the standard $\Lambda$CDM model at $<
1.7\sigma$ level. We formally derive the constraints
$0.32<\Omega^{0.55}\sigma_8<0.48$ ($68\% $ confidence level) or equivalently
$0.34<\Omega^{0.55}/b<0.52$, where $b$ is the galaxy bias factor. Deeper and
improved peculiar velocity catalogs will substantially reduce the
uncertainties, allowing tighter constraints from this type of correlations. | astro-ph_CO |
Alleviating the $H_0$ and $σ_8$ anomalies with a decaying dark
matter model: The Hubble tension between the $\Lambda$CDM-model-dependent prediction of the
current expansion rate $H_0$ using Planck data and direct, model-independent
measurements in the local universe from the SH0ES collaboration disagree at
$>3.5\sigma$. Moreover, there exists a milder $\sim 2\sigma$ tension between
similar predictions for the amplitude $S_8$ of matter fluctuations and its
measurement in the local universe. As explanations relying on unresolved
systematics have not been found, theorists have been exploring explanations for
these anomalies that modify the cosmological model, altering
early-universe-based predictions for these parameters. However, new
cosmological models that attempt to resolve one tension often worsen the other.
In this paper, we investigate a decaying dark matter (DDM) model as a solution
to both tensions simultaneously. Here, a fraction of dark matter density decays
into dark radiation. The decay rate $\Gamma$ is proportional to the Hubble rate
$H$ through the constant $\alpha_{\rm dr}$, the only additional parameter of
this model. Then, this model deviates most from $\Lambda$CDM in the early
universe, with $\alpha_{\rm dr}$ being positively correlated with $H_0$ and
negatively with $S_8$. Hence, increasing $\alpha_{\rm dr}$ (and allowing dark
matter to decay in this way) can then diminish both tensions simultaneously.
When only considering Planck CMB data and the local SH0ES prior on $H_0$, $\sim
1$\% dark matter decays, decreasing the $S_8$ tension to $0.3\sigma$ and
increasing the best-fit $H_0$ by $1.6$ km/s/Mpc. However, the addition of
intermediate-redshift data (the JLA supernova dataset and baryon acoustic
oscillation data) weakens the effectiveness of this model. Only $\sim 0.5$\% of
the dark matter decays bringing the $S_8$ tension back up to $\sim 1.5 \sigma$
and the increase in the best-fit $H_0$ down to $0.4$ km/s/Mpc. | astro-ph_CO |
The impact of the supersonic baryon-dark matter velocity difference on
the z~20 21cm background: Recently, Tseliakhovich and Hirata (2010) showed that during the cosmic Dark
Ages the baryons were typically moving supersonically with respect to the dark
matter with a spatially variable Mach number. Such supersonic motion may source
shocks that heat the Universe. This motion may also suppress star formation in
the first halos. Even a small amount of coupling of the 21cm signal to this
motion has the potential to vastly enhance the 21cm brightness temperature
fluctuations at 15<z<40 as well as to imprint acoustic oscillations in this
signal. We present estimates for the size of this coupling, which we calibrate
with a suite of cosmological simulations. Our simulations, discussed in detail
in a companion paper, are initialized to self-consistently account for gas
pressure and the dark matter-baryon relative velocity, v_bc (in contrast to
prior simulations). We find that the supersonic velocity difference
dramatically suppresses structure formation at 10-100 comoving kpc scales, it
sources shocks throughout the Universe, and it impacts the accretion of gas
onto the first star-forming minihalos (even for halo masses as large as ~10^7
Msun). However, we find that the v_bc-sourced temperature fluctuations can
contribute only as much as ~10% of the fluctuations in the 21cm signal. We do
find that v_bc could source an O(1) component in the power spectrum of the 21cm
signal via the X-ray (but not ultraviolet) backgrounds produced once the first
stars formed. In a scenario in which ~10^6 Msun minihalos reheated the Universe
via their X-ray backgrounds, we find that the pre-reionization 21cm signal
would be larger than previously anticipated and exhibit significant acoustic
features. We show that structure formation shocks are unable to heat the
Universe sufficiently to erase a strong 21cm absorption trough at z ~ 20 that
is found in most models of the sky-averaged 21cm intensity. | astro-ph_CO |
Estimating Black Hole Masses in Quasars Using Broad Optical and UV
Emission Lines: We review past work using broad emission lines as virial estimators of black
hole masses in quasars. Basically one requires estimates of the emitting region
radius and virial velocity dispersion to obtain black hole masses. The three
major ways to estimate the broad-line emitting region (BLR) radius involve: (1)
direct reverberation mapping, (2) derivation of BLR radius for larger samples
using the radius-luminosity correlation derived from reverberation measures,
and (3) estimates of BLR radius using the definition of the ionization
parameter solved for BLR radius (photoionization method). At low redshift (z <
0.7) FWHM H-beta serves as the most widely used estimator of virial velocity
dispersion. FWHM H-beta can provide estimates for tens of thousands of quasars
out to z ~ 3.8 (IR spectroscopy beyond z ~ 1). A new photoionization method
also shows promise for providing many reasonable estimates of BLR radius via
high S/N IR spectroscopy of the UV region 1300 -- 2000 A. FWHM MgII 2800 can
serve as a surrogate for FWHM H-beta in the range 0.4 < z < 6.5 while CIV 1549
is affected by broadening due to non-virial motions and best avoided (i.e.
there is no clear conversion factor between FWHM H-beta and FWHM CIV 1549).
Most quasars yield black hole mass estimates in the range 7 < log M< 9.7. There
is no strong evidence for values above 10.0 and there may be evidence for a
turnover in the maximum black hole mass near z ~ 5. | astro-ph_CO |
The F-GAMMA program: multi-wavelength AGN studies in the Fermi-GST era: The F -GAMMA program is a coordinated effort of several observing facilities
to understand the AGN/blazar phenomenon via a multi-frequency monitoring
approach, especially in the era of Fermi-GST. Some 60 prominent sources are
monitored monthly with the Effelsberg 100-m telescope, the IRAM 30-m telescope
and more frequently but in a less uniform fashion at the APEX 12-m telescope,
covering from 2.64 to 345 GHz. The program has been running since January 2007
and here some of its findings are summarized. (a) There are two major
variability patterns that the spectra of sources follow, one
spectral-evolution-dominated and one achromatic. (b) The FSRQs show higher
brightness temperatures indicative of larger Doppler factors at play and (c) a
statistically significant radio-gamma-ray correlation has been found with a
method recently suggested by Pavlidou et al. (in prep.). | astro-ph_CO |
On the relativistic mass function and averaging in cosmology: The general relativistic description of cosmological structure formation is
an important challenge from both the theoretical and the numerical point of
views. In this paper we present a brief prescription for a general relativistic
treatment of structure formation and a resulting mass function on galaxy
cluster scales in a highly generic scenario. To obtain this we use an exact
scalar averaging scheme together with the relativistic generalization of
Zel'dovich's approximation (RZA) that serves as a closure condition for the
averaged equations. | astro-ph_CO |
On the Effective Equation of State of Dark Energy: In an effective field theory model with an ultraviolet momentum cutoff, there
is a relation between the effective equation of state of dark energy and the
ultraviolet cutoff scale. It implies that a measure of the equation of state of
dark energy different from minus one, does not rule out vacuum energy as dark
energy. It also indicates an interesting possibility that precise measurements
of the infrared properties of dark energy can be used to probe the ultraviolet
cutoff scale of effective quantum field theory coupled to gravity. In a toy
model with a vacuum energy dominated universe with a Planck scale cutoff, the
dark energy effective equation of state is -0.96. | astro-ph_CO |
Measuring cosmic bulk flows with Type Ia Supernovae from the Nearby
Supernova Factory: Context. Our Local Group of galaxies appears to be moving relative to the
cosmic microwave background with the source of the peculiar motion still
uncertain. While in the past this has been studied mostly using galaxies as
distance indicators, the weight of type Ia supernovae (SNe Ia) has increased
recently with the continuously improving statistics of available low-redshift
supernovae.
Aims. We measured the bulk flow in the nearby universe ($0.015 < z < 0.1$)
using 117 SNe Ia observed by the Nearby Supernova Factory, as well as the
Union2 compilation of SN Ia data already in the literature.
Methods. The bulk flow velocity was determined from SN data binned in
redshift shells by including a coherent motion (dipole) in a cosmological fit.
Additionally, a method of spatially smoothing the Hubble residuals was used to
verify the results of the dipole fit. To constrain the location and mass of a
potential mass concentration (e.g., the Shapley supercluster) responsible for
the peculiar motion, we fit a Hubble law modified by adding an additional mass
concentration.
Results. The analysis shows a bulk flow that is consistent with the direction
of the CMB dipole up to $z \sim 0.06$, thereby doubling the volume over which
conventional distance measures are sensitive to a bulk flow. We see no
significant turnover behind the center of the Shapley supercluster. A simple
attractor model in the proximity of the Shapley supercluster is only marginally
consistent with our data, suggesting the need for another, more distant source.
In the redshift shell $0.06 < z < 0.1$, we constrain the bulk flow velocity to
$< 240~\textrm{km s}^{-1}$ (68% confidence level) for the direction of the CMB
dipole, in contradiction to recent claims of the existence of a large-amplitude
dark flow. | astro-ph_CO |
Population III.1 and III.2 gamma-Ray Bursts: Constraints on the event
rate for future radio and X-ray surveys: We calculate the theoretical event rate of gamma-ray bursts (GRBs) from the
collapse of massive first-generation (Population III; Pop III) stars. The Pop
III GRBs could be super-energetic with the isotropic energy up to $E_{\rm iso}
\gtrsim 10^{55-57}$ ergs, providing a unique probe of the high-redshift
Universe. We consider both the so-called Pop III.1 stars (primordial) and Pop
III.2 stars (primordial but affected by radiation from other stars). We employ
a semi-analytical approach that considers inhomogeneous hydrogen reionization
and chemical evolution of the intergalactic medium. We show that Pop III.2 GRBs
occur more than 100 times more frequently than Pop III.1 GRBs, and thus should
be suitable targets for future GRB missions. Interestingly, our optimistic
model predicts an event rate that is already constrained by the current radio
transient searches. We expect $\sim10-10^4$ radio afterglows above $\sim$ 0.3
mJy on the sky with $\sim 1$ year variability and mostly without GRBs
(orphans), which are detectable by ALMA, EVLA, LOFAR, and SKA, while we expect
to observe maximum of $N < 20$ GRBs per year integrated over at $z>6$ for Pop
III.2 and $N < 0.08$ per year integrated over at $z>10$ for Pop III.1 with
EXIST, and $N < 0.2$ for Pop III.2 GRBs per year integrated over at $z > 6$
with \textit{Swift}. | astro-ph_CO |
Measuring the lensing potential with tomographic galaxy number counts: We investigate how the lensing potential can be measured tomographically with
future galaxy surveys using their number counts. Such a measurement is an
independent test of the standard $\Lambda$CDM framework and can be used to
discern modified theories of gravity. We perform a Fisher matrix forecast based
on galaxy angular-redshift power spectra, assuming specifications consistent
with future photometric Euclid-like surveys and spectroscopic SKA-like surveys.
For the Euclid-like survey we derive a fitting formula for the magnification
bias. Our analysis suggests that the cross correlation between different
redshift bins is very sensitive to the lensing potential such that the survey
can measure the amplitude of the lensing potential at the same level of
precision as other standard $\Lambda$CDM cosmological parameters. | astro-ph_CO |
The Extragalactic Distance Database: A database can be accessed on the web at http://edd.ifa.hawaii.edu that was
developed to promote access to information related to galaxy distances. The
database has three functional components. First, tables from many literature
sources have been gathered and enhanced with links through a distinct galaxy
naming convention. Second, comparisons of results both at the levels of
parameters and of techniques have begun and are continuing, leading to
increasing homogeneity and consistency of distance measurements. Third, new
material are presented arising from ongoing observational programs at the
University of Hawaii 2.2m telescope, radio telescopes at Green Bank, Arecibo,
and Parkes and with Hubble Space Telescope. This new observational material is
made available in tandem with related material drawn from archives and passed
through common analysis pipelines. | astro-ph_CO |
Integral field spectroscopy with SINFONI of VVDS galaxies. I. Galaxy
dynamics and mass assembly at 1.2 < z < 1.6: Context. Identifying the main processes of galaxy assembly at high redshifts
is still a major issue to understand galaxy formation and evolution at early
epochs in the history of the Universe. Aims. This work aims to provide a first
insight into the dynamics and mass assembly of galaxies at redshifts 1.2<z<1.6,
the early epoch just before the sharp decrease of the cosmic star formation
rate. Methods. We use the near-infrared integral field spectrograph SINFONI on
the ESO-VLT under 0.65 seeing to obtain spatially resolved spectroscopy on nine
emission line galaxies with 1.2<z<1.6 from the VIMOS VLT Deep Survey. We derive
the velocity fields and velocity dispersions on kpc scales using the Halpha
emission line. Results. Out of the nine star-forming galaxies, we find that
galaxies distribute in three groups: two galaxies can be well reproduced by a
rotating disk, three systems can be classified as major mergers and four
galaxies show disturbed dynamics and high velocity dispersion. We argue that
there is evidence for hierarchical mass assembly from major merger, with most
massive galaxies with M>10^11Msun subject to at least one major merger over a 3
Gyr period as well as for continuous accretion feeding strong star formation.
