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Quantifying dwarf satellites through gravitational imaging: the case of
SDSS J120602.09+514229.5: SDSS J120602.09+514229.5 is a gravitational lens system formed by a group of
galaxies at redshift z=0.422 lensing a bright background galaxy at redshift
z=2.001. The main peculiarity of this system is the presence of a luminous
satellite near the Einstein radius, that slightly deforms the giant arc. This
makes SDSS J120602.09+514229.5 the ideal system to test our grid-based Bayesian
lens modelling method, designed to detect galactic satellites independently
from their mass-to-light ratio, and to measure the mass of this dwarf galaxy
despite its high redshift. Thanks to the pixelized source and potential
reconstruction technique of Vegetti and Koopmans 2009a we are able to detect
the luminous satellite as a local positive surface density correction to the
overall smooth potential. Assuming a truncated Pseudo-Jaffe density profile,
the satellite has a mass M=(2.75+-0.04)10^10 M_sun inside its tidal radius of
r_t=0.68". We determine for the satellite a luminosity of L_B=(1.6+-0.8)10^9
L_sun, leading to a total mass-to-light ratio within the tidal radius of
(M/L)_B=(17.2+-8.5) M_sun/L_sun. The central galaxy has a sub-isothermal
density profile as in general is expected for group members. From the SDSS
spectrum we derive for the central galaxy a velocity dispersion of
sigma_kinem=380+-60 km/s within the SDSS aperture of diameter 3". The
logarithmic density slope of gamma=1.7+0.25-0.30 (68% CL), derived from this
measurement, is consistent within 1-sigma with the density slope of the
dominant lens galaxy gamma~1.6, determined from the lens model. This paper
shows how powerful pixelized lensing techniques are in detecting and
constraining the properties of dwarf satellites at high redshift. | Graviton mass might reduce tension between early and late time
cosmological data: The standard $\Lambda$-CDM predicts a growth of structures which tends to be
higher than the values of redshift space distortion (RSD) measurements, if the
cosmological parameters are fixed by the CMB data. In this paper we point out
that this discrepancy can be resolved/understood if we assume that the graviton
has a small but non-zero mass. In the context of the Minimal Theory of Massive
Gravity (MTMG), due to infrared Lorentz violations measurable only at present
cosmological scales, the graviton acquires a mass without being haunted by
unwanted extra degrees of freedom. While the so-called self-accelerating branch
of cosmological solutions in MTMG has the same phenomenology for the background
as well as the scalar- and vector-type linear perturbations as the
$\Lambda$-CDM in General Relativity (GR), it is possible to choose another
branch so that the background is the same as that in GR but the evolution of
matter perturbations gets modified by the graviton mass. On studying the fit of
such modified dynamics to the above-mentioned RSD measurements, we find that
the $\Lambda$-CDM model is less probable than MTMG by two orders of magnitude.
With the help of the cross correlation between the integrated Sachs-Wolfe (ISW)
effect and the large scale structure (LSS), the data also pin-down the graviton
mass squared around $\mu^2\approx - (3\times 10^{-33} \rm{eV})^2$, which is
consistent with the latest bound $|\mu^2|<(1.2\times 10^{-22} \rm{eV})^2$ set
by the recent LIGO observation. |
The cosmological constant and the coincidence problem in a new
cosmological interpretation of the universal constant c: In a recent paper (Vigoureux et al. Int. J. Theor. Phys. 47:928, 2007) it has
been suggested that the velocity of light and the expansion of the universe are
two aspects of one single concept connecting space and time in the expanding
universe. It has then be shown that solving Friedmann's equations with that
interpretation (and keeping c = constant) can explain number of unnatural
features of the standard cosmology (for example: the flatness problem, the
problem of the observed uniformity in term of temperature and density of the
cosmological background radiation, the small-scale inhomogeneity problem...)
and leads to reconsider the Hubble diagram of distance moduli and redshifts as
obtained from recent observations of type Ia supernovae without having to need
an accelerating universe. In the present work we examine the problem of the
cosmological constant. We show that our model can exactly generate $\Lambda$
(equation of state $P_\varphi = - \rho_\varphi c^2$ with $\Lambda \propto
R^{-2}$) contrarily to the standard model which cannot generate it exactly. We
also show how it can solve the so-called cosmic coincidence problem. | Massive optimal data compression and density estimation for scalable,
likelihood-free inference in cosmology: Many statistical models in cosmology can be simulated forwards but have
intractable likelihood functions. Likelihood-free inference methods allow us to
perform Bayesian inference from these models using only forward simulations,
free from any likelihood assumptions or approximations. Likelihood-free
inference generically involves simulating mock data and comparing to the
observed data; this comparison in data-space suffers from the curse of
dimensionality and requires compression of the data to a small number of
summary statistics to be tractable. In this paper we use massive
asymptotically-optimal data compression to reduce the dimensionality of the
data-space to just one number per parameter, providing a natural and optimal
framework for summary statistic choice for likelihood-free inference. Secondly,
we present the first cosmological application of Density Estimation
Likelihood-Free Inference (\textsc{delfi}), which learns a parameterized model
for joint distribution of data and parameters, yielding both the parameter
posterior and the model evidence. This approach is conceptually simple,
requires less tuning than traditional Approximate Bayesian Computation
approaches to likelihood-free inference and can give high-fidelity posteriors
from orders of magnitude fewer forward simulations. As an additional bonus, it
enables parameter inference and Bayesian model comparison simultaneously. We
demonstrate Density Estimation Likelihood-Free Inference with massive data
compression on an analysis of the joint light-curve analysis supernova data, as
a simple validation case study. We show that high-fidelity posterior inference
is possible for full-scale cosmological data analyses with as few as $\sim
10^4$ simulations, with substantial scope for further improvement,
demonstrating the scalability of likelihood-free inference to large and complex
cosmological datasets. |
Photometric Supernovae Redshift Systematics Requirements: Imaging surveys will find many tens to hundreds of thousands of Type Ia
supernovae in the next decade, and measure their light curves. In addition to a
need for characterizing their types and subtypes, a redshift is required to
place them on a Hubble diagram to map the cosmological expansion. We
investigate the requirements on redshift systematics control in order not to
bias cosmological results, in particular dark energy parameter estimation. We
find that additive and multiplicative systematics must be constrained at the
few$\,\times 10^{-3}$ level, effectively requiring spectroscopic followup for
robust use of photometric supernovae. Catastrophic outliers need control at the
subpercent level. We also investigate sculpting the spectroscopic sample. | The concentration-mass relation of clusters of galaxies from the
OmegaWINGS survey: The relation between a cosmological halo concentration and its mass (cMr) is
a powerful tool to constrain cosmological models of halo formation and
evolution. On the scale of galaxy clusters the cMr has so far been determined
mostly with X-ray and gravitational lensing data. The use of independent
techniques is helpful in assessing possible systematics. Here we provide one of
the few determinations of the cMr by the dynamical analysis of the
projected-phase-space distribution of cluster members. Based on the WINGS and
OmegaWINGS data sets, we used the Jeans analysis with the MAMPOSSt technique to
determine masses and concentrations for 49 nearby clusters, each of which has
~60 spectroscopic members or more within the virial region, after removal of
substructures. Our cMr is in statistical agreement with theoretical predictions
based on LambdaCDM cosmological simulations. Our cMr is different from most
previous observational determinations because of its flatter slope and lower
normalization. It is however in agreement with two recent cMr obtained using
the lensing technique on the CLASH and LoCuSS cluster data sets. In the future
we will extend our analysis to galaxy systems of lower mass and at higher
redshifts. |
The clustering of galaxies in the SDSS-III Baryon Oscillation
Spectroscopic Survey: RSD measurement from the LOS-dependent power spectrum
of DR12 BOSS galaxies: We measure and analyse the clustering of the Baryon Oscillation Spectroscopic
Survey (BOSS) relative to the line-of-sight (LOS), for LOWZ and CMASS galaxy
samples drawn from the final Data Release 12 (DR12). The LOWZ sample contains
361\,762 galaxies with an effective redshift of $z_{\rm lowz}=0.32$, and the
CMASS sample 777\,202 galaxies with an effective redshift of $z_{\rm
cmass}=0.57$. From the power spectrum monopole and quadrupole moments around
the LOS, we measure the growth of structure parameter $f$ times the amplitude
of dark matter density fluctuations $\sigma_8$ by modeling the Redshift-Space
Distortion signal. When the geometrical Alcock-Paczynski effect is also
constrained from the same data, we find joint constraints on $f\sigma_8$, the
product of the Hubble constant and the comoving sound horizon at the baryon
drag epoch $H(z)r_s(z_d)$, and the angular distance parameter divided by the
sound horizon $D_A(z)/r_s(z_d)$. We find $f(z_{\rm lowz})\sigma_8(z_{\rm
lowz})=0.394\pm0.062$, $D_A(z_{\rm lowz})/r_s(z_d)=6.35\pm0.19$, $H(z_{\rm
lowz})r_s(z_d)=(11.41\pm 0.56)\,{10^3\rm km}s^{-1}$ for the LOWZ sample, and
$f(z_{\rm cmass})\sigma_8(z_{\rm cmass})=0.444\pm0.038$, $D_A(z_{\rm
cmass})/r_s(z_d)=9.42\pm0.15$, $H(z_{\rm cmass})r_s(z_d)=(13.92 \pm 0.44)\,
{10^3\rm km}s^{-1}$ for the CMASS sample. We find general agreement with
previous BOSS DR11 measurements. Assuming the Hubble parameter and angular
distance parameter are fixed at fiducial $\Lambda$CDM values, we find $f(z_{\rm
lowz})\sigma_8(z_{\rm lowz})=0.485\pm0.044$ and $f(z_{\rm
cmass})\sigma_8(z_{\rm cmass})=0.436\pm0.022$ for the LOWZ and CMASS samples,
respectively. | Remarks about the Tensor Mode Detection by the BICEP2 Collaboration and
the Super-Planckian Excursions of the Inflaton Field: The recent detection by the BICEP2 collaboration of a high level of tensor
modes has relevant implications which we briefly discuss in this short note. In
particular, the large angle CMB B- mode polarisation seems to imply problematic
super-Planckian excursions of the inflaton field. We provide some comments
about this point and in particular we stress a natural resolution to it: given
our current (and probably future) observational ignorance about the true source
of the scalar perturbations, one should abandon the theoretical prejudice that
they are associated to the inflaton fluctuations. |
Weighing neutrinos with cosmic neutral hydrogen: We investigate the signatures left by massive neutrinos on the spatial
distribution of neutral hydrogen (HI) in the post-reionization era by running
hydrodynamic simulations that include massive neutrinos as additional
collisionless particles. We find that halos in massive/massless neutrino
cosmologies host a similar amount of neutral hydrogen, although for a fixed
halo mass, on average, the HI mass increases with the sum of the neutrino
masses. Our results show that HI is more strongly clustered in cosmologies with
massive neutrinos, while its abundance, $\Omega_{\rm HI}(z)$, is lower. These
effects arise mainly from the impact of massive neutrinos on cosmology: they
suppress both the amplitude of the matter power spectrum on small scales and
the abundance of dark matter halos. Modelling the HI distribution with
hydrodynamic simulations at $z > 3$, and a simple analytic model at $z<3$, we
use the Fisher matrix formalism to conservatively forecast the constraints that
Phase 1 of the Square Kilometre Array (SKA) will place on the sum of neutrino
masses, $M_\nu\equiv \Sigma m_{\nu}$. We find that with 10,000 hours of
interferometric observations at $3 \lesssim z \lesssim 6$ from a deep and
narrow survey with SKA1-LOW, the sum of the neutrino masses can be measured
with an error $\sigma(M_\nu)\lesssim0.3$ eV (95% CL). Similar constraints can
be obtained with a wide and deep SKA1-MID survey at $z \lesssim 3$, using the
single-dish mode. By combining data from MID, LOW, and Planck, plus priors on
cosmological parameters from a Stage IV spectroscopic galaxy survey, the sum of
the neutrino masses can be determined with an error $\sigma(M_\nu)\simeq0.06$
eV (95% CL). | Primordial star formation: relative impact of H2 three-body rates and
initial conditions: Population III stars are the first stars in the Universe to form at z=20-30
out of a pure hydrogen and helium gas in minihalos of 10^5-10^6 M$_\odot$ .
Cooling and fragmentation is thus regulated via molecular hydrogen. At
densities above 10^8 cm$^{-3}$, the three-body H2 formation rates are
particularly important for making the gas fully molecular. These rates were
considered to be uncertain by at least a few orders of magnitude. We explore
the impact of new accurate three-body H2 formation rates derived by Forrey
(2013) for three different minihalos, and compare to the results obtained with
three-body rates employed in previous studies. The calculations are performed
with the cosmological hydrodynamics code ENZO (release 2.2) coupled with the
chemistry package KROME (including a network for primordial chemistry), which
was previously shown to be accurate in high resolution simulations. While the
new rates can shift the point where the gas becomes fully molecular, leading to
a different thermal evolution, there is no trivial trend in how this occurs.
While one might naively expect the results to be inbetween the calculations
based on Palla et al. (1983) and Abel et al. (2002), the behavior can be close
to the former or the latter depending on the dark matter halo that is explored.
We conclude that employing the correct three-body rates is about as equally
important as the use of appropriate initial conditions, and that the resulting
thermal evolution needs to be calculated for every halo individually. |
The 2nd Generation z(Redshift) and Early Universe Spectrometer Part I:
First-light observation of a highly lensed local-ULIRG analog at high-z: We report first science results from our new spectrometer, the 2nd generation
z(Redshift) and Early Universe Spectrometer (ZEUS-2), recently commissioned on
the Atacama Pathfinder Experiment telescope (APEX). ZEUS-2 is a submillimeter
grating spectrometer optimized for detecting the faint and broad lines from
distant galaxies that are redshifted into the telluric windows from 200 to 850
microns. It utilizes a focal plane array of transition-edge sensed bolometers,
the first use of these arrays for astrophysical spectroscopy. ZEUS-2 promises
to be an important tool for studying galaxies in the years to come due to its
synergy with ALMA and its capabilities in the short submillimeter windows that
are unique in the post Herschel era. Here we report on our first detection of
the [CII] 158 $\mu m$ line with ZEUS-2. We detect the line at z ~ 1.8 from
H-ATLAS J091043.1-000322 with a line flux of $(6.44 \pm 0.42) \times 10^{-18} W
m^{-2}$. Combined with its far-infrared luminosity and a new Herschel-PACS
detection of the [OI] 63 $\mu m $ line we model the line emission as coming
from a photo-dissociation region with far-ultraviolet radiation field, $G
\approx 2 \times 10^{4} G_{0}$, gas density, $n \approx 1 \times 10^{3}
cm^{-3}$ and size between ~ 0.4 and 1 kpc. Based on this model, we conclude
that H-ATLAS J091043.1-000322 is a high redshift analogue of a local
ultra-luminous infrared galaxy, i.e. it is likely the site of a compact
starburst due to a major merger. Further identification of these merging
systems is important for constraining galaxy formation and evolution models. | Using Multipoles of the Correlation Function to Measure H(z), D_A(z),
and β(z) from Sloan Digital Sky Survey Luminous Red Galaxies: Galaxy clustering data can be used to measure the cosmic expansion history
H(z), the angular-diameter distance D_A(z), and the linear redshift-space
distortion parameter beta(z). Here we present a method for using effective
multipoles of the galaxy two-point correlation function (\xi_0(s), \xi_2(s),
\xi}_4(s), and \xi_6(s), with s denoting the comoving separation) to measure
H(z), D_A(z)$, and beta(z), and validate it using LasDamas mock galaxy
catalogs. Our definition of effective multipoles explicitly incorporates the
discreteness of measurements, and treats the measured correlation function and
its theoretical model on the same footing. We find that for the mock data,
\xi_0+\xi_2+\xi_4 captures nearly all the information, and gives significantly
stronger constraints on H(z), D_A(z), and beta(z), compared to using only
\xi_0+\xi_2.
We apply our method to the sample of luminous red galaxies (LRGs) from the
Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) without assuming a dark
energy model or a flat Universe. We find that \xi}_4(s) deviates on scales of
s<60Mpc/h from the measurement from mock data (in contrast to \xi_0(s),
\xi_2(s), and \xi_6(s)), thus we only use \xi_0+\xi_2 for our fiducial
constraints. We obtain {H(0.35), D_A(0.35), Omega_mh^2, beta(z)} =
{79.6_{-8.7}^{+8.3} km/s/Mpc, 1057_{-87}^{+88}Mpc, 0.103\pm0.015, 0.44\pm0.15}
using \xi_0+\xi_2. We find that H(0.35)r_s(z_d)/c and D_A(0.35)/r_s(z_d) (where
r_s(z_d) is the sound horizon at the drag epoch) are more tightly constrained:
{H(0.35)r_s(z_d)/c, D_A(0.35)/r_s(z_d)} = {0.0437_{-0.0043}^{+0.0041},
6.48_{-0.43}^{+0.44}\} using \xi_0+\xi_2. |
Ten More New Sightlines for the Study of Intergalactic Helium, and
Hundreds of Far-UV-Bright Quasars, from SDSS, GALEX, and HST: Absorption along quasar sightlines remains among the most sensitive direct
measures of HeII reionization in much of the intergalactic medium (IGM). Until
recently, fewer than a half-dozen unobscured quasar sightlines suitable for the
HeII Gunn-Peterson test were known; although these handful demonstrated great
promise, the small sample size limited confidence in cosmological inferences.
We have recently added nine more such clean HeII quasars, exploiting SDSS
quasar samples, broadband UV imaging from GALEX, and high-yield UV
spectroscopic confirmations from HST. Here we markedly expand this approach by
cross-correlating SDSS DR7 and GALEX GR4+5 to catalog 428 SDSS and 165 other
quasars with z>2.78 having likely (~70%) GALEX detections, suggesting they are
bright into the far-UV. Reconnaissance HST Cycle 16 Supplemental prism data for
29 of these new quasar-GALEX matches spectroscopically confirm 17 as indeed
far-UV bright. At least 10 of these confirmations have clean sightlines all the
way down to HeII Lyman-alpha, substantially expanding the number of known clean
HeII quasars, and reaffirming the order of magnitude enhanced efficiency of our
selection technique. Combined confirmations from this and our past programs
yield more than twenty HeII quasars, quintupling the sample. These provide
substantial progress toward a sample of HeII quasar sightlines large enough,
and spanning a sufficient redshift range, to enable statistical IGM studies
that may avoid individual object peculiarity and sightline variance. Our
expanded catalog of hundreds of high-likelihood far-UV-bright QSOs additionally
will be useful for understanding the extreme-UV properties of the quasars
themselves. | Using Atom Interferometry to Detect Dark Energy: We review the tantalising prospect that the first evidence for the dark
energy driving the observed acceleration of the Universe on giga-parsec scales
may be found through metre scale laboratory based atom interferometry
experiments. To do that, we first introduce the idea that scalar fields could
be responsible for dark energy and show that in order to be compatible with
fifth force constraints these fields must have a screening mechanism which
hides their effects from us within the solar system. Particular emphasis is
placed on one such screening mechanism known as the chameleon effect where the
field's mass becomes dependent on the environment. The way the field behaves in
the presence of a spherical source is determined and we then go on to show how
in the presence of the kind of high vacuum associated with atom interferometry
experiments, and when the test particle is an atom, it is possible to use the
associated interference pattern to place constraints on the acceleration due to
the fifth force of the chameleon field - this has already been used to rule out
large regions of the chameleon parameter space and maybe one day will be able
to detect the force due to the dark energy field in the laboratory. |
Signatures of a High Temperature QCD Transition in the Early Universe: Beyond Standard Model extensions of QCD could result in quark and gluon
confinement occurring well above a temperature of $\sim$GeV. These models can
also alter the order of the QCD phase transition. The enhanced production of
primordial black holes (PBHs) that can accompany the change in relativistic
degrees of freedom at the QCD transition therefore could favor the production
of PBHs with mass scales smaller than the Standard Model QCD horizon scale.
Consequently, and unlike PBHs associated with a standard GeV-scale QCD
transition, such PBHs can account for all the dark matter abundance in the
unconstrained asteroid-mass window. This links beyond Standard Model
modifications of QCD physics over a broad range of unexplored temperature
regimes ($\sim 10-10^3$ TeV) with microlensing surveys searching for PBHs.
Additionally, we discuss implications of these models for gravitational wave
experiments. We show that a first order QCD phase transition at $\sim7$ TeV is
consistent with the Subaru Hyper-Suprime Cam candidate event, while a $\sim 70$
GeV transition is consistent with OGLE candidate events, and also could account
for the claimed NANOGrav gravitational wave signal. | Measuring $μ$-Distortions from the Thermal Sunyaev-Zeldovich effect: The thermal Sunyaev-Zel'dovich (tSZ) effect is a spectral distortion of the
cosmic microwave background (CMB) resulting from inverse Compton scattering of
CMB photons with electrons in the medium of galaxy clusters. The spectrum of
the tSZ effect is typically calculated assuming the spectrum of the CMB is a
blackbody. However, energy or photon number injection at any epoch after photon
creation processes become inefficient will distort the blackbody, potentially
leading to a chemical potential or $\mu$-distortion for early injection. These
$primordial$ spectral distortions will therefore introduce a change in the tSZ
effect, effectively a distortion of a distortion. While this effect is small
for an individual cluster's spectrum, upcoming and proposed CMB surveys expect
to detect tens of thousands of clusters with the tSZ effect. In this paper, we
forecast constraints on the $\mu$-distortion monopole from the distortion of
the tSZ spectrum of clusters measured by CMB surveys. We find that planned
experiments have the raw sensitivity to place constraints on $\mu$ that are
comparable to or better than existing constraints but control over foregrounds
and other systematics will be critical. |
Constraining f(R) gravity in solar system, cosmology and binary pulsar
systems: The $f(R)$ gravity can be cast into the form of a scalar-tensor theory, and
scalar degree of freedom can be suppressed in high-density regions by the
chameleon mechanism. In this article, for the general $f(R)$ gravity, using a
scalar-tensor representation with the chameleon mechanism, we calculate the
parameterized post-Newtonian parameters $\gamma$ and $\beta$, the effective
gravitational constant $G_{\rm eff}$, and the effective cosmological constant
$\Lambda_{\rm eff}$. In addition, for the general $f(R)$ gravity, we also
calculate the rate of orbital period decay of the binary system due to
gravitational radiation. Then we apply these results to specific $f(R)$ models
(Hu-Sawicki model, Tsujikawa model and Starobinsky model) and derive the
constraints on the model parameters by combining the observations in solar
system, cosmological scales and the binary systems. | Spectroscopic confirmation of a galaxy at redshift z=8.6: Galaxies had their most significant impact on the Universe when they
assembled their first generations of stars. Energetic photons emitted by young,
massive stars in primeval galaxies ionized the intergalactic medium surrounding
their host galaxies, cleared sight-lines along which the light of the young
galaxies could escape, and fundamentally altered the physical state of the
intergalactic gas in the Universe continuously until the present day.
Observations of the Cosmic Microwave Background, and of galaxies and quasars at
the highest redshifts, suggest that the Universe was reionised through a
complex process that was completed about a billion years after the Big Bang, by
redshift z~6. Detecting ionizing Ly-alpha photons from increasingly distant
galaxies places important constraints on the timing, location and nature of the
sources responsible for reionisation. Here we report the detection of Ly-a
photons emitted less than 600 million years after the Big Bang. UDFy-38135539
is at a redshift z=8.5549+-0.0002, which is greater than those of the
previously known most distant objects, at z=8.2 and z=6.97. We find that this
single source is unlikely to provide enough photons to ionize the volume
necessary for the emission line to escape, requiring a significant contribution
from other, probably fainter galaxies nearby. |
A Simplified Approach to General Scalar-Tensor Theories: The most general covariant action describing gravity coupled to a scalar
field with only second order equations of motion, Horndeski's theory (also
known as "Generalized Galileons"), provides an all-encompassing model in which
single scalar dark energy models may be constrained. However, the generality of
the model makes it cumbersome to manipulate. In this paper, we demonstrate that
when considering linear perturbations about a Friedmann-Robertson-Walker
background, the theory is completely specified by only six functions of time,
two of which are constrained by the background evolution. We utilise the ideas
of the Effective Field Theory of Inflation/Dark Energy to explicitly construct
these six functions of time in terms of the free functions appearing in
Horndeski's theory. These results are used to investigate the behavior of the
theory in the quasistatic approximation. We find that only four functions of
time are required to completely specify the linear behavior of the theory in
this limit, which can further be reduced if the background evolution is fixed.
This presents a significantly reduced parameter space from the original
presentation of Horndeski's theory, giving hope to the possibility of
constraining the parameter space. This work provides a cross-check for previous
work on linear perturbations in this theory, and also generalizes it to include
spatial curvature. | The Morphology of Passively Evolving Galaxies at z ~ 2 from HST/WFC3
Deep Imaging in the Hubble Ultradeep Field: We present near-IR images, obtained with the Hubble Space Telescope (HST) and
the WFC3/IR camera, of six passive and massive galaxies at redshift 1.3<z<2.4
(SSFR<10^{-2} Gyr^{-1}; stellar mass M~10^{11} M_{sun}), selected from the
Great Observatories Origins Deep Survey (GOODS). These images, which have a
spatial resolution of ~1.5 kpc, provide the deepest view of the optical
rest-frame morphology of such systems to date. We find that the light profile
of these galaxies is regular and well described by a Sersic model with index
typical of today's spheroids. Their size, however, is generally much smaller
than today's early types of similar stellar mass, with four out of six galaxies
having r_e ~ 1 kpc or less, in quantitative agreement with previous similar
measures made at rest-frame UV wavelengths. The images reach limiting surface
brightness mu~26.5 mag arcsec^{-2} in the F160W bandpass; yet, there is no
evidence of a faint halo in the galaxies of our sample, even in their stacked
image. We also find that these galaxies have very weak "morphological
k-correction" between the rest-frame UV (from the ACS z-band), and the
rest--frame optical (WFC3 H-band): the Sersic index, physical size and overall
morphology are independent or only mildly dependent on the wavelength, within
the errors. |
Testing MOND on small bodies in the remote solar system: Modified Newtonian dynamics (MOND), which postulates a breakdown of Newton's
laws of gravity/dynamics below some critical acceleration threshold, can
explain many otherwise puzzling observational phenomena on galactic scales.
MOND competes with the hypothesis of dark matter, which successfully explains
the cosmic microwave background and large-scale structure. Here we provide the
first solar-system test of MOND that probes the sub-critical acceleration
regime. Using the Bekenstein-Milgrom AQUAL formulation, we simulate the
evolution of myriads of test particles (planetesimals or comets) born in the
trans-Neptunian region and scattered by the giant planets over the lifetime of
the Sun to heliocentric distances of $10^2$-$10^5$ au. We include the effects
of the Galactic tidal field and passing stars. While Newtonian simulations
reproduce the distribution of binding energies of long-period and Oort-cloud
comets detectable from Earth, MOND-based simulations do not. This conclusion is
robust to plausible changes in the migration history of the planets, the
migration history of the Sun, the MOND transition function, effects of the
Sun's birth cluster, and the fading properties of long-period comets. For the
most popular version of AQUAL, characterized by a gradual transition between
the Newtonian and MOND regimes, our MOND-based simulations also fail to
reproduce the orbital distribution of trans-Neptunian objects in the detached
disk (perihelion > 38 au). Our results do not rule out some MOND theories more
elaborate than AQUAL, in which non-Newtonian effects are screened on small
spatial scales, at small masses, or in external gravitational fields comparable
in strength to the critical acceleration. | Probing the high-z IGM with the hyperfine transition of $^3$He$^+$: The hyperfine transition of $^3$He$^+$ at 3.5cm has been thought as a probe
of the high-z IGM since it offers a unique insight into the evolution of the
helium component of the gas, as well as potentially give an independent
constraint on the 21cm signal from neutral hydrogen. In this paper, we use
radiative transfer simulations of reionization driven by sources such as stars,
X-ray binaries, accreting black holes and shock heated interstellar medium, and
simulations of a high-z quasar to characterize the signal and analyze its
prospects of detection. We find that the peak of the signal lies in the range
1-50 $\mu$K for both environments, but while around the quasar it is always in
emission, in the case of cosmic reionization a brief period of absorption is
expected. As the evolution of HeII is determined by stars, we find that it is
not possible to distinguish reionization histories driven by more energetic
sources. On the other hand, while a bright QSO produces a signal in 21cm that
is very similar to the one from a large collection of galaxies, its signature
in 3.5cm is very peculiar and could be a powerful probe to identify the
presence of the QSO. We analyze the prospects of the signal's detectability
using SKA1-mid as our reference telescope. We find that the noise power
spectrum dominates over the power spectrum of the signal, although a modest S/N
ratio can be obtained when the wavenumber bin width and the survey volume are
sufficiently large. |
Hydrostatic mass estimates of massive galaxy clusters: a study with
varying hydrodynamics flavours and non-thermal pressure support: We use a set of 45 simulated clusters with a wide mass range ($8\times
10^{13} < M_{500}~[$M$_{\odot}]~< 2\times 10^{15}$) to investigate the effect
of varying hydrodynamics flavours on cluster mass estimates. The cluster zooms
were simulated using the same cosmological models as the BAHAMAS and C-EAGLE
projects, leading to differences in both the hydrodynamic solvers and the
subgrid physics but still producing clusters which broadly match observations.
At the same mass resolution as BAHAMAS, for the most massive clusters ($M_{500}
> 10^{15}$ M$_{\odot}$), we find changes in the SPH method produce the greatest
differences in the final halo, while the subgrid models dominate at lower mass.
