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The $m$-$z$ relation for Type Ia supernovae: safety in numbers or safely
without worry?: The $m$-$z$ relation for Type Ia supernovae is compatible with the
cosmological concordance model if one assumes that the Universe is homogeneous,
at least with respect to light propagation. This could be due to the density
along each line of sight being equal to the overall cosmological density, or to
`safety in numbers', with variation in the density along all lines of sight
averaging out if the sample is large enough. Statistical correlations (or lack
thereof) between redshifts, residuals (differences between the observed
distance moduli and those calculated from the best-fitting cosmological model),
and observational uncertainties suggest that the former scenario is the better
description, so that one can use the traditional formula for the luminosity
distance safely without worry. | Adiabaticity and the Fate of Non-Gaussianities: The Trispectrum and
Beyond: Extending the analysis of [1011.4934] beyond the bispectrum, we explore the
superhorizon generation of local non-gaussianities and their subsequent
approach to adiabaticity. Working with a class of two field models of inflation
with potentials amenable to treatment with the delta N formalism we find that,
as is the case for f_{NL}^{local}, the local trispectrum parameters tau_{NL}
and g_{NL} are exponentially driven toward values which are slow roll
suppressed if the fluctuations are driven into an adiabatic mode by a phase of
effectively single field inflation. We argue that general considerations should
ensure that a similar behavior will hold for the local forms of higher point
correlations as well. |
Highly Variable Objects in the Palomar-QUEST Survey: A Blazar Search
using Optical Variability: We identify 3,113 highly variable objects in 7,200 square degrees of the
Palomar-QUEST Survey, which each varied by more than 0.4 magnitudes
simultaneously in two broadband optical filters on timescales from hours to
roughly 3.5 years. The primary goal of the selection is to find blazars by
their well-known violent optical variability. Because most known blazars have
been found in radio and/or X-ray wavelengths, a sample discovered through
optical variability may have very different selection effects, elucidating the
range of behavior possible in these systems. A set of blazars selected in this
unusual manner will improve our understanding of the physics behind this
extremely variable and diverse class of AGN. The object positions, variability
statistics, and color information are available using the Palomar-QUEST CasJobs
server. The time domain is just beginning to be explored over large sky areas;
we do not know exactly what a violently variable sample will hold. About 20% of
the sample has been classified in the literature; over 70% of those objects are
known or likely AGN. The remainder largely consists of a variety of variable
stars, including a number of RR Lyrae and cataclysmic variables. | The Rapid Decline in Metallicity of Damped Ly-alpha Systems at z~5: We present evidence that the cosmological mean metallicity of neutral atomic
hydrogen gas shows a sudden decrease at z>4.7 down to <Z>=-2.03(+0.09-0.11),
which is 6 sigma deviant from that predicted by a linear fit to the data at
lower redshifts. This measurement is made possible by the chemical abundance
measurements of 8 new damped Ly-alpha (DLA) systems at z>4.7 observed with the
Echellette Spectrograph and Imager on the Keck II telescope, doubling the
number of measurements at z>4.7 to 16. Possible explanations for this sudden
decrease in metallicity include a change in the physical processes that enrich
the neutral gas within disks, or an increase of the covering factor of neutral
gas outside disks due to a lower ultra-violet radiation field and higher
density at high redshift. The later possibility would result in a new
population of presumably lower metallicity DLAs, with an increased contribution
to the DLA population at higher redshifts resulting in a reduced mean
metallicity. Furthermore, we provide evidence of a possible decrease at z>4.7
in the comoving metal mass density of DLAs, which is flat out to z~4.3. Such a
decrease is expected, as otherwise most of the metals from star-forming
galaxies would reside in DLAs by z~6. While the metallicity is decreasing at
high redshift, the contribution of DLAs to the total metal budget of the
universe increases with redshift, with DLAs at z~4.3 accounting for ~20% as
many metals as produced by Lyman break galaxies. |
Studying the properties of galaxy cluster morphology estimators: X-ray observations of galaxy clusters reveal a large range of morphologies
with various degrees of disturbance, showing that the assumptions of
hydrostatic equilibrium and spherical shape which are used to determine the
cluster mass from X-ray data are not always satisfied. It is therefore
important for the understanding of cluster properties as well as for
cosmological applications to detect and quantify substructure in X-ray images
of galaxy clusters. Two promising methods to do so are power ratios and center
shifts. Since these estimators can be heavily affected by Poisson noise and
X-ray background, we performed an extensive analysis of their statistical
properties using a large sample of simulated X-ray observations of clusters
from hydrodynamical simulations. We quantify the measurement bias and error in
detail and give ranges where morphological analysis is feasible. A new,
computationally fast method to correct for the Poisson bias and the X-ray
background contribution in power ratio and center shift measurements is
presented and tested for typical XMM-Newton observational data sets. We studied
the morphology of 121 simulated cluster images and establish structure
boundaries to divide samples into relaxed, mildly disturbed and disturbed
clusters. In addition, we present a new morphology estimator - the peak of the
0.3-1 r500 P3/P0 profile to better identify merging clusters. The analysis
methods were applied to a sample of 80 galaxy clusters observed with
XMM-Newton. We give structure parameters (P3/P0 in r500, w and P3/P0_max) for
all 80 observed clusters. Using our definition of the P3/P0 (w) substructure
boundary, we find 41% (47%) of our observed clusters to be disturbed. | LBT/LUCIFER Observations of the z~2 Lensed Galaxy J0900+2234: We present rest-frame optical images and spectra of the gravitationally
lensed, star-forming galaxy J0900+2234 (z=2.03). The observations were
performed with the newly commissioned LUCIFER1 near-infrared instrument mounted
on the Large Binocular Telescope (LBT). We fit lens models to the rest-frame
optical images and find the galaxy has an intrinsic effective radius of 7.4 kpc
with a lens magnification factor of about 5 for the A and B components. We also
discovered a new arc belonging to another lensed high-z source galaxy, which
makes this lens system a potential double Einstein ring system. Using the high
S/N rest-frame optical spectra covering H+K band, we detected Hbeta, OIII,
Halpha, NII and SII emission lines. Detailed physical properties of this high-z
galaxy were derived. The extinction towards the ionized HII regions (E_g(B-V))
is computed from the flux ratio of Halpha and Hbeta and appears to be much
higher than that towards stellar continuum (E_s(B-V)), derived from the optical
and NIR broad band photometry fitting. The metallicity was estimated using N2
and O3N2 indices. It is in the range of 1/5-1/3 solar abundance, which is much
lower than the typical z~2 star-forming galaxies. From the flux ratio of SII
6717 and 6732, we found that the electron number density of the HII regions in
the high-z galaxy were >1000 cm^-3, consistent with other z~2 galaxies but much
higher than that in local HII regions. The star-formation rate was estimated
via the Halpha luminosity, after correction for the lens magnification, to be
about 365\pm69 Msun/yr. Combining the FWHM of Halpha emission lines and the
half-light radius, we found the dynamical mass of the lensed galaxy is
5.8\pm0.9x10^10 Msun. The gas mass is 5.1\pm1.1x10^10~Msun from the H\alpha
flux surface density by using global Kennicutt-Schmidt Law, indicating a very
high gas fraction of 0.79\pm0.19 in J0900+2234. |
Neutrino Masses, Scale-Dependent Growth, and Redshift-Space Distortions: Massive neutrinos leave a unique signature in the large scale clustering of
matter. We investigate the wavenumber dependence of the growth factor arising
from neutrino masses and use a Fisher analysis to determine the aspects of a
galaxy survey needed to measure this scale dependence. | Linear growth of matter density perturbations in f(R,G) theories: We derive the equation of matter density perturbations on sub-horizon scales
around a flat Friedmann-Lema\^\i tre-Robertson-Walker background for the
general Lagrangian density $f(R,\GB)$ that is a function of a Ricci scalar $R$
and a Gauss-Bonnet term $\GB$. We find that the effective gravitational
constant generically scales as distance squared at small distances. The effect
of this diminishing of the gravitational constant might be important in the
gravitational dynamics of cosmic objects such as galaxies, which can be in
principle tested by observations. We also provide the general expressions for
the effective anisotropic stress, which is useful to constrain modified gravity
models from observations of large-scale structure and weak lensing. We also
find that there is a special class of theories which evade this unusual
behaviour and that the condition to belong to this special class is exactly the
same as the one for not having super-luminal modes with propagation speed
proportional to their wavenumber. |
A gravitational-wave limit on the Chandrasekhar mass of dark matter: We explore a new paradigm to study dissipative dark matter models using
gravitational-wave observations. We consider a dark atomic model which predicts
the formation of binary black holes such as GW190425 while obeying constraints
from large-scale structure, and improving on the missing satellite problem.
Using LIGO and Virgo gravitational-wave data from 12th September 2015 to 1st
October 2019, we show that interpreting GW190425 as a dark matter black-hole
binary limits the Chandrasekhar mass for dark matter to be below 1.4 $M_\odot$
at $> 99.9\%$ confidence implying that the dark proton is heavier than 0.95
GeV, while also suggesting that the molecular energy-level spacing of dark
molecules lies near $10^{-3}$ eV and constraining the cooling rate of dark
matter at low temperatures. | Inferences on the Timeline of Reionization at z~8 From the KMOS
Lens-Amplified Spectroscopic Survey: Detections and non-detections of Lyman alpha (Ly$\alpha$) emission from $z>6$
galaxies ($<1$ Gyr after the Big Bang) can be used to measure the timeline of
cosmic reionization. Of key interest to measuring reionization's mid-stages,
but also increasing observational challenge, are observations at z > 7, where
Ly$\alpha$ redshifts to near infra-red wavelengths. Here we present a search
for z > 7.2 Ly$\alpha$ emission in 53 intrinsically faint Lyman Break Galaxy
candidates, gravitationally lensed by massive galaxy clusters, in the KMOS
Lens-Amplified Spectroscopic Survey (KLASS). With integration times of ~7-10
hours, we detect no Ly$\alpha$ emission with S/N>5 in our sample. We determine
our observations to be 80% complete for 5$\sigma$ spatially and spectrally
unresolved emission lines with integrated line flux $>5.7\times10^{-18}$ erg
s$^{-1}$ cm$^{-2}$. We define a photometrically selected sub-sample of 29
targets at $z=7.9\pm0.6$, with a median 5$\sigma$ Ly$\alpha$ EW limit of 58A.
We perform a Bayesian inference of the average intergalactic medium (IGM)
neutral hydrogen fraction using their spectra. Our inference accounts for the
wavelength sensitivity and incomplete redshift coverage of our observations,
and the photometric redshift probability distribution of each target. These
observations, combined with samples from the literature, enable us to place a
lower limit on the average IGM neutral hydrogen fraction of $> 0.76 \; (68\%),
\; > 0.46 \; (95\%)$ at z ~ 8, providing further evidence of rapid reionization
at z~6-8. We show that this is consistent with reionization history models
extending the galaxy luminosity function to $M_\textrm{UV} \lesssim -12$, with
low ionizing photon escape fractions, $f_\textrm{esc} \lesssim 15\%$. |
A Comparison and Joint Analysis of Sunyaev-Zel'dovich Effect
Measurements from Planck and Bolocam for a set of 47 Massive Galaxy Clusters: We measure the SZ signal toward a set of 47 clusters with a median mass of
$9.5 \times 10^{14}$ M$_{\odot}$ and a median redshift of 0.40 using data from
Planck and the ground-based Bolocam receiver. When Planck XMM-like masses are
used to set the scale radius $\theta_{\textrm{s}}$, we find consistency between
the integrated SZ signal, $Y_{\textrm{5R500}}$, derived from Bolocam and Planck
based on gNFW model fits using A10 shape parameters, with an average ratio of
$1.069 \pm 0.030$ (allowing for the $\simeq 5$% Bolocam flux calibration
uncertainty). We also perform a joint fit to the Bolocam and Planck data using
a modified A10 model with the outer logarithmic slope $\beta$ allowed to vary,
finding $\beta = 6.13 \pm 0.16 \pm 0.76$ (measurement error followed by
intrinsic scatter). In addition, we find that the value of $\beta$ scales with
mass and redshift according to $\beta \propto M^{0.077 \pm 0.026} \times
(1+z)^{-0.06 \pm 0.09}$. This mass scaling is in good agreement with recent
simulations. We do not observe the strong trend of $\beta$ with redshift seen
in simulations, though we conclude that this is most likely due to our sample
selection. Finally, we use Bolocam measurements of $Y_{500}$ to test the
accuracy of the Planck completeness estimate. We find consistency, with the
actual number of Planck detections falling approximately $1 \sigma$ below the
expectation from Bolocam. We translate this small difference into a constraint
on the the effective mass bias for the Planck cluster cosmology results, with
$(1-b) = 0.93 \pm 0.06$. | Future dynamics in f(R) theories: The $f(R)$ gravity theories provide an alternative way to explain the current
cosmic acceleration without invoking dark energy matter component. However, the
freedom in the choice of the functional forms of $f(R)$ gives rise to the
problem of how to constrain and break the degeneracy among these gravity
theories on theoretical and/or observational grounds. In this paper to proceed
further with the investigation on the potentialities, difficulties and
limitations of $f(R)$ gravity, we examine the question as to whether the future
dynamics can be used to break the degeneracy between $f(R)$ gravity theories by
investigating the future dynamics of spatially homogeneous and isotropic dust
flat models in two $f(R)$ gravity theories, namely the well known $f(R) = R +
\alpha R^{n}$ gravity and another by A. Aviles et al., whose motivation comes
from the cosmographic approach to $f(R)$ gravity. To this end we perform a
detailed numerical study of the future dynamic of these flat model in these
theories taking into account the recent constraints on the cosmological
parameters made by the Planck team. We show that besides being powerful for
discriminating between $f(R)$ gravity theories, the future dynamics technique
can also be used to determine the fate of the Universe in the framework of
these $f(R)$ gravity theories. Moreover, there emerges from our numerical
analysis that if we do not invoke a dark energy component with
equation-of-state parameter $\omega < -1$ one still has dust flat FLRW solution
with a big rip, if gravity deviates from general relativity via $f(R) = R +
\alpha R^n $. We also show that FLRW dust solutions with $f''<0$ do not
necessarily lead to singularity. |
Measuring the Integrated Sachs-Wolfe Effect: One of the main challenges of modern cosmology is to understand the nature of
dark energy. The Integrated Sachs-Wolfe (ISW) effect is sensitive to dark
energy and presents an independent signature of dark energy in the absence of
modified gravity and curvature. The ISW effect occurs on large scales, where
cosmic variance is high and where there are large amounts of missing data in
the CMB and large scale structure maps due to Galactic confusion. Moreover,
existing methods in the literature often make strong assumptions about the
statistics of the underlying fields or estimators. Together these effects can
severely limit signal extraction. We review literature on the ISW effect,
comparing statistical subtleties between existing methods, and identifying
several limitations. We propose a novel method to detect and measure the ISW
signal. This method assumes only that the primordial CMB field is Gaussian. It
is based on a sparse inpainting method to reconstruct missing data and uses a
bootstrap technique to avoid assumptions about the statistics of the estimator.
It is a complete method, using three complementary statistical methods. We
apply our method to Euclid-like simulations and show we can expect a \sim
7\sigma model-independent detection of the ISW signal with WMAP7-like data,
even with missing data. Other tests return \sim 4.7\sigma detection levels for
a Euclid-like survey, with levels independent from whether the galaxy field is
normally or lognormally distributed. We apply our method to the 2 Micron All
Sky Survey (2MASS) and WMAP7 CMB data and find detections in the 1.1 -
2.0\sigma range, as expected from simulations. As a by-product, we reconstruct
the full-sky temperature ISW field due to 2MASS data. We have presented a novel
technique, based on sparse inpainting and bootstrapping, which accurately
detects and reconstructs the ISW effect. | The NEWFIRM Medium-band Survey: Photometric Catalogs, Redshifts and the
Bimodal Color Distribution of Galaxies out to z~3: We present deep near-infrared (NIR) medium-bandwidth photometry over the
wavelength range 1-1.8 microns in the All-wavelength Extended Groth strip
International Survey (AEGIS) and Cosmic Evolution Survey (COSMOS) fields. The
observations were carried out as part of the NEWFIRM Medium-Band Survey (NMBS),
an NOAO survey program on the Mayall 4m telescope on Kitt Peak using the NOAO
Extremely Wide-Field Infrared Imager (NEWFIRM). In this paper, we describe the
full details of the observations, data reduction and photometry for the survey.
We also present a public K-selected photometric catalog, along with accurate
photometric redshifts. The redshifts are computed with 37 (20) filters in the
COSMOS (AEGIS) fields, combining the NIR medium-bandwidth data with existing
ultraviolet (UV; Galaxy Evolution Explorer), visible and NIR
(Canada-France-Hawaii Telescope and Subaru) and mid-IR (Spitzer/IRAC) imaging.
We find excellent agreement with publicly available spectroscopic redshifts,
with sigma_z/(1+z)~1-2% for ~4000 galaxies at z=0-3. The NMBS catalogs contain
~13,000 galaxies at z>1.5 with accurate photometric redshifts and rest-frame
colors. Due to the increased spectral resolution obtained with the five NIR
medium-band filters, the median 68% confidence intervals of the photometric
redshifts of both quiescent and star-forming galaxies are a factor of ~2 times
smaller when comparing catalogs with medium-band NIR photometry to NIR
broadband photometry. We show evidence for a clear bimodal color distribution
between quiescent and star-forming galaxies that persists to z~3, a higher
redshift than has been probed so far. |
The Star-Formation Histories of z~2 DOGs and SMGs: The Spitzer Space Telescope has identified a population of ultra-luminous
infrared galaxies (ULIRGs) at z ~ 2 that may play an important role in the
evolution of massive galaxies. We measure the stellar masses of two populations
of Spitzer-selected ULIRGs, both of which have extremely red R-[24] colors
(dust-obscured galaxies, or DOGs) and compare our results with sub-millimeter
selected galaxies (SMGs). One set of 39 DOGs has a local maximum in their
mid-IR spectral energy distribution (SED) at rest-frame 1.6um associated with
stellar emission ("bump DOGs"), while the other set of 51 DOGs has a power-law
dominated mid-IR SED with spectral features typical of obscured AGN ("power-law
DOGs"). We use stellar population synthesis models applied self-consistently to
broad-band photometry in the rest-frame ultra-violet, optical, and
near-infrared of each of these populations and test a variety of stellar
population synthesis codes, star-formation histories (SFHs), and initial mass
functions (IMFs). Assuming a simple stellar population SFH and a Chabrier IMF,
we find that the median and inner quartile stellar masses of SMGs, bump DOGs
and power-law DOGs are given by log(M_*/M_sun) = 10.42_-0.36^+0.42,
10.62_-0.32^+0.36, and 10.71_-0.34^+0.40, respectively. Implementing more
complicated SFHs with multiple age components increases these mass estimates by
up to 0.5 dex. Our stellar mass estimates are consistent with physical
mechanisms for the origin of z~2 ULIRGs that result in high star-formation
rates for a given stellar mass. Such mechanisms are usually driven by a major
merger of two gas-rich systems, rather than smooth accretion of gas and small
satellites. | On validity of the quasi-static approximation in scalar-tensor theories: The discovery of cosmic acceleration motivated extensive studies of dynamical
dark energy and modified gravity models. Of particular interest are the
scalar-tensor theories, with a scalar field dark energy non-minimally coupled
to matter. Cosmological constraints on these models often employ the
quasi-static approximation (QSA), in which the dynamics of the scalar field
perturbations is proportional to the perturbation in the matter density. Using
the QSA simplifies the physical interpretation of the phenomenology of
scalar-tensor theories, and results in substantial savings of computing time
when deriving parameter constraints. Focusing on the symmetron model, which is
a well-motivated scalar-tensor theory with a screening mechanism, we compare
the exact solution of the linearly perturbed field equations to those obtained
under the QSA and identify the range of the model parameters for which the QSA
is valid. We find that the evolution of background scalar field is most
important, namely, whether it is dominated by the Hubble friction or the scalar
field potential. This helps us derive a criterion for the symmetron model, but
same argument can be applied to other scalar-tensor theories of generalized
Brans-Dicke type. We consider two scenarios, one where the scalar field is only
coupled to dark matter and where it couples to all of the matter. |
Fast simulations of cosmic large-scale structure with massive neutrinos: Accurate cosmological simulations that include the effect of non-linear
matter clustering as well as of massive neutrinos are essential for measuring
the neutrino mass scale from upcoming galaxy surveys. Typically, Newtonian
simulations are employed and the neutrino distribution is sampled with a large
number of particles in order to beat down the shot noise. Here we perform very
efficient simulations with light massive neutrinos which require virtually no
extra cost over matter-only simulations, and furthermore do not require tracer
particles for the neutrinos. Instead, we use a weak-field dictionary based on
the recently developed Newtonion motion approach, where Newtonian simulations
for matter are paired with a linear relativistic Boltzmann code to allow for an
absorption of the neutrino evolution into a time-dependent coordinate
transformation. For this, only minimal modifications in existing N-body codes
are required, which we have explicitly implemented in $\textit{gevolution}$ and
$\textit{gadget-2}$. Our fast method determines the non-linear matter power
spectrum to permille-level precision when compared against state-of-the-art
simulations that have been performed for $0.1\,{\rm eV} \leq \sum m_\nu \leq
0.3\,$eV. | The Properties of the Star-Forming Interstellar Medium at z=0.8-2.2 from
HiZELS - II: Star-Formation and Clump Scaling Laws in Gas Rich, Turbulent
Disks: We present adaptive optics assisted integral field spectroscopy of nine
Halpha-selected galaxies at z=0.84--2.23 selected from the HiZELS narrow-band
survey. Our observations map the star-formation and kinematics of these
representative star-forming galaxies on ~kpc-scales. We demonstrate that within
the ISM of these galaxies, the velocity dispersion of the star-forming gas
(\sigma) follows a scaling relation \sigma\propto\Sigma_SFR^(1/n)+constant
(where \Sigma_SFR is the star formation surface density and the constant
includes the stellar surface density). Assuming the disks are marginally stable
(Toomre Q=1), we show that this follows from the Kennicutt-Schmidt relation
(\Sigma_SFR = A\Sigma_gas^n), and we use the data to derive best fit parameters
of n=1.34+/-0.15 and A=3.4_(-1.6)^(+2.5)x10^(-4)Mo/yr/kpc^2, consistent with
the local relation and implying cold molecular gas masses of M_gas=10^(9-10)Mo
and molecular gas fractions M_gas/(M_gas+Mstars)=0.3+/-0.1, with a range of
10-75%. These values confirm the high gas fractions for high-redshift
star-forming galaxies, independent of CO-H_2 conversion factor. We also
identify eleven ~kpc-scale star-forming regions (clumps) within our sample and
show that their sizes are comparable to the wavelength of the fastest growing
unstable mode. The luminosities and velocity dispersions of these clumps follow
the same scaling relations as local HII regions, although their star formation
densities are a factor 15+/-5x higher than typically found locally. We discuss
how the clump properties are related to the disk, and show that their high
masses and luminosities are a consequence of the high disk surface density. |
Tidal virialization of dark matter haloes with clustering dark energy: We extend the analysis of Pace et al., JCAP, 2019, 060, by considering the
virialization process in the extended spherical collapse model for clustering
dark-energy models, i.e., accounting for dark-energy fluctuations. Differently
from the standard approach, here virialization is naturally achieved by
properly modelling deviations from sphericity due to shear and rotation induced
by tidal interactions. We investigate the time evolution of the virial
overdensity $\Delta_\mathrm{vir}$ in seven clustering dynamical dark energy
models and compare the results to the $\Lambda$CDM model and to the
corresponding smooth dark-energy models. Taking into account all the
appropriate corrections, we deduce the abundance of convergence peaks for Rubin
Observatory-LSST and Euclid-like weak-lensing surveys, of Sunyaev-Zel'dovich
peaks for a Simon Observatory-like CMB survey, and of X-ray peaks for an
eROSITA-like survey. Despite the tiny differences in $\Delta_\mathrm{vir}$
between clustering and smooth dark-energy models, owing to the large volumes
covered by these surveys, five out of seven clustering dark-energy models can
be statistically distinguished from $\Lambda$CDM. The contribution of
dark-energy fluctuation cannot be neglected, especially for the
Chevallier-Polarski-Limber and Albrecht-Skordis models, provided the
instrumental configurations provide high signal-to-noise ratio. These results
are almost independent of the tidal virialization model. | UNIONS: The impact of systematic errors on weak-lensing peak counts: UNIONS is an ongoing deep photometric multi-band survey of the Northern sky.
As part of UNIONS, CFIS provides r-band data which we use to study weak-lensing
peak counts for cosmological inference. We assess systematic effects for
weak-lensing peak counts and their impact on cosmological parameters for the
UNIONS survey. In particular, we present results on local calibration,
metacalibration shear bias, baryonic feedback, the source galaxy redshift
estimate, intrinsic alignment, and the cluster member dilution. For each
uncertainty and systematic effect, we describe our mitigation scheme and the
impact on cosmological parameter constraints. We obtain constraints on
cosmological parameters from MCMC using CFIS data and MassiveNuS N-body
simulations as a model for peak counts statistics. Depending on the calibration
(local versus global, and the inclusion of the residual multiplicative shear
bias), the mean matter density parameter $\Omega_m$ can shift up to $-0.024$
($-0.5\sigma$). We also see that including baryonic corrections can shift
$\Omega_m$ by $+0.027$ ($+0.5 \sigma$) with respect to the DM-only simulations.
Reducing the impact of the intrinsic alignment and cluster member dilution
through signal-to-noise cuts can lead to a shift in $\Omega_m$ of $+0.027$
($+0.5 \sigma$). Finally, with a mean redshift uncertainty of $\Delta \bar{z} =
0.03$, we see that the shift of $\Omega_m$ ($+0.001$ which corresponds to
$+0.02 \sigma$) is not significant. This paper investigates for the first time
with UNIONS weak-lensing data and peak counts the impact of systematic effects.
The value of $\Omega_m$ is the most impacted and can shift up to $\sim 0.03$
which corresponds to $0.5\sigma$ depending on the choices for each systematics.
We expect constraints to become more reliable with future (larger) data
catalogues, for which the current pipeline will provide a starting point. |
Inevitable imprints of patchy reionization on the cosmic microwave
background anisotropy: Reionization of the cosmic neutral hydrogen by the first stars in the
Universe is an inhomogeneous process which produces spatial fluctuations in
free electron density. These fluctuations lead to observable signatures in
cosmological probes like the cosmic microwave background (CMB). We explore the
effect of the electron density fluctuations on CMB using photon-conserving
semi-numerical simulations of reionization named \texttt{SCRIPT}. We show that
the amplitude of the kinematic Sunyaev-Zeldovich (kSZ) and $B$-mode
polarization signal depends on the patchiness in the spatial distribution of
electrons along with the dependence on mid-point and extent of the reionization
history. Motivated by this finding, we provide new scaling relations for the
amplitude of kSZ and $B$-mode polarization signal which can capture the effects
arising from the mean optical depth, width of reionization, and spatial
fluctuations in the electron density arising from patchy reionization. We show
that the amplitude of the kSZ and $B$-mode polarization signal exhibits
different dependency on the width of reionization and the patchiness of
reionization, and hence a joint study of these CMB probes will be able to break
the degeneracy. By combining external datasets from 21~cm measurements, the
degeneracy can be further lifted by directly exploring the sizes of the ionized
regions. | Testing flatness of the universe with probes of cosmic distances and
growth: When using distance measurements to probe spatial curvature, the geometric
degeneracy between curvature and dark energy in the distance-redshift relation
typically requires either making strong assumptions about the dark energy
evolution or sacrificing precision in a more model-independent approach.
Measurements of the redshift evolution of the linear growth of perturbations
can break the geometric degeneracy, providing curvature constraints that are
both precise and model-independent. Future supernova, CMB, and cluster data
have the potential to measure the curvature with an accuracy of
sigma(Omega_K)=0.002, without specifying a particular dark energy
phenomenology. In combination with distance measurements, the evolution of the
growth function at low redshifts provides the strongest curvature constraint if
the high-redshift universe is well approximated as being purely matter
dominated. However, in the presence of early dark energy or massive neutrinos,
the precision in curvature is reduced due to additional degeneracies, and
precise normalization of the growth function relative to recombination is
important for obtaining accurate constraints. Curvature limits from distances
and growth compare favorably to other approaches to curvature estimation
proposed in the literature, providing either greater accuracy or greater
freedom from dark energy modeling assumptions, and are complementary due to the
use of independent data sets. Model-independent estimates of curvature are
critical for both testing inflation and obtaining unbiased constraints on dark
energy parameters. |
Pole Dark Energy: Theories with a pole in the kinetic term have been used to great effect in
studying inflation, owing to their quantum stability and attractor properties.