Conclusions. These results point towards a galaxy formation and assembly
scenario which involves several processes, possibly acting in parallel, with
major mergers and continuous gas accretion playing a major role. Well
controlled samples representative of the bulk of the galaxy population at this
key cosmic time are necessary to make further progress. | astro-ph_CO |
Cosmological Limits on Hidden Sector Dark Matter: We explore the model-independent constraints from cosmology on a dark-matter
particle with no prominent standard model interactions that interacts and
thermalizes with other particles in a hidden sector. Without specifying
detailed hidden-sector particle physics, we characterize the relevant physics
by the annihilation cross section, mass, and temperature ratio of the hidden to
visible sectors. While encompassing the standard cold WIMP scenario, we do not
require the freeze-out process to be nonrelativistic. Rather, freeze-out may
also occur when dark matter particles are semirelativistic or relativistic. We
solve the Boltzmann equation to find the conditions that hidden-sector dark
matter accounts for the observed dark-matter density, satisfies the
Tremaine-Gunn bound on dark-matter phase space density, and has a
free-streaming length consistent with cosmological constraints on the matter
power spectrum. We show that for masses <1.5 keV no region of parameter space
satisfies all these constraints. This is a gravitationally-mediated lower bound
on the dark-matter mass for any model in which the primary component of dark
matter once had efficient interactions -- even if it has never been in
equilibrium with the standard model. | astro-ph_CO |
Abell 2744 may be a supercluster aligned along the sightline: To explain the unusual richness and compactness of the Abell 2744, we propose
a hypothesis that it may be a rich supercluster aligned along the sightline,
and present a supporting evidence obtained numerically from the MultiDark
Planck 2 simulations with a linear box size of $1\,h^{-1}$Gpc. Applying the
friends-of-friends (FoF) algorithm with a linkage length of $0.33$ to a sample
of the cluster-size halos from the simulations, we identify the superclusters
and investigate how many superclusters have filamentary branches that would
appear to be similar to the Abell 2744 if the filamentary axis is aligned with
the sightline. Generating randomly a unit vector as a sightline at the position
of the core member of each supercluster and projecting the positions of the
members onto the plane perpendicular to the direction of the sightline, we
measure two dimensional distances ($R_{2d}$) of the member halos from the core
for each supercluster. Defining a Abell 2744-like spuercluster as the one
having a filamentary branch composed of eight or more members with $R_{2d}\le
1\,$Mpc and masses comparable to those of the observed Abell 2744
substructures, we find one Abell 2744-like supercluster at $z=0.3$ and two at
$z=0$. Repeating the same analysis but with the data from the Big MultiDark
Planck simulations performed on a larger box of linear size of
$2.5\,h^{-1}$Mpc, we find that the number of the Abell 2744-like superclusters
at $z=0$ increases up to eighteen, among which three are found more massive
than $5\times 10^{15}\,M_{\odot}$. | astro-ph_CO |
The Herschel-SPIRE Legacy Survey (HSLS): the scientific goals of a
shallow and wide submillimeter imaging survey with SPIRE: A large sub-mm survey with Herschel will enable many exciting science
opportunities, especially in an era of wide-field optical and radio surveys and
high resolution cosmic microwave background experiments. The Herschel-SPIRE
Legacy Survey (HSLS), will lead to imaging data over 4000 sq. degrees at 250,
350, and 500 micron. Major Goals of HSLS are: (a) produce a catalog of 2.5 to 3
million galaxies down to 26, 27 and 33 mJy (50% completeness; 5 sigma confusion
noise) at 250, 350 and 500 micron, respectively, in the southern hemisphere
(3000 sq. degrees) and in an equatorial strip (1000 sq. degrees), areas which
have extensive multi-wavelength coverage and are easily accessible from ALMA.
Two thirds of the of the sources are expected to be at z > 1, one third at z >
2 and about a 1000 at z > 5. (b) Remove point source confusion in secondary
anisotropy studies with Planck and ground-based CMB data. (c) Find at least
1200 strongly lensed bright sub-mm sources leading to a 2% test of general
relativity. (d) Identify 200 proto-cluster regions at z of 2 and perform an
unbiased study of the environmental dependence of star formation. (e) Perform
an unbiased survey for star formation and dust at high Galactic latitude and
make a census of debris disks and dust around AGB stars and white dwarfs. | astro-ph_CO |
Constraints on non-resonant photon-axion conversion from the Planck
satellite data: The non-resonant conversion of Cosmic Microwave Background (CMB) photons into
scalar as well as light pseudoscalar particles such as axion-like particles
(ALPs) in the presence of turbulent magnetic fields can cause a unique,
spatially fluctuating spectral distortion in the CMB. We use the publicly
available Planck temperature maps for the frequency channels (70-545 GHz) to
obtain the first ALP distortion map using $45\%$ clean part of the sky. The
$95^{th}$ percentile upper limit on the RMS fluctuation of ALP distortions from
the cleanest part of the CMB sky at $15$ arcmin angular resolution is $18.5
\times 10^{-6}$. The RMS fluctuation in the distortion map is also consistent
with different combinations of frequency channels and sky-fractions. | astro-ph_CO |
Astrophysical Probes of Fundamental Physics: The dramatic confrontation between new observations and theories of the early
and recent universe makes cosmology one of the most rapidly advancing fields in
the physical sciences. The universe is a unique laboratory in which to probe
fundamental physics, the rationale being to start from fundamental physics
inspired models and explore their consequences in sufficient quantitative
detail to be able to identify key astrophysical and cosmological tests of the
underlying theory (or developing new tests when appropriate). An unprecedented
number of such tests will be possible in the coming years, by exploiting the
ever improving observational data. In this spirit I will highlight some open
issues in cosmology and particle physics and provide some motivation for this
symposium. | astro-ph_CO |
On the Lyth bound and single field slow-roll inflation: We take a pragmatic, model independent approach to single field slow-roll
inflation by imposing conditions to the slow-roll parameter $\epsilon$ and its
derivative $\epsilon^{\prime }.$ To accommodate the recent (large) values of
$r$ reported by the BICEP2 collaboration we advocate for a decreasing
$\epsilon$ during most part of inflation. However because at
$\phi_{\mathrm{H}}$, at which the perturbations are produced, some $50$ $-$
$60$ e-folds before the end of inflation, $\epsilon$ is increasing we thus
require that $\epsilon$ develops a maximum for $\phi > \phi_{\mathrm{H}}$ and
then decrease to small values where most e-folds are produced. The end of
inflation might occur trough a hybrid field and a small $\Delta\phi$ is
obtained with a sufficiently thin $\epsilon$ which, however, should not
conflict with the curvature of the potential measured by the second slow-roll
parameter $\eta$. The conclusion is that under these circumstances $\Delta\phi$
and the spectral index $n_{\mathrm{s}}$ are restricted to narrow windows of
values. | astro-ph_CO |
Structures of Local Galaxies Compared to High Redshift Star-forming
Galaxies: The rest-frame far-ultraviolet (FUV) morphologies of 8 nearby interacting and
starburst galaxies (Arp 269, M 82, Mrk 8, NGC 520, NGC 1068, NGC 3079, NGC
3310, NGC 7673) are compared with 54 galaxies at z ~ 1.5 and 46 galaxies at z ~
4 observed in the GOODS-ACS field. The nearby sample is artificially redshifted
to z ~ 1.5 and 4. We compare the simulated galaxy morphologies to real z ~ 1.5
and 4 UV-bright galaxy morphologies. We calculate the Gini coefficient (G), the
second-order moment of the brightest 20% of the galaxy's flux (M_20), and the
Sersic index (n). We explore the use of nonparametric methods with 2D profile
fitting and find the combination of M_20 with n an efficient method to classify
galaxies as having merger, exponential disk, or bulge-like morphologies. When
classified according to G and M_20, 20/30% of real/simulated galaxies at z ~
1.5 and 37/12% at z ~ 4 have bulge-like morphologies. The rest have merger-like
or intermediate distributions. Alternatively, when classified according to the
Sersic index, 70% of the z ~ 1.5 and z ~ 4 real galaxies are exponential disks
or bulge-like with n > 0.8, and ~30% of the real galaxies are classified as
mergers. The artificially redshifted galaxies have n values with ~35% bulge or
exponential at z ~ 1.5 and 4. Therefore, ~20-30% of Lyman-break galaxies (LBGs)
have structures similar to local starburst mergers, and may be driven by
similar processes. We assume merger-like or clumpy star-forming galaxies in the
GOODS field have morphological structure with values n < 0.8 and M_20 > -1.7.
We conclude that Mrk 8, NGC 3079, and NGC 7673 have structures similar to those
of merger-like and clumpy star-forming galaxies observed at z ~ 1.5 and 4. | astro-ph_CO |
The Power Spectra of Polarized, Dusty Filaments: We develop an analytic model for the power spectra of polarized filamentary
structures as a way to study the Galactic polarization foreground to the Cosmic
Microwave Background. Our approach is akin to the cosmological halo-model
framework, and reproduces the main features of the Planck 353 GHz power
spectra. We model the foreground as randomly-oriented, three-dimensional,
spheroidal filaments, accounting for their projection onto the sky. The main
tunable parameters are the distribution of filament sizes, the filament
physical aspect ratio, and the dispersion of the filament axis around the local
magnetic field direction. The abundance and properties of filaments as a
function of size determine the slopes of the foreground power spectra, as we
show via scaling arguments. The filament aspect ratio determines the ratio of
$B$-mode power to $E$-mode power, and specifically reproduces the
Planck-observed dust ratio of one-half when the short axis is roughly
one-fourth the length of the long axis. Filament misalignment to the local
magnetic field determines the $TE$ cross-correlation, and to reproduce Planck
measurements, we need a (three-dimensional) misalignment angle with a root mean
squared dispersion of about 50 degrees. These parameters are not sensitive to
the particular filament density profile. By artificially skewing the
distribution of the misalignment angle, this model can reproduce the
Planck-observed (and parity-violating) $TB$ correlation. The skewing of the
misalignment angle necessary to explain $TB$ will cause a yet-unobserved,
positive $EB$ dust correlation, a possible target for future experiments. | astro-ph_CO |
Structure formation with suppressed small-scale perturbations: All commonly considered dark matter scenarios are based on hypothetical
particles with small but non-zero thermal velocities and tiny interaction
cross-sections. A generic consequence of these attributes is the suppression of
small-scale matter perturbations either due to free-streaming or due to
interactions with the primordial plasma. The suppression scale can vary over
many orders of magnitude depending on particle candidate and production
mechanism in the early Universe. While nonlinear structure formation has been
explored in great detail well above the suppression scale, the range around
suppressed perturbations is still poorly understood. In this paper we study
structure formation in the regime of suppressed perturbations using both
analytical techniques and numerical simulations. We develop simple and
theoretically motivated recipes for the halo mass function, the expected number
of satellites, and the halo concentrations, which are designed to work for
power spectra with suppression at arbitrary scale and of arbitrary shape. As
case studies, we explore warm and mixed dark matter scenarios where effects are
most distinctive. Additionally, we examine the standard dark matter scenario
based on weakly interacting massive particles (WIMP) and compare it to pure
cold dark matter with zero primordial temperature. We find that our
analytically motivated recipes are in good agreement with simulations for all
investigated dark matter scenarios, and we therefore conclude that they can be
used for generic cases with arbitrarily suppressed small-scale perturbations. | astro-ph_CO |
Neutral hydrogen in galaxy clusters: impact of AGN feedback and
implications for intensity mapping: By means of zoom-in hydrodynamic simulations we quantify the amount of
neutral hydrogen (HI) hosted by groups and clusters of galaxies. Our
simulations, which are based on an improved formulation of smoothed particle
hydrodynamics (SPH), include radiative cooling, star formation, metal
enrichment and supernova feedback, and can be split in two different groups,
depending on whether feedback from active galactic nuclei (AGN) is turned on or
off. Simulations are analyzed to account for HI self-shielding and the presence
of molecular hydrogen. We find that the mass in neutral hydrogen of dark matter
halos monotonically increases with the halo mass and can be well described by a
power-law of the form $M_{\rm HI}(M,z)\propto M^{3/4}$. Our results point out
that AGN feedback reduces both the total halo mass and its HI mass, although it
is more efficient in removing HI. We conclude that AGN feedback reduces the
neutral hydrogen mass of a given halo by $\sim50\%$, with a weak dependence on
halo mass and redshift. The spatial distribution of neutral hydrogen within
halos is also affected by AGN feedback, whose effect is to decrease the
fraction of HI that resides in the halo inner regions. By extrapolating our
results to halos not resolved in our simulations we derive astrophysical
implications from the measurements of $\Omega_{\rm HI}(z)$: halos with circular
velocities larger than $\sim25~{\rm km/s}$ are needed to host HI in order to
reproduce observations. We find that only the model with AGN feedback is
capable of reproducing the value of $\Omega_{\rm HI}b_{\rm HI}$ derived from
available 21cm intensity mapping observations. | astro-ph_CO |
Updated constraint on a primordial magnetic field during big bang
nucleosynthesis and a formulation of field effects: A new upper limit on the amplitude of primordial magnetic field (PMF) is
derived by a comparison between a calculation of elemental abundances in big
bang nucleosynthesis (BBN) model and the latest observational constraints on
the abundances. Updated nuclear reaction rates are adopted in the calculation.
Effects of PMF on the abundances are consistently taken into account in the
numerical calculation with the precise formulation of changes in physical
variables. We find that abundances of 3He and 6Li increase while that of 7Li
decreases when the PMF amplitude increases, in the case of the baryon-to-photon
ratio determined from the measurement of cosmic microwave background radiation.