By calculating the mass of all of the clusters using different permutations of
the pressure, temperature and density profiles, created with either the true
simulated data or mock spectroscopic data, we find that the spectroscopic
temperature causes a bias in the hydrostatic mass estimates which increases
with the mass of the cluster, regardless of the SPH flavour used. For the most
massive clusters, the estimated mass of the cluster using spectroscopic density
and temperature profiles is found to be as low as 50 per cent of the true mass
compared to $\sim$ 90 per cent for low mass clusters. When including a
correction for non-thermal pressure, the spectroscopic hydrostatic mass
estimates are less biased on average and the mass dependence of the bias is
reduced, although the scatter in the measurements does increase. | The broad Fe Kα line and supermassive black holes: Here we present an overview of some of the most significant observational and
theoretical studies of the broad Fe K{\alpha} spectral line, which is believed
to originate from the innermost regions of relativistic accretion disks around
central supermassive black holes of galaxies. The most important results of our
investigations in this field are also listed. All these investigations indicate
that the broad Fe K{\alpha} line is a powerful tool for studying the properties
of the supermassive black holes (such as their masses and spins), space-time
geometry (metric) in their vicinity, their accretion physics, probing the
effects of their strong gravitational fields, and for testing the certain
predictions of General Relativity. |
How well can we really estimate the stellar masses of galaxies from
broadband photometry?: The estimated stellar masses of galaxies are widely used to characterize how
the galaxy population evolves over cosmic time. If stellar masses can be
estimated in a robust manner, free from any bias, global diagnostics such as
the stellar mass function can be used to constrain the physics of galaxy
formation. We explore how galaxy stellar masses, estimated by fitting
broad-band spectral energy distributions (SEDs) with stellar population models,
can be biased as a result of commonly adopted assumptions for the
star-formation and chemical enrichment histories, recycled fractions and dust
attenuation curves of galaxies. We apply the observational technique of
broad-band SED fitting to model galaxy SEDs calculated by the theoretical
galaxy formation model GALFORM, isolating the effect of each of these
assumptions. We find that, averaged over the entire galaxy population, the
common assumption of exponentially declining star-formation histories does not
adversely affect stellar mass estimation. We show that fixing the metallicity
in SED fitting or using sparsely sampled metallicity grids can introduce mass
dependent systematics into stellar mass estimates. We find that the common
assumption of a star-dust geometry corresponding to a uniform foreground dust
screen can cause the stellar masses of dusty model galaxies to be significantly
underestimated. Finally, we show that stellar mass functions recovered by
applying SED fitting to model galaxies at high redshift can differ
significantly in both shape and normalization from the intrinsic mass functions
predicted by a given model. Given these differences, our methodology of using
stellar masses estimated from model galaxy SEDs offers a new, self-consistent
way to compare model predictions with observations. | Axion production and CMB spectral distortion in cosmological tangled
magnetic field: Axion production due to photon-axion mixing in tangled magnetic field(s)
prior to recombination epoch and magnetic field damping can generate cosmic
microwave background (CMB) spectral distortions. In particular, contribution of
both processes to CMB $\mu$ distortion in the case of resonant photon-axion
mixing is studied. Assuming that magnetic field power spectrum is approximated
by a power law $P_B(k)\propto k^n$ with spectral index $n$, it is shown that
for magnetic field cut-off scales $172.5$ pc $\leq \lambda_B\leq 4\times 10^3$
pc, axion contribution to CMB $\mu$ distortion is subdominant in comparison
with magnetic field damping in the cosmological plasma. Using COBE upper limit
on $\mu$ and for magnetic field scale $\lambda_B\simeq 415$ pc, weaker limit in
comparison with other studies on the magnetic field strength ($B_0\leq
8.5\times 10^{-8}$ G) up to a factor 10 for the DFSZ axion model and axion mass
$m_a\geq 2.6\times 10^{-6}$ eV is found. A forecast for the expected
sensitivity of PIXIE/PRISM on $\mu$ is also presented. |
Precise Tully-Fisher Relations without Galaxy Inclinations: Power-law relations between tracers of baryonic mass and rotational
velocities of disk galaxies, so-called Tully-Fisher relations (TFRs), offer a
wealth of applications in galaxy evolution and cosmology. However, measurements
of rotational velocities require galaxy inclinations, which are difficult to
measure, thus limiting the range of TFR studies. This work introduces a maximum
likelihood estimation (MLE) method for recovering the TFR in galaxy samples
with limited or no information on inclinations. The robustness and accuracy of
this method is demonstrated using virtual and real galaxy samples.
Intriguingly, the MLE reliably recovers the TFR of all test samples, even
without using any inclination measurements - that is, assuming a
sin(i)-distribution for galaxy inclinations. Explicitly, this 'inclination-free
MLE' recovers the three TFR parameters (zero-point, slope, scatter) with
statistical errors only about 1.5-times larger than the best estimates based on
perfectly known galaxy inclinations with zero uncertainty. Thus, given
realistic uncertainties, the inclination-free MLE is highly competitive. If
inclination measurements have mean errors larger than 10 degrees, it is better
not to use any inclinations, than to consider the inclination measurements to
be exact. The inclination-free MLE opens interesting perspectives for future HI
surveys by the SKA and its pathfinders. | Toward a more stringent test of gravity with redshift space power
spectrum: simultaneous probe of growth and amplitude of large-scale structure: Redshift-space distortions (RSD) offers an exciting opportunity to test the
gravity on cosmological scales. In the presence of galaxy bias, however, the
RSD measurement at large scales, where the linear theory prediction is safely
applied, is known to exhibit a degeneracy between the parameters of structure
growth f and fluctuation amplitude sigma8, and one can only constrain the
parameters in the form of fsigma8. In order to disentangle this degeneracy, in
this paper, we go beyond the linear theory, and consider the model of RSD
applicable to a weakly nonlinear regime. Based on the Fisher matrix analysis,
we show explicitly that the degeneracy of the parameter fsigma8 can be broken,
and sigma8 is separately estimated in the presence of galaxy bias. Performing
further the Markov chain Monte Carlo analysis, we verify that our model
correctly reproduces the fiducial values of fsigma8 and sigma8, with the
statistical errors consistent with those estimated from the Fisher matrix
analysis. We show that upcoming galaxy survey of the stage-IV class can
unambiguously determine sigma8 at the precision down to 10% at higher redshifts
even if we restrict the accessible scales to k<0.16h/Mpc |
Constraints on the abundance of primordial black holes with different
mass distributions from lensing of fast radio bursts: Primordial black holes (PBHs) has been considered to form a part of dark
matter for a long time but the possibility has been poorly constrained over a
wide mass range, including the stellar mass range ($1-100~M_{\odot}$). However,
due to the discovery of merger events of black hole binaries by LIGO-Virgo
gravitational wave observatories, the interest for PBHs in the stellar mass
window has been aroused again. Fast radio bursts (FRBs) are bright radio
transients with millisecond duration and very high all-sky occurrence rate.
Lensing effect of these bursts has been proposed as one of the optimal probes
for constraining the abundance of PBHs in the stellar mass range. In this
paper, we first investigate constraints on the abundance of PBHs from the
latest $593$ FRB observations for both the monochromatic mass distribution and
three other popular extended mass distributions related to different formation
mechanisms of PBHs. It is found that constraints from currently public FRB
observations are relatively weaker than those from existing gravitational wave
detections. Furthermore, we forecast constraining power of future FRB
observations on the abundance of PBHs with different mass distributions of PBHs
and different redshift distributions of FRBs taken into account. Finally, We
find that constraints of parameter space on extended mass distributions from
$\sim10^5$ FRBs with $\overline{\Delta t}\leq1 ~\rm ms$ would be comparable
with what can be constrained from gravitational wave events. It is foreseen
that upcoming complementary multi-messenger observations will yield
considerable constraints on the possibilities of PBHs in this intriguing mass
window. | Extragalactic gamma-ray signal from Dark Matter annihilation: a power
spectrum based computation: We revisit the computation of the extragalactic gamma-ray signal from
cosmological dark matter annihilations. The prediction of this signal is
notoriously model dependent, due to different descriptions of the clumpiness of
the dark matter distribution at small scales, responsible for an enhancement
with respect to the smoothly distributed case. We show how a direct computation
of this "flux multiplier" in terms of the nonlinear power spectrum offers a
conceptually simpler approach and may ease some problems, such as the
extrapolation issue. In fact very simple analytical recipes to construct the
power spectrum yield results similar to the popular Halo Model expectations,
with a straightforward alternative estimate of errors. For this specific
application, one also obviates to the need of identifying (often
literature-dependent) concepts entering the Halo Model, to compare different
simulations. |
Grackle: a Chemistry and Cooling Library for Astrophysics: We present the Grackle chemistry and cooling library for astrophysical
simulations and models. Grackle provides a treatment of non-equilibrium
primordial chemistry and cooling for H, D, and He species, including H2
formation on dust grains; tabulated primordial and metal cooling; multiple UV
background models; and support for radiation transfer and arbitrary heat
sources. The library has an easily implementable interface for simulation codes
written in C, C++, and Fortran as well as a Python interface with added
convenience functions for semi-analytical models. As an open-source project,
Grackle provides a community resource for accessing and disseminating
astrochemical data and numerical methods. We present the full details of the
core functionality, the simulation and Python interfaces, testing
infrastructure, performance, and range of applicability. Grackle is a fully
open-source project and new contributions are welcome. | Testing the Origin of Cosmological Magnetic Fields through the
Large-Scale Structure Consistency Relations: We study the symmetries of the post-recombination cosmological
magnetohydrodynamical equations which describe the evolution of dark matter,
baryons and magnetic fields in a self-consistent way. This is done both at the
level of fluid equations and of Vlasov-Poisson-Maxwell equations in phase
space. We discuss some consistency relations for the soft limit of the (n +
1)-correlator functions involving magnetic fields and matter overdensities. In
particular, we stress that any violation of such consistency relations at
equal-time would point towards an inflationary origin of the magnetic field. |
Dispersion in the growth of matter perturbations: We consider the linear growth of matter perturbations on low redshifts in
modified gravity Dark Energy (DE) models where G_eff(z,k) is explicitly
scale-dependent. Dispersion in the growth today will only appear for scales of
the order the critical scale ~ \lambda_{c,0}, the range of the fifth-force
today. We generalize the constraint equation satisfied by the parameters
\gamma_0(k) and \gamma'_0(k) \equiv \frac{d\gamma(z,k)}{dz}(z=0) to models with
G_{eff,0}(k) \ne G. Measurement of \gamma_0(k) and \gamma'_0(k) on several
scales can provide information about \lambda_{c,0}. In the absence of
dispersion when \lambda_{c,0} is large compared to the probed scales,
measurement of \gamma_0 and \gamma'_0 provides a consistency check independent
of \lambda_{c,0}. This applies in particular to results obtained earlier for a
viable f(R) model. | Existence and Instability of Novel Hairy Black Holes in Shift-symmetric
Horndeski Theories: Shift-symmetric Horndeski theories admit an interesting class of
Schwarzschild black hole solutions exhibiting time-dependent scalar hair. By
making use of Lema\^{i}tre coordinates, we analyze perturbations around these
types of black holes, and demonstrate that scalar perturbations around black
hole backgrounds inevitably have gradient instabilities. Taken together with
previously established results, this newly-discovered instability rules out
black holes with time-dependent scalar hair in Horndeski theories. |
A cluster finding algorithm based on the multiband identification of red
sequence galaxies: We present a new algorithm, CAMIRA, to identify clusters of galaxies in
wide-field imaging survey data. We base our algorithm on the stellar population
synthesis model to predict colours of red-sequence galaxies at a given redshift
for an arbitrary set of bandpass filters, with additional calibration using a
sample of spectroscopic galaxies to improve the accuracy of the model
prediction. We run the algorithm on ~11960 deg^2 of imaging data from the Sloan
Digital Sky Survey (SDSS) Data Release 8 to construct a catalogue of 71743
clusters in the redshift range 0.1<z<0.6 with richness after correcting for the
incompleteness of the richness estimate greater than 20. We cross-match the
cluster catalogue with external cluster catalogues to find that our photometric
cluster redshift estimates are accurate with low bias and scatter, and that the
corrected richness correlates well with X-ray luminosities and temperatures. We
use the publicly available Canada-France-Hawaii Telescope Lensing Survey
(CFHTLenS) shear catalogue to calibrate the mass-richness relation from stacked
weak lensing analysis. Stacked weak lensing signals are detected significantly
for 8 subsamples of the SDSS clusters divided by redshift and richness bins,
which are then compared with model predictions including miscentring effects to
constrain mean halo masses of individual bins. We find the richness correlates
well with the halo mass, such that the corrected richness limit of 20
corresponds to the cluster virial mass limit of about 1 \times 10^14 M_Sun/h
for the SDSS DR8 cluster sample. | The IRX-beta relation on sub-galactic scales in star-forming galaxies of
the Herschel Reference Survey: UV and optical surveys are essential to gain insight into the processes
driving galaxy formation and evolution. The rest-frame UV emission is key to
measure the cosmic SFR. However, UV light is strongly reddened by dust. In
starburst galaxies, the UV colour and the attenuation are linked, allowing to
correct for dust extinction. Unfortunately, evidence has been accumulating that
the relation between UV colour and attenuation is different for normal
star-forming galaxies when compared to starburst galaxies. It is still not
understood why star-forming galaxies deviate from the UV colour-attenuation
relation of starburst galaxies. Previous work and models hint that the role of
the shape of the attenuation curve and the age of stellar populations have an
important role. In this paper we aim at understanding the fundamental reasons
to explain this deviation. We have used the CIGALE SED fitting code to model
the far UV to the far IR emission of a set of 7 reasonably face-on spiral
galaxies from the HRS. We have explored the influence of a wide range of
physical parameters to quantify their influence and impact on the accurate
determination of the attenuation from the UV colour, and why normal galaxies do
not follow the same relation as starburst galaxies. We have found that the
deviation can be best explained by intrinsic UV colour differences between
different regions in galaxies. Variations in the shape of the attenuation curve
can also play a secondary role. Standard age estimators of the stellar
populations prove to be poor predictors of the intrinsic UV colour. These
results are also retrieved on a sample of 58 galaxies when considering their
integrated fluxes. When correcting the emission of normal star-forming galaxies
for the attenuation, it is crucial to take into account possible variations in
the intrinsic UV colour as well as variations of the shape of the attenuation
curve. |
Gravitational waves from first order phase transitions during inflation: We study the production, spectrum and detectability of gravitational waves in
models of the early Universe where first order phase transitions occur during
inflation. We consider all relevant sources. The self-consistency of the
scenario strongly affects the features of the waves. The spectrum appears to be
mainly sourced by collisions of bubble of the new phases, while plasma dynamics
(turbulence) and the primordial gauge fields connected to the physics of the
transitions are generally subdominant. The amplitude and frequency dependence
of the spectrum for modes that exit the horizon during inflation are different
from those of the waves produced by quantum vacuum oscillations of the metric
or by first order phase transitions not occurring during inflation. A moderate
number of slow (but still successful) phase transitions can leave detectable
marks in the CMBR, but the signal weakens rapidly for faster transitions. When
the number of phase transitions is instead large, the primordial gravitational
waves can be observed both in the CMBR or with LISA (marginally) and especially
DECIGO. We also discuss the nucleosynthesis bound and the constraints it places
on the parameters of the models. | The Cosmological Constant Problem, Dark Energy, and the Landscape of
String Theory: In this colloquium-level account, I describe the cosmological constant
problem: why is the energy of empty space at least 60 orders of magnitude
smaller than several known contributions to it from the Standard Model of
particle physics? I explain why the "dark energy" responsible for the
accelerated expansion of the universe is almost certainly vacuum energy. The
second half of the paper explores a more speculative subject. The vacuum
landscape of string theory leads to a multiverse in which many different
three-dimensional vacua coexist, albeit in widely separated regions. This can
explain both the smallness of the observed vacuum energy and the coincidence
that its magnitude is comparable to the present matter density. |
Testing Inflation with Large Scale Structure: Connecting Hopes with
Reality: The statistics of primordial curvature fluctuations are our window into the
period of inflation, where these fluctuations were generated. To date, the
cosmic microwave background has been the dominant source of information about
these perturbations. Large scale structure is however from where drastic
improvements should originate. In this paper, we explain the theoretical
motivations for pursuing such measurements and the challenges that lie ahead.
In particular, we discuss and identify theoretical targets regarding the
measurement of primordial non-Gaussianity. We argue that when quantified in
terms of the local (equilateral) template amplitude $f_{\rm NL}^{\rm loc}$
($f_{\rm NL}^{\rm eq}$), natural target levels of sensitivity are $\Delta
f_{\rm NL}^{\rm loc, eq.} \simeq 1$. We highlight that such levels are within
reach of future surveys by measuring 2-, 3- and 4-point statistics of the
galaxy spatial distribution. This paper summarizes a workshop held at CITA
(University of Toronto) on October 23-24, 2014. | First Observational Tests of Eternal Inflation: Analysis Methods and
WMAP 7-Year Results: In the picture of eternal inflation, our observable universe resides inside a
single bubble nucleated from an inflating false vacuum. Many of the theories
giving rise to eternal inflation predict that we have causal access to
collisions with other bubble universes, providing an opportunity to confront
these theories with observation. We present the results from the first
observational search for the effects of bubble collisions, using cosmic
microwave background data from the WMAP satellite. Our search targets a generic
set of properties associated with a bubble collision spacetime, which we
describe in detail. We use a modular algorithm that is designed to avoid a
posteriori selection effects, automatically picking out the most promising
signals, performing a search for causal boundaries, and conducting a full
Bayesian parameter estimation and model selection analysis. We outline each
component of this algorithm, describing its response to simulated CMB skies
with and without bubble collisions. Comparing the results for simulated bubble
collisions to the results from an analysis of the WMAP 7-year data, we rule out
bubble collisions over a range of parameter space. Our model selection results
based on WMAP 7-year data do not warrant augmenting LCDM with bubble
collisions. Data from the Planck satellite can be used to more definitively
test the bubble collision hypothesis. |
Planck 2015 results. VIII. High Frequency Instrument data processing:
Calibration and maps: This paper describes the processing applied to the Planck High Frequency
Instrument (HFI) cleaned, time-ordered information to produce photometrically
calibrated maps in temperature and (for the first time) in polarization. The
data from the entire 2.5 year HFI mission include almost five independent
full-sky surveys. HFI observes the sky over a broad range of frequencies, from
100 to 857 GHz. To obtain the best accuracy on the calibration over such a
large range, two different photometric calibration schemes have been used. The
545 and 857 GHz data are calibrated using models of planetary atmospheric
emission. The lower frequencies (from 100 to 353 GHz) are calibrated using the
time-variable cosmological microwave background dipole, which we call the
"orbital dipole". This source of calibration only depends on the satellite
velocity with respect to the solar system. Using a CMB temperature of 2.7255
+/- 0.0006 K, it permits an independent measurement of the amplitude of the CMB
solar dipole (3364.3 +/- 1.5 \mu K) which is approximatively 1\sigma\ higher
than the WMAP measurement with a direction that is consistent between both
experiments. We describe the pipeline used to produce the maps of intensity and
linear polarization from the HFI timelines, and the scheme used to set the zero
level of the maps a posteriori. We also summarize the noise characteristics of
the HFI maps in the 2015 Planck data release and present some null tests to
assess their quality. Finally, we discuss the major systematic effects and in
particular the leakage induced by flux mismatch between the detectors that
leads to spurious polarization signal. | Cosmic Microwave Background Trispectrum and Primordial Magnetic Field
Limits: Primordial magnetic fields will generate non-Gaussian signals in the cosmic
microwave background (CMB) as magnetic stresses and the temperature anisotropy
they induce depend quadratically on the magnetic field. We compute a new
measure of magnetic non-Gaussianity, the CMB trispectrum, on large angular
scales, sourced via the Sachs-Wolfe effect. The trispectra induced by magnetic
energy density and by magnetic scalar anisotropic stress are found to have
typical magnitudes of approximately a few times 10^{-29} and 10^{-19},
respectively. Observational limits on CMB non-Gaussianity from WMAP data allow
us to conservatively set upper limits of a nG, and plausibly sub-nG, on the
present value of the primordial cosmic magnetic field. This represents the
tightest limit so far on the strength of primordial magnetic fields, on Mpc
scales, and is better than limits from the CMB bispectrum and all modes in the
CMB power spectrum. Thus, the CMB trispectrum is a new and more sensitive probe
of primordial magnetic fields on large scales. |
A weak lensing analysis of the PLCK G100.2-30.4 cluster: We present a mass estimate of the Planck-discovered cluster PLCK G100.2-30.4,
derived from a weak lensing analysis of deep SUBARU griz images. We perform a
careful selection of the background galaxies using the multi-band imaging data,
and undertake the weak lensing analysis on the deep (1hr) r-band image. The
shape measurement is based on the KSB algorithm; we adopt the PSFex software to
model the Point Spread Function (PSF) across the field and correct for this in
the shape measurement. The weak lensing analysis is validated through extensive
image simulations. We compare the resulting weak lensing mass profile and total
mass estimate to those obtained from our re-analysis of XMM-Newton
observations, derived under the hypothesis of hydrostatic equilibrium. The
total integrated mass profiles are in remarkably good agreement, agreeing
within 1$\sigma$ across their common radial range. A mass $M_{500} \sim 7
\times 10^{14} M_\odot$ is derived for the cluster from our weak lensing
analysis. Comparing this value to that obtained from our reanalysis of
XMM-Newton data, we obtain a bias factor of (1-b) = 0.8 $\pm$ 0.1. This is
compatible within 1$\sigma$ with the value of (1-b) obtained by Planck
Collaboration XXIV from their calibration of the bias factor using
newly-available weak lensing reconstructed masses. | Thermal and annihilation radiation in the quark nugget model of dark
matter: The Quark Nugget (QN) model of dark matter suggests that the dark matter may
consist of compact composite objects of quark matter. Although such composite
particles can strongly interact with visible matter, they may remain undetected
because of a small cross section to mass ratio. We focus on anti-QNs made of
antiquarks since they are heated by annihilation with visible matter and
radiate. We study the radiation spectrum and power from anti-QNs in our galaxy
and compare them with satellite observations. Thermal radiation from anti-QN is
produced by fluctuations of the positron density. We calculate the thermal
radiation of anti-QNs with the use of the Mie theory and found its ratio to the
black-body radiation. This allows us to find the equilibrium temperature of
anti-QNs in the interstellar medium and determine their contribution to the
observed diffuse background radiation in our galaxy in different frequency
intervals, from radio to UV. We also consider non-thermal radiations from
anti-QNs which are produced by products of annihilations of particles of the
interstellar gas with anti-QNs. Such radiations include photons from decays of
$\pi^0$ mesons, synchrotron, bremsstrahlung and transition radiations from
$\pi^\pm$ mesons, electrons and positrons. Synchrotron radiation in MHz
frequency range and flux of photons from $\pi^0$ decays may be above the
detection threshold in such detectors as Fermi-LAT. |
Simulating Cosmic Reionization and the Radiation Backgrounds from the
Epoch of Reionization: Large-scale reionization simulations are described which combine the results
of cosmological N-body simulations that model the evolving density and velocity
fields and identify the galactic halo sources, with ray-tracing radiative
transfer calculations which model the nonequilibrium ionization of the
intergalactic medium. These simulations have been used to predict some of the
signature effects of reionization on cosmic radiation backgrounds, including
the CMB, near-IR, and redshifted 21cm backgrounds. We summarize some of our
recent progress in this work, and address the question of whether observations
of such signature effects can be used to distinguish the relative contributions
of galaxies of different masses to reionization. | Denoising Gravitational Waves with Enhanced Deep Recurrent Denoising
Auto-Encoders: Denoising of time domain data is a crucial task for many applications such as
communication, translation, virtual assistants etc. For this task, a
combination of a recurrent neural net (RNNs) with a Denoising Auto-Encoder
(DAEs) has shown promising results. However, this combined model is challenged
when operating with low signal-to-noise ratio (SNR) data embedded in
non-Gaussian and non-stationary noise. To address this issue, we design a novel
model, referred to as 'Enhanced Deep Recurrent Denoising Auto-Encoder'
(EDRDAE), that incorporates a signal amplifier layer, and applies curriculum
learning by first denoising high SNR signals, before gradually decreasing the
SNR until the signals become noise dominated. We showcase the performance of
EDRDAE using time-series data that describes gravitational waves embedded in
very noisy backgrounds. In addition, we show that EDRDAE can accurately denoise
signals whose topology is significantly more complex than those used for
training, demonstrating that our model generalizes to new classes of
gravitational waves that are beyond the scope of established denoising
algorithms. |
Testing the wavelength dependence of cosmological redshift down to
$Δz \sim 10^{-6}$: At the core of the standard cosmological model lies the assumption that the
redshift of distant galaxies is independent of photon wavelength. This
invariance of cosmological redshift with wavelength is routinely found in all
galaxy spectra with a precision of $\Delta$z~10$^{-4}$. The combined use of
approximately half a million high-quality galaxy spectra from the Sloan Digital
Sky Survey (SDSS) allows us to explore this invariance down to a nominal
precision in redshift of one part per million (statistical). Our analysis is
performed over the redshift interval 0.02<z<0.25. We use the centroids of
spectral lines over the 3700-6800\AA\ rest-frame optical window. We do not find
any difference in redshift between the blue and red sides down to a precision
of 10$^{-6}$ at z<0.1 and 10$^{-5}$ at 0.1<z<0.25 (i.e. at least an order of
magnitude better than with single galaxy spectra). This is the first time the
wavelength-independence of the (1+z) redshift law is confirmed over a wide
spectral window at this precision level. This result holds independently of the
stellar population of the galaxies and their kinematical properties. This
result is also robust against wavelength calibration issues. The limited
spectral resolution (R~2000) of the SDSS data combined with the asymmetric
wavelength sampling of the spectral features in the observed restframe due to
the (1+z) stretching of the lines prevent our methodology to achieve a
precision higher than 10$^{-5}$, at z>0.1. Future attempts to constrain this
law will require high quality galaxy spectra at higher resolution (R>10,000). | UV/H-alpha Turmoil: A great deal of our understanding of star formation in the local universe has
been built upon an extensive foundation of H-alpha observational studies.
However, recent work in the ultraviolet (UV) with GALEX has shown that star
formation rates (SFRs) inferred from H-alpha in galactic environments
characterized by low stellar and gas densities tend to be less than those based
on the UV luminosity. The origin of the discrepancy is actively debated because
one possible explanation is that the stellar initial mass function is
systematically deficient in high mass stars in such environments. In this
contribution, we summarize our work on this topic using a dwarf galaxy
dominated sample of ~300 late-type galaxies in the 11 Mpc Local Volume. The
sample allows us to examine the discrepancy between H-alpha and UV SFRs using a
statistical number of galaxies with activities less than 0.1 Msun/yr. A range
of potential causes for such an effect are reviewed. We find that while the IMF
hypothesis is not inconsistent with our observations, alternate explanations
remain that must be investigated further before a final conclusion can be
drawn. |
Neutrinos in N-body simulations: In the next decade, cosmological surveys will have the statistical power to
detect the absolute neutrino mass scale. N-body simulations of large-scale
structure formation play a central role in interpreting data from such surveys.
Yet these simulations are Newtonian in nature. We provide a quantitative study
of the limitations to treating neutrinos, implemented as N-body particles, in
N-body codes, focusing on the error introduced by neglecting special
relativistic effects. Special relativistic effects are potentially important
due to the large thermal velocities of neutrino particles in the simulation
box. We derive a self-consistent theory of linear perturbations in Newtonian
and non-relativistic neutrinos and use this to demonstrate that N-body
simulations overestimate the neutrino free-streaming scale, and cause errors in
the matter power spectrum that depend on the initial redshift of the
simulations. For $z_{i} \lesssim 100$, and neutrino masses within the currently
allowed range, this error is $\lesssim 0.5\%$, though represents an up to $\sim
10\%$ correction to the shape of the neutrino-induced suppression to the cold
dark matter power spectrum. We argue that the simulations accurately model
non-linear clustering of neutrinos so that the error is confined to linear
scales. | 3D galaxy clustering with future wide-field surveys: Advantages of a
spherical Fourier-Bessel analysis: Upcoming spectroscopic galaxy surveys are extremely promising to help in
addressing the major challenges of cosmology, in particular in understanding
the nature of the dark universe. The strength of these surveys comes from their
unprecedented depth and width. Optimal extraction of their three-dimensional
information is of utmost importance to best constrain the properties of the
dark universe. Although there is theoretical motivation and novel tools to
explore these surveys using the 3D spherical Fourier-Bessel (SFB) power
spectrum of galaxy number counts $C_\ell(k,k^\prime)$, most survey
optimisations and forecasts are based on the tomographic spherical harmonics
power spectrum $C^{(ij)}_\ell$. We performed a new investigation of the
information that can be extracted from the tomographic and 3D SFB techniques by
comparing the forecast cosmological parameter constraints obtained from a
Fisher analysis in the context of planned stage IV wide-field galaxy surveys.
The comparison was made possible by careful and coherent treatment of
non-linear scales in the two analyses. Nuisance parameters related to a scale-
and redshift-dependent galaxy bias were also included for the first time in the
computation of both the 3D SFB and tomographic power spectra. Tomographic and
3D SFB methods can recover similar constraints in the absence of systematics.
