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The bright galaxy population of five medium redshift clusters. II.
Quantitative Galaxy Morphology: Aims: Following the study already presented in our previous paper, based on
the Nordic Optical Telescope (NOT) sample, which consists of five clusters of
galaxies within the redshift range 0.18 $\leq$ z $\leq$ 0.25, imaged in the
central 0.5-2 Mpc in very good seeing conditions, we have studied the
quantitative morphology of their bright galaxy population
Methods: We have analyzed the surface brightness profiles of the galaxy
population in those clusters. Previously, we have performed simulations in
order to check the reliability of the fits. We have also derived a quantitative
morphological classification.
Results: The structural parameters derived from these analysis have been
analyzed. We have obtained that the structural parameters of E/S0 galaxies are
similar to those showed by galaxies in low redshift clusters. However, the disc
scales are different. In particular, the scales of the discs of galaxies at
medium redshift clusters are statistically different than those located in
similar galaxies in the Coma cluster. But, the scales of the discs of galaxies
in medium redshift clusters are similar to nearby field galaxies.
Conclusions: The results suggest that the evolution of the disc component of
galaxies in clusters is faster than in field ones. Mechanisms like galaxy
harassment showing timescales of $\sim 1$Gyr could be the responsible of this
disc scale evolution. This indicates that spiral galaxies in clusters have
suffered a strong evolution in the last 2.5 Gyr or that Coma is in some way
anomalous. | Sheer shear: weak lensing with one mode: 3D data compression techniques can be used to determine the natural basis of
radial eigenmodes that encode the maximum amount of information in a
tomographic large-scale structure survey. We explore the potential of the
Karhunen-Lo\`eve decomposition in reducing the dimensionality of the data
vector for cosmic shear measurements, and apply it to the final data from the
\cfh survey. We find that practically all of the cosmological information can
be encoded in one single radial eigenmode, from which we are able to reproduce
compatible constraints with those found in the fiducial tomographic analysis
(done with 7 redshift bins) with a factor of ~30 fewer datapoints. This
simplifies the problem of computing the two-point function covariance matrix
from mock catalogues by the same factor, or by a factor of ~800 for an
analytical covariance. The resulting set of radial eigenfunctions is close to
ell-independent, and therefore they can be used as redshift-dependent galaxy
weights. This simplifies the application of the Karhunen-Lo\`eve decomposition
to real-space and Fourier-space data, and allows one to explore the effective
radial window function of the principal eigenmodes as well as the associated
shear maps in order to identify potential systematics. We also apply the method
to extended parameter spaces and verify that additional information may be
gained by including a second mode to break parameter degeneracies. The data and
analysis code are publicly available at
https://github.com/emiliobellini/kl_sample. |
Measuring the primordial curvature perturbations from the scalar induced
gravitational waves: The scalar induced gravitational waves are produced from primordial curvature
perturbations in the second order of perturbations. We constrain the fractional
energy density of scalar induced gravitational waves from gravitational waves
observations. If there is no detection of the scalar induced gravitational
waves, the fractional energy density of scalar induced gravitational waves is
constrained by some upper limits. Depends on these upper limits, we can obtain
the constraints on the power spectrum of the primordial curvature
perturbations. For a power-law scalar power spectrum, the constraints on the
power spectrum are affected by adding the upper limit of scalar induced
gravitational waves from Square Kilometer Array (SKA). In the standard model,
the mean values of the scalar amplitude and the spectral index shift to lower
values when SKA is added to the combination of Cosmic Microwave Background
(CMB) and Baryon Acoustic Oscillation (BAO) datasets, namely
$\ln(10^{10}A_s)=3.038\pm0.013$ and $n_s=0.9589^{+0.0021}_{-0.0011}$ at $68\%$
confidence level. We also consider the effects of the existing ground-based
gravitational-wave detectors, the existing Pulsar Timing Arrays (PTAs) and
Five-hundred-meter Aperture Spherical radio Telescope (FAST), while the
constraints from CMB+BAO datasets are totally within their upper limits of
scalar induced gravitational waves. Furthermore, we characterize the scalar
fluctuation spectrum in terms of the spectral index $n_s$ and its first two
derivatives. We calculate corresponding power spectrum of scalar induced
gravitational waves theoretically and give the constraints on the running of
the spectral index and the running of the running of the spectral index. | Vindicating single-T modified blackbody fits to Herschel SEDs (Research
Note): I show here that the bulk of the dust mass in a galaxy can be equivalently
estimated from: i) the full spectral energy distribution of dust emission,
using the approach of Draine & Lee (2007) that includes a distribution of dust
grains and a range of interstellar radiation field intensities; ii) the
emission in the wavelength range 100um <= lambda <= 500um (covered by the
Herschel Space Observatory), by fitting to the data a simpler single
temperature modified blackbody. Recent claims on the contrary (Dale et al.
2012) should be interpreted as a caveat to use in the simpler fits an
absorption cross section which is consistent both in the normalization and in
the spectral index beta with that of the full dust model. I also show that the
dust mass does not depend significantly on the choice of beta, if both the dust
mass and the absorption cross section are derived with the same assumption on
beta. |
Globular cluster content and evolutionary history of NGC147: We present the results of spectroscopic observations of eight globular
cluster candidates in NGC147, a satellite dwarf elliptical galaxy of M31. Our
goal is to make a complete inventory of the globular cluster system of this
galaxy, determine the properties of their stellar populations, and compare
these properties with those of systems of globular clusters in other dwarf
galaxies. The candidates were identified on Canada-France-Hawaii telescope
photographic plates. Medium resolution spectra were obtained with the SCORPIO
spectrograph at the prime focus of the 6m telescope of the Russian Academy of
Sciences. We were able to confirm the nature of all eight candidates, three of
which (GC5, GC7, and GC10) are indeed globular clusters, and to estimate
evolutionary parameters for the two brightest ones and for Hodge II. The bright
clusters GC5 and GC7 appear to have metallicities ([Z/H]~ -1.5- -1.8) that are
lower than the oldest stars in the galaxy. The fainter GC Hodge II has a
metallicity [Z/H]=-1.1 dex, similar to that of the oldest stars in the galaxy.
The clusters GC5 and GC7 have low alpha-element abundance ratios. The mean age
of the globular clusters in NGC147 is 9+-1 Gyr. The frequency, S_n =6.4, and
mass fraction, T=14 of globular clusters in NGC147 appear to be higher than
those for NGC185 and 205. (Abridged) | Probing frequency-dependent half-wave plate systematics for CMB
experiments with full-sky beam convolution simulations: We study systematic effects from half-wave plates (HWPs) for cosmic microwave
background (CMB) experiments using full-sky time-domain beam convolution
simulations. Using an optical model for a fiducial spaceborne two-lens
refractor telescope, we investigate how different HWP configurations optimized
for dichroic detectors centred at 95 and 150 GHz impact the reconstruction of
primordial B-mode polarization. We pay particular attention to possible biases
arising from the interaction of frequency dependent HWP non-idealities with
polarized Galactic dust emission and the interaction between the HWP and the
instrumental beam. To produce these simulations, we have extended the
capabilities of the publicly available beamconv code. To our knowledge, we
produce the first time-domain simulations that include both HWP non-idealities
and realistic full-sky beam convolution. Our analysis shows how certain
achromatic HWP configurations produce significant systematic polarization angle
offsets that vary for sky components with different frequency dependence. Our
analysis also demonstrates that once we account for interactions with HWPs,
realistic beam models with non-negligible cross-polarization and sidelobes will
cause significant B-mode residuals that will have to be extensively modelled in
some cases. |
Primordial Black Holes from Inflation and Quantum Diffusion: Primordial black holes as dark matter may be generated in single-field models
of inflation thanks to the enhancement at small scales of the comoving
curvature perturbation. This mechanism requires leaving the slow-roll phase to
enter a non-attractor phase during which the inflaton travels across a plateau
and its velocity drops down exponentially. We argue that quantum diffusion has
a significant impact on the primordial black hole mass fraction making the
classical standard prediction not trustable. | Galaxy Clusters in the Line of Sight to Background Quasars - III
Multi-Object Spectroscopy: We present Gemini/GMOS-S multi-object spectroscopy of 31 galaxy cluster
candidates at redshifts between 0.2 and 1.0 and centered on QSO sight-lines
taken from Lopez et al. (2008). The targets were selected based on the presence
of a intervening MgII absorption system at a similar redshift to that of a
galaxy cluster candidate lying at a projected distance < 2 h^{-1}Mpc from the
QSO sight-line (a 'photometric-hit'). The absorption systems span rest-frame
equivalent widths between 0.015 and 2.028 angstroms. Our aim was 3-fold: 1)
identify the absorbing galaxies and determine their impact parameters, 2)
confirm the galaxy cluster candidates in the vicinity of each quasar sightline,
and 3) determine whether the absorbing galaxies reside in galaxy clusters. Our
main findings are: 1) the identification of 10 out of 24 absorbing galaxies
with redshifts up to 1.0955. 2) The spectroscopic confirmation of 20 out of 31
cluster/group candidates, with most of the confirmed clusters/groups at z <
0.7. 3) Following from the results above, the spectroscopic confirmation of 10
out of 14 photometric hits within ~ 650 km/s from galaxy clusters/groups, in
addition to 2 new ones related to galaxy group environments. These numbers
imply efficiencies of 71% in finding such systems with MOS spectroscopy. This
is a remarkable result since we defined a photometric hit as those
cluster-absorber pairs having a redshift difference dz = 0.1. Absorbing
cluster-galaxies hosting weak absorbers are consistent with lower star
formation activity than the rest, which produce strong absorption and agree
with typical MgII absorbing galaxies found in the literature. Our spectroscopic
confirmations lend support to the selection of photometric hits made in Lopez
et al. (2008). |
Cosmology from the Chinese Space Station Optical Survey (CSS-OS): The Chinese Space Station Optical Survey (CSS-OS) is a planned full sky
survey operated by the Chinese Space Station Telescope (CSST). It can
simultaneously perform the photometric imaging and spectroscopic slitless
surveys, and will probe weak and strong gravitational lensing, galaxy
clustering, individual galaxies and galaxy clusters, active galactic nucleus
(AGNs), and so on. It aims to explore the properties of dark matter and dark
energy and other important cosmological problems. In this work, we focus on two
main CSS-OS scientific goals, i.e. the weak gravitational lensing (WL) and
galaxy clustering surveys. We generate the mock CSS-OS data based on the
observational COSMOS and zCOSMOS catalogs. We investigate the constraints on
the cosmological parameters from the CSS-OS using the Markov Chain Monte Carlo
(MCMC) method. The intrinsic alignments, galaxy bias, velocity dispersion, and
systematics from instrumental effects in the CSST WL and galaxy clustering
surveys are also included, and their impacts on the constraint results are
discussed. We find that the CSS-OS can improve the constraints on the
cosmological parameters by a factor of a few (even one order of magnitude in
the optimistic case), compared to the current WL and galaxy clustering surveys.
The constraints can be further enhanced when performing joint analysis with the
WL, galaxy clustering, and galaxy-galaxy lensing data. Therefore, the CSS-OS is
expected to be a powerful survey for exploring the Universe. Since some
assumptions may be still optimistic and simple, it is possible that the results
from the real survey could be worse. We will study these issues in details with
the help of simulations in the future. | Weak lensing of the Lyman-alpha forest: The angular positions of quasars are deflected by the gravitational lensing
effect of foreground matter. The Lyman-alpha forest seen in the spectra of
these quasars is therefore also lensed. We propose that the signature of weak
gravitational lensing of the forest could be measured using similar techniques
that have been applied to the lensed Cosmic Microwave Background, and which
have also been proposed for application to spectral data from 21cm radio
telescopes. As with 21cm data, the forest has the advantage of spectral
information, potentially yielding many lensed "slices" at different redshifts.
We perform an illustrative idealized test, generating a high resolution angular
grid of quasars (of order arcminute separation), and lensing the
Lyman-alphaforest spectra at redshifts z=2-3 using a foreground density field.
We find that standard quadratic estimators can be used to reconstruct images of
the foreground mass distribution at z~1. There currently exists a wealth of Lya
forest data from quasar and galaxy spectral surveys, with smaller sightline
separations expected in the future. Lyman-alpha forest lensing is sensitive to
the foreground mass distribution at redshifts intermediate between CMB lensing
and galaxy shear, and avoids the difficulties of shape measurement associated
with the latter. With further refinement and application of mass reconstruction
techniques, weak gravitational lensing of the high redshift Lya forest may
become a useful new cosmological probe. |
The star formation histories of fossil group galaxies: A comparison is carried out among the star formation histories of early-type
galaxies (ETG) in fossil groups, clusters and low density environments.
Although they show similar evolutionary histories, a significant fraction of
the fossils are younger than their counterparts, suggesting that fossils can be
precursors of the isolated ETGs. | A natural boundary of dark matter haloes revealed around the minimum
bias and maximum infall locations: We explore the boundary of dark matter haloes through their bias and velocity
profiles. Using cosmological $N$-body simulations, we show that the bias
profile exhibits a ubiquitous trough that can be interpreted as created by halo
accretion that depletes material around the boundary. The inner edge of the
active depletion region is marked by the location of the maximum mass inflow
rate that separates a growing halo from the draining environment. This inner
depletion radius can also be interpreted as the radius enclosing a highly
complete population of splashback orbits, and matches the optimal exclusion
radius in a halo model of the large-scale structure. The minimum of the bias
trough defines a characteristic depletion radius, which is located within the
infall region bounded by the inner depletion radius and the turnaround radius,
while approaching the turnaround radius in low mass haloes that have stopped
mass accretion. The characteristic depletion radius depends the most on halo
mass and environment. It is approximately $2.5$ times the virial radius and
encloses an average density of $\sim 40$ times the background density of the
universe, independent on halo mass but dependent on other halo properties. The
inner depletion radius is smaller by $10-20\%$ and encloses an average density
of $\sim 63$ times the background density. These radii open a new window for
studying the properties of haloes. |
The mystery of the missing GRB redshifts: It is clear that optical selection effects have distorted the "true" GRB
redshift distribution to its presently observed biased distribution. We
constrain a statistically optimal model that implies GRB host galaxy dust
extinction could account for up to 40% of missing optical afterglows and
redshifts in $z = 0-3$, but the bias is negligible at very high-$z$. The
limiting sensitivity of the telescopes, and the time to acquire
spectroscopic/photometric redshifts, are significant sources of bias for the
very high-$z$ sample. We caution on constraining star formation rate and
luminosity evolution using the GRB redshift distribution without accounting for
these selection effects. | XMM-Newton RGS observation of the warm absorber in Mrk 279: The Seyfert 1 galaxy Mrk 279 was observed by XMM-Newton in November 2005 in
three consecutive orbits, showing significant short-scale variability (average
soft band variation in flux ~20%). The source is known to host a two-component
warm absorber with distinct ionisation states from a previous Chandra
observation. We aim to study the warm absorber in Mrk 279 and investigate any
possible response to the short-term variations of the ionising flux, and to
assess whether it has varied on a long-term time scale with respect to the
Chandra observation. We find no significant changes in the warm absorber on
neither short time scales (~2 days) nor at longer time scales (two and a half
years), as the variations in the ionic column densities of the most relevant
elements are below the 90% confidence level. The variations could still be
present but are statistically undetected given the signal-to-noise ratio of the
data. Starting from reasonable standard assumptions we estimate the location of
the absorbing gas, which is likely to be associated with the putative dusty
torus rather than with the Broad Line Region if the outflowing gas is moving at
the escape velocity or larger. |
Is the $H_0$ tension suggesting a 4th neutrino's generation?: Flavour oscillations experiments are suggesting the existence of a sterile,
$4$th neutrino's generation with a mass of an eV order. This would mean an
additional relativistic degree of freedom in the cosmic inventory, in
contradiction with recent results from the Planck satellite, that have
confirmed the standard value $N_{eff} \approx 3$ for the effective number of
relativistic species. On the other hand, the Planck best-fit for the
Hubble-Lema\^itre parameter is in tension with the local value determined with
the Hubble Space Telescope, and adjusting $N_{eff}$ is a possible way to
overcome such a tension. In this paper we perform a joint analysis of three
complementary cosmological distance rulers, namely the CMB acoustic scale
measured by Planck, the BAO scale model-independently determined by Verde {\it
et al.}, and luminosity distances measured with JLA and Pantheon SNe Ia
surveys. Two Gaussian priors were imposed to the analysis, the local expansion
rate measured by Riess {\it et al.}, and the baryon density parameter fixed
from primordial nucleosynthesis by Cooke {\it et al.}. For the sake of
generality, two different models are used in the tests, the standard
$\Lambda$CDM model and a generalised Chaplygin gas. The best-fit gives $N_{eff}
\approx 4$ in both models, with a Chaplygin gas parameter slightly negative,
$\alpha \approx -0.04$. The standard value $N_{eff} \approx 3$ is ruled out
with $\approx 3\sigma$. | The POINT-AGAPE Survey: Comparing Automated Searches of Microlensing
Events toward M31: Searching for microlensing in M31 using automated superpixel surveys raises a
number of difficulties which are not present in more conventional techniques.