We derive a constraint on the present amplitude of PMF, i.e., B(0)<1.5 micro G
[corresponding to the amplitude less than 2.0x10^{11} G at BBN temperature of
T=10^9 K] based on the rigorous calculation. | astro-ph_CO |
Forecast and analysis of the cosmological redshift drift: The cosmological redshift drift could lead to the next step in high-precision
cosmic geometric observations, becoming a direct and irrefutable test for
cosmic acceleration. In order to test the viability and possible properties of
this effect, also called Sandage-Loeb (SL) test, we generate a model
independent mock data set so as to compare its constraining power with that of
the future mock data sets of Type Ia Supernovae (SNe) and Baryon Acoustic
Oscillations (BAO). The performance of those data sets is analyzed by testing
several cosmological models with the Markov chain Monte Carlo (MCMC) method,
both independently and combining all data sets. Final results show that, in
general, SL data sets allow for remarkable constraints on the matter density
parameter today $\Omega_m$ on every tested model, showing also a great
complementarity with SNe and BAO data regarding dark energy (DE) parameters. | astro-ph_CO |
On the Bispectra of Very Massive Tracers in the Effective Field Theory
of Large-Scale Structure: The Effective Field Theory of Large-Scale Structure (EFTofLSS) provides a
consistent perturbative framework for describing the statistical distribution
of cosmological large-scale structure. In a previous EFTofLSS calculation that
involved the one-loop power spectra and tree-level bispectra, it was shown that
the $k$-reach of the prediction for biased tracers is comparable for all
investigated masses if suitable higher-derivative biases, which are less
suppressed for more massive tracers, are added. However, it is possible that
the non-linear biases grow faster with tracer mass than the linear bias,
implying that loop contributions could be the leading correction to the
bispectra. To check this, we include the one-loop contributions in a fit to
numerical data in the limit of strongly enhanced higher-order biases. We show
that the resulting one-loop power spectra and higher-derivative plus leading
one-loop bispectra fit the two- and three-point functions respectively up to
$k\simeq 0.19\ h\ \rm{Mpc}^{-1}$ and $k\simeq 0.14\ h\ \rm{Mpc}^{-1}$ at the
percent level. We find that the higher-order bias coefficients are not strongly
enhanced, and we argue that the gain in perturbative reach due to the leading
one-loop contributions to the bispectra is relatively small. Thus, we conclude
that higher-derivative biases provide the leading correction to the bispectra
for tracers of a very wide range of masses. | astro-ph_CO |
The Structure of HE 1104-1805 from Infrared to X-Ray: The gravitationally lensed quasar HE 1104-1805 has been observed at a variety
of wavelengths ranging from the mid-infrared to X-ray for nearly 20 years. We
combine flux ratios from the literature, including recent Chandra data, with
new observations from the SMARTS telescope and HST, and use them to investigate
the spatial structure of the central regions using a Bayesian Monte Carlo
analysis of the microlensing variability. The wide wavelength coverage allows
us to constrain not only the accretion disk half-light radius r_1/2, but the
power-law slope \xi\ of the size-wavelength relation r_1/2 ~ \lambda^\xi. With
a logarithmic prior on the source size, the (observed-frame) R-band half-light
radius log(r_1/2/cm) is 16.0+0.3-0.4, and the slope \xi\ is 1.0+0.30-0.56. We
put upper limits on the source size in soft (0.4-1.2 keV) and hard (1.2-8 keV)
X-ray bands, finding 95% upper limits on log (r_1/2/cm) of 15.33 in both bands.
A linear prior yields somewhat larger sizes, particularly in the X-ray bands.
For comparison, the gravitational radius, using a black hole mass estimated
using the H\beta\ line, is log(r_g/cm) = 13.94. We find that the accretion disk
is probably close to face-on, with cos i = 1.0 being four times more likely
than cos i = 0.5. We also find probability distributions for the mean mass of
the stars in the foreground lensing galaxy, the direction of the transverse
peculiar velocity of the lens, and the position angle of the projected
accretion disk's major axis (if not face-on). | astro-ph_CO |
Magnetic Fields of Agns and Standard Accretion Disk Model: Testing by
Optical Polarimetry: We have developed the method that allows us to estimate the magnetic field
strength at the horizon of a supermassive black hole (SMBH) through the
observed polarization of optical emission of the accreting disk surrounding
SMBH. The known asymptotic formulae for the Stokes parameters of outgoing
radiation are azimuthal averaged, which corresponds to an observation of the
disk as a whole. We consider two models of the embedding 3D-magnetic field, the
regular field, and the regular field with an additional chaotic (turbulent)
component. It is shown that the second model is preferable for estimating the
magnetic field in NGC 4258. For estimations we used the standard accretion disk
model assuming that the same power-law dependence of the magnetic field follows
from the range of the optical emission down to the horizon. The observed
optical polarization from NGC 4258 allowed us to find the values 10^3 - 10^4
Gauss at the horizon, depending on the particular choice of the model
parameters. We also discuss the wavelength dependencies of the light
polarization, and possibly applying them for a more realistic choice of
accretion disk parameters. | astro-ph_CO |
Galaxy Bias and $σ_8$ from Counts in Cells from the SDSS Main
Sample: The counts-in-cells (CIC) galaxy probability distribution depends on both the
dark matter clustering amplitude $\sigma_8$ and the galaxy bias $b$. We present
a theory for the CIC distribution based on a previous prescription of the
underlying dark matter distribution and a linear volume transformation to
redshift space. We show that, unlike the power spectrum, the CIC distribution
breaks the degeneracy between $\sigma_8$ and $b$ on scales large enough that
both bias and redshift distortions are still linear; thus we obtain a
simultaneous fit for both parameters. We first validate the technique on the
Millennium Simulation and then apply it to the SDSS Main Galaxy Sample. We find
$\sigma_8 = 0.94^{+.11}_{-.10}$ and $b = 1.36^{+.14}_{-.11}$, consistent with
previous complementary results from redshift distortions and from Planck. | astro-ph_CO |
Discovery of Hydrogen Fluoride in the Cloverleaf Quasar at z = 2.56: We report the first detection of hydrogen fluoride (HF) toward a high
redshift quasar. Using the Caltech Submillimeter Observatory (CSO) we detect
the HF J = 1 - 0 transition in absorption toward the Cloverleaf, a broad
absorption line (BAL) quasi-stellar object (QSO) at z=2.56. The detection is
statistically significant at the ~ 6 sigma level. We estimate a lower limit of
4 \times 1014 cm-2 for the HF column density and using a previous estimate of
the hydrogen column density, we obtain a lower limit of 1.7 \times 10-9 for the
HF abundance. This value suggests that, assuming a Galactic N(HF)/NH ratio, HF
accounts for at least ~10% of the fluorine in the gas phase along the line of
sight to the Cloverleaf quasar. This observation corroborates the prediction
that HF should be a good probe of the molecular gas at high redshift.
Measurements of the HF abundance as a function of redshift are urgently needed
to better constrain the fluorine nucleosynthesis mechanism(s). | astro-ph_CO |
Testing MONDian Dark Matter with Galactic Rotation Curves: MONDian dark matter (MDM) is a new form of dark matter quantum that naturally
accounts for Milgrom's scaling, usually associated with modified Newtonian
dynamics (MOND), and theoretically behaves like cold dark matter (CDM) at
cluster and cosmic scales. In this paper, we provide the first observational
test of MDM by fitting rotation curves to a sample of 30 local spiral galaxies
(z approximately 0.003). For comparison, we also fit the galactic rotation
curves using MOND, and CDM. We find that all three models fit the data well.
The rotation curves predicted by MDM and MOND are virtually indistinguishable
over the range of observed radii (~1 to 30 kpc). The best-fit MDM and CDM
density profiles are compared. We also compare with MDM the dark matter density
profiles arising from MOND if Milgrom's formula is interpreted as Newtonian
gravity with an extra source term instead of as a modification of inertia. We
find that discrepancies between MDM and MOND will occur near the center of a
typical spiral galaxy. In these regions, instead of continuing to rise sharply,
the MDM mass density turns over and drops as we approach the center of the
galaxy. Our results show that MDM, which restricts the nature of the dark
matter quantum by accounting for Milgrom's scaling, accurately reproduces
observed rotation curves. | astro-ph_CO |
Angular Correlation Function from sample covariance with BOSS and eBOSS
LRG: The Baryon Acoustic Oscillations (BAO) are one of the most used probes to
understand the accelerated expansion of the Universe. Traditional methods rely
on fiducial model information within their statistical analysis, which may be a
problem when constraining different families of models. The aim of this work is
to provide a method that constrains $\theta_{BAO}$ through a model-independent
and compare parameter estimation of the angular correlation function polynomial
approach, using the covariance matrix from the galaxy sample from thin redshift
bins, with the usual mock sample covariance matrix. We proposed a different
approach to finding the BAO angular feature revisiting previous work in the
literature, we take the bias between the correlation function between the bins
and the whole sample. We used widths of $\delta z = 0.002$ separation for all
samples as the basis for a sample covariance matrix weighted by the statistical
importance of the redshift bin. We propose a different weighting scheme based
only on random pair counting. We also propose an alternate shift parameter
based only on the data. Each sample belongs to the Sloan Digital Sky Survey
Luminous Red Galaxies (LRG): BOSS1, BOSS2, and eBOSS, with effective redshift
$z_{eff}$: 0.35, 0.51, 0.71, respectively, and different numbers of bins with
50, 100, and 200 respectively. In addition, we correct the angular separation
from the polynomial fit ($\theta_{fit}$) that encodes the BAO feature with a
bias function obtained by comparing each bin correlation function with the
correlation function of the whole set. We also tested the same correction
choosing the bin at $z_{eff}$ and found that for eBOSS $\theta_{BAO}$ is in $1
\sigma$ agreement with the Planck 18 model. BOSS1 and BOSS2 $\theta_{BAO}$
agreed in $1\sigma$ with the Pantheon+ & S$H_0$ES Flat$\Lambda$CDM model, in
tension with Planck 18. | astro-ph_CO |
Effective Theory of Large-Scale Structure with Primordial
Non-Gaussianity: We develop the effective theory of large-scale structure for non-Gaussian
initial conditions. The effective stress tensor in the dark matter equations of
motion contains new operators, which originate from the squeezed limit of the
primordial bispectrum. Parameterizing the squeezed limit by a scaling and an
angular dependence, captures large classes of primordial non-Gaussianity.
Within this parameterization, we classify the possible contributions to the
effective theory. We show explicitly how all terms consistent with the
symmetries arise from coarse graining the dark matter equations of motion and
its initial conditions. We also demonstrate that the system is closed under
renormalization and that the basis of correction terms is therefore complete.
The relevant corrections to the matter power spectrum and bispectrum are
computed numerically and their relative importance is discussed. | astro-ph_CO |
Detecting relic gravitational waves in the CMB: Optimal parameters and
their constraints: The prospect of detecting relic gravitational waves (RGWs), through their
imprint in the cosmic microwave background radiation, provides an excellent
opportunity to study the very early Universe. In simplest viable theoretical
models the RGW background is characterized by two parameters, the
tensor-to-scalar ratio $r$ and the tensor spectral index $n_t$. In this paper,
we analyze the potential joint constraints on these two parameters, $r$ and
$n_t$, using the data from the upcoming cosmic microwave background radiation
experiments. Introducing the notion of the best pivot multipole $\ell_t^*$, we
find that at this pivot multipole the parameters $r$ and $n_t$ are
uncorrelated, and have the smallest variances. We derive the analytical
formulae for the best pivot multipole number $\ell_t^*$, and the variances of
the parameters $r$ and $n_t$. We verify these analytical calculations using
numerical simulation methods, and find agreement to within 20%. The analytical
results provides a simple way to estimate the detection ability for the relic
gravitational waves by the future observations of the cosmic microwave
background radiation. | astro-ph_CO |
The effect of early radiation in N-body simulations of cosmic structure
formation: Newtonian N-body simulations have been employed successfully over the past
decades for the simulation of the cosmological large-scale structure. Such
simulations usually ignore radiation perturbations (photons and massless
neutrinos) and the impact of general relativity (GR) beyond the background
expansion. This approximation can be relaxed and we discuss three different
approaches that are accurate to leading order in GR. For simulations that start
at redshift less than about 100 we find that the presence of early radiation
typically leads to percent-level effects on the numerical power spectra at
large scales. Our numerical results agree across the three methods, and we
conclude that all of the three methods are suitable for simulations in a
standard cosmology. Two of the methods modify the N-body evolution directly,
while the third method can be applied as a post-processing prescription. | astro-ph_CO |
Redshift-space distortions with wide angular separations: Redshift-space distortions are generally considered in the plane parallel
limit, where the angular separation between the two sources can be neglected.
Given that galaxy catalogues now cover large fractions of the sky, it becomes
necessary to consider them in a formalism which takes into account the wide
angle separations. In this article we derive an operational formula for the
matter correlators in the Newtonian limit to be used in actual data sets, both
in configuration and in Fourier spaces without relying on a plane-parallel
approximation. We then recover the plane-parallel limit not only in
configuration space where the geometry is simpler, but also in Fourier space,
and we exhibit the first corrections that should be included in large surveys
as a perturbative expansion over the plane-parallel results. We finally compare
our results to existing literature, and show explicitly how they are related. | astro-ph_CO |
Probing Two-Field Open Inflation by Resonant Signals in Correlation
Functions: We derive oscillatory signals in correlation functions in two-field open
inflation by means of the in-in formalism; such signatures are caused by
resonances between oscillations in the tunnelling field and fluctuations in the
inflaton during the curvature dominated, intermediate and subsequent
inflationary regime. While amplitudes are model-dependent, we find distinct
oscillations in the power and bi-spectrum that can act as a direct probe of the
curvature dominated phase and thus, indirectly, strengthen the claim of the
string landscape if they were observed. We comment on the prospects of
detecting these tell-tale signs in current experiments, which is challenging,
but not impossible.