However, constraints from the 3D SFB analysis are less sensitive to unavoidable
systematics stemming from a redshift- and scale-dependent galaxy bias. Even for
surveys that are optimised with tomography in mind, a 3D SFB analysis is more
powerful. In addition, for survey optimisation, the figure of merit for the 3D
SFB method increases more rapidly with redshift, especially at higher
redshifts, suggesting that the 3D SFB method should be preferred for designing
and analysing future wide-field spectroscopic surveys. |
The Q Continuum Simulation: Harnessing the Power of GPU Accelerated
Supercomputers: Modeling large-scale sky survey observations is a key driver for the
continuing development of high resolution, large-volume, cosmological
simulations. We report the first results from the 'Q Continuum' cosmological
N-body simulation run carried out on the GPU-accelerated supercomputer Titan.
The simulation encompasses a volume of (1300 Mpc)^3 and evolves more than half
a trillion particles, leading to a particle mass resolution of ~1.5 X 10^8
M_sun. At this mass resolution, the Q Continuum run is currently the largest
cosmology simulation available. It enables the construction of detailed
synthetic sky catalogs, encompassing different modeling methodologies,
including semi-analytic modeling and sub-halo abundance matching in a large,
cosmological volume. Here we describe the simulation and outputs in detail and
present first results for a range of cosmological statistics, such as mass
power spectra, halo mass functions, and halo mass-concentration relations for
different epochs. We also provide details on challenges connected to running a
simulation on almost 90% of Titan, one of the fastest supercomputers in the
world, including our usage of Titan's GPU accelerators. | The Baryonic Acoustic Feature and Large-Scale Clustering in the SDSS LRG
Sample: We examine the correlation function \xi of the Sloan Digital Sky Survey
(SDSS) Luminous Red Galaxy sample (LRG) at large scales (60<s<400 Mpc/h) using
the final data release (DR7; 105,831 LRGs between 0.16<z<0.47). Using mock
catalogs, we demonstrate that the observed baryonic acoustic peak and larger
scale signal are consistent with LCDM at the 1.5\sigma level. The signal at
155<s<200 Mpc/h tends to be high relative to theoretical expectations; this
slight deviation can be attributed to a bright subsample of the LRGs. Fitting
data to a non-linear, redshift-space, template based-model, we constrain the
peak position at s_p=103.6+3.6-2.4 Mpc/h when fitting the range 60<s<150 Mpc/h
(1\sigma uncertainties measured from the mocks. This redshift-space distance
s_p is related to the comoving sound horizon scale r_s after taking into
account matter clustering non-linearities, redshift distortions and galaxy
clustering bias. Mock catalogs show that the probability that a DR7-sized
sample would not have an identifiable peak is at least 10%. As a consistency
check of a fiducial cosmology, we use the observed s_p to obtain the distance
D_V=[(1+z)^2D_A^2cz/H(z)]^(1/3) relative to the acoustic scale. We find
r_s/D_V(z=0.278)=0.1394+-0.0049. This result is in excellent agreement with
Percival et. al (2009), who examine roughly the same data set, but using the
power spectrum. Comparison with other determinations in the literature are also
in very good agreement. We have tested our results against a battery of
possible systematic effects, finding all effects are smaller than our estimated
sample variance. |
Statistical properties of dark matter mini-haloes at z >= 15: Understanding the formation of the first objects in the universe critically
depends on knowing whether the properties of small dark matter structures at
high-redshift (z > 15) are different from their more massive lower-redshift
counterparts. To clarify this point, we performed a high-resolution N-body
simulation of a cosmological volume 1 Mpc/h comoving on a side, reaching the
highest mass resolution to date in this regime. We make precision measurements
of various physical properties that characterize dark matter haloes (such as
the virial ratio, spin parameter, shape, and formation times, etc.) for the
high-redshift (z > 15) dark matter mini-haloes we find in our simulation, and
compare them to literature results and a moderate-resolution comparison run
within a cube of side-length 100 Mpc/h. We find that dark matter haloes at
high-redshift have a log-normal distribution of the dimensionless spin
parameter centered around {\lambda} $\sim$ 0.03, similar to their more massive
counterparts. They tend to have a small ratio of the length of the shortest
axis to the longest axis (sphericity), and are highly prolate. In fact, haloes
of given mass that formed recently are the least spherical, have the highest
virial ratios, and have the highest spins. Interestingly, the formation times
of our mini-halos depend only very weakly on mass, in contrast to more massive
objects. This is expected from the slope of the linear power spectrum of
density perturbations at this scale, but despite this difference, dark matter
structures at high-redshift share many properties with their much more massive
counterparts observed at later times. | Effect of asymmetry of the radio source distribution on the apparent
proper motion kinematic analysis: A new list of physical characteristics of 4261 astrometric radio sources,
including all 717 ICRF-Ext.2 sources has been compiled. Comparison of our data
of optical characteristics with the official International Earth Rotation and
Reference Systems Service (IERS) list showed significant discrepancies for
about half of 667 common sources. We also found that asymmetry in the radio
sources distribution between hemispheres could cause significant correlation
between the vector spherical harmonics, especially if the case of sparse
distribution of the sources with high redshift. We identified radio sources
having many-year observation history and lack redshift. This sources should be
urgently observed at large optical telescopes. The list of optical
characteristics created in this paper is recommended for use as a supplement
material for the next International Celestial Reference Frame (ICRF)
realization. It can be also effectively used for cosmological studies and
planning of observing programs both in radio and optics. |
A Tilt Instability in the Cosmological Principle: We show that the Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) framework has
an instability towards the growth of fluid flow anisotropies, even if the
Universe is accelerating. This flow (tilt) instability in the matter sector is
invisible to Cosmic No-Hair Theorem-like arguments, which typically only flag
shear anisotropies in the metric. We illustrate our claims in the setting of
``dipole cosmology'', the maximally Copernican generalization of FLRW that can
accommodate a flow. Simple models are sufficient to show that the cosmic flow
need not track the shear, even in the presence of a positive cosmological
constant. We also emphasize that the growth of the tilt hair is fairly generic
if the total equation of state $w(t) \rightarrow -1$ at late times (as it does
in standard cosmology), irrespective of the precise model of dark energy. The
generality of our theoretical result puts various recent observational claims
about late time anisotropies and cosmic dipoles in a new light. | Effect of Magnetic Field Dissipation on Primordial Li Abundance: The dissipation effects of primordial magnetic fields on the primordial
elemental abundances were investigated. When a magnetic field reconnects, its
energy is converted to the kinetic energy of charged particles, as observed for
solar energetic particles arriving on earth. This accelerates the cosmic
background nuclei, and energetic nuclei induce nonthermal reactions. A
constraint on the dissipation is derived from a theoretical calculation of the
nonthermal reactions during Big Bang nucleosynthesis. We found that
observations of the Li and D abundances can be explained if 0.01--0.1 % of the
cosmic energy density was utilized for nuclear acceleration after the
electron--positron annihilation epoch. Reconnections of such amplitudes of
magnetic fields generate outgoing jets, the bulk velocity of which evolves to
values appropriate for cosmic ray (CR) nuclear energies of 0.1--1 MeV necessary
for successful CR nucleosynthesis. Therefore, acceleration of cosmic background
nuclei during the dissipation of primordial magnetic fields is a possible
generation mechanism of soft CRs that has been suggested as a solution to the
cosmic Li problem. Among the solutions suggested without exotic physics, only
the dissipating magnetic field model suggested here explains observations of
both low Li and high D abundances. Our results demonstrate that signatures of
strong magnetic fields in the early universe have been observed in primordial
elemental abundances. |
Probing the Long Gamma-Ray Burst Progenitor by Lyman-alpha Emission of
Host Galaxies: Long gamma-ray bursts (GRBs) have been suggested to occur preferentially in
low metallicity environment. We discuss the possibility and theoretical aspects
of using Lyman alpha emission properties of long GRB host galaxies as a
metallicity indicator of high redshift GRB environments, where direct
metallicity measurements are not easy. We propose to use the fraction of
Ly-alpha emitters (LAEs) in long GRB host galaxies as a function of UV
luminosity, which can be compared with star-formation-rate weighted LAE
fraction of Lyman-break galaxies as the standard in the case of no metallicity
dependence. There are two important effects of metallicity dependence of long
GRB rate to change the LAE fraction of host galaxies. One is the enhancement of
intrinsic Ly-alpha equivalent width (EW) by stronger ionizing UV luminosity of
low metallicity stellar population, and the other is extinction by interstellar
dust to change the observable EW. Based on a latest theoretical model of LAEs
that reproduce observations, we argue that the latter is likely to work in the
opposite direction to the former, i.e., to decrease LAE fraction if GRBs
preferentially occur in low-metallicity environments, because of the clumpy
inter-stellar medium effect. The high LAE fraction of GRB host galaxies
indicated by observations is quantitatively be explained by the LAE model if
GRBs occur when Z < 0.1Z_sun, although this result is still indicative because
of the limited statistics and theoretical uncertainties. This result
demonstrates that the LAE statistics of GRB hosts may give us useful
information in the future. | The decisive future of inflation: How much more will we learn about single-field inflationary models in the
future? We address this question in the context of Bayesian design and
information theory. We develop a novel method to compute the expected utility
of deciding between models and apply it to a set of futuristic measurements.
This necessarily requires one to evaluate the Bayesian evidence many thousands
of times over, which is numerically challenging. We show how this can be done
using a number of simplifying assumptions and discuss their validity. We also
modify the form of the expected utility, as previously introduced in the
literature in different contexts, in order to partition each possible future
into either the rejection of models at the level of the maximum likelihood or
the decision between models using Bayesian model comparison. We then quantify
the ability of future experiments to constrain the reheating temperature and
the scalar running. Our approach allows us to discuss possible strategies for
maximising information from future cosmological surveys. In particular, our
conclusions suggest that, in the context of inflationary model selection, a
decrease in the measurement uncertainty of the scalar spectral index would be
more decisive than a decrease in the uncertainty in the tensor-to-scalar ratio.
We have incorporated our approach into a publicly available python class, foxi
(https://sites.google.com/view/foxicode), that can be readily applied to any
survey optimisation problem. |
Cosmic dissonance: new physics or systematics behind a short sound
horizon?: Persistent tension between low-redshift observations and the Cosmic Microwave
Background radiation (CMB), in terms of two fundamental distance scales set by
the sound horizon $r_d$ and the Hubble constant $H_0$, suggests new physics
beyond the Standard Model or residual systematics. We examine recently updated
distance calibrations from Cepheids, gravitational lensing time-delay
observations, and the Tip of the Red Giant Branch. Calibrating the Baryon
Acoustic Oscillations (BAO) and Type Ia supernovae with combinations of the
distance indicators, we obtain a joint and self-consistent measurement of $H_0$
and $r_d$ at low redshift, independent of cosmological models and CMB
inference. In an attempt to alleviate the tension between late-time and
CMB-based measurements, we consider four extensions of the standard
$\Lambda$CDM model. The sound horizon from our different measurements is
$r_d=(137\pm3^{stat.}\pm2^{syst.})$~Mpc. Depending on the adopted distance
indicators, the $combined$ tension in $H_0$ and $r_d$ ranges between 2.3 and
5.1 $\sigma$. We find that modifications of $\Lambda$CDM that change the
physics after recombination fail to solve the problem, for the reason that they
only resolve the tension in $H_0$, while the tension in $r_d$ remains
unchanged. Pre-recombination extensions (with early dark energy or the
effective number of neutrinos $\rm{N}_{\rm{eff}}=3.24 \pm 0.16$) are allowed by
the data, unless the calibration from Cepheids is included. Results from
time-delay lenses are consistent with those from distance-ladder calibrations
and point to a discrepancy between absolute distance scales measured from the
CMB (assuming the standard cosmological model) and late-time observations. New
proposals to resolve this tension should be examined with respect to
reconciling not only the Hubble constant but also the sound horizon derived
from the CMB and other cosmological probes. | Evolution of perturbations and cosmological constraints in decaying dark
matter models with arbitrary decay mass products: Decaying dark matter (DDM) is a candidate which can solve the discrepancies
between predictions of the concordance $\Lambda$CDM model and observations at
small scales such as the number counts of companion galaxies of the Milky Way
and the density profile at the center of galaxies. Previous studies are limited
to the cases where the decay particles are massless and/or have almost
degenerate masses with that of mother particles. Here we expand the DDM models
so that one can consider the DDM with arbitrary lifetime and the decay products
with arbitrary masses. We calculate the time evolutions of perturbed
phase-space distribution functions of decay products for the first time and
study effects of DDM on the temperature anisotropy in the cosmic microwave
background and the matter power spectrum at present. From a recent
observational estimate of $\sigma_{8}$, we derive constraints on the lifetime
of DDM and the mass ratio between the decay products and DDM. We also discuss
implications of the DDM model for the discrepancy in the measurements of
$\sigma_8$ recently claimed by the Planck satellite collaboration. |
Kinetics of spontaneous baryogenesis in non-stationary background: Generation of the cosmological baryon asymmetry in frameworks of spontaneous
baryogenesis is studied in detail. It is shown that the relation between
baryonic chemical potential and the time derivative of the (pseudo)Goldstone
field essentially depends upon the representation chosen for the fermionic
fields with non-zero baryonic number (quarks). Kinetic equation is modified and
numerically solved in equilibrium for the case of time dependent external
background or finite integration time to be applicable to the case when energy
conservation law is formally violated. | Inferring the Age of the Universe with Globular Clusters: We present an estimate of the absolute age of 68 galactic globular clusters
obtained by exploiting the distribution of stars in the full color-magnitude
diagram. In particular, we jointly estimate the absolute age, distance,
reddening, metallicity ([Fe/H]) and [$\alpha$/Fe] of each cluster, imposing
priors motivated by independent observations; we also estimate possible
systematics from stellar modeling. Our derived distances for the globular
cluster sample are in agreement with those obtained from GAIA using
main-sequence dwarf stars (where available), and the inferred ages are in good
agreement with those previously published. The novelty of our approach is that,
with the adopted priors, we are able to estimate robustly these parameters from
the globular cluster color-magnitude diagram. We find that the average age of
the oldest globular clusters is $t_{\rm GC}=13.32 \pm 0.1 {\rm (stat.)} \pm 0.5
{\rm (sys.)}$, at 68\% confidence level, including systematic uncertainties
from stellar modeling. These measurements can be used to infer the age of the
Universe, largely independently of the cosmological parameters: we find an age
of the Universe $t_{\rm U}=13.5^{+0.16}_{-0.14} {\rm (stat.)} \pm 0.5 ({\rm
sys.})$ at 68\% confidence level, accounting for the formation time of globular
clusters and its uncertainty. This value is compatible with $13.8 \pm 0.02$
Gyr, the cosmological model-dependent value inferred by the Planck mission
assuming the $\Lambda$CDM model. |
Quintessential Scale Dependence from Separate Universe Simulations: By absorbing fluctuations into a local background, separate universe
simulations provide a powerful technique to characterize the response of
small-scale observables to the long-wavelength density fluctuations, for
example those of the power spectrum and halo mass function which lead to the
squeezed-limit $n$-point function and halo bias, respectively. Using
quintessence dark energy as the paradigmatic example, we extend these
simulation techniques to cases where non-gravitational forces in other sectors
establish a Jeans scale across which the growth of density fluctuations becomes
scale dependent. By characterizing the separate universes with matching
background expansion histories, we show that the power spectrum and mass
function responses depend on whether the long-wavelength mode is above or below
the Jeans scale. Correspondingly, the squeezed bispectrum and halo bias also
become scale dependent. Models of bias that are effectively local in the
density field at a single epoch, initial or observed, cannot describe this
effect which highlights the importance of temporal nonlocality in structure
formation. Validated by these quintessence tests, our techniques are applicable
to a wide range of models where the complex dynamics of additional fields
affect the clustering of matter in the linear regime and it would otherwise be
difficult to simulate their impact in the nonlinear regime. | Can axion-like particles explain the alignments of the polarisations of
light from quasars?: The standard axion-like particle explanation of the observed large-scale
coherent orientations of quasar polarisation vectors is ruled out by the recent
measurements of vanishing of circular polarisation. We introduce a more general
wave-packet formalism and show that, although decoherence effects between waves
of different frequencies can reduce significantly the amount of circular
polarisation, the axion-like particle hypothesis is disfavoured given the
bandwidth with which part of the observations were performed. Finally, we show
that a more sophisticated model of extragalactic fields does not lead to an
alignment of polarisations. |
The CluMPR Galaxy Cluster-Finding Algorithm and DESI Legacy Survey
Galaxy Cluster Catalogue: Galaxy clusters enable unique opportunities to study cosmology, dark matter,
galaxy evolution, and strongly-lensed transients. We here present a new
cluster-finding algorithm, CluMPR (Clusters from Masses and Photometric
Redshifts), that exploits photometric redshifts (photo-z's) as well as
photometric stellar mass measurements. CluMPR uses a 2-dimensional binary
search tree to search for overdensities of massive galaxies with similar
redshifts on the sky and then probabilistically assigns cluster membership by
accounting for photo-z uncertainties. We leverage the deep DESI Legacy Survey
grzW1W2 imaging over one-third of the sky to create a catalogue of ~ 300,000
galaxy cluster candidates out to z = 1, including tabulations of member
galaxies and estimates of each cluster's total stellar mass. Compared to other
methods, CluMPR is particularly effective at identifying clusters at the high
end of the redshift range considered (z = 0.75-1), with minimal contamination
from low-mass groups. These characteristics make it ideal for identifying
strongly lensed high-redshift supernovae and quasars that are powerful probes
of cosmology, dark matter, and stellar astrophysics. As an example application
of this cluster catalogue, we present a catalogue of candidate wide-angle
strongly-lensed quasars in Appendix C. The five best candidates identified from
this sample include two known lensed quasar systems and a possible
changing-look lensed QSO with SDSS spectroscopy. All code and catalogues
produced in this work are publicly available (see Data Availability). | Slicing the Torus: Obscuring Structures in Quasars: Quasars and Active Galactic Nuclei (AGNs) are often obscured by dust and gas.
It is normally assumed that the obscuration occurs in an oblate "obscuring
torus", that begins at the radius at which the most refractive dust can remain
solid. The most famous form of this torus is a donut-shaped region of molecular
gas with a large scale-height. While this model is elegant and accounts for
many phenomena at once, it does not hold up to detailed tests. Instead the
obscuration in AGNs must occur on a wide range of scales and be due to a
minimum of three physically distinct absorbers. Slicing the "torus" into these
three regions will allow interesting physics of the AGN to be extracted. |
The Chandra Multi-Wavelength Project: Optical Spectroscopy and the
Broadband Spectral Energy Distributions of X-ray Selected AGN: From optical spectroscopy of X-ray sources observed as part of ChaMP, we
present redshifts and classifications for a total of 1569 Chandra sources from
our targeted spectroscopic follow up using the FLWO, SAAO, WIYN, CTIO, KPNO,
Magellan, MMT and Gemini telescopes, and from archival SDSS spectroscopy. We
classify the optical counterparts as 50% BLAGN, 16% NELG, 14% ALG, and 20%
stars. We detect QSOs out to z~5.5 and galaxies out to z~3. We have compiled
extensive photometry from X-ray to radio bands. Together with our spectroscopic
information, this enables us to derive detailed SEDs for our extragalactic
sources. We fit a variety of templates to determine bolometric luminosities,
and to constrain AGN and starburst components where both are present. While
~58% of X-ray Seyferts require a starburst event to fit observed photometry
only 26% of the X-ray QSO population appear to have some kind of star formation
contribution. This is significantly lower than for the Seyferts, especially if
we take into account torus contamination at z>1 where the majority of our X-ray
QSOs lie. In addition, we observe a rapid drop of the percentage of starburst
contribution as X-ray luminosity increases. This is consistent with the
quenching of star formation by powerful QSOs, as predicted by the merger model,
or with a time lag between the peak of star formation and QSO activity. We have
tested the hypothesis that there should be a strong connection between X-ray
obscuration and star-formation but we do not find any association between X-ray
column density and star formation rate both in the general population or the
star-forming X-ray Seyferts. Our large compilation also allows us to report
here the identification of 81 XBONG, 78 z>3 X-ray sources and 8 Type-2 QSO
candidates. Also we have identified the highest redshift (z=5.4135) X-ray
selected QSO with optical spectroscopy. | Estimating the contribution of foreground halos to the FRB 180924
dispersion measure: Fast Radio Burst (FRB) dispersion measures (DMs) record the presence of
ionized baryons that are otherwise invisible to other techniques enabling
resolution of the matter distribution in the cosmic web. In this work, we aim
to estimate the contribution to FRB 180924 DM from foreground galactic halos.
Localized by ASKAP to a massive galaxy, this sightline is notable for an
estimated cosmic web contribution to the DM ($\rm DM_{cosmic} =
220~pc~cm^{-3}$), which is less than the average value at the host redshift
($\rm z = 0.3216$) estimated from the Macquart relation ($280~\rm pc~cm^{-3}$).
In the favored models of the cosmic web, this suggests few intersections with
foreground halos at small impact parameters ($\lesssim 100$ kpc). To test this
hypothesis, we carried out spectroscopic observations of the field galaxies
within $\sim$1' of the sightline with VLT/MUSE and Keck/LRIS. Furthermore, we
developed a probabilistic methodology that leverages photometric redshifts
derived from wide-field DES and WISE imaging. We conclude that there is no
galactic halo that closely intersects the sightline and also that the net DM
contribution from halos, $\rm DM_{halos}< 45~pc~cm^{-3}$ (95 % c.l.). This
value is lower than the $\rm DM_{halos}$ estimated from an "average" sightline
($121~\rm pc~cm^{-3}$) using the Planck $\Lambda CDM$ model and the Aemulus
halo mass function and reasonably explains its low $\rm DM_{cosmic}$ value. We
conclude that FRB 180924 represents the predicted majority of sightlines in the
universe with no proximate foreground galactic halos. Our framework lays the
foundation for a comprehensive analysis of FRB fields in the near future. |
Star Formation Quenching in High-redshift Large-scale Structure:
Post-starburst Galaxies in the Cl1604 Supercluster at $z \sim 0.9$: The Cl1604 supercluster at $z \sim 0.9$ is one of the most extensively
studied high redshift large scale structures, with more than 500
spectroscopically confirmed members. It consists of 8 clusters and groups, with
members numbering from a dozen to nearly a hundred, providing a broad range of
environments for investigating the large scale environmental effects on galaxy
evolution. Here we examine the properties of 48 post-starburst galaxies in
Cl1604, comparing them to other galaxy populations in the same supercluster.
Incorporating photometry from ground-based optical and near-infrared imaging,
along with $Spitzer$ mid-infrared observations, we derive stellar masses for
all Cl1604 members. The colors and stellar masses of the K+A galaxies support
the idea that they are progenitors of red sequence galaxies. Their
morphologies, residual star-formation rates, and spatial distributions suggest
galaxy mergers may be the principal mechanism producing post-starburst
galaxies. Interaction between galaxies and the dense intra-cluster medium is
also effective, but only in the cores of dynamically evolved clusters. The
prevalence of post-starburst galaxies in clusters correlates with the dynamical
state of the host cluster, as both galaxy mergers and the dense intra-cluster
medium produce post-starburst galaxies. We also investigate the incompleteness
and contamination of K+A samples selected by means of H$\delta$ and [OII]
equivalent widths. K+A samples may be up to $\sim50\%$ incomplete due to the
presence of LINER/Seyferts and up to $\sim30\%$ of K+A galaxies could have
substantial star formation activity. | Constraints on the Topology of the Universe: Extension to General
Geometries: We present an update to the search for a non-trivial topology of the universe
by searching for matching circle pairs in the cosmic microwave background using
the WMAP 7 year data release. We extend the exisiting bounds to encompass a
wider range of possible topologies by searching for matching circle pairs with
opening angles 10 degree < \alpha < 90 degree and separation angles 11 degree <
\theta < 180 degree. The extended search reveal two small anomalous regions in
the CMB sky. Numerous pairs of well-matched circles are found where both
circles pass through one or the other of those regions. As this is not the
signature of any known manifold, but is a likely consequence of contamination
in those sky regions, we repeat the search excluding circle pairs where both
pass through either of the two regions. We then find no statistically
significant pairs of matched circles, and so no hints of a non-trivial
topology. The absence of matched circles increases the lower limit on the
length of the shortest closed null geodesic that self-intersects at our
location in the universe (equivalently the injectivity radius at our location)
to 98.5% of the diameter of the last scattering surface or approximately 26
Gpc. It extends the limit to any manifolds in which the intersecting arcs of
said geodesic form an angle greater than 10^o. |
Alpha, Betti and the Megaparsec Universe: on the Topology of the Cosmic
Web: We study the topology of the Megaparsec Cosmic Web in terms of the
scale-dependent Betti numbers, which formalize the topological information
content of the cosmic mass distribution. While the Betti numbers do not fully
quantify topology, they extend the information beyond conventional cosmological
studies of topology in terms of genus and Euler characteristic. The richer
information content of Betti numbers goes along the availability of fast
algorithms to compute them.
For continuous density fields, we determine the scale-dependence of Betti
numbers by invoking the cosmologically familiar filtration of sublevel or
superlevel sets defined by density thresholds. For the discrete galaxy
distribution, however, the analysis is based on the alpha shapes of the
particles. These simplicial complexes constitute an ordered sequence of nested
subsets of the Delaunay tessellation, a filtration defined by the scale
parameter, $\alpha$. As they are homotopy equivalent to the sublevel sets of
the distance field, they are an excellent tool for assessing the topological
structure of a discrete point distribution. In order to develop an intuitive
understanding for the behavior of Betti numbers as a function of $\alpha$, and
their relation to the morphological patterns in the Cosmic Web, we first study
them within the context of simple heuristic Voronoi clustering models.
Subsequently, we address the topology of structures emerging in the standard
LCDM scenario and in cosmological scenarios with alternative dark energy
content. The evolution and scale-dependence of the Betti numbers is shown to
reflect the hierarchical evolution of the Cosmic Web and yields a promising
measure of cosmological parameters. We also discuss the expected Betti numbers
as a function of the density threshold for superlevel sets of a Gaussian random
field. | COMAP Early Science: VII. Prospects for CO Intensity Mapping at
Reionization: We introduce COMAP-EoR, the next generation of the Carbon Monoxide Mapping
Array Project aimed at extending CO intensity mapping to the Epoch of
Reionization. COMAP-EoR supplements the existing 30 GHz COMAP Pathfinder with
two additional 30 GHz instruments and a new 16 GHz receiver. This combination
of frequencies will be able to simultaneously map CO(1--0) and CO(2--1) at
reionization redshifts ($z\sim5-8$) in addition to providing a significant
boost to the $z\sim3$ sensitivity of the Pathfinder. We examine a set of
existing models of the EoR CO signal, and find power spectra spanning several
orders of magnitude, highlighting our extreme ignorance about this period of
cosmic history and the value of the COMAP-EoR measurement. We carry out the
most detailed forecast to date of an intensity mapping cross-correlation, and
find that five out of the six models we consider yield signal to noise ratios
(S/N) $\gtrsim20$ for COMAP-EoR, with the brightest reaching a S/N above 400.
We show that, for these models, COMAP-EoR can make a detailed measurement of
the cosmic molecular gas history from $z\sim2-8$, as well as probe the
population of faint, star-forming galaxies predicted by these models to be
undetectable by traditional surveys. We show that, for the single model that
does not predict numerous faint emitters, a COMAP-EoR-type measurement is
required to rule out their existence. We briefly explore prospects for a
third-generation Expanded Reionization Array (COMAP-ERA) capable of detecting
the faintest models and characterizing the brightest signals in extreme detail. |
Curvaton model completed: In an inflationary cosmology, the observed primoridal density perturbation
could come from the quantum fluctuations of another light 'curvaton' field,
rather than the inflaton. In this case, it is essential that the curvaton
decays, converting its perturbation to an adiabatic perturbation. For the first
time, we consistently account for this decay in the simplest curvaton model
V(\sigma) = (m^2\sigma^2)/2 and point out that it gives rise to an important
logarithmic correction to the potential. Moreover, the potential will also
receive a correction from the thermal bath. As a consequence, the dynamics of
the curvaton are substantially altered compared to the original model in the
majority of the parameter space. It will therefore be necessary to re-calculate
all the predictions of the original model. | Primordial black hole production during preheating in a chaotic
inflationary model: In this paper we review the production of primordial black holes (PBHs)
during preheating after a chaotic inflationary model. All relevant equations of
motion are solved numerically in a modified version of HLattice, and we then
calculate the mass variance to determine structure formation during preheating.
It is found that production of PBHs can be a generic result of the model, even
though the results seem to be sensitive to the values of the smoothing scale.