Here we focus on the problem that the list of microlensing candidates is
sensitive to the selection criteria or "cuts" imposed and some subjectivity is
involved in this. Weakening the cuts will generate a longer list of
microlensing candidates but with a greater fraction of spurious ones;
strengthening the cuts will produce a shorter list but may exclude some genuine
events. We illustrate this by comparing three analyses of the same data-set
obtained from a 3-year observing run on the INT in La Palma. The results of two
of these analyses have been already reported: Belokurov et al. (2005) obtained
between 3 and 22 candidates, depending on the strength of their cuts, while
Calchi Novati et al. (2005) obtained 6 candidates. The third analysis is
presented here for the first time and reports 10 microlensing candidates, 7 of
which are new. Only two of the candidates are common to all three analyses. In
order to understand why these analyses produce different candidate lists, a
comparison is made of the cuts used by the three groups... |
BeyondPlanck XVI. Limits on Large-Scale Polarized Anomalous Microwave
Emission from Planck LFI and WMAP: We constrain the level of polarized anomalous microwave emission (AME) on
large angular scales using $\textit{Planck}$ LFI and $\textit{WMAP}$
polarization data within a Bayesian CMB analysis framework. We model
synchrotron emission with a power-law spectral energy distribution, and the sum
of AME and thermal dust emission through linear regression with the
$\textit{Planck}$ HFI 353 GHz data. This template-based dust emission model
allows us to constrain the level of polarized AME while making minimal
assumptions on its frequency dependence. We neglect cosmic microwave background
fluctuations, but show through simulations that these have a minor impact on
the results. We find that the resulting AME polarization fraction confidence
limit is sensitive to the polarized synchrotron spectral index prior, and for
priors steeper than $\beta_{\mathrm{s}} = -3.1\pm0.1$ we find an upper limit of
$p_{\mathrm{AME}}^{\rm max}\lesssim 0.6\,\%$ ($95\,\%$ confidence). In
contrast, for $\beta_{\mathrm{s}}=-3.0\pm0.1$, we find a nominal detection of
$p_{\mathrm{AME}}=2.5\pm1.0\,\%$ ($95\,\%$ confidence). These data are thus not
strong enough to simultaneously and robustly constrain both polarized
synchrotron emission and AME, and our main result is therefore a constraint on
the AME polarization fraction explicitly as a function of $\beta_\mathrm{s}$.
Combining the current $\textit{Planck}$ and $\textit{WMAP}$ observations with
measurements from high-sensitivity low-frequency experiments such as C-BASS and
QUIJOTE will be critical to improve these limits further. | Faint AGNs at z>4 in the CANDELS GOODS-S field: looking for contributors
to the reionization of the Universe: In order to derive the AGN contribution to the cosmological ionizing
emissivity we have selected faint AGN candidates at $z>4$ in the CANDELS
GOODS-South field which is one of the deepest fields with extensive
multiwavelength coverage from Chandra, HST, Spitzer and various groundbased
telescopes. We have adopted a relatively novel criterion. As a first step high
redshift galaxies are selected in the NIR $H$ band down to very faint levels
($H\leq27$) using reliable photometric redshifts. This corresponds at $z>4$ to
a selection criterion based on the galaxy rest-frame UV flux. AGN candidates
are then picked up from this parent sample if they show X-ray fluxes above a
threshold of $F_X\sim 1.5\times 10^{-17}$ cgs (0.5-2 keV). We have found 22 AGN
candidates at $z>4$ and we have derived the first estimate of the UV luminosity
function in the redshift interval $4<z<6.5$ and absolute magnitude interval
$-22.5\lesssim M_{1450} \lesssim -18.5$ typical of local Seyfert galaxies. The
faint end of the derived luminosity function is about two/four magnitudes
fainter at $z\sim 4-6$ than that derived from previous UV surveys. We have then
estimated ionizing emissivities and hydrogen photoionization rates in the same
redshift interval under reasonable assumptions and after discussion of possible
caveats, the most important being the large uncertainties involved in the
estimate of photometric redshift for sources with featureless, almost power-law
SEDs and/or low average escape fraction of ionizing photons from the AGN host
galaxies. We argue that, under reasonable evaluations of possible biases, the
probed AGN population can produce at $z=4-6.5$ photoionization rates consistent
with that required to keep highly ionized the intergalactic medium observed in
the Lyman-$\alpha$ forest of high redshift QSO spectra, providing an important
contribution to the cosmic reionization. |
Late-time decaying dark matter: constraints and implications for the
$H_0$-tension: We constrain and update the bounds on the life-time of a decaying dark matter
model with a warm massive daughter particle using the most recent low-redshift
probes. We use Supernovae Type-Ia, Baryon Acoustic Oscillations and the time
delay measurements of gravitationally lensed quasars. These data sets are
complemented by the early universe priors taken from the Cosmic Microwave
background. For the maximum allowed fraction of the relativistic daughter
particle, the updated bounds on the life-time are found to be $\tau > 9\,
\rm{Gyr}$ and $\tau >11\,\rm{Gyr}$ at $95\%$ C.L., for the two-body and
many-body decay scenarios, respectively. We also comment on the recent proposal
that the current two-body decaying dark matter model can provide resolution for
the $H_0$-tension, by contrasting against the standard $\Lambda$CDM model. We
infer that the current dark matter decaying scenario is unlikely to alleviate
the $H_0$-tension. We find that the decaying dark matter is able to reduce the
trend of the decreasing $H_0$ values with increasing lens redshifts observed in
the strong lensing dataset. | An Assessment of Contamination in the thermal-SZ Map Using Cross
Correlations: We search for the potential contamination in the Planck thermal
Sunyaev-Zeldovich (tSZ) map by calculating the cross-correlation between the
tSZ signal and weak lensing by large scale structure and the Cosmic Microwave
Background (CMB). The lensing data we use is the convergence map from the Red
Sequence Cluster Lensing Survey (RCSLens) and the Planck CMB lensing map. We
reconstruct the tSZ $y$ map with a Needlet Internal Linear Combination method
using the HFI sky maps from the Planck satellite. We remove the CMB signal
while minimizing the residual noise. The cross correlation signal from our
reconstructed $y$ map is consistent with that from the Planck team's NILC $y$
map. The CIB and galactic dust emission are two potential sources of
contamination in the reconstructed $y$ map. We remove the CIB signal by
subtracting the CIB maps reconstructed by Planck collaboration from the raw
temperature maps. We find that cross-correlation between the CIB and galactic
lensing contributes to $(7.5\pm6.0)\%$ in the Planck NILC tSZ cross galactic
lensing signal within $100<\ell<2000$, which implies that previous detections
of the tSZ cross galactic lensing is robust to CIB contaminations. In contrast,
the Planck NILC tSZ cross CMB lensing is biased by $(18.4\pm2.8)\%$ in the same
$\ell$ range. Galactic dust contamination is tested by projecting out a
grey-body dust models with different dust spectral indices. Galactic dust does
not affect galactic lensing cross tSZ signal significantly. |
Structures in the Planck map of the CMB: We present the results of the quest for ring-type structures on the maps
observed by the Planck satellite. | GEMINI 3D spectroscopy of BAL+IR+Fe II QSOs: II. IRAS 04505-2958 an
explosive QSO with hypershell and a new scenario for galaxy formation and
galaxy end: From a study of BAL + IR + Fe II QSOs (using deep Gemini GMOS-IFU
spectroscopy) new results are presented: for IRAS 04505-2958. Specifically, we
have studied in detail the out flow (OF) process and their associated
structures, mainly at two large galactic scales: (i) two blobs/shells (S1, S2)
at radius r = 1.1 and 2.2 kpc; and (ii) an external hypergiant shell (S3) at r
= 11 kpc. In addition, the presence of two very extended hypergiant shells (S4,
S5) at r = 80 kpc is discussed. From this GMOS study the following main results
were obtained: (i) For the external hypergiant shell S3 the kinematics GMOS
maps of the ionized gas show very similar features to those observed for the
prototype of exploding external supergiant shell: in NGC 5514. (ii) The main
knots K1, K2 and K3 -of this hypergiant shell S3- show a stellar population and
emission line ratios associated with the presence of a starburst + OF/shocks.
(iii) The internal shells S1 and S2 show structures, OF components and
properties very similar to those detected in the nuclear shells of Mrk 231.
(iv) The shells S1+S2 and S3 are aligned at PA = 131: i.e. suggesting that the
OF process is in the blow-out phase with bipolar structure. In addition, the
shells S4 and S5 (at 80-100 kpc scale) are aligned at PA = 40, i.e.: a bipolar
OF perpendicular to the internal OF. Finally, the generation of UHE cosmic rays
and neutrino/ dark-matter -associated with HyNe in BAL + IR + Fe II QSOs- is
discussed. |
Deep Chandra Monitoring Observations of NGC 4278: Catalog of Source
Properties: We present the properties of the discrete X-ray sources detected in our
monitoring program of the globular cluster (GC) rich elliptical galaxy, NGC
4278, observed with Chandra ACIS-S in six separate pointings, resulting in a
co-added exposure of 458-ks. From this deep observation, 236 sources have been
detected within the region overlapped by all observations, 180 of which lie
within the D25 ellipse of the galaxy. These 236 sources range in Lx from 3.5E36
erg/s (with 3sigma upper limit <1E37 erg/s) to ~2E40 erg/s, including the
central nuclear source which has been classified as a LINER. From optical data,
39 X-ray sources have been determined to be coincident with a globular cluster,
these sources tend to have high X-ray luminosity, with ten of these sources
exhibiting Lx>1E38 erg/s. From X-ray source photometry, it has been determined
that the majority of the 236 point sources that have well constrained colors,
have values that are consistent with typical LMXB spectra, with 29 of these
sources expected to be background objects from the logN-logS relation. There
are 103 sources in this population that exhibit long-term variability,
indicating that they are accreting compact objects. 3 of these sources have
been identified as transient candidates, with a further 3 possible transients.
Spectral variations have also been identified in the majority of the source
population, where a diverse range of variability has been identified,
indicating that there are many different source classes located within this
galaxy. | Massive data compression for parameter-dependent covariance matrices: We show how the massive data compression algorithm MOPED can be used to
reduce, by orders of magnitude, the number of simulated datasets that are
required to estimate the covariance matrix required for the analysis of
gaussian-distributed data. This is relevant when the covariance matrix cannot
be calculated directly. The compression is especially valuable when the
covariance matrix varies with the model parameters. In this case, it may be
prohibitively expensive to run enough simulations to estimate the full
covariance matrix throughout the parameter space. This compression may be
particularly valuable for the next-generation of weak lensing surveys, such as
proposed for Euclid and LSST, for which the number of summary data (such as
band power or shear correlation estimates) is very large, $\sim 10^4$, due to
the large number of tomographic redshift bins that the data will be divided
into. In the pessimistic case where the covariance matrix is estimated
separately for all points in an MCMC analysis, this may require an unfeasible
$10^9$ simulations. We show here that MOPED can reduce this number by a factor
of 1000, or a factor of $\sim 10^6$ if some regularity in the covariance matrix
is assumed, reducing the number of simulations required to a manageable $10^3$,
making an otherwise intractable analysis feasible. |
Simulating the LOcal Web (SLOW): I. Anomalies in the local density field: Context: Several observations of the local Universe (LU) point towards the
existence of very prominent structures. The presence of massive galaxy clusters
and local super clusters on the one hand, but also large local voids and
under-densities on the other hand. However, it is highly non trivial to connect
such different observational selected tracers to the underlying dark matter
(DM) distribution. Methods (abridged): We used a 500 Mpc/h large constrained
simulation of the LU with initial conditions based on peculiar velocities
derived from the CosmicFlows-2 catalogue and follow galaxy formation physics
directly in the hydro-dynamical simulations to base the comparison on stellar
masses of galaxies or X-ray luminosity of clusters. We also used the 2668 Mpc/h
large cosmological box from the Magneticum simulations to evaluate the
frequency of finding such anomalies in random patches within simulations.
Results: We demonstrate that haloes and galaxies in our constrained simulation
trace the local DM density field very differently. Thereby, this simulation
reproduces the observed 50% under-density of galaxy clusters and groups within
the sphere of ~100 Mpc when applying the same mass or X-ray luminosity limit
used in the observed cluster sample (CLASSIX), which is consistent with a
~1.5$\sigma$ feature. At the same time, the simulation reproduces the observed
over-density of massive galaxy clusters within the same sphere, which on its
own also corresponds to a ~1.5$\sigma$ feature. Interestingly, we find that
only 44 out of 15635 random realizations (i.e. 0.28%) are matching both
anomalies, making the LU to be a ~3$\sigma$ environment. We finally compared a
mock galaxy catalogue with the observed distribution of galaxies in the LU,
finding also a match to the observed factor of two over-density at ~16 Mpc as
well as the observed 15% under-density at ~40 Mpc distance. | When two become one: an apparent QSO pair turns out to be a single
quasar: We report on our serendipitous discovery that the objects Q 01323-4037 and Q
0132-4037, listed in the V\'eron-Cetty & V\'eron catalog (2006) as two
different quasars, are actually a quasar and a star. We briefly discuss the
origin of the misidentification, and provide a refined measurement of the
quasar redshift. |
The detection of FIR emission from high redshift star-forming galaxies
in the ECDF-S: ABRIDGED: We have used the LABOCA Survey of the ECDF-S (LESS) to investigate
rest-frame FIR emission from typical SF systems (LBGs) at redshift 3, 4, and 5.
We initially concentrate on LBGs at z~3 and select three subsamples on stellar
mass, extinction corrected SF and rest-frame UV-magnitude. We produce composite
870micron images of the typical source in our subsamples, obtaining ~4sigma
detections and suggesting a correlation between FIR luminosity and stellar
mass. We apply a similar procedure to our full samples at z~3, 4, 4.5 and 5 and
do not obtain detections - consistent with a simple scaling between FIR
luminosity and stellar mass. In order to constrain the FIR SED of these systems
we explore their emission at multiple wavelengths spanning the peak of dust
emission at z~3 using the Herschel SPIRE observations of the field. We obtain
detections at multiple wavelengths for both our stellar mass and UV-magnitude
selected samples, and find a best-fit SED with T_dust in the ~33-41K range. We
calculate L_FIR, obscured SFRs and M_dust, and find that a significant fraction
of SF in these systems is obscured. Interestingly, our extinction corrected SFR
sample does not display the large FIR fluxes predicted from its red UV-spectral
slope. This suggests that the method of assuming an intrinsic UV-slope and
correcting for dust attenuation may be invalid for this sample - and that these
are not in fact the most actively SF systems. All of our z~3 samples fall on
the `main sequence' of SF galaxies at z~3 and our detected subsamples are
likely to represent the high obscuration end of LBGs at their epoch. We compare
the FIR properties of our subsamples with various other populations, finding
that our stellar mass selected sample shows similar FIR characteristics to SMGs
at the same epoch and therefore potentially represents the low L_FIR end of the
high redshift FIR luminosity function. | Evidence for Large-Scale Fluctuations in the Metagalactic Ionizing
Background Near Redshift Six: The observed scatter in intergalactic Lyman-$\alpha$ opacity at $z \lesssim
6$ requires large-scale fluctuations in the neutral fraction of the
intergalactic medium (IGM) after the expected end of reionization.