At the technical level, we pay special attention to the applicability
conditions for truncation fluctuations to the light (inflaton) field and derive
upper limits on the oscillation amplitude of the heavy field. A violation of
these bounds requires a multi-field analysis at the perturbed level. | astro-ph_CO |
Ammonia as a Temperature Tracer in the Ultraluminous Galaxy Merger
Arp220: (abridged) We present ATCA and GBT observations of ammonia (NH3) toward the
ultraluminous infrared galaxy (ULIRG) merger Arp220. We detect the NH3 (1,1),
(2,2), (3,3), (4,4), (5,5), and (6,6) inversion lines in absorption against the
unresolved, (62+/-9)mJy continuum source at 1.2cm. The peak apparent optical
depths of the NH3 lines range from ~0.05 to 0.18. The absorption depth of the
NH3 (1,1) line is significantly shallower than expected based on the depths of
the other transitions, which might be caused by contamination from emission by
a hypothetical, cold (<~20K) gas layer with an estimated column density of <~
2x10^14 cm^-2. The widths of the NH3 absorption lines are ~120-430 km s^-1, in
agreement with those of other molecular tracers. We cannot confirm the
extremely large linewidths of up to ~1800km s^-1 previously reported. We
determine a rotational temperature of (124+/-19)K, corresponding to a kinetic
temperature of T_kin=(186+/-55)K. NH3 column densities depend on the excitation
temperature. For an excitation temperature of 50K, we estimate
(8.4+/-0.5)x10^16cm^-2. The relation scales linearly for possible higher
excitation temperatures. In the context of a model with a molecular ring that
connects the two nuclei in Arp220, we estimate the H2 gas density to be
~f_V^-0.5 x (1-4)x10^3, (f_V: volume filling factor). In addition to NH3, our
ATCA data show an absorption feature adjacent in frequency to the NH3 (3,3)
line. If we interpret the line to be from the OH ^2Pi_3/2 J=9/2 F=4-4
transition, it would have a linewidth, systemic velocity, and apparent optical
depth similar to what we detect in the NH3 lines. If this association with OH
is correct, it marks the first detection of the highly excited (~511K above
ground state) ^2Pi_3/2 J=9/2 F=4-4 OH line in an extragalactic object. | astro-ph_CO |
Redshift Space Distortion of the 21cm Background from the Epoch of
Reionization I: Methodology Re-examined: The peculiar velocity of the intergalactic gas responsible for the cosmic
21cm background from the epoch of reionization and beyond introduces an
anisotropy in the three-dimensional power spectrum of brightness temperature
fluctuations. Measurement of this anisotropy by future 21cm surveys is a
promising tool for separating cosmology from 21cm astrophysics. However,
previous attempts to model the signal have often neglected peculiar velocity or
only approximated it crudely. This paper re-examines the effects of peculiar
velocity on the 21cm signal in detail, improving upon past treatment and
addressing several issues for the first time. (1) We show that properly
accounting for finite optical depth eliminates the unphysical divergence of
21cm brightness temperature in overdense regions of the IGM found by previous
work that employed the usual optically-thin approximation. (2) The
approximation made previously to circumvent the diverging brightness
temperature problem by capping velocity gradient can misestimate the power
spectrum on all scales. (3) The observed power spectrum in redshift-space
remains finite even in the optically-thin approximation if one properly
accounts for the redshift-space distortion. However, results that take full
account of finite optical depth show that this approximation is only accurate
in the limit of high spin temperature. (4) The linear theory for redshift-space
distortion results in ~30% error in the observationally relevant wavenumber
range, at the 50% ionized epoch. (5) We describe and test two numerical schemes
to calculate the 21cm signal from reionization simulations to incorporate
peculiar velocity effects in the optically-thin approximation accurately. One
is particle-based, the other grid-based, and while the former is most accurate,
we demonstrate that the latter is computationally more efficient and can
achieve sufficient accuracy. [Abridged] | astro-ph_CO |
Is a co-rotating Dark Disk a threat to Dark Matter Directional Detection
?: Recent N-Body simulations are in favor of the presence of a co-rotating Dark
Disk that might contribute significantly (10%-50%) to the local Dark Matter
density. Such substructure could have dramatic effect on directional detection.
Indeed, in the case of a null lag velocity, one expects an isotropic WIMP
velocity distribution arising from the Dark Disk contribution, which might
weaken the strong angular signature expected in directional detection. For a
wide range of Dark Disk parameters, we evaluate in this Letter the effect of
such dark component on the discovery potential of upcoming directional
detectors. As a conclusion of our study, using only the angular distribution of
nuclear recoils, we show that Dark Disk models as suggested by recent N-Body
simulations will not affect significantly the Dark Matter reach of directional
detection, even in extreme configurations. | astro-ph_CO |
Supernovae in paired galaxies: We investigate the influence of close neighbor galaxies on the properties of
supernovae (SNe) and their host galaxies using 56 SNe located in pairs of
galaxies with different levels of star formation (SF) and nuclear activity. The
mean distance of type II SNe from nuclei of hosts is greater by about a factor
of 2 than that of type Ibc SNe. The distributions and mean distances of SNe are
consistent with previous results compiled with the larger sample. For the first
time it is shown that SNe Ibc are located in pairs with significantly smaller
difference of radial velocities between components than pairs containing SNe Ia
and II. We consider this as a result of higher star formation rate (SFR) of
these closer systems of galaxies. | astro-ph_CO |
Optimal non-linear transformations for large scale structure statistics: Recently, several studies proposed non-linear transformations, such as a
logarithmic or Gaussianization transformation, as efficient tools to recapture
information about the (Gaussian) initial conditions. During non-linear
evolution, part of the cosmologically relevant information leaks out from the
second moment of the distribution. This information is accessible only through
complex higher order moments or, in the worst case, becomes inaccessible to the
hierarchy. The focus of this work is to investigate these transformations in
the framework of Fisher information using cosmological perturbation theory of
the matter field with Gaussian initial conditions. We show that at each order
in perturbation theory, there is a polynomial of corresponding order exhausting
the information on a given parameter. This polynomial can be interpreted as the
Taylor expansion of the maximally efficient "sufficient" observable in the
non-linear regime. We determine explicitly this maximally efficient observable
for local transformations. Remarkably, this optimal transform is essentially
the simple power transform with an exponent related to the slope of the power
spectrum; when this is -1, it is indistinguishable from the logarithmic
transform. This transform Gaussianizes the distribution, and recovers the
linear density contrast. Thus a direct connection is revealed between undoing
of the non-linear dynamics and the efficient capture of Fisher information. Our
analytical results were compared with measurements from the Millennium
Simulation density field. We found that our transforms remain very close to
optimal even in the deeply non-linear regime with \sigma^2 \sim 10. | astro-ph_CO |
The Ultraluminous State: (Abridged) We revisit the question of the nature of ULXs through a detailed
investigation of their spectral shape, using the highest quality X-ray data
available in the XMM-Newton public archives. We confirm that simple spectral
models commonly used for the analysis and interpretation of ULXs (power-law
continuum and multi-colour disc blackbody models) are inadequate in the face of
such high quality data. Instead we find two near ubiquitous features in the
spectrum: a soft excess and a roll-over in the spectrum at energies above 3keV.
We investigate a range of more physical models to describe these data. We find
that disc plus Comptonised corona models fit the data well, but the derived
corona is cool, and optically thick (tau ~ 5-30). We argue that these observed
disc temperatures are not a good indicator of the black hole mass as the
powerful, optically thick corona drains energy from the inner disc, and
obscures it. We estimate the intrinsic (corona-less) disc temperature, and
demonstrate that in most cases it lies in the regime of stellar mass black
holes. These objects have spectra which range from those similar to the highest
mass accretion rate states in Galactic binaries, to those which clearly have
two peaks, one at energies below 1 keV (from the outer, unComptonised disc) and
one above 3 keV (from the Comptonised, inner disc). However, a few ULXs have a
significantly cooler corrected disc temperature; we suggest that these are the
most extreme stellar mass black hole accretors, in which a massive wind
completely envelopes the inner disc regions, creating a cool photosphere. We
conclude that ULXs provide us with an observational template for the transition
between Eddington and super-Eddington accretion flows, with the latter
occupying a new ultraluminous accretion state. | astro-ph_CO |
Evidence for massive neutrinos from CMB and lensing observations: We discuss whether massive neutrinos (either active or sterile) can reconcile
some of the tensions within cosmological data that have been brought into focus
by the recently released {\it Planck} data. We point out that a discrepancy is
present when comparing the primary CMB and lensing measurements both from the
CMB and galaxy lensing data using CFHTLenS, similar to that which arises when
comparing CMB measurements and SZ cluster counts. A consistent picture emerges
and including a prior for the cluster constraints and BAOs we find that: for an
active neutrino model with 3 degenerate neutrinos, $\sum m_{\nu}= (0.320 \pm
0.081)\,{\rm eV}$, whereas for a sterile neutrino, in addition to 3 neutrinos
with a standard hierarchy and $\sum m_{\nu}= 0.06\,{\rm eV}$, $m_{\nu, \, \rm
sterile}^{\rm eff}= (0.450 \pm 0.124)\,{\rm eV}$ and $\Delta N_{\rm eff} = 0.45
\pm 0.23$. In both cases there is a significant detection of modification to
the neutrino sector from the standard model and in the case of the sterile
neutrino it is possible to reconcile the BAO and local $H_0$ measurements.
However, a caveat to our result is some internal tension between the CMB and
lensing/cluster observations, and the masses are in excess of those estimated
from the shape of the matter power spectrum from galaxy surveys. | astro-ph_CO |
Indirect Detection of Decaying Dark Matter with High Angular Resolution:
Case for axion search by IRCS at Subaru Telescope: Recent advances in cosmic-ray detectors have provided exceptional
sensitivities of dark matter with high angular resolution. Motivated by this,
we present a comprehensive study of cosmic-ray flux from dark matter decay in
dwarf spheroidal galaxies (dSphs), with a focus on detectors possessing
arcsecond-level field of view and/or angular resolution. We propose to use
differential $D$-factors, which are estimated for various dSphs since such
detectors are sensitive to their dark matter distributions. Our findings reveal
that the resulting signal flux can experience a more than $O$(1-10) enhancement
with different theoretical uncertainty compared to traditional estimations.
Based on this analysis, we find that the Infrared Camera and Spectrograph
(IRCS) installed on the 8.2m Subaru telescope can be a good dark matter
detector for the mass in the eV range, particularly axion-like particles
(ALPs). Observing the Draco or Ursa Major II galaxies with the IRCS for just a
few nights will be sufficient to surpass the stellar cooling bounds for ALP
dark matter with a mass in the range of $1\,{\rm eV} \lesssim m_a \lesssim
2\,\rm eV$. | astro-ph_CO |
AGN feedback in galaxy groups: a joint GMRT/X-ray study: We present an ongoing study of 18 nearby galaxy groups, chosen for the
availability of Chandra and/or XMM-Newton data and evidence for AGN/hot
intragroup gas interaction. We have obtained 235 and 610 MHz observations at
the GMRT for all the groups, and 327 and 150 MHz for a few. We discuss two
interesting cases - NGC 5044 and AWM 4 - which exhibit different kinds of
AGN/hot gas interaction. With the help of these examples we show how joining
low-frequency radio data (to track the history of AGN outbursts through
emission from aged electron populations) with X-ray data (to determine the
state of hot gas, its disturbances, heating and cooling) can provide a unique
insight into the nature of the feedback mechanism in galaxy groups. | astro-ph_CO |
Phenomenological consequences of superfluid dark matter with
baryon-phonon coupling: Recently, a new form of dark matter has been suggested to naturally reproduce
the empirically successful aspects of Milgrom's law in galaxies. The dark
matter particle candidates are axion-like, with masses of order eV and strong
self-interactions. They Bose-Einstein condense into a superfluid phase in the
central regions of galaxy halos. The superfluid phonon excitations in turn
couple to baryons and mediate an additional long-range force. For a suitable
choice of the superfluid equation of state, this force can mimic Milgrom's law.
In this paper we develop in detail some of the main phenomenological
consequences of such a formalism, by revisiting the expected dark matter halo
profile in the presence of an extended baryon distribution. In particular, we
show how rotation curves of both high and low surface brightness galaxies can
be reproduced, with a slightly rising rotation curve at large radii in massive
high surface brightness galaxies, thus subtly different from Milgrom's law. We
finally point out other expected differences with Milgrom's law, in particular
in dwarf spheroidal satellite galaxies, tidal dwarf galaxies, and globular
clusters, whose Milgromian or Newtonian behavior depends on the position with
respect to the superfluid core of the host galaxy. We also expect ultra-diffuse
galaxies within galaxy clusters to have velocities slightly above the baryonic
Tully-Fisher relation. Finally, we note that, in this framework, photons and
gravitons follow the same geodesics, and that galaxy-galaxy lensing, probing
larger distances within galaxy halos than rotation curves, should follow
predictions closer to the standard cosmological model than those of Milgrom's
law. | astro-ph_CO |
Cosmological Implications of the Tetron Model of Elementary Particles: Based on a possible solution to the tetron spin problem, a modification of
the standard Big Bang scenario is suggested, where the advent of a spacetime
manifold is connected to the appearance of tetronic bound states. The metric
tensor is constructed from tetron constituents and the reason for cosmic
inflation is elucidated. Furthermore, there are natural dark matter candidates
in the tetron model. The ratio of ordinary to dark matter in the universe is
calculated to be 1:5. | astro-ph_CO |
Probing high-redshift quasars with ALMA. I. Expected observables and
potential number of sources: (abridged) We explore how ALMA observations can probe high-redshift galaxies
in unprecedented detail. We discuss the main observables that are excited by
the large-scale starburst, and formulate expectations for the chemistry and the
fluxes in the center of active galaxies, where chemistry may be driven by the
absorption of X-ray photons. We show that such X-ray dominated regions (XDRs)
should be large enough to be resolved with ALMA, and predict the expected
amount of emission in CO and various fine-structure lines. We discuss how such
XDRs can be distinguished from a strong starburst on the same spatial scales
based on the CO line SED. Our models are compared to known sources like NGC
1068 and APM 08279. We also analyze the properties of the z=6.42 quasar SDSS
J114816.64+525150.3, and find that the observed emission in CO, [CII] and [CI]
requires a dense warm and a low-density cold gas component. We estimate the
expected number of sources at redshifts higher than 6, finding that one could
expect one black hole with $10^6$ solar masses per arcmin$^2$. | astro-ph_CO |
The Accretion Disc Particle Method for Simulations of Black Hole Feeding
and Feedback: Black holes grow by accreting matter from their surroundings. However,
angular momentum provides an efficient natural barrier to accretion and so only
the lowest angular momentum material will be available to feed the black holes.