We consider a constraint for overproduction of PBHs that could uncover some
stress between inflation-preheating models and observations. |
The Millennium Run Observatory: First Light: Simulations of galaxy evolution aim to capture our current understanding as
well as to make predictions for testing by future experiments. Simulations and
observations are often compared in an indirect fashion: physical quantities are
estimated from the data and compared to models. However, many applications can
benefit from a more direct approach, where the observing process is also
simulated and the models are seen fully from the observer's perspective. To
facilitate this, we have developed the Millennium Run Observatory (MRObs), a
theoretical virtual observatory which uses virtual telescopes to `observe'
semi-analytic galaxy formation models based on the suite of Millennium Run dark
matter simulations. The MRObs produces data that can be processed and analyzed
using the standard software packages developed for real observations. At
present, we produce images in forty filters from the rest-frame UV to IR for
two stellar population synthesis models, three different models of IGM
absorption, and two cosmologies (WMAP1/7). Galaxy distributions for a large
number of mock lightcones can be `observed' using models of major ground- and
space-based telescopes. The data include lightcone catalogues linked to
structural properties of galaxies, pre-observation model images, mock telescope
images, and Source Extractor products that can all be traced back to the higher
level dark matter, semi-analytic galaxy, and lightcone catalogues available in
the Millennium database. Here, we describe our methods and announce a first
public release of simulated surveys (e.g., SDSS, CFHT-LS, GOODS, GOODS/ERS,
CANDELS, and HUDF). The MRObs browser, an online tool, further facilitates
exploration of the simulated data. We demonstrate the benefits of a direct
approach through a number of example applications (galaxy number counts in
CANDELS, clusters, morphologies, and dropout selections). | A Hubble Space Telescope Study of Lyman Limit Systems: Census and
Evolution: We present a survey for optically thick Lyman limit absorbers at z<2.6 using
archival Hubble Space Telescope observations with the Faint Object Spectrograph
and Space Telescope Imaging Spectrograph. We identify 206 Lyman limit systems
(LLSs) increasing the number of catalogued LLSs at z<2.6 by a factor of ~10. We
compile a statistical sample of 50 tau_LLS > 2 LLSs drawn from 249 QSO sight
lines that avoid known targeting biases. The incidence of such LLSs per unit
redshift, l(z)=dn/dz, at these redshifts is well described by a single power
law, l(z) = C1 (1+z)^gamma, with gamma=1.33 +/- 0.61 at z<2.6, or with
gamma=1.83 +/- 0.21 over the redshift range 0.2 < z < 4.9. The incidence of
LLSs per absorption distance, l(X), decreases by a factor of ~1.5 over the ~0.6
Gyr from z=4.9 to 3.5; l(X) evolves much more slowly at low redshifts,
decreasing by a similar factor over the ~8 Gyr from z=2.6 to 0.25. We show that
the column density distribution function, f(N(HI)), at low redshift is not well
fitted by a single power law index (f(N(HI)) = C2 N(HI)^(-beta)) over the
column density range 13 < log N(HI) < 22 or log N(HI) >17.2. While low and high
redshift f(N(HI)) distributions are consistent for log N(HI)>19.0, there is
some evidence that f(N(HI)) evolves with z for log N(HI) < 17.7, possibly due
to the evolution of the UV background and galactic feedback. Assuming LLSs are
associated with individual galaxies, we show that the physical cross section of
the optically thick envelopes of galaxies decreased by a factor of ~9 from z~5
to 2 and has remained relatively constant since that time. We argue that a
significant fraction of the observed population of LLSs arises in the
circumgalactic gas of sub-L* galaxies. |
Constraints on the Galactic Halo Dark Matter from Fermi-LAT Diffuse
Measurements: We have performed an analysis of the diffuse gamma-ray emission with the
Fermi Large Area Telescope in the Milky Way Halo region searching for a signal
from dark matter annihilation or decay. In the absence of a robust dark matter
signal, constraints are presented. We consider both gamma rays produced
directly in the dark matter annihilation/decay and produced by inverse Compton
scattering of the e+e- produced in the annihilation/decay. Conservative limits
are derived requiring that the dark matter signal does not exceed the observed
diffuse gamma-ray emission. A second set of more stringent limits is derived
based on modeling the foreground astrophysical diffuse emission using the
GALPROP code. Uncertainties in the height of the diffusive cosmic-ray halo, the
distribution of the cosmic-ray sources in the Galaxy, the index of the
injection cosmic-ray electron spectrum and the column density of the
interstellar gas are taken into account using a profile likelihood formalism,
while the parameters governing the cosmic-ray propagation have been derived
from fits to local cosmic-ray data. The resulting limits impact the range of
particle masses over which dark matter thermal production in the early Universe
is possible, and challenge the interpretation of the PAMELA/Fermi-LAT cosmic
ray anomalies as annihilation of dark matter. | The Atacama Cosmology Telescope: limits on dark matter-baryon
interactions from DR4 power spectra: Diverse astrophysical observations suggest the existence of cold dark matter
that interacts only gravitationally with radiation and ordinary baryonic
matter. Any nonzero coupling between dark matter and baryons would provide a
significant step towards understanding the particle nature of dark matter.
Measurements of the cosmic microwave background (CMB) provide constraints on
such a coupling that complement laboratory searches. In this work we place
upper limits on a variety of models for dark matter elastic scattering with
protons and electrons by combining large-scale CMB data from the Planck
satellite with small-scale information from Atacama Cosmology Telescope (ACT)
DR4 data. In the case of velocity-independent scattering, we obtain bounds on
the interaction cross section for protons that are 40\% tighter than previous
constraints from the CMB anisotropy. For some models with velocity-dependent
scattering we find best-fitting cross sections with a 2$\sigma$ deviation from
zero, but these scattering models are not statistically preferred over
$\Lambda$CDM in terms of model selection. |
KiDS-Legacy calibration: unifying shear and redshift calibration with
the SKiLLS multi-band image simulations: We present SKiLLS, a suite of multi-band image simulations for the weak
lensing analysis of the complete Kilo-Degree Survey (KiDS), dubbed KiDS-Legacy
analysis. The resulting catalogues enable joint shear and redshift calibration,
enhancing the realism and hence accuracy over previous efforts. To create a
large volume of simulated galaxies with faithful properties and to a sufficient
depth, we integrated cosmological simulations with high-quality imaging
observations. We also improved the realism of simulated images by allowing the
point spread function (PSF) to differ between CCD images, including stellar
density variations and varying noise levels between pointings. Using realistic
variable shear fields, we accounted for the impact of blended systems at
different redshifts. Although the overall correction is minor, we found a clear
redshift-bias correlation in the blending-only variable shear simulations,
indicating the non-trivial impact of this higher-order blending effect. We also
explored the impact of the PSF modelling errors and found a small yet
noticeable effect on the shear bias. Finally, we conducted a series of
sensitivity tests, including changing the input galaxy properties. We conclude
that our fiducial shape measurement algorithm, lensfit, is robust within the
requirements of lensing analyses with KiDS. As for future weak lensing surveys
with tighter requirements, we suggest further investments in understanding the
impact of blends at different redshifts, improving the PSF modelling algorithm
and developing the shape measurement method to be less sensitive to the galaxy
properties. | Understanding the cosmic web: We investigate the characteristics and the time evolution of the cosmic web
from redshift, z=2, to present time, within the framework of the NEXUS+
algorithm. This necessitates the introduction of new analysis tools optimally
suited to describe the very intricate and hierarchical pattern that is the
cosmic web. In particular, we characterize filaments (walls) in terms of their
linear (surface) mass density. This is very good in capturing the evolution of
these structures. At early times the cosmos is dominated by tenuous filaments
and sheets, which, during subsequent evolution, merge together, such that the
present day web is dominated by fewer, but much more massive, structures. We
also show that voids are more naturally described in terms of their boundaries
and not their centres. We illustrate this for void density profiles, which,
when expressed as a function of the distance from void boundary, show a
universal profile in good qualitative agreement with the theoretical
shell-crossing framework of expanding underdense regions. |
A non-linear solution to the $S_8$ tension?: Weak galaxy lensing surveys have consistently reported a lower amplitude for
the matter fluctuation spectrum, as measured by the $S_8$ parameter, than
expected in the $\Lambda{\rm CDM}$ cosmology favoured by $Planck$. However, the
expansion history follows the predictions of the $Planck$ $\Lambda{\rm CDM}$
cosmology to high accuracy, as do measurements of lensing of the cosmic
microwave background anisotropies. Redshift space distortion measurements also
appear to be consistent with $Planck$ $\Lambda{\rm CDM}$. In this paper, we
argue that these observations can be reconciled with the $Planck$ $\Lambda{\rm
CDM}$ cosmology if the matter power spectrum is suppressed more strongly on
non-linear scales than assumed in analyses of weak galaxy lensing. We
demonstrate this point by fitting a one-parameter model, characterising a
suppression of the non-linear power spectrum, to the KiDS-1000 weak lensing
measurements. Such a suppression could be attributed to new properties of the
dark matter that affect non-linear scales, or to a response of the matter
fluctuations to baryonic feedback processes that are stronger than expected
from recent cosmological simulations. Our proposed explanation can be tested
using measurements of the amplitude of the matter fluctuation spectrum on
linear scales, in particular via high precision redshift space distortion
measurements from forthcoming galaxy and quasar redshift surveys. | The physics and the structure of the quasar-driven outflow in Mrk 231: Massive AGN-driven outflows are invoked by AGN-galaxy co-evolutionary models
to suppress both star formation and black hole accretion. Massive molecular
outflows have recently been revealed in some AGN hosts. However, the physical
properties and structure of these AGN-driven molecular outflows are still
poorly constrained. Here we present new IRAM PdBI observations of Mrk231, the
closest quasar known, targeting both the CO(1-0) and CO(2-1) transitions. We
detect broad wings in both transitions, tracing a massive molecular outflow
with velocities up to 800 km/s. The wings are spatially resolved at high
significance level (5-11 sigma), indicating that the molecular outflow extends
on the kpc scale. The CO(2-1)/CO(1-0) ratio of the red broad wings is
consistent with the ratio observed in the narrow core, while the blue broad
wing is less excited than the core. The latter result suggests that quasar
driven outflow models invoking shocks (which would predict higher gas
excitation) are not appropriate to describe the bulk of the outflow in Mrk231.
However, we note that within the central 700 pc the CO(2-1)/CO(1-0) ratio of
the red wing is slightly, but significantly, higher than in the line core,
suggesting that shocks may play a role in the central region. We also find that
the average size of the outflow anticorrelates with the critical density of the
transition used as a wind tracer. This indicates that, although diffuse and
dense clumps coexist in the outflowing gas, dense outflowing clouds have
shorter lifetime and that they evaporate into the diffuse component along the
outflow or, more simply, that diffuse clouds are more efficiently accelerated
to larger distances by radiation pressure. |
Halo model and halo properties in Galileon gravity cosmologies: We investigate the performance of semi-analytical modelling of large-scale
structure in Galileon gravity cosmologies using results from N-body
simulations. We focus on the Cubic and Quartic Galileon models that provide a
reasonable fit to CMB, SNIa and BAO data. We demonstrate that the Sheth-Tormen
mass function and linear halo bias can be calibrated to provide a very good fit
to our simulation results. We also find that the halo concentration-mass
relation is well fitted by a power law. The nonlinear matter power spectrum
computed in the halo model approach is found to be inaccurate in the mildly
nonlinear regime, but captures reasonably well the effects of the Vainshtein
screening mechanism on small scales. In the Cubic model, the screening
mechanism hides essentially all of the effects of the fifth force inside
haloes. In the case of the Quartic model, the screening mechanism leaves behind
residual modifications to gravity, which make the effective gravitational
strength time-varying and smaller than the standard value. Compared to normal
gravity, this causes a deficiency of massive haloes and leads to a weaker
matter clustering on small scales. For both models, we show that there are
realistic halo occupation distributions of Luminous Red Galaxies that can match
both the observed large-scale clustering amplitude and the number density of
these galaxies. | Bayesian Comparison of the Cosmic Duality Scenarios: The cosmic distance duality relation (CDDR), $D_{\rm L}(1+z)^{-2}/D_{\rm
A}=\eta=1$, with $D_{\rm L}$ and $D_{\rm A}$, being the luminosity and angular
diameter distances, respectively, is a crucial premise in cosmological
scenarios. Many investigations try to test CDDR through observational
approaches, even some of these ones also consider a deformed CDDR, i.e.,
$\eta=\eta(z)$. In this paper, we use type Ia supernovae luminosity distances
and galaxy cluster measurements (their angular diameter distances and gas mass
fractions) in order to perform a Bayesian model comparison between $ \eta(z) $
functions. We show that the data here used are unable to pinpoint, with a high
degree of Bayesian evidence, which $\eta(z)$ function best captures the
evolution of CDDR. |
Impact of astrophysics on cosmology forecasts for 21 cm surveys: We use the results of previous work building a halo model formalism for the
distribution of neutral hydrogen, along with experimental parameters of future
radio facilities, to place forecasts on astrophysical and cosmological
parameters from next generation surveys. We consider 21 cm intensity mapping
surveys conducted using the BINGO, CHIME, FAST, TianLai, MeerKAT and SKA
experimental configurations. We work with the 5-parameter cosmological dataset
of {$\Omega_m, \sigma_8, h, n_s, \Omega_b$} assuming a flat $\Lambda$CDM model,
and the astrophysical parameters {$v_{c,0}, \beta$} which represent the cutoff
and slope of the HI- halo mass relation. We explore (i) quantifying the effects
of the astrophysics on the recovery of the cosmological parameters, (ii) the
dependence of the cosmological forecasts on the details of the astrophysical
parametrization, and (iii) the improvement of the constraints on probing
smaller scales in the HI power spectrum. For an SKA I MID intensity mapping
survey alone, probing scales up to $\ell_{\rm max} = 1000$, we find a factor of
$1.1 - 1.3$ broadening in the constraints on $\Omega_b$ and $\Omega_m$, and of
$2.4 - 2.6$ on $h$, $n_s$ and $\sigma_8$, if we marginalize over astrophysical
parameters without any priors. However, even the prior information coming from
the present knowledge of the astrophysics largely alleviates this broadening.
These findings do not change significantly on considering an extended HIHM
relation, illustrating the robustness of the results to the choice of the
astrophysical parametrization. Probing scales up to $\ell_{\rm max} = 2000$
improves the constraints by factors of 1.5-1.8. The forecasts improve on
increasing the number of tomographic redshift bins, saturating, in many cases,
with 4 - 5 redshift bins. We also forecast constraints for intensity mapping
with other experiments, and draw similar conclusions. | X-ray spectral study of the hot gas in three Clusters of Galaxies: We study the physical properties of three clusters of galaxies, selected from
a BeppoSAX Wide Field Camera (WFC) survey. These sources are identified as 1RXS
J153934.7-833535, 1RXS J160147.6-754507, and 1RXS J081232.3-571423 in the ROSAT
All-Sky Survey catalogue. We obtained XMM-Newton follow-up observations for
these three clusters. We fit single and multi-temperature models to spectra
obtained from the EPIC-pn camera to determine the temperature, the chemical
composition of the gas and their radial distribution. Since two observations
are contaminated by a high soft-proton background, we develop a new method to
estimate the effect of this background on the data. For the first time, we
present the temperature and iron abundance of two of these three clusters. The
iron abundance of 1RXS J153934.7-33535 decreases with radius. The fits to the
XMM-Newton and Chandra data show that the radial temperature profile within 3'
towards the centre either flattens or lowers. A Chandra image of the source
suggests the presence of X-ray cavities. The gas properties in 1RXS
J160147.6-754507 are consistent with a flat radial distribution of iron and
temperature within 2' from the centre. 1RXS J081232.3-571423 is a relatively
cool cluster with a temperature of about 3 keV. The radial temperature and iron
profiles suggest that 1RXS J153934.7-833535 is a cool core cluster. The Chandra
image shows substructure which points toward AGN feedback in the core. The flat
radial profiles of the temperature and iron abundance in 1RXS J160147.6-754507
are similar to the profiles of non-cool-core clusters. |
A bubble size distribution model for the Epoch of Reionization: The bubble size distribution is a summary statistics that can be computed
from the observed 21-cm signal from the Epoch of Reionization. As it depends
only on the ionization field and is not limited to gaussian information, it is
an interesting probe, complementary to the power spectrum of the full 21-cm
signal. Devising a flexible and reliable theoretical model for the bubble size
distribution paves the way for using it for astrophysical parameters inference.
The proposed model is built from the excursion set theory and a functional
relation between the bubble volume and the collapsed mass in the bubble. Unlike
previous models it accommodates any functional relation or distributions. Using
parameterized relations allows us to test the predictive power of the model by
performing a minimization best-fit to the bubble size distribution obtained
from a high resolution, fully coupled radiative hydrodynamics simulations,
HIRRAH-21. Our model is able to provide a better fit to the numerical bubble
size distribution at ionization fraction of $x_{\text{H}_{\text{II}}} \sim 1\%$
and $3\%$ than other existing models. Moreover, the bubble volume to collapsed
mass relation corresponding to the best-fit parameters, which is not an
observable, is compared to numerical simulation data. A good match is obtained,
confirming the possibility to infer this relation from an observed bubble size
distribution using our model. Finally we present a simple algorithm that
empirically implements the process of percolation. We show that it extends the
usability of our bubble size distribution model up to $x_{\text{H}_{\text{II}}}
\sim 30\%$. | The UV-bright, Slowly Declining Transient PS1-11af as a Partial Tidal
Disruption Event: We present the Pan-STARRS1 discovery of the long-lived and blue transient
PS1-11af, which was also detected by GALEX with coordinated observations in the
near-ultraviolet (NUV) band. PS1-11af is associated with the nucleus of an
early-type galaxy at redshift z=0.4046 that exhibits no evidence for star
formation or AGN activity. Four epochs of spectroscopy reveal a pair of
transient broad absorption features in the UV on otherwise featureless spectra.
Despite the superficial similarity of these features to P-Cygni absorptions of
supernovae (SNe), we conclude that PS1-11af is not consistent with the
properties of known types of SNe. Blackbody fits to the spectral energy
distribution are inconsistent with the cooling, expanding ejecta of a SN, and
the velocities of the absorption features are too high to represent material in
homologous expansion near a SN photosphere. However, the constant blue colors
and slow evolution of the luminosity are similar to previous optically-selected
tidal disruption events (TDEs). The shape of the optical light curve is
consistent with models for TDEs, but the minimum accreted mass necessary to
power the observed luminosity is only ~0.002M_sun, which points to a partial
disruption model. A full disruption model predicts higher bolometric
luminosities, which would require most of the radiation to be emitted in a
separate component at high energies where we lack observations. In addition,
the observed temperature is lower than that predicted by pure accretion disk
models for TDEs and requires reprocessing to a constant, lower temperature.
Three deep non-detections in the radio with the VLA over the first two years
after the event set strict limits on the production of any relativistic outflow
comparable to Swift J1644+57, even if off-axis. |
The BAHAMAS project: Calibrated hydrodynamical simulations for
large-scale structure cosmology: The evolution of the large-scale distribution of matter is sensitive to a
variety of fundamental parameters that characterise the dark matter, dark
energy, and other aspects of our cosmological framework. Since the majority of
the mass density is in the form of dark matter that cannot be directly
observed, to do cosmology with large-scale structure one must use observable
(baryonic) quantities that trace the underlying matter distribution in a
(hopefully) predictable way. However, recent numerical studies have
demonstrated that the mapping between observable and total mass, as well as the
total mass itself, are sensitive to unresolved feedback processes associated
with galaxy formation, motivating explicit calibration of the feedback
efficiencies. Here we construct a new suite of large-volume cosmological
hydrodynamical simulations (called BAHAMAS, for BAryons and HAloes of MAssive
Systems) where subgrid models of stellar and Active Galactic Nucleus (AGN)
feedback have been calibrated to reproduce the present-day galaxy stellar mass
function and the hot gas mass fractions of groups and clusters in order to
ensure the effects of feedback on the overall matter distribution are broadly
correct. We show that the calibrated simulations reproduce an unprecedentedly
wide range of properties of massive systems, including the various observed
mappings between galaxies, hot gas, total mass, and black holes, and represent
a significant advance in our ability to mitigate the primary systematic
uncertainty in most present large-scale structure tests. | The Cosmological Parameters 2014: This is a review article for The Review of Particle Physics 2014 (aka the
Particle Data Book). It forms a compact review of knowledge of the cosmological
parameters at the beginning of 2014. Topics included are Parametrizing the
Universe; Extensions to the standard model; Probes; Bringing observations
together; Outlook for the future. |
Accurate Power Spectrum Estimation toward Nyquist limit: The power spectrum, as a statistic in Fourier space, is commonly numerically
calculated using the fast Fourier transform method to efficiently reduce the
computational costs. To alleviate the systematic bias known as aliasing due to
the insufficient sampling, the interlacing technique was proposed. We derive
the analytical form of the shot noise under the interlacing technique, which
enables the exact separation of the Poisson shot noise from the signal in this
case. Thanks to the accurate shot noise subtraction, we demonstrate an
enhancement in the accuracy of power spectrum estimation, and compare with the
other widely used estimators in community. The good performance of our
estimation allows an abatement in the computational cost by using low
resolution and low order mass assignment scheme in the analysis for huge
surveys and mocks. | Baryonic Post-Processing of N-body Simulations, with Application to Fast
Radio Bursts: Where the cosmic baryons lie in and around galactic dark matter halos is only
weakly constrained. We develop a method to quickly paint on models for their
distribution. Our approach uses the statistical advantages of $N$-body
simulations, while painting on the profile of gas around individual halos in
ways that can be motivated by semi-analytic models or zoom-in hydrodynamic
simulations of galaxies. Possible applications of the algorithm include
extragalactic dispersion measures to fast radio bursts (FRBs), the
Sunyaev-Zeldovich effect, baryonic effects on weak lensing, and cosmic metal
enrichment. As an initial application, we use this tool to investigate how the
baryonic profile of foreground galactic-mass halos affects the statistics of
the dispersion measure (DM) towards cosmological FRBs.
We show that the distribution of DM is sensitive to the distribution of
baryons in galactic halos, with viable gas profile models having significantly
different probability distributions for DM to a given redshift. We also
investigate the requirements to statistically measure the circumgalactic
electron profile for FRB analyses that stack DM with impact parameter to
foreground galaxies, quantifying the size of the contaminating "two-halo" term
from correlated systems and the number of FRBs for a high significance
detection. Publicly available Python modules implement our CGMBrush algorithm. |
Limits on Einstein's Equivalence Principle from the first localized Fast
Radio Burst FRB 150418: Fast Radio Bursts have recently been used to place limits on Einstein's
Equivalence Principle via observations of time delays between photons of
different radio frequencies by \citet{wei15}. These limits on differential
post-Newtonian parameters ($\Delta \gamma<2.52\times10^{-8}$) are the best yet
achieved but still rely on uncertain assumptions, namely the relative
contributions of dispersion and gravitational delays to the observed time
delays and the distances to FRBs. Also very recently, the first FRB host galaxy
has likely been identified, providing the first redshift-based distance
estimate to FRB 150418 \citep{kea16}. Moreover, consistency between the
\omegaigm\ estimate from FRB 150418 and \omegaigm~expected from $\Lambda$CDM
models and WMAP observations leads one to conclude that the observed time delay
for FRB 150418 is highly dominated by dispersion, with any gravitational delays
small contributors. This points to even tighter limits on $\Delta \gamma$. In
this paper, the technique of \citet{wei15} is applied to FRB 150418 to produce
a limit of $\Delta \gamma < 1 - 2\times10^{-9}$, approximately an order of
magnitude better than previous limits and in line with expectations by
\citet{wei15} for what could be achieved if the dispersive delay is separated
from other effects. Future substantial improvements in such limits will depend
on accurately determining the contribution of individual ionized components to
the total observed time delays for FRBs. | First Axion Results from the XENON100 Experiment: We present the first results of searches for axions and axion-like-particles
with the XENON100 experiment. The axion-electron coupling constant, $g_{Ae}$,
has been probed by exploiting the axio-electric effect in liquid xenon. A
profile likelihood analysis of 224.6 live days $\times$ 34 kg exposure has
shown no evidence for a signal. By rejecting $g_{Ae}$, larger than $7.7 \times
10^{-12}$ (90\% CL) in the solar axion search, we set the best limit to date on
this coupling. In the frame of the DFSZ and KSVZ models, we exclude QCD axions
heavier than 0.3 eV/c$^2$ and 80 eV/c$^2$, respectively. For
axion-like-particles, under the assumption that they constitute the whole
abundance of dark matter in our galaxy, we constrain $g_{Ae}$, to be lower than
$1 \times 10^{-12}$ (90\% CL) for mass range from 1 to 40 keV/c$^2$, and set
the best limit to date as well. |
The Stellar Kinematic Signature of Massive Black Hole Binaries: The stalling radius of a merging massive binary black hole (BBH) is expected
to be below 0".1 even in nearby galaxies (Yu 2002), and thus BBHs are not
expected to be spatially resolved in the near future. However, as we show
below, a BBH may be detectable through the significantly anisotropic stellar
velocity distribution it produces on scales 5-10 times larger than the binary
separation. We calculate the velocity distribution of stable orbits near a BBH
by solving the restricted three body problem for a BBH embedded in a bulge
potential. We present high resolution maps of the projected velocity
distribution moments, based on snapshots of ~ 10^8 stable orbits. The kinematic
signature of a BBH in the average velocity maps is a counter rotating torus of
stars outside the BBH Hill spheres. The velocity dispersion maps reveal a dip
in the inner region, and an excess of 20-40% further out, compared to a single
BH of the same total mass. More pronounced signatures are seen in the third and
fourth Gauss-Hermite velocity moments maps. The detection of these signatures
may indicate the presence of a BBH currently, or at some earlier time, which
depends on the rate of velocity phase space mixing following the BBH merger. | Primordial perturbations and non-Gaussianities from modulated trapping: We propose a new mechanism to generate primordial curvature perturbations,
based on the resonant production of particles during inflation. It is known
that this phenomenon can trap the inflaton for a fraction of e-fold. This
effect is governed by the mass of the produced particles and by their coupling
to the inflaton, parameters which can depend on the expectation value of other
fields. If one of such additional fields - a 'modulaton' - is light, then its
fluctuations, acquired during the earlier stages of inflation, will induce a
spatial modulation of the trapping, and thus of the end of inflation,
corresponding to a curvature perturbation. We calculate the power spectrum,
bispectrum and trispectrum of the curvature perturbations generated by this
mechanism, taking into account the perturbations due to the inflaton
fluctuations as well. We find that modulated trapping could provide the main
contribution to the observed power spectrum and lead to detectable primordial
non-gaussianities. |
Revealing the effects of curvature on the cosmological models: In this paper we consider the effects of adding curvature in extended
cosmologies involving a free-to-vary neutrino sector and different
parametrizations of Dark Energy (DE). We make use of the Planck 2018 cosmic
microwave background temperature and polarization data, Baryon Acoustic
Oscillations and Pantheon type Ia Supernovae data. Our main result is that a
non-flat Universe cannot be discarded in light of the current astronomical
data, because we find an indication for a closed Universe in most of the DE
cosmologies explored in this work. On the other hand, forcing the Universe to
be flat can significantly bias the constraints on the equation of state of the
DE component and its dynamical nature. | A Systematic Study of the Stochastic Gravitational-Wave Background due
to Stellar Core Collapse: Stellar core collapse events are expected to produce gravitational waves via
several mechanisms, most of which are not yet fully understood due to the
current limitations in the numerical simulations of these events. In this
paper, we begin with an empirical functional form that fits the
gravitational-wave spectra from existing simulations of stellar core collapse
and integrate over all collapse events in the universe to estimate the
resulting stochastic gravitational-wave background. We then use a Gaussian
functional form to separately fit and model a low-frequency peak in the
core-collapse strain spectra, which likely occurs due to prompt convection. We
systematically study the parameter space of both models, as well as the
combined case, and investigate their detectability by upcoming
gravitational-wave detectors, such as Advanced LIGO and Einstein Telescope.
Assuming realistic formation rates for progenitors of core-collapse supernovae,
our results indicate that both models are 2--4 orders of magnitude below the
expected sensitivity of Advanced LIGO, and 1--2 orders of magnitude below that
of the Einstein Telescope. |
Identifying Luminous AGN in Deep Surveys: Revised IRAC Selection
Criteria: Spitzer IRAC selection is a powerful tool for identifying luminous AGN. For
deep IRAC data, however, the AGN selection wedges currently in use are heavily
contaminated by star-forming galaxies, especially at high redshift. Using the
large samples of luminous AGN and high-redshift star-forming galaxies in
COSMOS, we redefine the AGN selection criteria for use in deep IRAC surveys.
The new IRAC criteria are designed to be both highly complete and reliable, and
incorporate the best aspects of the current AGN selection wedges and of
infrared power-law selection while excluding high redshift star-forming
galaxies selected via the BzK, DRG, LBG, and SMG criteria. At QSO-luminosities
of log L(2-10 keV) (ergs/s) > 44, the new IRAC criteria recover 75% of the hard
X-ray and IRAC-detected XMM-COSMOS sample, yet only 38% of the IRAC AGN
candidates have X-ray counterparts, a fraction that rises to 52% in regions
with Chandra exposures of 50-160 ks. X-ray stacking of the individually X-ray
non-detected AGN candidates leads to a hard X-ray signal indicative of heavily
obscured to mildly Compton-thick obscuration (log N_H (cm^-2) = 23.5 +/- 0.4).
While IRAC selection recovers a substantial fraction of luminous unobscured and
obscured AGN, it is incomplete to low-luminosity and host-dominated AGN. | The Cosmic Far-Infrared Background Buildup Since Redshift 2 at 70 and
160 microns in the COSMOS and GOODS fields: The Cosmic Far-Infrared Background (CIB) at wavelengths around 160 {\mu}m
corresponds to the peak intensity of the whole Extragalactic Background Light,
which is being measured with increasing accuracy. However, the build up of the
CIB emission as a function of redshift, is still not well known. Our goal is to
measure the CIB history at 70 {\mu}m and 160 {\mu}m at different redshifts, and
provide constraints for infrared galaxy evolution models. We use complete deep
Spitzer 24 {\mu}m catalogs down to about 80 {\mu}Jy, with spectroscopic and
photometric redshifts identifications, from the GOODS and COSMOS deep infrared
surveys covering 2 square degrees total. After cleaning the Spitzer/MIPS 70
{\mu}m and 160 {\mu}m maps from detected sources, we stacked the far-IR images
at the positions of the 24 {\mu}m sources in different redshift bins. We
measured the contribution of each stacked source to the total 70 and 160 {\mu}m
light, and compare with model predictions and recent far-IR measurements made
with Herschel/PACS on smaller fields. We have detected components of the 70 and
160 {\mu}m backgrounds in different redshift bins up to z ~ 2. The contribution
to the CIB is maximum at 0.3 <= z <= 0.9 at 160{\mu}m (and z <= 0.5 at 70
{\mu}m). A total of 81% (74%) of the 70 (160) {\mu}m background was emitted at
z < 1. We estimate that the AGN relative contribution to the far-IR CIB is less
than about 10% at z < 1.5. We provide a comprehensive view of the CIB buildup
at 24, 70, 100, 160 {\mu}m. IR galaxy models predicting a major contribution to
the CIB at z < 1 are in agreement with our measurements, while our results
discard other models that predict a peak of the background at higher redshifts.