Post-reionization models that explain this scatter invoke fluctuations in
either the ionizing ultraviolet background (UVB) or IGM temperature. These
models make very different predictions, however, for the relationship between
Lyman-$\alpha$ opacity and local density. Here we test these models using
Lyman-$\alpha$ emitting galaxies (LAEs) to trace the density field surrounding
the longest and most opaque known Lyman-$\alpha$ trough at $z < 6$. Using deep
Subaru Hyper Suprime-Cam narrow-band imaging, we find a highly significant
deficit of $z \simeq 5.7$ LAEs within 20 Mpc/$h$ of the trough. The results are
consistent with a model in which the scatter in Lyman-$\alpha$ opacity near $z
\sim 6$ is driven by large-scale UVB fluctuations, and disfavor a scenario in
which the scatter is primarily driven by variations in IGM temperature. UVB
fluctuations at this epoch present a boundary condition for reionization
models, and may help shed light on the nature of the ionizing sources. |
Clustering of primordial black holes with non-Gaussian initial
fluctuations: We formulate the two-point correlation function of primordial black holes
(PBHs) at their formation time, based on the functional integration approach
which has often been used in the context of halo clustering. We find that PBH
clustering on super-Hubble scales could never be induced in the case where the
initial primordial fluctuations are Gaussian, while it can be enhanced by the
so-called local-type trispectrum (four-point correlation function) of the
primordial curvature perturbations. | The Role of Starburst-AGN composites in Luminous Infrared Galaxy
Mergers: Insights from the New Optical Classification Scheme: We investigate the fraction of starbursts, starburst-AGN composites,
Seyferts, and LINERs as a function of infrared luminosity (L_IR) and merger
progress for ~500 infrared-selected galaxies. Using the new optical
classifications afforded by the extremely large data set of the Sloan Digital
Sky Survey, we find that the fraction of LINERs in IR-selected samples is rare
(< 5%) compared with other spectral types. The lack of strong infrared emission
in LINERs is consistent with recent optical studies suggesting that LINERs
contain AGN with lower accretion rates than in Seyfert galaxies. Most
previously classified infrared-luminous LINERs are classified as starburst-AGN
composite galaxies in the new scheme. Starburst-AGN composites appear to
"bridge" the spectral evolution from starburst to AGN in ULIRGs. The relative
strength of the AGN versus starburst activity shows a significant increase at
high infrared luminosity. In ULIRGs (L_IR >10^12 L_odot), starburst-AGN
composite galaxies dominate at early--intermediate stages of the merger, and
AGN galaxies dominate during the final merger stages. Our results are
consistent with models for IR-luminous galaxies where mergers of gas-rich
spirals fuel both starburst and AGN, and where the AGN becomes increasingly
dominant during the final merger stages of the most luminous infrared objects. |
Cosmological Simulations of Massive Compact High-z Galaxies: In order to investigate the structure and dynamics of the recently discovered
massive (M_* > 10^11 M_sun) compact z~2 galaxies, cosmological
hydrodynamical/N-body simulations of a proto-cluster region have been
undertaken. At z=2, the highest resolution simulation contains ~5800 resolved
galaxies, of which 509, 27 and 5 have M_* > 10^10 M_sun, > 10^11 M_sun and >
4x10^11 M_sun, respectively. Effective radii and characteristic stellar
densities have been determined for all galaxies. At z=2, for the definitely
well resolved mass range of M_* > 10^11 Msun, the mass-size relation is
consistent with observational findings for the most compact z~2 galaxies. The
very high velocity dispersion recently measured for a compact z~2 galaxy (~510
km/s; van Dokkum et al 2009) can be matched at about the 1-sigma level,
although a somewhat larger mass than the estimated M_* ~ 2 x 10^11 M_sun is
indicated. For the above mass range, the galaxies have an average axial ratio
<b/a> = 0.64 +/- 0.02 with a dispersion of 0.1, an average rotation to 1D
velocity dispersion ratio <v/sigma> = 0.46 +/- 0.06 with a dispersion of 0.3,
and a maximum value of v/sigma ~ 1.1. Rotation and velocity anisotropy both
contribute in flattening the compact galaxies. Some of the observed compact
galaxies appear flatter than any of the simulated galaxies. Finally, it is
found that the massive compact galaxies are strongly baryon dominated in their
inner parts, with typical dark matter mass fractions of order only 20% inside
of r=2R_eff. | Understanding the Reconstruction of the Biased Tracer: Recent development in the reconstruction of the large-scale structure (LSS)
has seen significant improvement in restoring the linear baryonic acoustic
oscillation (BAO) from at least the non-linear matter field. This outstanding
performance is achieved by iteratively solving the Monge-Ampere equation of the
mass conservation. However, this technique also relies on several assumptions
that are not valid in reality, namely the longitudinal displacement, the
absence of shell-crossing and homogeneous initial condition. In particular, the
conservation equation of the tracers comprises the biasing information that
breaks down the last assumption. Consequently, direct reconstruction would
entangle the non-linear displacement with complicated bias parameters and
further affect the BAO. In this paper, we formulate a theoretical model
describing the reconstructed biased map by matching the tracer overdensity with
an auxiliary fluid with vanishing initial perturbation. Regarding the
performance of the reconstruction algorithm, we show that even though the shot
noise is still the most significant limiting factors in a realistic survey,
inappropriate treatment of the bias could also shift the reconstructed frame
and therefore broaden the BAO peak. We suggest that, in principle, this
bias-related BAO smearing effect could be used to independently self-calibrate
the bias parameters. |
Evolution of shocks and turbulence in the formation of galaxy clusters
embedded in Megaparsec-scale filaments: Massive structures like cluster of galaxies, embedded in cosmic filaments,
release enormous amount of energy through their interactions. These events are
associated with production of Mpc-scale shocks and injection of considerable
amount of turbulence, affecting the non-thermal energy budget of the ICM. In
order to study this thoroughly, we performed a set of cosmological simulations
using the hydrodynamical code Enzo. We studied the formation of clusters
undergoing major mergers, the propagation of merger shocks and their
interaction with the filamentary cosmic web. This interaction is shown to
produce peripheral structures remarkably similar to giant radio relics
observed, for example, in Abell 3376 and Abell 3667. We find a relatively long
timescale (about 4 Gyr) for turbulence decay in the centre of major merging
clusters. This timescale is substantially longer than typically assumed in the
turbulent re-acceleration models, invoked for explaining the statistics of
observed radio halos. | Measuring Polarized Emission in Clusters in the CMB S4 Era: The next generation of CMB experiments (CMB Stage-4) will produce a
Sunyaev-Zel'dovich (SZ) cluster catalog containing $\sim10^{5}$ objects, two
orders of magnitudes more than currently available. In this paper, we discuss
the detectability of the polarized signal generated by scattering of the CMB
quadrupole on the cluster electron gas using this catalog. We discuss the
possibility of using this signal to measure the relationship between cluster
optical depth and mass. We find that the area of observation of S4 maximizes
the signal-to-noise (S/N) on the polarized signal but that this S/N is
extremely small for an individual cluster, of order 0.5% for a typical cluster
in our catalog, the main source of noise being the residual primordial E-mode
signal. However, we find that the signal could be detected using the full
cluster catalog and that the significance of the result will increase linearly
with the size of the CMB S4 telescope mirror. |
Gravity's Islands: Parametrizing Horndeski Stability: Cosmic acceleration may be due to modified gravity, with effective field
theory or property functions describing the theory. Connection to cosmological
observations through practical parametrization of these functions is difficult
and also faces the issue that not all assumed time dependence or parts of
parameter space give a stable theory. We investigate the relation between
parametrization and stability in Horndeski gravity, showing that the results
are highly dependent on the function parametrization. This can cause
misinterpretations of cosmological observations, hiding and even ruling out key
theoretical signatures. We discuss approaches and constraints that can be
placed on the property functions and scalar sound speed to preserve some
observational properties, but find that parametrizations closest to the
observations, e.g. in terms of the gravitational strengths, offer more robust
physical interpretations. In addition we present an example of how future
observations of the B-mode polarization of the cosmic microwave background from
primordial gravitational waves can probe different aspects of gravity. | Dark halo response and the stellar initial mass function in early-type
and late-type galaxies: We investigate the origin of the relations between stellar mass and optical
circular velocity for early-type (ETG) and late-type (LTG) galaxies --- the
Faber-Jackson (FJ) and Tully-Fisher (TF) relations. We combine measurements of
dark halo masses (from satellite kinematics and weak lensing), and the
distribution of baryons in galaxies (from a new compilation of galaxy scaling
relations), with constraints on dark halo structure from cosmological
simulations. The principle unknowns are the halo response to galaxy formation
and the stellar initial mass function (IMF). The slopes of the TF and FJ
relations are naturally reproduced for a wide range of halo response and IMFs.
However, models with a universal IMF and universal halo response cannot
simultaneously reproduce the zero points of both the TF and FJ relations. For a
model with a universal Chabrier IMF, LTGs require halo expansion, while ETGs
require halo contraction. A Salpeter IMF is permitted for high mass (sigma >
180 km/s) ETGs, but is inconsistent for intermediate masses, unless
V_circ(R_e)/sigma_e > 1.6. If the IMF is universal and close to Chabrier, we
speculate that the presence of a major merger may be responsible for the
contraction in ETGs while clumpy accreting streams and/or feedback leads to
expansion in LTGs. Alternatively, a recently proposed variation in the IMF
disfavors halo contraction in both types of galaxies. Finally we show that our
models naturally reproduce flat and featureless circular velocity profiles
within the optical regions of galaxies without fine-tuning. |
Highlights and Conclusions of the Chalonge 13th Paris Cosmology
Colloquium: The 13th Chalonge Paris Cosmology Colloquium was held at the historic
Perrault building of Observatoire de Paris on 23-25 July 2009. The Colloquium
was held in the spirit of the Chalonge School, putting together real
cosmological and astrophysical data and hard theory predictive approach in the
framework of the Standard Model of the Universe. Peter Biermann, James Bullock,
Claudio Destri, Hector de Vega, Massimo Giovannini, Sasha Kashlinsky, Eiichiro
Komatsu, Anthony Lasenby and Norma G. Sanchez present here their highlights of
the Colloquium. The summary and conclusions by H. J. de Vega, M. C. Falvella
and N. G. Sanchez stress among other points: (i) the primordial CMB
fluctuations are almost gaussian, large primordial non-gaussianity and large
running index are strongly disfavored. The primordial graviton ratio r is
predicted in the effective theory of inflation to be between 0.021 and 0.053,
at reach of the next CMB observations. (ii) Dark energy observations are
consistent with the cosmological constant. (iii) The cosmic ray positron excess
recently observed is explained by natural astrophysical processes. (iv) The
heavy dark matter particle candidates ( > 1 GeV, wimps) became strongly
disfavored, while cored (non cusped) dark matter halos and light (keV scale
mass) dark matter are being increasingly favored from theory and astrophysical
observations. The Daniel Chalonge Medal 2009 was awarded to Peter Biermann
during the Colloquium. Photos of the Colloquium are included. | Comparison of delensing methodologies and assessment of the delensing
capabilities of future experiments: Most of the CMB experiments proposed for the next generation aim to detect
the Primordial Gravitational Wave Background (PGWB). The fulfillment of this
objective depends on our capacity to separate Galactic foreground emissions and
to \emph{delens} the secondary B-mode component induced by weak gravitational
lensing. Focusing on the latter of these efforts, in this work we briefly
review the basic aspects of lensing, and exhaustively compare the performance
of current delensing methodologies and implementations within the Born
approximation as a preparation for the analysis of the data to come in the
following years. Two of the main conclusions that can be drawn from our study
are that, for next-generation experiments, delensing efficiency will still be
limited by the quality of the data itself rather than by the limitations of
current delensing methodologies, and that template delensing within the
antilensing approximation will be the optimal (balancing accuracy and
computational cost) technique to employ. We then evaluate the delensing
capabilities of future experiments (like the Simons Observatory, the CMB
Stage-IV, or the LiteBIRD and PICO satellites) by applying that methodology
onto numerical simulations of the typical CMB and lensing potential
reconstructions that they are expected to produce, and quantify how internal
and external delensing will help them to improve their sensitivity to detect
the PGWB. We also consider the benefits that a joint analysis of their data
would provide. |
Testing Verlinde's emergent gravity in early-type galaxies: Verlinde derived gravity as an emergent force from the information flow,
through two-dimensional surfaces and recently, by a priori postulating the
entanglement of information in 3D space, he derived the effect of the
gravitational potential from dark matter (DM) as the entropy displacement of
dark energy by baryonic matter. In Emergent Gravity (EG) this apparent DM
depends only on the baryonic mass distribution and the present-day value of the
Hubble parameter. In this paper we test the EG proposition, formalized by
Verlinde for a spherical and isolated mass distribution, using the central
velocity dispersion, $\sigma$ and the light distribution in a sample of 4260
massive and local early-type galaxies (ETGs) from the SPIDER sample. Our
results remain unaltered if we consider the sample of 807 roundest field
galaxies. We derive the predictions by EG for the stellar mass-to-light ratio
(M/L) and the Initial Mass Function (IMF), and compare them with the same
inferences derived from a) DM-based models, b) MOND and c) stellar population
models. We demonstrate that, consistently with a classical Newtonian framework
with a DM halo component, or alternative theories of gravity as MOND, the
central dynamics can be fitted if the IMF is assumed non-universal. The results
can be interpreted with a IMF lighter than a standard Chabrier at low-$\sigma$,
and bottom-heavier IMFs at larger $\sigma$. We find lower, but still
acceptable, stellar M/L in EG theory, if compared with the DM-based NFW model
and with MOND. The results from EG are comparable to what is found if the DM
haloes are adiabatically contracted and with expectations from spectral
gravity-sensitive features. If the strain caused by the entropy displacement
would be not maximal, as adopted in the current formulation, then the dynamics
of ETGs could be reproduced with larger M/L. (abridged) | Constraints on the temperature of the intergalactic medium at z=8.4 with
21-cm observations: We compute robust lower limits on the spin temperature, $T_{\rm S}$, of the
$z=8.4$ intergalactic medium (IGM), implied by the upper limits on the 21-cm
power spectrum recently measured by PAPER-64. Unlike previous studies which
used a single epoch of reionization (EoR) model, our approach samples a large
parameter space of EoR models: the dominant uncertainty when estimating
constraints on $T_{\rm S}$. Allowing $T_{\rm S}$ to be a free parameter and
marginalizing over EoR parameters in our Markov Chain Monte Carlo code 21CMMC,
we infer $T_{\rm S}\ge3 {\rm K}$ (corresponding approximately to $1\sigma$) for
a mean IGM neutral fraction of $\bar{x}_{\rm H{\scriptsize I}}\gtrsim0.1$. We
further improve on these limits by folding-in additional EoR constraints based
on: (i) the dark fraction in QSO spectra, which implies a strict upper limit of
$\bar{x}_{\rm H{\scriptsize I}}[z=5.9]\leq 0.06+0.05 \,(1\sigma)$; and (ii) the
electron scattering optical depth, $\tau_{\rm e}=0.066\pm0.016\,(1\sigma)$
measured by the Planck satellite. By restricting the allowed EoR models, these
additional observations tighten the approximate $1\sigma$ lower limits on the
spin temperature to $T_{\rm S} \ge 6$ K. Thus, even such preliminary 21-cm
observations begin to rule out extreme scenarios such as `cold reionization',
implying at least some prior heating of the IGM. The analysis framework
developed here can be applied to upcoming 21-cm observations, thereby providing
unique insights into the sources which heated and subsequently reionized the
very early Universe. |
Halo assembly bias from Separate Universe simulations: We present a calibration of halo assembly bias using the Separate Universe
technique. Specifically, we measure the response of halo abundances at fixed
mass and concentration to the presence of an infinite-wavelength initial
perturbation. We develop an analytical framework for describing the
concentration dependence of this peak-background split halo bias -- a measure
of assembly bias -- relying on the near-Lognormal distribution of halo
concentration at fixed halo mass. The combination of this analytical framework
and the Separate Universe technique allows us to achieve very high precision in
the calibration of the linear assembly bias $b_1$, and qualitatively reproduces
known trends such as the monotonic decrease (increase) of $b_1$ with halo
concentration at large (small) masses. The same framework extends to the
concentration dependence of higher order bias parameters $b_n$, and we present
the first calibration of assembly bias in $b_2$. Our calibrations are directly
applicable in analytical Halo Model calculations that seek to robustly detect
galaxy assembly bias in observational samples. We detect a non-universality in
the $b_1 - b_2$ relation arising from assembly bias, and suggest that
simultaneous measurements of these bias parameters could be used to both detect
the signature of assembly bias as well as mitigate its effects in cosmological
analyses. | Decaying Dark Matter: Simulations and Weak-Lensing Forecast: Despite evidence for the existence of dark matter (DM) from very high and low
redshifts, a moderate amount of DM particle decay remains a valid possibility.
This includes both models with very long-lived yet unstable particles or mixed
scenarios where only a small fraction of dark matter is allowed to decay. In
this paper, we investigate how DM particles decaying into radiation affect
non-linear structure formation. We look at the power spectrum and its redshift
evolution, varying both the decay lifetime ($\tau$) and the fraction of
decaying-to-total dark matter ($f$), and we propose a fitting function that
reaches sub-percent precision below $k\sim10$ h/Mpc. Based on this fit, we
perform a forecast analysis for a Euclid-like weak lensing (WL) survey,
including both massive neutrino and baryonic feedback parameters. We find that
with WL observations alone, it is possible to rule out decay lifetimes smaller
than $\tau=75$ Gyr (at 95 percent CL) for the case that all DM is unstable.