We explore the use of such pole kinetic terms in dark energy theories, finding
an interesting link between thawing and freezing models, and the possibility of
enhanced plateaus with ``superattractor''-like behavior. We assess the
observational viability of pole dark energy, showing that simple models can
give dark energy equation of state evolution with $w(z)<-0.9$ even for
potentials that could not normally achieve this easily. The kinetic term pole
also offers an interesting perspective with respect to the swampland criteria
for such observationally viable dark energy models. | A New Constraint on the Simulation of the Intergalactic Medium through
the Evolution of the Neutral Hydrogen Fraction in the Epoch of Reionization: The thermal history of the intergalactic medium is full of extremely useful
data in the field of astrophysics and cosmology. In other words, by examining
this environment in different redshifts, the effects of cosmology and
astrophysics can be observed side by side. Therefore, simulation is our very
powerful tool to reach a suitable model for the intergalactic medium, both in
terms of cosmology and astrophysics. In this work, we have simulated the
intergalactic medium with the help of the 21cmFAST code and compared the
evolution of the neutral hydrogen fraction in different initial conditions.
Considerable works arbitrarily determine many important effective parameters in
the thermal history of the intergalactic medium without any constraints, and
usually, there is a lot of flexibility for modeling. Nonetheless, in this work,
by focusing on the evolution of the neutral hydrogen fraction in different
models and comparing it with observational data, we have eliminated many models
and introduced only limited simulation models that could confirm the
observations with sufficient accuracy. This issue becomes thoroughly vital from
the point that, in addition to restricting the models through the neutral
hydrogen fraction, it can also impose restrictions on the parameters affecting
its changes. However, we hope that in future works, by enhancing the
observational data and increasing their accuracy, more compatible models with
the history of the intergalactic medium can be achieved. |
Forecast Cosmological Constraints with the 1D Wavelet Scattering
Transform and the Lyman-$α$ forest: We make forecasts for the constraining power of the 1D Wavelet Scattering
Transform (WST) in the context of Lyman-$\alpha$ forest cosmology. Using mock
simulations and a Fisher matrix, we show that there is considerable
cosmological information in the scattering transform coefficients. We estimate
mock covariance matrices assuming uncorrelated Gaussian pixel noise for each
quasar, at a level drawn from a simple lognormal model. The extra information
comes from a smaller estimated covariance in the first-order wavelet power, and
from second-order wavelet coefficients which probe non-Gaussian information in
the forest. Forecast constraints on cosmological parameters from the WST are as
much as an order of magnitude tighter than for the power spectrum. Should these
constraints be confirmed on real data, it would substantially improve
cosmological constraints on, for example, neutrino mass. | Individual Elemental Abundances in Elliptical Galaxies: Using synthetic spectra to gauge the observational consequences of altering
the abundance of individual elements, I determine the observability of new Lick
IDS style indices designed to target individual elements. Then using these new
indices and single stellar population models, I investigate a new method to
determine Balmer series emission in a Sloan Digital Sky Surveys grand average
of quiescent galaxies. I also investigate the effects of an old metal-poor
stellar population on the near ultra violet spectrum through the use of these
new indices and find that the presence of a small old metal-poor population
accounts for discrepancies observed between index trends in the near UV and
optical spectral regimes. Index trends for 74 indices and three data sets are
presented and discussed. Finally, I determine the near nuclear line-strength
gradients of 18 red sequence elliptical Virgo cluster galaxies for 74 indices. |
Large-Scale Clustering of Cosmic Voids: We study the clustering of voids using $N$-body simulations and simple
theoretical models. The excursion-set formalism describes fairly well the
abundance of voids identified with the watershed algorithm, although the void
formation threshold required is quite different from the spherical collapse
value. The void cross bias $b_{\rm c} $ is measured and its large-scale value
is found to be consistent with the peak background split results. A simple
fitting formula for $b_{\rm c} $ is found. We model the void auto-power
spectrum taking into account the void biasing and exclusion effect. A good fit
to the simulation data is obtained for voids with radii $\gtrsim$ 30 Mpc/$h$,
especially when the void biasing model is extended to 1-loop order. However,
the best-fit bias parameters do not agree well with the peak-background split
results. Being able to fit the void auto-power spectrum is particularly
important not only because it is the direct observable in galaxy surveys, but
also our method enables us to treat the bias parameters as nuisance parameters,
which are sensitive to the techniques used to identify voids. | A hybrid map-$C_\ell$ component separation method for primordial CMB
$B$-mode searches: The observation of the polarised emission from the Cosmic Microwave
Background (CMB) from future ground-based and satellite-borne experiments holds
the promise of indirectly detecting the elusive signal from primordial tensor
fluctuations in the form of large-scale $B$-mode polarisation. Doing so,
however, requires an accurate and robust separation of the signal from
polarised Galactic foregrounds. We present a component separation method for
multi-frequency CMB observations that combines some of the advantages of
map-based and power-spectrum-based techniques, and which is direcly applicable
to data in the presence of realistic foregrounds and instrumental noise. We
demonstrate that the method is able to reduce the contamination from Galactic
foregrounds below an equivalent tensor-to-scalar ratio $r_{\rm
FG}\lesssim5\times10^{-4}$, as required for next-generation observatories, for
a wide range of foreground models with varying degrees of complexity. This bias
reduction is associated with a mild $\sim20-30\%$ increase in the final
statistical uncertainties, and holds for large sky areas, and for experiments
targeting both the reionisation and recombination bumps in the $B$-mode power
spectrum. |
Planck Intermediate Results. XXXVI. Optical identification and redshifts
of Planck SZ sources with telescopes in the Canary Islands Observatories: We present the results of approximately three years of observations of Planck
Sunyaev-Zeldovich (SZ) sources with telescopes at the Canary Islands
observatories as part of the general optical follow-up programme undertaken by
the Planck collaboration. In total, 78 SZ sources are discussed. Deep-imaging
observations were obtained for most of these sources; spectroscopic
observations in either in long-slit or multi-object modes were obtained for
many. We effectively used 37.5 clear nights. We found optical counterparts for
73 of the 78 candidates. This sample includes 53 spectroscopic redshift
determinations, 20 of them obtained with a multi-object spectroscopic mode. The
sample contains new redshifts for 27 Planck clusters that were not included in
the first Planck SZ source catalogue (PSZ1). | A New Empirical Method to Infer the Starburst History of the Universe
from Local Galaxy Properties: The centers of bulges are formed dissipationally via gas inflows over short
timescales: the 'starburst' mode of star formation (SF). Recent work has shown
that detailed observations can be used to separate the stellar mass profile of
these 'burst relic' components in local systems. Together with the assumption
that some Kennicutt-Schmidt law holds, and that the burst was indeed a
dissipational gas-rich event, we show that the observed profiles can be
inverted to obtain the time and space-dependent SF history of each burst.
Performing this with a large sample of well-studied spheroids, we show that the
implied bursts scale in magnitude, mass, peak SFR, and spatial extent with
galaxy mass in simple manner, and provide fits to these correlations. Burst
masses are ~10% the total spheroid mass; timescales a mass-independent ~10^8
yr; peak SFR ~M_burst/t_burst; and they decay in power-law fashion ~t^-2.4.
Sizes are ~0.1 R_e(spheroid), but grow with time. Combined with measurements of
the nuclear stellar population ages of these systems (i.e. burst times), it is
possible to re-construct the burst contribution to the distribution of SFRs and
IR luminosity functions at all redshifts. The burst LF agrees well with
observed IR LFs at the brightest luminosities, at z=0-2. At low-L, bursts are
always unimportant; the transition to their importance increases from ULIRG
luminosities at z~0 to HyLIRG luminosities at z~2. At all redshifts, bursts are
a small fraction (~5-10%) of the total SFR density. We discuss possible
implications of tension between maximum relic stellar mass densities in massive
systems, and estimated number counts of brightest sub-millimeter galaxies. |
Tensor Detection Severely Constrains Axion Dark Matter: The recent detection of B-modes by BICEP2 has non-trivial implications for
axion dark matter implied by combining the tensor interpretation with
isocurvature constraints from Planck. In this paper the measurement is taken as
fact, and its implications considered, though further experimental verification
is required. In the simplest inflation models $r=0.2$ implies $H_I=1.1\times
10^{14}\text{ GeV}$. If the axion decay constant $f_a<H_I/2\pi$ constraints on
the dark matter (DM) abundance alone rule out the QCD axion as DM for $m_a
\lesssim 52\chi^{6/7}\,\mu\text{eV}$ (where $\chi>1$ accounts for theoretical
uncertainty). If $f_a>H_I/2\pi$ then vacuum fluctuations of the axion field
place conflicting demands on axion DM: isocurvature constraints require a DM
abundance which is too small to be reached when the back reaction of
fluctuations is included. High $f_a$ QCD axions are thus ruled out. Constraints
on axion-like particles, as a function of their mass and DM fraction, are also
considered. For heavy axions with $m_a\gtrsim 10^{-22}\text{ eV}$ we find
$\Omega_a/\Omega_d\lesssim 10^{-3}$, with stronger constraints on heavier
axions. Lighter axions, however, are allowed and (inflationary)
model-independent constraints from the CMB temperature power spectrum and large
scale structure are stronger than those implied by tensor modes. | Study of systematics effects on the Cross Power Spectrum of 21 cm Line
and Cosmic Microwave Background using Murchison Widefield Array Data: Observation of the 21cm line signal from neutral hydrogen during the Epoch of
Reionization is challenging due to extremely bright Galactic and extragalactic
foregrounds and complicated instrumental calibration. A reasonable approach for
mitigating these problems is the cross correlation with other observables. In
this work, we present the first results of the cross power spectrum (CPS)
between radio images observed by the Murchison Widefield Array and the cosmic
microwave background (CMB), measured by the Planck experiment. We study the
systematics due to the ionospheric activity, the dependence of CPS on group of
pointings, and frequency. The resulting CPS is consistent with zero because the
error is dominated by the foregrounds in the 21cm observation. Additionally,
the variance of the signal indicates the presence of unexpected systematics
error at small scales. Furthermore, we reduce the error by one order of
magnitude with application of a foreground removal using a polynomial fitting
method. Based on the results, we find that the detection of the 21cm-CMB CPS
with the MWA Phase I requires more than 99.95% of the foreground signal
removed, 2000 hours of deep observation and 50% of the sky fraction coverage. |
Disentangling magnification in combined shear-clustering analyses: We investigate the sensitivity to the effects of lensing magnification on
large-scale structure analyses combining photometric cosmic shear and galaxy
clustering data (i.e. the now commonly called "3$\times$2-point" analysis).
Using a Fisher matrix bias formalism, we disentangle the contribution to the
bias on cosmological parameters caused by ignoring the effects of magnification
in a theory fit from individual elements in the data vector, for Stage-III and
Stage-IV surveys, assuming well-known redshift distributions, sample selection
based on magnitude, and magnification strengths inferred from CFHTLenS and DES
Y1 data. We show that the removal of elements of the data vectors that are
dominated by magnification does not guarantee a reduction in the cosmological
bias due to the magnification signal, but can instead increase the sensitivity
to magnification. We find that the most sensitive elements of the data vector
come from the shear-clustering cross-correlations, particularly between the
highest-redshift shear bin and any lower-redshift lens sample, and that the
parameters $\Omega_{M}$, $S_8=\sigma_8\sqrt{\Omega_M/0.3}$ and $w_0$ show the
most significant biases for both survey models. Our forecasts predict that
current analyses are not significantly biased by magnification, but this bias
will become highly significant with the continued increase of statistical power
in the near future. We therefore conclude that future surveys should measure
and model the magnification as part of their flagship "3$\times$2-point"
analysis. | The scaling of primordial gauge fields: The large-scale magnetic fields arising from the quantum mechanical
fluctuations of the hypercharge are investigated when the evolution of the
gauge coupling is combined with a sufficiently long inflationary stage. In this
framework the travelling waves associated with the quantum mechanical initial
conditions turn asymptotically into standing waves which are the gauge analog
of the Sakharov oscillations. Even if the rate of dilution of the hypermagnetic
and hyperelectric fields seems to be superficially smaller than expected from
the covariant conservation of the energy-momentum tensor, the standard
evolution for wavelengths larger than the Hubble radius fully accounts for this
anomalous scaling which is anyway unable to increase the amplitude of the
magnetic power spectra after symmetry breaking. An effective amplification of
the gauge power spectra may instead occur when the post-inflationary expansion
rate is slower than radiation. We stress that the modulations of the gauge
power spectra freeze as soon as the relevant wavelengths reenter the Hubble
radius and not at the end of inflation. After the Mpc scale crosses the
comoving Hubble radius the scaling of the magnetic power spectrum follows from
the dominance of the conductivity. From these two observations the late-time
values of the magnetic power spectra are accurately computed in the case of a
nearly scale-invariant slope and contrasted with the situation where the phases
of Sakharov oscillations are not evaluated at horizon crossing but at the end
of inflation, i.e. when all the wavelengths relevant for magnetogenesis are
still larger than the comoving horizon. |
Chandra deep observation of XDCP J0044.0-2033, a massive galaxy cluster
at z>1.5: We report the analysis of the Chandra observation of XDCP J0044.0-2033, a
massive, distant (z=1.579) galaxy cluster discovered in the XDCP survey. The
total exposure time of 380 ks with Chandra ACIS-S provides the deepest X-ray
observation currently achieved on a massive, high redshift cluster. Extended
emission from the Intra Cluster Medium (ICM) is detected at a very high
significance level (S/N~20) on a circular region with a 44" radius,
corresponding to $R_{ext}=375$ kpc at the cluster redshift. We perform an X-ray
spectral fit of the ICM emission modeling the spectrum with a
single-temperature thermal mekal model. Our analysis provides a global
temperature $kT=6.7^{+1.3}_{-0.9}$ keV, and a iron abundance $Z_{Fe} =
0.41_{-0.26}^{+0.29}Z_{Fe_\odot}$ (error bars correspond to 1 $\sigma$). We fit
the background-subtracted surface brightness profile with a single
$\beta$-model out to 44", finding a rather flat profile with no hints of a cool
core. We derive the deprojected electron density profile and compute the ICM
mass within the extraction radius $R_{ext}=375$ kpc to be $M_{ICM}(r<R_{ext}) =
(1.48 \pm 0.20) \times 10^{13} M_\odot$. Under the assumption of hydrostatic
equilibrium and assuming isothermality within $R_{ext}$, the total mass is
$M_{2500}= 1.23_{-0.27}^{+0.46} \times 10 ^{14} M_\odot$ for $R_{2500} =
240_{-20}^{+30}$ kpc. Extrapolating the profile at radii larger than the
extraction radius $R_{ext}$ we find $M_{500} = 3.2_{-0.6}^{+0.9} \times 10
^{14}M_\odot$ for $R_{500} = 562_{-37}^{+50}$ kpc. This analysis establishes
the existence of virialized, massive galaxy clusters at redshift $z\sim 1.6$,
paving the way to the investigation of the progenitors of the most massive
clusters today. Given its mass and the XDCP survey volume, XDCP J0044.0-2033
does not create significant tension with the WMAP-7 $\Lambda$CDM cosmology. | Clustering and redshift-space distortions in modified gravity models
with massive neutrinos: Modified gravity and massive neutrino cosmologies are two of the most
interesting scenarios that have been recently explored to account for possible
observational deviations from the concordance $\Lambda$-cold dark matter
($\Lambda$CDM) model. In this context, we investigated the large-scale
structure of the Universe by exploiting the \dustp simulations that implement,
simultaneously, the effects of $f(R)$ gravity and massive neutrinos. To study
the possibility of breaking the degeneracy between these two effects, we
analysed the redshift-space distortions in the clustering of dark matter haloes
at different redshifts. Specifically, we focused on the monopole and quadrupole
of the two-point correlation function, both in real and redshift space. The
deviations with respect to $\Lambda$CDM model have been quantified in terms of
the linear growth rate parameter. We found that redshift-space distortions
provide a powerful probe to discriminate between $\Lambda$CDM and modified
gravity models, especially at high redshifts ($z \gtrsim 1$), even in the
presence of massive neutrinos. |
H$α$ Star Formation Rates of $z$ > 1 Galaxy Clusters in the IRAC
Shallow Cluster Survey: We present Hubble Space Telescope near-IR spectroscopy for 18 galaxy clusters
at 1.0 < $z$ < 1.5 in the IRAC Shallow Cluster Survey. We use Wide Field Camera
3 grism data to spectroscopically identify H$\alpha$ emitters in both the cores
of galaxy clusters as well as in field galaxies. We find a large
cluster-to-cluster scatter in the star formation rates within a projected
radius of 500 kpc, and many of our clusters (~60%) have significant levels of
star formation within a projected radius of 200 kpc. A stacking analysis
reveals that dust reddening in these star-forming galaxies is positively
correlated with stellar mass and may be higher in the field than the cluster at
a fixed stellar mass. This may indicate a lower amount of gas in star-forming
cluster galaxies than in the field population. Also, H$\alpha$ equivalent
widths of star-forming galaxies in the cluster environment are still suppressed
below the level of the field. This suppression is most significant for lower
mass galaxies (log M$_{*}$ < 10.0 M$_{\odot}$). We therefore conclude that
environmental effects are still important at 1.0 < $z$ < 1.5 for star-forming
galaxies in galaxy clusters with log M$_{*}$ < 10.0 M$_{\odot}$. | UV-dropout Galaxies in the GOODS-South Field from WFC3 Early Release
Science Observations: We combine new high sensitivity ultraviolet (UV) imaging from the Wide Field
Camera 3 (WFC3) on the Hubble Space Telescope (HST) with existing deep
HST/Advanced Camera for Surveys (ACS) optical images from the Great
Observatories Origins Deep Survey (GOODS) program to identify UV-dropouts,
which are Lyman break galaxy (LBG) candidates at z~1-3. These new HST/WFC3
observations were taken over 50 sq.arcmin in the GOODS-South field as a part of
the Early Release Science program. The uniqueness of these new UV data is that
they are observed in 3 UV/optical (WFC3 UVIS) channel filters (F225W, F275W and
F336W), which allows us to identify three different sets of UV-dropout samples.
We apply Lyman break dropout selection criteria to identify F225W-, F275W- and
F336W-dropouts, which are z~1.7, 2.1 and 2.7 LBG candidates, respectively. Our
results are as follows: (1) these WFC3 UVIS filters are very reliable in
selecting LBGs with z~2.0, which helps to reduce the gap between the well
studied z~>3 and z~0 regimes, (2) the combined number counts agrees very well
with the observed change in the surface densities as a function of redshift
when compared with the higher redshift LBG samples; and (3) the best-fit
Schechter function parameters from the rest-frame UV luminosity functions at
three different redshifts fit very well with the evolutionary trend of the
characteristic absolute magnitude, and the faint-end slope, as a function of
redshift. This is the first study to illustrate the usefulness of the WFC3 UVIS
channel observations to select z<3 LBGs. The addition of the new WFC3 on the
HST has made it possible to uniformly select LBGs from z~1 to z~9, and
significantly enhance our understanding of these galaxies using HST sensitivity
and resolution. |
Cosmological evolution of warm dark matter fluctuations II: Solution
from small to large scales and keV sterile neutrinos: We solve the cosmological evolution of warm dark matter (WDM) density
fluctuations with the Volterra integral equations of paper I. In the absence of
neutrinos, the anisotropic stress vanishes and the Volterra equations reduce to
a single integral equation. We solve numerically this equation both for DM
fermions decoupling at equilibrium and DM sterile neutrinos decoupling out of
equilibrium. We give the exact analytic solution for the density fluctuations
and gravitational potential at zero wavenumber. We compute the density contrast
as a function of the scale factor a for a wide range of wavenumbers k. At fixed
a, the density contrast grows with k for k < k_c while it decreases for k >
k_c, (k_c ~ 1.6/Mpc). The density contrast depends on k and a mainly through
the product k a exhibiting a self-similar behavior. Our numerical density
contrast for small k gently approaches our analytic solution for k = 0. For
fixed k < 1/(60 kpc), the density contrast generically grows with a while for k
> 1/(60 kpc) it exhibits oscillations since the RD era which become stronger as
k grows. We compute the transfer function of the density contrast for thermal
fermions and for sterile neutrinos in: a) the Dodelson-Widrow (DW) model and b)
in a model with sterile neutrinos produced by a scalar particle decay. The
transfer function grows with k for small k and then decreases after reaching a
maximum at k = k_c reflecting the time evolution of the density contrast. The
integral kernels in the Volterra equations are nonlocal in time and their
falloff determine the memory of the past evolution since decoupling. This
falloff is faster when DM decouples at equilibrium than when it decouples out
of equilibrium. Although neutrinos and photons can be neglected in the MD era,
they contribute in the MD era through their memory from the RD era. | Scale-dependent non-Gaussianity and the CMB Power Asymmetry: We introduce an alternative parametrisation for the scale dependence of the
non-linearity parameter $f_{\rm NL}$ in quasi-local models of non-Gaussianity.
Our parametrisation remains valid when $f_{\rm NL}$ changes sign, unlike the
commonly adopted power law ansatz $f_{\rm NL}(k) \propto k^{ n_{f_{\rm NL}} }$.
We motivate our alternative parametrisation by appealing to the
self-interacting curvaton scenario, and as an application, we apply it to the
CMB power asymmetry. Explaining the power asymmetry requires a strongly scale
dependent non-Gaussianity. We show that regimes of model parameter space where
$f_{\rm NL}$ is strongly scale dependent are typically associated with a large
$g_{\rm NL}$ and quadrupolar power asymmetry, which can be ruled out by
existing observational constraints. |
Hydrodynamical simulations and semi-analytic models of galaxy formation:
two sides of the same coin: In this work we develop a new method to turn a state-of-the-art
hydrodynamical cosmological simulation of galaxy formation (HYD) into a simple
semi-analytic model (SAM). This is achieved by summarizing the efficiencies of
accretion, cooling, star formation, and feedback given by the HYD, as functions
of the halo mass and redshift. Surprisingly, by turning the HYD into a SAM, we
conserve the mass of individual galaxies, with deviations at the level of 0.1
dex, on an object-by-object basis. This is true for all redshifts, and for the
mass of stars and gas components, although the agreement reaches 0.2 dex for
satellite galaxies at low redshift. We show that the same level of accuracy is
obtained even in case the SAM uses only one phase of gas within each galaxy.
Moreover, we demonstrate that the formation history of one massive galaxy
provides sufficient information for the SAM to reproduce the population of
galaxies within the entire cosmological box. The reasons for the small scatter
between the HYD and SAM galaxies are: a) The efficiencies are matched as
functions of the halo mass and redshift, meaning that the evolution within
merger-trees agrees on average. b) For a given galaxy, efficiencies fluctuate
around the mean value on time scales of 0.2-2 Gyr. c) The various mass
components of galaxies are obtained by integrating the efficiencies over time,
averaging out these fluctuations. We compare the efficiencies found here to
standard SAM recipes and find that they often deviate significantly. For
example, here the HYD shows smooth accretion that is less effective for low
mass haloes, and is always composed of hot or dilute gas; cooling is less
effective at high redshift; and star formation changes only mildly with cosmic
time. The method developed here can be applied in general to any HYD, and can
thus serve as a common language for both HYDs and SAM (Abridged). | The Mid-IR and X-ray Selected QSO Luminosity Function: We present the J-band luminosity function of 1838 mid-infrared and X-ray
selected AGNs in the redshift range 0<z<5.85. These luminosity functions are
constructed by combining the deep multi-wavelength broad-band observations from
the UV to the mid-IR of the NDWFS Bootes field with the X-ray observations of
the XBootes survey and the spectroscopic observations of the same field by
AGES. Our sample is primarily composed of IRAC-selected AGNs, targeted using
modifications of the Stern et al.(2005) criteria, complemented by MIPS 24
microns and X-ray selected AGNs to alleviate the biases of IRAC mid-IR
selection against z~4.5 quasars and AGNs faint with respect to their hosts.
This sample provides an accurate link between low and high redshift AGN
luminosity functions and does not suffer from the usual incompleteness of
optical samples at z~3. We find that the space density of the brightest quasars
strongly decreases from z=3 to z=0, while the space density of faint quasars is
at least flat, and possibly increasing, over the same redshift range. At z>3 we
observe a decrease in the space density of quasars of all brightnesses. We
model the luminosity function by a double power-law and find that its evolution
cannot be described by either pure luminosity or pure density evolution, but
must be a combination of both. Our best-fit model has bright and faint
power-law indices consistent with the low redshift measurements based on the
2QZ and 2SLAQ surveys and it generally agrees with the number of bright quasars
predicted by other LFs at all redshifts. If we construct the QSO luminosity
function using only the IRAC-selected AGNs, we find that the biases inherent to
this selection method significantly modify the behavior of phi*(z) only for z<1
and have no significant impact upon the characteristic magnitude M*_J(z). |
Nuclear Rings in Galaxies---A Kinematic Perspective: We combine DensePak integral field unit and TAURUS Fabry-Perot observations
of 13 nuclear rings to show an interconnection between the kinematic properties
of the rings and their resonant origin. The nuclear rings have regular and
symmetric kinematics, and lack strong non-circular motions. This symmetry,
coupled with a direct relationship between the position angles and
ellipticities of the rings and those of their host galaxies, indicate the rings
are in the same plane as the disc and are circular. From the rotation curves
derived, we have estimated the compactness (v^2/r) up to the turnover radius,
which is where the nuclear rings reside. We find that there is evidence of a
correlation between compactness and ring width and size. Radially wide rings
are less compact, and thus have lower mass concentration. The compactness
increases as the ring width decreases. We also find that the nuclear ring size
is dependent on the bar strength, with weaker bars allowing rings of any size
to form. | Local non-Gaussianities from cross-correlations between the CMB and
21-cm: The 21-cm brightness temperature fluctuation from the Dark Ages ($z \simeq
30-100$) will allow us to probe the inflationary epoch on very small scales
($>0.1 \, \mbox{Mpc}^{-1}$), inaccessible to cosmic microwave background
experiments. Combined with the possibility to collect information from
different redshift slices, the 21-cm bispectrum has the potential to
significantly improve constraints on primordial non-Gaussianity. However,
recent work has shown secondary effects source off-diagonal terms in the
covariance matrix which can significantly affect forecasted constraints,
especially in signals that peak in the squeezed configuration, such as the
local bispectrum. In this paper we propose the three-point $\langle 21-21-\rm
CMB \rangle$ bispectrum cross-correlation as a new independent observational
channel sensitive to local primordial non-Gaussianity. We find that, contrary
to the 21-cm bispectrum, secondary contributions are subdominant to the
primordial signal for values $f_{\rm NL}^{\rm loc} \sim 1$, resulting in
negligible effects from off-diagonal terms in the covariance matrix. We
forecast that CMB $T$ and $E$ modes cross-correlated with an ideal cosmic
variance-limited 21-cm experiment with a $0.1$ MHz frequency and $0.1$
arc-minute angular resolution could reach $f_{\rm NL}^{\rm loc} \sim 6 \times
10^{-3}$. This forecast suggests cross-correlation between CMB and 21-cm
experiments could provide a viable alternative to 21-cm auto-spectra in
reaching unprecedented constraints on primordial local non-Gaussianities. |
A High Resolution View of the Warm Absorber in the Quasar MR2251-178: High resolution X-ray spectroscopy of the warm absorber in the nearby quasar,
MR2251-178 (z = 0.06398) is presented. The observations were carried out in
2011 using the Chandra High Energy Transmission Grating and the XMM-Newton
Reflection Grating Spectrometer, with net exposure times of approximately 400
ks each. A multitude of absorption lines from C to Fe are detected, revealing
at least 3 warm absorbing components ranging in ionization parameter from
log(\xi/erg cm s^-1) = 1-3 and with outflow velocities < 500 km/s. The lowest
ionization absorber appears to vary between the Chandra and XMM-Newton
observations, which implies a radial distance of between 9-17 pc from the black
hole. Several broad soft X-ray emission lines are strongly detected, most
notably from He-like Oxygen, with FWHM velocity widths of up to 10000 km/s,
consistent with an origin from Broad Line Region (BLR) clouds. In addition to
the warm absorber, gas partially covering the line of sight to the quasar
appears to be present, of typical column density N_H = 10^23 cm^-2. We suggest
that the partial covering absorber may arise from the same BLR clouds
responsible for the broad soft X-ray emission lines. Finally the presence of a
highly ionised outflow in the iron K band from both 2002 and 2011 Chandra HETG
observations appears to be confirmed, which has an outflow velocity of -15600
\pm 2400 km/s. However a partial covering origin for the iron K absorption
cannot be excluded, resulting from low ionization material with little or no
outflow velocity. | SDSS J102623.61+254259.5: the second most distant blazar at z=5.3: The radio-loud quasar SDSS J102623.61+254259.5, at a redshift z=5.3, is one
of the most distant radio-loud objects. Since its radio flux exceeds 100 mJy at
a few GHz, it is also one of the most powerful radio-loud sources. We propose
that this source is a blazar, i.e. we are seeing its jet at a small viewing
angle. This claim is based on the spectral energy distribution of this source,
and especially on its strong and hard X-ray spectrum, as seen by Swift, very
typical of powerful blazars. Observations by the Gamma-Ray Burst
Optical/Near-Infrared Detector (GROND) and by theWide-field Infrared Survey
Explorer (WISE) allow to establish the thermal nature of the emission in the
near IR-optical band. Assuming that this is produced by a standard accretion
disk, we derive that it emits a luminosity of L_d \simeq 9 \times 10^46 erg
s^{-1} and that the black hole has a mass between 2 and 5 billion solar masses.