Our results are available online http://www.ias.u-psud.fr/irgalaxies/ . |
Distance Duality Test: The Evolution of Radio Sources Mimics a
Nonexpanding Universe: Distance duality relation (DDR) marks a fundamental difference between
expanding and nonexpanding Universes, as an expanding metric causes angular
diameter distance smaller than luminosity distance by an extra factor of
$(1+z)$. Here we report a test of this relation using two independent samples
of ultracompact radio sources observed at 2.29 GHz and 5.0 GHz. The test with
radio sources involves only geometry, so it is independent of cosmological
models. Since the observed radio luminosities systematically increase with
redshift, we do not assume a constant source size. Instead, we start with
assuming the intensive property, luminosity density, does not evolve with
redshift and then infer its evolution from the resultant DDR. We make the same
assumption for both samples, and find it results in the same angular
size-redshift relation. Interestingly, the resultant DDR is fully consistent
with a nonexpanding Universe. Imposing the DDR predicted by the expanding
Universe, we infer the radio luminosity density evolves as
$\rho_L\propto(1+z)^3$. However, the perfect agreement with a nonexpanding
Universe under the assumption of constant luminosity densities poses a
conspiracy and fine-tuning problem: the size and luminosity density of
ultracompact radio sources evolve in the way that precisely mimics a
nonexpanding Universe. | Reconstructing the spectral shape of a stochastic gravitational wave
background with LISA: We present a set of tools to assess the capabilities of LISA to detect and
reconstruct the spectral shape and amplitude of a stochastic gravitational wave
background (SGWB). We first provide the LISA power-law sensitivity curve and
binned power-law sensitivity curves, based on the latest updates on the LISA
design. These curves are useful to make a qualitative assessment of the
detection and reconstruction prospects of a SGWB. For a quantitative
reconstruction of a SGWB with arbitrary power spectrum shape, we propose a
novel data analysis technique: by means of an automatized adaptive procedure,
we conveniently split the LISA sensitivity band into frequency bins, and fit
the data inside each bin with a power law signal plus a model of the
instrumental noise. We apply the procedure to SGWB signals with a variety of
representative frequency profiles, and prove that LISA can reconstruct their
spectral shape. Our procedure, implemented in the code SGWBinner, is suitable
for homogeneous and isotropic SGWBs detectable at LISA, and it is also expected
to work for other gravitational wave observatories. |
The First Galaxies: Chemical Enrichment, Mixing, and Star Formation: Using three-dimensional cosmological simulations, we study the assembly
process of one of the first galaxies, with a total mass of 10^8 M_sun,
collapsing at z = 10. Our main goal is to trace the transport of the heavy
chemical elements produced and dispersed by a pair-instability supernova
exploding in one of the minihalo progenitors. To this extent, we incorporate an
efficient algorithm into our smoothed particle hydrodynamics code which
approximately models turbulent mixing as a diffusion process. We study this
mixing with and without the radiative feedback from Population III stars that
subsequently form in neighboring minihalos. Our simulations allow us to
constrain the initial conditions for second-generation star formation, within
the first galaxy itself, and inside of minihalos that virialize after the
supernova explosion. We find that most minihalos remain unscathed by ionizing
radiation or the supernova remnant, while some are substantially photoheated
and enriched to supercritical levels, likely resulting in the formation of
low-mass Population III or even Population II stars. At the center of the newly
formed galaxy, 10^5 M_sun of cold, dense gas uniformly enriched to 10^-3 Z_sun
are in a state of collapse, suggesting that a cluster of Population II stars
will form. The first galaxies, as may be detected by the James Webb Space
Telescope, would therefore already contain stellar populations familiar from
lower redshifts. | Velocity-dependent Self-interacting Dark Matter from Groups and Clusters
of Galaxies: We probe the self-interactions of dark matter using observational data of
relaxed galaxy groups and clusters. Our analysis uses the Jeans formalism and
considers a wider range of systematic effects than in previous work, including
adiabatic contraction and stellar anisotropy, to robustly constrain the
self-interaction cross section. For both groups and clusters, our results show
a mild preference for a nonzero cross section compared with cold collisionless
dark matter. Our groups result, $\sigma/m=0.5\pm0.2~\mathrm{cm}^2/\mathrm{g}$,
places the first constraint on self-interacting dark matter (SIDM) at an
intermediate scale between galaxies and massive clusters. Our clusters result
is $\sigma/m=0.19\pm0.09~\mathrm{cm}^2/\mathrm{g}$, with an upper limit of
$\sigma / m < 0.35~\mathrm{cm}^2/\mathrm{g}$ (95% CL). Thus, our results
disfavor a velocity-independent cross section of order
$1~\mathrm{cm}^2/\mathrm{g}$ or larger needed to address small scale structure
problems in galaxies, but are consistent with a velocity-dependent cross
section that decreases with increasing scattering velocity. Comparing the cross
sections with and without the effect of adiabatic contraction, we find that
adiabatic contraction produces slightly larger values for our data sample, but
they are consistent at the $1\sigma$ level. Finally, to validate our approach,
we apply our Jeans analysis to a sample of mock data generated from
SIDM-plus-baryons simulations with $\sigma/m = 1~\mathrm{cm}^2/\mathrm{g}$.
This is the first test of the Jeans model at the level of stellar and lensing
observables directly measured from simulations. We find our analysis gives a
robust determination of the cross section, as well as consistently inferring
the true baryon and dark matter density profiles. |
Unusual displacement of HI due to tidal interaction in Arp 181: We present results from GMRT HI 21 cm line observations of the interacting
galaxy pair Arp 181 (NGC 3212 and NGC 3215) at z =0.032. We find almost all of
the detected HI (90%) displaced well beyond the optical disks of the pair with
the highest density HI located ~70 kpc west of the pair. An HI bridge extending
between the optical pair and the bulk of the HI together with their HI
deficiencies provide strong evidence that the interaction between the pair has
removed most of their HI to the current projected position. HI to the west of
the pair has two approximately equal intensity peaks. The HI intensity maximum
furthest to the west coincides with a small spiral companion SDSS
J102726.32+794911.9 which shows enhanced mid-infrared (Spitzer), UV (GALEX) and
H alpha emission indicating intense star forming activity. The HI intensity
maximum close to the Arp 181 pair, coincides with a diffuse optical cloud
detected in UV (GALEX) at the end of the stellar and HI tidal tails originating
at NGC 3212 and, previously proposed to be a tidal dwarf galaxy in formation.
Future sensitive HI surveys by telescopes like ASKAP should prove to be
powerful tools for identifying tidal dwarfs at moderate to large redshifts to
explore in detail the evolution of dwarf galaxies in the Universe. | Shocks in the Stacked Sunyaev-Zel'dovich Profiles of Clusters I:
Analysis with the Three Hundred Simulations: Gas infalling into the gravitational potential wells of massive galaxy
clusters is expected to experience one or more shocks on its journey to
becoming part of the intracluster medium (ICM). These shocks are important for
setting the thermodynamic properties of the ICM and can therefore impact
cluster observables such as X-ray emission and the Sunyaev-Zel'dovich (SZ)
effect. We investigate the possibility of detecting signals from cluster shocks
in the averaged thermal SZ profiles of galaxy clusters. Using zoom-in
hydrodynamic simulations of massive clusters from the Three Hundred Project, we
show that if cluster SZ profiles are stacked as a function of $R/R_{200m}$,
shock-induced features appear in the averaged SZ profile. These features are
not accounted for in standard fitting formulae for the SZ profiles of galaxy
clusters. We show that the shock features should be detectable with samples of
clusters from ongoing and future SZ surveys. We also demonstrate that the
location of these features is correlated with the cluster accretion rate, as
well as the location of the cluster splashback radius. Analyses of ongoing and
future surveys, such as SPT-3G, AdvACT, Simons Observatory and CMB-S4, that
include gas shocks will gain a new handle on the properties and dynamics of the
outskirts of massive halos, both in gas and in mass. |
NGC 839: Shocks in an M82-like Superwind: We present observations of NGC 839 made with the Wide Field Spectrograph
(WiFeS) on the ANU 2.3m telescope. Our data cover a region 25" x 60" at a
spatial resolution of ~1.5". The long axis of the field is aligned with the
superwind we have discovered in this starburst galaxy. The data cover the range
of 3700-7000 {\AA}, with a spectral resolution R~7000 in the red, and R~3000 in
the blue. We find that the stellar component of the galaxy is strongly
dominated by a fast rotating intermediate-age (~400 Myr) A-Type stellar
population, while the gas is concentrated in a bi-conical polar funnel. We have
generated flux distributions, emission line ratio diagnostics and velocity maps
in both emission and absorption components. We interpret these in the context
of a new grid of low-velocity shock models appropriate for galactic-scale
outflows. These models are remarkably well fit to the data, providing for the
first time model diagnostics for shocks in superwinds and strongly suggesting
that shock excitation is largely responsible for the extended LINER emission in
the outflowing gas in NGC 839. Our work may have important implications both
for extended LINER emission seen in other galaxies, as well as in the
interpretation of objects with "composite" spectra. Finally, we present a
scenario for the formation of E+A galaxies based upon our observations of NGC
839, and its relation to M82. | Did the Milky Way dwarf satellites enter the halo as a group?: The dwarf satellite galaxies in the Local Group are generally considered to
be hosted in dark matter subhalos that survived the disruptive processes during
infall onto their host halos. It has recently been argued that if the majority
of satellites entered the Milky Way halo in a group rather than individually,
this could explain the spatial and dynamical peculiarities of its satellite
distribution. Such groups were identified as dwarf galaxy associations that are
found in the nearby Universe. In this paper we address the question whether
galaxies in such associations can be the progenitors of the Milky Way satellite
galaxies. We find that the dwarf associations are much more extended than would
be required to explain the disk-like distribution of the Milky Way and
Andromeda satellite galaxies. We further identify a possible minor filamentary
structure, perpendicular to the supergalactic plane, in which the dwarf
associations are located, that might be related to the direction of infall of a
progenitor galaxy of the Milky Way satellites, if they are of tidal origin. |
Dwarf Galaxies United by Dark Bosons: Low mass galaxies in the Local Group are dominated by dark matter and
comprise the well studied ``dwarf Spheroidal" (dSph) class, with typical masses
of $10^{9-10}M_\odot$ and also the equally numerous ``ultra faint dwarfs"
(UFD), discovered recently, that are distinctly smaller and denser with masses
of only $10^{7-8}M_\odot$. This bimodality amongst low mass galaxies contrasts
with the scale free continuity expected for galaxies formed under gravity, as
in the standard Cold Dark Matter (CDM) model for heavy particles. Within each
dwarf class we find the core radius $R_c$ is inversely related to velocity
dispersion $\sigma$, quite the opposite of standard expectations, but
indicative of dark matter in a Bose-Einstein state, where the Uncertainty
Principle requires $R_c \times \sigma$ is fixed by Planks constant, $h$. The
corresponding boson mass, $m_b=h/R_c \sigma$, differs by one order of magnitude
between the UDF and dSph classes, with $10^{-21.4}$eV and $10^{-20.3}$eV
respectively. Two boson species is reinforced by parallel relations seen
between the central density and radius of UDF and dSph dwarfs respectively,
each matching the steep prediction, $\rho_c \propto R_c^{-4}$, for soliton
cores in the ground state. Furthermore, soliton cores accurately fit the
stellar profiles of UDF and dSph dwarfs where prominent, dense cores appear
surrounded by low density halos, as predicted by our simulations. Multiple
bosons may point to a String Theory interpretation for dark matter, where a
discrete mass spectrum of axions is generically predicted to span many decades
in mass, offering a unifying "Axiverse" interpretation for the observed
"diversity" of dark matter dominated dwarf galaxies. | On cosmological signatures of baryons-dark energy elastic couplings: We consider a scenario where dark energy and baryons are dynamically coupled
without any energy transfer. In this scenario, the background cosmology is
unaffected and, at the perturbations level, the coupling only appears through
the corresponding Euler equations of dark energy and baryons. We then explore
some phenomenological consequences of this scenario and their signatures in
several cosmological observables. In particular, we show its ability to
suppress the growth of cosmic structures. We also constrain the parameters of
the model with cosmological data and show that an interaction of dark energy
with baryons on cosmological scales is mildly favoured. |
Dark Matter Results From 54-Ton-Day Exposure of PandaX-II Experiment: We report a new search of weakly interacting massive particles (WIMPs) using
the combined low background data sets in 2016 and 2017 from the PandaX-II
experiment in China. The latest data set contains a new exposure of 77.1 live
day, with the background reduced to a level of 0.8$\times10^{-3}$ evt/kg/day,
improved by a factor of 2.5 in comparison to the previous run in 2016. No
excess events were found above the expected background. With a total exposure
of 5.4$\times10^4$ kg day, the most stringent upper limit on spin-independent
WIMP-nucleon cross section was set for a WIMP with mass larger than 100
GeV/c$^2$, with the lowest exclusion at 8.6$\times10^{-47}$ cm$^2$ at 40
GeV/c$^2$. | Planck 2015 results. IX. Diffuse component separation: CMB maps: We present foreground-reduced CMB maps derived from the full Planck data set
in both temperature and polarization. Compared to the corresponding Planck 2013
temperature sky maps, the total data volume is larger by a factor of 3.2 for
frequencies between 30 and 70 GHz, and by 1.9 for frequencies between 100 and
857 GHz. In addition, systematic errors in the forms of
temperature-to-polarization leakage, analogue-to-digital conversion
uncertainties, and very long time constant errors have been dramatically
reduced, to the extent that the cosmological polarization signal may now be
robustly recovered on angular scales $\ell\gtrsim40$. On the very largest
scales, instrumental systematic residuals are still non-negligible compared to
the expected cosmological signal, and modes with $\ell < 20$ are accordingly
suppressed in the current polarization maps by high-pass filtering. As in 2013,
four different CMB component separation algorithms are applied to these
observations, providing a measure of stability with respect to algorithmic and
modelling choices. The resulting polarization maps have rms instrumental noise
ranging between 0.21 and 0.27$\,\mu\textrm{K}$ averaged over 55 arcmin pixels,
and between 4.5 and 6.1$\,\mu\textrm{K}$ averaged over 3.4 arcmin pixels. The
cosmological parameters derived from the analysis of temperature power spectra
are in agreement at the $1\sigma$ level with the Planck 2015 likelihood.
Unresolved mismatches between the noise properties of the data and simulations
prevent a satisfactory description of the higher-order statistical properties
of the polarization maps. Thus, the primary applications of these polarization
maps are those that do not require massive simulations for accurate estimation
of uncertainties, for instance estimation of cross-spectra and
cross-correlations, or stacking analyses. |
Which galaxies dominate the neutral gas content of the Universe?: We study the contribution of galaxies with different properties to the global
densities of star formation rate (SFR), atomic (HI) and molecular hydrogen (H2)
as a function of redshift. We use the GALFORM model of galaxy formation, which
is set in the LCDM framework. This model includes a self-consistent calculation
of the SFR, which depends on the H2 content of galaxies. The predicted SFR
density and how much of this is contributed by galaxies with different stellar
masses and infrared luminosities are in agreement with observations. The model
predicts a modest evolution of the HI density at z<3, which is also in
agreement with the observations. The HI density is predicted to be always
dominated by galaxies with SFR<1Msun/yr. This contrasts with the H2 density,
which is predicted to be dominated by galaxies with SFR>10Msun/yr. Current
high-redshift galaxy surveys are limited to detect carbon monoxide in galaxies
with SFR>30Msun/yr, which in our model make up, at most, 20% of the H2 in the
universe. In terms of stellar mass, the predicted H2 density is dominated by
massive galaxies, Mstellar>10^10Msun, while the HI density is dominated by low
mass galaxies, Mstellar<10^9Msun. In the context of upcoming neutral gas
surveys, we suggest that the faint nature of the galaxies dominating the HI
content of the Universe will hamper the identification of optical counterparts,
while for H2, we expect follow up observations of molecular emission lines of
already existing galaxy catalogues to be able to uncover the H2 density of the
Universe. | Removal of Galactic foregrounds for the Simons Observatory primordial
gravitational wave search: Upcoming observations from the Simons Observatory have been projected to
constrain the tensor-to-scalar ratio, $r$, at the level of $\sigma(r)=$0.003.
Here we describe one of the forecasting algorithms for the Simons Observatory
in more detail, based on cleaning CMB polarization maps using a parametric
model. We present a new code to perform this end-to-end forecast, and explore
the assumptions in greater detail. If spatial uniformity of the spectral energy
distribution of synchrotron radiation and thermal dust emission is assumed over
the region planned for observations, covering almost a fifth of the sky, a bias
of order 1--3$\sigma$ in $r$ is projected for foreground models consistent with
current data. We find that by masking the most contaminated regions of sky, or
by adopting more parameters to describe the spatial variation in spectral index
for synchrotron and dust, such a bias can be mitigated for the foreground
models we consider. We also explore strategies for testing whether the cleaned
CMB polarization maps contain residual foreground contamination, including
cross-correlating with maps tracing the foregrounds. This method also has
applications for other CMB polarization experiments. |
A dark matter scaling relation from mirror dark matter: Mirror dark matter, and other similar dissipative dark matter candidates,
need an energy source to stabilize dark matter halos in spiral galaxies. It has
been suggested previously that ordinary supernovae can potentially supply the
required energy. By matching the energy supplied to the halo from supernovae to
that lost due to radiative cooling, we here derive a rough scaling relation,
$R_{SN} \propto \rho_0 r_0^2$ ($R_{SN}$ is the supernova rate and $\rho_0, \
r_0$ the dark matter central density and core radius). Such a relation is
consistent with dark matter properties inferred from studies of spiral galaxies
with halo masses larger than $3\times 10^{11} M_\odot$. We speculate that other
observed galaxy regularities might be explained within the framework of such
dissipative dark matter. | Joint analysis of anisotropic power spectrum, bispectrum and
trispectrum: application to N-body simulations: We perform for the first time a joint analysis of the monopole and
quadrupoles for power spectrum, bispectrum and integrated trispectrum
(i-trispectrum) from the redshift space matter field in N-body simulations.
With a full Markov Chain Monte Carlo exploration of the posterior distribution,
we quantify the constraints on cosmological parameters for an object density of
$n_\mathrm{p}=5\times10^{-4} (h\,\mathrm{Mpc}^{-1})^{3}$, redshift $z=0.5$, and
a covariance corresponding to a survey volume of $V_\mathrm{survey}
=25\,(h^{-1}\mathrm{Gpc})^3$, a set up which is representative of forthcoming
galaxy redshift surveys. We demonstrate the complementarity of the bispectrum
and i-trispectrum in constraining key cosmological parameters. In particular,
compared to the state-of-the-art power spectrum (monopole plus quadrupole) and
bispectrum (monopole) analyses, we find 1D $68\%$ credible regions smaller by a
factor of $(72\%,78\%,72\%,47\%,46\%)$ for the parameters
$(f,\sigma_8,f_\mathrm{nl},\alpha_\parallel,\alpha_\perp)$ respectively. This
work motivates the additional effort necessary to include the redshift-space
anisotropic signal of higher-order statistics in the analysis and
interpretation of ongoing and future galaxy surveys. |
Lensing in the McVittie metric: We investigate the effect of the cosmological expansion on the bending of
light due to an isolated point-like mass. We adopt McVittie metric as the model
for the geometry of the lens. Assuming a constant Hubble factor we find an
analytic expression involving the bending angle, which turns out to be
unaffected by the cosmological expansion at the leading order. | The Arecibo Legacy Fast ALFA Survey: The alpha.40 HI Source Catalog, its
Characteristics and their Impact on the Derivation of the HI Mass Function: We present a current catalog of 21 cm HI line sources extracted from the
Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey over ~2800
square degrees of sky: the alpha.40 catalog. Covering 40% of the final survey
area, the alpha.40 catalog contains 15855 sources in the regions 07h30m < R.A.
< 16h30m, +04 deg < Dec. < +16 deg and +24 deg < Dec. < +28 deg and 22h < R.A.
< 03h, +14 deg < Dec. < +16 deg and +24 deg < Dec. < +32 deg. Of those, 15041
are certainly extragalactic, yielding a source density of 5.3 galaxies per
square degree, a factor of 29 improvement over the catalog extracted from the
HI Parkes All Sky Survey. In addition to the source centroid positions, HI line
flux densities, recessional velocities and line widths, the catalog includes
the coordinates of the most probable optical counterpart of each HI line
detection, and a separate compilation provides a crossmatch to identifications
given in the photometric and spectroscopic catalogs associated with the Sloan
Digital Sky Survey Data Release 7. Fewer than 2% of the extragalactic HI line
sources cannot be identified with a feasible optical counterpart; some of those
may be rare OH megamasers at 0.16 < z < 0.25. A detailed analysis is presented
of the completeness, width dependent sensitivity function and bias inherent in
the current alpha.40 catalog. The impact of survey selection, distance errors,
current volume coverage and local large scale structure on the derivation of
the HI mass function is assessed. While alpha.40 does not yet provide a
completely representative sampling of cosmological volume, derivations of the
HI mass function using future data releases from ALFALFA will further improve
both statistical and systematic uncertainties. |
Diffuse Intracluster Light at Intermediate Redshifts: ICL observations
in a X-ray cluster at z=0.29: The diffuse intracluster light (ICL) contains a significant fraction of the
total stellar mass in clusters of galaxies, and contributes in roughly equal
proportion as the hot intra-cluster medium (ICM) to the total baryon content of
clusters. Because of the potential importance of understanding the origin of
the ICL in the context of the formation and evolution of structure in the
Universe, the field has recently undergone a revival both in the quality and
quantity of observational and theoretical investigations. Due to cosmological
dimming, the observational work has mostly concentrated on low redshift
clusters, but clearly observations at higher redshifts can provide interesting
clues about the evolution of the diffuse component. In this paper we present
the first results of a program to characterize the ICL of intermediate redshift
clusters. We find that at z ~ 0.3, the X-ray cluster RX J0054.0-2823 already
has a significant ICL and that the fraction of the total light in the ICL and
the brightest cluster galaxy (BCG) is comparable to that of similar clusters at
lower redshift. We also find that the kinematics of the ICL is consistent with
it being the remnant of tidally destroyed galaxies streaming in the central
regions of the cluster, which has three central giant elliptical galaxies
acting as an efficient "grinding machine". Our cluster has a bi-modal
radial-velocity distribution and thus two possible values for the velocity
dispersion. We find that the cluster fits well in the correlation between
BCG+ICL fraction and cluster mass for a range of velocity dispersions, leading
us to question the validity of a relevant correlation between these two
quantities. | Breaking the Dark Degeneracy with the Drifting Coefficient of the Field
Cluster Mass Function: We present a numerical analysis supporting the evidence that the redshift
evolution of the drifting coefficient of the field cluster mass function is
capable of breaking several cosmic degeneracies. This evidence is based on the
data from the CoDECS and DUSTGRAIN-pathfinder simulations performed separately
for various non-standard cosmologies including coupled dark energy, $f(R)$
gravity and combinations of $f(R)$ gravity with massive neutrinos as well as
for the standard $\Lambda$CDM cosmology. We first numerically determine the
field cluster mass functions at various redshifts in the range of $0\le z\le 1$
for each cosmology. Then, we compare the analytic formula developed in previous
works with the numerically obtained field cluster mass functions by adjusting
its drifting coefficient, $\beta$, at each redshift. It is found that the
analytic formula with the best-fit coefficient provides a good match to the
numerical results at all redshifts for all of the cosmologies. The empirically
determined redshift evolution of the drifting coefficient, $\beta(z)$, turns
out to significantly differ among different cosmologies. It is also shown that
even without using any prior information on the background cosmology the
drifting coefficient, $\beta(z)$, can discriminate with high statistical
significance the degenerate non-standard cosmologies not only from the
$\Lambda$CDM but also from one another. It is concluded that the evolution of
the departure from the Einstein-de Sitter state and spherically symmetric
collapse processes quantified by $\beta(z)$ is a powerful probe of gravity and
dark sector physics. |
Observational constraints on non-flat dynamical dark energy cosmological
models: We constrain two non-flat time-evolving dark energy cosmological models by
using Hubble parameter data, Type Ia supernova apparent magnitude measurements,
and baryonic acoustic oscillation peak length scale observations. The inclusion
of space curvature as a free parameter in the analysis results in a significant
broadening of the allowed range of values of the parameter that governs the
time evolution of the dark energy density in these models. While consistent
with the "standard" spatially-flat $\Lambda$CDM cosmological model, these data
are also consistent with a range of mildly non-flat, slowly time-varying dark
energy models. After marginalizing over all other parameters, these data
require the averaged magnitude of the curvature density parameter
$|\Omega_{k0}| \lesssim 0.15$ at 1$\sigma$ confidence. | Large Blue Spectral Isocurvature Spectral Index Signals Time-Dependent
Mass: We show that if a spectator linear isocurvature dark matter field degree of
freedom has a constant mass through its entire evolution history, the maximum
measurable isocurvature spectral index that is consistent with the current
tensor-to-scalar ratio bound is about 2.4, even if experiments can be sensitive
to a $10^{-6}$ contamination of the predominantly adiabatic power spectrum with
an isocurvature power spectrum at the shortest observable length scales. Hence,
any foreseeable future measurement of a blue isocurvature spectral index larger
than about 2.4 may provide nontrivial evidence for dynamical degrees of freedom
with time-dependent masses during inflation. The bound is not sensitive to the
details of the reheating scenario and can be made mildly smaller if the
tensor-to-scalar ratio is better constrained in the future. |
The XMM-Newton Wide-Field Survey in the COSMOS field (XMM-COSMOS):
demography and multiwavelength properties of obscured and unobscured luminous
AGN: We report the final optical identifications of the medium-depth (~60 ksec),
contiguous (2 deg^2) XMM-Newton survey of the COSMOS field. XMM-Newton has
detected ~800 X-ray sources down to limiting fluxes of ~5x10^{-16},
~3x10^{-15}, and ~7x10^{-15} erg/cm2/s in the 0.5-2 keV, 2-10 keV and 5-10 keV
bands, respectively. The work is complemented by an extensive collection of
multi-wavelength data from 24 micron to UV, available from the COSMOS survey,
for each of the X-ray sources, including spectroscopic redshifts for ~50% of
the sample, and high-quality photometric redshifts for the rest. The XMM and
multiwavelength flux limits are well matched: 1760 (98%) of the X-ray sources
have optical counterparts, 1711 (~95%) have IRAC counterparts, and 1394 (~78%)
have MIPS 24micron detections. Thanks to the redshift completeness (almost
100%) we were able to constrain the high-luminosity tail of the X-ray
luminosity function confirming that the peak of the number density of
logL_X>44.5 AGN is at z~2. Spectroscopically-identified obscured and unobscured
AGN, as well as normal and starforming galaxies, present well-defined optical
and infrared properties. We devised a robust method to identify a sample of
~150 high redshift (z>1), obscured AGN candidates for which optical
spectroscopy is not available. We were able to determine that the fraction of
the obscured AGN population at the highest (L_X>10^{44} erg s^{-1}) X-ray
luminosity is ~15-30% when selection effects are taken into account, providing
an important observational constraint for X-ray background synthesis. We
studied in detail the optical spectrum and the overall spectral energy
distribution of a prototypical Type 2 QSO, caught in a stage transitioning from
being starburst dominated to AGN dominated, which was possible to isolate only
thanks to the combination of X-ray and infrared observations. | Clustering with general photo-$z$ uncertainties: Application to Baryon
Acoustic Oscillations: Photometric data can be analyzed using the three-dimensional correlation
function $\xi_{\rm p}$ to extract cosmological information via e.g.,
measurement of the Baryon Acoustic Oscillations (BAO). Previous studies modeled
$\xi_{\rm p} $ assuming a Gaussian photo-$z$ approximation. In this work we
improve the modeling by incorporating realistic photo-$z$ distribution. We show
that the position of the BAO scale in $\xi_{\rm p}$ is determined by the
photo-$z$ distribution and the Jacobian of the transformation. The latter
diverges at the transverse scale of the separation $s_\perp $, and it explains
why $\xi_{\rm p } $ traces the underlying correlation function at $s_\perp $,
rather than $s$, when the photo-$z$ uncertainty $ \sigma_z / (1+ z) \gtrsim
0.02$. We also obtain the Gaussian covariance for $\xi_{\rm p}$. Due to
photo-$z$ mixing, the covariance of $\xi_{\mathrm{p}}$ shows strong
off-diagonal elements. The high correlation of the data causes some issues to
the data fitting. Nonetheless, we find that either it can be solved by
suppressing the largest eigenvalues of the covariance or it is not directly
related to the BAO. We test our BAO fitting pipeline using a set of mock
catalogs. The data set is dedicated for Dark Energy Survey Year 3 (DES Y3) BAO
analyses and includes realistic photo-$z$ distributions. The theory template is
in good agreement with mock measurement. Based on the DES Y3 mocks, $\xi_{\rm
p}$ statistic is forecast to constrain the BAO shift parameter $\alpha$ to be
$1.001 \pm 0.023$, which is well consistent with the corresponding constraint
derived from the angular correlation function measurements. Thus $\xi_{\rm p}$
offers a competitive alternative for the photometric data analyses. |
Luminosities, Masses and Star Formation Rates of Galaxies at High
Redshift (IAU279 conference proceedings): There has been great progress in recent years in discovering star forming
galaxies at high redshifts (z>5), close to the epoch of reionization of the
intergalactic medium (IGM). The WFC3 and ACS cameras on the Hubble Space
Telescope have enabled Lyman break galaxies to be robustly identified, but the
UV luminosity function and star formation rate density of this population at
z=6-8 seems to be much lower than at z=2-4. High escape fractions and a large
contribution from faint galaxies below our current detection limits would be
required for star-forming galaxies to reionize the Universe. We have also found
that these galaxies have blue rest-frame UV colours, which might indicate lower
dust extinction at z>5. There has been some spectroscopic confirmation of these
Lyman break galaxies through Lyman-alpha emission, but the fraction of galaxies
where we see this line drops at z>7, perhaps due to the onset of the
Gunn-Peterson effect (where the IGM is opaque to Lyman-alpha). | Expansion and Growth of Structure Observables in a Macroscopic Gravity
Averaged Universe: We investigate the effect of averaging inhomogeneities on expansion and
large-scale structure growth observables using the exact and covariant
framework of Macroscopic Gravity (MG). It is well-known that applying the
Einstein's equations and spatial averaging do not commute and lead to the
averaging problem. For the MG formalism applied to the
Friedmann-Lemaitre-Robertson-Walker (FLRW) metric, this gives an extra
dynamical term encapsulated as an averaging density parameter denoted
$\Omega_A$. An exact isotropic cosmological solution of MG for the flat FLRW
metric is already known in the literature, we derive here an anisotropic exact
solution. Using the isotropic solution, we compare the expansion history to
current data of distances to supernovae, Baryon Acoustic Oscillations, CMB last
scattering surface, and Hubble constant measurements, and find $-0.05 \le
\Omega_A \le 0.07$ (at the 95% CL). For the flat metric case this reduces to
$-0.03 \le \Omega_A \le 0.05$. We also find that the inclusion of this term in
the fits can shift the values of the usual cosmological parameters by a few to
several percents. Next, we derive an equation for the growth rate of large
scale structure in MG that includes a term due to the averaging and compare it
to that of the LCDM concordance model. We find that an $\Omega_A$ of an
amplitude range within the bounds above leads to a relative deviation of the
growth from that of the LCDM of up to 2-4% at late times. Thus, the shift in
the growth could be of comparable amplitude to that caused by similar changes
in cosmological parameters like the dark energy density parameter or its
equation of state. The effect could also be comparable in amplitude to some
systematic effects considered for future surveys. This indicates that the
averaging term and its possible effect need to be tightly constrained in future
precision cosmological studies. (Abridged) |
Evolution of the degree of substructures in simulated galaxy clusters: We study the evolution of substructure in the mass distribution with mass,
redshift and radius in a sample of simulated galaxy clusters. The sample,
containing $1226$ objects, spans the mass range $M_{200} = 10^{14} - 1.74
\times 10^{15} \ {\rm M_{\odot}} \ h^{-1}$ in six redshift bins from $z=0$ to
$z=1.179$. We consider three different diagnostics: 1) subhalos identified with
SUBFIND; 2) overdense regions localized by dividing the cluster into octants;
3) offset between the potential minimum and the center of mass. The octant
analysis is a new method that we introduce in this work. We find that none of
the diagnostics indicate a correlation between the mass of the cluster and the
fraction of substructures. On the other hand, all the diagnostics suggest an
evolution of substructures with redshift. For SUBFIND halos, the mass fraction
is constant with redshift at $R_{\mathrm{vir}}$, but shows a mild evolution at
$R_{200}$ and $R_{500}$. Also, the fraction of clusters with at least a subhalo
more massive than one thirtieth of the total mass is less than $20 \%$. Our new
method based on the octants returns a mass fraction in substructures which has
a strong evolution with redshift at all radii. The offsets also evolve strongly
with redshift. We also find a strong correlation for individual clusters
between the offset and the fraction of substructures identified with the octant
analysis. Our work puts strong constraints on the amount of substructures we
expect to find in galaxy clusters and on their evolution with redshift. | Full-sky weak lensing: a nonlinear post-Friedmann treatment: We present a full-sky derivation of weak lensing observables in the
Post-Friedmann (PF) formalism. Weak lensing has the characteristic of mixing
small scales and large scales since it is affected by inhomogeneities
integrated along the photon trajectory. With the PF formalism, we develop a
modelling of lensing observables which encompasses both leading order
relativistic effects and effects that are due to the fully non-linear matter
distribution at small scales. We derive the reduced shear, convergence and
rotation up to order $1/c^4$ in the PF approximation, accounting for scalar,
vector and tensor perturbations, as well as galaxies' peculiar velocities. We
discuss the various contributions that break the Kaiser-Squires relation
between the shear and the convergence at different orders. We pay particular
attention to the impact of the frame-dragging vector potential on lensing
observables and we discuss potential ways to measure this effect in future
lensing surveys. |
The Observable Supernova Rate in Galaxy-Galaxy Lensing Systems with the
TESS Satellite: The Transiting Exoplanet Survey Satellite (TESS) is the latest observational
effort to find exoplanets and map bright transient optical phenomena.