This constraint improves to $\tau=182$ Gyr if the WL data is combined with CMB
priors from the Planck satellite and to $\tau=275$ Gyr if we further assume
baryonic feedback to be fully constrained by upcoming Sunyaev-Zeldovich or
X-ray data. The latter shows a factor of 3.2 improvement compared to
constraints from CMB data alone. Regarding the scenario of a strongly decaying
sub-component of dark matter with $\tau\sim 30$ Gyr or lower, it will be
possible to rule out a decaying-to-total fraction of $f>0.49$, $f>0.21$, and
$f>0.13$ (at the 95 percent CL) for the same three scenarios. We conclude that
the upcoming stage-IV WL surveys will allow us to significantly improve current
constraints on the stability of the dark matter sector. |
Analytic Approximations for the Primordial Power Spectrum with Israel
Junction Conditions: This work compares cosmological matching conditions used in approximating
generic pre-inflationary phases of the universe. We show that the joining
conditions for primordial scalar perturbations assumed by Contaldi et al. are
inconsistent with the physically motivated Israel junction conditions, however,
performing general relativistic matching with the aforementioned constraints
results in unrealistic primordial power spectra. Eliminating the need for
ambiguous matching, we look at an alternative semi-analytic model for producing
the primordial power spectrum allowing for finite duration cosmological phase
transitions. | Reconstruction of Primordial Power Spectrum of curvature perturbation
from the merger rate of Primordial Black Hole Binaries: The properties of primordial curvature perturbations on small scales are
still unknown while those on large scales have been well probed by the
observations of the cosmic microwave background anisotropies and the large
scale structure. In this paper, we propose the reconstruction method of
primordial curvature perturbations on small scales through the merger rate of
binary primordial black holes, which could form from large primordial curvature
perturbation on small scales. |
AGN contamination of galaxy-cluster thermal X-ray emission: predictions
for eRosita from cosmological simulations: In this study, we present a modelling of the X-ray emission from the
simulated SMBHs within the cosmological hydrodynamical Magneticum Pathfinder
Simulation, in order to study the statistical properties of the resulting X-ray
Active Galactic Nuclei (AGN) population and their expected contribution to the
X-ray flux from galaxy clusters. The simulations reproduce the evolution of the
observed unabsorbed AGN bolometric luminosity functions (LFs) up to redshift
z~2, consistently with previous works. Furthermore, we study the evolution of
the LFs in the soft (SXR) and hard (HXR) X-ray bands by means of synthetic
X-ray data generated with the PHOX simulator, that includes an
observationally-motivated modelling of an instrinsic absorption component,
mimicking the torus around the AGN. The reconstructed SXR and HXR AGN LFs
present a remarkable agreement with observational data up to z~2 when an
additional obscuration fraction for Compton-thick AGN is assumed, although a
discrepancy still exists for the SXR LF at z=2.3. With this approach, we also
generate full eROSITA mock observations to predict the level of contamination
due to AGN of the intra-cluster medium (ICM) X-ray emission, which can affect
cluster detection especially at high redshifts. We find that, at z~1-1.5, for
20-40% of the clusters with M500>3e13 Msun/h, the AGN counts in the observed
SXR band exceed by more than a factor of 2 the counts from the whole ICM. | HST/COS observations of a new population of associated QSO absorbers: (Abridged) We present a sample of new population of associated absorbers,
detected through Ne VIII \lambda\lambda 770,780 absorption, in HST/COS spectra
of intermediate redshift (0.45 < z < 1.21) quasars (QSOs). Our sample comprised
of total 12 associated Ne VIII systems detected towards 8 lines of sight (none
of them are radio bright). The incidence rate of these absorbers is found to be
40%. Majority of the Ne VIII systems at small ejection velocities (v_ej) show
complete coverage of the background source, but systems with higher v_ej show
lower covering fractions (i.e. f_c < 0.8) and systematically higher values of
N(Ne VIII). We detect Mg X \lambda\lambda 609,624 absorption in 7 out of the 8
Ne VIII systems where the expected wavelength range is cover by our spectra and
is free of any strong blending. We report the detections of Na IX
\lambda\lambda 681,694 absorption, for the first time, in three highest
ejection velocity (e.g. v_ej > 7,000 km/s) systems in our sample. All these
systems show very high N(Ne VIII) (i.e. > 10^{15.6} cm^{-2}), high ionization
parameter (i.e. log U > 0.5), high metallicity (i.e. Z > Z_{\odot}), and
ionization potential dependent f_c values. The observed column density ratios
of different ions are reproduced by multiphase photoionization (PI) and/or
collisional ionization (CI) equilibrium models. While solar abundance ratios
are adequate in CIE, enhancement of Na relative to Mg is required in PI models
to explain our observations. |
Strong Lensing Analysis of PLCK G004.5$-$19.5, a Planck-Discovered
Cluster Hosting a Radio Relic at $z=0.52$: The recent discovery of a large number of galaxy clusters using the
Sunyaev-Zel'dovich (SZ) effect has opened a new era on the study of the most
massive clusters in the Universe. Multi-wavelength analyses are required to
understand the properties of these new sets of clusters, which are a sensitive
probe of cosmology. We aim at a multi-wavelength characterization of PLCK
G004.5$-$19.5, one of the most massive X-ray validated SZ effect-selected
galaxy clusters discovered by the Planck satellite. We have observed PLCK
G004.5$-$19.5 with GMOS on Gemini South for optical imaging and spectroscopy,
and performed a strong lensing analysis. We also searched for associated radio
emission in published catalogs. An analysis of the optical images confirms that
this is a massive cluster, with a dominant central galaxy (the BCG) and an
accompanying red sequence of galaxies, plus a $14''$-long strong lensing arc.
Longslit pectroscopy of 6 cluster members shows that the cluster is at
$z=0.516\pm0.002$. We also targeted the strongly lensed arc, and found $z_{\rm
arc}=1.601$. We use LensTool to carry out a strong lensing analysis, from which
we measure a median Einstein radius $\theta_E(z_s=1.6)\simeq30''$ and estimate
an enclosed mass $M_E=2.45_{-0.47}^{+0.45}\times10^{14}\,M_\odot$. By
extrapolating an NFW profile we find a total mass
$M_{500}^{SL}=4.0_{-1.0}^{+2.1}\times10^{14}M_\odot$. Including a constraint on
the mass from previous X-ray observations yields a slightly higher mass,
$M_{500}^{SL+X}=6.7_{-1.3}^{+2.6}\times10^{14}M_\odot$, marginally consistent
with the value from strong lensing alone. High-resolution radio images from
TGSS at 150~MHz reveal that PLCK G004.5$-$19.5 hosts a powerful radio relic on
scales $\lesssim500$ kpc. Emission at the same location is also detected in low
resolution images at 843~MHz and 1.4~GHz. This is one of the higher redshift
radio relics known to date. | The End of the Rainbow: What Can We Say About the Extragalactic
Sub-Megahertz Radio Sky?: The Galactic disc is opaque to radio waves from extragalactic sources with
frequencies nu less than ~3 MHz. However, radio waves with kHz, Hz, and even
lower frequencies may propagate through the intergalactic medium (IGM). I argue
that the presence of these waves can be inferred by using the Universe as our
detector. I discuss possible sub-MHz sources and set new non-trivial upper
limits on the energy density of sub-MHz radio waves in galaxy clusters and the
average cosmic background. Limits based on five effects are considered: (1)
changes in the expansion of the Universe from the radiation energy density (2)
heating of the IGM by free-free absorption; (3) radiation pressure squeezing of
IGM clouds by external radio waves; (4) synchrotron heating of electrons in
clusters; and (5) Inverse Compton upscattering of sub-MHz radio photons. Any
sub-MHz background must have an energy density much smaller than the CMB at
frequencies below 1 MHz. The free-free absorption bounds from the Lyman-alpha
forest are potentially the strongest, but are highly dependent on the
properties of sub-MHz radio scattering in the IGM. I estimate an upper limit of
6 * 10^4 L_sun Mpc^-3 for the emissivity within Lyman-alpha forest clouds in
the frequency range 5 - 200 Hz. The sub-MHz energy density in the Coma cluster
is constrained to be less than ~10^-15 erg cm^-3. At present, none of the
limits is strong enough to rule out a maximal T_b = 10^12 K sub-MHz synchrotron
background, but other sources may be constrained with a better knowledge of
sub-MHz radio propagation in the IGM. |
The Planck clusters in the LOFAR sky. III. LoTSS-DR2: Dynamic states and
density fluctuations of the intracluster medium: The footprint of LoTSS-DR2 covers 309 PSZ2 galaxy clusters, 83 of which host
a radio halo and 26 host a radio relic(s). It provides us an excellent
opportunity to statistically study the properties of extended cluster radio
sources, especially their connection with merging activities. We aim to
quantify cluster dynamic states to investigate their relation with the
occurrence of extended radio sources. We also search for connections between
intracluster medium (ICM) turbulence and nonthermal characteristics of radio
halos in the LoTSS-DR2. We analyzed XMM-Newton and Chandra archival X-ray data
and computed concentration parameters and centroid shifts that indicate the
dynamic states of the clusters. We also performed a power spectral analysis of
the X-ray surface brightness (SB) fluctuations to investigate large-scale
density perturbations and estimate the turbulent velocity dispersion. The power
spectral analysis results in a large scatter density fluctuation amplitude. We
therefore only found a marginal anticorrelation between density fluctuations
and cluster relaxation state, and we did not find a correlation between density
fluctuations and radio halo power. Nevertheless, the injected power for
particle acceleration calculated from turbulent dissipation is correlated with
the radio halo power, where the best-fit unity slope supports the turbulent
(re)acceleration scenario. Two different acceleration models, transit-time
damping and adiabatic stochastic acceleration, cannot be distinguished due to
the large scatter of the estimated turbulent Mach number. We introduced a new
quantity $[kT\cdot Y_X]_{r_\mathrm{RH}}$, which is proportional to the
turbulent acceleration power assuming a constant Mach number. This quantity is
strongly correlated with radio halo power, where the slope is also unity. | Emission models and EBL as a tool to measure the redshift of BL Lac
objects: We introduce a new method to determine the redshift of unknown-redshift BL
Lac Objects. The method relies on simultaneous multi-wavelength (MWL)
observations of BL Lac objects in optical, X-ray, HE (E>100 MeV) gamma-rays and
VHE (E>100 GeV)gamma-rays. It involves best-fitting spectral energy
distribution (SED) from optical through HE gamma-rays with a
Synchrotron-Self-Compton (SSC) model. We extrapolate such best fitting model
into VHE regime, and assume that it represents the intrinsic emission of the
object. We then compare the observed VHE flux which has been affected by the
interaction with Extragalactic Background Light (EBL). Constraining the
measured vs intrinsic emission leads to the determination of gamma-gamma
opacity. Comparing the obtained opacity with the predicted opacity based on EBL
model, we obtain the redshift of the photon source. |
Cosmological Information in Perturbative Forward Modeling: We study how well perturbative forward modeling can constrain cosmological
parameters compared to conventional analyses. We exploit the fact that in
perturbation theory the field-level posterior can be computed analytically in
the limit of small noise. In the idealized case where the only relevant
parameter for the nonlinear evolution is the nonlinear scale, we argue that
information content in this posterior is the same as in the $n$-point
correlation functions computed at the same perturbative order. In the real
universe other parameters can be important, and there are possibly enhanced
effects due to nonlinear interactions of long and short wavelength fluctuations
that can either degrade the signal or increase covariance matrices. We identify
several different parameters that control these enhancements and show that for
some shapes of the linear power spectrum they can be large. This leads to
degradation of constraints in the standard analyses, even though the effects
are not dramatic for a $\Lambda$CDM-like cosmology. The aforementioned
long-short couplings do not affect the field-level inference which remains
optimal. Finally, we show how in these examples calculation of the perturbative
posterior motivates new estimators that are easier to implement in practice
than the full forward modelling but lead to nearly optimal constraints on
cosmological parameters. | LOFAR 150-MHz observations of the Boötes field: Catalogue and Source
Counts: We present the first wide area (19 deg$^2$), deep ($\approx120-150$ {\mu}Jy
beam$^{-1}$), high resolution ($5.6 \times 7.4$ arcsec) LOFAR High Band Antenna
image of the Bo\"otes field made at 130-169 MHz. This image is at least an
order of magnitude deeper and 3-5 times higher in angular resolution than
previously achieved for this field at low frequencies. The observations and
data reduction, which includes full direction-dependent calibration, are
described here. We present a radio source catalogue containing 6276 sources
detected over an area of $19$\,deg$^2$, with a peak flux density threshold of
$5\sigma$. As the first thorough test of the facet calibration strategy,
introduced by van Weeren et al., we investigate the flux and positional
accuracy of the catalogue. We present differential source counts that reach an
order of magnitude deeper in flux density than previously achieved at these low
frequencies, and show flattening at 150 MHz flux densities below 10 mJy
associated with the rise of the low flux density star-forming galaxies and
radio-quiet AGN. |
Dynamics of Non-minimally Coupled Scalar Fields in the Jordan Frame: The presence of scalar fields with non-minimal gravitational interactions of
the form $\xi |\phi|^2 R$ may have important implications for the physics of
the early universe. While many studies solve the dynamics of non-minimally
coupled scalars in the Einstein frame, where gravity is simply described by the
Einstein-Hilbert action, we instead propose a procedure to solve the dynamics
directly in the original Jordan frame where the non-minimal couplings are
maintained explicitly. Our algorithm can be applied to scenarios that include
minimally coupled fields and an arbitrary number of non-minimally coupled
scalars, with the expansion of the universe sourced by all fields present. This
includes situations when the dynamics become fully inhomogeneous, fully
non-linear (due to e.g.~backreaction or mode rescattering effects), and/or when
the expansion of the universe is dominated by non-minimally coupled species. As
an example, we study geometric preheating with a non-minimally coupled scalar
spectator field when the inflaton oscillates following the end of inflation. In
the future, our technique may be used to shed light on aspects of the
equivalence of the Jordan and Einstein frames at the quantum level. | Stellar Tidal Streams in Spiral Galaxies of the Local Volume: A Pilot
Survey with Modest Aperture Telescopes: [Abridged] Within the hierarchical framework for galaxy formation, minor
merging and tidal interactions are expected to shape all large galaxies to the
present day. As a consequence, most seemingly normal disk galaxies should be
surrounded by spatially extended stellar 'tidal features' of low surface
brightness. As part of a pilot survey for such interaction signatures, we have
carried out ultra deep, wide field imaging of 8 isolated spiral galaxies in the
Local Volume, with data taken at small (D=0.1-0.5m) robotic telescopes that
provide exquisite surface brightness sensitivity (mu_V)~28.5$ mag/arcsec^2).
This initial observational effort has led to the discovery of six previously
undetected extensive (to ~30 kpc) stellar structures in the halos surrounding
these galaxies, likely debris from tidally disrupted satellites. In addition,
we confirm and clarify several enormous stellar over-densities previously
reported in the literature, but never before interpreted as tidal streams. Even
this pilot sample of galaxies exhibits strikingly diverse morphological
characteristics of these extended stellar features: great circle-like features
that resemble the Sagittarius stream surrounding the Milky Way, remote shells
and giant clouds of presumed tidal debris far beyond the main stelar body, as
well as jet-like features emerging from galactic disks. A qualitative
comparison with available simulations set in a Lambda-Cold Dark Matter
cosmology shows that the extraordinary variety of stellar morphologies detected
in this pilot survey matches that seen in those simulations. The common
existence of these tidal features around 'normal' disk galaxies and the
morphological match to the simulations constitutes new evidence that these
theoretical models also apply to a large number of other Milky Way-mass disk
galaxies in the Local Volume. |
Primordial cosmic complexity and effects of reheating: We study the effects of the reheating phase on the evolution of complexities
for the primordial curvature perturbation using the squeezed formalism. We
examine the evolution of the out-of-time correlator, the quantum discord, and
circuit complexity, starting from the inflationary epoch to the
radiation-dominated epoch with different reheating scenarios. We find that for
a mode that reenters the horizon after reheating, the effect of a finite
reheating epoch on the characteristic \textit{freeze-in} amplitude of these
primordial complexities can only be distinguished up to three different classes
depending on whether the equation of state parameter: $(i)$ $w_\mathrm{re}=1/3$
$(ii)$ $w_\mathrm{re}<1/3$, or, (iii) $w_\mathrm{re}>1/3$. For reheating with
different EOS within these classes, the final amplitude will be the same --
hence, the detailed signature of reheating with a class on the complexity
measures will be lost. Taking the central value of the scalar spectral index
($n_s=0.9649$) from Planck and the equation of state during reheating
$w_\mathrm{re}=0.25$ as benchmark values, we found that the behavior of the
complexities for all modes smaller than $1.27\times10^{16}\mathrm{Mpc^{-1}}$
can be classified as above. However, for the small-scale modes reentering the
horizon during reheating, the signature of EOS on the evolution of these two
complexities will be embedded in each of the cases separately. | The Origin of Disks and Spheroids in Simulated Galaxies: In the simplest scenario, disk galaxies form predominantly in halos with high
angular momentum and quiet recent assembly history, whereas spheroids are the
slowly-rotating remnants of repeated merging events. We explore these
assumptions using one hundred systems with halo masses similar to that of the
Milky Way, identified in a series of cosmological gasdynamical simulations
GIMIC. At z=0, the simulated galaxies exhibit a wide variety of morphologies,
from dispersion-dominated spheroids to pure disk galaxies. Surprisingly, these
morphological features are very poorly correlated with their halo properties:
disks form in halos with high and low net spin, and mergers play a negligible
role in the formation of spheroid stars, most of which form in-situ. More
important to morphology is the coherent alignment of the angular momentum of
baryons that accrete over time to form a galaxy. Spheroids tend to form when
the spin of newly-accreted gas is misaligned with that of the extant galaxy,
leading to the episodic formation of stars with different kinematics that
cancel out the net rotation of the system. Disks, on the other hand, form out
of gas that flows in with similar angular momentum to that of earlier-accreted
material. Gas accretion from a hot corona thus favours disk formation, whereas
gas that flows "cold", often along separate, misaligned filaments, favours the
formation of spheroids. In this scenario, most spheroids consist of
superpositions of stellar components with distinct kinematics, age, and
metallicity, an arrangement that might survive to the present day given the
paucity of major mergers. Since angular momentum is acquired largely at
turnaround, morphology is imprinted early by the interplay of the tidal field
and the shape of the material destined to form the galaxy. |
A practical approach to cosmological perturbations in modified gravity: The next generation of large scale surveys will not only measure cosmological
parameters within the framework of General Relativity, but will also allow for
precision tests of the framework itself. At the order of linear perturbations,
departures from the growth in the LCDM model can be quantified in terms of two
functions of time and Fourier number k. We argue that in local theories of
gravity, in the quasi-static approximation, these functions must be ratios of
polynomials in k, with the numerator of one function being equal to the
denominator of the other. Moreover, the polynomials are even and of second
degree in practically all viable models considered today. This means that,
without significant loss of generality, one can use data to constraint only
five functions of a single variable, instead of two functions of two variables.