This poses interesting constraints on the mass function of heavy (> 10^9 M_sun)
black holes at high redshifts. |
Near-infrared spectroscopy of a nitrogen-loud quasar SDSS J1707+6443: We present near-infrared spectroscopy of the z=3.2 quasar SDSS J1707+6443,
obtained with MOIRCS on the Subaru Telescope. This quasar is classified as a
"nitrogen-loud" quasar because of the fairly strong NIII] and NIV]
semi-forbidden emission lines from the broad-line region (BLR) observed in its
rest-frame UV spectrum. However, our rest-frame optical spectrum from MOIRCS
shows strong [OIII] emission from the narrow-line region (NLR) suggesting that,
at variance with the BLR, NLR gas is not metal-rich. In order to reconcile
these contradictory results, there may be two alternative possibilities; (1)
the strong nitrogen lines from the BLR are simply due to a very high relative
abundance of nitrogen rather than to a very high BLR metallicity, or (2) the
BLR metallicity is not representative of the metallicity of the host galaxy,
better traced by the NLR. In either case, the strong broad nitrogen lines in
the UV spectrum are not indication of a chemically enriched host galaxy. We
estimated the black hole mass and Eddington ratio of this quasar from the
velocity width of both CIV and H_beta, that results in log(M_BH/M_sun) = 9.50
and log(L_bol/L_Edd) = -0.34. The relatively high Eddington ratio is consistent
with our earlier result that strong nitrogen emission from BLRs is associated
with high Eddington ratios. Finally, we detected significant [NeIII] emission
from the NLR, implying a quite high gas density of n~10^6 cm^-3 and suggesting
a strong coupling between quasar activity and dense interstellar clouds in the
host galaxy. | The Uchuu-SDSS galaxy lightcones: a clustering, RSD and BAO study: We present the data release of the Uchuu-SDSS galaxies: a set of 32
high-fidelity galaxy lightcones constructed from the large Uchuu 2.1 trillion
particle $N$-body simulation using Planck cosmology. We adopt subhalo abundance
matching to populate the Uchuu-box halo catalogues with SDSS galaxy
luminosities. These cubic box galaxy catalogues generated at several redshifts
are combined to create the set of lightcones with redshift-evolving galaxy
properties. The Uchuu-SDSS galaxy lightcones are built to reproduce the
footprint and statistical properties of the SDSS main galaxy survey, along with
stellar masses and star formation rates. This facilitates direct comparison of
the observed SDSS and simulated Uchuu-SDSS data. Our lightcones reproduce a
large number of observational results, such as the distribution of galaxy
properties, the galaxy clustering, the stellar mass functions, and the halo
occupation distributions. Using the simulated and real data we select samples
of bright red galaxies at $z_\mathrm{eff}=0.15$ to explore Redshift Space
Distortions and Baryon Acoustic Oscillations (BAO) utilizing a full-shape
analytical model of the two-point correlation function. We create a set of 5100
galaxy lightcones using GLAM N-body simulations to compute covariance errors.
We report a $\sim 30\%$ precision increase on $f\sigma_8$, due to our better
estimate of the covariance matrix. From our BAO-inferred $\alpha_{\parallel}$
and $\alpha_{\perp}$ parameters, we obtain the first SDSS measurements of the
Hubble and angular diameter distances $D_\mathrm{H}(z=0.15) / r_d =
27.9^{+3.1}_{-2.7}$, $D_\mathrm{M}(z=0.15) / r_d = 5.1^{+0.4}_{-0.4}$. Overall,
we conclude that the Planck LCDM cosmology nicely explains the observed
large-scale structure statistics of SDSS. All data sets are made publicly
available. |
The XMM-Newton Wide Angle Survey (XWAS): This programme is aimed at obtaining one of the largest X-ray selected
samples of identified active galactic nuclei to date in order to characterise
such a population at intermediate fluxes, where most of the Universe's
accretion power originates. We present the XMM-Newton Wide Angle Survey (XWAS),
a new catalogue of almost a thousand X-ray sources spectroscopically identified
through optical observations. A sample of X-ray sources detected in 68
XMM-Newton pointed observations was selected for optical multi-fibre
spectroscopy. Optical counterparts and corresponding photometry of the X-ray
sources were obtained from the SuperCOSMOS Sky Survey. Candidates for
spectroscopy were initially selected with magnitudes down to R~21, with
preference for X-ray sources having a flux F(0.5-4.5 keV) >10^-14 erg s^-1
cm^-2. Optical spectroscopic observations performed at the Anglo Australian
Telescope Two Degree Field were analysed, and the derived spectra were
classified based on optical emission lines. We have identified through optical
spectroscopy 940 X-ray sources over ~11.8 deg^2 of the sky. Source populations
in our sample can be summarised as 65% broad line active galactic nuclei
(BLAGN), 16% narrow emission line galaxies (NELGs), 6% absorption line galaxies
(ALGs) and 13% stars. An active nucleus is likely to be present also in the
large majority of the X-ray sources spectroscopically classified as NELGs or
ALGs. Sources lie in high-galactic latitude (|b| > 20 deg) XMM-Newton fields
mainly in the southern hemisphere. Due to the large parameter space in redshift
(0 < z < 4.25) and flux (10^-15 < F(0.5-4.5 keV) < 10^-12 erg s^-1 cm^-2)
covered by the XWAS this work provides an excellent resource to further study
subsamples and particular cases. The overall properties of the extragalactic
objects are presented in this paper. | Cosmic Tsunamis in Modified Gravity: Disruption of Screening Mechanisms
from Scalar Waves: Extending general relativity by adding extra degrees of freedom is a popular
approach for explaining the accelerated expansion of the Universe and to build
high energy completions of the theory of gravity. The presence of such new
degrees of freedom is, however, tightly constrained from several observations
and experiments that aim to test general relativity in a wide range of scales.
The viability of a given modified theory of gravity, therefore, strongly
depends on the existence of a screening mechanism that suppresses the extra
degrees of freedom. We perform simulations, and find that waves propagating in
the new degrees of freedom can significantly impact the efficiency of some
screening mechanisms, thereby threatening the viability of these modified
gravity theories. Specifically, we show that the waves produced in the
symmetron model can increase the amplitude of the fifth force and the
parametrized post-Newtonian parameters by several orders of magnitude. |
Feedback from central black holes in elliptical galaxies. III: models
with both radiative and mechanical feedback: We find, from high-resolution hydro simulations, that winds from AGN
effectively heat the inner parts (~100 pc) of elliptical galaxies, reducing
infall to the central SMBH; and radiative (photoionization and X-ray) heating
reduces cooling flows at the kpc scale. Including both types of feedback with
(peak) efficiencies of 3 10^{-4} < epsilon_mech < 10^{-3} and of epsilon_rad
~10^{-1.3} respectively, produces systems having duty-cycles, central SMBH
masses, X-ray luminosities, optical light profiles, and E+A spectra in accord
with the broad suite of modern observations of massive elliptical systems. Our
main conclusion is that mechanical feedback (including all three of energy,
momentum and mass) is necessary but the efficiency, based on several
independent arguments must be a factor of 10 lower than is commonly assumed.
Bursts are frequent at z>1 and decline in frequency towards the present epoch
as energy and metal rich gas are expelled from the galaxies into the
surrounding medium. For a representative galaxy of final stellar mass ~3
10^{11} Msun, roughly 3 10^{10} Msun of recycled gas has been added to the ISM
since z~2 and, of that, roughly 63% has been expelled from the galaxy, 19% has
been converted into new metal rich stars in the central few hundred parsecs,
and 2% has been added to the central SMBH, with the remaining 16% in the form
hot X-ray emitting ISM. The bursts occupy a total time of ~170 Myr, which is
roughly 1.4% of the available time. Of this time, the central SMBH would be
seen as an UV or optical source for ~45% and ~71$% of the time, respectively.
Restricting to the last 8.5 Gyr, the burst occupy ~44 Myr, corresponding to a
fiducial duty-cycle of ~5 10^{-3}. | Supernova Legacy Survey: Using Spectral Signatures To Improve Type Ia
Supernovae As Distance Indicators: GMOS optical long-slit spectroscopy at the Gemini-North telescope was used to
classify targets from the Supernova Legacy Survey (SNLS) from July 2005 and May
2006 - May 2008. During this time, 95 objects were observed. Where possible the
objects' redshifts (z) were measured from narrow emission or absorption
features in the host galaxy spectrum, otherwise they were measured from the
broader supernova features. We present spectra of 68 confirmed or probable SNe
Ia from SNLS with redshifts in the range 0.17 \leq z \leq 1.02. In combination
with earlier SNLS Gemini and VLT spectra, we used these new observations to
measure pseudo-equivalent widths (EWs) of three spectral features - CaII H&K,
SiII and MgII - in 144 objects and compared them to the EWs of low-redshift SNe
Ia from a sample drawn from the literature. No signs of changes with z are seen
for the CaII H&K and MgII features. Systematically lower EW SiII is seen at
high redshift, but this can be explained by a change in demographics of the SNe
Ia population within a two-component model combined with an observed
correlation between EW SiII and photometric lightcurve stretch. |
The quasar SDSS J142507.32+323137.4 : dual AGNs?: We analyze the optical spectrum of type 1 QSO SDSS J1425+3231. This ob- ject
is interesting since its narrow emission lines such as [O
III]{\lambda}{\lambda}4959, 5007 are double- peaked, and the line structure can
be modeled well by three Gaussian components: two components for the two peaks
(we refer the peaks at low/high redshift as "the blue/red component") and
another one for the line wing which has the same line center as that of the
blue component, but ~ 3 times broader. The separation between the blue and red
components is ~ 500 km/s with blue component ~ 2 times broader than the red
one. The H{\beta} emission can be separated into four components: two for the
double-peaked narrow line and two for the broad line which comes from the broad
line region (BLRs). The black hole mass estimated from the broad H{\beta}
emission line using the typical reverberation map- ping relation is 0.85 \times
108M\odot, which is consistent with that derived from parameters of [O
III]{\lambda} 5007 of the blue component. We suggest this QSO might be a dual
AGN system, the broad H{\beta} emission line is mainly contributed by the
primary black hole (traced by the blue component) while the broad H{\beta}
component of the secondary black hole (traced by the red component) is hard to
be separated out considering a resolution of ~2000 of SDSS spectra or it is
totally obscured by the dusty torus. | Primordial non-Gaussianity as a signature of pre-inflationary radiation
era: Primordial non-Gaussianity generated in an inflationary model where inflation
is preceded by a radiation era is discussed. It is shown that both bispectrum
and trispectrum non-Gaussianities are enhanced due to the presence of
pre-inflationary radiation era. One distinguishing feature of such a scenario
is that the trispectrum non-Gaussianity is larger than the bispectrum one. |
Big bang nucleosynthesis with rapidly varying G: We examine big bang nucleosynthesis (BBN) in models with a time-varying
gravitational constant $G$, when this time variation is rapid on the scale of
the expansion rate $H$, i.e, $\dot G/G \gg H$. Such models can arise naturally
in the context of scalar-tensor theories of gravity and result in additional
terms in the Friedman equation. We examine two representative models: a
step-function evolution for $G$ and a rapidly-oscillating $G$. In the former
case, the additional terms in the Friedman equation tend to cancel the effects
of an initial value of $G$ that differs from the present-day value. In the case
of deuterium, this effect is large enough to reverse the sign of the change in
(D/H) for a given change in the initial value of $G$. For rapidly-oscillating
$G$, the effect on the Friedman equation is similar to that of adding a vacuum
energy density, and BBN allows upper limits to be placed on the product of the
oscillation frequency and amplitude. The possibility that a rapidly oscillating
$G$ could mimic a cosmological constant is briefly discussed. | Inflows and outflows in nearby active galactic nuclei from integral
field spectroscopy: I report recent results on the kinematics of the inner few hundred parsecs
(pc) around nearby active galactic nuclei (AGN) at a sampling of a few pc to a
few tens of pc, using optical and near-infrared (near-IR) integral field
spectroscopy obtained with the Gemini telescopes. The stellar kinematics of the
hosts - comprised mostly of spiral galaxies - are dominated by circular
rotation in the plane of the galaxy. Inflows with velocities of ~ 50 km/s have
been observed along nuclear spiral arms in (optical) ionized gas emission for
low-luminosity AGN and in (near-IR) molecular gas emission for
higher-luminosity AGN. We have also observed gas rotating in the galaxy plane,
sometimes in compact (few tens of pc) disks which may be fuelling the AGN.
Outflows have been observed mostly in ionized gas emission from the narrow-line
region, whose flux distributions and kinematics frequently correlate with radio
flux distributions. Channel maps along the emission-line profiles reveal
velocities as high as ~ 600 km/s. Mass outflow rates in ionized gas range from
0.01 to 0.001 solar masses per year and are 10-100 times larger than the mass
accretion rates to the AGN, supporting an origin for the bulk of the outflow in
gas from the galaxy plane entrained by a nuclear jet or accretion disk wind. |
Spectral distortion constraints on photon injection from low-mass
decaying particles: Spectral distortions (SDs) of the cosmic microwave background (CMB) provide a
powerful tool for studying particle physics. Here we compute the distortion
signals from decaying particles that convert directly into photons at different
epochs during cosmic history, focusing on injection energies
$E_\mathrm{inj}\lesssim 20\,\mathrm{keV}$. We deliver a comprehensive library
of SD solutions that can be used to study a wide range of particle physics
scenarios. We use {\tt CosmoTherm} to compute the SD signals, including effects
on the ionization history and opacities of the Universe. We also consider the
effect of blackbody-induced stimulated decay, which can modify the injection
history significantly. Then, we use data from COBE/FIRAS and EDGES to constrain
the properties of the decaying particles. We explore scenarios where these
provide a dark matter (DM) candidate or constitute only a small fraction of DM.
We complement the SD constraints with CMB anisotropy constraints, highlighting
new effects from injections at very-low photon energies ($h\nu\lesssim
10^{-4}\,\mathrm{eV}$). Our model-independent constraints exhibit rich
structures in the lifetime-energy domain, covering injection energies
$E_\mathrm{inj}\simeq 10^{-10}\mathrm{eV}-10\mathrm{keV}$ and lifetimes
$\tau_X\simeq 10^5\,\mathrm{s}-10^{33}\mathrm{s}$. We discuss the constraints
on axions and axion-like particles that convert directly into two photons,
revising existing SD constraints in the literature. Our limits are competitive
with other constraints for axion masses $m_a c^2\gtrsim 27\,\mathrm{eV}$ and we
find that simple estimates based on the overall energetics are generally
inaccurate. Future CMB spectrometers could significantly improve the obtained
constraints, thus providing an important complementary probe of early-universe
particle physics. | Gaussian Process Foreground Subtraction and Power Spectrum Estimation
for 21 cm Cosmology: One of the primary challenges in enabling the scientific potential of 21 cm
intensity mapping at the Epoch of Reionization (EoR) is the separation of
astrophysical foreground contamination. Recent works have claimed that Gaussian
process regression (GPR) can robustly perform this separation, particularly at
low Fourier $k$ wavenumbers where the signal reaches its peak signal-to-noise
ratio. We revisit this topic by casting GPR foreground subtraction (GPR-FS)
into the quadratic estimator formalism, thereby putting its statistical
properties on stronger theoretical footing. We find that GPR-FS can distort the
window functions at these low k modes, which, without proper decorrelation,
make it difficult to probe the EoR power spectrum. Incidentally, we also show
that GPR-FS is in fact closely related to the widely studied optimal quadratic
estimator. As a case study, we look at recent power spectrum upper limits from
the Low Frequency Array (LOFAR) that utilized GPR-FS. We pay close attention to
their normalization scheme, showing that it is particularly sensitive to signal
loss when the EoR covariance is misestimated. This implies possible
ramifications for recent astrophysical interpretations of the LOFAR limits,
because many of the EoR models ruled out do not fall within the bounds of the
covariance models explored by LOFAR. Being more robust to this bias (although
not entirely free of it), we conclude that the quadratic estimator is a more
natural framework for implementing GPR-FS and computing the 21 cm power
spectrum. |
INTEGRAL and Swift/XRT observations of the source PKS 0208-512: The active galaxy PKS 0208-512, detected at lower energies by COMPTEL, has
been claimed to be a MeV blazar from EGRET. We report on the most recent
INTEGRAL observations of the blazar PKS 0208-512, which are supplemented by
Swift ToO observations. The high energy X-ray and gamma-ray emission of PKS
0208-512 during August - December 2008 has been studied using 682 ks of
INTEGRAL guest observer time and ~ 56 ks of Swift/XRT observations. These data
were collected during the decay of a gamma-ray flare observed by Fermi/LAT. At
X-ray energies (0.2 - 10 keV) PKS 0208-512 is significantly detected by
Swift/XRT, showing a power-law spectrum with a photon index of ~ 1.64. Its
X-ray luminosity varied by roughly 30% during one month. At hard X-/soft
gamma-ray energies PKS 0208-512 shows a marginally significant (~ 3.2 sigma)
emission in the 0.5-1 MeV band when combining all INTEGRAL/SPI data.
Non-detections at energies below and above this band by INTEGRAL/SPI may
indicate intrinsic excess emission. If this possible excess is produced by the
blazar, one possible explanation could be that its jet consists of an abundant
electron-positron plasma, which may lead to the emission of an annihilation
radiation feature. Assuming this scenario, we estimate physical parameters of
the jet of PKS 0208-512. | The 2024 BBN baryon abundance update: We revisit the state of the light element abundances from big bang
nucleosynthesis in early 2024 with particular focus on the derived baryon
abundance. We find that the largest differences between the final baryon
abundances are typically driven by the assumed Deuterium burning rates,
characterized in this work by the underlying code. The rates from theoretical
ab-initio calculations favor smaller baryon abundances, while
experimentally-determined rates prefer higher abundances. Through robust
marginalization over a wide range of nuclear rates, the recently released
$\mathtt{PRyMordial}$ code allows for a conservative estimate of the baryon
abundance at $\Omega_b h^2 = 0.02218 \pm 0.00055$ (using PDG-recommended light
element abundances) in $\Lambda$CDM and $\Omega_b h^2 = 0.02196 \pm 0.00063$
when additional ultra-relativistic relics are considered ($\Lambda$CDM +
$N_\mathrm{eff}$). These additional relics themselves are constrained to
$\Delta N_\mathrm{eff} = -0.10 \pm 0.21$ by light element abundances alone. |
SMA/PdBI multiple line observations of the nearby Seyfert2 galaxy NGC
1068: Shock related gas kinematics and heating in the central 100pc?: We present high angular resolution (0.5-2.0") observations of the mm
continuum and the 12CO(J=3-2), 13CO(J=3-2), 13CO(J=2-1), C18O(J=2-1),
HCN(J=3-2), HCO+(J=4-3) and HCO+(J=3-2) line emission in the circumnuclear disk
(r=100pc) of the proto-typical Seyfert type-2 galaxy NGC1068, carried out with
the Submillimeter Array. We further include in our analysis new 13CO(J=1-0) and
improved 12CO(J=2-1) observations of NGC1068 at high angular resolution
(1.0-2.0") and sensitivity, conducted with the IRAM Plateau de Bure
Interferometer. Based on the complex dynamics of the molecular gas emission
indicating non-circular motions in the central ~100pc, we propose a scenario in
which part of the molecular gas in the circumnuclear disk of NGC1068 is
radially blown outwards as a result of shocks. This shock scenario is further
supported by quite warm (Tkin>=200K) and dense (nH2=10^4cm^-3) gas constrained
from the observed molecular line ratios. The HCN abundance in the circumnuclear
disk is found to be [HCN]/[12CO]=10^-3.5. This is slightly higher than the
abundances derived for galactic and extragalactic starforming/starbursting
regions. This results lends further support to X-ray enhanced HCN formation in
the circumnuclear disk of NGC1068, as suggested by earlier studies. The HCO+
abundance ([HCO+]/[12CO]=10^-5) appears to be somewhat lower than that of
galactic and extragalactic starforming/starbursting regions. When trying to fit
the cm to mm continuum emission by different thermal and non-thermal processes,
it appears that electron-scattered synchrotron emission yields the best results
while thermal free-free emission seems to over-predict the mm continuum
emission. | Temperature and Entropy Profiles to the Virial Radius of Abell 1246
Cluster Observed with Suzaku: We report properties of the intracluster medium (ICM) in Abell~1246 to the
virial radius ($r_{200}$) and further outside as observed with Suzaku. The ICM
emission is clearly detected to $r_{200}$, and we derive profiles of electron
temperature, density, entropy, and cluster mass based on the spectral analysis.
The temperature shows variation from $\sim 7$ keV at the central region to
$\sim 2.5$ keV around $r_{200}$. The total mass in $r_{500}$ is $(4.3 \pm 0.4)
\times 10^{14}~M_{\odot}$, assuming hydrostatic equilibrium. At $r>r_{500}$,
the hydrostatic mass starts to decline and we, therefore, employ the total mass
within $r_{200}$ based on weak-lens mass profile obtained from a sample of
lower mass clusters. This yields the gas mass fraction at $r_{200}$ consistent
with the cosmic baryon fraction, i.e. $\sim 17$%. The entropy profile indicates
a flatter slope than that of the numerical simulation, particularly in
$r>r_{500}$. These tendencies are similar to those of other clusters observed
with Suzaku. We detect no significant ICM emission outside of $r_{200}$, and
$2\sigma$ upper limits of redshifted OVII and OVIII line intensities are
constrained to be less than 2.9 and $5.6\times 10^{-7}$ photons cm$^{-2}$
s$^{-1}$ arcmin$^{-2}$, respectively. The OVII line upper limit indicates
$n_{\rm H}< 4.7\times 10^{-5}$ cm$^{-3}$ ($Z/0.2~Z_{\odot}$)$^{-1/2}$
($L/20~{\rm Mpc}$)$^{-1/2}$, which corresponds to an overdensity, $\delta<160$
($Z/0.2~Z_{\odot}$)$^{-1/2}$ ($L/20~{\rm Mpc}$)$^{-1/2}$. |
Constraining f(R) theories with cosmography: A method to set constraints on the parameters of extended theories of
gravitation is presented. It is based on the comparison of two series
expansions of any observable that depends on H(z). The first expansion is of
the cosmographical type, while the second uses the dependence of H with z
furnished by a given type of extended theory. When applied to f(R) theories
together with the redshift drift, the method yields limits on the parameters of
two examples (the theory of Hu and Sawicki (2007), and the exponential gravity
introduced by Linder (2009)) that are compatible with or more stringent than
the existing ones, as well as a limit for a previously unconstrained parameter. | Mass-metallicity relation from z=5 to the present: Evidence for a
transition in the mode of galaxy growth at z=2.6 due to the end of sustained
primordial gas infall: We analyze the redshift evolution of the mass-metallicity relation in a
sample of 110 Damped Ly$\alpha$ absorbers spanning the redshift range
$z=0.11-5.06$ and find that the zero-point of the correlation changes
significantly with redshift. The evolution is such that the zero-point is
constant at the early phases of galaxy growth (i.e. no evolution) but then
features a sharp break at $z=2.6\pm 0.2$ with a rapid incline towards lower
redshifts such that damped absorbers of identical masses are more metal rich at
later times than earlier. The slope of this mass metallicity correlation
evolution is $0.35 \pm 0.07$ dex per unit redshift.
We compare this result to similar studies of the redshift evolution of
emission selected galaxy samples and find a remarkable agreement with the slope
of the evolution of galaxies of stellar mass log$(M_{*}/M_\odot) \approx 8.5$.
This allows us to form an observational tie between damped absorbers and
galaxies seen in emission.
We use results from simulations to infer the virial mass of the dark matter
halo of a typical DLA galaxy and find a ratio $(M_{vir}/M_{*}) \approx 30$.
We compare our results to those of several other studies that have reported
strong transition-like events at redshifts around $z=2.5-2.6$ and argue that
all those observations can be understood as the consequence of a transition
from a situation where galaxies were fed more unprocessed infalling gas than
they could easily consume to one where they suddenly become infall starved and
turn to mainly processing, or re-processing, of previously acquired gas. |
A new measurement of the Hubble constant and matter content of the
Universe using extragalactic background light $γ$-ray attenuation: The Hubble constant $H_{0}$ and matter density $\Omega_{m}$ of the Universe
are measured using the latest $\gamma$-ray attenuation results from Fermi-LAT
and Cherenkov telescopes. This methodology is based upon the fact that the
extragalactic background light supplies opacity for very high energy photons
via photon-photon interaction. The amount of $\gamma$-ray attenuation along the
line of sight depends on the expansion rate and matter content of the Universe.
This novel strategy results in a value of
$H_{0}=67.4_{-6.2}^{+6.0}$~km~s$^{-1}$~Mpc$^{-1}$ and
$\Omega_{m}=0.14_{-0.07}^{+0.06}$. These estimates are independent and
complementary to those based on the distance ladder, cosmic microwave
background (CMB), clustering with weak lensing, and strong lensing data. We
also produce a joint likelihood analysis of our results from $\gamma$ rays and
these from more mature methodologies, excluding the CMB, yielding a combined
value of $H_{0}=66.6\pm 1.6$~km~s$^{-1}$~Mpc$^{-1}$ and $\Omega_{m}=0.29\pm
0.02$. | Non-Gaussian errors of baryonic acoustic oscillations: We revisit the uncertainty in baryon acoustic oscillation (BAO) forecasts and
data analyses. In particular, we study how much the uncertainties on both the
measured mean dilation scale and the associated error bar are affected by the
non-Gaussianity of the non-linear density field. We examine two possible
impacts of non-Gaussian analysis: (1) we derive the distance estimators from
Gaussian theory, but use 1000 N-Body simulations to measure the actual errors,
and compare this to the Gaussian prediction, and (2) we compute new optimal
estimators, which requires the inverse of the non-Gaussian covariance matrix of
the matter power spectrum. Obtaining an accurate and precise inversion is
challenging, and we opted for a noise reduction technique applied on the
covariance matrices. By measuring the bootstrap error on the inverted matrix,
this work quantifies for the first time the significance of the non-Gaussian
error corrections on the BAO dilation scale. We find that the variance (error
squared) on distance measurements can deviate by up to 12% between both
estimators, an effect that requires a large number of simulations to be
resolved. We next apply a reconstruction algorithm to recover some of the BAO
signal that had been smeared by non-linear evolution, and we rerun the
analysis. We find that after reconstruction, the rms error on the distance
measurement improves by a factor of ~1.7 at low redshift (consistent with
previous results), and the variance ({\sigma}^2) shows a change of up to 18%
between optimal and sub-optimal cases (note, however, that these discrepancies
may depend in detail on the procedure used to isolate the BAO signal). We
finally discuss the impact of this work on current data analyses. |
The Local Environments of Core-Collapse SNe within Host Galaxies: We present constraints on core-collapse supernova progenitors through
observations of their environments within host galaxies. This is achieved
through 2 routes. Firstly, we investigate the spatial correlation of supernovae
with host galaxy star formation using pixel statistics. We find that the main
supernova types form a sequence of increasing association to star formation.
The most logical interpretation is that this implies an increasing progenitor
mass sequence going from the supernova type Ia arising from the lowest mass,
through the type II, type Ib, and the supernova type Ic arising from the
highest mass progenitors. We find the surprising result that the supernova type
IIn show a lower association to star formation than type IIPs, implying lower
mass progenitors. Secondly, we use host HII region spectroscopy to investigate
differences in environment metallicity between different core-collapse types.
We find that supernovae of types Ibc arise in slightly higher metallicity
environments than type II events. However, this difference is not significant,
implying that progenitor metallicity does not play a dominant role in deciding
supernova type. | Counter-dispersed slitless-spectroscopy technique: planetary nebula
velocities in the halo of NGC 1399: Using a counter-dispersed slitless spectroscopy technique, we detect and
measure the line-of-sight velocities of 187 planetary nebulae (PNe) around one
of the nearest cD galaxies, NGC 1399, with FORS1 on the VLT. We describe the
method for identifying and classifying the emission-line sources and the
procedure for computing their J2000 coordinates and velocities. The number of
PN detections and the errors in the velocity measurements (37 km/s indicate
that this technique is comparable to other methods, such as that described by
Teodorescu et al. (2005). We present the spatial distribution of the PNe and a
basic analysis of their velocities. The PN two-dimensional velocity field shows
marginal rotation consistent with other studies. We also find a low-velocity
substructure in the halo and a flatter velocity-dispersion profile compared to
previous observations that extends to ~400 arcsec. The detection of a
low-velocity subcomponent underscores the importance of discrete velocity
tracers for the detection of un-mixed components. The new velocity-dispersion
profile is in good agreement with revised velocity dispersions for the red
globular clusters in NGC 1399, using the data of Schuberth et al. (2009). The
outer parts of this profile are consistent with one of the dynamical models of
Kronawitter et al. (2000), which corresponds to a circular velocity of ~340
km/s and a rescaled B-band mass-to-light ratio of ~20 at 7' radius. These
measurements trace the kinematics of the outer halo and disentangle the
heterogenous populations in the Fornax Cluster core. The new data set the stage
for a revised dynamical model of the outer halo of NGC 1399. |
Anisotropic Lyman-alpha Emission: As a result of resonant scatterings off hydrogen atoms, Lyman-alpha (Lya)
emission from star-forming galaxies provides a probe of the (hardly isotropic)
neutral gas environment around them. We study the effect of the environmental
anisotropy on the observed Lya emission by performing radiative transfer
calculations for models of neutral hydrogen clouds with prescriptions of
spatial and kinematic anisotropies. The environmental anisotropy leads to
corresponding anisotropy in the Lya flux and spectral properties and induces
correlations among them. The Lya flux (or observed luminosity) depends on the
viewing angle and shows an approximate correlation with the initial Lya optical
depth in the viewing direction relative to those in all other directions. The
distribution of Lya flux from a set of randomly oriented clouds is skewed to
high values, providing a natural contribution to the Lya equivalent width (EW)
distribution seen in observation. A narrower EW distribution is found at a
larger peak offset of the Lya line, similar to the trend suggested in
observation. The peak offset appears to correlate with the line shape (full
width at half maximum and asymmetry), pointing to a possibility of using Lya
line features alone to determine the systemic redshifts of galaxies. The study
suggests that anisotropies in the spatial and kinematic distributions of
neutral hydrogen can be an important ingredient in shaping the observed
properties of Lya emission from star-forming galaxies. We discuss the
implications of using Lya emission to probe the circumgalactic and
intergalactic environments of galaxies. | Constraining star formation rates in cool-core brightest cluster
galaxies: We used broad-band imaging data for 10 cool-core brightest cluster galaxies
(BCGs) and conducted a Bayesian analysis using stellar population synthesis to
determine the likely properties of the constituent stellar populations.