Supernovae (SN) are particularly interesting as cosmological standard candles
for cosmological distance measures. The limiting magnitude of TESS strongly
constrains supernova detection to the very nearby Universe ($m \sim$ 19,
$z<0.05$). We explore the possibility that more distant supernovae that are
gravitationally lensed and magnified by a foreground galaxy can be detected by
TESS, an opportunity to measure the time delay between light paths and
constrain the Hubble constant independently.
We estimate the rate of occurrence of such systems, assuming reasonable
distributions of magnification, host dust attenuation and redshift. There are
approximately 16 type Ia and 43 core-collapse SN (SNcc) expected to be
observable with TESS each year, which translates to 18% and 43% chance of
detection per year, respectively. Monitoring the largest collections of known
strong galaxy-galaxy lenses from Petrillo et al., this translates into 0.6% and
1.3% chances of a SNIa and SNcc per year. The TESS all-sky detection rates are
lower than those of the Zwicky Transient Facility (ZTF) and Vera Rubin
Observatory. However, on the ecliptic poles, TESS performs almost as well as
its all-sky search thanks to its continuous coverage: 2 and 4% chance of an
observed SN (Ia or cc) each year. These rates argue for timely processing of
full-frame TESS imaging to facilitate follow-up and should motivate further
searches for low-redshift lensing system. | Ensemble X-ray variability of Active Galactic Nuclei from serendipitous
source catalogues: The X-ray variability of the Active Galactic Nuclei (AGN) has been most often
investigated with studies of individual, nearby, sources, and only a few
ensemble analyses have been applied to large samples in wide ranges of
luminosity and redshift. We want to determine the ensemble variability
properties of two serendipitously selected AGN samples extracted from the
catalogues of XMM-Newton and Swift, with redshift between ~0.2 and ~4.5, and
X-ray luminosities, in the 0.5-4.5 keV band, between ~10^43 erg/s and ~10^46
erg/s. We use the structure function (SF), which operates in the time domain,
and allows for an ensemble analysis even when only a few observations are
available for individual sources and the power spectral density (PSD) cannot be
derived. SF is also more appropriate than fractional variability and excess
variance, because such parameters are biased by the duration of the monitoring
time interval in the rest-frame, and thus by cosmological time dilation. We
find statistically consistent results for the two samples, with the SF
described by a power law of the time lag, approximately as SF \propto tau^0.1.
We do not find evidence of the break in the SF, at variance with the case of
lower luminosity AGNs. We confirm a strong anti-correlation of the variability
with X-ray luminosity, accompanied by a change of the slope of the SF. We find
evidence in support of a weak, intrinsic, average increase of X-ray variability
with redshift. The change of amplitude and slope of the SF with X-ray
luminosity provides new constraints on both single oscillator models and
multiple subunits models of variability. |
The Evolution of the Baryonic Tully-Fisher Relation over the past 6 Gyr: Scaling relations are salient ingredients of galaxy evolution and formation
models. I summarize results from the IMAGES survey, which combines
spatially-resolved kinematics from FLAMES/GIRAFFE with imaging from HST/ACS and
other facilities. Specifically, I will focus on the evolution of the stellar
mass and baryonic Tully-Fisher Relations (TFR) from z=0.6 down to z=0. We found
a significant evolution in zero point and scatter of the stellar mass TFR
compared to the local Universe. Combined with gas fractions derived by
inverting the Schmidt-Kennicutt relation, we derived for the first time a
baryonic TFR at high redshift. Conversely to the stellar mass TFR, the baryonic
relation does not appear to evolve in zero point, which suggests that most of
the reservoir of gas converted into stars over the past 6 Gyr was already
gravitationally bound to galaxies at z=0.6. | Gravity Waves as a Probe of Hubble Expansion Rate During An Electroweak
Scale Phase Transition: Just as big bang nucleosynthesis allows us to probe the expansion rate when
the temperature of the universe was around 1 MeV, the measurement of gravity
waves from electroweak scale first order phase transitions may allow us to
probe the expansion rate when the temperature of the universe was at the
electroweak scale. We compute the simple transformation rule for the gravity
wave spectrum under the scaling transformation of the Hubble expansion rate. We
then apply this directly to the scenario of quintessence kination domination
and show how gravity wave spectra would shift relative to LISA and BBO
projected sensitivities. |
Dark energy from the gas of wormholes: We assume the space-time foam picture in which the vacuum is filled with a
gas of virtual wormholes. It is shown that virtual wormholes form a finite (of
the Planckian order) value of the energy density of zero-point fluctuations.
However such a huge value is compensated by the contribution of virtual
wormholes to the mean curvature and the observed value of the cosmological
constant is close to zero. A non-vanishing value appears due to the
polarization of vacuum in external classical fields. In the early Universe some
virtual wormholes may form actual ones. We show that in the case of actual
wormholes vacuum polarization effects are negligible while their contribution
to the mean curvature is apt to form the observed dark energy phenomenon. Using
the contribution of wormholes to dark matter and dark energy we find estimates
for characteristic parameters of the gas of wormholes. | Dark matter halos in the multicomponent model. II. Density profiles of
galactic halos: The multicomponent dark matter model with self-scattering and
inter-conversions of species into one another is an alternative dark matter
paradigm that is capable of resolving the long-standing problems of
$\Lambda$CDM cosmology at small scales. In this paper, we have studied in
detail the properties of dark matter halos with $M \sim 4-5 \times10^{11}
M_{\odot}$ obtained in $N$-body cosmological simulations with the simplest
two-component (2cDM) model. A large set of velocity-dependent cross-section
prescriptions for elastic scattering and mass conversions, $\sigma_s(v)\propto
v^{a_s}$ and $\sigma_c(v)\propto v^{a_c}$, has been explored and the results
were compared with observational data. The results demonstrate that
self-interactions with the cross-section per particle mass evaluated at $v=100$
km s$^{-1}$ being in the range of $0.01\lesssim \sigma_0/m\lesssim 1$
cm$^2$g$^{-1}$ robustly suppress central cusps, thus resolving the core-cusp
problem. The core radii are controlled by the values of $\sigma_0/m$ and the DM
cross-section's velocity-dependent power-law indices $(a_s,a_c)$, but are
largely insensitive to the species' mass degeneracy. These values are in full
agreement with those resolving the substructure and too-big-to-fail problems.
We have also studied the evolution of halos in the 2cDM model with cosmic time. |
Void bias from primordial non-Gaussianities: We study how primordial non-Gaussianities affect the clustering of voids at
large scales. We derive a formula of the bias of voids induced from the
non-Gaussianities by making use of the functional integral method. In a similar
way as of haloes, we find that primordial non-Gaussianities can generate
scale-dependence in the bias of voids at large scales. In addition, we show
that by observing the cross power spectrum of voids and haloes we could check
the consistency relation between the non-linearity parameters f_NL and tau_NL.
Large voids (high peak objects) would be good targets since the effects of
non-Gaussianities are more prominent while the effects of "void-in-cloud" are
less significant. | Euclid: impact of nonlinear prescriptions on cosmological parameter
estimation from weak lensing cosmic shear: Upcoming surveys will map the growth of large-scale structure with
unprecented precision, improving our understanding of the dark sector of the
Universe. Unfortunately, much of the cosmological information is encoded by the
small scales, where the clustering of dark matter and the effects of
astrophysical feedback processes are not fully understood. This can bias the
estimates of cosmological parameters, which we study here for a joint analysis
of mock Euclid cosmic shear and Planck cosmic microwave background data. We use
different implementations for the modelling of the signal on small scales and
find that they result in significantly different predictions. Moreover, the
different nonlinear corrections lead to biased parameter estimates, especially
when the analysis is extended into the highly nonlinear regime, with both the
Hubble constant, $H_0$, and the clustering amplitude, $\sigma_8$, affected the
most. Improvements in the modelling of nonlinear scales will therefore be
needed if we are to resolve the current tension with more and better data. For
a given prescription for the nonlinear power spectrum, using different
corrections for baryon physics does not significantly impact the precision of
Euclid, but neglecting these correction does lead to large biases in the
cosmological parameters. In order to extract precise and unbiased constraints
on cosmological parameters from Euclid cosmic shear data, it is therefore
essential to improve the accuracy of the recipes that account for nonlinear
structure formation, as well as the modelling of the impact of astrophysical
processes that redistribute the baryons. |
Gravitational lensing of gravitational waves: A statistical perspective: In this paper, we study the strong gravitational lensing of gravitational
waves (GWs) from a statistical perspective, with particular focus on the high
frequency GWs from stellar binary black hole coalescences. These are most
promising targets for ground-based detectors such as Advanced Laser
Interferometer Gravitational Wave Observatory (aLIGO) and the proposed Einstein
Telescope (ET) and can be safely treated under the geometrical optics limit for
GW propagation. We perform a thorough calculation of the lensing rate, by
taking account of effects caused by the ellipticity of lensing galaxies, lens
environments, and magnification bias. We find that in certain GW source rate
scenarios, we should be able to observe strongly lensed GW events once per year
($\sim1~\text{yr}^{-1}$) in the aLIGO survey at its design sensitivity; for the
proposed ET survey, the rate could be as high as $\sim80~\text{yr}^{-1}$. These
results depend on the estimate of GW source abundance, and hence can be
correspondingly modified with an improvement in our understanding of the merger
rate of stellar binary black holes. We also compute the fraction of four-image
lens systems in each survey, predicting it to be $\sim30$ per cent for the
aLIGO survey and $\sim6$ per cent for the ET survey. Finally, we evaluate the
possibility of missing some images due to the finite survey duration, by
presenting the probability distribution of lensing time delays. We predict that
this selection bias will be insignificant in future GW surveys, as most of the
lens systems ($\sim90$ per cent) will have time delays less than $\sim1$ month,
which will be far shorter than survey durations. | SZ power spectrum and cluster numbers from an extended merger-tree model: We have recently developed an extended merger-tree model that efficiently
follows hierarchical evolution of galaxy clusters and provides a quantitative
description of both their dark matter and gas properties. We employed this
diagnostic tool to calculate the thermal SZ power spectrum and cluster number
counts, accounting explicitly for uncertainties in the relevant statistical and
intrinsic cluster properties, such as the halo mass function and the gas
equation of state. Results of these calculations are compared with those
obtained from a direct analytic treatment and from hydrodynamical simulations.
We show that under certain assumptions on the gas mass fraction our results are
consistent with the latest SPT measurement. Our approach can be particularly
useful in predicting cluster number counts and their dependence on cluster and
cosmological parameters. |
Modelling the Energy Spectra of Radio Relics: Radio relics are diffuse synchrotron sources that illuminate shock waves in
the intracluster medium. In recent years, radio telescopes have provided
detailed observations about relics. Consequently, cosmological simulations of
radio relics need to provide a similar amount of detail. In this methodological
work, we include information on adiabatic compression and expansion, which have
been neglected in the past in the modelling of relics. In a cosmological
simulation of a merging galaxy cluster, we follow the energy spectra of shock
accelerated cosmic-ray electrons using Lagrangian tracer particles. On board of
each tracer particle, we compute the temporal evolution of the energy spectrum
under the influence of synchrotron radiation, inverse Compton scattering, and
adiabatic compression and expansion. Exploratory tests show that the total
radio power and, hence, the integrated radio spectrum are not sensitive to the
adiabatic processes. This is attributed to small changes in the compression
ratio over time. | Generation of Primordial Black Holes and Gravitational Waves from
Dilaton-Gauge Field Dynamics: We study the observational signatures from particle production of a $U(1)$
gauge field kinetically coupled to an inflaton. Regarding the form of gauge
kinetic function, we consider the possibility that it becomes stabilized at a
certain time, which makes the growing power of the gauge field evolve
non-monotonically with a sharp transition. Remarkably, the copious production
of the gauge field occurs on super-horizon scales at the late stage of
inflation and perturbations are enhanced on the intermediate scales during
inflation. We find that it can predict a bumpy shape of the curvature power
spectrum which leads to the generation of primordial black holes as a dark
matter after inflation. We also estimate two types of tensor modes sourced by
the gauge field: the primordial gravitational waves generated during inflation
and the induced gravitational waves provided by the enhanced curvature
perturbation after inflation. We show that both of them are potentially
testable with the future space-based gravitational wave interferometers. |
Possible evidence for a large-scale enhancement in the Lyman-$α$
forest power spectrum at redshift $\mathbf{\textit{z}\geq 4}$: Inhomogeneous reionization enhances the 1D Lyman-$\alpha$ forest power
spectrum on large scales at redshifts $z\geq4$. This is due to coherent
fluctuations in the ionized hydrogen fraction that arise from large-scale
variations in the post-reionization gas temperature, which fade as the gas
cools. It is therefore possible to use these relic fluctuations to constrain
inhomogeneous reionization with the power spectrum at wavenumbers
$\log_{10}(k/{\rm km^{-1}\,s})\lesssim -1.5$. We use the Sherwood-Relics suite
of hybrid radiation hydrodynamical simulations to perform a first analysis of
new Lyman-$\alpha$ forest power spectrum measurements at $4.0\leq z \leq 4.6$.
These data extend to wavenumbers $\log_{10}(k/{\rm km^{-1}\,s})\simeq -3$, with
a relative uncertainty of $10$--$20$ per cent in each wavenumber bin. Our
analysis returns a $2.7\sigma$ preference for an enhancement in the
Lyman-$\alpha$ forest power spectrum at large scales, in excess of that
expected for a spatially uniform ultraviolet background. This large-scale
enhancement could be a signature of inhomogeneous reionization, although the
statistical precision of these data is not yet sufficient for obtaining a
robust detection of the relic post-reionization fluctuations. We show that
future power spectrum measurements with relative uncertainties of $\lesssim
2.5$ per cent should provide unambiguous evidence for an enhancement in the
power spectrum on large scales. | Inflation, SUSY breaking, and primordial black holes in modified
supergravity coupled to chiral matter: We propose a novel model of the modified (Starobinsky-like) old-minimal-type
supergravity coupled to a chiral matter superfield, that can {\it
simultaneously} describe multi-field inflation, primordial black hole (PBH)
formation, dark matter (DM), and spontaneous supersymmetry (SUSY) breaking
after inflation in a Minkowski vacuum. The PBH masses in our supergravity model
of double slow-roll inflation, with a short phase of "ultra-slow-roll" between
two slow-roll phases, are close to $10^{18}$ g. We find that a significant PBH
fraction in the allowed mass window can be supplemented by spontaneous SUSY
breaking in the vacuum with the gravitino mass close to the scalaron (inflaton)
mass M of the order $10^{13}$ GeV. Our supergravity model favors the {\it
composite} nature of DM as a mixture of PBH and heavy gravitinos as the
lightest SUSY particles. The composite DM significantly relaxes fine-tuning
needed for the whole PBH-DM. The PBH-DM fraction is derived, and the
second-order gravitational wave background induced by the enhanced scalar
perturbations is calculated. Those gravitational waves may be accessible by the
future space-based gravitational interferometers. |
Detection of the Intrinsic Spin Alignments in Isolated Spiral Pairs: An observational evidence for the intrinsic galaxy alignments in isolated
spiral pairs is presented. From the catalog of the galaxy groups identified by
Tempel et al. in the flux limited galaxy sample of the Sloan Digital Sky Survey
Data Release 10, we select those groups consisting only of two spiral galaxies
as isolated spiral pairs and investigate if and how strongly the spin axes of
their two spiral members are aligned with each other. We detect a clear signal
of intrinsic spin alignment in the isolated spiral pairs, which leads to the
rejection of the null hypothesis at the $99.9999\%$ confidence level via the
Rayleigh test. It is also found that those isolated pairs comprising two
early-type spiral galaxies exhibit the strongest signal of intrinsic spin
alignment and that the strength of the alignment signal depends on the angular
separation distance as well as on the luminosity ratio of the member galaxies.
Using the dark matter halos consisting of only two subhalos resolved in the
EAGLE hydrodynamic simulations, we repeat the same analysis but fail to find
any alignment tendency between the spin angular momentum vectors of the stellar
components of the subhalos, which is in tension with the observational result.
A couple of possible sources of this apparent inconsistency between the
observational and the numerical results are discussed. | Cosmological Model Independent Time Delay Method: We propose a Cosmological Model Independent Time Delay (CMITD) method where
the Lorentz invariance violation (LIV) variable $K(z)$ is constructed by
observational data instead of cosmological model. The simulated time delay data
show the CMITD method could present the validity of LIV test. And, the errors
in the propagating process is critical for the existence and magnitude of LIV. |
An Analytic Hybrid Halo + Perturbation Theory Model for Small-scale
Correlators: Baryons, Halos, and Galaxies: We update Halo Zeldovich Perturbation Theory (HZPT), an analytic model for
the two-point statistics of dark matter, to describe halo and galaxy
clustering, and galaxy-matter cross-correlation on nonlinear scales. The model
correcting Zeldovich has an analytic Fourier transform, and therefore is valid
in both configuration space and Fourier space. The model is accurate at the
$2\%$-level or less for $P_{mm}$ (k < 1 h/Mpc), $P_{hm}$ (k < 1 h/Mpc),
$P_{hh}$ (k < 2 h/Mpc), $P_{gm}$ (k < 1 h/Mpc), $P_{gg}$ (k < 1 h/Mpc),
$\xi_{mm}$ (r > 1 Mpc/h), $\xi_{hm}$ (r > 2 Mpc/h), $\xi_{hh}$ (r > 2 Mpc/h),
$\xi_{gm}$ (r > 1 Mpc/h), $\xi_{gg}$ (r > 2 Mpc/h), for LRG-like mock galaxies.
We show that the HZPT model for matter correlators can account for the effects
of a wide range of baryonic feedback models and provide extended dark matter
models which are of $1\% ~(3\%)$ accuracy for k < 10 (8) h/Mpc. We explicitly
model the non-perturbative features of halo exclusion for the halo-halo and
galaxy-galaxy correlators, as well as the presence of satellites for
galaxy-matter and galaxy-galaxy correlation functions. We perform density
estimation using N-body simulations and a wide range of HOD galaxy mocks to
obtain correlations of model parameters with the cosmological parameters
$\Omega_{m}$ and $\sigma_{8}$. HZPT can provide a fast, interpretable, and
analytic model for combined-probe analyses of redshift surveys using scales
well into the non-linear regime. | Cosmological cluster tension: The abundance of clusters is a classical cosmological probe sensitive to both
the geometrical aspects and the growth rate of structures. The abundance of
clusters of galaxies measured by Planck has been found to be in tension with
the prediction of the LCDM models normalized to Planck CMB fluctuations power
spectra. The same tension appears with X-ray cluster local abundance. Massive
neutrinos and modified gravity are two possible solutions to fix this tension.
Alternatively, others options include a bias in the selection procedure or in
the mass calibration of clusters. We present a study, based on our recent work,
updating the present situation on this topic and discuss the likelihood of the
various options. |
CMB dipole asymmetry from a fast roll phase: The observed CMB (cosmic microwave background) dipole asymmetry cannot be
explained by a single field model of inflation - it inevitably requires more
than one field where one of the fields is responsible for amplifying the
super-Hubble fluctuations beyond the pivot scale. Furthermore the current
constraints on $f_NL$ and $tau_NL$ require that such an amplification cannot
produce large non-Gaussianity. In this paper we propose a model to explain this
dipole asymmetry from a spectator field, which is responsible for generating
all the curvature perturbations, but has a temporary fast roll phase before the
Hubble exit of the pivot scale. The current data prefers spectator scenario
because it leaves no isocurvature perturbations. The spectator model will also
satisfy the well-known constraints arising from quasars, and the quadrupole and
octupole of the CMB. | Stars were born in significantly denser regions in the early Universe: The density of the warm ionized gas in high-redshift galaxies is known to be
higher than what is typical in local galaxies on similar scales. At the same
time, the mean global properties of the high- and low-redshift galaxies are
quite different. Here, we present a detailed differential analysis of the
ionization parameters of 14 star-forming galaxies at redshift 2.6-3.4, compiled
from the literature. For each of those high-redshift galaxies, we construct a
comparison sample of low-redshift galaxies closely matched in specific star
formation rate (sSFR) and stellar mass, thus ensuring that their global
physical conditions are similar to the high-redshift galaxy. We find that the
median log [OIII] 5007/ [OII] 3727 line ratio of the high-redshift galaxies is
0.5 dex higher than their local counterparts. We construct a new calibration
between the [OIII] 5007/ [OII] 3727 emission line ratio and ionization
parameter to estimate the difference between the ionization parameters in the
high and low-redshift samples. Using this, we show that the typical density of
the warm ionized gas in star-forming regions decreases by a median factor of
$7.1^{+10.2}_{-5.4}$ from z ~ 3.3 to z ~ 0 at fixed mass and sSFR. We show that
metallicity differences cannot explain the observed density differences.
Because the high- and low-redshift samples are comparable in size, we infer
that the relationship between star formation rate density and gas density must
have been significantly less efficient at z ~2-3 than what is observed in
nearby galaxies with similar levels of star formation activity. |
An HI view of the on-going assembly of early-type galaxies: present and
future observations: We present a preliminary analysis of the HI properties of early-type galaxies
in the ATLAS3D sample. Using WSRT data for ~100 galaxies outside the Virgo
cluster and data from the Alfalfa project for galaxies inside Virgo, we discuss
the dependence of HI properties on environment. We detect HI in about half of
the galaxies outside Virgo. For these systems, the HI morphology and kinematics
change as a function of environment, going from regular, rotating systems
around isolated galaxies to progressively more disturbed structures for
galaxies with neighbours or in groups. In denser environment, inside Virgo,
nearly none of the galaxies contains HI.
We discuss future work in this field which will be enabled by
next-generation, pre-SKA radio instruments. We present a simulated Apertif HI
observation of an ATLAS3D early-type galaxy, showing how its appearance and
detection level vary as a function of redshift. | C$^3$-Cluster Clustering Cosmology I. New constraints on the cosmic
growth rate at z~0.3 from redshift-space clustering anisotropies: Redshift-space distortions in the clustering of galaxy clusters provide a
novel probe to test the gravity theory on cosmological scales. The aim of this
work is to derive new constraints on the linear growth rate of cosmic
structures from the redshift-space two-point correlation function of galaxy
clusters. We construct a large spectroscopic catalogue of optically-selected
clusters from the Sloan Digital Sky Survey. The selected sample consists of
$43,743$ clusters in the redshift range $0.1<z<0.42$, with masses estimated
from weak-lensing calibrated scaling relations. We measure the transverse and
radial wedges of the two-point correlation function of the selected clusters.
Modelling the redshift-space clustering anisotropies, we provide the first
constraints on the linear growth rate from cluster clustering. The cluster
masses are used to set a prior on the linear bias of the sample. This
represents the main advantage in using galaxy clusters as cosmic probes,
instead of galaxies. Assuming a standard cosmological model consistent with the
latest cosmic microwave background constraints, we do not find any evidence of
deviations from General Relativity. Specifically, we get the value of the
growth rate times the matter power spectrum normalisation parameter
$f\sigma_{8}=0.44\pm0.05$, at an effective redshift $z=0.275$. |
Non-Gaussian statistics of critical sets in 2 and 3D: Peaks, voids,
saddles, genus and skeleton: The formalism to compute the geometrical and topological one-point statistics
of mildly non-Gaussian 2D and 3D cosmological fields is developed. Leveraging
the isotropy of the target statistics, the Gram-Charlier expansion is
reformulated with rotation invariant variables. This formulation allows us to
track the geometrical statistics of the cosmic field to all orders. It then
allows us to connect the one point statistics of the critical sets to the
growth factor through perturbation theory, which predicts the redshift
evolution of higher order cumulants. In particular, the cosmic non-linear
evolution of the skeleton's length, together with the statistics of extrema and
Euler characteristic are investigated in turn. In 2D, the corresponding
differential densities are analytic as a function of the excursion set
threshold and the shape parameter. In 3D, the Euler characteristics and the
field isosurface area are also analytic to all orders in the expansion.
Numerical integrations are performed and simple fits are provided whenever
closed form expressions are not available. These statistics are compared to
estimates from N-body simulations and are shown to match well the cosmic
evolution up to root mean square of the density field of ~0.2. In 3D,
gravitational perturbation theory is implemented to predict the cosmic
evolution of all the relevant Gram-Charlier coefficients for universes with
scale invariant matter distribution. The one point statistics of critical sets
could be used to constrain primordial non-Gaussianities and the dark energy
equation of state on upcoming cosmic surveys; this is illustrated on idealized
experiments. | Study of the chemical evolution and spectral signatures of some
interstellar precursor molecules of adenine, glycine alanine: We carry out a quantum chemical calculation to obtain the infrared and
electronic absorption spectra of several complex molecules of the interstellar
medium (ISM). These molecules are the precursors of adenine, glycine & alanine.