Furthermore, since the five functions are expected to be slowly varying, one
can fit them to data in a non-parametric way with the aid of an explicit
smoothness prior. We discuss practical application of this parametrization to
forecasts and fits. | The signal of the stochastic gravitational wave background and the
angular correlation of its energy density: The gravitational wave radiation emitted by all, resolved and unresolved,
astrophysical sources in the observable universe generates a stochastic
background. This background has a directional dependence inherited from the
inhomogeneities of the matter distribution. This article proposes a new and
independent derivation of the angular dependence of its energy density by
focusing on the total gravitational wave signal produced by an ensemble of
incoherent sources. This approach clarifies the origin of the angular
correlation and the relation between the gravitational wave signal that can be
measured by interferometers and the energy density of the stochastic
background. |
Kelvin-Helmholtz instabilities at the sloshing cold fronts in the Virgo
cluster as a measure for the effective ICM viscosity: Sloshing cold fronts (CFs) arise from minor merger triggered gas sloshing.
Their detailed structure depends on the properties of the intra-cluster medium
(ICM): hydrodynamical simulations predict the CFs to be distorted by
Kelvin-Helmholtz instabilities (KHIs), but aligned magnetic fields, viscosity,
or thermal conduction can suppress the KHIs. Thus, observing the detailed
structure of sloshing CFs can be used to constrain these ICM properties. Both
smooth and distorted sloshing CFs have been observed, indicating that the KHI
is suppressed in some clusters, but not in all. Consequently, we need to
address at least some sloshing clusters individually before drawing general
conclusions about the ICM properties. We present the first detailed attempt to
constrain the ICM properties in a specific cluster from the structure of its
sloshing CF. Proximity and brightness make the Virgo cluster an ideal target.
We combine observations and Virgo-specific hydrodynamical sloshing simulations.
Here we focus on a Spitzer-like temperature dependent viscosity as a mechanism
to suppress the KHI, but discuss the alternative mechanisms in detail. We
identify the CF at 90 kpc north and north-east of the Virgo center as the best
location in the cluster to observe a possible KHI suppression. For viscosities
$\gtrsim$ 10% of the Spitzer value KHIs at this CF are suppressed. We describe
in detail the observable signatures at low and high viscosities, i.e. in the
presence or absence of KHIs. We find indications for a low ICM viscosity in
archival XMM-Newton data and demonstrate the detectability of the predicted
features in deep Chandra observations. | Large-Scale Structure Formation: from the first non-linear objects to
massive galaxy clusters: The large-scale structure of the Universe formed from initially small
perturbations in the cosmic density field, leading to galaxy clusters with up
to 10^15 Msun at the present day. Here, we review the formation of structures
in the Universe, considering the first primordial galaxies and the most massive
galaxy clusters as extreme cases of structure formation where fundamental
processes such as gravity, turbulence, cooling and feedback are particularly
relevant. The first non-linear objects in the Universe formed in dark matter
halos with 10^5-10^8 Msun at redshifts 10-30, leading to the first stars and
massive black holes. At later stages, larger scales became non-linear, leading
to the formation of galaxy clusters, the most massive objects in the Universe.
We describe here their formation via gravitational processes, including the
self-similar scaling relations, as well as the observed deviations from such
self-similarity and the related non-gravitational physics (cooling, stellar
feedback, AGN). While on intermediate cluster scales the self-similar model is
in good agreement with the observations, deviations from such self-similarity
are apparent in the core regions, where numerical simulations do not reproduce
the current observational results. The latter indicates that the interaction of
different feedback processes may not be correctly accounted for in current
simulations. Both in the most massive clusters of galaxies as well as during
the formation of the first objects in the Universe, turbulent structures and
shock waves appear to be common, suggesting them to be ubiquitous in the
non-linear regime. |
Forecasts for warm dark matter from weakly lensed Type Ia supernovae: We investigate the possibility to have a constraint on the mass of thermal
warm dark matter (WDM) particle from the expected data of the Wide Field
Infrared Survey Telescope (WFIRST) survey if all the dark matter is warm. For
this purpose we consider the lensing effect of large scale structure based on
the warm dark matter scenario on the apparent magnitude of SNe Ia. We use
HALOFIT as non-linear matter power spectrum and the variance of PDF. We preform
a Fisher matrix analysis and obtain the lower bound of $m_{\rm WDM}>0.167$keV. | Testing Inflation and Curvaton Scenarios with CMB Distortions: Prior to recombination, Silk damping causes the dissipation of energy from
acoustic waves into the monopole of the Cosmic Microwave Background (CMB),
resulting in spectral distortions. These can be used to probe the primordial
scalar power spectrum on smaller scales than it is possible with CMB
anisotropies. An enhancement of power on these scales is nevertheless required
for the resulting distortions to be detectable by future experiments like
PIXIE. In this paper, we examine all 49 single-field inflation models listed by
Martin et al. in the Encyclopaedia Inflationaris [1] and find that only one of
these may lead to a detectable level of distortions in a tuned region of its
parameter space, namely the original hybrid model. Three effective multi-field
scenarios are also studied: with softly and suddenly turning trajectories, and
with a mild waterfall trajectory. Softly turning trajectories do not induce
distortions at any detectable level, whereas a sudden turn in the field space
or a mild waterfall trajectory predicts a peak (plus damped oscillations in the
sudden turn case) in the scalar power spectrum, which can lead to an observable
amount of CMB distortions. Finally, another scenario leading to potentially
detectable distortions involves a curvaton whose blue spectrum is subdominant
on CMB angular scales and overtakes the inflaton spectrum on smaller scales. In
this case however, we show that the bounds from ultra compact minihaloes are
not satisfied. Expectations for an ultimate PRISM-class experiment
characterized by an improvement in sensitivity by a factor of ten are discussed
for some models. |
Recovering MOND from extended metric theories of gravity: We show that the Modified Newtonian Dynamics (MOND) regime can be fully
recovered as the weak-field limit of a particular theory of gravity formulated
in the metric approach. This is possible when Milgrom's acceleration constant
is taken as a fundamental quantity which couples to the theory in a very
consistent manner. As a consequence, the scale invariance of the gravitational
interaction is naturally broken. In this sense, Newtonian gravity is the
weak-field limit of general relativity and MOND is the weak-field limit of that
particular extended theory of gravity. We also prove that a Noether's symmetry
approach to the problem yields a conserved quantity coherent with this
relativistic MONDian extension. | Narrow absorption line variability in repeat quasar observations from
the Sloan Digital Sky Survey: We present the results from a time domain study of absorption lines detected
in quasar spectra with repeat observations from the Sloan Digital Sky Survey
Data Release 7 (SDSS DR7). Beginning with over 4500 unique time separation
baselines of various absorption line species identified in the SDSS DR7 quasar
spectra, we create a catalogue of 2522 quasar absorption line systems with two
to eight repeat observations, representing the largest collection of unbiased
and homogeneous multi-epoch absorption systems ever published. To investigate
these systems for time variability of narrow absorption lines, we refine this
sample based on the reliability of the system detection, the proximity of
pixels with bright sky contamination to individual absorption lines, and the
quality of the continuum fit. Variability measurements of this sub-sample based
on the absorption line equivalent widths yield a total of 33 systems with
indications of significantly variable absorption strengths on time-scales
ranging from one day to several years in the rest frame of the absorption
system. Of these, at least 10 are from a class known as intervening absorption
systems caused by foreground galaxies along the line of sight to the background
quasar. This is the first evidence of possible absorption line variability
detected in intervening systems, and their short time-scale variations suggest
that small-scale structures (~10-100 au) are likely to exist in their host
foreground galaxies. |
Planck 2018 results. V. CMB power spectra and likelihoods: This paper describes the 2018 Planck CMB likelihoods, following a hybrid
approach similar to the 2015 one, with different approximations at low and high
multipoles, and implementing several methodological and analysis refinements.
With more realistic simulations, and better correction and modelling of
systematics, we can now make full use of the High Frequency Instrument
polarization data. The low-multipole 100x143 GHz EE cross-spectrum constrains
the reionization optical-depth parameter $\tau$ to better than 15% (in
combination with with the other low- and high-$\ell$ likelihoods). We also
update the 2015 baseline low-$\ell$ joint TEB likelihood based on the Low
Frequency Instrument data, which provides a weaker $\tau$ constraint. At high
multipoles, a better model of the temperature-to-polarization leakage and
corrections for the effective calibrations of the polarization channels
(polarization efficiency or PE) allow us to fully use the polarization spectra,
improving the constraints on the $\Lambda$CDM parameters by 20 to 30% compared
to TT-only constraints. Tests on the modelling of the polarization demonstrate
good consistency, with some residual modelling uncertainties, the accuracy of
the PE modelling being the main limitation. Using our various tests,
simulations, and comparison between different high-$\ell$ implementations, we
estimate the consistency of the results to be better than the 0.5$\sigma$
level. Minor curiosities already present before (differences between $\ell$<800
and $\ell$>800 parameters or the preference for more smoothing of the $C_\ell$
peaks) are shown to be driven by the TT power spectrum and are not
significantly modified by the inclusion of polarization. Overall, the legacy
Planck CMB likelihoods provide a robust tool for constraining the cosmological
model and represent a reference for future CMB observations. (Abridged) | Bandpass mismatch error for satellite CMB experiments I: Estimating the
spurious signal: Future Cosmic Microwave Background (CMB) satellite missions aim to use the
$B$ mode polarization to measure the tensor-to-scalar ratio $r$ with a
sensitivity of about $10^{-3}$. Achieving this goal will not only require
sufficient detector array sensitivity but also unprecedented control of all
systematic errors inherent to CMB polarization measurements. Since polarization
measurements derive from differences between observations at different times
and from different sensors, detector response mismatches introduce leakages
from intensity to polarization and thus lead to a spurious $B$ mode signal.
Because the expected primordial $B$ mode polarization signal is dwarfed by the
known unpolarized intensity signal, such leakages could contribute
substantially to the final error budget for measuring $r.$ Using simulations we
estimate the magnitude and angular spectrum of the spurious $B$ mode signal
resulting from bandpass mismatch between different detectors. It is assumed
here that the detectors are calibrated, for example using the CMB dipole, so
that their sensitivity to the primordial CMB signal has been perfectly matched.
Consequently the mismatch in the frequency bandpass shape between detectors
introduces difference in the relative calibration of galactic emission
components. We simulate using a range of scanning patterns being considered for
future satellite missions. We find that the spurious contribution to $r$ from
reionization bump on large angular scales ($\ell < 10$) is $\approx 10^{-3}$
assuming large detector arrays and 20 percent of the sky masked. We show how
the amplitude of the leakage depends on the angular coverage per pixels that
results from the scan pattern. |
X-ray analysis of the Planck-detected triplet-cluster system PLCK
G334.8-38: We conducted an X-ray analysis of one of the two Planck-detected
triplet-cluster systems, PLCK G334.8-38.0, with a $\sim100$~ks deep XMM-Newton
data. We find that the system has a redshift of $z=0.37\pm{0.01}$ but the
precision of the X-ray spectroscopy for two members is too low to rule out a
projected triplet system, demanding optical spectroscopy for further
investigation. In projection, the system looks almost like an equilateral
triangle with an edge length of $\sim2.0\,\mathrm{Mpc}$, but masses are very
unevenly distributed ($M_{500} \sim [2.5,0.7,0.3] \times
10^{14}\,\mathrm{M_{\odot}}$ from bright to faint). The brightest member
appears to be a relaxed cool-core cluster and is more than twice as massive as
both other members combined. The second brightest member appears to be a
disturbed non-cool-core cluster and the third member was too faint to make any
classification. None of the clusters have an overlapping $R_{500}$ region and
no signs of cluster interaction were found; however, the XMM-Newton data alone
are probably not sensitive enough to detect such signs, and a joint analysis of
X-ray and the thermal Sunyaev-Zeldovich effect (tSZ) is needed for further
investigation, which may also reveal the presence of the warm-hot intergalactic
medium (WHIM) within the system. The comparison with the other Planck-detected
triplet-cluster-system (PLCK G214.6+36.9) shows that they have rather different
configurations, suggesting rather different merger scenarios, under the
assumption that they are both not simply projected triplet systems. | Holographic dark energy: constraints on the interaction from diverse
observational data sets: The present work deals with holographic dark energy models with Hubble
horizon as the infra-red cut-off. The interaction rate between dark energy and
dark matter has been reconstructed with three different choices of the
interaction term. It is shown that the coupling parameter of the interaction
term should evolve with redshift to allow the successful transition from
decelerated to accelerated phase of expansion. Constraints on the model
parameters are obtained from Markov Chain Monte Carlo (MCMC) analysis using the
supernova distance modulus data and observational measurements of the Hubble
parameter. Results show that the model with the coupling parameter increasing
with redshift (z) or equivalently decreasing with the evolution, are ruled out.
On the other hand, coupling parameters, increasing or slowly varying with the
evolution, are consistent with the observed evolution scenario. A Bayesian
evidence calculation has been carried out for statistical selection of the
reconstructed models. Though the kinematical parameters are well behaved for
these models, the physical variables which determine the nature of the
components in the matter sector, are not at all realistic. We have concluded
that the existence of spatial curvature is essential for this particular type
of dark energy models. |
Magnetization of the intergalactic medium in the IllustrisTNG
simulations: the importance of extended, outflow-driven bubbles: We study the effects of galaxy formation physics on the magnetization of the
intergalactic medium (IGM) using the IllustrisTNG simulations. We demonstrate
that large-scale regions affected by the outflows from galaxies and clusters
contain magnetic fields that are several orders of magnitude stronger than in
unaffected regions with the same electron density. Moreover, like magnetic
fields amplified inside galaxies, these magnetic fields do not depend on the
primordial seed, i.e. the adopted initial conditions for magnetic field
strength. We study the volume filling fraction of these strong field regions
and their occurrence in random lines of sight. As a first application, we use
these results to put bounds on the photon-axion conversion from spectral
distortion of the CMB. As photon-axion coupling grows with energy, stronger
constraints could potentially be obtained using data on the propagation of
gamma-ray photons through the IGM. Finally, we also briefly discuss potential
applications of our results to the Faraday Rotation measurements. | Distortions in the Surface of Last Scattering: The surface of last scattering of the photons in the cosmic microwave
background is not a spherical shell. Apart from its finite width, each photon
experiences a different gravitational potential along its journey to us,
leading to different travel times in different directions. Since all photons
were released at the same cosmic time, the photons with longer travel times
started farther away from us than those with shorter times. Thus, the surface
of last scattering is corrugated, a deformed spherical shell. We present an
estimator quadratic in the temperature and polarization fields that could
provide a map of the time delays as a function of position on the sky. The
signal to noise of this map could exceed unity for the dipole, thereby
providing a rare insight into the universe on the largest observable scales. |
Effective field theory search for high-energy nuclear recoils using the
XENON100 dark matter detector: We report on WIMP search results in the XENON100 detector using a
non-relativistic effective field theory approach. The data from science run II
(34 kg $\times$ 224.6 live days) was re-analyzed, with an increased recoil
energy interval compared to previous analyses, ranging from $(6.6 -
240)~\mathrm{keV_\mathrm{nr}}$. The data is found to be compatible with the
background-only hypothesis. We present 90% confidence level exclusion limits on
the coupling constants of WIMP-nucleon effective operators using a binned
profile likelihood method. We also consider the case of inelastic WIMP
scattering, where incident WIMPs may up-scatter to a higher mass state, and set
exclusion limits on this model as well. | Weak Lensing by Minifilament or Minivoid as the Origin of Flux-ratio
Anomalies in Lensed Quasar MG0414+0534: We explore the weak lensing effects by ministructures in the line-of-sight in
a quadruply lensed quasar MG0414+0534 that shows an anomaly in the flux-ratios.
We find that the observed flux-ratio anomaly can be explained by a presence of
either a minifilament or a minivoid in the line-of-sight with a surface mass
density of the order of 10^(8-9) h^(-1) solar mass /arcsec^2 without taking
into account any subhalos in the lensing galaxy. The astrometric perturbation
by a possible minifilament/minivoid is <~ 0.001 arcsec and the amplitudes of
convergence perturbations due to these perturbers are ~ 0.004-0.008 at the
place of an image that shows anomaly. In order to discriminate models with the
line-of-sight ministructures from those with a subhalo(s) in the lensing
galaxy, we need to precisely measure the projected convergence and shear around
the lensing galaxy. The differential magnification effect could break the model
degeneracy if the source size is > ~100 pc. Observation at the submillimeter
band using interferometers will enable us to determine the origin of anomalies
in the flux ratios. |
Using the XMM Optical Monitor to Study Cluster Galaxy Evolution: We explore the application of XMM-Newton Optical Monitor (XMM-OM) ultraviolet
(UV) data to study galaxy evolution. Our sample is constructed as the
intersection of all Abell clusters with z < 0.05 and having archival XMM-OM
data in either the UVM2 or UVW1 filters, plus optical and UV photometry from
the Sloan Digital Sky Survey and GALEX, respectively. The eleven resulting
clusters include 726 galaxies with measured redshifts, 520 of which have
redshifts placing them within their parent Abell clusters. We develop
procedures for manipulating the XMM-OM images and measuring galaxy photometry
from them, and confirm our results via comparison with published catalogs.