Determination of ongoing star formation rates (SFRs), in particular, has a
direct impact on our understanding of the cooling of the intracluster medium
(ICM), star formation and AGN-regulated feedback. Our model consists of an old
stellar population and a series of young stellar components. We calculated
marginalized posterior probability distributions for various model parameters
and obtained 68% plausible intervals from them. The 68% plausible interval on
the SFRs is broad, owing to a wide range of models that are capable of fitting
the data, which also explains the wide dispersion in the star formation rates
available in the literature. The ranges of possible SFRs are robust and
highlight the strength in such a Bayesian analysis. The SFRs are correlated
with the X-ray mass deposition rates (the former are factors of 4 to 50 lower
than the latter), implying a picture where the cooling of the ICM is a
contributing factor to star formation in cool-core BCGs. We find that 9 out of
10 BCGs have been experiencing starbursts since 6 Gyr ago. While four out of 9
BCGs seem to require continuous SFRs, 5 out of 9 seem to require periodic star
formation on intervals ranging from 20 Myr to 200 Myr. This time scale is
similar to the cooling-time of the ICM in the central (< 5 kpc) regions. |
Revisiting small-scale fluctuations in $α$-attractor models of
inflation: Cosmological $\alpha$-attractors stand out as particularly compelling models
to describe inflation in the very early universe, naturally meeting tight
observational bounds from cosmic microwave background (CMB) experiments. We
investigate $\alpha$-attractor potentials in the presence of an inflection
point, leading to enhanced curvature perturbations on small scales. We study
both single- and multi-field models, driven by scalar fields living on a
hyperbolic field space. In the single-field case, ultra-slow-roll dynamics at
the inflection point is responsible for the growth of the power spectrum, while
in the multi-field set-up we study the effect of geometrical destabilisation
and non geodesic motion in field space. The two mechanisms can in principle be
distinguished through the spectral shape of the resulting scalar power spectrum
on small scales. These enhanced scalar perturbations can lead to primordial
black hole (PBH) production and second-order gravitational wave (GW)
generation. Due to the existence of universal predictions in
$\alpha$-attractors, consistency with current CMB constraints on the
large-scale spectral tilt implies that PBHs can only be produced with masses
smaller than $10^8\,\text{g}$ and are accompanied by ultra-high frequency GWs,
with a peak expected to be at frequencies of order $10\,\text{kHz}$ or above. | Confirming the Detection of two WHIM Systems along the Line of Sight to
1ES 1553+113: We present a re-analysis, with newly acquired atomic data, of the two
detections of two highly ionized intervening OVII absorbers reported by
Nicastro and collaborators (2018). We confirm both intervening Warm-Hot
Intergalactic Medium OVII detections, and revise statistical significance and
physical parameters of the absorber at $z=0.4339$ in light of its partial
contamination by Galactic interstellar medium NII K$\alpha$ absorption. |
Interacting Viscous Dark Energy in Bianchi Type-I Universe: A solution to the coincidence and Big Rip problems on the bases of an
anisotropic space-time is proposed. To do so, we study the interaction between
viscous dark energy and dark matter in the scope of the Bianchi type-I
Universe. We parameterize the viscosity and the interaction between the two
fluids by constants $\zeta_{0}$ and $\sigma$ respectively. A detailed
investigation on the cosmological implications of this parametrization has been
made. We have also performed a geometrical diagnostic by using the statefinder
pairs $\{s, r\}$ and $\{q, r\}$ in order to differentiate between different
dark energy models. Moreover, we fit the coupling parameter $\sigma$ as well as
the Hubble's parameter $H_{0}$ of our model by minimizing the $\chi^{2}$
through the age differential method, involving a direct measurement of $H$. | Generating $\fnl$ at $\ell\lsim 60$: The CMB anisotropy at $\ell\lsim 60$ seems to have some special features
which include (i) a dipole modulation and (ii) a decrease in power. It is known
that both of these effects can be generated if a curvaton-type field has a
super-horizon perturbation.
It is also known that this will generate non-gaussianity $\fnl$ in the same
range of $\ell$, whose magnitude has a lower bound coming from the magnitude of
the observed CMB quadrupole. I revisit that bound in the present paper, and
point out that it may or may not be compatible with current data which should
therefore be re-analysed. |
Do baryons trace dark matter in the early universe?: Baryon-density perturbations of large amplitude may exist if they are
compensated by dark-matter perturbations so that the total density remains
unchanged. Big-bang nucleosynthesis and galaxy clusters allow the amplitudes of
these compensated isocurvature perturbations (CIPs) to be as large as
$\sim10%$. CIPs will modulate the power spectrum of cosmic microwave background
(CMB) fluctuations---those due to the usual adiabatic perturbations---as a
function of position on the sky. This leads to correlations between different
spherical-harmonic coefficients of the temperature/polarization map, and it
induces B modes in the CMB polarization. Here, the magnitude of these effects
is calculated and techniques to measure them are introduced. While a CIP of
this amplitude can be probed on the largest scales with WMAP, forthcoming CMB
experiments should improve the sensitivity to CIPs by at least an order of
magnitude. | Phantom boundary crossing and anomalous growth index of fluctuations in
viable f(R) models of cosmic acceleration: Evolution of a background space-time metric and sub-horizon matter density
perturbations in the Universe is numerically analyzed in viable $f(R)$ models
of present dark energy and cosmic acceleration. It is found that viable models
generically exhibit recent crossing of the phantom boundary $w_{\rm DE}=-1$.
Furthermore, it is shown that, as a consequence of the anomalous growth of
density perturbations during the end of the matter-dominated stage, their
growth index evolves non-monotonically with time and may even become negative
temporarily. |
A Matched Catalogue of z> 5.9 Galaxies in the WFC3 Hubble Ultra Deep
Field: There have been several independent analyses of the recent Wide Field Camera
3 images of the Hubble Deep Field, selecting galaxies at z>6 through the Lyman
break technique. Presented here is a matched catalogue of objects in common
between the analyses posted to this preprint server, listing the different
catalogue names associated with the same sources. | Axion Dark Matter and Cosmological Parameters: We observe that photon cooling after big bang nucleosynthesis (BBN) but
before recombination can remove the conflict between the observed and
theoretically predicted value of the primordial abundance of $^7$Li. Such
cooling is ordinarily difficult to achieve. However, the recent realization
that dark matter axions form a Bose-Einstein condensate (BEC) provides a
possible mechanism, because the much colder axions may reach thermal contact
with the photons. This proposal predicts a high effective number of neutrinos
as measured by the cosmic microwave anisotropy spectrum. |
Bayesian cosmological inference through implicit cross-correlation
statistics: Analyzes of next-generation galaxy data require accurate treatment of
systematic effects such as the bias between observed galaxies and the
underlying matter density field. However, proposed models of the phenomenon are
either numerically expensive or too inaccurate to achieve unbiased inferences
of cosmological parameters even at mildly-nonlinear scales of the data. As an
alternative to constructing accurate galaxy bias models, requiring
understanding galaxy formation, we propose to construct likelihood
distributions for Bayesian forward modeling approaches that are insensitive to
linear, scale-dependent bias and provide robustness against model
misspecification. We use maximum entropy arguments to construct likelihood
distributions designed to account only for correlations between data and
inferred quantities. By design these correlations are insensitive to linear
galaxy biasing relations, providing the desired robustness. The method is
implemented and tested within a Markov Chain Monte Carlo approach. The method
is assessed using a halo mock catalog based on standard full, cosmological,
N-body simulations. We obtain unbiased and tight constraints on cosmological
parameters exploiting only linear cross-correlation rates for $k\le 0.10$
Mpc/h. Tests for halos of masses ~10$^{12}$ M$_\odot$ to ~10$^{13}$ M$_\odot$
indicate that it is possible to ignore all details of the linear, scale
dependent, bias function while obtaining robust constraints on cosmology. Our
results provide a promising path forward to analyzes of galaxy surveys without
the requirement of having to accurately model the details of galaxy biasing but
by designing robust likelihoods for the inference. | Hubble tension or a transition of the Cepheid SnIa calibrator
parameters?: We re-analyze the Cepheid data used to infer the value of $H_0$ by
calibrating SnIa. We do not enforce a universal value of the empirical Cepheid
calibration parameters $R_W$ (Cepheid Wesenheit color-luminosity parameter) and
$M_H^{W}$ (Cepheid Wesenheit H-band absolute magnitude). Instead, we allow for
variation of either of these parameters for each individual galaxy. We also
consider the case where these parameters have two universal values: one for low
galactic distances $D<D_c$ and one for high galactic distances $D>D_c$ where
$D_c$ is a critical transition distance. We find hints for a $3\sigma$ level
mismatch between the low and high galactic distance parameter values. We then
use AIC and BIC criteria to compare and rank the following types of models:
Base models: Universal values for $R_W$ and $M_H^{W}$ (no parameter variation),
I Individual fitted galactic $R_W$ with a universal fitted $M_H^{W}$, II
Universal fixed $R_W$ with individual fitted galactic $M_H^{W}$, III Universal
fitted $R_W$ with individual fitted galactic $M_H^{W}$, IV Two universal fitted
$R_W$ (near and far) with one universal fitted $M_H^{W}$, V Universal fitted
$R_W$ with two universal fitted $M_H^{W}$ (near and far), VI Two universal
fitted $R_W$ with two universal fitted $M_H^{W}$ (near and far). We find that
the AIC and BIC criteria consistently favor model IV instead of the commonly
used Base model where no variation is allowed for the Cepheid empirical
parameters. The best fit value of the SnIa absolute magnitude $M_B$ and of
$H_0$ implied by the favored model IV is consistent with the inverse distance
ladder calibration based on the CMB sound horizon $H_0=67.4\pm
0.5\,km\,s^{-1}\,Mpc^{-1}$. Thus in the context of the favored model IV the
Hubble crisis is not present. This model may imply the presence of a
fundamental physics transition taking place at a time more recent than
$100\,Myrs$ ago. |
Rings and bars: unmasking secular evolution of galaxies: Secular evolution gradually shapes galaxies by internal processes, in
contrast to early cosmological evolution which is more rapid. An important
driver of secular evolution is the flow of gas from the disk into the central
regions, often under the influence of a bar. In this paper, we review several
new observational results on bars and nuclear rings in galaxies. They show that
these components are intimately linked to each other, and to the properties of
their host galaxy. We briefly discuss how upcoming observations, e.g., imaging
from the Spitzer Survey of Stellar Structure in Galaxies (S4G), will lead to
significant further advances in this area of research. | Testing the anisotropy of the universe using the simulated gravitational
wave events from advanced LIGO and Virgo: The detection of gravitational waves (GWs) provides a powerful tool to
constrain the cosmological parameters. In this paper, we investigate the
possibility of using GWs as standard sirens in testing the anisotropy of the
universe. We consider the GW signals produced by the coalescence of binary
black hole systems and simulate hundreds of GW events from the advanced Laser
Interferometer Gravitational-Wave Observatory (LIGO) and Virgo. It is found
that the anisotropy of the universe can be tightly constrained if the redshift
of the GW source is precisely known. The anisotropic amplitude can be
constrained with an accuracy comparable to the Union2.1 complication of type-Ia
supernovae if $\gtrsim 400$ GW events are observed. As for the preferred
direction, $\gtrsim 800$ GW events are needed in order to achieve the accuracy
of Union2.1. With 800 GW events, the probability of pseudo anisotropic signals
with an amplitude comparable to Union2.1 is negligible. These results show that
GWs can provide a complementary tool to supernovae in testing the anisotropy of
the universe. |
Big Bang Nucleosynthesis: 2015: Big-bang nucleosynthesis (BBN) describes the production of the lightest
nuclides via a dynamic interplay among the four fundamental forces during the
first seconds of cosmic time. We briefly overview the essentials of this
physics, and present new calculations of light element abundances through li6
and li7, with updated nuclear reactions and uncertainties including those in
the neutron lifetime. We provide fits to these results as a function of baryon
density and of the number of neutrino flavors, N_nu. We review recent
developments in BBN, particularly new, precision Planck cosmic microwave
background (CMB) measurements that now probe the baryon density, helium
content, and the effective number of degrees of freedom, n_eff. These
measurements allow for a tight test of BBN and of cosmology using CMB data
alone. Our likelihood analysis convolves the 2015 Planck data chains with our
BBN output and observational data. Adding astronomical measurements of light
elements strengthens the power of BBN. We include a new determination of the
primordial helium abundance in our likelihood analysis. New D/H observations
are now more precise than the corresponding theoretical predictions, and are
consistent with the Standard Model and the Planck baryon density. Moreover, D/H
now provides a tight measurement of N_nu when combined with the CMB baryon
density, and provides a 2sigma upper limit N_nu < 3.2. The new precision of the
CMB and of D/H observations together leave D/H predictions as the largest
source of uncertainties. Future improvement in BBN calculations will therefore
rely on improved nuclear cross section data. In contrast with D/H and he4, li7
predictions continue to disagree with observations, perhaps pointing to new
physics. | The Origin of Intergalactic Light in Compact Groups of Galaxies: We investigate the origin of intergalactic light (IGL) in close groups of
galaxies. IGL is hypothesized to be the byproduct of interaction and merger
within compact groups. Comparing the X-ray point source population in our
sample of compact groups that have intergalactic light with compact groups
without IGL, we find marginal evidence for a small increase in ultra-luminous
X-ray sources (ULXs). There is also a significant bias towards lower luminosity
high mass X-ray binaries (HMXRBs). We interpret this as an indication that
groups with visible IGL represent a later evolutionary phase than other compact
groups. They have galaxies characterized by quenching of star formation (lower
star formation rate (SFR) inferred from lower HMXRB luminosity) after stellar
material has been removed from the galaxies into the intergalactic medium,
which is the source of the IGL. We conclude that the presence of an increased
fraction of ULXs is due to past interaction and mergers within groups that have
IGL. |
PRISM: Sparse recovery of the primordial spectrum from WMAP9 and Planck
datasets: The primordial power spectrum is an indirect probe of inflation or other
structure-formation mechanisms. We introduce a new method, named
\textbf{PRISM}, to estimate this spectrum from the empirical cosmic microwave
background (CMB) power spectrum. This is a sparsity-based inversion method,
which leverages a sparsity prior on features in the primordial spectrum in a
wavelet dictionary to regularise the inverse problem. This non-parametric
approach is able to reconstruct the global shape as well as localised features
of spectrum accurately and proves to be robust for detecting deviations from
the currently favoured scale-invariant spectrum. We investigate the strength of
this method on a set of WMAP nine-year simulated data for three types of
primordial spectra and then process the WMAP nine-year data as well as the
Planck PR1 data. We find no significant departures from a near scale-invariant
spectrum. | Discrimination between Lambda-CDM, quintessence, and modified gravity
models using wide area surveys: In the past decade or so observations of supernovae, Large Scale Structures
(LSS), and the Cosmic Microwave Background (CMB) have confirmed the presence of
what is called dark energy - the cause of accelerating expansion of the
Universe. They have also measured its density as well as the value of other
cosmological parameters according to the concordance $\Lambda$CDM model with
few percent uncertainties. Next generation of surveys should allow to constrain
this model with better precisions, or distinguish between a LCDM and
alternative models such as modified gravity and (interacting)-quintessence
models. In this work we parametrize both homogeneous and anisotropic components
of matter density in the context of interacting dark energy models with the
goal of discriminating between f(R) modified gravity and its generalizations,
and interacting dark energy models, for which we also propose a
phenomenological description of energy-momentum conservation equations inspired
by particle physics. It is based on the fact that the simplest interactions
between particles/fields are elastic scattering and decay. The parametrization
of growth rate proposed here is nonetheless general and can be used to
constrain other interactions. As an example of applications, we present an
order of magnitude estimation of the accuracy of the measurement of these
parameters using Euclid and Planck surveys data, and leave a better estimation
to a dedicated work. |
A deep look at the inner regions of the mini-BAL QSO PG 1126-041 with
XMM-Newton: A long XMM-Newton observation of the mini-BAL QSO PG 1126-041 allowed us to
detect a highly ionized phase of X-ray absorbing gas outflowing at v~15000
km/s. Physical implications are briefly discussed. | The $f(R)$ halo mass function in the cosmic web: An important indicator of modified gravity is the effect of the local
environment on halo properties. This paper examines the influence of the local
tidal structure on the halo mass function, the halo orientation, spin and the
concentration-mass relation. We generalise the excursion set formalism to
produce a halo mass function conditional on large-scale structure. Our model
agrees well with simulations on large scales at which the density field is
linear or weakly non-linear. Beyond this, our principal result is that $f(R)$
does affect halo abundances, the halo spin parameter and the concentration-mass
relationship in an environment-independent way, whereas we find no appreciable
deviation from $\Lambda$CDM for the mass function with fixed environment
density, nor the alignment of the orientation and spin vectors of the halo to
the eigenvectors of the local cosmic web. There is a general trend for greater
deviation from $\Lambda$CDM in underdense environments and for high-mass
haloes, as expected from chameleon screening. |
Calibrating the BAO scale using the CMB: Lifting the degeneracy between
geometric and dynamic distortions using the sound horizon from the CMB: The degeneracy between geometric (Alcock-Paczynski) and dynamic (redshift
space) distortions in the pattern of the galaxy distribution has been a long
standing problem in the study of the large scale structure of the universe. We
examine the possibility of lifting this degeneracy and constraining
cosmological parameters by using the Baryon Acoustic Oscillation (BAO) scale as
a feature of known physical size, the sound horizon r_s ~ 150 Mpc. We
callibrate this scale with the equivalent feature in the Cosmic Microwave
Background (CMB). First, we construct a toy model of a power spectrum which
includes the BAO as well as geometric and dynamic distortions. By adding a
prior onto the sound horizon of ~1% we show, using a Fisher matrix analysis,
that error ellipses for line of sight and tangential distortion parameters
shrink by a factor of two for a 20(Gpc/h)^3 `DESpec/BigBOSS'-like galaxy survey
including shot noise. This improvement is even more marked in smaller surveys.
We also carry out a Monte Carlo Nested Sampling analysis on our parameter
space. We find that Monte Carlo and Fisher methods can agree reasonably well
for surveys with large volume but differ greatly for small volume surveys. | Magnetic Inelastic Dark Matter: Directional Signals Without a
Directional Detector: The magnetic inelastic dark matter (MiDM) model, in which dark matter
inelastically scatters off nuclei through a magnetic dipole interaction, has
previously been shown to reconcile the DAMA/LIBRA annual modulation signal with
null results from other experiments. In this work, we explore the unique
directional detection signature of MiDM. After the dark matter scatters into
its excited state, it decays with a lifetime of order 1 microsecond and emits a
photon with energy ~100 keV. Both the nuclear recoil and the corresponding
emitted photon can be detected by studying delayed coincidence events. The
recoil track and velocity of the excited state can be reconstructed from the
nuclear interaction vertex and the photon decay vertex. The angular
distribution of the WIMP recoil tracks is sharply peaked and modulates daily.
It is therefore possible to observe the directional modulation of WIMP-nucleon
scattering without a large-volume gaseous directional detection experiment.
Furthermore, current experiments such as XENON100 can immediately measure this
directional modulation and constrain the MiDM parameter space with an exposure
of a few thousand kg day. |
Measurement of the Anisotropy Power Spectrum of the Radio Synchrotron
Background: We present the first targeted measurement of the power spectrum of
anisotropies of the radio synchrotron background, at 140 MHz where it is the
overwhelmingly dominant photon background. This measurement is important for
understanding the background level of radio sky brightness, which is dominated
by steep-spectrum synchrotron radiation at frequencies below 0.5 GHz and has
been measured to be significantly higher than that which can be produced by
known classes of extragalactic sources and most models of Galactic halo
emission. We determine the anisotropy power spectrum on scales ranging from 2
degrees to 0.2 arcminutes with LOFAR observations of two 18 square degree
fields -- one centered on the Northern hemisphere coldest patch of radio sky
where the Galactic contribution is smallest and one offset from that location
by 15 degrees. We find that the anisotropy power is higher than that
attributable to the distribution of point sources above 100 micro-Jy in flux.
This level of radio anisotropy power indicates that if it results from point
sources, those sources are likely at low fluxes and incredibly numerous, and
likely clustered in a specific manner. | Blueshifted galaxies in the Virgo Cluster: We examine a sample of 65 galaxies in the Virgo cluster with negative radial
velocities relative to the Local Group. Some features of this sample are
pointed out. All of these objects are positioned compactly within a virial zone
of radius 6{\deg} in the cluster, but their centroid is displaced relative to
the dynamic center of the cluster, M87, by 1.1{\deg} to the northwest. The
dwarf galaxies in this sample are clumped on a scale of ~10' (50 kpc). The
observed asymmetry in the distribution of the blueshifted galaxies may be
caused by infall of a group of galaxies around M86 onto the main body of the
cluster. We offer another attempt to explain this phenomenon, assuming a mutual
tangential velocity of ~300 km/s between the Local Group and the Virgo cluster
owing to their being repelled from the local cosmological void. |
Gravitational imaging through a triple source plane lens: revisiting the
$Λ$CDM-defying dark subhalo in SDSSJ0946+1006: The $\Lambda$CDM paradigm successfully explains the large-scale structure of
the Universe, but is less well constrained on sub-galactic scales.
Gravitational lens modelling has been used to measure the imprints of dark
substructures on lensed arcs, testing the small-scale predictions of
$\Lambda$CDM. However, the methods required for these tests are subject to
degeneracies among the lens mass model and the source light profile. We present
a case study of the unique compound gravitational lens SDSSJ0946+1006, wherein
a dark, massive substructure has been detected, whose reported high
concentration would be unlikely in a $\Lambda$CDM universe. For the first time,
we model the first two background sources in both I- and U-band HST imaging, as
well as VLT-MUSE emission line data for the most distant source. We recover a
lensing perturber at a $5.9\sigma$ confidence level with mass
$\log_{10}(M_\mathrm{sub}/M_{\odot})=9.2^{+0.4}_{-0.1}$ and concentration
$\log_{10}c=2.4^{+0.5}_{-0.3}$. The concentration is more consistent with CDM
subhalos than previously reported, and the mass is compatible with that of a
dwarf satellite galaxy whose flux is undetectable in the data at the location
of the perturber. A wandering black hole with mass
$\log_{10}(M_\mathrm{BH}/M_{\odot})=8.9^{+0.2}_{-0.1}$ is a viable alternative
model. We systematically investigate alternative assumptions about the
complexity of the mass distribution and source reconstruction; in all cases the
subhalo is detected at around the $\geq5\sigma$ level. However, the detection
significance can be altered substantially (up to $11.3\sigma$) by alternative
choices for the source regularisation scheme. | An Opacity-Free Method of Testing the Cosmic Distance Duality Relation
Using Strongly Lensed Gravitational Wave Signals: The cosmic distance duality relation (CDDR), expressed as DL(z) = (1 +
z)2DA(z), plays an important role in modern cosmology. In this paper, we
propose a new method of testing CDDR using strongly lensed gravitational wave
(SLGW) signals. Under the geometric optics approximation, we calculate the
gravitational lens effects of two lens models, the point mass and singular
isothermal sphere. We use functions of {\eta}1(z) = 1 + {\eta}0z and {\eta}2(z)
= 1 + {\eta}0z=(1 + z) to parameterize the deviation of CDDR. By
reparameterizing the SLGW waveform with CDDR and the distance-redshift
relation, we include the deviation parameters {\eta}0 of CDDR as waveform
parameters. We evaluate the ability of this method by calculating the parameter
estimation of simulated SLGW signals from massive binary black holes. We apply
the Fisher information matrix and Markov Chain Monte Carlo methods to calculate
parameter estimation. We find that with only one SLGW signal, the measurement
precision of {\eta}0 can reach a considerable level of 0.5-1.3% for {\eta}1(z)
and 1.1-2.6% for {\eta}2(z), depending on the lens model and parameters. |
The MUSE Hubble Ultra Deep Field Survey VI: The Faint-End of the Lya
Luminosity Function at 2.91 < z < 6.64 and Implications for Reionisation: We present the deepest study to date of the Lya luminosity function (LF) in a
blank field using blind integral field spectroscopy from MUSE. We constructed a
sample of 604 Lya emitters (LAEs) across the redshift range 2.91 < z < 6.64
using automatic detection software in the Hubble Ultra Deep Field. We calculate
accurate total Lya fluxes capturing low surface brightness extended Lya
emission now known to be a generic property of high-redshift star-forming
galaxies. We simulated realistic extended LAEs to characterise the selection
function of our samples, and performed flux-recovery experiments to test and
correct for bias in our determination of total Lya fluxes. We find an accurate
completeness correction accounting for extended emission reveals a very steep
faint-end slope of the LF, alpha, down to luminosities of log10 L erg s^-1<
41.5, applying both the 1/Vmax and maximum likelihood estimators. Splitting the
sample into three broad redshift bins, we see the faint-end slope increasing
from -2.03+1.42-inf at z ~ 3.44 to -2.86+0.76-inf at z ~ 5.48, however no
strong evolution is seen between the 68% confidence regions in L*-alpha
parameter space. Using the Lya line flux as a proxy for star formation
activity, and integrating the observed LFs, we find that LAEs' contribution to
the cosmic SFRD rises with redshift until it is comparable to that from
continuum-selected samples by z ~ 6. This implies that LAEs may contribute more
to the star-formation activity of the early Universe than previously thought -
any additional interglactic medium correction would act to further boost the
Lya luminosities. Finally, assuming fiducial values for the escape of Lya and
LyC radiation, and the clumpiness of the IGM, we integrated the maximum
likelihood LF at 5.00 < z < 6.64 and find we require only a small extrapolation
beyond the data (< 1 dex in L) for LAEs alone to maintain an ionised IGM at z ~
6. | Simulation of the analysis of interferometric microwave background
polarization data: We present results from an end-to-end simulation pipeline interferometric
observations of cosmic microwave background polarization. We use both
maximum-likelihood and Gibbs sampling techniques to estimate the power
spectrum. In addition, we use Gibbs sampling for image reconstruction from
interferometric visibilities. The results indicate the level to which various
systematic errors (e.g., pointing errors, gain errors, beam shape errors,
cross- polarization) must be controlled in order to successfully detect and
characterize primordial B modes as well as other scientific goals. In addition,
we show that Gibbs sampling is an effective method of image reconstruction for
interferometric data in other astrophysical contexts. |
The redshift dependence of black hole mass distribution: Is it reliable
for standard sirens cosmology?: An upper limit on the mass of a black hole set by the pair-instability
supernovae (PISN) process can be useful in inferring the redshift of the
gravitational wave (GW) sources by lifting the degeneracy between mass and
redshift. However, for this technique to work, it is essential that the PISN
mass-scale is redshift independent or at least has a predictable redshift
dependence. We show that the observed PISN mass-scale can get smeared and the
position of the PISN mass-scale is likely to exhibit a strong redshift
dependence due to a combined effect from the non-zero value of the delay time
between the formation of a star and the merging of two black holes and the
metallicity dependence of PISN mass scale. Due to the unknown form of the
delay-time distribution, the redshift dependence of the PISN mass cut-off of
the binary black holes (BBHs) cannot be well characterized and will exhibit a
large variation with the change in redshift. As a result, the use of a fixed
PISN mass scale to infer the redshift of the BBHs from the observed masses will
be systematically biased. Though this uncertainty is not severe for the third
observation run conducted by the LIGO-Virgo-KAGRA collaboration, in the future
this uncertainty will cause a systematic error in the redshift inferred from
the PISN mass scale. The corresponding systematic error will be a bottleneck in
achieving a few percent precision measurements of the cosmological parameters
using this method in the future. | Unified Dark Matter scalar field models with fast transition: We investigate the general properties of Unified Dark Matter (UDM) scalar
field models with Lagrangians with a non-canonical kinetic term, looking
specifically for models that can produce a fast transition between an early
Einstein-de Sitter CDM-like era and a later Dark Energy like phase, similarly
to the barotropic fluid UDM models in JCAP1001(2010)014. However, while the
background evolution can be very similar in the two cases, the perturbations
are naturally adiabatic in fluid models, while in the scalar field case they
are necessarily non-adiabatic. The new approach to building UDM Lagrangians
proposed here allows to escape the common problem of the fine-tuning of the
parameters which plague many UDM models. We analyse the properties of
perturbations in our model, focusing on the the evolution of the effective
speed of sound and that of the Jeans length. With this insight, we can set
theoretical constraints on the parameters of the model, predicting sufficient
conditions for the model to be viable. An interesting feature of our models is
that what can be interpreted as w_{DE} can be <-1 without violating the null
energy conditions. |
The JCMT Nearby Galaxies Legacy Survey VII: Hα imaging and
massive star formation properties: We present H\alpha{} fluxes, star formation rates (SFRs) and equivalent
widths (EWs) for a sample of 156 nearby galaxies observed in the 12CO J=3-2
line as part of the James Clerk Maxwell Telescope Nearby Galaxies Legacy
Survey. These are derived from images and values in the literature and from new
H\alpha{} images for 72 galaxies which we publish here. We describe the sample,
observations and procedures to extract the H\alpha{} fluxes and related
quantities. We discuss the SFR properties of our sample and confirm the
well-known correlation with galaxy luminosity, albeit with high dispersion. Our
SFRs range from 0.1 to 11 Msun yr-1 with a median SFR value for the complete
sample of 0.2 Msun yr-1. This median values is somewhat lower than similar
published measurements, which we attribute, in part, to our sample being
HI-selected and, thus, not biased towards high SFRs as has frequently been the
case in previous studies. Additionally, we calculate internal absorptions for
the H\alpha{} line, A(H\alpha{}), which are lower than many of those used in
previous studies. Our derived EWs, which range from 1 to 880\AA{} with a median
value of 27\AA{}, show little dependence with luminosity but rise by a factor
of five from early- to late-type galaxies. This paper is the first in a series
aimed at comparing SFRs obtained from H\alpha{} imaging of galaxies with
information derived from other tracers of star formation and atomic and
molecular gas. | Galileon Gravity in Light of ISW, CMB, BAO and $H_0$ data: Cosmological models with Galileon gravity are an alternative to the standard
$\Lambda {\rm CDM}$ paradigm with testable predictions at the level of its
self-accelerating solutions for the expansion history, as well as large-scale
structure formation. Here, we place constraints on the full parameter space of
these models using data from the cosmic microwave background (CMB) (including
lensing), baryonic acoustic oscillations (BAO) and the Integrated Sachs-Wolfe
(ISW) effect. We pay special attention to the ISW effect for which we use the
cross-spectra, $C_\ell^{\rm T g}$, of CMB temperature maps and foreground
galaxies from the WISE survey. The sign of $C_\ell^{\rm T g}$ is set by the
time evolution of the lensing potential in the redshift range of the galaxy
sample: it is positive if the potential decays (like in $\Lambda {\rm CDM}$),
negative if it deepens. We constrain three subsets of Galileon gravity
separately known as the Cubic, Quartic and Quintic Galileons. The cubic
Galileon model predicts a negative $C_\ell^{\rm T g}$ and exhibits a
$7.8\sigma$ tension with the data, which effectively rules it out. For the
quartic and quintic models the ISW data also rule out a significant region of
the parameter space but permit regions where the goodness-of-fit is comparable
to $\Lambda {\rm CDM}$. The data prefers a non zero sum of the neutrino masses
($\sum m_\nu\approx 0.5$eV) with $ \sim \! 5\sigma$ significance in these
models. The best-fitting models have values of $H_0$ consistent with local
determinations, thereby avoiding the tension that exists in $\Lambda {\rm
CDM}$. We also identify and discuss a $\sim \! 2\sigma$ tension that Galileon
gravity exhibits with recent BAO measurements. Our analysis shows overall that
Galileon cosmologies cannot be ruled out by current data but future lensing,
BAO and ISW data hold strong potential to do so. |
Cosmological behavior in extended nonlinear massive gravity: We perform a detailed dynamical analysis of various cosmological scenarios in
extended (varying-mass) nonlinear massive gravity. Due to the enhanced freedom
in choosing the involved free functions, this cosmological paradigm allows for
a huge variety of solutions that can attract the universe at late times,
comparing to scalar-field cosmology or usual nonlinear massive gravity. Amongst
others, it accepts quintessence, phantom, or cosmological-constant-like
late-time solutions, which moreover can alleviate the coincidence problem.