They could be produced in the gas phase as well as in the ice phase. We carried
out a hydro-chemical simulation to predict the abundances of these species in
the gas as well as in the ice phase. Gas and grains are assumed to be
interacting through the accretion of various species from the gas phase on to
the grain surface and desorption (thermal evaporation and photo-evaporation)
from the grain surface to the gas phase. Depending on the physical properties
of the cloud, the calculated abundances varies. The influence of ice on
vibrational frequencies of different pre-biotic molecules was obtained using
Polarizable Continuum Model (PCM) model with the integral equation formalism
variant (IEFPCM) as default SCRF method with a dielectric constant of 78.5.
Time dependent density functional theory (TDDFT) is used to study the
electronic absorption spectrum of complex molecules which are biologically
important such as, formamide and precursors of adenine, alanine and glycine. We
notice a significant difference between the spectra of the gas and ice phase
(water ice). The ice could be mixed instead of simple water ice. We have varied
the ice composition to find out the effects of solvent on the spectrum. We
expect that our study could set the guidelines for observing the precursor of
some bio-molecules in the interstellar space. |
The Effect of Spatial Gradients in Stellar Mass-to-Light Ratio on Black
Hole Mass Measurements: We have tested the effect of spatial gradients in stellar mass-to-light ratio
(Y) on measurements of black hole masses (MBH) derived from stellar orbit
superposition models. Such models construct a static gravitational potential
for a galaxy and its central black hole, but typically assume spatially uniform
Y. We have modeled three giant elliptical galaxies with gradients alpha = d(log
Y)/d(log r) from -0.2 to +0.1. Color and line strength gradients suggest mildly
negative alpha in these galaxies. Introducing a negative (positive) gradient in
Y increases (decreases) the enclosed stellar mass near the center of the galaxy
and leads to systematically smaller (larger) MBH measurements. For models with
alpha = -0.2, the best-fit values of MBH are 28%, 27%, and 17% lower than the
constant-Y case, in NGC 3842, NGC 6086, and NGC 7768, respectively. For alpha =
+0.1, MBH are 14%, 22%, and 17% higher than the constant-Y case for the three
respective galaxies. For NGC 3842 and NGC 6086, this bias is comparable to the
statistical errors from individual modeling trials. At larger radii, negative
(positive) gradients in Y cause the total stellar mass to decrease (increase)
and the dark matter fraction within one effective radius to increase
(decrease). | Using the cosmological recombination radiation to probe early dark
energy and fundamental constant variations: The cosmological recombination radiation (CRR) is one of the guaranteed
spectral distortion signals from the early Universe. The CRR photons from
hydrogen and helium pre-date the last scattering process and as such allow
probing physical phenomena in the pre-recombination era. Here we compute the
modifications to the CRR caused by early dark energy models and varying
fundamental constants. These new physics examples have seen increased recent
activity in connection with the Hubble tension, motivating the exploratory
study presented here. The associated CRR responses are spectrally-rich but the
level of the signals is small. We forecast the possible sensitivity of future
spectrometers to these effects. Our estimates demonstrate that the CRR directly
depends to changes in the expansion history and recombination physics during
the pre-recombination era. However, futuristic sensitivities are required for
spectrometer-only constraints that are competitive with other cosmological
probes. Nevertheless, measurements of the CRR can directly reach into phases
that otherwise remain inaccessible, highlighting the potential these types of
observations could have as a probe of the early Universe. A combination with
${\it Planck}$ data further shows that a synergistic approach is very
promising. |
Cosmological-model-independent tests of cosmic distance duality relation
with Type Ia supernovae and radio quasars: In this paper, we investigate the possible deviations of the cosmic distance
duality relation (CDDR) using the combination of the largest SNe Ia (Pantheon)
and compact radio quasar (QSO) samples through two model-independent
approaches. The deviation of CDDR is written as
$D_L(z)/D_A(z)(1+z)^{-2}=\eta(z)$ and $\eta(z)=e^{\tau(z)/2}$, with the
parameterizations of $F_1$ ($\tau(z) = 2\epsilon_1 z$) and $F_2$ ($\tau(z) =
(1+z)^{2\epsilon_2}-1$). Furthermore, in order to compare the two resulting
distances, two cosmological-model-independent methods, i.e., the nearby SNe Ia
method and the GP method are employed to match the two distinct data at the
same redshift. Our findings indicate that, compared with the results obtained
in the literature, there is an improvement in precision when the latest SNe Ia
and QSO samples are used. Specially, in the framework of nearby SNe Ia method,
the CDDR would be constrained at the precision of $\Delta\epsilon_{1} = 0.013$
in Model $F_1$ and $\Delta\epsilon_{2}=0.018$ in Model $F_2$. Regarding the GP
method, one observes that a larger data size would produce more stringent
constraints on the CDDR parameters. Therefore, accompanied by further
developments in cosmological observations and the analysis methods, our
analysis provides an insight into the evidence for unaccounted opacity sources
at an earlier stage of the universe, or at the very least the new physics
involved. | Near-Infrared Properties of Type Ia Supernovae: The photometric properties of Type Ia supernovae (SNe Ia) in the
near-infrared as garnered from observations made over the last 30 years are
reviewed. During this period, light curves for more than 120 nearby SNe Ia have
been published, revealing considerable homogeneity but also some fascinating
differences. These data have confirmed that, for all but the fastest declining
objects, SNe Ia are essentially perfect standard candles in the near-infrared,
displaying only a slight dependence of peak luminosity on decline rate and
color. |
Reconstruction of the Primordial Power Spectrum using Temperature and
Polarisation Data from Multiple Experiments: We develop a method to reconstruct the primordial power spectrum, P(k), using
both temperature and polarisation data from the joint analysis of a number of
Cosmic Microwave Background (CMB) observations. The method is an extension of
the Richardson-Lucy algorithm, first applied in this context by Shafieloo &
Souradeep. We show how the inclusion of polarisation measurements can decrease
the uncertainty in the reconstructed power spectrum. In particular, the
polarisation data can constrain oscillations in the spectrum more effectively
than total intensity only measurements. We apply the estimator to a compilation
of current CMB results. The reconstructed spectrum is consistent with the
best-fit power spectrum although we find evidence for a `dip' in the power on
scales k ~ 0.002 Mpc^-1. This feature appears to be associated with the WMAP
power in the region 18 < l < 26 which is consistently below best--fit models.
We also forecast the reconstruction for a simulated, Planck-like survey
including sample variance limited polarisation data. | Probing spatial homogeneity with LTB models: a detailed discussion: Do current observational data confirm the assumptions of the cosmological
principle, or is there statistical evidence for deviations from spatial
homogeneity on large scales? To address these questions, we developed a
flexible framework based on spherically symmetric, but radially inhomogeneous
Lemaitre-Tolman-Bondi (LTB) models with synchronous Big Bang. We expanded the
(local) matter density profile in terms of flexible interpolation schemes and
orthonormal polynomials. A Monte Carlo technique in combination with recent
observational data was used to systematically vary the shape of these profiles.
In the first part of this article, we reconsider giant LTB voids without dark
energy to investigate whether extremely fine-tuned mass profiles can reconcile
these models with current data. While the local Hubble rate and supernovae can
easily be fitted without dark energy, however, model-independent constraints
from the Planck 2013 data require an unrealistically low local Hubble rate,
which is strongly inconsistent with the observed value; this result agrees well
with previous studies. In the second part, we explain why it seems natural to
extend our framework by a non-zero cosmological constant, which then allows us
to perform general tests of the cosmological principle. Moreover, these
extended models facilitate explorating whether fluctuations in the local matter
density profile might potentially alleviate the tension between local and
global measurements of the Hubble rate, as derived from Cepheid-calibrated type
Ia supernovae and CMB experiments, respectively. We show that current data
provide no evidence for deviations from spatial homogeneity on large scales.
More accurate constraints are required to ultimately confirm the validity of
the cosmological principle, however. |
The AGN, Star-Forming, and Morphological Properties of Luminous
IR-Bright/Optically-Faint Galaxies: We present the AGN, star-forming, and morphological properties of a sample of
13 MIR-luminous (f(24) > 700uJy) IR-bright/optically-faint galaxies (IRBGs,
f(24)/f(R) > 1000). While these z~2 sources were drawn from deep Chandra fields
with >200 ks X-ray coverage, only 7 are formally detected in the X-ray and four
lack X-ray emission at even the 2 sigma level. Spitzer IRS spectra, however,
confirm that all of the sources are AGN-dominated in the mid-IR, although half
have detectable PAH emission responsible for ~25% of their mid-infrared flux
density. When combined with other samples, this indicates that at least 30-40%
of luminous IRBGs have star-formation rates in the ULIRG range (~100-2000
Msun/yr). X-ray hardness ratios and MIR to X-ray luminosity ratios indicate
that all members of the sample contain heavily X-ray obscured AGN, 80% of which
are candidates to be Compton-thick. Furthermore, the mean X-ray luminosity of
the sample, log L(2-10 keV)(ergs/s)=44.6, indicates that these IRBGs are Type 2
QSOs, at least from the X-ray perspective. While those sources most heavily
obscured in the X-ray are also those most likely to display strong silicate
absorption in the mid-IR, silicate absorption does not always accompany X-ray
obscuration. Finally, ~70% of the IRBGs are merger candidates, a rate
consistent with that of sub-mm galaxies (SMGs), although SMGs appear to be
physically larger than IRBGs. These characteristics are consistent with the
proposal that these objects represent a later, AGN-dominated, and more relaxed
evolutionary stage following soon after the star-formation-dominated one
represented by the SMGs. | Cosmological constraints with weak lensing peak counts and second-order
statistics in a large-field survey: Peak statistics in weak lensing maps access the non-Gaussian information
contained in the large-scale distribution of matter in the Universe. They are
therefore a promising complement to two-point and higher-order statistics to
constrain our cosmological models. To prepare for the high-precision data of
next-generation surveys, we assess the constraining power of peak counts in a
simulated Euclid-like survey on the cosmological parameters
$\Omega_\mathrm{m}$, $\sigma_8$, and $w_0^\mathrm{de}$. In particular, we study
how the Camelus model--a fast stochastic algorithm for predicting peaks--can be
applied to such large surveys. We measure the peak count abundance in a mock
shear catalogue of ~5,000 sq. deg. using a multiscale mass map filtering
technique. We then constrain the parameters of the mock survey using Camelus
combined with approximate Bayesian computation (ABC). We find that peak
statistics yield a tight but significantly biased constraint in the
$\sigma_8$-$\Omega_\mathrm{m}$ plane, indicating the need to better understand
and control the model's systematics. We calibrate the model to remove the bias
and compare results to those from the two-point correlation functions (2PCF)
measured on the same field. In this case, we find the derived parameter
$\Sigma_8=\sigma_8(\Omega_\mathrm{m}/0.27)^\alpha=0.76_{-0.03}^{+0.02}$ with
$\alpha=0.65$ for peaks, while for 2PCF the value is
$\Sigma_8=0.76_{-0.01}^{+0.02}$ with $\alpha=0.70$. We therefore see comparable
constraining power between the two probes, and the offset of their
$\sigma_8$-$\Omega_\mathrm{m}$ degeneracy directions suggests that a combined
analysis would yield tighter constraints than either measure alone. As
expected, $w_0^\mathrm{de}$ cannot be well constrained without a tomographic
analysis, but its degeneracy directions with the other two varied parameters
are still clear for both peaks and 2PCF. (abridged) |
One Thousand and One Clusters: Measuring the Bulk Flow with the Planck
ESZ and X-Ray Selected Galaxy Cluster Catalogs: We present our measurement of the "bulk flow" using the kinetic
Sunyaev-Zel'dovich (kSZ) effect in the WMAP 7-year data. As the tracer of
peculiar velocities, we use Planck Early Sunyaev-Zel'dovich Detected Cluster
Catalog and a compilation of X-ray detected galaxy cluster catalogs based on
ROSAT All-Sky Survey. We build a full-sky kSZ template and fit it to the WMAP
data in W-band. Using a Wiener filter we maximize the signal to noise ratio of
the kSZ cluster signal in the data. We find no significant detection of the
bulk flow, and our results are consistent with the LCDM prediction. | A Maximum Likelihood Approach to Estimating Correlation Functions: We define a Maximum Likelihood (ML for short) estimator for the correlation
function, {\xi}, that uses the same pair counting observables (D, R, DD, DR,
RR) as the standard Landy and Szalay (1993, LS for short) estimator. The ML
estimator outperforms the LS estimator in that it results in smaller
measurement errors at any fixed random point density. Put another way, the ML
estimator can reach the same precision as the LS estimator with a significantly
smaller random point catalog. Moreover, these gains are achieved without
significantly increasing the computational requirements for estimating {\xi}.
We quantify the relative improvement of the ML estimator over the LS estimator,
and discuss the regimes under which these improvements are most significant. We
present a short guide on how to implement the ML estimator, and emphasize that
the code alterations required to switch from a LS to a ML estimator are
minimal. |
Deep Absorption Line Studies of Quiescent Galaxies at z~2: The Dynamical
Mass-Size Relation, and First Constraints on the Fundamental plane: We present dynamical and structural scaling relations of quiescent galaxies
at z=2, including the dynamical mass-size relation and the first constraints on
the fundamental plane (FP). The backbone of the analysis is a new, very deep
VLT/X-shooter spectrum of a massive, compact, quiescent galaxy at z=2.0389. We
detect the continuum between 3700-22000A and several strong absorption features
(Balmer series, Ca H+K, G-band), from which we derive a stellar velocity
dispersion of 318 +/- 53 km/s. We perform detailed modeling of the continuum
emission and line indices and derive strong simultaneous constraints on the
age, metallicity, and stellar mass. The galaxy is a dusty (A_V=0.77
(+0.36,-0.32)) solar metallicity (log(Z/Zsun) = 0.02 (+0.20,-0.41)) post
starburst galaxy, with a mean luminosity weighted log(age/yr) of 8.9 +/- 0.1.
The galaxy formed the majority of its stars at z>3 and currently has little or
no ongoing star formation. We compile a sample of three other z~2 quiescent
galaxies with measured velocity dispersions, two of which are also post
starburst like. Their dynamical mass-size relation is offset significantly less
than the stellar mass-size relation from the local early type relations, which
we attribute to a lower central dark matter fraction. Recent cosmological
merger simulations qualitatively agree with the data, but can not fully account
for the evolution in the dark matter fraction. The z~2 FP requires additional
evolution beyond passive stellar aging, to be in agreement with the local FP.
The structural evolution predicted by the cosmological simulations is
insufficient, suggesting that additional, possibly non-homologous structural
evolution is needed. | The source-lens clustering effect in the context of lensing tomography
and its self-calibration: Cosmic shear can only be measured where there are galaxies. This source-lens
clustering (SLC) effect has two sources, intrinsic source clustering and cosmic
magnification (magnification/size bias). Lensing tomography can suppress the
former. However, this reduction is limited by the existence of photo-z error
and nonzero redshift bin width. Furthermore, SLC induced by cosmic
magnification cannot be reduced by lensing tomography. Through N-body
simulations, we quantify the impact of SLC on the lensing power spectrum in the
context of lensing tomography. We consider both the standard estimator and the
pixel-based estimator. We find that none of them can satisfactorily handle both
sources of SLC. (1) For the standard estimator, SLC induced by both sources can
bias the lensing power spectrum by O(1)-O(10)%. Intrinsic source clustering
also increases statistical uncertainties in the measured lensing power
spectrum. However, the standard estimator suppresses intrinsic source
clustering in the cross-spectrum. (2) In contrast, the pixel-based estimator
suppresses SLC through cosmic magnification. However, it fails to suppress SLC
through intrinsic source clustering and the measured lensing power spectrum can
be biased low by O(1)-O(10)%. In short, for typical photo-z errors
(sigma_z/(1+z)=0.05) and photo-z bin sizes (Delta_z^P=0.2), SLC alters the
lensing E-mode power spectrum by 1-10%, with ell~10^3$ and z_s~1 being of
particular interest to weak lensing cosmology. Therefore the SLC is a severe
systematic for cosmology in Stage-IV lensing surveys. We present useful scaling
relations to self-calibrate the SLC effect. |
MUSE observations of the lensing cluster SMACSJ2031.8-4036: new
constraints on the mass distribution in the cluster core: We present new observations of the lensing cluster SMACSJ2031.8-4036 obtained
with the MUSE integral field spectrograph as part of its commissioning on the
Very Large Telescope. By providing medium-resolution spectroscopy over the full
4750-9350 Angstroms domain and a 1x1 arcmin2 field of view, MUSE is ideally
suited for identifying lensed galaxies in the cluster core, in particular
multiple-imaged systems. We perform a redshift analysis of all sources in the
datacube and identify a total of 12 systems ranging from $z=1.46$ to $z=6.4$,
with all images of each system confirmed by a spectroscopic redshift. This
allows us to accurately constrain the cluster mass profile in this region. We
foresee that future MUSE observations of cluster cores should help us discover
very faint Lyman-alpha emitters thanks to the strong magnification and the high
sensitivity of this instrument. | Effect of neutrino rest mass on ionization equilibrium freeze-out: We discuss how small neutrino rest masses can increase the expansion rate
near the photon decoupling epoch in the early universe, causing an earlier,
higher temperature freeze-out for ionization equilibrium compared to the
massless neutrino case. This yields a larger free-electron fraction. A larger
ratio of the sound horizon to the photon diffusion length follows, implying a
smaller inferred Neff. This neutrino-mass/recombination effect depends strongly
on the neutrino rest masses. Though below current sensitivity, this effect
could be probed by next-generation cosmic microwave background experiments,
giving an observational handle of neutrino mass physics. |
Panchromatic spectral energy distributions of Herschel sources: (abridged) Far-infrared Herschel photometry from the PEP and HerMES programs
is combined with ancillary datasets in the GOODS-N, GOODS-S, and COSMOS fields.
Based on this rich dataset, we reproduce the restframe UV to FIR ten-colors
distribution of galaxies using a superposition of multi-variate Gaussian modes.
The median SED of each mode is then fitted with a modified version of the
MAGPHYS code that combines stellar light, emission from dust heated by stars
and a possible warm dust contribution heated by an AGN. The defined Gaussian
grouping is also used to identify rare sources. The zoology of outliers
includes Herschel-detected ellipticals, very blue z~1 Ly-break galaxies,
quiescent spirals, and torus-dominated AGN with star formation. Out of these
groups and outliers, a new template library is assembled, consisting of 32 SEDs
describing the intrinsic scatter in the restframe UV-to-submm colors of
infrared galaxies. This library is tested against L(IR) estimates with and
without Herschel data included, and compared to eight other popular methods
often adopted in the literature. When implementing Herschel photometry, these
approaches produce L(IR) values consistent with each other within a median
absolute deviation of 10-20%, the scatter being dominated more by fine tuning
of the codes, rather than by the choice of SED templates. Finally, the library
is used to classify 24 micron detected sources in PEP GOODS fields. AGN appear
to be distributed in the stellar mass (M*) vs. star formation rate (SFR) space
along with all other galaxies, regardless of the amount of infrared luminosity
they are powering, with the tendency to lie on the high SFR side of the "main
sequence". The incidence of warmer star-forming sources grows for objects with
higher specific star formation rates (sSFR), and they tend to populate the
"off-sequence" region of the M*-SFR-z space. | Dynamics of a scalar field in Robertson-Walker spacetimes: We analyze the dynamics of a single scalar field in
Friedmann-Robertson-Walker universes with spatial curvature. We obtain the
fixed point solutions which are shown to be late time attractors. In
particular, we determine the corresponding scalar field potentials which
correspond to these stable solutions. The analysis is quite general and
incorporates expanding and contracting universes with both positive and
negative scalar potentials. We demonstrate that the known power law,
exponential, and de-Sitter solutions are certain limits of our general set of
solutions. |
ORIGAMI: Delineating Halos using Phase-Space Folds: We present the ORIGAMI method of identifying structures, particularly halos,
in cosmological N-body simulations. Structure formation can be thought of as
the folding of an initially flat three-dimensional manifold in six-dimensional
phase space. ORIGAMI finds the outer folds that delineate these structures.
Halo particles are identified as those that have undergone shell-crossing along
3 orthogonal axes, providing a dynamical definition of halo regions that is
independent of density. ORIGAMI also identifies other morphological structures:
particles that have undergone shell-crossing along 2, 1, or 0 orthogonal axes
correspond to filaments, walls, and voids respectively. We compare this method
to a standard Friends-of-Friends halo-finding algorithm and find that ORIGAMI
halos are somewhat larger, more diffuse, and less spherical, though the global
properties of ORIGAMI halos are in good agreement with other modern
halo-finding algorithms. | Photometric Redshifts and Systematic Variations in the SEDs of Luminous
Red Galaxies from the SDSS DR7: We describe the construction of a template set of spectral energy
distributions (SEDs) for the estimation of photometric redshifts of luminous
red galaxies (LRGs) with a Bayesian template fitting method. By examining the
color properties of several publicly available SED sets within a redshift range
of 0<z<0.5 and comparing them to SDSS DR7 data, we show that only some of the
investigated SEDs approximately match the colors of the LRG data throughout the
redshift range, however not at the quantitative level required for precise
photometric redshifts. We generate new SEDs by superposing model SEDs of
composite stellar populations with a burst model, allowing both components to
be reddened by dust, in order to match the data in five different redshift
bins. We select a set of SEDs which represents the LRG data in color space
within five redshift bins, thus defining our new SED template set for
photometric redshift estimates. The results we get with the new template set
and our Bayesian template fitting photometric redshift code (PhotoZ) are nearly
unbiased, with a scatter of \sigma(\Delta z)=0.027 (including outliers), and a
fraction of catastrophic outliers (|z_phot-z_spec|/(1+z_spec)>0.15) of 0.12%.
We show that templates that optimally describe the brightest galaxies
(-24.5<M_R<-22.7) indeed vary from z=0.1 to z=0.5, consistent with aging of the
stellar population. Furthermore, we find that templates that optimally describe
galaxies at z<0.1 strongly differ as a function of the absolute magnitude of
the galaxies, indicating an increase in star formation activity for less
luminous galaxies. Our findings based on the photometry of the SDSS LRGs and
our SED template fitting are supported by comparison to the average SDSS LRG
spectra in different luminosity and redshift bins. |
The Three Hundred Project: correcting for the hydrostatic-equilibrium
mass bias in X-ray and SZ surveys: Accurate and precise measurements of masses of galaxy clusters are key to
derive robust constraints on cosmological parameters. Rising evidence from
observations, however, confirms that X-ray masses, obtained under the
assumption of hydrostatic equilibrium, might be underestimated, as previously
predicted by cosmological simulations.
We analyse more than 300 simulated massive clusters, from `The Three Hundred
Project', and investigate the connection between mass bias and several
diagnostics extracted from synthetic X-ray images of these simulated clusters.
We find that the azimuthal scatter measured in 12 sectors of the X-ray flux
maps is a statistically significant indication of the presence of an intrinsic
(i.e. 3D) clumpy gas distribution. We verify that a robust correction to the
hydrostatic mass bias can be inferred when estimates of the gas inhomogeneity
from X-ray maps (such as the azimuthal scatter or the gas ellipticity) are
combined with the asymptotic external slope of the gas density or pressure
profiles, which can be respectively derived from X-ray and millimetric
(Sunyaev-Zeldovich effect) observations.
We also obtain that mass measurements based on either gas density and
temperature or gas density and pressure result in similar distributions of the
mass bias. In both cases, we provide corrections that help reduce both the
dispersion and skewness of the mass bias distribution. These are effective even
when irregular clusters are included leading to interesting implications for
the modelling and correction of hydrostatic mass bias in cosmological analyses
of current and future X-ray and SZ cluster surveys. | A Bayesian Approach to Gravitational Lens Model Selection, SF2A
proceeding: Over the past decade advancements in the understanding of several
astrophysical phenomena have allowed us to infer a concordance cosmological
model that successfully accounts for most of the observations of our universe.
This has opened up the way to studies that aim to better determine the
constants of the model and confront its predictions with those of competing
scenarios. Here, we use strong gravitational lenses as cosmological probes.
Strong lensing, as opposed to weak lensing, produces multiple images of a
single source. Extracting cosmologically relevant information requires accurate
modeling of the lens mass distribution, the latter being a galaxy or a cluster.
To this purpose a variety of models are available, but it is hard to
distinguish between them, as the choice is mostly guided by the quality of the
fit to the data without accounting for the number of additional parameters
introduced. However, this is a model selection problem rather than one of
parameter fitting that we address in the Bayesian framework. Using simple test
cases, we show that the assumption of more complicate lens models may not be
justified given the level of accuracy of the data. |
Shining Light on Merging Galaxies I: The Ongoing Merger of a Quasar with
a `Green Valley' Galaxy: Serendipitous observations of a pair z = 0.37 interacting galaxies (one
hosting a quasar) show a massive gaseous bridge of material connecting the two
objects. This bridge is photoionized by the quasar (QSO) revealing gas along
the entire projected 38 kpc sightline connecting the two galaxies. The emission
lines that result give an unprecedented opportunity to study the merger process
at this redshift. We determine the kinematics, ionization parameter (log U ~
-2.5 +- 0.03), column density (N_H ~ 10^{21} cm^{-2}), metallicity ([M/H] ~
-0.20 +- 0.15), and mass (~ 10^8 Msun) of the gaseous bridge. We simultaneously
constrain properties of the QSO-host (M_DM>8.8x 10^{11} Msun) and its companion
galaxy (M_DM>2.1 x 10^{11} Msun; M_star ~ 2 x 10^{10} Msun; stellar burst
age=300-800 Myr; SFR~6 Msun/yr; and metallicity 12+log (O/H)= 8.64 +- 0.2). The
general properties of this system match the standard paradigm of a
galaxy-galaxy merger caught between first and second passage while one of the
galaxies hosts an active quasar. The companion galaxy lies in the so-called
`green valley', with a stellar population consistent with a recent starburst
triggered during the first passage of the merger and has no detectable AGN
activity. In addition to providing case-studies of quasars associated with
galaxy mergers, quasar/galaxy pairs with QSO-photoionized tidal bridges such as
this one offer unique insights into the galaxy properties while also
distinguishing an important and inadequately understood phase of galaxy
evolution. | Optical Spectroscopy of Distant Red Galaxies: We present optical spectroscopic follow-up of a sample of Distant Red
Galaxies (DRGs) with K < 22.5 (Vega), selected by J-K > 2.3, in the Hubble Deep
Field South, the MS 1054-03 field, and the Chandra Deep Field South.
Spectroscopic redshifts were obtained for 15 DRGs. Only 2 out of 15 DRGs are
located at z < 2, suggesting a high efficiency to select high-redshift sources.
From other spectroscopic surveys in the CDFS targeting intermediate to high
redshift populations selected with different criteria, we find spectroscopic
redshifts for a further 30 DRGs. We use the sample of spectroscopically
confirmed DRGs to establish the high quality (scatter in \Delta z/(1+z) of ~
0.05) of their photometric redshifts in the considered deep fields, as derived
with EAZY (Brammer et al. 2008). Combining the spectroscopic and photometric
redshifts, we find that 74% of DRGs with K < 22.5 lie at z > 2. The combined
spectroscopic and photometric sample is used to analyze the distinct intrinsic
and observed properties of DRGs at z < 2 and z > 2. In our photometric sample
to K < 22.5, low-redshift DRGs are brighter in K than high-redshift DRGs by 0.7
mag, and more extincted by 1.2 mag in Av. Our analysis shows that the DRG
criterion selects galaxies with different properties at different redshifts.
Such biases can be largely avoided by selecting galaxies based on their
rest-frame properties, which requires very good multi-band photometry and high
quality photometric redshifts. |
The Pantheon+ Analysis: The Full Dataset and Light-Curve Release: Here we present 1701 light curves of 1550 spectroscopically confirmed Type Ia
supernovae (SNe Ia) that will be used to infer cosmological parameters as part
of the Pantheon+ SN analysis and the SH0ES (Supernovae and H0 for the Equation
of State of dark energy) distance-ladder analysis. This effort is one part of a
series of works that perform an extensive review of redshifts, peculiar
velocities, photometric calibration, and intrinsic-scatter models of SNe Ia.