Color magnitude diagrams (CMDs) constructed using the XMM-OM data along with
SDSS optical data show promise for evolutionary studies, with good separation
between red and blue sequences and real variation in the width of the red
sequence that is likely indicative of differences in star formation history.
This is particularly true for UVW1 data, as the relative abundance of data
collected using this filter and its depth make it an attractive choice.
Available tools that use stellar synthesis libraries to fit the UV and optical
photometric data may also be used, thereby better describing star formation
history within the past Gyr and providing estimates of total stellar mass that
include contributions from young stars. Finally, color-color diagrams that
include XMM-OM UV data appear useful to the photometric identification of both
extragalactic and stellar sources. | Cosmological implications of electromagnetically interacting dark
matter: milli-charged particles and atoms with singly and doubly charged dark
matter: While the behavior of the dominant component of the dark matter is reasonably
well established by cosmological observables, its particle nature and
interactions with the rest of the matter are not known. We consider three dark
matter models that admit electromagnetic interaction between baryons and dark
matter: (a) milli-charged particle (CCDM) of charge $q_{\rm ccdm}$ and mass
$m_{\rm ccdm}$, (b) a neutral atom of two charged particles of mass $m_{\rm
dd}$ (DD), and (c) a neutral atom of doubly charged particle and helium nucleus
(HeD). We derive and discuss in detail the formation, stability, and
interaction of these atoms with baryons. We derive the implications of this new
interaction in the tight-coupling approximation, which allows us to
analytically gauge their impact on the matter power spectrum and CMB
anisotropy. We incorporate this new interaction into the publicly-available
code CLASS to obtain numerical results. We compare our results with Planck 2018
data to constrain the fraction of interacting dark matter. For the range of
allowed astrophysical parameters, the HeD atom yields the results of
$\Lambda$CDM model for $k < 1 \, \rm Mpc^{-1}$, and hence its fraction is not
constrained by CMB anisotropy data which is sensitive to $k < 0.2 \, \rm
Mpc^{-1}$. For $m_{\rm dd} \gtrsim 25 \, \rm GeV$, the DD atom is also not
constrained by CMB data. For $m_{\rm dd} = 10 \, \rm GeV$, the CMB data
constrains the fraction of DD atoms to be smaller than 4% of the total CDM
component. For $q_{\rm ccdm} = 10^{-6}e$ and $m_{\rm ccdm} = 50 \, \rm MeV$,
the CCDM fraction is constrained to be less than 1%. |
Time variation of the Equation of State for Dark Energy: The time variation of the equation of state ($w_Q$) for the dark energy is
analyzed by the current values of parameters $\Omega_Q $, $w_Q $ and their time
derivatives. In the future, detailed feature of the dark energy could be
observed, so we have considered the second derivatives of $w_Q$ for two types
of potential: One is an inverse power-law type ($V=M^{4+\alpha}/Q^{\alpha}$)
and the other is an exponential one ($V=M^4\exp{(\beta M/Q)}$). The first
derivative $dw_Q/da$ and the second derivative $d^2 w_Q/da^2$ for both
potentials are derived. The first derivative is estimated by the observed two
parameters $\Delta=w_Q+1$ and $\Omega_Q$, with the assuming for $Q_0$. In the
limit $\Delta \rightarrow 0$, the first derivative is null and, under the
tracker approximation, the second derivative also becomes null. For the inverse
power potential $V=M^{4+\alpha}/Q^{\alpha}$, the observed first and second
derivatives are used to determine the potential parameter $M$ and $\alpha$. For
the potential of $V=M^4\exp{(\beta M/Q)}$, the second derivative is estimated
by the observed parameters $\Delta$, $\Omega_Q$ and $dw_Q/da$. | Multi wavelength cross-correlation analysis of the simulated cosmic web: We used magneto-hydrodynamical cosmological simulations to investigate the
cross-correlation between different observables (i.e. X-ray emission,
Sunyaev-Zeldovich signal at 21 cm, HI temperature decrement, diffuse
synchrotron emission and Faraday Rotation) as a probe of the diffuse matter
distribution in the cosmic web. We adopt an uniform and simplistic approach to
produce synthetic observations at various wavelengths, and we compare the
detection chances of different combinations of observables correlated with each
other and with the underlying galaxy distribution in the volume. With presently
available surveys of galaxies and existing instruments, the best chances to
detect the diffuse gas in the cosmic web outside of halos is by
cross-correlating the distribution of galaxies with Sunyaev-Zeldovich
observations. We also find that the cross-correlation between the galaxy
network and the radio emission or the Faraday Rotation can already be used to
limit the amplitude of extragalactic magnetic fields, well outside of the
cluster volume usually explored by existing radio observations, and to probe
the origin of cosmic magnetism with the future generation of radio surveys. |
The Evolution of 21-cm Structure (EOS): public, large-scale simulations
of Cosmic Dawn and Reionization: We introduce the Evolution of 21-cm Structure (EOS) project: providing
periodic, public releases of the latest cosmological 21-cm simulations. 21-cm
interferometry is set to revolutionize studies of the Cosmic Dawn (CD) and
epoch of reionization (EoR), eventually resulting in 3D maps of the first
billion years of our Universe. Progress will depend on sophisticated data
analysis pipelines, which are in turn tested on large-scale mock observations.
Here we present the 2016 EOS data release, consisting of the largest (1.6 Gpc
on side with a 1024^3 grid), public 21-cm simulations of the CD and EoR. We
include calibrated, sub-grid prescriptions for inhomogeneous recombinations and
photo-heating suppression of star formation in small mass galaxies. We present
two simulation runs that approximately bracket the contribution from faint
unseen galaxies. From these two extremes, we predict that the duration of
reionization (defined as a change in the mean neutral fraction from 0.9 to 0.1)
should be between 2.7 < Delta z < 5.7. The large-scale 21-cm power during the
advanced EoR stages can be different by up to a factor of ~10, depending on the
model. This difference has a comparable contribution from: (i) the typical bias
of sources; and (ii) a more efficient negative feedback in models with an
extended EoR driven by faint galaxies. We also make detectability forecasts.
With a 1000h integration, HERA and SKA1-low should achieve a signal-to-noise of
~few-hundreds throughout the EoR/CD, while in the maximally optimistic scenario
of perfect foreground cleaning, all instruments should make a statistical
detection of the cosmic signal. We also caution that our ability to clean
foregrounds determines the relative performance of narrow/deep vs. wide/shallow
surveys expected with SKA1. Our 21-cm power spectra, simulation outputs and
visualizations are publicly available. | Analytical Galaxy Profiles for Photometric and Lensing Analysis: This article introduces a family of analytical functions of the form x^{\nu}
K_{\nu}(x), where K_{\nu} is the incomplete Bessel function of the third kind.
This family of functions can describe the density profile, projected and
integrated light profiles and the gravitational potentials of galaxies. For the
proper choice of parameters, these functions accurately approximate Sersic
functions over a range of indices and are good fits to galaxy light profiles.
With an additional parameter corresponding to a galaxy core radius, these
functions can fit galaxy like M87 over a factor of 100,000 in radius. Unlike
Sersic profiles, these functions have simple analytical 2-dimensional and
3-dimensional Fourier transforms, so they are easily convolved with spatially
varying point spread function and are well suited for photometric and lensing
analysis. We use these functions to estimate the effects of seeing on lensing
measurements and show that high S/N measurements, even when the PSF is larger
than the galaxy effective radius, should be able to recover accurate estimates
of lensing distortions by weighting light in the outer isophotes that are less
effected by seeing. |
N-body simulations of structure formation in thermal inflation
cosmologies: Thermal inflation models (which feature two inflationary stages) can display
damped primordial curvature power spectra on small scales which generate damped
matter fluctuations. For a reasonable choice of parameters, thermal inflation
models naturally predict a suppression of the matter power spectrum on galactic
and sub-galactic scales, mimicking the effect of warm or interacting dark
matter. Matter power spectra in these models are also characterised by an
excess of power (w.r.t. the standard $\Lambda$CDM power spectrum) just below
the suppression scale. By running a suite of N-body simulations we investigate
the non-linear growth of structure in models of thermal inflation. We measure
the non-linear matter power spectrum and extract halo statistics, such as the
halo mass function, and compare these quantities with those predicted in the
standard $\Lambda$CDM model and in other models with damped matter
fluctuations. We find that the thermal inflation models considered here produce
measurable differences in the matter power spectrum from $\Lambda$CDM at
redshifts $z>5$, while the halo mass functions are appreciably different at all
redshifts. The halo mass function at $z=0$ for thermal inflation displays an
enhancement of around $\sim 20\%$ w.r.t. $\Lambda$CDM and a damping at lower
halo masses, with the position of the enhancement depending on the value of the
free parameter in the model. The enhancement in the halo mass function (w.r.t.
$\Lambda$CDM ) increases with redshift, reaching $\sim 40\%$ at $z=5$. We also
study the accuracy of the analytical Press-Schechter approach, using different
filters to smooth the density field, to predict halo statistics for thermal
inflation. We find that the predictions with the smooth-$k$ filter agree with
the simulation results over a wider range of halo masses than is the case with
other filters commonly used in the literature. | Constraining the dark-energy equation of state with cosmological data: Recently, the observed equation of state for dark energy appears to favor
values below $-1$. The tendency implies that the nature of dark energy may be
quite different from that of the cosmological constant. In view of the
adjustment on the equation of state keeps decreasing, the introduction of the
phantom energy seems inevitable. By employing observational constraints from
supernovae and from the acoustic scale in which the accuracy of the data has
become extraordinary, we apply a phenomenological scenario to be acquainted
with the evolution of our universe. The demonstration on the constrained
unfolding of the phantom energy shows the model has high consistency with the
current observation. |
The Cosmological Analysis of the SDSS/BOSS data from the Effective Field
Theory of Large-Scale Structure: The Effective Field Theory of Large-Scale Structure (EFTofLSS) is a formalism
that allows us to predict the clustering of Cosmological Large-Scale Structure
in the mildly non-linear regime in an accurate and reliable way. After
validating our technique against several sets of numerical simulations, we
perform the analysis for the cosmological parameters of the DR12 BOSS data. We
assume $\Lambda$CDM, a fixed value of the baryon/dark-matter ratio,
$\Omega_b/\Omega_c$, and of the tilt of the primordial power spectrum, $n_s$,
and no significant input from numerical simulations. By using the one-loop
power spectrum multipoles, we measure the primordial amplitude of the power
spectrum, $A_s$, the abundance of matter, $\Omega_m$, and the Hubble parameter,
$H_0$, to about $13\%$, $3.2\%$ and $3.2\%$ respectively, obtaining
$\ln(10^{10}As)=2.72\pm 0.13$, $\Omega_m=0.309\pm 0.010$, $H_0=68.5\pm 2.2$
km/(s Mpc) at 68\% confidence level. If we then add a CMB prior on the sound
horizon, the error bar on $H_0$ is reduced to $1.6\%$. These results are a
substantial qualitative and quantitative improvement with respect to former
analyses, and suggest that the EFTofLSS is a powerful instrument to extract
cosmological information from Large-Scale Structure. | Machine Learning and cosmographic reconstructions of quintessence and
the Swampland conjectures: We present model independent reconstructions of quintessence and the
Swampland conjectures (SC) using both Machine Learning (ML) and cosmography. In
particular, we demonstrate how the synergies between theoretical analyses and
ML can provide key insights on the nature of dark energy and modified gravity.
Using the Hubble parameter $H(z)$ data from the cosmic chronometers we find
that the ML and cosmography reconstructions of the SC are compatible with
observations at low redshifts. Finally, including the growth rate data
$f\sigma_8(z)$ we perform a model independent test of modified gravity
cosmologies through two phase diagrams, namely $H-f\sigma_8$ and
$\eta-f\sigma_8$, where the anisotropic stress parameter $\eta$ is obtained via
the $E_g$ statistics, which is related to gravitational lensing data. While the
first diagram is consistent within the errors with the $\Lambda$CDM model, the
second one has a $\sim 2\sigma$ deviation of the anisotropic stress from unity
at $z\sim 0.3$ and a $\sim 4\sigma$ deviation at $z\sim 0.9$, thus pointing
toward mild deviations from General Relativity, which could be further tested
with upcoming large-scale structure surveys. |
Non-Gaussianity from violation of slow-roll in multiple inflation: Multiple inflation is a model based on N=1 supergravity wherein there are
sudden changes in the mass of the inflaton because it couples to 'flat
direction' scalar fields which undergo symmetry breaking phase transitions as
the universe cools. The resulting brief violations of slow-roll evolution
generate a non-gaussian signal which we find to be oscillatory and yielding
f_NL ~ 5-20. This is potentially detectable by e.g. Planck but would require
new bispectrum estimators to do so. We also derive a model-independent result
relating the period of oscillations of a phase transition during inflation to
the period of oscillations in the primordial curvature perturbation generated
by the inflaton. | Cosmological constraints on post-Newtonian parameters in effectively
massless scalar-tensor theories of gravity: We study the cosmological constraints on the variation of the Newton's
constant and on post-Newtonian parameters for simple models of scalar-tensor
theory of gravity beyond the extended Jordan-Brans-Dicke theory. We restrict
ourselves to an effectively massless scalar field with a potential $V \propto
F^2$, where $F(\sigma)=N_{pl}^2+\xi\sigma^2$ is the coupling to the Ricci
scalar considered. We derive the theoretical predictions for cosmic microwave
background (CMB) anisotropies and matter power spectra by requiring that the
effective gravitational strength at present is compatible with the one measured
in a Cavendish-like experiment and by assuming adiabatic initial condition for
scalar fluctuations. When comparing these models with $Planck$ 2015 and a
compilation of baryonic acoustic oscilation (BAO) data, all these models
accomodate a marginalized value for $H_0$ higher than in $\Lambda$CDM. We find
no evidence for a statistically significant deviation from Einstein's general
relativity. We find $\xi < 0.064$ ($|\xi| < 0.011$) at 95 % CL for $\xi > 0$
(for $\xi < 0$, $\xi \ne -1/6$). In terms of post-Newtonian parameters, we find
$0.995 < \gamma_{\rm PN} < 1$ and $0.99987 < \beta_{\rm PN} < 1$ ($0.997 <
\gamma_{\rm PN} < 1$ and $1 < \beta_{\rm PN} < 1.000011$) for $\xi >0$ (for
$\xi < 0$). For the particular case of the conformal coupling, i.e. $\xi=-1/6$,
we find constraints on the post-Newtonian parameters of similar precision to
those within the Solar System. |
Hydro-chemical study of the evolution of interstellar pre-biotic
molecules during the collapse of molecular clouds: One of the stumbling blocks for studying the evolution of interstellar
molecules is the lack of adequate knowledge of the rate co-efficients of
various reactions which take place in the Interstellar medium and molecular
clouds. Some of the theoretical models of rate coefficients do exist in the
literature for computing abundances of the complex pre-biotic molecules. So far
these have been used to study the abundances of these molecules in space.
However, in order to obtain more accurate final compositions in these media, we
find out the rate coefficients for the formation of some of the most important
interstellar pre-biotic molecules by using quantum chemical theory. We use
these rates inside our hydro-chemical model to find out the chemical evolution
and the final abundances of the pre-biotic species during the collapsing phase
of a proto-star. We find that a significant amount of various pre-biotic
molecules could be produced during the collapsing phase of a proto-star. We
study extensively the formation these molecules via successive neutral-neutral
and radical-radical/radical-molecular reactions. We present the time evolution
of the chemical species with an emphasis on how the production of these
molecules varies with the depth of a cloud. We compare the formation of adenine
in the interstellar space using our rate-coefficients and using those obtained
from the existing theoretical models. Formation routes of the pre-biotic
molecules are found to be highly dependent on the abundances of the reactive
species and the rate coefficients involved in the reactions. Presence of grains
strongly affect the abundances of the gas phase species. We also carry out a
comparative study between different pathways available for the synthesis of
adenine, alanine, glycine and other molecules considered in our network. | Extended Analysis of Neutrino-Dark Matter Interactions with Small-Scale
CMB Experiments: We explore an extension of the standard $\Lambda$CDM model by including an
interaction between neutrinos and dark matter, and making use of the ground
based telescope data of the Cosmic Microwave Background (CMB) from the Atacama
Cosmology Telescope (ACT). An indication for a non-zero coupling between dark
matter and neutrinos (both assuming a temperature independent and $T^2$
dependent cross-section) is obtained at the 1$\sigma$ level coming from the ACT
CMB data alone and when combined with the Planck CMB and Baryon Acoustic
Oscillations (BAO) measurements. This result is confirmed by both fixing the
effective number of relativistic degrees of freedom in the early Universe to
the Standard Model value of $N_{\rm eff}=3.044$, and allowing $N_{\rm eff}$ to
be a free cosmological parameter. Furthermore, when performing a Bayesian model
comparison, the interacting $\nu$DM (+$N_{\rm eff}$) scenario is mostly
preferred over a baseline $\Lambda$CDM (+$N_{\rm eff}$) cosmology. The
preferred value is then used as a benchmark and the potential implications of
dark matter's interaction with a sterile neutrino are discussed. |
SweetSpot: Near-Infrared Observations of Thirteen Type Ia Supernovae
from a New NOAO Survey Probing the Nearby Smooth Hubble Flow: We present 13 Type Ia supernovae (SNe Ia) observed in the restframe
near-infrared (NIR) from 0.02 < z < 0.09 with the WIYN High-resolution Infrared
Camera (WHIRC) on the WIYN 3.5-m telescope. With only 1-3 points per light
curve and a prior on the time of maximum from the spectrum used to type the
object we measure an H-band dispersion of spectroscopically normal SNe Ia of
0.164 mag. These observations continue to demonstrate the improved standard
brightness of SNe Ia in H-band even with limited data. Our sample includes two
SNe Ia at z ~ 0.09, which represent the most distant restframe NIR H-band
observations published to date.