These features seem to be general and non-sensitive to the imposed ansantzes
and model parameters, and thus extended nonlinear massive gravity can be a good
candidate for the description of nature. | Primordial magnetic fields and gravitational baryogenesis in nonlinear
electrodynamics: The amplification of the primordial magnetic fields and the gravitational
baryogenesis, a mechanism that allows to generate the baryon asymmetry in the
Universe by means of the coupling between the Ricci scalar curvature and the
baryon current, are reviewed in the framework of the nonlinear electrodynamics.
To study the amplification of the primordial magnetic field strength, we write
down the gauge invariant wave equations and then solve them (in the long
wavelength approximation) for three different eras of the Universe: de Sitter,
the reheating and the radiation dominated era. Constraints on parameters
entering the nonlinear electrodynamics are obtained by using the amplitude of
the observed galactic magnetic fields and the baryon asymmetry, which are
characterized by the dimensionless parameters $r\sim 10^{-37}$ and
$\eta_B\lesssim 9\times 10^{-11}$, respectively. |
Chemical abundances in M31 from HII regions: We have obtained multi-slit spectroscopic observations from 3700A to 9200A
with LRIS at the Keck I telescope for 31 HII regions in the disk of the
Andromeda galaxy (M31), spanning a range in galactocentric distance from 3.9
kpc to 16.1 kpc. In 9 HII regions we measure one or several auroral lines
([OIII]4363, [NII]5755, [SIII]6312, [OII]7325), from which we determine the
electron temperature (Te) of the gas and derive chemical abundances using the
'direct Te-based method'. We analyze, for the first time in M31, abundance
trends with galactocentric radius from the 'direct' method, and find that the
Ne/O, Ar/O, N/O and S/O abundance ratios are consistent with a constant value
across the M31 disc, while the O/H abundance ratio shows a weak gradient. We
have combined our data with all spectroscopic observations of HII regions in
M31 available in the literature, yielding a sample of 85 HII regions spanning
distances from 3.9 kpc to 24.7 kpc (0.19 - 1.2 R25) from the galaxy center. We
have tested a number of empirical calibrations of strong emission line ratios.
We find that the slope of the oxygen abundance gradient in M31 is
-0.023+/-0.002 dex/kpc, and that the central oxygen abundance is in the range
12+log(O/H) = 8.71 - 8.91 dex (i.e. between 1.05 and 1.66 times the solar
value, for 12+log(O/H)_solar=8.69), depending on the calibration adopted. The
HII region oxygen abundances are compared with the results from other
metallicity indicators (supergiant stars and planetary nebulae). The comparison
shows that HII region O/H abundances are systematically ~0.3 dex below the
stellar ones. This discrepancy is discussed in terms of oxygen depletion onto
dust grains and possible biases affecting Te-based oxygen abundances at high
metallicity. | Lower bias, lower noise CMB lensing with foreground-hardened estimators: Extragalactic foregrounds in temperature maps of the Cosmic Microwave
Background (CMB) severely limit the ability of standard estimators to
reconstruct the weak lensing potential. These foregrounds are not fully
removable by multi-frequency cleaning or masking and can lead to large biases
if not properly accounted for. For foregrounds made of a number of unclustered
point sources, an estimator for the source amplitude can be derived and
deprojected, removing any bias to the lensing reconstruction. We show with
simulations that all of the extragalactic foregrounds in temperature can be
approximated by a collection of sources with identical profiles, and that a
simple bias hardening technique is effective at reducing any bias to lensing,
at a minimal noise cost. We compare the performance and bias to other methods
such as "shear-only" reconstruction, and discuss how to jointly deproject any
arbitrary number of foregrounds, each with an arbitrary profile. In particular,
for a Simons Observatory-like experiment foreground-hardened estimators allow
us to extend the maximum multipole used in the reconstruction, increasing the
overall statistical power by $\sim 50\%$ over the standard quadratic estimator,
both in auto and cross-correlation. We conclude that source hardening
outperforms the standard lensing quadratic estimator both in auto and
cross-correlation, and in terms of lensing signal-to-noise and foreground bias. |
Future Steps in Cosmology using Spectral Distortions of the Cosmic
Microwave Background: Since the measurements of COBE/FIRAS in the mid-90's we know that the energy
spectrum of the cosmic microwave background (CMB) is extremely close to that of
a perfect blackbody at an average temperature T0~2.726K. However, a number of
early-universe processes are expected to create CMB spectral distortions -
departures of the average CMB energy spectrum from a blackbody - at a level
that is within reach of present-day technology. This provides strong motivation
to study the physics of CMB spectral distortions and ask what these small
signals might be able to tell us about the Universe we live in. In this
lecture, I will give a broad-brush overview of recent theoretical and
experimental developments, explaining why future spectroscopic measurements of
the CMB will open an unexplored new window to early-universe and particle
physics. I will give an introduction about the different types of distortions,
how they evolve and thermalize and highlight some of the physical processes
that can cause them. I hope to be able to convince you that CMB spectral
distortions could open an exciting new path forward in CMB cosmology, which is
complementary to planned and ongoing searches for primordial B-mode
polarization signals. Spectral distortions should thus be considered very
seriously as part of the activities in the next decades. | Radio Loud AGN in the 2XMMi catalogue: We are carrying out a search for all radio loud Active Galactic Nuclei
observed with XMM-Newton, including targeted and field sources to perform a
multi-wavelength study of these objects. We have cross-correlated the
Veron-Cetty & Veron (2010) catalogue with the XMM-Newton Serendipitous Source
Catalogue (2XMMi) and found about 4000 matched sources. A literature search
provided radio, optical, and X-ray data for 403 sources. Here we summarize the
first results of our study. |
The COS-Halos Survey: Physical Conditions and Baryonic Mass in the
Low-Redshift Circumgalactic Medium: We analyze the physical conditions of the cool, photoionized (T $\sim 10^4$
K) circumgalactic medium (CGM) using the COS-Halos suite of gas column density
measurements for 44 gaseous halos within 160 kpc of $L \sim L^*$ galaxies at $z
\sim 0.2$. These data are well described by simple photoionization models, with
the gas highly ionized (n$_{\rm HII}$/n$_{\rm H} \gtrsim 99\%$) by the
extragalactic ultraviolet background (EUVB). Scaling by estimates for the
virial radius, R$_{\rm vir}$, we show that the ionization state (tracked by the
dimensionless ionization parameter, U) increases with distance from the host
galaxy. The ionization parameters imply a decreasing volume density profile
n$_{\rm H}$ = (10$^{-4.2 \pm 0.25}$)(R/R$_{\rm vir})^{-0.8\pm0.3}$. Our derived
gas volume densities are several orders of magnitude lower than predictions
from standard two-phase models with a cool medium in pressure equilibrium with
a hot, coronal medium expected in virialized halos at this mass scale. Applying
the ionization corrections to the HI column densities, we estimate a lower
limit to the cool gas mass M$_{\rm CGM}^{\rm cool} > 6.5 \times 10^{10}$
M$_{\odot}$ for the volume within R $<$ R$_{\rm vir}$. Allowing for an
additional warm-hot, OVI-traced phase, the CGM accounts for at least half of
the baryons purported to be missing from dark matter halos at the 10$^{12}$
M$_{\odot}$ scale. | Ambiguities in gravitational lens models: impact on time delays of the
source position transformation: The central ambition of the modern time delay cosmography consists in
determining the Hubble constant $H_0$ with a competitive precision. However,
the tension with $H_0$ obtained from the Planck satellite for a spatially-flat
$\Lambda$CDM cosmology suggests that systematic errors may have been
underestimated. The most critical one probably comes from the degeneracy
existing between lens models that was first formalized by the well-known
mass-sheet transformation (MST). In this paper, we assess to what extent the
source position transformation (SPT), a more general invariance transformation
which contains the MST as a special case, may affect the time delays predicted
by a model. To this aim we use pySPT, a new open-source python package fully
dedicated to the SPT that we present in a companion paper. For axisymmetric
lenses, we find that the time delay ratios between a model and its SPT-modified
counterpart simply scale like the corresponding source position ratios, $\Delta
\hat{t}/ \Delta t \approx \hat{\beta}/\beta$, regardless of the mass profile
and the isotropic SPT. Similar behavior (almost) holds for non-axisymmetric
lenses in the double image regime and for opposite image pairs in the quadruple
image regime. In the latter regime, we also confirm that the time delay ratios
are not conserved. In addition to the MST effects, the SPT-modified time delays
deviate in general no more than a few percent for particular image pairs,
suggesting that its impact on time-delay cosmography seems not be as crucial as
initially suspected. We also reflected upon the relevance of the SPT validity
criterion and present arguments suggesting that it should be reconsidered. Even
though a new validity criterion would affect the time delays in a different
way, we expect from numerical simulations that our conclusions will remain
unchanged. |
Gravitational Wave Anisotropies from Primordial Black Holes: An observable stochastic background of gravitational waves is generated
whenever primordial black holes are created in the early universe thanks to a
small-scale enhancement of the curvature perturbation. We calculate the
anisotropies and non-Gaussianity of such stochastic gravitational waves
background which receive two contributions, the first at formation time and the
second due to propagation effects. The former contribution can be generated if
the distribution of the curvature perturbation is characterized by a local and
scale-invariant shape of non-Gaussianity. Under such an assumption, we conclude
that a sizeable magnitude of anisotropy and non-Gaussianity in the
gravitational waves would suggest that primordial black holes may not comply
the totality of the dark matter. | The merger history, AGN and dwarf galaxies of Hickson Compact Group 59: Compact group galaxies often appear unaffected by their unusually dense
environment. Closer examination can, however, reveal the subtle, cumulative
effects of multiple galaxy interactions. Hickson Compact Group (HCG) 59 is an
excellent example of this situation. We present a photometric study of this
group in the optical (HST), infrared (Spitzer) and X-ray (Chandra) regimes
aimed at characterizing the star formation and nuclear activity in its
constituent galaxies and intra-group medium. We associate five dwarf galaxies
with the group and update the velocity dispersion, leading to an increase in
the dynamical mass of the group of up to a factor of 10 (to 2.8e13 Msun), and a
subsequent revision of its evolutionary stage. Star formation is proceeding at
a level consistent with the morphological types of the four main galaxies, of
which two are star-forming and the other two quiescent. Unlike in some other
compact groups, star-forming complexes across HCG 59 closely follow mass-radius
scaling relations typical of nearby galaxies. In contrast, the ancient globular
cluster populations in galaxies HCG 59A and B show intriguing irregularities,
and two extragalactic HII regions are found just west of B. We age-date a faint
stellar stream in the intra-group medium at ~1 Gyr to examine recent
interactions. We detect a likely low-luminosity AGN in HCG 59A by its ~10e40
erg/s X-ray emission; the active nucleus rather than star formation can account
for the UV+IR SED. We discuss the implications of our findings in the context
of galaxy evolution in dense environments. |
Inflationary Dynamics with a Non-Abelian Gauge Field: We study the dynamics of the universe with a scalar field and an SU(2)
non-Abelian Gauge (Yang-Mills) field. The scalar field has an exponential
potential and the Yang-Mills field is coupled to the scalar field with an
exponential function of the scalar field. We find that the magnetic component
of the Yang-Mills field assists acceleration of the cosmic expansion and a
power-law inflation becomes possible even if the scalar field potential is
steep, which may be expected from some compactification of higher-dimensional
unified theories of fundamental interactions. This power-law inflationary
solution is a stable attractor in a certain range of coupling parameters.
Unlike the case with multiple Abelian gauge fields, the power-law inflationary
solution with the dominant electric component is unstable because of the
existence of non-linear coupling of the Yang-Mills field. We also analyze the
dynamics for the non-inflationary regime, and find several attractor solutions. | J-PAS: forecasts on dark energy and modified gravity theories: The next generation of galaxy surveys will allow us to test one of the most
fundamental assumptions of the standard cosmology, i.e., that gravity is
governed by the general theory of relativity (GR). In this paper we investigate
the ability of the Javalambre Physics of the Accelerating Universe
Astrophysical Survey (J-PAS) to constrain GR and its extensions. Based on the
J-PAS information on clustering and gravitational lensing, we perform a Fisher
matrix forecast on the effective Newton constant, $\mu$, and the gravitational
slip parameter, $\eta$, whose deviations from unity would indicate a breakdown
of GR. Similar analysis is also performed for the DESI and Euclid surveys and
compared to J-PAS with two configurations providing different areas, namely an
initial expectation with 4000 $\mathrm{deg}^2$ and the future best case
scenario with 8500 $\mathrm{deg}^2$. We show that J-PAS will be able to measure
the parameters $\mu$ and $\eta$ at a sensitivity of $2\% - 7\%$, and will
provide the best constraints in the interval $z = 0.3 - 0.6$, thanks to the
large number of ELGs detectable in that redshift range. We also discuss the
constraining power of J-PAS for dark energy models with a time-dependent
equation-of-state parameter of the type $w(a)=w_0+w_a(1-a)$, obtaining $\Delta
w_0=0.058$ and $\Delta w_a=0.24$ for the absolute errors of the dark energy
parameters. |
Dust Content, Galaxy Orientations, and Shape Noise in Imaging Surveys: We show that dust absorption in disk galaxies leads to a color- and
orientation-dependent centroid shift which is expected to be observable in
multi-band imaging surveys. This centroid shift is an interesting new probe
which contains astrophysically and cosmologically relevant information: it can
be used to probe the dust content of a large sample of galaxies, and to reduce
the shape noise due to inclination of disk galaxies for weak lensing shear.
Specifically, we find that data sets comparable to CFHTLenS, the Dark Energy
Survey (DES) or the Hyper Suprime-Cam (HSC) survey should provide a dust
measurement for several hundred galaxies per square degree. Conversely, given
knowledge of the dust optical depth, this technique will significantly lower
the shape noise for the brightest galaxies in the sample (signal-to-noise
greater than a few hundred), thereby increasing their relative importance for
the weak lensing shear measurement. | The XXL Survey XXV. Cosmological analysis of the C1 cluster number
counts: Context. We present an estimation of cosmological parameters with clusters of
galaxies. Aims. We constrain the $\Omega_m$, $\sigma_8$, and $w$ parameters
from a stand-alone sample of X-ray clusters detected in the 50 deg$^2$ XMM-XXL
survey with a well-defined selection function. Methods. We analyse the redshift
distribution of a sample comprising 178 high S/N clusters out to a redshift of
unity. The cluster sample scaling relations are determined in a self-consistent
manner. Results. In a lambda cold dark matter ($\Lambda$CDM) model, the
cosmology favoured by the XXL clusters compares well with results derived from
the Planck S-Z clusters for a totally different sample (mass/redshift range,
selection biases, and scaling relations). However, with this preliminary sample
and current mass calibration uncertainty, we find no inconsistency with the
Planck CMB cosmology. If we relax the $w$ parameter, the Planck CMB
uncertainties increase by a factor of $\sim$10 and become comparable with those
from XXL clusters. Combining the two probes allows us to put constraints on
$\Omega_m$=0.316$\pm$0.060, $\sigma_8$=0.814$\pm$0.054, and $w$=-1.02$\pm$0.20.
Conclusions. This first self-consistent cosmological analysis of a sample of
serendipitous XMM clusters already provides interesting insights into the
constraining power of the XXL survey. Subsequent analysis will use a larger
sample extending to lower confidence detections and include additional
observable information, potentially improving posterior uncertainties by
roughly a factor of 3. |
The Tensor-Vector-Scalar theory and its cosmology: Over the last few decades, astronomers and cosmologists have accumulated vast
amounts of data clearly demonstrating that our current theories of fundamental
particles and of gravity are inadequate to explain the observed discrepancy
between the dynamics and the distribution of the visible matter in the
Universe. The Modified Newtonian Dynamics (MOND) proposal aims at solving the
problem by postulating that Newton's second law of motion is modified for
accelerations smaller than ~10^{-10}m/s^2. This simple amendment, has had
tremendous success in explaining galactic rotation curves. However, being
non-relativistic, it cannot make firm predictions for cosmology.
A relativistic theory called Tensor-Vector-Scalar (TeVeS) has been proposed
by Bekenstein building on earlier work of Sanders which has a MOND limit for
non-relativistic systems.
In this article I give a short introduction to TeVeS theory and focus on its
predictions for cosmology as well as some non-cosmological studies. | Constraining Co-Varying Coupling Constants from Globular Cluster Age: Equations governing the evolution of a star involve multiple coupling
constants. Thus, the time it spends as a main-sequence star can be expected to
depend on whether or not such constants vary over the time scale of stellar
evolution. When the star belongs to a globular cluster, the star's age cannot
exceed that of the globular cluster, and the latter cannot exceed the age of
the Universe. This fact can be used to constrain or verify the variation of the
coupling constants, i.e., the speed of light c, the gravitational constant G,
the Planck constant h, and the Boltzmann constant k. We have estimated the age
of the main-sequence star analytically from the time it takes to synthesize all
its hydrogen into helium under fixed and varying coupling constants scenarios.
When we permitted the interrelated variation of the four constants ($G\thicksim
c^{3}\thicksim h^{3}\thicksim k^{3/2}$) and differentiated between the
cosmological energy and local energy conservation laws, we could show that the
variation of the constants established in our earlier studies, i.e.,
$(\dot{G}/G)_{0}=3(\dot{c}/c)_{0}=(\dot{h}/h)_{0}=1.5 (\dot{k}/k)_{0}=5.4H_{0}
=3.90(\pm 0.04)\times 10^{-10} yr^{-1}$ at the current cosmic time is
consistent with the present work. Nevertheless, the challenge remains to come
up with an experiment, astrometric or terrestrial, that can unequivocally prove
or falsify the predicted variation. |
Searching for Signal of Primordial Black Hole from CMB Lensing and
$γ$-ray Emissions: In this $\textit{Letter}$, we search for the signal of the primordial black
holes (PBHs) by correlating the $\gamma$-ray emissions in the MeV energy band
produced by the Hawking evaporation and the lensing effect of the cosmic
microwave background (CMB). We use the conservative case of the astrophysical
model as much as possible in the calculations, since the potential
astrophysical origins dominate the observed emission in the MeV energy band. By
carefully discussing the appropriate energy bands corresponding to different
PBHs masses, it is worth expecting a tight constraint on the fraction of the
Schwarzschild PBHs in the mass range of $10^{16} - 5\times10^{17}\,{\rm g}$, by
simulations of the sensitivity of the future CMB-S4 project and the
$\gamma$-ray telescope e-ASTROGAM. Furthermore, we also consider the PBHs model
with spins, and find that the constraining ability of the PBHs fraction from
the correlation between CMB lensing and $\gamma$-ray emissions can be improved
by another order of magnitude, which could importantly fill the gaps with PBHs
fraction limits in the mass range of $5\times 10^{17} - 2\times 10^{18}\,{\rm
g}$. | Resolving galaxy cluster gas properties at z~1 with XMM-Newton and
Chandra: We present a pilot X-ray study of the five most massive ($M_{500}>5 \times
10^{14} M_{\odot}$), distant (z~1), galaxy clusters detected via the
Sunyaev-Zeldovich effect. We optimally combine XMM-Newton and Chandra X-ray
observations by leveraging the throughput of XMM to obtain spatially-resolved
spectroscopy, and the spatial resolution of Chandra to probe the bright inner
parts and to detect embedded point sources. Capitalising on the excellent
agreement in flux-related measurements, we present a new method to derive the
density profiles, constrained in the centre by Chandra and in the outskirts by
XMM. We show that the Chandra-XMM combination is fundamental for morphological
analysis at these redshifts, the Chandra resolution being required to remove
point source contamination, and the XMM sensitivity allowing higher
significance detection of faint substructures. The sample is dominated by
dynamically disturbed objects. We use the combined Chandra-XMM density profiles
and spatially-resolved temperature profiles to investigate thermodynamic
quantities including entropy and pressure. From comparison of the scaled
profiles with the local REXCESS sample, we find no significant departure from
standard self-similar evolution, within the dispersion, at any radius, except
for the entropy beyond 0.7$R_{500}$. The baryon mass fraction tends towards the
cosmic value, with a weaker dependence on mass than observed in the local
Universe. We compare with predictions from numerical simulations. The present
pilot study demonstrates the utility and feasibility of spatially-resolved
analysis of individual objects at high-redshift through the combination of XMM
and Chandra observations. Observations of a larger sample will allow a fuller
statistical analysis to be undertaken, in particular of the intrinsic scatter
in the structural and scaling properties of the cluster population. (abridged) |
The redshift evolution of extragalactic magnetic fields: Faraday rotation studies of distant radio sources can constrain the evolution
and the origin of cosmic magnetism. We use data from the LOFAR Two Metre Sky
Survey: Data Release 2 (LoTSS DR2) to study the dependence of the Faraday
rotation measure (RM) on redshift. By focusing on radio sources that are close
in terms of their projection on the sky, but physically unrelated (random
pairs), we measure the RM difference, $\Delta$RM, between the two sources.
Thus, we isolate the extragalactic contribution to $\Delta$RM from other
contributions. We present a statistical analysis of the resulting sample of
random pairs and find a median absolute RM difference |$\Delta$RM| $ = (1.79
\pm 0.09)$ rad/m$^{2}$ , with |$\Delta$RM| uncorrelated both with respect to
the redshift difference of the pair and the redshift of the nearer source, and
a median excess of random pairs over physical pairs of $(1.65 \pm 0.10)$
rad/m$^{2}$. We seek to reproduce this result with Monte Carlo simulations
assuming a non vanishing seed cosmological magnetic field and a redshift
evolution of the comoving magnetic field strength that varies as $1/(1 +
z)^{\gamma}$. We find the best fitting results $B_0 \equiv B_{\rm comoving}(z =
0) \lesssim (2.0 \pm 0.2)$ nG and $\gamma \lesssim 4.5 \pm 0.2$ that we
conservatively quote as upper limits due to an unmodelled but non vanishing
contribution of local environments to the RM difference. A comparison with
cosmological simulations shows our results to be incompatible with primordial
magnetogenesis scenarios with uniform seed fields of order nG. | Hydrodynamic simulations of correlation and scatter in galaxy cluster
maps: The two dimensional structure of hot gas in galaxy clusters contains
information about the hydrodynamical state of the cluster, which can be used to
understand the origin of scatter in the thermodynamical properties of the gas,
and to improve the use of clusters to probe cosmology. Using a set of
hydrodynamical simulations, we provide a comparison between various maps
currently employed in the X-ray analysis of merging clusters and those cluster
maps anticipated from forthcoming observations of the thermal
Sunyaev-Zel'dovich effect. We show the following: 1) an X-ray pseudo-pressure,
defined as square root of the soft band X-ray image times the temperature map
is a good proxy for the SZ map; 2) we find that clumpiness is the main reason
for deviation between X-ray pseudo-pressure and SZ maps; 3) the level of
clumpiness can be well characterized by X-ray pseudo-entropy maps. 4) We
describe the frequency of deviation in various maps of clusters as a function
of the amplitude of the deviation. This enables both a comparison to
observations and a comparison to effects of introduction of complex physical
processes into simulation. |
Void magnetic field and its primordial origin in inflation: Since magnetic fields in galaxies, galactic clusters and even void regions
are observed, theoretical attempts to explain their origin are strongly
motivated. It is interesting to consider that inflation is responsible for the
origin of the magnetic fields as well as the density perturbation. However, it
is known that inflationary magnetogenesis suffers from several problems. We
explore these problems by using a specific model, namely the kinetic coupling
model, and show how the model is constrained. Model independent arguments are
also discussed. | Model-independent bubble wall velocities in local thermal equilibrium: Accurately determining bubble wall velocities in first-order phase
transitions is of great importance for the prediction of gravitational wave
signals and the matter-antimatter asymmetry. However, it is a challenging task
which typically depends on the underlying particle physics model. Recently, it
has been shown that assuming local thermal equilibrium can provide a good
approximation when calculating the bubble wall velocity. In this paper, we
provide a model-independent determination of bubble wall velocities in local
thermal equilibrium. Our results show that, under the reasonable assumption
that the sound speeds in the plasma are approximately uniform, the
hydrodynamics can be fully characterized by four quantities: the phase strength
$\alpha_n$, the ratio of the enthalpies in the broken and symmetric phases,
$\Psi_n$, and the sound speeds in both phases, $c_s$ and $c_b$. We provide a
code snippet that allows for a determination of the wall velocity and energy
fraction in local thermal equilibrium in any model. In addition, we present a
fit function for the wall velocity in the case $c_s = c_b = 1/\sqrt 3$. |
The Dark Energy Survey Supernova Program: Modelling selection efficiency
and observed core collapse supernova contamination: The analysis of current and future cosmological surveys of type Ia supernovae
(SNe Ia) at high-redshift depends on the accurate photometric classification of
the SN events detected. Generating realistic simulations of photometric SN
surveys constitutes an essential step for training and testing photometric
classification algorithms, and for correcting biases introduced by selection
effects and contamination arising from core collapse SNe in the photometric SN
Ia samples. We use published SN time-series spectrophotometric templates,
rates, luminosity functions and empirical relationships between SNe and their
host galaxies to construct a framework for simulating photometric SN surveys.