The standard sub-grid model for black hole accretion in galaxy formation
simulations - based on the Bondi-Hoyle method - does not account for the
angular momentum of accreting material, and so it is unclear how representative
the black hole accretion rate estimated in this way is likely to be. In this
paper we introduce a new sub-grid model for black hole accretion that naturally
accounts for the angular momentum of accreting material. Both the black hole
and its accretion disc are modelled as a composite accretion disc particle. Gas
particles are captured by the accretion disc particle if and only if their
orbits bring them within its accretion radius R_acc, at which point their mass
is added to the accretion disc and feeds the black hole on a viscous timescale
t_visc. The resulting black hole accretion rate (dM/dt)_BH powers the accretion
luminosity L_acc ~ (dM/dt)_BH, which drives black hole feedback. Using a series
of controlled numerical experiments, we demonstrate that our new accretion disc
particle method is more physically self-consistent than the Bondi-Hoyle method.
We also discuss the physical implications of the accretion disc particle method
for systems with a high degree of rotational support, and we argue that the
M_BH-sigma relation in these systems should be offset from the relation for
classical bulges and ellipticals, as appears to be observed. | astro-ph_CO |
A highly precise shear bias estimator independent of the measured shape
noise: We present a new method to estimate shear measurement bias in image
simulations that significantly improves the precision with respect to current
techniques. Our method is based on measuring the shear response for individual
images. We generated sheared versions of the same image to measure how the
galaxy shape changes with the small applied shear. This shear response is the
multiplicative shear bias for each image. In addition, we also measured the
individual additive bias. Using the same noise realizations for each sheared
version allows us to compute the shear response at very high precision. The
estimated shear bias of a sample of galaxies is then the average of the
individual measurements. The precision of this method leads to an improvement
with respect to previous methods concerned with the precision of estimates of
multiplicative bias since our method is not affected by noise from shape
measurements, which until now has been the dominant uncertainty. As a
consequence, the method does not require shape-noise suppression for a precise
estimation of shear multiplicative bias. Our method can be readily used for
numerous applications such as shear measurement validation and calibration,
reducing the number of necessary simulated images by a few orders of magnitude
to achieve the same precision. | astro-ph_CO |
Diffuse optical intracluster light as a measure of stellar tidal
stripping: the cluster CL0024+17 at $z\sim $0.4 observed at LBT: We have evaluated the diffuse intracluster light (ICL) in the central core of
the galaxy cluster CL0024+17 at $z\sim 0.4$ observed with the prime focus
camera (LBC) at LBT. The measure required an accurate removal of the galaxies
light within $\sim 200$ kpc from the center. The residual background intensity
has then been integrated in circular apertures to derive the average ICL
intensity profile. The latter shows an approximate exponential decline as
expected from theoretical cold dark matter models. The radial profile of the
ICL over the galaxies intensity ratio (ICL fraction) is increasing with
decreasing radius but near the cluster center it starts to bend and then
decreases where the overlap of the halos of the brightest cluster galaxies
becomes dominant. Theoretical expectations in a simplified CDM scenario show
that the ICL fraction profile can be estimated from the stripped over galaxy
stellar mass ratio in the cluster. It is possible to show that the latter
quantity is almost independent of the properties of the individual host
galaxies but mainly depends on the average cluster properties. The predicted
ICL fraction profile is thus very sensitive to the assumed CDM profile, total
mass and concentration parameter of the cluster. Adopting values very similar
to those derived from the most recent lensing analysis in CL0024+17 we find a
good agreement with the observed ICL fraction profile. The galaxy counts in the
cluster core have then been compared with that derived from composite cluster
samples in larger volumes, up to the clusters virial radius. The galaxy counts
in the CL0024+17 core appear flatter and the amount of bending respect to the
average cluster galaxy counts imply a loss of total emissivity in broad
agreement with the measured ICL fraction. | astro-ph_CO |
Are Newly Discovered HI High Velocity Clouds Minihalos in the Local
Group?: A set of HI sources extracted from the north Galactic polar region by the
ongoing ALFALFA survey has properties that are consistent with the
interpretation that they are associated with isolated minihalos in the
outskirts of the Local Group (LG). Unlike objects detected by previous surveys,
such as the Compact High Velocity Clouds of Braun & Burton (1999), the HI
clouds found by ALFALFA do not violate any structural requirements or halo
scaling laws of the LambdaCDM structure paradigm, nor would they have been
detected by extant HI surveys of nearby galaxy groups other than the LG. At a
distance of d Mpc, their HI masses range between $5 x 10^4 d^2 and 10^6 d^2
solar and their HI radii between <0.4d and 1.6 d kpc. If they are parts of
gravitationally bound halos, the total masses would be on order of 10^8--10^9
solar, their baryonic content would be signifcantly smaller than the cosmic
fraction of 0.16 and present in a ionized gas phase of mass well exceeding that
of the neutral phase. This study does not however prove that the minihalo
interpretation is unique. Among possible alternatives would be that the clouds
are shreds of the Leading Arm of the Magellanic Stream. | astro-ph_CO |
Is the lack of power anomaly in the CMB correlated with the orientation
of the Galactic plane?: The lack of power at large angular scales in the CMB temperature anisotropy
pattern is a feature known to depend on the size of the Galactic mask. Not only
the large scale anisotropy power in the CMB is lower than the best-fit
$\Lambda$CDM model predicts, but most of the power seems to be localised close
to the Galactic plane, making high-Galactic latitude regions more anomalous. We
assess how likely the latter behaviour is in a $\Lambda$CDM model by extracting
simulations from the {\it Planck} 2018 fiducial model. By comparing the former
to {\it Planck} data in different Galactic masks, we reproduce the anomaly
found in previous works, at a statistical significance of $\sim 3 \, \sigma$.
This result suggests the existence of a bizzarre correlation between the
particular orientation of the Galaxy and the lack of power anomaly. To test
this hypothesis, we perform random rotations of the {\it Planck} 2018 data and
compare these to similarly rotated $\Lambda$CDM realisations. We find that,
among all possible rotations, the lower-tail probability of the observed
high-Galactic latitude data variance is still low at the level of $2.8 \,
\sigma$. Furthermore, the lowering trend of the variance when moving from low-
to high-Galactic latitude is anomalous in the data at $\sim 3\,\sigma$ when
comparing to $\Lambda$CDM rotated realisations. This shows that the lack of
power at high Galactic latitude is substantially stable against the "look
elsewhere" effect induced by random rotations of the Galaxy orientation.
Moreover, this analysis turns out to be substantially stable if we employ, in
place of generic $\Lambda$CDM simulations, a specific set whose variance is
constrained to reproduce the observed data variance. | astro-ph_CO |
cosmoabc: Likelihood-free inference via Population Monte Carlo
Approximate Bayesian Computation: Approximate Bayesian Computation (ABC) enables parameter inference for
complex physical systems in cases where the true likelihood function is
unknown, unavailable, or computationally too expensive. It relies on the
forward simulation of mock data and comparison between observed and synthetic
catalogues. Here we present cosmoabc, a Python ABC sampler featuring a
Population Monte Carlo (PMC) variation of the original ABC algorithm, which
uses an adaptive importance sampling scheme. The code is very flexible and can
be easily coupled to an external simulator, while allowing to incorporate
arbitrary distance and prior functions. As an example of practical application,
we coupled cosmoabc with the numcosmo library and demonstrate how it can be
used to estimate posterior probability distributions over cosmological
parameters based on measurements of galaxy clusters number counts without
computing the likelihood function. cosmoabc is published under the GPLv3
license on PyPI and GitHub and documentation is available at
http://goo.gl/SmB8EX | astro-ph_CO |
A designer approach to $f(Q)$ gravity and cosmological implications: We investigate the evolution of linear perturbations in the Symmetric
Teleparallel Gravity, namely $f(Q)$ gravity, for which we design the $f(Q)$
function to match specific expansion histories. We consider different
evolutions of the effective dark energy equation of state, $w_Q(a)$, which
includes $w_Q=-1$, a constant $w_Q \neq -1$ and a fast varying equation of
state. We identify clear patterns in the effective gravitational coupling,
which accordingly modifies the linear growth of large scale structures. We
provide theoretical predictions for the product of the growth rate $\tilde{f}$
and the root mean square of matter fluctuations $\sigma_8$, namely
$\tilde{f}\sigma_8$ and for the sign of the cross-correlation power spectrum of
the galaxy fluctuations and the cosmic microwave background radiation
anisotropies. These properties can be used to distinguish the $f(Q)$ gravity
from the standard cosmological model using accurate cosmological observations. | astro-ph_CO |
Accelerating MCMC algorithms through Bayesian Deep Networks: Markov Chain Monte Carlo (MCMC) algorithms are commonly used for their
versatility in sampling from complicated probability distributions. However, as
the dimension of the distribution gets larger, the computational costs for a
satisfactory exploration of the sampling space become challenging. Adaptive
MCMC methods employing a choice of proposal distribution can address this issue
speeding up the convergence. In this paper we show an alternative way of
performing adaptive MCMC, by using the outcome of Bayesian Neural Networks as
the initial proposal for the Markov Chain. This combined approach increases the
acceptance rate in the Metropolis-Hasting algorithm and accelerate the
convergence of the MCMC while reaching the same final accuracy. Finally, we
demonstrate the main advantages of this approach by constraining the
cosmological parameters directly from Cosmic Microwave Background maps. | astro-ph_CO |
Constraints on Cosmographic Functions of Cosmic Chronometers Data Using
Gaussian Processes: We study observational constraints on the cosmographic functions up to the
fourth derivative of the scale factor with respect to cosmic time, i.e., the
so-called snap function, using the non-parametric method of Gaussian Processes.
As observational data we use the Hubble parameter data. Also we use mock data
sets to estimate the future forecast and study the performance of this type of
data to constrain cosmographic functions. The combination between a
non-parametric method and the Hubble parameter data is investigated as a
strategy to reconstruct cosmographic functions. In addition, our results are
quite general because they are not restricted to a specific type of functional
dependency of the Hubble parameter. We investigate some advantages of using
cosmographic functions instead of cosmographic series, since the former are
general definitions free of approximations. In general, our results do not
deviate significantly from $\Lambda CDM$. We determine a transition redshift
$z_{tr}=0.637^{+0.165}_{-0.175}$ and $H_{0}=69.45 \pm 4.34$. Also assuming
priors for the Hubble constant we obtain $z_{tr}=0.670^{+0.210}_{-0.120}$ with
$H_{0}=67.44$ (Planck) and $z_{tr}=0.710^{+0.159}_{-0.111}$ with
$H_{0}=74.03$(SH0ES). Our main results are summarized in table 2. | astro-ph_CO |
Observational Constraints on the Modified Gravity Model (MOG) Proposed
by Moffat: Using the Magellanic System: A simple model for the dynamics of the Magellanic Stream (MS), in the
framework of modified gravity models is investigated. We assume that the galaxy
is made up of baryonic matter out of context of dark matter scenario. The model
we used here is named Modified Gravity (MOG) proposed by Moffat (2005). In
order to examine the compatibility of the overall properties of the MS under
the MOG theory, the observational radial velocity profile of the MS is compared
with the numerical results using the $\chi^2$ fit method. In order to obtain
the best model parameters, a maximum likelihood analysis is performed. We also
compare the results of this model with the Cold Dark Matter (CDM) halo model
and the other alternative gravity model that proposed by Bekenstein (2004), so
called TeVeS. We show that by selecting the appropriate values for the free
parameters, the MOG theory seems to be plausible to explain the dynamics of the
MS as well as the CDM and the TeVeS models. | astro-ph_CO |
A numerical study of pseudoscalar inflation with an axion-gauge field
coupling: A numerical study of a pseudoscalar inflation having an axion-photon-like
coupling is performed by solving numerically the coupled differential equations
of motion for inflaton and photon mode functions from the onset of inflation to
the end of reheating. The backreaction due to particle production is also
included self-consistently. We find that this particular inflation model
realizes the idea of a warm inflation in which a steady thermal bath is
established by the particle production. In most cases this thermal bath exceeds
the amount of radiation released in the reheating process. In the strong
coupling regime, the transition from the inflationary to the
radiation-dominated phase does not involve either a preheating or reheating
process. In addition, energy density peaks produced near the end of inflation
may lead to the formation of primordial black holes. | astro-ph_CO |
Higgs-induced spectroscopic shifts near strong gravity sources: We explore the consequences of the mass generation due to the Higgs field in
strong gravity astrophysical environments. The vacuum expectation value of the
Higgs field is predicted to depend on the curvature of spacetime, potentially
giving rise to peculiar spectroscopic shifts, named hereafter "Higgs shifts."