This modest sample of 13 NIR SNe Ia represent the pilot sample for
"SweetSpot" - a three-year NOAO Survey program that will observe 144 SNe Ia in
the smooth Hubble flow. By the end of the survey we will have measured the
relative distance to a redshift of z ~ 0.05 to 1%. Nearby Type Ia supernova (SN
Ia) observations such as these will test the standard nature of SNe Ia in the
restframe NIR, allow insight into the nature of dust, and provide a critical
anchor for future cosmological SN Ia surveys at higher redshift. | CO(1-0) detection of molecular gas in the massive Spiderweb Galaxy (z=2): The high-redshift radio galaxy MRC 1138-262 (`Spiderweb Galaxy'; z = 2.16),
is one of the most massive systems in the early Universe and surrounded by a
dense `web' of proto-cluster galaxies. Using the Australia Telescope Compact
Array, we detected CO(1-0) emission from cold molecular gas -- the raw
ingredient for star formation -- across the Spiderweb Galaxy. We infer a
molecular gas mass of M(H2) = 6x10^10 M(sun) (for M(H2)/L'(CO)=0.8). While the
bulk of the molecular gas coincides with the central radio galaxy, there are
indications that a substantial fraction of this gas is associated with
satellite galaxies or spread across the inter-galactic medium on scales of tens
of kpc. In addition, we tentatively detect CO(1-0) in the star-forming
proto-cluster galaxy HAE 229, 250 kpc to the west. Our observations are
consistent with the fact that the Spiderweb Galaxy is building up its stellar
mass through a massive burst of widespread star formation. At maximum star
formation efficiency, the molecular gas will be able to sustain the current
star formation rate (SFR ~ 1400 M(sun)/yr, as traced by Seymour et al.) for
about 40 Myr. This is similar to the estimated typical lifetime of a major
starburst event in infra-red luminous merger systems. |
Axion Dark Matter Induced Cosmic Microwave Background $B$-modes: It was known that isocurvature perturbation of a nearly massless cosmological
axion field can lead to rotation of $E$-mode polarization into $B$-mode
polarization in the cosmic microwave background (CMB) by the presence of a
parity violating coupling of the field to the topological density of
electromagnetism, resulting in a phenomenon known as anisotropic cosmic
birefringence. In this {\em Letter}, we propose a new source of anisotropic
cosmic birefringence induced by dark matter adiabatic density perturbation. If
dark matter is ultralight axions that carry a coupling to photon, its adiabatic
density fluctuations will induce anisotropic cosmic birefringence with a
blue-tilted rotation power spectrum, thus generating CMB $B$-mode polarization
on sub-degree angular scales. Using current POLARBEAR and SPTPol $B$-mode
polarization data, we derive a constraint on the axion-photon coupling strength
($\beta$) and the axion mass ($m$), $\beta^2 (10^{-22}{\rm eV}/m)^2 < 8\times
10^{15}$. It is shown that the birefringence $B$ modes can dominate over CMB
lensing $B$ modes at high $l$, manifesting as an excess power for $l>1500$ in
future CMB lensing $B$-mode searches. In addition, we derive the
lensing-rotation cross correlation that can be a potential test to the present
model. | Gravitational Wave mergers as tracers of Large Scale Structures: Clustering measurements of Gravitational Wave (GW) mergers in Luminosity
Distance Space can be used in the future as a powerful tool for Cosmology. We
consider tomographic measurements of the Angular Power Spectrum of mergers both
in an Einstein Telescope-like detector network and in some more advanced
scenarios (more sources, better distance measurements, better sky
localization). We produce Fisher forecasts for both cosmological (matter and
dark energy) and merger bias parameters. Our fiducial model for the number
distribution and bias of GW events is based on results from hydrodynamical
simulations. The cosmological parameter forecasts with Einstein Telescope are
less powerful than those achievable in the near future via galaxy clustering
observations with, e.g., Euclid. However, in the more advanced scenarios we see
significant improvements. Moreover, we show that bias can be detected at high
statistical significance. Regardless of the specific constraining power of
different experiments, many aspects make this type of analysis interesting
anyway. For example, compact binary mergers detected by Einstein Telescope will
extend up to very high redshifts. Furthermore, Luminosity Distance Space
Distortions in the GW analysis have a different structure with respect to
Redshift-Space Distortions in galaxy catalogues. Finally, measurements of the
bias of GW mergers can provide useful insight into their physical nature and
properties. |
Cosmological implications of different baryon acoustic oscillation data: In this work, we explore the cosmological implications of different baryon
acoustic oscillation (BAO) data, including the BAO data extracted by using the
spherically averaged one-dimensional galaxy clustering (GC) statistics
(hereafter BAO1) and the BAO data obtained by using the anisotropic
two-dimensional GC statistics (hereafter BAO2). To make a comparison, we also
take into account the case without BAO data (hereafter NO BAO). Firstly, making
use of these BAO data, as well as the SNLS3 type Ia supernovae sample and the
Planck distance priors data, we give the cosmological constraints of the
$\Lambda$CDM, the $w$CDM, and the Chevallier-Polarski-Linder (CPL) model. Then,
we discuss the impacts of different BAO data on cosmological consquences,
including its effects on parameter space, equation of state (EoS), figure of
merit (FoM), deceleration-acceleration transition redshift, Hubble parameter
$H(z)$, deceleration parameter $q(z)$, statefinder hierarchy $S^{(1)}_3(z)$,
$S^{(1)}_4(z)$ and cosmic age $t(z)$. We find that: (1) NO BAO data always give
a smallest fractional matter density $\Omega_{m0}$, a largest fractional
curvature density $\Omega_{k0}$ and a largest Hubble constant $h$; in contrast,
BAO1 data always give a largest $\Omega_{m0}$, a smallest $\Omega_{k0}$ and a
smallest $h$. (2) For the $w$CDM and the CPL model, NO BAO data always give a
largest EoS $w$; in contrast, BAO2 data always give a smallest $w$. (3)
Compared with the case of BAO1, BAO2 data always give a slightly larger FoM,
and thus can give a cosmological constraint with a slightly better accuracy.
(4) The impacts of different BAO data on the cosmic evolution and the comic age
are very small, and can not be distinguished by using various dark energy
diagnosis and the cosmic age data. | Primordial magnetic helicity evolution with a homogeneous magnetic field
from inflation: Motivated by a scenario of magnetogenesis in which a homogeneous magnetic
field is generated during inflation, we study the magnetohydrodynamic evolution
of the primordial plasma motions for two kinds of initial conditions -- (i) a
spatially homogeneous field with an unlimited correlation length, and (ii) a
zero flux scale-invariant statistically homogeneous magnetic field. In both
cases, we apply, for a short initial time interval, monochromatic forcing at a
certain wave number so that the correlation length is finite, but much smaller
than the typical length scale of turbulence. In particular, we investigate the
decay of nonhelical and helical hydromagnetic turbulence. We show that, in the
presence of a homogeneous magnetic field, the decay of helical and nonhelical
small-scale fields can occur rapidly. This is a special property of a system
with a perfectly homogeneous magnetic field, which is sometimes considered as a
local approximation to a slowly varying background field. It can never change
and acts as an imposed magnetic field. This is in a sharp contrast to the case
of a statistically homogeneous magnetic field, where we recover familiar decay
properties: a much slower decay of magnetic energy and a faster growth of the
correlation length, especially in the case with magnetic felicity. The result
suggests that a homogeneous magnetic field, if generated during inflation,
should persist under the influence of small-scale fields and could be the
origin of the large-scale magnetic field in the Universe. |
Dark energy with non-adiabatic sound speed: initial conditions and
detectability: Assuming that the universe contains a dark energy fluid with a constant
linear equation of state and a constant sound speed, we study the prospects of
detecting dark energy perturbations using CMB data from Planck,
cross-correlated with galaxy distribution maps from a survey like LSST. We
update previous estimates by carrying a full exploration of the mock data
likelihood for key fiducial models. We find that it will only be possible to
exclude values of the sound speed very close to zero, while Planck data alone
is not powerful enough for achieving any detection, even with lensing
extraction. We also discuss the issue of initial conditions for dark energy
perturbations in the radiation and matter epochs, generalizing the usual
adiabatic conditions to include the sound speed effect. However, for most
purposes, the existence of attractor solutions renders the perturbation
evolution nearly independent of these initial conditions. | Multiband Comparative Study of Optical Microvariability in RL vs. RQ
Quasars: We present the results of an optical multi-band (BVR) photometric monitoring
program of 22 core-dominated radio-loud quasars (CRLQs) and 22 radio-quiet
quasars (RQQs). The aim was to compare the properties of microvariability in
both types of quasars. We detected optical microvariability in 5 RQQs and 4
CRLQs. Our results confirm that microvariability in RQQs may be as frequent as
in CRLQs. In addition we compare microvariability duty cycles in different
bands. Finally, the implications for the origin of the microvariations are
briefly discussed. |
Discovery of a spiral-host episodic radio-galaxy: We report the discovery of a unique radio galaxy at z=0.137, which could
possibly be the second spiral-host large radio galaxy and also the second
triple-double episodic radio galaxy. The host galaxy shows signs of recent star
formation in the UV but is optically red and is the brightest galaxy of a
possible cluster. The outer relic radio lobes of this galaxy, separated by ~1
Mpc, show evidence of spectral flattening and a high fraction of linear
polarisation. We interpret that these relic lobes have experienced
re-acceleration of particles and compression of the magnetic field due to
shocks in the cluster outskirts. From the morphology of the relics and galaxy
distribution, we argue that re-acceleration is unlikely to be due to a
cluster-cluster merger and suggest the possibility of accretion shocks. The
source was identified from SDSS, GALEX, NVSS and FIRST survey data but we also
present follow up optical observations with the Lulin telescope and 325 MHz low
frequency radio observations with the GMRT. We briefly discuss the scientific
potential of this example in understanding the evolution of galaxies and
clusters by accretion, mergers, star formation, and AGN feedback. | Sparse Bayesian mass-mapping using trans-dimensional MCMC: Uncertainty quantification is a crucial step of cosmological mass-mapping
that is often ignored. Suggested methods are typically only approximate or make
strong assumptions of Gaussianity of the shear field. Probabilistic sampling
methods, such as Markov chain Monte Carlo (MCMC), draw samples form a
probability distribution, allowing for full and flexible uncertainty
quantification, however these methods are notoriously slow and struggle in the
high-dimensional parameter spaces of imaging problems. In this work we use, for
the first time, a trans-dimensional MCMC sampler for mass-mapping, promoting
sparsity in a wavelet basis. This sampler gradually grows the parameter space
as required by the data, exploiting the extremely sparse nature of mass maps in
wavelet space. The wavelet coefficients are arranged in a tree-like structure,
which adds finer scale detail as the parameter space grows. We demonstrate the
trans-dimensional sampler on galaxy cluster-scale images where the planar
modelling approximation is valid. In high-resolution experiments, this method
produces naturally parsimonious solutions, requiring less than 1% of the
potential maximum number of wavelet coefficients and still producing a good fit
to the observed data. In the presence of noisy data, trans-dimensional MCMC
produces a better reconstruction of mass-maps than the standard smoothed
Kaiser-Squires method, with the addition that uncertainties are fully
quantified. This opens up the possibility for new mass maps and inferences
about the nature of dark matter using the new high-resolution data from
upcoming weak lensing surveys such as Euclid. |
Geometrical constraints on curvature from galaxy-lensing
cross-correlations: Accurate constraints on curvature provide a powerful probe of inflation.
However, curvature constraints based on specific assumptions of dark energy may
lead to unreliable conclusions when used to test inflation models. To avoid
this, it is important to obtain constraints that are independent on assumptions
for dark energy. In this paper, we investigate such constraints on curvature
from the geometrical probe constructed from galaxy-lensing cross-correlations.
We study comprehensively the cross-correlations of galaxy with magnification,
measured from type Ia supernovae's brightnesses ("$g\kappa^{\rm SN}$"), with
shear ("$g\kappa^{\rm g}$"), and with CMB lensing ("$g\kappa^{\rm CMB}$"). We
find for the LSST and Stage IV CMB surveys, "$g\kappa^{\rm SN}$" ,
"$g\kappa^{\rm g}$" and "$g\kappa^{\rm CMB}$" can be detected with
signal-to-noise ratio $S/N=104,\ 2291,\ 1842$ respectively. When combined with
supernovae Hubble diagram ("SN") to constrain curvature, we find galaxy-lensing
cross-correlation becomes increasingly important with more degrees of freedom
allowed in dark energy. Without any priors, we obtain error on $\Omega_K$ of
$0.723$ from "SN + $g\kappa^{\rm SN}$", $0.0417$ from "SN + $g\kappa^{\rm g}$",
and $0.04$ from "SN + $g\kappa^{\rm g}$ + $g\kappa^{\rm CMB}$" for the LSST and
Stage IV CMB surveys. The last one is more competitive than a Stage IV BAO
survey ("BAO"). When galaxy-lensing cross-correlations are added to the
combined probe of "SN + BAO + CMB", where "CMB" stands for Planck measurement
for the CMB acoustic scale, we obtain constraint on $\Omega_K$ of $0.0013$,
which is a factor of 7 improvement from "SN + BAO + CMB". We study improvements
in these results from increasing the high redshift extension of supernovae. | Cosmological Covariance of Fast Radio Burst Dispersions: The dispersion of fast radio bursts (FRBs) is a measure of the large-scale
electron distribution. It enables measurements of cosmological parameters,
especially of the expansion rate and the cosmic baryon fraction. The number of
events is expected to increase dramatically over the coming years, and of
particular interest are bursts with identified host galaxy and therefore
redshift information.