We present this framework in the context of the Dark Energy Survey (DES) 5-year
photometric SN sample, comparing our simulations of DES with the observed DES
transient populations. We demonstrate excellent agreement in many
distributions, including Hubble residuals, between our simulations and data. We
estimate the core collapse fraction expected in the DES SN sample after
selection requirements are applied and before photometric classification. After
testing different modelling choices and astrophysical assumptions underlying
our simulation, we find that the predicted contamination varies from 5.8 to 9.3
per cent, with an average of 7.0 per cent and r.m.s. of 1.1 per cent. Our
simulations are the first to reproduce the observed photometric SN and host
galaxy properties in high-redshift surveys without fine-tuning the input
parameters. The simulation methods presented here will be a critical component
of the cosmology analysis of the DES photometric SN Ia sample: correcting for
biases arising from contamination, and evaluating the associated systematic
uncertainty. | Spherical accretion of collisional gas in modified gravity I:
self-similar solutions and a new cosmological hydrodynamical code: The spherical collapse scenario has great importance in cosmology since it
captures several crucial aspects of structure formation. The presence of
self-similar solutions in the Einstein-de Sitter (EdS) model greatly simplifies
its analysis, making it a powerful tool to gain valuable insights into the real
and more complicated physical processes involved in galaxy formation. While
there has been a large body of research to incorporate various additional
physical processes into spherical collapse, the effect of modified gravity (MG)
models, which are popular alternatives to the $\Lambda CDM$ paradigm to explain
the cosmic acceleration, is still not well understood in this scenario. In this
paper, we study the spherical accretion of collisional gas in a particular MG
model, which is a rare case that also admits self-similar solutions. The model
displays interesting behaviours caused by the enhanced gravity and a screening
mechanism. Despite the strong effects of MG, we find that its self-similar
solution agrees well with that of the EdS model. These results are used to
assess a new cosmological hydrodynamical code for spherical collapse
simulations introduced here, which is based on the hyperbolic partial
differential equation engine ExaHyPE 2. Its good agreement with the theoretical
predictions confirms the reliability of this code in modelling astrophysical
processes in spherical collapse. We will use this code to study the evolution
of gas in more realistic MG models in future work. |
Signature of Massive Neutrinos from the Clustering of Critical Points.
I. Density-threshold-based Analysis in Configuration Space: Critical points represent a subset of special points tracing cosmological
structures, carrying remarkable topological properties. They thus offer a
richer high-level description of the multiscale cosmic web, being more robust
to systematic effects. For the first time, we characterize here their
clustering statistics in massive neutrino cosmologies, including
cross-correlations, and quantify their simultaneous imprints on the
corresponding web constituents - i.e., halos, filaments, walls, and voids - for
a series of rarity levels. Our first analysis is centered on a
density-threshold-based approach in configuration space. In particular, we show
that the presence of massive neutrinos does affect the baryon acoustic
oscillation peak amplitudes of all of the critical point correlation functions
above/below the rarity threshold, as well as the positions of their
correspondent inflection points at large scales: departures from analogous
measurements carried out in the baseline massless neutrino scenario can reach
up to ~7% in autocorrelations and ~9% in cross-correlations at z=0 when
M_nu=0.1 eV, and are more pronounced for higher neutrino mass values. In turn,
these combined multiscale effects can be used as a novel technique to set upper
limits on the summed neutrino mass and infer the type of hierarchy. Our study
is particularly relevant for ongoing and future large-volume redshift surveys
such as the Dark Energy Spectroscopic Instrument and the Rubin Observatory
Legacy Survey of Space and Time, which will provide unique datasets suitable
for establishing competitive neutrino mass constraints. | Herschel-ATLAS: far-infrared properties of radio-selected galaxies: We use the Herschel-ATLAS science demonstration data to investigate the
star-formation properties of radio-selected galaxies in the GAMA-9h field as a
function of radio luminosity and redshift. Radio selection at the lowest radio
luminosities, as expected, selects mostly starburst galaxies. At higher radio
luminosities, where the population is dominated by AGN, we find that some
individual objects are associated with high far-infrared luminosities. However,
the far-infrared properties of the radio-loud population are statistically
indistinguishable from those of a comparison population of radio-quiet galaxies
matched in redshift and K-band absolute magnitude. There is thus no evidence
that the host galaxies of these largely low-luminosity (Fanaroff-Riley class
I), and presumably low-excitation, AGN, as a population, have particularly
unusual star-formation histories. Models in which the AGN activity in
higher-luminosity, high-excitation radio galaxies is triggered by major mergers
would predict a luminosity-dependent effect that is not seen in our data (which
only span a limited range in radio luminosity) but which may well be detectable
with the full Herschel-ATLAS dataset. |
Primordial non-Gaussianity and power asymmetry with quantum
gravitational effects in loop quantum cosmology: Loop quantum cosmology (LQC) provides a resolution of the classical big bang
singularity in the deep Planck era. The evolution, prior to the usual slow-roll
inflation, naturally generates excited states at the onset of the slow-roll
inflation. It is expected that these quantum gravitational effects could leave
its fingerprints on the primordial perturbation spectrum and non-Gaussianity,
and lead to some observational evidences in the cosmic microwave background
(CMB). While the impact of the quantum effects on the primordial perturbation
spectrum has been already studied and constrained by current data, in this
paper we continue studying such effects on the non-Gaussianity of the
primordial curvature perturbations. In this paper, we present detailed and
analytical calculations of the non-Gaussianity and show explicitly that the
corrections due to quantum effects are in the same magnitude of the slow-roll
parameters in the observable scales and thus are well within current
observational constraints. Despite this, we show that the non-Gaussianity in
the squeezed limit can be enhanced at superhorizon scales and further, these
effects may yield a large statistical anisotropy on the power spectrum through
the Erickcek-Kamionkowski-Carroll mechanism. | The holiest grail: I will discuss to what degree the cosmic microwave background (CMB) can be
used to constrain primordial non-Gaussianity involving one tensor and two
scalar fluctuations, focusing on the correlation of one $B$-mode polarization
fluctuation with two temperature fluctuations (BTT). In the simplest models of
inflation, the tensor-scalar-scalar primordial bispectrum is non-vanishing and
is of the same order in slow-roll parameters as the scalar-scalar-scalar
bispectrum. I will show that constraints from an experiment like CMB-Stage IV
using this observable are more than an order of magnitude better than those on
the same primordial coupling obtained from temperature measurements alone. I
will argue that $B$-mode non-Gaussianity opens up an as-yet-unexplored window
into the early Universe, demonstrating that significant information on
primordial physics remains to be harvested from CMB anisotropies. BTT presents
a measure of both primordial tensors and primordial non-Gaussianity, two of the
most sought after signatures of the inflationary paradigm. |
HOLISMOKES -- V. Microlensing of type II supernovae and time-delay
inference through spectroscopic phase retrieval: We investigate strongly gravitationally lensed type II supernovae (LSNe II)
for time-delay cosmography incorporating microlensing effects, which expands on
previous microlensing studies of type Ia supernovae (SNe Ia). We use the
radiative-transfer code ${\rm \small TARDIS}$ to recreate five spectra of the
prototypical SN 1999em at different times within the plateau phase of the light
curve. The microlensing-induced deformations of the spectra and light curves
are calculated by placing the SN into magnification maps generated with the
code ${\rm \small GERLUMPH}$. We study the impact of microlensing on the color
curves and find that there is no strong influence on them during the
investigated time interval of the plateau phase. The color curves are only
weakly affected by microlensing due to the almost achromatic behavior of the
intensity profiles. However, the lack of non-linear structure in the color
curves makes time-delay measurements difficult given the possible presence of
differential dust extinction. Therefore, we further investigate SN phase
inference through spectral absorption lines under the influence of microlensing
and Gaussian noise. As the spectral features shift to longer wavelengths with
progressing time after explosion, the measured wavelength of a specific
absorption line provides information on the epoch of the SN. The comparison
between retrieved epochs of two observed lensing images then gives the time
delay of the images. We find that the phase retrieval method using spectral
features yields accurate delays with uncertainties $\small {\lesssim}$2 days,
making it a promising approach. | Compact groups in theory and practice -- IV. The connection to
large-scale structure: We investigate the properties of photometrically-selected compact groups
(CGs) in the Sloan Digital Sky Survey. In this paper, the fourth in a series,
we focus on understanding the characteristics of our observed CG sample with
particular attention paid to quantifying and removing contamination from
projected foreground or background galaxies. Based on a simple comparison of
pairwise redshift likelihoods, we find that approximately half of compact
groups in the parent sample contain one or more projected (interloping)
members; our final clean sample contains 4566 galaxies in 1086 compact groups.
We show that half of the remaining CGs are associated with rich groups (or
clusters), i.e. they are embedded sub-structure. The other half have spatial
distributions and number-density profiles consistent with the interpretation
that they are either independently distributed structures within the field
(i.e. they are isolated) or associated with relatively poor structures.
Comparisons of late-type and red-sequence fractions in radial annuli show that
galaxies around apparently isolated compact groups resemble the field
population by 300 to 500 kpc from the group centre. In contrast, the galaxy
population surrounding embedded compact groups appears to remain distinct from
the field out beyond 1 to 2 Mpc, consistent with results for rich groups. We
take this as additional evidence that the observed distinction between compact
groups, i.e. isolated vs. embedded, is a separation between different host
environments. |
Star Formation and Metallicity Gradients in Semi-analytic Models of Disk
Galaxy Formation: We have updated our radially-resolved SAMs of galaxy formation, which track
both the atomic and molecular gas phases of the ISM. The models are adapted
from those of Guo et al. using similar methodology as in Fu et al. and are run
on halo merger trees from the MS and MS II with the following main changes: (1)
We adopt a simple star formation law where \Sigma_SFR \propto \Sigma_H2 (2) We
inject the heavy elements produced by supernovae directly into the halo hot
gas, instead of first mixing them with the cold gas in the disk. (3) We include
radial gas inflows in disks using a model of the form v_inflow = \alpha r. The
models are used to study the radial profiles of star formation rate and
gas-phase metallicity in present-day galaxies. The \Sigma_H2 profiles in L*
galaxies place strong constraints on inflow velocities, favouring models where
v_inflow~7km/s at a galactocentric radius of 10kpc. Radial gas inflow has
little influence on gas-phase and stellar metallicity gradients, which are
affected much more strongly by the fraction of metals that are directly
injected into the halo gas, rather than mixed with the cold gas. Metals ejected
out of the galaxy in early epochs result in late infall of pre-enriched gas and
flatter present-day gas-phase metallicity gradients. A prescription in which
80% of the metals are injected into the halo gas results in good fits to the
flat observed metallicity gradients in galaxies with stellar masses greater
than 10^10 M_sun, as well as the relations between gas-phase metallicity and
sSFR in the outer parts of galactic disks. We examine the correlation between
gas-phase metallicity gradient and global galaxy properties, finding that it is
most strongly correlated with the bulge-to-total ratio of the galaxy. This is
because gas is consumed when the bulge forms during galaxy mergers, and the
gas-phase metallicity gradient is then set by newly-accreted gas. | Origin of Cosmic Magnetic Fields: We calculate, in the free Maxwell theory, the renormalized quantum vacuum
expectation value of the two-point magnetic correlation function in de Sitter
inflation. We find that quantum magnetic fluctuations remain constant during
inflation instead of being washed out adiabatically, as usually assumed in the
literature. The quantum-to-classical transition of super-Hubble magnetic modes
during inflation, allow us to treat the magnetic field classically after
reheating, when it is coupled to the primeval plasma. The actual magnetic field
is scale independent and has an intensity of few \times 10^(-12) G if the
energy scale of inflation is few \times 10^(16) GeV. Such a field accounts for
galactic and galaxy cluster magnetic fields. |
(P)reheating after minimal Plateau Inflation and constraints from CMB: We have studied the preheating phase for a class of plateau inflationary
model considering the four-legs interaction term $(1/2)g^2\phi^2\chi^2$ between
the inflaton $(\phi)$ and reheating field $(\chi)$. We specifically focus on
the effects of a parameter $\phi_*$ that controls inflationary dynamics and the
shape of the inflaton potential. For $\phi_* < M_p$, the departure of the
inflaton potential from the usual power-law behavior $\phi^n$ significantly
modifies the microscopic behavior of the preheating dynamics. We analyze and
compare the efficiency of production, thermalization and the final equation of
state of the system for different models under consideration with $n=2,4,6$ for
two different values of $\phi_*$. Most importantly as we increase $n$, or
decrease $\phi_*$, the preheating occurs very efficiently with the final
equation of state to be that of the radiation, $w=1/3$. Specially for $n=2$,
the final equation of state turned out to be $w\simeq 0.2$. However, a complete
decay of inflaton could not be achieved with the four-legs interaction for any
model under consideration. Therefore, in order to complete the reheating
process, we perform the perturbative analysis for the second stage of the
reheating phase. Taking the end product of the preheating phase as an initial
condition we have solved the homogeneous Boltzmann equations for both the
fields supplemented by the constraints coming from the subsequent entropy
conservation. In so doing, we can calculate the reheating temperature which is
otherwise ill-defined right after the end of preheating. The temperature can be
uniquely fixed for a given inflaton decay constant and the CMB temperature. We
also compare our results with the conventional reheating constraint analysis
and discuss the limit of inflaton decay constant from the field theory
perspective. | Lemaître and Hubble: What was discovered - if any - in 1927-29?: The Big Bang predicted theoretically by Friedmann could not be discovered in
the 1920th, since global cosmological distances (more than 300-1000 Mpc) were
not available for observations at that time. In 1927-29, Lema\^itre and Hubble
studied receding motions of galaxies at local distances of less than 20-30 Mpc
and found that the motions followed the (nearly) linear velocity-distance
relation, known now as Hubble's law. For decades, the real nature of this
phenomenon has remained a mystery, in Sandage's words. After the discovery of
dark energy, it was suggested that the dynamics of local expansion flows is
dominated by omnipresent dark energy, and it is the dark energy antigravity
that is able to introduce the linear velocity-distance relation to the flows.
It implies that Hubble's law observed at local distances was in fact the first
observational manifestation of dark energy. If this is the case, the commonly
accepted criteria of scientific discovery lead to the conclusion: In 1927,
Lema\^itre discovered dark energy and Hubble confirmed this in 1929. |
Primordial black hole mass functions as a probe of cosmic origin: We discuss a novel window to probe the origin of our universe via the mass
functions of primordial black holes (PBHs). The mass functions of PBHs are
simply estimated using the conventional Press-Schechter formalism for two
paradigms of cosmic origin, including inflationary $\Lambda$CDM and bounce
cosmology. The standard inflationary $\Lambda$CDM model cannot generate an
appreciable number of massive PBHs; however, non-trivial inflation models with
blue-tilted power spectra at small scales and matter bounce cosmology provide
formation mechanisms for heavy PBHs, which in turn, may seed the observed
supermassive black holes (SMBHs). By fitting the SMBH mass functions at high
redshift ($z \sim 6$) derived from Sloan Digital Sky Survey (SDSS) and
Canada-France High-z Quasar Survey (CFHQS) quasars, for two paradigms of cosmic
origin, we derive constraints on the PBH density fraction $f_{\mathrm{PBH}}$ at
$z \sim 6$ and the characteristic mass $M_{\star}$, with the prior assumption
that all SMBHs stem from PBHs. We demonstrate that this newly proposed
procedure, relying on astronomical measurements that utilize deep-field surveys
of SMBHs at high redshift, can be used to constrain models of cosmic origin.
Additionally, although not the main focus of this paper, we evolve the mass
function from $z\sim6$ to $z\sim0$ through an assumption of $3\times 10^8$-year
Eddington's accretion, and give a rough estimation of $f_{\mathrm{PBH}}$ at $z
\sim 0$. | On the Power Spectrum of Dark Matter Substructure in Strong
Gravitational Lenses: Studying the smallest self-bound dark matter structure in our Universe can
yield important clues about the fundamental particle nature of dark matter.
Galaxy-scale strong gravitational lensing provides a unique way to detect and
characterize dark matter substructures at cosmological distances from the Milky
Way. Within the cold dark matter (CDM) paradigm, the number of low-mass
subhalos within lens galaxies is expected to be large, implying that their
contribution to the lensing convergence field is approximately Gaussian and
could thus be described by their power spectrum. We develop here a general
formalism to compute from first principles the substructure convergence power
spectrum for different populations of dark matter subhalos. As an example, we
apply our framework to two distinct subhalo populations: a truncated
Navarro-Frenk-White subhalo population motivated by standard CDM, and a
truncated cored subhalo population motivated by self-interacting dark matter
(SIDM). We study in detail how the subhalo abundance, mass function, internal
density profile, and concentration affect the amplitude and shape of the
substructure power spectrum. We determine that the power spectrum is mostly
sensitive to a specific combination of the subhalo abundance and moments of the
mass function, as well as to the average tidal truncation scale of the largest
subhalos included in the analysis. Interestingly, we show that the asymptotic
slope of the substructure power spectrum at large wave number reflects the
internal density profile of the subhalos. In particular, the SIDM power
spectrum exhibits a characteristic steepening at large wave number absent in
the CDM power spectrum, opening the possibility of using this observable, if at
all measurable, to discern between these two scenarios. |
Probing the time variability of five Fe low broad absorption line
quasars: We study the time variability of five Fe Low ionization Broad Absorption Line
(FeLoBAL) QSOs using repeated spectroscopic observations with the 2m telescope
at IUCAA Girawali observatory (IGO) spanning an interval of upto 10 years. We
report a dramatic variation in Al III and Fe III fine-structure lines in the
spectra of SDSS J221511.93-004549.9 (z_em ~ 1.478). However, there is no such
strong variability shown by the C IV absorption. This source is known to be
unusual with (i) the continuum emission dominated by Fe emission lines, (ii) Fe
III absorption being stronger than Fe II and (iii) the apparent ratio of Fe III
UV 48 to Fe III UV 34 absorption suggesting an inverted population ratio. This
is the first reported detection of time variability in the Fe III
fine-structure lines in QSO spectra. There is a strong reduction in the
absorption strength of these lines between year 2000 and 2008. Using the
template fitting techniques, we show that the apparent inversion of strength of
UV lines could be related to the complex spectral energy distribution of this
QSO. The observed variability can be related to change in the ionization state
of the gas or due to transverse motion of this absorbing gas. The shortest
variability timescale of Al III line gives a lower limit on the electron
density of the absorbing gas as n_e >= 1.1 x 10^4 cm^-3. The remaining 4
FeLoBALs do not show any changes beyond the measurement uncertainties either in
optical depth or in the velocity structure. We present the long-term
photometric light curve for all of our sources. Among them only SDSS
J221511.93-004549.9 shows significant (>= 0.2 mag) variability. | $f(T)$ cosmology in the regime of quasar observations: The open problems related to cosmological tensions in current times have
opened new paths to study new probes to constrain cosmological parameters in
standard and extended cosmologies, in particular, to determine at a local level
the value of the Hubble constant $H_0$, through independent techniques.
However, while standard Cosmological Constant Cold Dark Matter ($\Lambda$CDM)
model has been well constrained and parts of extended cosmology have been
intensively studied, the physics behind them aspects restrains our
possibilities of selecting the best cosmological model that can show a
significant difference from the first model. Therefore, to explore a possible
deviation from a such model that can explain the current discrepancy on the
$H_0$ value, in this work we consider adding the current local observables,
e.g. Supernovae Type Ia (SNIa), $H(z)$ measurements, and Baryon Acoustic
Observations (BAO) combined with two new calibrated Quasars (QSO) datasets
using ultraviolet, x-ray and optical plane techniques. While these can be
identified as part of the high-redshift standard candle objects, the main
characteristics of these are based on fluxes distributions calibrated up to $z
\sim 7 $. We consider five $H_0$ prior scenarios to develop these calibrations.
Furthermore, we found that our estimations provide the possibility to relax the
$H_0$ tension at 2$\sigma$ using a QSO ultraviolet sample in combination with
late measurements showing higher values of $H_0$. Our results can be an initial
start for more serious treatments in the quasars physics from ultraviolet,
x-ray, and optical plane techniques behind the local observations as
cosmological probes to relax the cosmological tensions problems. |
Ring of attraction: overlapping directions of the dipole modulation of
the CMB, the parity asymmetry, and kinematic dipole percolation zone: The largest anisotropy in the cosmic microwave background (CMB) is the 3 mK
kinematic dipole reflecting our motion with respect to the CMB frame and
pointed in the direction $(l, b) = (264^\circ, +48^\circ)$ in Galactic
coordinates. We introduce the concept of the ring of attraction (RA), which is
orthogonal to the axis of the kinematic dipole. These directions overlap with
the zone of percolation for the kinematic dipole, where its amplitude almost
vanishes. We show that along this ring are oriented the directions of the
dipole modulation of the CMB, and positions of the peaks responsible for
generation of parity asymmetry. This coincidence is peculiar at around the 3
sigma level. We analyzed the "interaction" of low multipoles of the CMB with RA
and showed that for odd modes there is a sequence of peaks in the RA direction.
These peaks correlate with each other for different multipoles and result in
mutual amplification of the odd $\ell$ signal for the first 30 multipoles. Our
method sheds new light on the nature of parity asymmetry. It consists of the
deficit of symmetrically located and equal in amplitude peaks in the CMB map in
comparison with asymmetric peaks. | MWA and ASKAP observations of atypical radio-halo-hosting galaxy
clusters: Abell 141 and Abell 3404: We report on the detection of a giant radio halo in the cluster Abell 3404 as
well as confirmation of the radio halo observed in Abell 141 (with linear
extents $\sim 770$ kpc and $\sim 850$ kpc, respectively). We use the Murchison
Widefield Array (MWA) in conjunction with the Australian Square Kilometre Array
Pathfinder (ASKAP) and the Australia Telescope Compact Array (ATCA) to
characterise the emission and intervening radio sources from $\sim100$-$1000$
MHz; power law models are fit to the spectral energy distributions with
spectral indices $\alpha_{88}^{1110} = -1.66 \pm 0.07$ and $\alpha_{88}^{944} =
-1.06 \pm 0.09$ for the radio halos in Abell 3404 and Abell 141, respectively.
We find strong correlation between radio and X-ray surface brightness for
Abell~3404 but little correlation for Abell~141. We note each cluster has an
atypical morphology for a radio-halo--hosting cluster, with Abell 141 having
been previously reported to be in a pre-merging state, and Abell 3404 is
largely relaxed with only minor evidence for a disturbed morphology. We find
that the radio halo power is consistent with the current radio halo sample and
$P_\nu$-$M$ scaling relations, but note that the radio halo in Abell 3404 is an
ultra-steep-spectrum radio halo (USSRH) and, as with other USSRHs lies slightly
below the best-fit $P_{1.4}$-$M$ relation. We find that an updated scaling
relation is consistent with previous results and shifting the frequency to 150
MHz does not significantly alter the best-fit relations with a sample of 86
radio halos. We suggest that the USSRH halo in Abell 3404 represents the faint
class of radio halos that will be found in clusters undergoing weak mergers. |
Nonlinear Perturbations in a Variable Speed of Light Cosmology: A variable speed of light (VSL) cosmology is described in which the causal
mechanism of generating primordial perturbations is achieved by varying the
speed of light in a primordial epoch. This yields an alternative to inflation
for explaining the formation of the cosmic microwave background (CMB) and the
large scale structure (LSS) of the universe. We make use of the $\delta{\cal
N}$ formalism to identify signatures of primordial nonlinear fluctuations, and
this allows the VSL model to be distinguished from inflationary models. In
particular, we find that the parameter $f_{\rm NL}=5$ in the variable speed of
light cosmology. The value of the parameter $g_{\rm NL}$ evolves during the
primordial era and shows a running behavior. | Constraining the redshift evolution of the Cosmic Microwave Background
black-body temperature with PLANCK data: We constrain the deviation of adiabatic evolution of the Universe using the
data on the Cosmic Microwave Background (CMB) temperature anisotropies measured
by the {\it Planck} satellite and a sample of 481 X-ray selected clusters with
spectroscopically measured redshifts. To avoid antenna beam effects, we bring
all the maps to the same resolution. We use a CMB template to subtract the
cosmological signal while preserving the Thermal Sunyaev-Zeldovich (TSZ)
anisotropies; next, we remove galactic foreground emissions around each cluster
and we mask out all known point sources. If the CMB black-body temperature
scales with redshift as $T(z)=T_0(1+z)^{1-\alpha}$, we constrain deviations of
adiabatic evolution to be $\alpha=-0.007\pm 0.013$, consistent with the
temperature-redshift relation of the standard cosmological model. This result
could suffer from a potential bias $\delta\alpha$ associated with the CMB
template, that we quantify it to be $|\delta\alpha|\le 0.02$ and with the same
sign than the measured value of $\alpha$, but is free from those biases
associated with using TSZ selected clusters; it represents the best constraint
to date of the temperature-redshift relation of the Big-Bang model using only
CMB data, confirming previous results. |
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses IX. Time
delays, lens dynamics and baryonic fraction in HE 0435-1223: We present accurate time delays for the quadruply imaged quasar HE 0435-1223.
The delays were measured from 575 independent photometric points obtained in
the R-band between January 2004 and March 2010. With seven years of data, we
clearly show that quasar image A is affected by strong microlensing variations
and that the time delays are best expressed relative to quasar image B. We
measured Delta_t(BC) = 7.8+/-0.8 days, Delta_t(BD) = -6.5+/-0.7 days and
Delta_t_CD = -14.3+/-0.8 days. We spacially deconvolved HST NICMOS2 F160W
images to derive accurate astrometry of the quasar images and to infer the
light profile of the lensing galaxy. We combined these images with a stellar
population fitting of a deep VLT spectrum of the lensing galaxy to estimate the
baryonic fraction, $f_b$, in the Einstein radius. We measured f_b =
0.65+0.13-0.10 if the lensing galaxy has a Salpeter IMF and f_b =
0.45+0.04-0.07 if it has a Kroupa IMF. The spectrum also allowed us to estimate
the velocity dispersion of the lensing galaxy, sigma_ap = 222+/-34 km/s. We
used f_b and sigma_ap to constrain an analytical model of the lensing galaxy
composed of an Hernquist plus generalized NFW profile. We solve the Jeans
equations numerically for the model and explored the parameter space under the
additional requirement that the model must predict the correct astrometry for
the quasar images. Given the current error bars on f_b and sigma_ap, we did not
constrain H0 yet with high accuracy, i.e., we found a broad range of models
with chi^2 < 1. However, narrowing this range is possible, provided a better
velocity dispersion measurement becomes available. In addition, increasing the
depth of the current HST imaging data of HE 0435-1223 will allow us to combine
our constraints with lens reconstruction techniques that make use of the full
Einstein ring that is visible in this object. | The Opacity of Galactic Disks at z~0.7: We compare the surface brightness-inclination relation for a sample of COSMOS
pure disk galaxies at z~0.7 with an artificially redshifted sample of SDSS
disks well matched to the COSMOS sample in terms of rest-frame photometry and
morphology, as well as their selection and analysis. The offset between the
average surface brightness of face-on and edge-on disks in the redshifted SDSS
sample matches that predicted by measurements of the optical depth of galactic
disks in the nearby universe. In contrast, large disks at z~0.7 have a
virtually flat surface brightness-inclination relation, suggesting that they
are more opaque than their local counterparts. This could be explained by
either an increased amount of optically thick material in disks at higher
redshift, or a different spatial distribution of the dust. |
Constraints on Lepton Asymmetry from Nucleosynthesis in a Linearly
Coasting Cosmology: We study the effect of neutrino degeneracy on primordial nucleosynthesis in a
universe in which the cosmological scale factor evolves linearly with time. The
degeneracy parameter of electron type neutrinos ($\xi_e$) determines the $n/p$
(neutron to proton) ratio, which in turn determines the abundance of $^4$He in
a manner quite distinct from the Standard Scenario. The observed abundances of
$^4$He, $\mathrm{Y}_P$=0.254$\pm$0.003, and the minimum metallicity that is
essential for fragmentation and cooling processes in star forming prestellar
gas clouds (Z = Z$_{cr}$ = 10$^{-6}$Z$_\odot$), constrain the baryon to photon
ratio, $\eta_B$=(3.927$\pm$0.292)10$^{-9}$, corresponding to a baryonic matter
density, $\Omega_B$=0.263$\pm$ 0.026 and $\xi_e$=-2.165$\pm$0.171. This closes
the dynamic mass estimates of matter in the universe by baryons alone. Useful
byproducts are the threshold X(CNO) abundances required to trigger the CNO
cycle in the observed low metallicity stars in the universe. | Prospects of constraining reionization model parameters using Minkowski
tensors and Betti numbers: We explore the possibility of constraining model parameters of the Epoch of
Reionization (EoR) from 21cm brightness temperature maps, using a combination
of morphological descriptors constructed from the eigenvalues of the Contour
Minkowski Tensor (CMT), Betti numbers (count of connected regions $n_{con}$ and
holes $n_{hole}$) and the area of structures in the excursion set of the field.