Higgs shifts could be searched through dedicated multiwavelength and
multispecies surveys with high spatial and spectral resolution near strong
gravity sources such as Sagittarius A* or broad searches for signals due to
primordial black holes. The possible absence of Higgs shifts in these surveys
should provide limits to the coupling between the Higgs particle and the
curvature of spacetime, a topic of interest for a recently proposed
Higgs-driven inflationary model. We discuss some conceptual issues regarding
the coexistence between the Higgs mechanism and gravity, especially for their
different handling of fundamental and composite particles. | astro-ph_CO |
Exploring the Dark Universe: constraints on dynamical Dark Energy models
from CMB, BAO and growth rate measurements: In order to explain the current acceleration of the Universe, the fine tuning
problem of the cosmological constant $\Lambda$ and the cosmic coincidence
problem, different alternative models have been proposed in the literature. We
use the most recent observational data from CMB (Planck 2018 final data
release) and LSS (SDSS, WiggleZ, VIPERS) to constrain dynamical dark energy
(DE) models. The CMB shift parameter, which traditionally has been used to
determine the main cosmological parameters of the standard model $\Lambda CDM$
is employed in addition to data from redshift-space distortions through the
growth parameter $A(z)=f(z)\sigma_{8}(z)$ to constrain the mass variance
$\sigma_{8}$. BAO data is also used to study the history of the cosmological
expansion and the main properties of DE. From the evolution of $q(z)$ we found
a slowdown of acceleration behaviour at low redshifts, and by using the Akaike
and Bayesian Information Criterion (AIC, BIC) we discriminate different models
those that are better suited to the observational data, finding that the
interactive dark energy (IDE) model is the most favoured by observational data,
including information from SNIa and Hz. The analysis shows that the IDE model
is followed closely by EDE and $\Lambda CDM$ models, which in some cases fit
better the observational data with individual probes. | astro-ph_CO |
Constraint on Heavy Element Production in Inhomogeneous Big-Bang
Nucleosynthesis from The Light-Element Observations: We investigate the observational constraints on the inhomogeneous big-bang
nucleosynthesis that Matsuura et al. suggested the possibility of the heavy
element production beyond ${}^7$Li in the early universe. From the
observational constraints on light elements of ${}^4$He and D, possible regions
are found on the plane of the volume fraction of the high density region
against the ratio between high-and low-density regions. In these allowed
regions, we have confirmed that the heavy elements beyond Ni can be produced
appreciably, where $p$- and/or $r$-process elements are produced well
simultaneously. | astro-ph_CO |
The coordinated key role of wet, mixed, and dry major mergers in the
buildup of massive early-type galaxies at z<~1: Hierarchical models predict that massive early-type galaxies (mETGs) derive
from the most massive and violent merging sequences occurred in the Universe.
However, the role of wet, mixed, and dry major mergers in the assembly of mETGs
is questioned by some recent observations. We have developed a semi-analytical
model to test the feasibility of the major-merger origin hypothesis for mETGs,
just accounting for the effects on galaxy evolution of the major mergers
strictly reported by observations. The model proves that it is feasible to
reproduce the observed number density evolution of mETGs since z~1, just
accounting for the coordinated effects of wet/mixed/dry major mergers. It can
also reconcile the different assembly redshifts derived by hierarchical models
and by mass downsizing data for mETGs, just considering that a mETG observed at
a certain redshift is not necessarily in place since then. The model predicts
that wet major mergers have controlled the mETGs buildup since z~1, although
dry and mixed mergers have also played an essential role in it. The bulk of
this assembly took place at 0.7<z<1, being nearly frozen at z<~0.7 due to the
negligible number of major mergers occurred per existing mETG since then. The
model suggests that major mergers have been the main driver for the
observational migration of mass from the massive end of the blue galaxy cloud
to that of the red sequence in the last ~8 Gyr. | astro-ph_CO |
The Merger Rate of Primordial Black Hole-Neutron Star Binaries in
Ellipsoidal-Collapse Dark Matter Halo Models: Primordial black holes (PBHs), as a potential macroscopic candidate for dark
matter, can encounter other compact objects in dark matter halos because of
their random distribution. Besides, the detection of gravitational waves (GWs)
related to the stellar-mass black hole-neutron star (BH-NS) mergers raises the
possibility that the BHs involved in such events may have a primordial origin.
In this work, we calculate the merger rate of PBH-NS binaries within the
framework of ellipsoidal-collapse dark matter halo models and compare it with
the corresponding results derived from spherical-collapse dark matter halo
models. Our results exhibit that ellipsoidal-collapse dark matter halo models
can potentially amplify the merger rate of PBH-NS binaries in such a way that
it is very close to the range estimated by the LIGO-Virgo observations. While
spherical-collapse dark matter halo models cannot justify PBH-NS merger events
as consistent results with the latest GW data reported by the LIGO-Virgo
collaboration. In addition, we calculate the merger rate of PBH-NS binaries as
a function of PBH mass and fraction within the context of ellipsoidal-collapse
dark matter halo models. The results indicate that PBH-NS merger events with
the mass of $(M_{PBH}\le 5 M_{\odot}, M_{NS}\simeq 1.4 M_{\odot})$ will be
consistent with the LIGO-Virgo observations if $f_{PBH}\simeq 1$. We also show
that to have at least on $(M_{PBH}\simeq 5 M_{\odot}, M_{NS}\simeq 1.4
M_{\odot})$ event in the comoving volume $1 Gpc^{3}$ annually,
ellipsoidal-collapse dark matter halo models constrain the abundance of PBHs as
$f_{PBH} \geq 0.1$. | astro-ph_CO |
Beyond Spherical Top Hat Collapse: We study the evolution of inhomogeneous spherical perturbations in the
universe in a way that generalizes the spherical top hat collapse in a
straightforward manner. For that purpose we derive a dynamical equation for the
evolution of the density contrast in the context of a Lemaitre-Tolman-Bondi
metric and construct solutions with and without a cosmological constant for the
evolution of a spherical perturbation with a given initial radial profile. | astro-ph_CO |
Learning from Topology: Cosmological Parameter Estimation from the
Large-scale Structure: The topology of the large-scale structure of the universe contains valuable
information on the underlying cosmological parameters. While persistent
homology can extract this topological information, the optimal method for
parameter estimation from the tool remains an open question. To address this,
we propose a neural network model to map persistence images to cosmological
parameters. Through a parameter recovery test, we demonstrate that our model
makes accurate and precise estimates, considerably outperforming conventional
Bayesian inference approaches. | astro-ph_CO |
The eROSITA view of the Abell 3391/95 field: The Northern Clump. The
largest infalling structure in the longest known gas filament observed with
eROSITA, XMM-Newton, and Chandra: SRG/eROSITA PV observations revealed the A3391/95 cluster system and the
Northern Clump (MCXC J0621.7-5242 galaxy cluster) are aligning along a cosmic
filament in soft X-rays, similarly to what has been seen in simulations before.
We aim to understand the dynamical state of the Northern Clump as it enters the
atmosphere ($3\times R_{200}$) of A3391. We analyzed joint eROSITA, XMM-Newton,
and Chandra observations to probe the morphological, thermal, and chemical
properties of the Northern Clump from its center out to a radius of 988 kpc
($R_{200}$). We utilized the ASKAP/EMU radio data, DECam optical image, and
Planck y-map to study the influence of the WAT radio source on the Northern
Clump central ICM. From the Magneticum simulation, we identified an analog of
the A3391/95 system along with an infalling group resembling the Northern
Clump. The Northern Clump is a WCC cluster centered on a WAT radio galaxy. The
gas temperature over $0.2-0.5R_{500}$ is $k_BT_{500}=1.99\pm0.04$ keV. We
employed the $M-T$ scaling relation and obtained a mass estimate of
$M_{500}=(7.68\pm0.43)\times10^{13}M_{\odot}$ and $R_{500}=(636\pm12)$ kpc. Its
atmosphere has a boxy shape and deviates from spherical symmetry. We identify a
southern surface brightness edge, likely caused by subsonic motion relative to
the filament gas. At $\sim\! R_{500}$, the southern atmosphere appears to be
42% hotter than its northern atmosphere. We detect a downstream tail pointing
toward the north with a projected length of $\sim318$ kpc, plausibly the result
of ram pressure stripping. The analog group in the Magneticum simulation is
experiencing changes in its gas properties and a shift between the position of
the halo center and that of the bound gas while approaching the main cluster
pair. | astro-ph_CO |
Strong lensing modeling in galaxy clusters as a promising method to test
cosmography I. Parametric dark energy models: In this paper we probe five cosmological models for which the dark energy
equation of state parameter, $w(z)$, is parameterized as a function of redshift
using strong lensing data in the galaxy cluster Abell 1689. We constrain the
parameters of the $w(z)$ functions by reconstructing the lens model under each
one of these cosmologies with strong lensing measurements from two galaxy
clusters: Abell 1689 and a mock cluster, Ares, from the Hubble Frontier Fields
Comparison Challenge, to validate our methodology. To quantify how the
cosmological constraints are biased due to systematic effects in the strong
lensing modeling, we carry out three runs considering the following
uncertainties for the multiple images positions: 0.25", 0.5", and 1.0". With
Ares, we find that larger errors decrease the systematic bias on the estimated
cosmological parameters. With real data, our strong-lensing constraints on
$w(z)$ are consistent those derived from other cosmological probes. We confirm
that strong lensing cosmography with galaxy clusters is a promising method to
constrain $w(z)$ parameterizations. A better understanding of galaxy clusters
and their environment is however needed to improve the SL modeling and hence to
estimate stringent cosmological parameters in alternatives cosmologies. | astro-ph_CO |
Implications of multiple high-redshift galaxy clusters: To date, 14 high-redshift (z>1.0) galaxy clusters with mass measurements have
been observed, spectroscopically confirmed and are reported in the literature.
These objects should be exceedingly rare in the standard LCDM model. We
conservatively approximate the selection functions of these clusters' parent
surveys, and quantify the tension between the abundances of massive clusters as
predicted by the standard LCDM model and the observed ones. We alleviate the
tension considering non-Gaussian primordial perturbations of the local type,
characterized by the parameter fnl and derive constraints on fnl arising from
the mere existence of these clusters. At the 95% confidence level, fnl>467 with
cosmological parameters fixed to their most likely WMAP5 values, or fnl > 123
(at 95% confidence) if we marginalize over WMAP5 parameters priors. In
combination with fnl constraints from Cosmic Microwave Background and halo
bias, this determination implies a scale-dependence of fnl at approx. 3 sigma.
Given the assumptions made in the analysis, we expect any future improvements
to the modeling of the non-Gaussian mass function, survey volumes, or selection
functions to increase the significance of fnl>0 found here. In order to
reconcile these massive, high-z clusters with an fnl=0, their masses would need
to be systematically lowered by 1.5 sigma or the sigma8 parameter should be
approx. 3 sigma higher than CMB (and large-scale structure) constraints. The
existence of these objects is a puzzle: it either represents a challenge to the
LCDM paradigme or it is an indication that the mass estimates of clusters is
dramatically more uncertain than we think. | astro-ph_CO |
Cosmological observations in the radio domain: the contribution of
extragalactic sources: The low frequency tail of the CMB spectrum, down along the radio range (~1
GHz), may carry weak spectral distortions which are fingerprints of processes
occurred during different epochs of the thermal history of the Universe, from
z~3\times 10^6 to reionization. TRIS and ARCADE2 are the most recent
experiments dedicated to the exploration of this chapter of CMB cosmology. The
level of instrumental accuracy they reached in the determination of the
absolute sky temperature is such that the removal of galactic and
extra-galactic contamination is the true bottleneck towards the recovery of the
cosmological signal. This will be certainly the case also for future
experiments in the radio domain. Here we present an update of a study
originally done to recognize the contribution of unresolved extra-galactic
radio sources to the sky brightness measured by TRIS. Despite the specific
context which originated our analysis, this is a study of general interest,
improved by the inclusion of all the source counts available up-to-date from
150 MHz to 8.4 GHz. | astro-ph_CO |
Evolution of the $fσ_8$ tension with the Planck15/$Λ$CDM
determination and implications for modified gravity theories: We construct an updated extended compilation of distinct (but possibly
correlated) $f\sigma_8(z)$ Redshift Space Distortion (RSD) data published
between 2006 and 2018. It consists of 63 datapoints and is significantly larger
than previously used similar datasets. After fiducial model correction we
obtain the best fit $\Omega_{0m}-\sigma_8$ $\Lambda$CDM parameters and show
that they are at a $5\sigma$ tension with the corresponding
Planck15/$\Lambda$CDM values. Introducing a nontrivial covariance matrix
correlating randomly $20\%$ of the RSD datapoints has no significant effect on
the above tension level. We show that the tension disappears (becomes less than
$1\sigma$) when a subsample of the 20 most recently published data is used. A
partial cause for this reduced tension is the fact that more recent data tend
to probe higher redshifts (with higher errorbars) where there is degeneracy
among different models due to matter domination. Allowing for a nontrivial
evolution of the effective Newton's constant as
$G_{\textrm{eff}}(z)/G_{\textrm{N}} = 1 + g_a \left(\frac{z}{1+z}\right)^2 -
g_a \left(\frac{z}{1+z}\right)^4$ ($g_a$ is a parameter) and fixing a \plcdm
background we find $g_a=-0.91\pm 0.17$ from the full $f\sigma_8$ dataset while
the 20 earliest and 20 latest datapoints imply $g_a=-1.28^{+0.28}_{-0.26}$ and
$g_a=-0.43^{+0.46}_{-0.41}$ respectively. Thus, the more recent $f\sigma_8$
data appear to favor GR in contrast to earlier data. Finally, we show that the
parametrization $f\sigma_8(z)=\lambda \sigma_8 \Omega(z)^\gamma /(1+z)^\beta$
provides an excellent fit to the solution of the growth equation for both GR
($g_a=0$) and modified gravity ($g_a\neq 0$). | astro-ph_CO |
Sensitivity and foreground modelling for large-scale CMB B-mode
polarization satellite missions: The measurement of the large-scale B-mode polarization in the cosmic
microwave background (CMB) is a fundamental goal of future CMB experiments.