The total number of light curves, which are compiled across 18 different
surveys, is a significant increase from the first Pantheon analysis (1048 SNe),
particularly at low redshift ($z$). Furthermore, unlike in the Pantheon
analysis, we include light curves for SNe with $z<0.01$ such that SN systematic
covariance can be included in a joint measurement of the Hubble constant
(H$_0$) and the dark energy equation-of-state parameter ($w$). We use the large
sample to compare properties of 151 SNe Ia observed by multiple surveys and 12
pairs/triplets of "SN siblings" - SNe found in the same host galaxy. Distance
measurements, application of bias corrections, and inference of cosmological
parameters are discussed in the companion paper by Brout et al. (2022b), and
the determination of H$_0$ is discussed by Riess et al. (2022). These analyses
will measure w with $\sim3\%$ precision and H$_0$ with 1 km/s/Mpc precision. | Constraining the luminosity function of faint undetected i-dropout
galaxies: We present a new technique to quantify the light contribution coming from the
faint high redshift ($z\sim6$) galaxies below the detection threshold of
imaging data, set conventionally at S/N=4.5. We illustrate the technique with
an application to Hubble Space Telescope Advanced Camera for Surveys images in
the F775W and F850LP filters of the Ultra Deep Field parallel field NICP12. The
aim of this analysis is to extend by a few magnitudes the faint end of the
luminosity function at $z\sim6$. After masking all the detected sources in the
field we apply a Fast Fourier Transform to obtain the spatial power spectrum of
the background signal. The power spectrum permits us to separate the background
noise signal, the residuals due to the data reduction of the wide field, and
the overall signal produced by faint galaxies. The ratio of the signal in the
i_775 and z_850 bands is used to estimate the contribution of the faint
i-dropout objects. We rely on extensive Monte Carlo simulations to characterize
various sources of uncertainty and quantify the number of faint i-dropout
galaxies in the field. The analysis allows us to put constraints on the
luminosity function at $z\sim6$ down to z_850= 30 mag, 2.5 mag fainter than
with standard techniques on the same data. The data are consistent with a faint
end slope of the luminosity function of $\alpha = -1.9$. Assuming a specific
set of values for the clumping factor, escape fraction, and spectral energy
distribution, we find that the $z\sim6$ undetected galaxies down to z_850=30
mag could have driven cosmic reionization. |
Quasi-spherical collapse of matter in $Λ$CDM: We report the findings of new exact analytical solutions to the cosmological
fluid equations, namely for the case where the initial conditions are
perturbatively close to a spherical top-hat profile. To do so we enable a fluid
description in a Lagrangian-coordinates approach, and prove the convergence of
the Taylor-series representation of the Lagrangian displacement field until the
time of collapse ("shell-crossing"). This allows the determination of the time
for quasi-spherical collapse, which is shown to happen generically earlier than
in the spherical case. For pedagogical reasons, calculations are first given
for a spatially flat universe that is only filled with a non-relativistic
component of cold dark matter (CDM). Then, the methodology is updated to a
$\Lambda$CDM Universe, with the inclusion of a cosmological constant
$\Lambda>0$. | Bounce and cyclic cosmology in extended nonlinear massive gravity: We investigate non-singular bounce and cyclic cosmological evolutions in a
universe governed by the extended nonlinear massive gravity, in which the
graviton mass is promoted to a scalar-field potential. The extra freedom of the
theory can lead to certain energy conditions violations and drive cyclicity
with two different mechanisms: either with a suitably chosen scalar-field
potential under a given Stuckelberg-scalar function, or with a suitably chosen
Stuckelberg-scalar function under a given scalar-field potential. Our analysis
shows that extended nonlinear massive gravity can alter significantly the
evolution of the universe at both early and late times. |
Generalized Holographic Dark Energy and its Observational Constraints: In the original holographic dark energy (HDE) model, the dark energy density
is proposed to be $\rho_{de} = 3c^2M^2_{pl}L^{-2}$, with $c$ is a dimensionless
constant characterizing the properties of the HDE. In this work, we propose the
generalized holographic dark energy (GHDE) model by considering the parameter
$c$ as a redshift-dependent function $c(z)$. We derive all the physical
quantities of the GHDE model analytically, and fit the $c(z)$ by trying four
kinds of parametrizations. The cosmological constraints of the $c(z)$ are
obtained from the joint analysis of the present SNLS3+BAO+CMB+$H_0$ data. We
find that, compared with the original HDE model, the GHDE models can provide a
better fit to the data. For example, the GHDE model with JBP-type $c(z)$ can
reduce the $\chi^2_{min}$ of the HDE model by 2.16. We also find that, unlike
the original HDE model with a phantom-like behavior in the future, the GHDE
models can present many more different possibilities, i.e., it allows the GHDE
in the future to be either quintessence like, cosmological constant like, or
phantom like, depending on the forms of $c(z)$. | Stability of small-scale baryon perturbations during cosmological
recombination: In this paper, we study small-scale fluctuations (baryon pressure sound
waves) in the baryon fluid during recombination. In particular, we look at
their evolution in the presence of relative velocities between baryons and
photons on large scales ($k \sim 10^{-1} \ {\rm Mpc}^{-1}$), which are
naturally present during the era of decoupling. Previous work concluded that
the fluctuations grow due to an instability of sound waves in a recombining
plasma, but that the growth factor is small for typical cosmological models.
These analyses model recombination in an inhomogenous universe as a
perturbation to the parameters of the homogenous solution. We show that for
relevant wavenumbers $k\gtrsim 10^3\ {\rm Mpc}^{-1}$ the dynamics are
significantly altered by the transport of both ionizing continuum ($h\nu>13.6$
eV) and Lyman-$\alpha$ photons between crests and troughs of the density
perturbations. We solve the radiative transfer of photons in both these
frequency ranges and incorporate the results in a perturbed three-level atom
model. We conclude that the instability persists at intermediate scales. We use
the results to estimate a distribution of growth rates in $10^{7}$ random
realizations of large-scale relative velocities. Our results indicate that
there is no appreciable growth; out of these $10^7$ realizations, the maximum
growth factor we find is less than $\approx 1.2$ at wavenumbers of $k \approx
10^{3} \ {\rm Mpc}^{-1}$. The instability's low growth factors are due to the
relatively short duration of the recombination epoch during which the electrons
and photons are coupled. |
The Evolution of Lyman Limit Absorption Systems to Redshift Six: We have measured the redshift evolution of the density of Lyman limit systems
(LLS) in the intergalactic medium over the redshift range 0 < z < 6. We have
used two new quasar samples to (1) improve coverage at z ~ 1, with GALEX grism
spectrograph observations of 50 quasars with 0.8 < z_em < 1.3, and (2) extend
coverage to z ~ 6, with Keck ESI spectra of 25 quasars with 4.17 < z_em < 5.99.
Using these samples together with published data, we find that the number
density of LLS per unit redshift, n(z), can be well fit by a simple evolution
of the form n(z) = n_3.5 [(1+z)/4.5]^gamma, with n_3.5 = 2.80 +/- 0.33 and
gamma = 1.94^(+0.36)_(-0.32) for the entire range 0 < z < 6. We have also
reanalyzed the evolution of damped Lyman alpha systems (DLAs) in the redshift
range 4 < z < 5 using our high-redshift quasar sample. We find a total of 17
DLAs and sub-DLAs, which we have analyzed in combination with published data.
The DLAs with log (HI column density) > 20.3 show the same redshift evolution
as the LLS. When combined with previous results, our DLA sample is also
consistent with a constant Omega_DLA= 9 x 10^(-4) from z = 2 to z = 5. We have
used the LLS number density evolution to compute the evolution in the mean free
path of ionizing photons. We find a smooth evolution to z ~ 6, very similar in
shape to that of Madau, Haardt & Rees (1999) but about a factor of two higher.
Recent theoretical models roughly match to the z < 6 data but diverge from the
measured power law at z > 6 in different ways, cautioning against extrapolating
the fit to the mean free path outside the measured redshift range. | Dynamical Structure of the Molecular Interstellar Medium in an Extremely
Bright, Multiply Lensed z~3 Submillimeter Galaxy Discovered with Herschel: We report the detection of CO 5-4, 3-2, and 1-0 emission in the strongly
lensed, Herschel/SPIRE-selected submillimeter galaxy (SMG) HLSW-01 at
z=2.9574+/-0.0001, using the Plateau de Bure Interferometer, the Combined Array
for Research in Millimeter-wave Astronomy, and the Green Bank Telescope. The
observations spatially resolve the molecular gas into four lensed images with a
maximum separation of ~9", and reveal the internal gas dynamics in this system.
We derive lensing-corrected CO line luminosities of L'(CO 1-0) = (4.17+/-0.41),
L'(CO 3-2) = (3.96+/-0.20) and L'(CO 5-4) = (3.45+/-0.20) x 10^10
(mu_L/10.9)^-1 Kkm/s pc^2, corresponding to luminosity ratios of r_31 =
0.95+/-0.10, r_53 = 0.87+/-0.06, and r_51 = 0.83+/-0.09. This suggests a total
molecular gas mass of Mgas = 3.3 x 10^10 (alpha_CO/0.8) (mu_L/10.9)^-1 Msun.
The gas mass, gas mass fraction, gas depletion timescale, star formation
efficiency, and specific star formation rate are typical for an SMG. The
velocity structure of the gas reservoir suggests that the brightest two lensed
images are dynamically resolved projections of the same dust-obscured region in
the galaxy that are kinematically offset from the unresolved fainter images.
The resolved kinematics appear consistent with the complex velocity structure
observed in major, `wet' (i.e., gas-rich) mergers. Major mergers are commonly
observed in SMGs, and are likely to be responsible for fueling their intense
starbursts at high gas consumption rates. This study demonstrates the level of
detail to which galaxies in the early universe can be studied by utilizing the
increase in effective spatial resolution and sensitivity provided by
gravitational lensing. |
Cosmological data favor Galileon ghost condensate over $Λ$CDM: We place observational constraints on the Galileon ghost condensate model, a
dark energy proposal in cubic-order Horndeski theories consistent with the
gravitational-wave event GW170817. The model extends the covariant Galileon by
taking an additional higher-order field derivative $X^2$ into account. This
allows for the dark energy equation of state $w_{\rm DE}$ to access the region
$-2<w_{\rm DE}<-1$ without ghosts. Indeed, this peculiar evolution of $w_{\rm
DE}$ is favored over that of the cosmological constant $\Lambda$ from the joint
data analysis of cosmic microwave background (CMB) radiation, baryonic acoustic
oscillations (BAOs), supernovae type Ia (SNIa) and redshift-space distortions
(RSDs). Furthermore, our model exhibits a better compatibility with the CMB
data over the $\Lambda$-cold-dark-matter ($\Lambda$CDM) model by suppressing
large-scale temperature anisotropies. The CMB temperature and polarization data
lead to an estimation for today's Hubble parameter $H_0$ consistent with its
direct measurements at 2$\sigma$. We perform a model selection analysis by
using several methods and find a statistically significant preference of the
Galileon ghost condensate model over $\Lambda$CDM. | The remnants of galaxy formation from a panoramic survey of the region
around M31: In hierarchical cosmological models, galaxies grow in mass through the
continual accretion of smaller ones. The tidal disruption of these systems is
expected to result in loosely bound stars surrounding the galaxy, at distances
that reach $10 - 100$ times the radius of the central disk. The number,
luminosity and morphology of the relics of this process provide significant
clues to galaxy formation history, but obtaining a comprehensive survey of
these components is difficult because of their intrinsic faintness and vast
extent. Here we report a panoramic survey of the Andromeda galaxy (M31). We
detect stars and coherent structures that are almost certainly remnants of
dwarf galaxies destroyed by the tidal field of M31. An improved census of their
surviving counterparts implies that three-quarters of M31's satellites brighter
than $M_V < -6$ await discovery. The brightest companion, Triangulum (M33), is
surrounded by a stellar structure that provides persuasive evidence for a
recent encounter with M31. This panorama of galaxy structure directly confirms
the basic tenets of the hierarchical galaxy formation model and reveals the
shared history of M31 and M33 in the unceasing build-up of galaxies. |
On the estimation of gravitational wave spectrum from cosmic domain
walls: We revisit the production of gravitational waves from unstable domain walls
analyzing their spectrum by the use of field theoretic lattice simulations with
grid size $1024^3$, which is larger than the previous study. We have recognized
that there exists an error in the code used in the previous study, and the
correction of the error leads to the suppression of the spectrum of
gravitational waves at high frequencies. The peak of the spectrum is located at
the scale corresponding to the Hubble radius at the time of the decay of domain
walls, and its amplitude is consistent with the naive estimation based on the
quadrupole formula. Using the numerical results, the magnitude and the peak
frequency of gravitational waves at the present time are estimated. It is shown
that for some choices of parameters the signal of gravitational waves is strong
enough to be probed in the future gravitational wave experiments. | Revisiting Metastable Dark Energy and Tensions in the Estimation of
Cosmological Parameters: We investigate constraints on some key cosmological parameters by confronting
metastable dark energy models with different combinations of the most recent
cosmological observations. Along with the standard $\Lambda$CDM model, two
phenomenological metastable dark energy models are considered: (\romannumeral1)
DE decays exponentially, (\romannumeral2) DE decays into dark matter. We find
that: (1) when considering the most recent supernovae and BAO data, and
assuming a fiducial $\Lambda$CDM model, the inconsistency in the estimated
value of the $\Omega_{\rm{m,0}}h^2$ parameter obtained by either including or
excluding Planck CMB data becomes very much substantial and points to a clear
tension~\citep{sahni2014model,zhao2017dynamical}; (2) although the two
metastable dark energy models that we study provide greater flexibility in
fitting the data, and they indeed fit the SNe Ia+BAO data substantially better
than $\Lambda$CDM, they are not able to alleviate this tension significantly
when CMB data are included; (3) while local measurements of the Hubble constant
are significantly higher relative to the estimated value of $H_0$ in our models
(obtained by fitting to SNe Ia and BAO data), the situation seems to be rather
complicated with hints of inconsistency among different observational data sets
(CMB, SNe Ia+BAO and local $H_0$ measurements). Our results indicate that we
might not be able to remove the current tensions among different cosmological
observations by considering simple modifications of the standard model or by
introducing minimal dark energy models. A complicated form of expansion
history, different systematics in different data and/or a non-conventional
model of the early Universe might be responsible for these tensions. |
The simplest parametrization of equation of state parameter in the
scalar field Universe: In this paper, we have investigated a scalar field cosmological model of
accelerating Universe with the simplest parametrization of equation of state
parameter of the scalar field. We used $H(z)$ data, pantheon compilation of SN
Ia data and BAO data to constrained the model parameters using $\chi^{2}$
minimization technique. We obtain the present values of Hubble constant $H_{0}$
as $66.2^{+1.42}_{-1.34}$, $70.7^{+0.32}_{-0.31}$ and $67.74^{+1.24}_{-1.04}$
for $H(z)$, $H(z)$ + Pantheon and $H(z)$ + BAO respectively. Also, we have
estimated the present age of the Universe in derived model $t_{0} =
14.38^{+0.63}_{-0.64}$ for joint $H(z)$ and pantheon compilation of SN Ia data
which has only $0.88~\sigma$ tension with its empirical value obtained in Plank
collaboration \cite{Ade/2016}. Moreover, the present values of the deceleration
parameter $q_{0}$ come out to be $-0.55^{+0.031}_{-0.038}$,
$-0.61^{+0.030}_{-0.021}$ and $-0.627^{+0.022}_{-0.025}$ by bounding the
Universe in derived model with $H(z)$, $H(z)$ + Pantheon compilation of SN Ia
and $H(z)$ + BAO data sets respectively. We also have performed the
state-finder diagnostics to discover the nature of dark energy. | Cosmological magnetic braking and the formation of high-redshift,
super-massive black holes: We study the effect of magnetic braking due to a primordial magnetic field in
the context of the formation of massive ($\gtrsim 10^{4} M_\odot$) direct
collapse black holes (DCBHs) at high redshifts. Under the assumption of axial
symmetry, we analytically compute the effect of magnetic braking on the angular
momentum of gas collapsing into the potential well of massive dark matter
haloes ($\simeq 10^{7-9} M_\odot$) which are spun up by gravitational tidal
torques. We find that a primordial magnetic field of strength $B_0\simeq
0.1$~nG (comoving) can remove the initial angular momentum gained by the
in-falling gas due to tidal torques, thus significantly lowering the angular
momentum barrier to the formation of DCBHs. These magnetic field strengths are
consistent with the bounds on primordial fields from astrophysical and
cosmological measurements and they are large enough to seed observed galactic
magnetic fields. |
Constraints on Cosmographic Functions of Cosmic Chronometers Data Using
Gaussian Processes: We study observational constraints on the cosmographic functions up to the
fourth derivative of the scale factor with respect to cosmic time, i.e., the
so-called snap function, using the non-parametric method of Gaussian Processes.
As observational data we use the Hubble parameter data. Also we use mock data
sets to estimate the future forecast and study the performance of this type of
data to constrain cosmographic functions. The combination between a
non-parametric method and the Hubble parameter data is investigated as a
strategy to reconstruct cosmographic functions. In addition, our results are
quite general because they are not restricted to a specific type of functional
dependency of the Hubble parameter. We investigate some advantages of using
cosmographic functions instead of cosmographic series, since the former are
general definitions free of approximations. In general, our results do not
deviate significantly from $\Lambda CDM$. We determine a transition redshift
$z_{tr}=0.637^{+0.165}_{-0.175}$ and $H_{0}=69.45 \pm 4.34$. Also assuming
priors for the Hubble constant we obtain $z_{tr}=0.670^{+0.210}_{-0.120}$ with
$H_{0}=67.44$ (Planck) and $z_{tr}=0.710^{+0.159}_{-0.111}$ with
$H_{0}=74.03$(SH0ES). Our main results are summarized in table 2. | Non-Gaussianity in D3-brane inflation: We update predictions for observables in the "delicate" D3/anti-D3
inflationary model on the conifold. We use a full CMB likelihood calculation to
assess goodness-of-fit, which is necessary because in this model the zeta power
spectrum often cannot be modelled as a power-law over observable scales. For
the first time we are able to provide accurate forecasts for the amplitude of
three-point correlations. In a significant portion of its parameter space the
model follows Maldacena's single-field prediction fNL ~ -(5/12)(ns-1) if nt <<
1. Therefore |fNL| is usually small when the power spectrum satisfies
observational constraints. In a small number of cases the bispectrum is instead
dominated by effects from rapid switching between angular minima. The resulting
amplitudes are larger, but mostly with unacceptable spectral behaviour. In the
most extreme case we obtain |fNLeq| ~ 75 at kt/3 = 0.002/Mpc. It has been
suggested that the quasi-single field inflation ("QSFI") mechanism could
produce significant 3-point correlations in this model. We do observe rare
shifts in amplitude between equilateral and squeezed configurations that could
possibly be associated with QSFI effects, but more investigation is needed to
establish the full bispectrum shape. There is evidence of "shape" running
between equilateral and squeezed configurations that may be inherited from the
scale dependence of the spectrum. We explore the dependence of observables on
discrete choices such as the truncation point of the potential. Our analysis
illustrates the advantages of a standard format for information exchange within
the inflationary model-building and testing community. |
Numerical and Perturbative Computations of the Fuzzy Dark Matter Model: We investigate nonlinear structure formation in the fuzzy dark matter (FDM)
model using both numerical and perturbative techniques. On the numerical side,
we examine the virtues and limitations of a Schrodinger-Poisson solver (wave
formulation) versus a fluid dynamics solver (Madelung formulation). We also
carry out a perturbative computation of the one-loop mass power spectrum. We
find that (1) in many cases, the fluid dynamics solver is capable of producing
the expected interference patterns, but it fails where destructive interference
causes the density to vanish which generally occurs in the nonlinear regime.
(2) The Schrodinger-Poisson solver works well in all test cases, but it is
demanding in resolution: one must resolve the small de Broglie scale to obtain
the correct dynamics on large scales. (3) We compare the mass power spectrum
from perturbation theory against that from the Schrodinger-Poisson solver, and
find good agreement in the mildly nonlinear regime. Compared with fluid
perturbation theory, wave perturbation theory has a more limited range of
validity. (4) As an application, we compare the Lyman-alpha forest flux power
spectrum obtained from the Schrodinger-Poisson solver versus one from an N-body
simulation (which is often used as an approximate method to make predictions
for FDM). At redshift 5, the two, starting from the same initial condition,
agree to better than 10 % on observationally relevant scales as long as the FDM
mass exceeds $2 \times 10^{-23}$ eV. | Geometries with integrable singularity -- black/white holes and
astrogenic universes: We briefly review the problem of generating cosmological flows of matter in
GR (the genesis of universes), analyze models' shortcomings and their basic
assumptions yet to be justified in physical cosmology. We propose a paradigm of
cosmogenesis based on the class of spherically symmetric solutions with {\it
integrable} singularity $r=0$. They allow for geodesically complete geometries
of black/white holes, which may comprise space-time regions with properties of
cosmological flows. |
Herschel-ATLAS: a binary HyLIRG pinpointing a cluster of starbursting
proto-ellipticals: Panchromatic observations of the best candidate HyLIRG from the widest
Herschel extragalactic imaging survey have led to the discovery of at least
four intrinsically luminous z=2.41 galaxies across a ~100-kpc region - a
cluster of starbursting proto-ellipticals. Via sub-arcsecond interferometric
imaging we have measured accurate gas and star-formation surface densities. The
two brightest galaxies span ~3 kpc FWHM in submm/radio continuum and CO J=4-3,
and double that in CO J=1-0. The broad CO line is due partly to the multitude
of constituent galaxies and partly to large rotational velocities in two
counter-rotating gas disks -- a scenario predicted to lead to the most intense
starbursts, which will therefore come in pairs. The disks have M(dyn) of
several x 10^11 Msun, and gas fractions of ~40%. Velocity dispersions are
modest so the disks are unstable, potentially on scales commensurate with their
radii: these galaxies are undergoing extreme bursts of star formation, not
confined to their nuclei, at close to the Eddington limit. Their specific
star-formation rates place them ~>5x above the main sequence, which supposedly
comprises large gas disks like these. Their high star-formation efficiencies
are difficult to reconcile with a simple volumetric star-formation law. N-body
and dark matter simulations suggest this system is the progenitor of a
B(inary)-type ~10^14.6-Msun cluster. | Quasar-Lyman $α$ Forest Cross-Correlation from BOSS DR11 : Baryon
Acoustic Oscillations: We measure the large-scale cross-correlation of quasars with the Lyman alpha
forest absorption, using over 164,000 quasars from Data Release 11 of the
SDSS-III Baryon Oscillation Spectroscopic Survey. We extend the previous study
of roughly 60,000 quasars from Data Release 9 to larger separations, allowing a
measurement of the Baryonic Acoustic Oscillation (BAO) scale along the line of
sight $c/(H(z=2.36) ~ r_s) = 9.0 \pm 0.3$ and across the line of sight
$D_A(z=2.36) / ~ r_s = 10.8 \pm 0.4$, consistent with CMB and other BAO data.
Using the best fit value of the sound horizon from Planck data ($r_s=147.49
Mpc$), we can translate these results to a measurement of the Hubble parameter
of $H(z=2.36) = 226 \pm 8 km/s / Mpc$ and of the angular diameter distance of
$D_A(z=2.36) = 1590 \pm 60 Mpc$. The measured cross-correlation function and an
update of the code to fit the BAO scale (baofit) are made publicly available. |
A Measurement of Gravitational Lensing of the Cosmic Microwave
Background by Galaxy Clusters Using Data from the South Pole Telescope: Clusters of galaxies are expected to gravitationally lens the cosmic
microwave background (CMB) and thereby generate a distinct signal in the CMB on
arcminute scales. Measurements of this effect can be used to constrain the
masses of galaxy clusters with CMB data alone. Here we present a measurement of
lensing of the CMB by galaxy clusters using data from the South Pole Telescope
(SPT). We develop a maximum likelihood approach to extract the CMB cluster
lensing signal and validate the method on mock data. We quantify the effects on
our analysis of several potential sources of systematic error and find that
they generally act to reduce the best-fit cluster mass. It is estimated that
this bias to lower cluster mass is roughly $0.85\sigma$ in units of the
statistical error bar, although this estimate should be viewed as an upper
limit. We apply our maximum likelihood technique to 513 clusters selected via
their SZ signatures in SPT data, and rule out the null hypothesis of no lensing
at $3.1\sigma$. The lensing-derived mass estimate for the full cluster sample
is consistent with that inferred from the SZ flux: $M_{200,\mathrm{lens}} =
0.83_{-0.37}^{+0.38}\, M_{200,\mathrm{SZ}}$ (68% C.L., statistical error only). | The Distribution and Evolution of Quasar Proximity Zone Sizes: In this paper, we study the sizes of quasar proximity zones with synthetic
quasar absorption spectra obtained by post-processing a Cosmic Reionization On
Computers (CROC) simulation. CROC simulations have both relatively large box
sizes and high spacial resolution, allowing us to resolve Lyman limit systems,
which are crucial for modeling the quasar absorption spectra. We find that
before reionization most quasar proximity zone sizes grow steadily for $\sim
10$ Myr, while after reionization they grow rapidly but only for $\sim 0.1$
Myr. We also find a slow growth of $R_{\rm obs}$ with decreasing turn-on
redshift. In addition, we find that $\sim 1-2\%$ of old quasars ($30$ Myr old)
display extremely small proximity zone sizes ($<1$ proper Mpc), of which the
vast majority are due to the occurrence of a damped Ly$\alpha$ absorber (DLA)
or a Lyman limit system (LLS) along the line of sight. These DLAs and LLSs are
contaminated with metal, which offers a way to distinguish them from the normal
proximity zones of young quasars. |
Building the cosmic infrared background brick by brick with Herschel/PEP: The cosmic infrared background (CIB) includes roughly half of the energy
radiated by all galaxies at all wavelengths across cosmic time, as observed at
the present epoch. The PACS Evolutionary Probe (PEP) survey is exploited here
to study the CIB and its redshift differential, at 70, 100 and 160 micron,
where the background peaks. Combining PACS observations of the GOODS-S,
GOODS-N, Lockman Hole and COSMOS areas, we define number counts spanning over
more than two orders of magnitude in flux: from ~1 mJy to few hundreds mJy.
Stacking of 24 micron sources and P(D) statistics extend the analysis down to
~0.2 mJy. Taking advantage of the wealth of ancillary data in PEP fields,
differential number counts and CIB are studied up to z=5. Based on these
counts, we discuss the effects of confusion on PACS blank field observations
and provide confusion limits for the three bands considered. The total CIB
surface brightness emitted above PEP 3 sigma flux limits is 4.52 +/- 1.18, 8.35
+/- 0.95 and 9.49 +/- 0.59 [nW/m2/sr] at 70, 100, and 160 micron, respectively.
These values correspond to 58 +/- 7% and 74 +/- 5% of the COBE/DIRBE CIB direct
measurements at 100 and 160 micron. Employing the P(D) analysis, these
fractions increase to ~65% and ~89%. More than half of the resolved CIB was
emitted at redshift z<=1. The 50%-light redshifts lie at z=0.58, 0.67 and 0.73
at the three PACS wavelengths. The distribution moves towards earlier epochs at
longer wavelengths: while the 70 micron CIB is mainly produced by z<=1.0
objects, the contribution of z>1.0 sources reaches 50% at 160 micron. Most of
the CIB resolved in the three PACS bands was emitted by galaxies with infrared
luminosities in the range 1e11-1e12 L(sun). | Exploring the Latest Pantheon SNIa Dataset by Using Three Kinds of
Statistics Techniques: In this work, we explore the cosmological consequences of the latest Type Ia
supernova (SN Ia) data-set, Pantheon, by adopting the $wCDM$ model. The
Pantheon data-set is the largest SN Ia samples till now, which contains 1048
supernovae on the redshift range $0 < z < 2.3$. Here we take into account three
kinds of SN Ia statistics techniques, including: 1. magnitude statistics (MS),
which is the traditional SN Ia statistics technique; 2. flux statistics (FS),
which bases on the flux-averaging (FA) method; 3. improved flux statistics
(IFS), which combines the advantages of MS and FS. It should be mentioned that,
The IFS technique need to scan the $(z_{cut},\Delta z)$ parameters plane, where
$z_{cut}$ and $\Delta z$ are redshift cut-off and redshift interval of FA,
respectively. The results are shown as follows. (1) Using SN data-set only, the
best FA recipe for IFS is $(z_{cut},\Delta z)=(0.1,0.08)$; (2) Comparing to the
old SN data-set, JLA, adopting Pantheon data-set can reduce the $2\sigma$ error
bars of equation of state $w$ by 38\%, 47\% and 53\% for MS, FS and IFS,
respectively; (3) FS gives closer results to other observations, such as Baryon
acoustic oscillations and Cosmic microwave background; (4) Compared with FS and
IFS, MS more favors a Universe that will end in a "big rip". |
Unified galaxy power spectrum measurements from 6dFGS, BOSS, and eBOSS: We make use of recent developments in the analysis of galaxy redshift surveys
to present an easy to use matrix-based analysis framework for the galaxy power
spectrum multipoles, including wide-angle effects and the survey window
function. We employ this framework to derive the deconvolved power spectrum
multipoles of 6dFGS DR3, BOSS DR12 and the eBOSS DR16 quasar sample. As an
alternative to the standard analysis, the deconvolved power spectrum multipoles
can be used to perform a data analysis agnostic of survey specific aspects,
like the window function. We show that in the case of the BOSS dataset, the
Baryon Acoustic Oscillation (BAO) analysis using the deconvolved power spectra
results in the same likelihood as the standard analysis. To facilitate the
analysis based on both the convolved and deconvolved power spectrum
measurements, we provide the window function matrices, wide-angle matrices,
covariance matrices and the power spectrum multipole measurements for the
datasets mentioned above. Together with this paper we publish a
\code{Python}-based toolbox to calculate the different analysis components. The
appendix contains a detailed user guide with examples for how a cosmological
analysis of these datasets could be implemented. We hope that our work makes
the analysis of galaxy survey datasets more accessible to the wider cosmology
community. | DNF - Galaxy photometric redshift by Directional Neighbourhood Fitting: Wide field images taken in several photometric bands allow simultaneous
measurement of redshifts for thousands of galaxies. A variety of algorithms to
make this measurement have appeared in the last few years, the majority of
which can be classified as either template or training based methods. Among the
latter, nearest neighbour estimatorsstand out as one of the most successful, in
terms of both precision and the quality of error estimation. In this paper we
describe the Directional Neighbourhood Fitting (DNF) algorithm based on the
following: a new neighbourhood metric (Directional Neighbourhood), a photo-z
estimation strategy (Neighbourhood Fitting) and a method for generating the
photo-z probability distribution function. We compare DNF with other well-known
empirical photometric redshift tools using different public datasets (Sloan
Digital Sky Survey, VIMOS VLT Deep Survey and Photo-z Accuracy Testing). DNF
achieves high-quality results with reliable error. |
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