We use a three parameter model of EoR simulated using 21\textrm{cmFAST}, namely
the ionizing efficiency of sources $\zeta$, the minimum virial temperature
$T_{vir}$ required for collapse into a halo and the maximum radius for ionizing
radiation described by $R_{mfp}$. We performed a Bayesian analysis to recover
model parameters for a mock 21cm image from SKA phase I at a redshift of
$z=7.4$ corresponding to a mean neutral hydrogen fraction of $\mathrm{\bar
x}_{HI} \simeq 0.5$. We find that in the absence of noise the average size of
structures in the field with $x_{HI} \lesssim 0.5$ is smaller than regions with
$x_{HI} \gtrsim 0.5$ and the structures are equally isotropic when
$\mathrm{\bar x}_{HI}=0.5$ . We also find that in order to recover the input
model to within $1-\sigma$ accuracy for a mock noisy image at a single
frequency channel of $1~\mathrm{MHz}$, for an observation time
$t_{obs}<2000~\mathrm{hrs}$, the noisy $\delta T_b$ map needs to be smoothed at
a scale $R_s>9.5~\mathrm{Mpc}$. Finally we show that the systematic behaviour
of the statistic as ionization progresses, enables us to obtain stringent
constraints on $\mathrm{\bar x}_{HI}$ (with a coefficient of variation $\sim
0.05$ as compared to $\sim 0.1-0.2$ for model parameter constraints), thereby
making these descriptors a promising statistic for constraining EoR model
parameters and the ionization history of the universe. |
Broad Brush Cosmos: An innovative approach to map the large-scale structure in the Universe
sidesteps the conventional need to observe millions of galaxies individually,
and holds promise for both astrophysical and cosmological studies. | Cosmology with gravitationally lensed repeating Fast Radio Bursts: High-precision cosmological probes have revealed a small but significant
tension between the parameters measured with different techniques, among which
there is one based on time delays in gravitational lenses. We discuss a new way
of using time delays for cosmology, taking advantage of the extreme precision
expected for lensed fast radio bursts (FRBs), which are short flashes of radio
emission originating at cosmological distances. With coherent methods, the
achievable precision is sufficient for measuring how time delays change over
the months and years, which can also be interpreted as differential redshifts
between the images. It turns out that uncertainties arising from the unknown
mass distribution of gravitational lenses can be eliminated by combining time
delays with their time derivatives. Other effects, most importantly relative
proper motions, can be measured accurately and disentangled from the
cosmological effects. With a mock sample of simulated lenses, we show that it
may be possible to attain strong constraints on cosmological parameters.
Finally, the lensed images can be used as galactic interferometer to resolve
structures and motions of the burst sources with incredibly high resolution and
help reveal their physical nature, which is currently unknown. |
Curvature Constraints from the Causal Entropic Principle: Current cosmological observations indicate a preference for a cosmological
constant that is drastically smaller than what can be explained by conventional
particle physics. The Causal Entropic Principle (Bousso, {\it et al}.) provides
an alternative approach to anthropic attempts to predict our observed value of
the cosmological constant by calculating the entropy created within a causal
diamond. We have extended this work to use the Causal Entropic Principle to
predict the preferred curvature within the "multiverse". We have found that
values larger than $\rho_k = 40\rho_m$ are disfavored by more than 99.99% and a
peak value at $\rho_{\Lambda} = 7.9 \times 10^{-123}$ and $\rho_k =4.3 \rho_m$
for open universes. For universes that allow only positive curvature or both
positive and negative curvature, we find a correlation between curvature and
dark energy that leads to an extended region of preferred values. Our universe
is found to be disfavored to an extent depending the priors on curvature. We
also provide a comparison to previous anthropic constraints on open universes
and discuss future directions for this work. | On the anisotropic distribution of clusters in the local Universe: In his 2021 lecture to the Canadian Association of Physicists Congress,
P.J.E. Peebles pointed out that the brightest extra-galactic radio sources tend
to be aligned with the plane of the de Vaucouleur Local Supercluster up to
redshifts of $z=0.02$ ($d_{\rm MW}\approx 85~\rm{Mpc}$). He then asked whether
such an alignment of clusters is anomalous in the standard $\Lambda$CDM
framework. In this letter, we employ an alternative, absolute orientation
agnostic, measure of the anisotropy based on the inertia tensor axis ratio of
these brightest sources and use a large cosmological simulation from the
FLAMINGO suite to measure how common such an alignment of structures is. We
find that only 3.5% of randomly selected regions display an anisotropy of their
clusters more extreme than the one found in the local Universe's radio data.
This sets the region around the Milky Way as a $1.85\sigma$ outlier. Varying
the selection parameters of the objects in the catalogue, we find that the
clusters in the local Universe are never more than $2\sigma$ away from the
simulations' prediction for the same selection. We thus conclude that the
reported anisotropy, whilst note-worthy, is not in tension with the
$\Lambda$CDM paradigm. |
Intensity Mapping of Lyman-alpha Emission During the Epoch of
Reionization: We calculate the absolute intensity and anisotropies of the Lyman-alpha
radiation field present during the epoch of reionization. We consider emission
from both galaxies and the intergalactic medium (IGM) and take into account the
main contributions to the production of Lyman-alpha photons: recombinations,
collisions, continuum emission from galaxies and scattering of Lyman-n photons
in the IGM. We find that the emission from individual galaxies dominates over
the IGM with a total Lyman-alpha intensity (times frequency) of about
(1.43-3.57)x10^{-8} erg s^{-1} cm^{-2} sr^{-1} at a redshift of 7. This
intensity level is low so it is unlikely that the Lyman-\alpha background
during reionization can be established by an experiment aiming at an absolute
background light measurement. Instead we consider Lyman-\alpha intensity
mapping with the aim of measuring the anisotropy power spectrum which has rms
fluctuations at the level of 1 x 10^{-16} [erg s^[-1} cm^{-2} sr^{-1}]^2 at a
few Mpc scales. These anisotropies could be measured with a spectrometer at
near-IR wavelengths from 0.9 to 1.4 \mu m with fields in the order of 0.5 to 1
sq. degrees. We recommend that existing ground-based programs using narrow band
filters also pursue intensity fluctuations to study statistics on the spatial
distribution of faint Lyman-\alpha emitters. We also discuss the
cross-correlation signal with 21 cm experiments that probe HI in the IGM during
reionization. A dedicated sub-orbital or space-based Lyman-\alpha intensity
mapping experiment could provide a viable complimentary approach to probe
reionization, when compared to 21 cm experiments, and is likely within
experimental reach. | Constraining Cosmological Phase Transitions with Chinese Pulsar Timing
Array Data Release 1: The Chinese Pulsar Timing Array (CPTA) collaboration has recently reported
the observational evidence of a stochastic gravitational wave background. In
light of the latest CPTA observation, we aim at exploring the ability of CPTA
in probing new physics. Specifically, we constrain the first-order cosmological
phase transitions with CPTA data, and find that the constraining result is
slightly tighter than that of NANOGrav's 12.5-yr data but weaker than
NANOGrav's 15-yr data. Considering the possible complexity of gravitational
wave sources, we give the constraint on a mixed scenario of cosmological phase
transitions and astrophysical supermassive binary black holes. Our analysis
suggests that CPTA has a great potential to probe fundamental physics in the
near future. |
[O III] Equivalent Width and Orientation Effects in Quasars: The flux of the [OIII] line is considered to be a good indicator of the
bolometric emission of quasars. The observed continuum emission from the
accretion disc should instead be strongly dependent on the inclination angle
theta between the disc axis and the line of sight. Based on this, the
equivalent width (EW) of [OIII] should provide a direct measure of theta. Here
we analyze the distribution of EW([OIII]) in a sample of ~6,000 SDSS quasars,
and find that it can be accurately reproduced assuming a relatively small
intrinsic scatter and a random distribution of inclination angles. This result
has several implications: 1) it is a direct proof of the disc-like emission of
the optical continuum of quasars; 2) the value of EW([OIII]) can be used as a
proxy of the inclination, to correct the measured continuum emission and then
estimate the bolometric luminosity of quasars; 3) the presence of almost
edge-on discs among broad line quasars implies that the accretion disc is not
aligned with the circumnuclear absorber, and/or that the covering fraction of
the latter is rather small. Finally, we show that a similar analysis of EW
distributions of broad lines (Hbeta, Mg II, C IV) provides no evidence of
inclination effects, suggesting a disc-like geometry of the broad emission line
region. | Full-sky Cosmic Microwave Background Foreground Cleaning Using Machine
Learning: In order to extract cosmological information from observations of the
millimeter and submillimeter sky, foreground components must first be removed
to produce an estimate of the cosmic microwave background (CMB). We developed a
machine-learning approach for doing so for full-sky temperature maps of the
millimeter and submillimeter sky. We constructed a Bayesian spherical
convolutional neural network architecture to produce a model that captures both
spectral and morphological aspects of the foregrounds. Additionally, the model
outputs a per-pixel error estimate that incorporates both statistical and model
uncertainties. The model was then trained using simulations that incorporated
knowledge of these foreground components that was available at the time of the
launch of the Planck satellite. On simulated maps, the CMB is recovered with a
mean absolute difference of $<4\mu$K over the full sky after masking map pixels
with a predicted standard error of $>50\mu$K; the angular power spectrum is
also accurately recovered. Once validated with the simulations, this model was
applied to Planck temperature observations from its 70GHz through 857GHz
channels to produce a foreground-cleaned CMB map at a Healpix map resolution of
NSIDE=512. Furthermore, we demonstrate the utility of the technique for
evaluating how well different simulations match observations, particularly in
regard to the modeling of thermal dust. |
Primordial Non-Gaussianity and Extreme-Value Statistics of Galaxy
Clusters: What is the size of the most massive object one expects to find in a survey
of a given volume? In this paper, we present a solution to this problem using
Extreme-Value Statistics, taking into account primordial non-Gaussianity and
its effects on the abundance and the clustering of rare objects. We calculate
the probability density function (pdf) of extreme-mass clusters in a survey
volume, and show how primordial non-Gaussianity shifts the peak of this pdf. We
also study the sensitivity of the extreme-value pdfs to changes in the mass
functions, survey volume, redshift coverage and the normalization of the matter
power spectrum, {\sigma}_8. For 'local' non-Gaussianity parametrized by f_NL,
our correction for the extreme-value pdf due to the bias is important when f_NL
> O(100), and becomes more significant for wider and deeper surveys. Applying
our formalism to the massive high-redshift cluster XMMUJ0044.0-2-33, we find
that its existence is consistent with f_NL = 0, although the conclusion is
sensitive to the assumed values of the survey area and {\sigma}_8. We also
discuss the convergence of the extreme-value distribution to one of the three
possible asymptotic forms, and argue that the convergence is insensitive to the
presence of non-Gaussianity. | Electrodynamic effect of anisotropic expansions in the Universe: In the presence of anisotropic cosmic expansions at global or local scale the
equations of electrodynamics in expanding space-time are modified and presented
here. A new effect should arise in regions of local anisotropic expansion in a
cosmologically isotropic background. These regions should naturally exist,
being connected with scales decoupling from the Hubble flow. Possible
observational consequences of this effect are suggested. In particular, I
predict the appearance or variation of the polarization of electromagnetic
radiation coming from or passing through these regions. This effect is
observable and possibly already observed in the polarization of quasars. |
Deprojected analysis of Abell 1835 observed with Chandra and compared
with XMM-Newton: Using a deprojection technique, we study the X-ray properties of the galaxy
cluster Abell 1835 observed with Chandra, including temperature, abundance,
electron density, gas mass fraction, and total mass. A comparison with the
results without deprojection shows that the properties do not change much. When
we compare the results with those of XMM-Newton, the difference between the
temperature profiles derived from Chandra and XMM-Newton data still exists,
even if the point-spread function effect of XMM-Newton is corrected. To
investigate the reasons for the difference, we used the spectra to
cross-calibrate the temperatures. They show that the Chandra spectra can be
fitted well with XMM-Newton temperatures. Furthermore, we derive the electron
density profile from Chandra data with XMM-Newton temperatures and calculate
the projected mass, which is consistent with the XMM-Newton mass and a little
lower than the weak lensing mass at r_500. Thus, it seems that the temperature
derived from XMM-Newton may be more reliable. | Response approach to the integrated shear 3-point correlation function:
the impact of baryonic effects on small scales: The integrated shear 3-point correlation function $\zeta_{\pm}$ is a
higher-order statistic of the cosmic shear field that describes the modulation
of the 2-point correlation function $\xi_{\pm}$ by long-wavelength features in
the field. Here, we introduce a new theoretical model to calculate
$\zeta_{\pm}$ that is accurate on small angular scales, and that allows to take
baryonic feedback effects into account. Our model builds on the realization
that the small-scale $\zeta_{\pm}$ is dominated by the nonlinear matter
bispectrum in the squeezed limit, which can be evaluated accurately using the
nonlinear matter power spectrum and its first-order response functions to
density and tidal field perturbations. We demonstrate the accuracy of our model
by showing that it reproduces the small-scale $\zeta_{\pm}$ measured in
simulated cosmic shear maps. The impact of baryonic feedback enters effectively
only through the corresponding impact on the nonlinear matter power spectrum,
thereby permitting to account for these astrophysical effects on $\zeta_{\pm}$
similarly to how they are currently accounted for on $\xi_{\pm}$. Using a
simple idealized Fisher matrix forecast for a DES-like survey we find that,
compared to $\xi_{\pm}$, a combined $\xi_{\pm}\ \&\ \zeta_{\pm}$ analysis can
lead to improvements of order $20-40\%$ on the constraints of cosmological
parameters such as $\sigma_8$ or the dark energy equation of state parameter
$w_0$. We find similar levels of improvement on the constraints of the baryonic
feedback parameters, which strengthens the prospects for cosmic shear data to
obtain tight constraints not only on cosmology but also on astrophysical
feedback models. These are encouraging results that motivate future works on
the integrated shear 3-point correlation function towards applications to real
survey data. |
A Precise Cluster Mass Profile Averaged from the Highest-Quality Lensing
Data: We outline our methods for obtaining high precision mass profiles, combining
independent weak-lensing distortion, magnification, and strong-lensing
measurements. For massive clusters the strong and weak lensing regimes
contribute equal logarithmic coverage of the radial profile. The utility of
high-quality data is limited by the cosmic noise from large scale structure
along the line of sight. This noise is overcome when stacking clusters, as too
are the effects of cluster asphericity and substructure, permitting a stringent
test of theoretical models. We derive a mean radial mass profile of four
similar mass clusters of high-quality HST and Subaru images, in the range
R=40kpc/h to 2800kpc/h, where the inner radial boundary is sufficiently large
to avoid smoothing from miscentering effects. The stacked mass profile is
detected at 58-sigma significance over the entire radial range, with the
contribution from the cosmic noise included. We show that the projected mass
profile has a continuously steepening gradient out to beyond the virial radius,
in remarkably good agreement with the standard Navarro-Frenk-White form
predicted for the family of CDM-dominated halos in gravitational equilibrium.
The central slope is constrained to lie in the range,
-dln{\rho}/dln{r}=0.89^{+0.27}_{-0.39}. The mean concentration is
c_{vir}=7.68^{+0.42}_{-0.40} (at a mean virial mass 1.54^{+0.11}_{-0.10}\times
10^{15} M_{sun}/h), which is high for relaxed, high-mass clusters, but
consistent with LCDM when a sizable projection bias estimated from N-body
simulations is considered. This possible tension will be more definitively
explored with new cluster surveys, such as CLASH, LoCuSS, Subaru HSC, and
XXM-XXL, to construct the c-M relation over a wider mass range. | Impact of galactic distributions in celestial capture of dark matter: Celestial capture of dark matter provides a useful handle for constraining
its particulate properties. The capture formalism is sensitive to the phase
space distribution of dark matter in the vicinity of the celestial object. This
article aims to systematically study the impact of uncertainties and the
influence of cosmological simulations on the rate at which dark matter
particles are captured inside a variety of celestial objects. Going beyond the
framework of the Maxwell-Boltzmann distribution or the standard halo model, we
take up pragmatic dark matter velocity distributions motivated by observations
or cosmological simulations. Within the limits of the standard halo model, we
report a maximum $\sim 20\%$ change in the capture rate. This number can go up
to $\sim 200\%$ if dark matter particles within the galactic halo are favored
to have an empirical velocity distribution profile when well-resolved and
sophisticated cosmological simulations are employed to extract their parametric
values. |
Perturbation Theory of the Cosmological Log-Density Field: The matter density field exhibits a nearly lognormal probability density
distribution (PDF) after entering into the nonlinear regime. Recently, it has
been shown that the shape of the power spectrum of a logarithmically
transformed density field is very close to the linear density power spectrum,
motivating an analytic study of it. In this paper, we develop cosmological
perturbation theory for the power spectrum of this field. Our formalism is
developed in the context of renormalized perturbation theory, which helps to
regulate the convergence behavior of the perturbation series, and of the
Taylor- series expansion we use of the logarithmic mapping. This approach
allows us to handle the critical issue of density smoothing in a
straightforward way. We also compare our perturbative results with simulation
measurements. | Synchrotron emission and neutral hydrogen in the simulated cosmic web: We present the first results of a campaign of ENZO cosmological simulations
targeting the shocked and the neutral parts of the cosmic web, obtained with
Supercomputing facilities provided by the INAF-CINECA agreement. |
Needlet Bispectrum Asymmetries in the WMAP 5-year Data: We apply the needlet formalism to the Wilkinson Microwave Anisotropy Probe
5-year data, looking for evidence of non-Gaussianity in the bispectrum of the
needlet amplitudes. We confirm earlier findings of an asymmetry in the
non-Gaussianity between the northern and southern galactic hemispheres. We
attempt to isolate which scales and geometrical configurations are most
anomalous, and find the bispectrum is most significant on large scales and in
the more co-linear configurations, and also in the `squeezed' configurations.
However, these anomalies do not appear to affect the estimate of the non-linear
parameter $\fnl$, and we see no significant difference between its value
measured in the two hemispheres. | Mapping Spatially Varying Additive Biases in Cosmic Shear Data: In this paper we address the challenge of extracting maps of spatially
varying unknown additive biases from cosmic shear data. This is done by
exploiting the isotropy of the cosmic shear field, and the anisotropy of a
typical additive bias field, using an autocorrelation discrepancy map; which
identifies significant non-Gaussian components of the map. We test this
approach using simulations and find that the autocorrelation discrepancy map
produces spatially varying features that are indicative of the additive bias
field both in amplitude and spatial variation. We then apply this to the Dark
Energy Survey Year 1 data, and find evidence for spatially varying additive
biases of at most 0.002 on large-scales. The method can be used to empirically
inform modelling of the spatially varying additive bias field in any
cosmological parameter inference, and can act as a validation test for cosmic
shear surveys. |
Radio Planetary Nebulae in the Magellanic Clouds: We present preliminary results of our deep Australia Telescope Compact Array
(ATCA) radio-continuum survey of the Magellanic Clouds Planetary Nebulae. | Reconciling low multipole anomalies and reheating in single field
inflationary models: Reheating phase of inflationary Universe can be modeled by parameters
$T_{\text{reh}}$, $\bar{w}_{\text{reh}}$ and $N_{\text{reh}}$, which can be
constrained by the scalar spectral amplitude $A_{s}$ and the scalar spectral
index $n_{s}$. On the other hand the low multipole anomalies in the CMB can be
modeled by suitable features in the inflaton potential. We show that the
parameters of these features in the inflaton potential provide additional
constraints on the reheating parameters. For several single field models we
find that the reheating parameters are substantially more constrained by the
requirement of compatibility with the proposed explanation for low multipole
anomalies. |
Galilean invariance and the consistency relation for the nonlinear
squeezed bispectrum of large scale structure: We discuss the constraints imposed on the nonlinear evolution of the Large
Scale Structure (LSS) of the universe by galilean invariance, the symmetry
relevant on subhorizon scales. Using Ward identities associated to the
invariance, we derive fully nonlinear consistency relations between statistical
correlators of the density and velocity perturbations, such as the power
spectrum and the bispectrum. These relations are valid up to O (f_{NL}^2)
corrections. We then show that most of the semi-analytic methods proposed so
far to resum the perturbative expansion of the LSS dynamics fail to fulfill the
constraints imposed by galilean invariance, and are therefore susceptible to
non-physical infrared effects. Finally, we identify and discuss a
nonperturbative semi-analytical scheme which is manifestly galilean invariant
at any order of its expansion. | Modeling the neutral hydrogen distribution in the post-reionization
Universe: intensity mapping: We model the distribution of neutral hydrogen (HI) in the post-reionization
era and investigate its detectability in 21 cm intensity mapping with the
future SKA radio telescope. We rely on high resolution hydrodynamical N-body
simulations. The HI is assigned a-posteriori to the gas particles following two
different approaches: a halo-based method in which HI is assigned only to gas
particles residing within dark matter halos; a particle-based method that
assigns HI to all gas particles using a prescription based on the physical
properties of the particles. The HI statistical properties are then compared to
the observational properties of Damped Lyman-$\alpha$ Absorbers (DLAs) and of
lower column density systems and reasonable good agreement is found for all the
cases. Among the halo-based method, we further consider two different schemes
that aim at reproducing the observed properties of DLAs by distributing HI
inside halos: one of this results in a much higher bias for DLAs, in agreement
with recent observations, which boosts the 21 cm power spectrum by a factor
$\sim 4$ with respect to the other recipe. We compute the 21 cm power spectrum
from the simulated HI distribution and calculate the expected signal for both
SKA1-mid and SKA1-low configurations at $2.4 \leq z \leq 4$. We find that SKA
will be able to detect the 21 cm power spectrum, in the non-linear regime, up
to $k\sim 1\,h$/Mpc for SKA1-mid and $k\sim 5\,h$/Mpc for SKA1-low with 100
hours of observations. We also investigate the perspective of imaging the HI
distribution. Our findings indicate that SKA1-low could detect the most massive
HI peaks with a signal to noise ratio (SNR) higher than 5 for an observation
time of about 1000 hours at $z=4$, for a synthesized beam width of $2'$.
Detection at redshifts $z\geqslant2.4$ with SKA1-mid would instead require a
much longer observation time to achieve a comparable SNR level. |
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. | Search for Compensated Isocurvature Perturbations with Planck Power
Spectra: In the standard inflationary scenario, primordial perturbations are
adiabatic. The amplitudes of most types of isocurvature perturbations are
generally constrained by current data to be small. If, however, there is a
baryon-density perturbation that is compensated by a dark-matter perturbation
in such a way that the total matter density is unperturbed, then this
compensated isocurvature perturbation (CIP) has no observable consequence in
the cosmic microwave background (CMB) at linear order in the CIP amplitude.
Here we search for the effects of CIPs on CMB power spectra to quadratic order
in the CIP amplitude. An analysis of the Planck temperature data leads to an
upper bound $\Delta_{\rm rms}^2 \leq 7.1\times 10^{-3}$, at the 68\% confidence
level, to the variance $\Delta_{\rm rms}^2$ of the CIP amplitude. This is then
strengthened to $\Delta_{\rm rms}^2\leq 5.0\times 10^{-3}$ if Planck
small-angle polarization data are included. A cosmic-variance-limited CMB
experiment could improve the $1\sigma$ sensitivity to CIPs to $\Delta^2_{\rm
rms} \lesssim 9\times 10^{-4}$. It is also found that adding CIPs to the
standard $\Lambda$CDM model can improve the fit of the observed smoothing of
CMB acoustic peaks just as much as adding a non-standard lensing amplitude. |
Three-dimensional magnetohydrodynamic simulations of the evolution of
magnetic fields in Fanaroff-Riley class II radio sources: Radio observations of Fanaroff-Riley class II sources often show correlations
between the synchrotron emission and the linear-polarimetric distributions.
Magnetic position vectors seem to align with the projected emission of both the
radio jets and the sources' edges. Using statistics we study such relation as
well as its unknown time evolution via synthetic polarisation maps of model FR
II sources formed in 3D-MHD numerical simulations of bipolar, hypersonic and
weakly magnetised jets. The magnetic field is initially random with a
Kolmogorov power spectrum, everywhere. We investigate the structure and
evolution of magnetic fields in the sources as a function of the power of jets
and the observational viewing angle. Our synthetic polarisation maps agree with
observations, showing B-field vectors which are predominantly aligned with the
jet axis, and show that magnetic fields inside sources are shaped by the jets'
backflow. Polarimetry is found to correlate with time, the viewing angle and
the jet-to-ambient density contrast. The magnetic structure inside thin
elongated sources is more uniform than inside more spherical ones. We see jets
increase the magnetic energy in cocoons in proportion to the jet velocity and
the cocoon width. Filaments in the synthetic emission maps suggest turbulence
develops in evolved sources. | The Weak Lensing Peak Statistics in the Mocks by the
inverse-Gaussianization Method: We apply the inverse-Gaussianization method proposed in
\citealt{arXiv:1607.05007} to fast produce weak lensing convergence maps and
investigate the peak statistics, including the peak height counts and peak
steepness counts, in these mocks. We find that the distribution of peak height
and steepness is in good agreement with the simulation. The difference is
$\lesssim 20\%$ for these peak statistics in the maps at source redshift
$z_s=1$. Besides, the loss of off-diagonal elements in peak covariance
motivates us to consider the super sample variance in weak lensing peak
statistics. We propose correction methods to effectively recover the
(anti-)correlation among different bins by adding scatters in the mean value of
these mocks. Finally, as an example of the application, we adopt the improved
inverse-Gaussianization method with the above improvement to fast generate
40,000 mocks to calculate precision matrices between the power spectrum and
peak statistics. |
AMICO galaxy clusters in KiDS-DR3: measuring the splashback radius from
weak gravitational lensing: Context. Weak gravitational lensing offers a powerful method to investigate
the projected matter density distribution within galaxy clusters, granting
crucial insights into the broader landscape of dark matter on cluster scales.
Aims. In this study, we make use of the large photometric galaxy cluster data
set derived from the publicly available Third Data Release of the Kilo-Degree
Survey, along with the associated shear signal. Our primary objective is to
model the peculiar sharp transition in the cluster profile slope, i.e. what is
commonly referred to as the splashback radius. The data set under scrutiny
includes 6962 galaxy clusters, selected by AMICO on the KiDS-DR3 data, in the
redshift range of 0.1 < z < 0.6, all observed at signal-to-noise ratio greater
than 3.5. Methods. Employing a comprehensive Bayesian analysis, we model the
stacked excess surface mass density distribution of the clusters. We adopt a
model from recent results on numerical simulations, that captures the dynamics
of both orbiting and infalling materials, separated by the region where the
density profile slope undergoes a pronounced deepening. Results. We find that
the adopted profile successfully characterizes the cluster masses, consistent
with previous works, and models the deepening of the slope of the density
profiles measured with weak-lensing data up to the outskirts. Moreover, we
measure the splashback radius of galaxy clusters and show that its value is
close to the radius within which the enclosed overdensity is 200 times the mean
matter density of the Universe, while theoretical models predict a larger value
consistent with a low accretion rate. This points to a potential bias of
optically selected clusters that are preferentially characterized by a high
density at small scales compared to a pure mass-selected cluster sample. | Redshifted 21-cm emission signal from the halos in Dark Ages: The emission in the hyperfine structure 21 cm line of atomic hydrogen arising
in the halos with masses $\sim10^6-10^{10}$ M$_\odot$ from the Dark Ages in the
models with Warm Dark Matter (WDM) is analysed. The halos are assumed to be
formed from Gaussian density peaks of cosmological density perturbations at
$10\lesssim z\lesssim50$. Semi-analytical modelling of the formation of
individual spherical halos in multi-component models shows that gas in them has
the kinetic temperature in the range of $60-800$ K under adiabatic compression
of the collapsing halo, and the temperature of each halo depends on the time of
virialization. It is shown that inelastic collisions between neutral hydrogen
atoms are the dominant excitation mechanism for hyperfine structure levels,
which pulls the spin temperature closer to the kinetic temperature. The
brightness temperature of individual halos is in the range of 1-10 K, depending
on the mass of the halo and its virialization redshift, and increasing as these
two increase. The apparent angular radii of such halos are in the range
0.06-1.2 arcseconds, their surface number density decreasing exponentially from
a few per arcmin$^2$ for the lowest mass and redshift to nearly zero for higher
values. Assuming a 1 MHz observation bandwidth the surface number density of
the halo at various redshifts is evaluated as well as beam-averaged
differential antenna temperatures and fluxes of hydrogen emission from halos of
different masses. The beam-averaged signal strongly depends on the cut-off
scale in the mass function of dark ages halos that may be caused by
free-streaming of WDM particles. The finding is compared with the upper limits
on the amplitude of the power spectrum of the hydrogen 21-cm line fluctuations
derived from the recent observation data obtained with MWA and LOFAR. |
Evolution of cosmic filaments and of their galaxy population from MHD
cosmological simulations: Despite containing about a half of the total matter in the Universe, at most
wavelengths the filamentary structure of the cosmic web is difficult to
observe. In this work, we use large unigrid cosmological simulations to
investigate how the geometrical, thermodynamical and magnetic properties of
cosmological filaments vary with mass and redshift (z $\leq 1$). We find that
the average temperature, length, volume and magnetic field of filaments are
tightly log-log correlated with the underlying total gravitational mass. This
reflects the role of self-gravity in shaping their properties and enables
statistical predictions of their observational properties based on their mass.