However, because of unprecedented sensitivity, future CMB experiments will be
much more sensitive to any imperfect modelling of the Galactic foreground
polarization in the reconstruction of the primordial B-mode signal. We compare
the sensitivity to B-modes of different concepts of CMB satellite missions
(LiteBIRD, COrE, COrE+, PRISM, EPIC, PIXIE) in the presence of Galactic
foregrounds. In particular, we quantify the impact on the tensor-to-scalar
parameter of incorrect foreground modelling in the component separation
process. Using Bayesian fitting and Gibbs sampling, we perform the separation
of the CMB and Galactic foreground B-modes. The recovered CMB B-mode power
spectrum is used to compute the likelihood distribution of the tensor-to-scalar
ratio. We focus the analysis to the very large angular scales that can be
probed only by CMB space missions, i.e. the Reionization bump, where primordial
B-modes dominate over spurious B-modes induced by gravitational lensing. We
find that fitting a single modified blackbody component for thermal dust where
the "real" sky consists of two dust components strongly bias the estimation of
the tensor-to-scalar ratio by more than 5{\sigma} for the most sensitive
experiments. Neglecting in the parametric model the curvature of the
synchrotron spectral index may bias the estimated tensor-to-scalar ratio by
more than 1{\sigma}. For sensitive CMB experiments, omitting in the foreground
modelling a 1% polarized spinning dust component may induce a non-negligible
bias in the estimated tensor-to-scalar ratio. | astro-ph_CO |
Constraints on turbulent pressure in the X-ray halos of giant elliptical
galaxies from resonant scattering: The dense cores of X-ray emitting gaseous halos of large elliptical galaxies
with temperatures below about 0.8 keV show two prominent Fe XVII emission
features, which provide a sensitive diagnostic tool to measure the effects of
resonant scattering. We present here high-resolution spectra of five bright
nearby elliptical galaxies, obtained with the Reflection Grating Spectrometers
(RGS) on the XMM-Newton satellite. The spectra for the cores of four of the
galaxies show the Fe XVII line at 15.01 Angstrom being suppressed by resonant
scattering. The data for NGC 4636 in particular allow the effects of resonant
scattering to be studied in detail and to prove that the 15.01 Angstrom line is
suppressed only in the dense core and not in the surrounding regions. Using
deprojected density and temperature profiles for this galaxy obtained with the
Chandra satellite, we model the radial intensity profiles of the strongest
resonance lines, accounting for the effects of resonant scattering, for
different values of the characteristic turbulent velocity. Comparing the model
to the data, we find that the isotropic turbulent velocities on spatial scales
smaller than about 1 kpc are less than 100 km/s and the turbulent pressure
support in the galaxy core is smaller than 5% of the thermal pressure at the
90% confidence level, and less than 20% at 95% confidence. Neglecting the
effects of resonant scattering in spectral fitting of the inner 2 kpc core of
NGC 4636 will lead to underestimates of the chemical abundances of Fe and O by
~10-20%. | astro-ph_CO |
Primordial Non-Gaussianity from G-inflation: Enormous information about interactions is contained in the non-Gaussianities
of the primordial curvature perturbations, which are essential to break the
degeneracy of inflationary models. We study the primordial bispectra for
G-inflation models predicting both sharp and broad peaks in the primordial
scalar power spectrum. We calculate the non-Gaussianity parameter
$f_{\mathrm{NL}}$ in the equilateral limit and squeezed limit numerically, and
confirm that the consistency relation holds in these models. Even though
$f_{\mathrm{NL}}$ becomes large at the scales before the power spectrum reaches
the peak and the scales where there are wiggles in the power spectrum, it
remains to be small at the peak scales. Therefore, the contributions of
non-Gaussianity to the scalar induced secondary gravitational waves and
primordial black hole abundance are expected to be negligible. | astro-ph_CO |
The evolution of the AGN content in groups up to z~1: Determining the AGN content in structures of different mass/velocity
dispersion and comparing them to higher mass/lower redshift analogs is
important to understand how the AGN formation process is related to
environmental properties. We use our well-tested cluster finding algorithm to
identify structures in the GOODS North and South fields, exploiting the
available spectroscopic redshifts and accurate photometric redshifts. We
identify 9 structures in GOODS-south (presented in a previous paper) and 8 new
structures in GOODS-north. We only consider structures where at least 2/3 of
the members brighter than M_R=-20 have a spectroscopic redshift. For those
group members that coincide with X-ray sources in the 4 and 2 Msec Chandra
source catalogs respectively, we determine if the X-ray emission originates
from AGN activity or it is related to the galaxies' star-formation activity. We
find that the fraction of AGN with Log L_H > 42 erg/s in galaxies with M_R <
-20 is on average 6.3+-1.3%, much higher than in lower redshift groups of
similar mass and more than double the fraction found in massive clusters at a
similarly high redshift. We then explore the spatial distribution of AGN in the
structures and find that they preferentially populate the outer regions. The
colors of AGN host galaxies in structures tend to be confined to the green
valley, thus avoiding the blue cloud and, partially, also the red-sequence,
contrary to what happens in the field. We finally compare our results to the
predictions of two sets of semi analytic models to investigate the evolution of
AGN and evaluate potential triggering and fueling mechanisms. The outcome of
this comparison attests the importance of galaxy encounters, not necessarily
leading to mergers, as an efficient AGN triggering mechanism. (abridged) | astro-ph_CO |
A Wide-field High Resolution HI Mosaic of Messier 31: I. Opaque Atomic
Gas and Star Formation Rate Density: We have undertaken a deep, wide-field HI imaging survey of M31, reaching a
maximum resolution of about 50 pc and 2 km/s across a 95x48 kpc region. The HI
mass and brightness sensitivity at 100 pc resolution for a 25 km/s wide
spectral feature is 1500 M_Sun and 0.28 K. Our study reveals ubiquitous HI
self-opacity features, discernible in the first instance as filamentary local
minima in images of the peak HI brightness temperature. Local minima are
organized into complexes of more than kpc length and are particularly
associated with the leading edge of spiral arm features. Just as in the Galaxy,
there is only patchy correspondence of self-opaque features with CO(1-0)
emission. Localized opacity corrections to the column density exceed an order
of magnitude in many cases and add globally to a 30% increase in the atomic gas
mass over that inferred from the integrated brightness under the usual
assumption of negligible self-opacity. Opaque atomic gas first increases from
20 to 60 K in spin temperature with radius to 12 kpc but then declines again to
20 K beyond 25 kpc. We have extended the resolved star formation law down to
physical scales more than an order of magnitude smaller in area and mass than
has been possible previously. The relation between total-gas-mass- and
star-formation-rate-density is significantly tighter than that with
molecular-mass and is fully consistent in both slope and normalization with the
power law index of 1.56 found in the molecule-dominated disk of M51 at 500 pc
resolution. Below a gas-mass-density of about 5 M_Sun/pc^2, there is a
down-turn in star-formation-rate-density which may represent a real local
threshold for massive star formation at a cloud mass of about 5x10^4 M_Sun. | astro-ph_CO |
A note on Low Energy Effective Theory of Chromo Natural Inflation in the
light of BICEP2 results: Recent result of BICEP2, revealing a larger value of tensor to scalar ratio
(r), has opened up new investigations of the in ationary models to fit the
experimental data. The experiment needs to reconfirm the results, specifically
the consistency between Planck and BICEP2. On the other hand, the combined
analysis of Planck and BICEP2 B, including the dust polarization uncertainty,
brings down the upper limit on r. In this note, we reexamine the low energy
effective theory of Chromo Natural In ation model and its generalization in
view of such observational data. We find that the parameter space of the model
admits a large value of r as well as other cosmological observables consistent
with data. | astro-ph_CO |
The impact of the SZ effect on cm-wavelength (1-30 GHz) observation of
galaxy cluster radio relics: (Abridged) Radio relics in galaxy clusters are believed to be associated with
powerful shock fronts that originate during cluster mergers, and are a testbed
for the acceleration of relativistic particles in the intracluster medium.
Recently, radio relic observations have pushed into the cm-wavelength domain
(1-30 GHz) where a break from the standard synchrotron power-law spectrum has
been found, most noticeably in the famous 'Sausage' relic. In this paper, we
point to an important effect that has been ignored or considered insignificant
while interpreting these new high-frequency radio data, namely the
contamination due to the Sunyaev-Zel'dovich (SZ) effect that changes the
observed synchrotron flux. Even though the radio relics reside in the cluster
outskirts, the shock-driven pressure boost increases the SZ signal locally by
roughly an order of magnitude. The resulting flux contamination for some
well-known relics are non-negligible already at 10 GHz, and at 30 GHz the
observed synchrotron fluxes can be diminished by a factor of several from their
true values. Interferometric observations are not immune to this contamination,
since the change in the SZ signal occurs roughly at the same length scale as
the synchrotron emission, although there the flux loss is less severe than
single-dish observations. We present a simple analytical approximation for the
synchrotron-to-SZ flux ratio, based on a theoretical radio relic model that
connects the non-thermal emission to the thermal gas properties, and show that
by measuring this ratio one can potentially estimate the relic magnetic fields
or the particle acceleration efficiency. | astro-ph_CO |
A high-resolution self-consistent whole sky foreground model: The neutral hydrogen 21cm line is potentially a very powerful probe of the
observable universe, and a number of on-going experiments are trying to detect
it at cosmological distances. However, the presence of strong foreground
radiations such as the galactic synchrotron radiation, galactic free-free
emission and extragalactic radio sources make it a very challenging task. For
the design of 21cm experiments and analysis of their data, simulation is an
essential tool, and good sky foreground model is needed. With existing data the
whole sky maps are available only in low angular resolutions or for limited
patches of sky, which is inadequate in the simulation of these new 21cm
experiments. In this paper, we present the method of constructing a high
resolution self-consistent sky model at low frequencies, which incorporates
both diffuse foreground and point sources. Our diffuse map is constructed by
generating physical foreground components including the galactic synchrotron
emission and galactic free-free emission. The point source sample is generated
using the actual data from the NRAO VLA Sky Survey (NVSS) and the Sydney
University Molonglo Sky Survey (SUMSS) where they are available and complete in
flux limit, and mock point sources according to statistical distributions. The
entire model is made self-consistent by removing the integrated flux of the
point sources from the diffuse map so that this part of radiation is not double
counted. We show that with the point sources added, a significant angular power
is introduced in the mock sky map, which may be important for foreground
subtraction simulations. Our sky maps and point source catalogues are available
to download. | astro-ph_CO |
The Sloan Great Wall. Rich clusters: We present the results of the study of the substructure and galaxy content of
ten rich clusters of galaxies in three different superclusters of the Sloan
Great Wall. We determine the substructure in clusters using the 'Mclust'
package from the 'R' statistical environment and analyse their galaxy content.
We analyse the distribution of the peculiar velocities of galaxies in clusters
and calculate the peculiar velocity of the first ranked galaxy. We show that
clusters in our sample have more than one component; in some clusters different
components also have different galaxy content. We find that in some clusters
with substructure the peculiar velocities of the first ranked galaxies are
large. All clusters in our sample host luminous red galaxies. They can be found
both in the central areas of clusters as well as in the outskirts, some of them
have large peculiar velocities. About 1/3 of red galaxies in clusters are
spirals. The scatter of colours of red ellipticals is in most clusters larger
than that of red spirals. The presence of substructure in rich clusters, signs
of possible mergers and infall, as well as the large peculiar velocities of the
first ranked galaxies suggest that the clusters in our sample are not yet
virialized. We present merger trees of dark matter haloes in an N-body
simulation to demonstrate the formation of present-day dark matter haloes via
multiple mergers during their evolution. In simulated dark matter haloes we
find a substructure similar to that in observed clusters. | astro-ph_CO |
Ghost Collapse : exploring feasibility of spurious Spherical Collapses: We explore the real solutions to the Spherical Collapse Model in a non-flat
Universe with a Cosmological Constant, and observe a possible situation for a
fake or Ghost Collapse, in which an expanding overdense spherical region, turns
around and begins to collapse, turns around again after a finite time and
starts expanding. To make such a situation of spurious collapse feasible, we
make a linear redshift dependent correction to the standard Dark Energy density
term which is originally in the form of a cosmological constant. There is good
reason to believe in such a correction based on recent research which hints
that Dark Energy desnity evolves with the redshift (even becomes negative) when
fit to observational data. | astro-ph_CO |
Observational signatures of microlensing in gravitational waves at
LIGO/Virgo frequencies: Microlenses with typical stellar masses (a few ${\rm M}_{\odot}$) have
traditionally been disregarded as potential sources of gravitational lensing
effects at LIGO/Virgo frequencies, since the time delays are often much smaller
than the inverse of the frequencies probed by LIGO/Virgo, resulting in
negligible interference effects at LIGO/Virgo frequencies. While this is true
for isolated microlenses in this mass regime, we show how, under certain
circumstances and for realistic scenarios, a population of microlenses (for
instance stars and remnants from a galaxy halo or from the intracluster medium)
embedded in a macromodel potential (galaxy or cluster) can conspire together to
produce time delays of order one millisecond which would produce significant
interference distortions in the observed strains. At sufficiently large
magnification factors (of several hundred), microlensing effects should be
common in gravitationally lensed gravitational waves. We explore the regime
where the predicted signal falls in the frequency range probed by LIGO/Virgo.
We find that stellar mass microlenses, permeating the lens plane, and near
critical curves, can introduce interference distortions in strongly lensed
gravitational waves. For those lensed events with negative parity, (or saddle
points, never studied before in the context of gravitational waves), and that
take place near caustics of macromodels, they are more likely to produce
measurable interference effects at LIGO/Virgo frequencies. This is the first
study that explores the effect of a realistic population of microlenses, plus a
macromodel, on strongly lensed gravitational waves. | astro-ph_CO |
Beyond Concordance Cosmology with Magnification of Gravitational-Wave
Standard Sirens: We show how future gravitational-wave detectors would be able of
discriminating between the concordance LCDM cosmological model and up-to-date
competing alternatives, e.g. dynamical dark energy models (DE) or modified
gravity theories (MG). Our method consists in using the weak-lensing
magnification effect that affects a standard-siren signal because of its
travelling trough the Universe's large-scale structure. As a demonstration, we
present constraints on DE and MG from proposed gravitational-wave detectors,
namely ET and DECIGO/BBO. | astro-ph_CO |
The deconvolved distribution estimator: enhancing reionisation-era CO
line-intensity mapping analyses with a cross-correlation analogue for
one-point statistics: We present the deconvolved distribution estimator (DDE), an extension of the
voxel intensity distribution (VID), in the context of future observations
proposed as part of the CO Mapping Array Project (COMAP). The DDE exploits the
fact that the observed VID is a convolution of correlated signal intensity
distributions and uncorrelated noise or interloper intensity distributions. By
deconvolving the individual VID of two observables away from their joint VID in
a Fourier-space operation, the DDE suppresses sensitivity to interloper
emission while maintaining sensitivity to correlated components. The DDE thus
improves upon the VID by reducing the relative influence of uncorrelated noise
and interloper biases, which is useful in the context of COMAP observations
that observe different rotational transitions of CO from the same comoving
volume in different observing frequency bands. Fisher forecasts suggest that
the theoretical sensitivity in the DDE allows significant improvements in
constraining power compared to either the cross power spectrum or the
individual VID data, and matches the constraining power of the combination of
all other one- and two-point summary statistics. Future work should further
investigate the covariance and model-dependent behaviour of this novel
one-point cross-correlation statistic. | astro-ph_CO |
The Physics and Mass Assembly of distant galaxies with the E-ELT: One of the main science goal of the future European Extremely Large Telescope
will be to understand the mass assembly process in galaxies as a function of
cosmic time. To this aim, a multi-object, AO-assisted integral field
spectrograph will be required to map the physical and chemical properties of
very distant galaxies. In this paper, we examine the ability of such an
instrument to obtain spatially resolved spectroscopy of a large sample of
massive (0.1<Mstellar<5e11Mo) galaxies at 2<z<6, selected from future large
area optical-near IR surveys. We produced a set of about one thousand numerical
simulations of 3D observations using reasonable assumptions about the site,
telescope, and instrument, and about the physics of distant galaxies. These
data-cubes were analysed as real data to produce realistic kinematic
measurements of very distant galaxies. We then studied how sensible the
scientific goals are to the observational (i.e., site-, telescope-, and
instrument-related) and physical (i.e., galaxy-related) parameters. We
specifically investigated the impact of AO performance on the science goal. We
did not identify any breaking points with respect to the parameters (e.g., the
telescope diameter), with the exception of the telescope thermal background,
which strongly limits the performance in the highest (z>5) redshift bin. We
find that a survey of Ngal galaxies that fulfil the range of science goals can
be achieved with a ~90 nights program on the E-ELT, provided a multiplex
capability M Ngal/8. | astro-ph_CO |
Exploring the Impact of Microlensing on Gravitational Wave Signals:
Biases, Population Characteristics, and Prospects for Detection: In this study, we investigate the impact of microlensing on gravitational
wave (GW) signals in the LIGO$-$Virgo sensitivity band. Microlensing caused by
an isolated point lens, with (redshifted) mass ranging from
$M_\mathrm{Lz}\in(1,10^5){\rm M}_\odot$ and impact parameter $y\in (0.01,~5)$,
can result in a maximum mismatch of $\sim 30\%$ with their unlensed
counterparts. When $y<1$, it strongly anti-correlates with the luminosity
distance enhancing the detection horizon and signal-to-noise ratio (SNR).
Biases in inferred source parameters are assessed, with in-plane spin
components being the most affected intrinsic parameters. The luminosity
distance is often underestimated, while sky-localisation and trigger times are
mostly well-recovered. Study of a population of microlensed signals due to an
isolated point lens primarily reveals: (i) using unlensed templates during the
search causes fractional loss ($20\%$ to $30\%$) of potentially identifiable
microlensed signals; (ii) the observed distribution of $y$ challenges the
notion of its high improbability at low values ($y\lesssim 1$), especially for
$y\lesssim 0.1$; (iii) Bayes factor analysis of the population indicates that
certain region in $M_\mathrm{Lz}-y$ parameter space have a higher probability
of being detected and accurately identified as microlensed. Notably, the
microlens parameters for the most compelling candidate identified in previous
microlensing searches, GW200208_130117, fall within a 1-sigma range of the
aforementioned higher probability region. Identifying microlensing signatures
from $M_\mathrm{Lz}<100~$M$_\odot$ remains challenging due to small
microlensing effects at typical SNR values. Additionally, we also examined how
microlensing from a population of microlenses influences the detection of
strong lensing signatures in pairs of GW events, particularly in the
posterior-overlap analysis. | astro-ph_CO |
Can varying the gravitational constant alleviate the tensions ?: Constraints on the cosmological concordance model parameters from observables
at different redshifts are usually obtained using the locally measured value of
the gravitational constant $G_N$. Here we relax this assumption, by considering
$G$ as a free parameter, either constant over the redshift range or dynamical
but limited to differ from fiducial value only above a certain redshift. Using
CMB data and distance measurements from galaxy clustering BAO feature, we
constrain the cosmological parameters, along with $G$, through a MCMC bayesian
inference method. Furthermore, we investigate whether the tensions on the
matter fluctuation $\sigma_8$ and Hubble $H_0$ parameter could be alleviated by
this new variable. We used different parameterisations spanning from a constant
$G$ to a dynamical $G$. In all the cases investigated in this work we found no
mechanism that alleviates the tensions when both CMB and BAO data are used with
$\xi_{\mathrm{g}} = G / G_N$ constrained to 1.0$\pm0.04$ (resp. $\pm0.01$) in
the constant (resp. dynamical) case. Finally, we studied the cosmological
consequences of allowing a running of the spectral index, since the later is
sensitive to a change in $G$. For the two parameterisations adopted, we found
no significant changes to the previous conclusions. | astro-ph_CO |
Quasi-periodical features in the distribution of Luminous Red Galaxies: A statistical analysis of radial distributions of Luminous Red Galaxies
(LRGs) from the Sloan Digital Sky Survey (SDSS DR7) catalogue within an
interval $0.16 \leq z \leq 0.47$ is carried out. We found that the radial
distribution of $\sim$ 106,000 LRGs incorporates a few quasi-periodical
components relatively to a variable $\eta$, dimensionless line-of-sight
comoving distance calculated for the $\Lambda$CDM cosmological model. The most
significant peaks of the power spectra are obtained for two close periodicities
corresponding to the spatial comoving scales $(135 \pm 12) h^{-1}$ Mpc and
$(101 \pm 6)h^{-1}$ Mpc. The latter one is dominant and consistent with the
characteristic scale of the baryon acoustic oscillations. We analyse also the
radial distributions of two other selected LRG samples: $\sim$ 33,400 bright
LRGs ($-23.2 < M \leq -21.8$) and $\sim$ 60,300 all LRGs within a rectangle
region on the sky, and show differences of the quasi-periodical features
characteristic for different samples. Being confirmed the results would allow
to give preference of the spatial against temporal models which could explain
the quasi-periodicities discussed here. As a caveat we show that estimations of
the significance levels of the peaks strongly depend on a smoothed radial
function (trend) as well as characteristics of random fluctuations. | astro-ph_CO |
Full covariance of CMB and lensing reconstruction power spectra: CMB and lensing reconstruction power spectra are powerful probes of
cosmology. However they are correlated, since the CMB power spectra are lensed
and the lensing reconstruction is constructed using CMB multipoles. We perform
a full analysis of the auto- and cross-covariances, including polarization
power spectra and minimum variance lensing estimators, and compare with
simulations of idealized future CMB-S4 observations. Covariances sourced by
fluctuations in the unlensed CMB and instrumental noise can largely be removed
by using a realization-dependent subtraction of lensing reconstruction noise,
leaving a relatively simple covariance model that is dominated by
lensing-induced terms and well described by a small number of principal
components. The correlations between the CMB and lensing power spectra will be
detectable at the level of $\sim 5\sigma$ for a CMB-S4 mission, and neglecting
those could underestimate some parameter error bars by several tens of percent.
However we found that the inclusion of external priors or data sets to estimate
parameter error bars can make the impact of the correlations almost negligible. | astro-ph_CO |
A robust upper limit on N_eff from BBN, circa 2011: We derive here a robust bound on the effective number of neutrinos from
constraints on primordial nucleosynthesis yields of deuterium and helium. In
particular, our results are based on very weak assumptions on the astrophysical
determination of the helium abundance, namely that the minimum effect of
stellar processing is to keep constant (rather than increase, as expected) the
helium content of a low-metallicity gas. Using the results of a recent analysis
of extragalactic HII regions as upper limit, we find that Delta Neff<= 1 at 95
% C.L., quite independently of measurements on the baryon density from cosmic
microwave background anisotropy data and of the neutron lifetime input. In our
approach, we also find that primordial nucleosynthesis alone has no significant
preference for an effective number of neutrinos larger than the standard value.
The ~2 sigma hint sometimes reported in the literature is thus driven by CMB
data alone and/or is the result of a questionable regression protocol to infer
a measurement of primordial helium abundance. | astro-ph_CO |
Modification of the halo mass function by kurtosis associated with
primordial non-Gaussianity: We study the halo mass function in the presence of the kurtosis type of
primordial non-Gaussianity. The kurtosis corresponds to the trispectrum as
defined in Fourier space. The primordial trispectrum is commonly characterized
by two parameters, $\tau_{\rm NL}$ and $g_{\rm NL}$. As applications of the
derived non-Gaussian mass function, we consider the effect on the abundance of
void structure, the effect on early star formation and on formation of the most
massive object at high redshift. We show that by comparing the effects of
primordial non-Gaussianity on cluster abundance with that on void abundance, we
can distinguish between the skewness and the kurtosis types of primordial
non-Gaussianity. As for early star formation, we show that the kurtosis type of
primordial non-Gaussianity seems not to affect the reionization history of the
Universe on average. However, at high redshifts (up to $z\simeq 20$) such
non-Gaussianity does somewhat affect the early stages of reionization. | astro-ph_CO |
Dusty MgII Absorbers: Implications for the GRB/Quasar Incidence
Discrepancy: There is nearly a factor of four difference in the number density of
intervening MgII absorbers as determined from gamma-ray burst (GRB) and quasar
lines of sight. We use a Monte-Carlo simulation to test if a dust extinction
bias can account for this discrepancy. We apply an empirically determined
relationship between dust column density and MgII rest equivalent width to
simulated quasar sight-lines and model the underlying number of quasars that
must be present to explain the published magnitude distribution of SDSS
quasars. We find that an input MgII number density dn/dz of 0.273 +- 0.002 over
the range 0.4 <= z <= 2.0 and with MgII equivalent width W_0 >= 1.0 angstroms
accurately reproduces observed distributions. From this value, we conclude that
a dust obstruction bias cannot be the sole cause of the observed discrepancy
between GRB and quasar sight-lines: this bias is likely to reduce the
discrepancy only by ~10%. | astro-ph_CO |
Primordial power spectrum: a complete analysis with the WMAP nine-year
data: We have improved further the error sensitive Richardson-Lucy deconvolution
algorithm making it applicable directly on the un-binned measured angular power
spectrum of Cosmic Microwave Background observations to reconstruct the form of
the primordial power spectrum. This improvement makes the application of the
method significantly more straight forward by removing some intermediate stages
of analysis allowing a reconstruction of the primordial spectrum with higher
efficiency and precision and with lower computational expenses. Applying the
modified algorithm we fit the WMAP 9 year data using the optimized
reconstructed form of the primordial spectrum with more than 300 improvement in
\chi^2 with respect to the best fit power-law. This is clearly beyond the reach
of other alternative approaches and reflects the efficiency of the proposed
method in the reconstruction process and allow us to look for any possible
feature in the primordial spectrum projected in the CMB data. Though the
proposed method allow us to look at various possibilities for the form of the
primordial spectrum, all having good fit to the data, proper error-analysis is
needed to test for consistency of theoretical models since, along with possible
physical artefacts, most of the features in the reconstructed spectrum might be
arising from fitting noises in the CMB data. Reconstructed error-band for the
form of the primordial spectrum using many realizations of the data, all
bootstrapped and based on WMAP 9 year data, shows proper consistency of
power-law form of the primordial spectrum with the WMAP 9 data at all wave
numbers. Including WMAP polarization data in to the analysis have not improved
much our results due to its low quality but we expect Planck data will allow us
to make a full analysis on CMB observations on both temperature and
polarization separately and in combination. | astro-ph_CO |
Fantasia of a Superfluid Universe -- In memory of Kerson Huang: This article introduces Kerson Huang's theory on superfluid universe in these
aspects: I. choose the asymptotically free Halpern-Huang scalar field(s) to
drive inflation; II. use quantum turbulence to create matter; III. consider
dark energy as the energy density of the cosmic superfluid and dark matter the
deviation of the superfluid density from its equilibrium value; IV. use quantum
vorticity to explain phenomena such as the non-thermal filaments at the
galactic center, the large voids in the galactic distribution, and the
gravitational collapse of stars to fast-rotating blackholes. | astro-ph_CO |
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