We also focus on the properties of the simulated population of galaxy-sized
halos within filaments, and compare their properties to the results obtained
from the spectroscopic GAMA survey. Simulated and observed filaments with the
same length are found to contain an equal number of galaxies, with very similar
distribution of halo masses. The total number of galaxies within each filament
and the total/average stellar mass in galaxies can now be used to predict also
the large-scale properties of the gas in the host filaments across tens or
hundreds of Mpc in scale. These results are the first steps towards the future
use of galaxy catalogues in order to select the best targets for observations
of the warm-hot intergalactic medium. | First Simulations of Axion Minicluster Halos: We study the gravitational collapse of axion dark matter fluctuations in the
post-inflationary scenario, so-called axion miniclusters, with N-body
simulations. Largely confirming theoretical expectations, overdensities begin
to collapse in the radiation-dominated epoch and form an early distribution of
miniclusters with masses up to $10^{-12}\,M_\odot$. After matter-radiation
equality, ongoing mergers give rise to a steep power-law distribution of
minicluster halo masses. The density profiles of well-resolved halos are
NFW-like to good approximation. The fraction of axion dark matter in these
bound structures is $\sim 0.75$ at redshift $z=100$. |
Recovering 3D clustering information with angular correlations: We study how to recover the full 3D clustering information of P(\vec{k},z),
including redshift space distortions (RSD), from 2D tomography using the
angular auto and cross spectra of different redshift bins C_\ell(z,z'). We
focus on quasilinear scales where the minimum scale \lambda_{min} or
corresponding maximum wavenumber k_{max}= 2\pi/\lambda_{min} is targeted to be
between k_{max}={0.05-0.2} h/Mpc. For spectroscopic surveys, we find that we
can recover the full 3D clustering information when the redshift bin width
\Delta z used in the 2D tomography is similar to the targeted minimum scale,
i.e. \Delta z ~ {0.6-0.8} \lambda_{min} H(z)/c which corresponds to \Delta z ~
0.01-0.05 for z<1. This value of \Delta z is optimal in the sense that larger
values of \Delta z lose information, while smaller values violate our minimum
scale requirement. For a narrow-band photometric survey, with photo-z error
\sigma_z=0.004, we find almost identical results to the spectroscopic survey
because the photo-z error is smaller than the optimal bin width \sigma_z<\Delta
z. For a typical broad-band photometric survey with \sigma_z=0.1, we have that
\sigma_z>\Delta z and most radial information is intrinsically lost. The
remaining information can be recovered from the 2D tomography if we use \Delta
z ~ 2\sigma_z. While 3D and 2D analysis are shown here to be equivalent, the
advantage of using angular positions and redshifts is that we do not need a
fiducial cosmology to convert to 3D coordinates. This avoids assumptions and
marginalization over the fiducial model. In addition, it becomes straight
forward to combine RSD, clustering and weak lensing in 2D space. | The Metric of the Cosmos from Luminosity and Age Data: This paper presents the algorithm for determining the Lemaitre-Tolman (LT)
model that best fits given datasets for maximum stellar ages, and SNIa
luminosities, both as functions of redshift. It then applies it to current
cosmological data. Special attention must be given to the handling of the
origin, and the region of the maximum diameter distances. As with a previous
combination of datasets (galaxy number counts and luminosity distances versus
redshift), there are relationships that must hold at the region of the maximum
diameter distance, which are unlikely to be obeyed exactly by real data. We
show how to make corrections that enable a self-consistent solution to be
found. We address the questions of the best way to approximate discrete data
with smooth functions, and how to estimate the uncertainties of the output -
the 3 free functions that determine a specific LT metric. While current data
does not permit any confidence in our results, we show that the method works
well, and reasonable LT models do fit with or without a cosmological constant. |
Constraints on a scale-dependent bias from galaxy clustering: We forecast the future constraints on scale-dependent parametrizations of
galaxy bias and their impact on the estimate of cosmological parameters from
the power spectrum of galaxies measured in a spectroscopic redshift survey. For
the latter we assume a wide survey at relatively large redshifts, similar to
the planned Euclid survey, as baseline for future experiments. To assess the
impact of the bias we perform a Fisher matrix analysis and we adopt two
different parametrizations of scale-dependent bias. The fiducial models for
galaxy bias are calibrated using a mock catalogs of H$\alpha$ emitting galaxies
mimicking the expected properties of the objects that will be targeted by the
Euclid survey.
In our analysis we have obtained two main results. First of all, allowing for
a scale-dependent bias does not significantly increase the errors on the other
cosmological parameters apart from the rms amplitude of density fluctuations,
$\sigma_{8}$, and the growth index $\gamma$, whose uncertainties increase by a
factor up to two, depending on the bias model adopted. Second, we find that the
accuracy in the linear bias parameter $b_{0}$ can be estimated to within 1-2\%
at various redshifts regardless of the fiducial model. The non-linear bias
parameters have significantly large errors that depend on the model adopted.
Despite of this, in the more realistic scenarios departures from the simple
linear bias prescription can be detected with a $\sim2\,\sigma$ significance at
each redshift explored.
Finally, we use the Fisher Matrix formalism to assess the impact of assuming
an incorrect bias model and found that the systematic errors induced on the
cosmological parameters are similar or even larger than the statistical ones. | The zCOSMOS survey: the role of the environment in the evolution of the
luminosity function of different galaxy types: (Abridged) We studied the evolution in the B band luminosity function to z~1
in the zCOSMOS 10k sample, for which both accurate galaxy classifications and a
detailed description of the local density field are available.
The global LF exhibits a brightening of ~0.7 mag in M* from z~0.2 to z~0.9.
At low z, late types dominate at faint magnitudes, while the bright end is
populated mainly by early types. At higher z, late-type galaxies evolve
significantly and, at z~1, the contribution from the various types to the
bright end of the LF is comparable. The evolution for early types is in both
luminosity and normalization. A similar behaviour is exhibited by late types,
but with an opposite trend for the normalization. Studying the role of the
environment, we find that the global LF of galaxies in overdense regions has
always a brighter M* and a flatter slope. In low density environments, the main
contribution to the LF is from blue galaxies, while for high density
environments there is an important contribution from red galaxies to the bright
end. The differences between the global LF in the two environments are not due
to only a difference in the relative numbers of red and blue galaxies, but also
to their relative luminosity distributions: the value of M* for both types in
underdense regions is always fainter than in overdense environments.
The "specular" evolution of late- and early-type galaxies is consistent with
a scenario where a part of blue galaxies is transformed in red galaxies with
increasing cosmic time, without significant changes in the fraction of
intermediate-type galaxies. The bulk of this tranformation in overdense regions
probably happened before z~1, while it is still ongoing at lower z in
underdense environments. |
Breaking a Dark Degeneracy with Gravitational Waves: We identify a scalar-tensor model embedded in the Horndeski action whose
cosmological background and linear scalar fluctuations are degenerate with the
concordance cosmology. The model admits a self-accelerated background expansion
at late times that is stable against perturbations with a sound speed
attributed to the new field that is equal to the speed of light. While
degenerate in scalar fluctuations, self-acceleration of the model implies a
present cosmological tensor mode propagation at < 95% of the speed of light
with a damping of the wave amplitude that is > 5% less efficient than in
general relativity. We show that these discrepancies are endemic to
self-accelerated Horndeski theories with degenerate large-scale structure and
are tested with measurements of gravitational waves emitted by events at
cosmological distances. Hence, gravitational-wave cosmology breaks the dark
degeneracy in observations of the large-scale structure between two
fundamentally different explanations of cosmic acceleration - a cosmological
constant and a scalar-tensor modification of gravity. The gravitational wave
event GW150914 recently detected with the aLIGO instruments and its potential
association with a weak short gamma-ray burst observed with the Fermi GBM
experiment may have provided this crucial measurement. | Chemical evolution of the Large Magellanic Cloud: We adopt a new chemical evolution model for the Large Magellanic Cloud (LMC)
and thereby investigate its past star formation and chemical enrichment
histories. The delay time distribution of type Ia supernovae recently revealed
by type Ia supernova surveys is incorporated self-consistently into the new
model. The principle results are summarized as follows. The present gas mass
fraction and stellar metallicity as well as the higher [Ba/Fe] in metal-poor
stars at [Fe/H]<-1.5 can be more self-consistently explained by models with
steeper initial mass functions. The observed higher [Mg/Fe] (> 0.3) at [Fe/H] ~
-0.6 and higher [Ba/Fe] (>0.5) at [Fe/H] ~ -0.3 can be due to significantly
enhanced star formation about 2 Gyr ago. The observed overall [Ca/Fe]-[Fe/H]
relation and remarkably low [Ca/Fe] (<-0.2) at [Fe/H]>-0.6 are consistent with
models with short-delay supernova Ia and with the more efficient loss of Ca
possibly caused by an explosion mechanism of type II supernovae. Although the
metallicity distribution functions do not show double peaks in the models with
a starburst about 2 Gyr ago, they show characteristic double peaks in the
models with double starbursts at ~200 Myr and ~2 Gyr ago. The observed apparent
dip of [Fe/H] around ~1.5 Gyr ago in the age--metallicity relation can be
reproduced by models in which a large amount (~10^9 M_{sun}) of metal-poor
([Fe/H]<-1) gas can be accreted onto the LMC. |
The generation of strong magnetic fields during the formation of the
first stars: Cosmological hydrodynamical simulations of primordial star formation suggest
that the gas within the first star-forming halos is turbulent. This has strong
implications on the subsequent evolution, in particular on the generation of
magnetic fields. Using high-resolution numerical simulations, we show that in
the presence of turbulence, weak seed magnetic fields are exponentially
amplified by the small-scale dynamo during the formation of the first stars. We
conclude that strong magnetic fields are generated during the birth of the
first stars in the universe, potentially modifying the mass distribution of
these stars and influencing the subsequent cosmic evolution. We find that the
presence of the small-scale turbulent dynamo can only be identified in
numerical simulations in which the turbulent motions in the central core are
resolved with at least 32 grid cells. | Constraints on massive vector dark energy models from integrated
Sachs-Wolfe-galaxy cross-correlations: The gravitational-wave event GW170817, together with the electromagnetic
counterpart, shows that the speed of tensor perturbations $c_T$ on the
cosmological background is very close to that of light $c$ for the redshift
$z<0.009$. In generalized Proca theories, the Lagrangians compatible with the
condition $c_T=c$ are constrained to be derivative interactions up to cubic
order, besides those corresponding to intrinsic vector modes. We place
observational constraints on a dark energy model in cubic-order generalized
Proca theories with intrinsic vector modes by running the Markov chain Monte
Carlo (MCMC) code. We use the cross-correlation data of the integrated
Sachs-Wolfe (ISW) signal and galaxy distributions in addition to the data sets
of cosmic microwave background, baryon acoustic oscillations, type Ia
supernovae, local measurements of the Hubble expansion rate, and redshift-space
distortions. We show that, unlike cubic-order scalar-tensor theories, the
existence of intrinsic vector modes allows the possibility for evading the
ISW-galaxy anticorrelation incompatible with the current observational data. As
a result, we find that the dark energy model in cubic-order generalized Proca
theories exhibits a better fit to the data than the cosmological constant, even
by including the ISW-galaxy correlation data in the MCMC analysis. |
GAMA/H-ATLAS: The Dust Opacity - Stellar Mass Surface Density Relation
for Spiral Galaxies: We report the discovery of a well-defined correlation between B-band face-on
central optical depth due to dust, \tau^f_B, and the stellar mass surface
density, \mu_{*}, of nearby (z < 0.13) spiral galaxies: log(\tau^f_B) =
1.12(+-0.11)log(\mu_{*}/M_sol kpc^2)-8.6(+-0.8). This relation was derived from
a sample of spiral galaxies taken from the Galaxy and Mass Assembly (GAMA)
survey and detected in the FIR/submm in the Herschel-ATLAS survey. Using a
quantitative analysis of the NUV attenuation-inclination relation for complete
samples of GAMA spirals categorized according to \mu_{*} we demonstrate that
this correlation can be used to statistically correct for dust attenuation
purely on the basis of optical photometry and S'ersic-profile morphological
fits. Considered together with previously established empirical relationships
between stellar mass, metallicity and gas mass, the near linearity and high
constant of proportionality of the \tau^f_B-\mu_{*} relation disfavors a
stellar origin for the bulk of refractory grains in spiral galaxies, instead
being consistent with the existence of a ubiquitous and very rapid mechanism
for the growth of dust in the ISM. We use the \tau^f_B-\mu_{*} relation in
conjunction with the radiation transfer model for spiral galaxies of Popescu &
Tuffs (2011) to derive intrinsic scaling relations between specific star
formation rate (sSFR), stellar mass, and \mu_{*}, in which the attenuation of
the UV light used to measure the SFR is corrected on an object-to-object basis.
A marked reduction in scatter in these relations is achieved which is
demonstrably due to correction of both the inclination-dependent and face-on
components of attenuation. Our results are consistent with a picture of spiral
galaxies in which most of the submm emission originates from grains residing in
translucent structures, exposed to UV in the diffuse interstellar radiation
field. | Cosmological constraints on a unified dark matter-energy scalar field
model with fast transition: We test the viability of a single fluid cosmological model containing a
transition from a dark-matter-like regime to a dark-energy-like regime. The
fluid is a k-essence scalar field with a well-defined Lagrangian. We constrain
its model parameters with a combination of geometric probes and conclude that
the evidence for this model is similar to the evidence for $\Lambda$CDM. In
addition, we find a lower bound for the rapidity of the transition, implying
that fast transitions are favored with respect to slow ones even at background
level. |
Updated F(T) gravity constraints from high redshift cosmography: In the last dozen years a wide and variegated mass of observational data
revealed that the universe is now expanding at an accelerated rate. In the
absence of a well-based theory to interpret the observations, cosmography
provides information about the evolution of the Universe from measured
distances, only assuming that the geometry of the can be described by the
Friedmann-Lemaitre-Robertson -Walker metric. We perform a high-redshift
analysis allows us to put constraints on the cosmographic parameters up to the
5fth order, thus inducing indirect constraints on any gravity theory. Here we
are interested in the so called teleparallel gravity theory, f(T). Actually we
use the analytical expressions of the present day values of f(T) and its
derivatives as functions of the cosmographic parameters to map the cosmography
region of confidences into confidence ranges for f(T) and its derivative.
Moreover, we show how these can be used to test some teleparallel gravity
models without solving the dynamical equations. Our analysis is based on the
Union2 Type Ia Supernovae (SNIa) data set, a set of 28 measurements of the
Hubble parameter, the Hubble diagram constructed from some Gamma Ray Bursts
(GRB) luminosity distance indicators, and gaussian priors on the distance from
the Baryon Acoustic Oscillations (BAO), and the Hubble constant h. To perform
our statistical analysis and to explore the probability distributions of the
cosmographic parameters we use the Markov Chain Monte Carlo Method (MCMC). | The Assembly of Milky Way-like Galaxies Since z~2.5: Galaxies with the mass of the Milky Way dominate the stellar mass density of
the Universe but it is uncertain how and when they were assembled. Here we
study progenitors of these galaxies out to z=2.5, using data from the 3D-HST
and CANDELS Treasury surveys. We find that galaxies with present-day stellar
masses of log(M)~10.7 built ~90% of their stellar mass since z=2.5, with most
of the star formation occurring before z=1. In marked contrast to the assembly
history of massive elliptical galaxies, mass growth is not limited to large
radii: the mass in the central 2 kpc of the galaxies increased by a factor of
3.2+-0.8 between z=2.5 and z=1. We therefore rule out simple models in which
bulges were fully assembled at high redshift and disks gradually formed around
them. Instead, bulges (and black holes) likely formed in lockstep with disks,
through bar instabilities, migration, or other processes. We find that after
z=1 the growth in the central regions gradually stopped and the disk continued
to build, consistent with recent studies of the gas distributions in z~1
galaxies and the properties of many spiral galaxies today. |
Modeling Dust and Starlight in Galaxies Observed by Spitzer and
Herschel: NGC 628 and NGC 6946: We characterize the dust in NGC628 and NGC6946, two nearby spiral galaxies in
the KINGFISH sample. With data from 3.6um to 500um, dust models are strongly
constrained. Using the Draine & Li (2007) dust model, (amorphous silicate and
carbonaceous grains), for each pixel in each galaxy we estimate (1) dust mass
surface density, (2) dust mass fraction contributed by polycyclic aromatic
hydrocarbons (PAH)s, (3) distribution of starlight intensities heating the
dust, (4) total infrared (IR) luminosity emitted by the dust, and (5) IR
luminosity originating in regions with high starlight intensity. We obtain maps
for the dust properties, which trace the spiral structure of the galaxies. The
dust models successfully reproduce the observed global and resolved spectral
energy distributions (SEDs). The overall dust/H mass ratio is estimated to be
0.0082+/-0.0017 for NGC628, and 0.0063+/-0.0009 for NGC6946, consistent with
what is expected for galaxies of near-solar metallicity. Our derived dust
masses are larger (by up to a factor 3) than estimates based on
single-temperature modified blackbody fits. We show that the SED fits are
significantly improved if the starlight intensity distribution includes a
(single intensity) "delta function" component. We find no evidence for
significant masses of cold dust T<12K. Discrepancies between PACS and MIPS
photometry in both low and high surface brightness areas result in large
uncertainties when the modeling is done at PACS resolutions, in which case
SPIRE, MIPS70 and MIPS160 data cannot be used. We recommend against attempting
to model dust at the angular resolution of PACS. | Probing Small Scale Primordial Power Spectrum with 21cm Line Global
Signal: We argue that the global signal of neutral hydrogen 21cm line can be a
powerful probe of primordial power spectrum on small scales. Since the
amplitude of small scale primordial fluctuations is important to determine the
early structure formation and the timing when the sources of Lyman ${\alpha}$
photons are produced, they in turn affect the neutral hydrogen 21cm line
signal. We show that the information of the position of the absorption trough
can severely constrain the small scale amplitude of primordial fluctuations
once astrophysical parameters relevant to the 21cm line signal are fixed. We
also discuss how the uncertainties of astrophysical parameters affect the
constraints. |
Search for Event Rate Modulation in XENON100 Electronic Recoil Data: We have searched for periodic variations of the electronic recoil event rate
in the (2-6) keV energy range recorded between February 2011 and March 2012
with the XENON100 detector, adding up to 224.6 live days in total. Following a
detailed study to establish the stability of the detector and its background
contributions during this run, we performed an un-binned profile likelihood
analysis to identify any periodicity up to 500 days. We find a global
significance of less than 1 sigma for all periods suggesting no statistically
significant modulation in the data. While the local significance for an annual
modulation is 2.8 sigma, the analysis of a multiple-scatter control sample and
the phase of the modulation disfavor a dark matter interpretation. The
DAMA/LIBRA annual modulation interpreted as a dark matter signature with
axial-vector coupling of WIMPs to electrons is excluded at 4.8 sigma. | CMB constraints on the inflaton couplings and reheating temperature in
$α$-attractor inflation: We study reheating in $\alpha$-attractor models of inflation in which the
inflaton couples to other scalars or fermions. We show that the parameter space
contains viable regions in which the inflaton couplings to radiation can be
determined from the properties of CMB temperature fluctuations, in particular
the spectral index. This may be the only way to measure these fundamental
microphysical parameters, which shaped the universe by setting the initial
temperature of the hot big bang and contain important information about the
embedding of a given model of inflation into a more fundamental theory of
physics. The method can be applied to other models of single field inflation. |
Star Formation Properties in Barred Galaxies (SFB). II. NGC 2903 and NGC
7080: Stellar bars are important for the secular evolution of disk galaxies because
they can drive gas into the galactic central regions. To investigate the star
formation properties in barred galaxies, we presented a multi-wavelength study
of two barred galaxies NGC 2903 and NGC 7080. We performed the three-component
bulge-disk-bar decomposition using the 3.6 {\mu}m images, and identified the
bulges in the two galaxies as pseudobulges. Based on the narrowband H{\alpha}
images, the star formation clumps were identified and analyzed. the clumps in
the bulge regions have the highest star formation rate surface densities in
both galaxies, while the star formation activities in the bar of NGC 2903 are
more intense than those in the bar of NGC 7080. Finally, we compared with the
scenario of bar-driven secular evolution in previous studies, and discussed the
possible evolutionary stages of the two galaxies. | Dust-corrected surface photometry of M 31 from the Spitzer far infrared
observations: We create a model for recovering the intrinsic, absorption-corrected surface
brightness distribution of a galaxy and apply the model to the M31.
We construct a galactic model as a superposition of axially symmetric stellar
components and a dust disc to analyse the intrinsic absorption efects. Dust
column density is assumed to be proportional to the far-infrared flux of the
galaxy. Along each line of sight, the observed far-infrared spectral energy
distribution is approximated with modified black body functions considering
dust components with different temperatures, allowing to determine the
temperatures and relative column densities of the dust components.
We apply the model to the nearby galaxy M31 using the Spitzer Space Telescope
far-infrared observations for mapping dust distribution and temperature. A warm
and a cold dust component are distinguished. The temperature of the warm dust
in M31 varies between 56 and 60 K and is highest in the spiral arms; the
temperature of the cold component is mostly 15-19 K and rises up to about 25 K
at the centre of the galaxy. The intensity-weighted mean temperature of the
dust decreases from T ~32 K at the centre to T ~20 K at R ~7 kpc and outwards.
We also calculate the intrinsic UBVRIL surface brightness distributions and the
spatial luminosity distribution. The intrinsic dust extinction in the V-colour
rises from 0.25 mag at the centre to 0.4-0.5 mag at R = 6-13 kpc and decreases
smoothly thereafter. The calculated total extinction-corrected luminosity of
M31 is L_B = (3.64 pm 0.15) 10^10L_sun, corresponding to an absolute luminosity
M_B = (-20.89 pm 0.04) mag. Of the total B-luminosity, 20% (0.24 mag) is
obscured from us by the dust inside M31. The intrinsic shape of the bulge is
slightly prolate in our best-fit model. |
The Shared Causal Pasts and Futures of Cosmological Events: We derive criteria for whether two cosmological events can have a shared
causal past or a shared causal future, assuming a
Friedmann-Lemaitre-Robertson-Walker universe with best-fit \Lambda CDM
cosmological parameters from the Planck satellite. We further derive criteria
for whether either cosmic event could have been in past causal contact with our
own worldline since the time of the hot "big bang", which we take to be the end
of early-universe inflation. We find that pairs of objects such as quasars on
opposite sides of the sky with redshifts z >= 3.65 have no shared causal past
with each other or with our past worldline. More complicated constraints apply
if the objects are at different redshifts from each other or appear at some
relative angle less than 180 degrees, as seen from Earth. We present examples
of observed quasar pairs that satisfy all, some, or none of the criteria for
past causal independence. Given dark energy and the recent accelerated
expansion, our observable universe has a finite conformal lifetime, and hence a
cosmic event horizon at current redshift z = 1.87. We thus constrain whether
pairs of cosmic events can signal each other's worldlines before the end of
time. Lastly, we generalize the criteria for shared past and future causal
domains for FLRW universes with nonzero spatial curvature. | Testing X-ray Measurements of Galaxy Cluster Outskirts with Cosmological
Simulations: The study of galaxy cluster outskirts has emerged as one of the new frontiers
in extragalactic astrophysics and cosmology with the advent of new observations
in X-ray and microwave. However, the thermodynamic properties and chemical
enrichment of this diffuse and azimuthally asymmetric component of the
intracluster medium (ICM) are still not well understood. This work, for the
first time, systematically explores potential observational biases in these
regions. To assess X-ray measurements of galaxy cluster properties at large
radii ($>{R}_{500c}$), we use mock Chandra analyses of cosmological galaxy
cluster simulations. The pipeline is identical to that used for Chandra
observations, but the biases discussed in this paper are relevant for all X-ray
observations outside of ${R}_{500c}$. We find the following from our analysis:
(1) filament regions can contribute as much as $50\%$ at $R_{200c}$ to the
emission measure; (2) X-ray temperatures and metal abundances from model fitted
mock X-ray spectra in a multi-temperature ICM respectively vary to the level of
$10\%$ and $50\%$; (3) resulting density profiles vary to within $10\%$ out to
$R_{200c}$, and gas mass, total mass, and baryon fractions all vary to within a
few percent; (4) the bias from a metal abundance extrapolated a factor of five
higher than the true metal abundance results in total mass measurements biased
high by $20\%$ and total gas measurements biased low by $10\%$; and (5)
differences in projection and dynamical state of a cluster can lead to gas
density slope measurements that differ by a factor of $15\%$ and $30\%$,
respectively. The presented results can partially account for some of the
recent gas profile measurements in cluster outskirts by, e.g., Suzaku. Our
findings are pertinent to future X-ray cosmological constraints from cluster
outskirts. |
Low- and high-redshift H II starburst galaxies obey different
luminosity-velocity dispersion relations: To determine whether or not H II starburst galaxies (H IIG) are
standardizable candles, we study the correlation between the H$\beta$
luminosity ($L$) and the velocity dispersion ($\sigma$) of the ionized gas from
H IIG measurements by simultaneously constraining the $L-\sigma$ relation
parameters and the cosmological model parameters. We investigate six flat and
nonflat relativistic dark energy cosmological models, spatially flat and
nonflat, and with cosmological constant or dynamical dark energy. We find that
low-redshift and high-redshift H IIG data subsets are standardizable but obey
different $L-\sigma$ relations. Current H IIG data are too sparse and too
non-uniformly distributed in redshift to allow for a determination of whether
what we have found is just a consequence of H IIG evolution. Until this issue
is better understood, H IIG data cosmological constraints must be treated with
caution. | Have pulsar timing array methods detected a cosmological phase
transition?: We show that the recent detection of a gravitational wave (GW) background
reported by various pulsar timing array (PTA) collaborations including
NANOGrav-15yr, PPTA, EPTA, and CPTA can be explained in terms of first order
phase transitions (FOPTs) from dark sector models (DSM). Specifically, we
explore a model for first order phase transitions that involves the majoron, a
Nambu-Goldstone boson that is emerging from the spontaneous symmetry breaking
of a $U(1)_{L}$ or $U(1)_{B-L}$ symmetry. We show how the predicted GW power
spectrum, with a realistic choice of the FOPT parameters, is consistent with
1-$\sigma$ deviations from the estimated parameters of the background detected
by the PTA collaborations. |
Simulating X-ray Supercavities and Their Impact on Galaxy Clusters: Recent X-ray observations of hot gas in the galaxy cluster MS 0735.6+7421
reveal huge radio-bright, quasi-bipolar X-ray cavities having a total energy
~10^{62} ergs, the most energetic AGN outburst currently known. We investigate
the evolution of this outburst with two-dimensional axisymmetric gasdynamical
calculations in which the cavities are inflated by relativistic cosmic rays.
Many key observational features of the cavities and associated shocks are
successfully reproduced. The radial elongation of the cavities indicates that
cosmic rays were injected into the cluster gas by a (jet) source moving out
from the central AGN. AGN jets of this magnitude must be almost perfectly
identically bipolar. The relativistic momentum of a single jet would cause a
central AGN black hole of mass 10^9 M_{sun} to recoil at ~6000 km s^{-1},
exceeding kick velocities during black hole mergers, and be ejected from the
cluster-center galaxy. When the cavity inflation is complete, 4PV
underestimates the total energy received by the cluster gas. Deviations of the
cluster gas from hydrostatic equilibrium are most pronounced during the early
cavity evolution when the integrated cluster mass found from the observed gas
pressure gradient can have systematic errors near the cavities of ~10-30%. The
creation of the cavity with cosmic rays generates a long-lasting global cluster
expansion that reduces the total gas thermal energy below that received from
the cavity shock. One Gyr after this single outburst, a gas mass of ~ 6 \times
10^{11} M_{sun} is transported out beyond a cluster radius of 500 kpc. Such
post-cavity outflows can naturally produce the discrepancy observed between the
cluster gas mass fraction and the universal baryon fraction inferred from WMAP
observations. (Abridged) | Indirect Dark Matter Searches in the Light of ATIC, FERMI, EGRET and
PAMELA: Recently, new data on antiprotons and positrons from PAMELA, e- + e+ spectra
from ATIC, FERMI and HESS up to TeV energies all indicate deviations from
expectations, which has caused an interesting mix of new explanations, ranging
from background, standard astrophysical sources to signals from dark matter
(DM) annihilation. Unfortunately, the excess in positrons is not matched with
obvious excesses in antiprotons or gamma rays, so a new class of DM scenarios
with leptophilic WIMP candidates have been invoked. On the other hand, the
increase in the positron fraction, which could have had any spectral shape for
new physics, matches well the shape expected from proton background. |
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