In this paper, we explore the covariance matrix of the dispersion measure
(DM) of FRBs induced by the large-scale structure, as bursts from a similar
direction on the sky are correlated by long wavelength modes of the electron
distribution. We derive analytical expressions for the covariance matrix and
examine the impact on parameter estimation from the FRB dispersion measure -
redshift relation. The covariance also contains additional information that is
missed by analysing the events individually. For future samples containing over
$\sim300$ FRBs with host identification over the full sky, the covariance needs
to be taken into account for unbiased inference, and the effect increases
dramatically for smaller patches of the sky. Also forecasts must consider these
effects as they would yield too optimistic parameter constraints. Our procedure
can also be applied to the DM of the afterglow of Gamma Ray Bursts. |
Time Delay Cosmography: Analysis of Quadruply Lensed QSO SDSSJ1433 from
Wendelstein Observatory: The goal of this work is to obtain a Hubble constant estimate through the
study of the quadruply lensed, variable QSO SDSSJ1433+6007. To achieve this we
combine multi-filter, archival $\textit{HST}$ data for lens modelling and a
dedicated time delay monitoring campaign with the 2.1m Fraunhofer telescope at
the $\textit{Wendelstein Observatory}$. The lens modelling is carried out with
the public $\texttt{lenstronomy}$ Python package for each of the filters
individually. Through this approach, we find that the data in one of the
$\textit{HST}$ filters (F160W) contain a light contaminant, that would, if
remained undetected, have severely biased the lensing potentials and thus our
cosmological inference. After rejecting these data we obtain a combined
posterior for the Fermat potential differences from the lens modelling in the
remaining filters (F475X, F814W, F105W and F140W) with a precision of
$\sim6\%$. The analysis of the $\textit{g'}$-band Wendelstein light curve data
is carried out with a free-knot spline fitting method implemented in the public
Python $\texttt{PyCS3}$ tools. The precision of the time delays between the QSO
images has a range between 7.5 and 9.8$\%$ depending on the brightness of the
images and their time delay. We then combine the posteriors for the Fermat
potential differences and time delays. Assuming a flat $\Lambda$CDM cosmology,
we infer a Hubble parameter of
$H_0=76.6^{+7.7}_{-7.0}\frac{\mathrm{km}}{\mathrm{Mpc\;s}}$, reaching $9.6\%$
uncertainty for a single system. | The First Billion Years project - IV: Proto-galaxies reionising the
Universe: The contribution of stars in galaxies to cosmic reionisation depends on the
star formation history in the Universe, the abundance of galaxies during
reionisation, the escape fraction of ionising photons and the clumping factor
of the inter-galactic medium (IGM). We compute the star formation rate and
clumping factor during reionisation in a cosmological volume using a
high-resolution hydrodynamical simulation. We post-process the output with
detailed radiative transfer simulations to compute the escape fraction of
ionising photons. Together, this gives us the opportunity to assess the
contribution of galaxies to reionisation self-consistently. The strong mass and
redshift dependence of the escape fraction indicates that reionisation occurred
between z=15 and z=10 and was mainly driven by proto-galaxies forming in
dark-matter haloes with masses between 1e7 and 1e8 solar mass. More massive
galaxies that are rare at these redshifts and have significantly lower escape
fractions contribute less photons to the reionisation process than the
more-abundant low-mass galaxies. Star formation in the low-mass haloes is
suppressed by radiative feedback from reionisation, therefore these
proto-galaxies only contribute when the part of the Universe they live in is
still neutral. After z~10, massive galaxies become more abundant and provide
most of the ionising photons. In addition, we find that Population (Pop) III
stars are too short-lived and not frequent enough to have a major contribution
to reionisation. Although the stellar component of the proto-galaxies that
produce the bulk of ionising photons during reionisation is too faint to be
detected by the James Webb Space Telescope (JWST), these sources are brightest
in the H-alpha and Ly-alpha recombination lines, which will likely be detected
by JWST in deep surveys. |
Cosmological simulations of black hole growth: AGN luminosities and
downsizing: In this study, we present a detailed, statistical analysis of black hole
growth and the evolution of active galactic nuclei (AGN) using cosmological
hydrodynamic simulations run down to $z=0$. The simulations self-consistently
follow radiative cooling, star formation, metal enrichment, black hole growth
and associated feedback processes from both supernovae typeII/Ia and AGN. We
consider two simulation runs, one with a large co-moving volume of $(500\
\mathrm{Mpc})^3$ and one with a smaller volume of $(68\ \mathrm{Mpc})^3$ but
with a by a factor of almost 20 higher mass resolution. Consistently with
previous results, our simulations can widely match observed black hole
properties of the local Universe. Furthermore, our simulations can successfully
reproduce the evolution of the bolometric AGN luminosity function for both the
low-luminosity and the high-luminosity end up to $z=3.0$. In addition, the
smaller but higher resolution run is able to match the observational data of
the low bolometric luminosity end at higher redshifts $z=3-4$. We also perform
a direct comparison with the observed soft and hard X-ray luminosity functions
of AGN, including an empirical correction for a torus-level obscuration, and
find a similarly good agreement. These results nicely demonstrate that the
observed "anti-hierarchical" trend in the AGN number density evolution (i.e.
the number densities of luminous AGN peak at higher redshifts than those of
faint AGN) is self-consistently predicted by our simulations. Implications of
this downsizing behaviour on active black holes, their masses and
Eddington-ratios are discussed. Overall, the downsizing behaviour in the AGN
number density as a function of redshift can be mainly attributed to the
evolution of the gas density in the resolved vicinity of a (massive) black
hole. (shortened) | Probing the peak of the star formation rate density with the
extragalactic background light: The extragalactic background light (EBL), i.e., the diffuse meta-galactic
photon field in the ultraviolet to infrared, is dominated by the emission from
stars in galaxies. It is, therefore, intimately connected with the integrated
star formation rate density (SFRD). In this paper, the SFRD is constrained
using recent limits on the EBL density derived from observations of distant
sources of high and very-high energy gamma-rays. The stellar EBL contribution
is modeled utilizing simple stellar population spectra including dust
attenuation and emission. For modeling the SFRD up to z=4 a broken power law
function in z+1 is assumed. A wide range of values for the different model
parameters (SFRD(z), metallicity, dust absorption) is investigated and their
impact on the resulting EBL is studied. The calculated EBL densities are
compared with the specific EBL density limits and constraints on the SFRD are
derived. For the fiducial model, adopting a Chabrier initial mass function
(IMF) and a second power law index for the SFRD of beta=0.3, the SFRD is
constrained to <~ 0.1 M_solar yr^-1 Mpc^-3 and < 0.2 M_solar yr^-1 Mpc^-3 for a
redshift of z~1 and z~2, respectively. The limits for a redshift of z~1 are in
tension with SFRD measurements derived from instantaneous star formation
tracers. While the tension for the conservative fiducial model in this study is
not yet overly strong, the tension increases when applying plausible changes to
the model parameters, e.g., using a Salpeter instead of a Chabrier IMF or a
adopting a sub-solar metallicity. |
Cosmology Intertwined I: Perspectives for the Next Decade: The standard $\Lambda$ Cold Dark Matter cosmological model provides an
amazing description of a wide range of astrophysical and astronomical data.
However, there are a few big open questions, that make the standard model look
like a first-order approximation to a more realistic scenario that still needs
to be fully understood. In this Letter of Interest we will list a few important
goals that need to be addressed in the next decade, also taking into account
the current discordances present between the different cosmological probes, as
the Hubble constant $H_0$ value, the $\sigma_8 - S_8$ tension, and the
anomalies present in the Planck results. Finally, we will give an overview of
upgraded experiments and next-generation space-missions and facilities on
Earth, that will be of crucial importance to address all these questions. | Analysis of an iterative reconstruction method in comparison of the
standard reconstruction method: We present a detailed analysis of a new, iterative density reconstruction
algorithm. This algorithm uses a decreasing smoothing scale to better
reconstruct the density field in Lagrangian space. We implement this algorithm
to run on the Quijote simulations, and extend it to (a) include a smoothing
kernel that smoothly goes from anisotropic to isotropic, and (b) a variant that
does not correct for redshift space distortions. We compare the performance of
this algorithm with the standard reconstruction method. Our examinations of the
methods include cross-correlation of the reconstructed density field with the
linear density field, reconstructed two-point functions, and BAO parameter
fitting. We also examine the impact of various parameters, such as smoothing
scale, anisotropic smoothing, tracer type/bias, and the inclusion of second
order perturbation theory. We find that the two reconstruction algorithms are
comparable in most of the areas we examine. In particular, both algorithms give
consistent fittings of BAO parameters. The fits are robust over a range of
smoothing scales. We find the iterative algorithm is significantly better at
removing redshift space distortions. The new algorithm will be a promising
method to be employed in the ongoing and future large-scale structure surveys. |
A free parametrized TOV: Modified Gravity from Newtonian to Relativistic
Stars: We test a free {\it ad hoc} parametrization of the Tolman-Oppenheimer-Volkoff
(TOV) equation. We do not have in mind any specific extended theory of gravity
(ETG) but each new parameter introduced has a physical interpretation. Our aim
is fully pedagogical rather than a proposal for a new ETG. Given a realistic
neutron star equation of state we map the contributions of each new parameter
into a shift in trajectories of the mass-radius diagram. This exercise allows
us to make the correspondence between each TOV sector with possible
modifications of gravity and clarifies how neutron star observations are
helpful for distinguishing theories. | The luminosity distance-redshift relation up to second order in the
Poisson gauge with anisotropic stress: We present the generalization of previously published results, about the
perturbed redshift and the luminosity-redshift relation up to second order in
perturbation theory, for the case of the Poisson gauge and in the presence of
anisotropic stress. The results are therefore valid for general dark energy
models and (most) modified gravity models. We use an innovative approach based
on the recently proposed "geodesic light-cone" gauge. We then compare our
finding with other results, which recently appeared in the literature, for the
particular case of vanishing anisotropic stress. Arriving at a common accepted
expression for the non-linear and relativistic corrections to the redshift and
distance-redshift relation is of fundamental importance in view of future
cosmological surveys. Thanks to these surveys the Universe will be further
probed with high precision and at very different scales, where non-linear and
relativistic effects can play a key role. |
The Resolved Radio--FIR Correlation in Nearby Galaxies with Herschel and
Spitzer: We investigate the correlation between the far-infrared (FIR) and radio
continuum emission from NGC6946 on spatial scales between 0.9 and 17 kpc. We
use the Herschel PACS (70, 100, 160$\mu$m) and SPIRE (250$\mu$m) data from the
KINGFISH project. Separating the free-free and synchrotron components of the
radio continuum emission, we find that FIR is better correlated with the
free-free than the synchrotron emission. Compared to a similar study in M33 and
M31, we find that the scale dependence of the synchrotron--FIR correlation in
NGC6946 is more similar to M31 than M33. The scale dependence of the
synchrotron--FIR correlation can be explained by the turbulent-to-ordered
magnetic field ratio or, equivalently, the diffusion length of the cosmic ray
electrons in these galaxies. | Cosmological models with Lagrange Multiplier Field: We first consider the Einstein-aether theory with a gravitational coupling
and a Lagrange multiplier field, and then consider the non-minimally coupled
quintessence field theory with Lagrange multiplier field. We study the
influence of the Lagrange multiplier field on these models. We show that the
energy density evolution of the Einstein-aether field and the quintessence
field are significantly modified. The energy density of the Einstein-aether is
nearly a constant during the entire history of the Universe. The energy density
of the quintessence field can also be kept nearly constant in the matter
dominated Universe, or even exhibit a phantom-like behavior for some models.
This suggests a possible dynamical origin of the cosmological constant or dark
energy. Further more, for the canonical quintessence in the absence of
gravitational coupling, we find that the quintessence scalar field can play the
role of cold dark matter with the introduction of a Lagrange multiplier field.
We conclude that the Lagrange multiplier field could play a very interesting
and important role in the construction of cosmological models. |
Probing primordial features with the primary CMB: CMB photons travel from the last scattering surface, when the primary CMB has
been generated, along the surface of the light cone to us. During their travel,
they are affected by many secondary effects such as the integrated Sachs-Wolfe
effect and CMB lensing. These CMB secondary effects modify the CMB primary
power spectrum adding degeneracies and decreasing the sensibility to primordial
parameters. The possibility to reconstruct the primary CMB anisotropies will
allow us to have a more direct observable to test the physics of the early
universe. We propose to study the imprint of features in the primordial power
spectrum with the primary CMB after the subtraction of the reconstructed ISW
signal from the observed CMB temperature angular power spectrum. We consider
the application to features models able to fit two of the large scales
anomalies observed in the CMB temperature angular power spectrum: the deficit
of power at $\ell \sim 2$ and at $\ell \sim 22$. This method allows to improve
significantly the constraints on the features parameters up to $16\%$ for
models predicting a suppression of power of the quadrupole and up to $27\%$ for
models with features at $\ell \sim 22$, assuming instrumental sensitivity
similar to the $Planck$ satellite (depending on the goodness of the ISW
reconstruction). Furthermore, it gives the opportunity to understand if these
anomalies are attributed to early- or late-time physics. | A measurement of cluster masses using Planck and SPT-SZ CMB lensing: We used an unbiased CMB lensing mass estimator on 468 SPT-SZ clusters from
the SPT-SZ and the Planck public data, the first such estimation using combined
ground- and space-based data. We measured the average ratio between CMB lensing
and SZ mass to be $M_{\rm CMBlens}/M_{\rm SZ} = 0.98 \pm 0.19$ (stat.) $\pm
0.03$ (syst.). The average CMB lensing mass from the combination of the two
data sets is measured at 4.8$\sigma$, which is a significant gain with respect
to the measurement performed on the SPT-SZ only (3.9$\sigma$) or the Planck
only (3.7$\sigma$) data set. We showed that the combination not only takes
advantage of the two different ranges of spatial scales (i.e. Fourier modes)
observed but also exploits the lensing induced correlation between scales
observed by one experiment and the other. This result demonstrates the
importance of measuring a large range of spatial scales for CMB lensing mass
estimation, from arcmin to degrees. This large range of scales will most
probably be provided by the combination of various data sets, such as from the
large and small aperture telescopes of the upcoming Simons Observatory and
future CMB-S4 experiment, and Planck. In this context, the Planck data will
remain a key element for CMB lensing cluster studies in the years to come. |
Constraining the cross-section of dark matter with giant radial arcs in
galaxy clusters: We compare the statistics and morphology of giant arcs in galaxy clusters
using N-body and non-radiative SPH simulations within the standard cold dark
matter model and simulations where dark matter has a non-negligible probability
of interaction (parametrized by its cross-section), i.e self-interacting dark
matter (SIDM). We use a ray-tracing technique to produce a statistically large
number of arcs around six simulated galaxy clusters at different redshifts.
Since dark matter is more likely to interact in colliding clusters than in
relaxed clusters, and this probability of interaction is largest in denser
regions, we focus our analysis on radial arcs (which trace the lensing
potential in the central region better than tangential arcs) in galaxy clusters
which underwent (or are undergoing) a major merger. We find that
self-interacting dark matter produces fewer radial arcs than standard cold dark
matter but they are on average more magnified. We also appreciate differences
in the arc morphology that could be used to statistically favor one model
versus the other. | RASS-MCMF: A full-sky X-ray selected galaxy cluster catalog: We present the RASS-MCMF catalog of 8,465 X-ray selected galaxy clusters over
25,000 deg$^2$ of extragalactic sky. The accumulation of deep, multiband
optical imaging data, the development of the Multi-Component Matched Filter
cluster confirmation algorithm (MCMF), and the release of the DESI Legacy
Survey DR10 catalog makes it possible -- for the first time, more than 30 years
after the launch of the ROSAT X-ray satellite -- to identify the majority of
the galaxy clusters detected in the second ROSAT All-Sky-Survey (RASS) source
catalog (2RXS). The resulting 90\% pure RASS-MCMF catalog is the largest
ICM-selected cluster sample to date. RASS-MCMF probes a large dynamic range in
cluster mass spanning from galaxy groups to the most massive clusters. The
cluster redshift distribution peaks at $z\sim0.1$ and extends to redshifts
$z\sim1$. Out to $z\sim0.4$, the RASS-MCMF sample contains more clusters per
redshift interval ($dN/dz$) than any other ICM-selected sample. In addition to
the main sample, we present two subsamples with 6,924 and 5,516 clusters,
exhibiting 95\% and 99\% purity, respectively.. We forecast the utility of the
sample for a cluster cosmological study, using realistic mock catalogs that
incorporate most observational effects, including the X-ray exposure time and
background variations, the existence likelihood selection and the impact of the
optical cleaning with the algorithm MCMF. Using realistic priors on the
observable-mass relation parameters from a DES-based weak lensing analysis, we
estimate the constraining power of the RASS-MCMF$\times$DES sample to be of
0.026, 0.033 and 0.15 ($1\sigma$) on the parameters $\Omega_\mathrm{m}$,
$\sigma_8$ and $w$, respectively. |
Intrinsic alignment of redMaPPer clusters: cluster shape - matter
density correlation: We measure the alignment of the shapes of galaxy clusters, as traced by their
satellite distributions, with the matter density field using the public
redMaPPer catalogue based on SDSS-DR8, which contains 26 111 clusters up to
z~0.6. The clusters are split into nine redshift and richness samples; in each
of them we detect a positive alignment, showing that clusters point towards
density peaks. We interpret the measurements within the tidal alignment
paradigm, allowing for a richness and redshift dependence. The intrinsic
alignment (IA) amplitude at the pivot redshift z=0.3 and pivot richness
\lambda=30 is A_{IA}^{gen}=12.6_{-1.2}^{+1.5}. We obtain tentative evidence
that the signal increases towards higher richness and lower redshift. Our
measurements agree well with results of maxBCG clusters and with
dark-matter-only simulations. Comparing our results to IA measurements of
luminous red galaxies, we find that the IA amplitude of galaxy clusters forms a
smooth extension towards higher mass. This suggests that these systems share a
common alignment mechanism, which can be exploited to improve our physical
understanding of IA. | ART^2 : Coupling Lyman-alpha Line and Multi-wavelength Continuum
Radiative Transfer: Narrow-band Lya line and broad-band continuum have played important roles in
the discovery of high-redshift galaxies in recent years. Hence, it is crucial
to study the radiative transfer of both Lya and continuum photons in the
context of galaxy formation and evolution in order to understand the nature of
distant galaxies. Here, we present a three-dimensional Monte Carlo radiative
transfer code, All-wavelength Radiative Transfer with Adaptive Refinement Tree
(ART^2), which couples Lya line and multi-wavelength continuum, for the study
of panchromatic properties of galaxies and interstellar medium. This code is
based on the original version of Li et al., and features three essential
modules: continuum emission from X-ray to radio, Lya emission from both
recombination and collisional excitation, and ionization of neutral hydrogen.
The coupling of these three modules, together with an adaptive refinement grid,
enables a self-consistent and accurate calculation of the Lya properties. As an
example, we apply ART^2 to a cosmological simulation that includes both star
formation and black hole growth, and study in detail a sample of massive
galaxies at redshifts z=3.1 - 10.2. We find that these galaxies are Lya
emitters (LAEs), whose Lya emission traces the dense gas region, and that their
Lya lines show a shape characteristic of gas inflow. Furthermore, the Lya
properties, including photon escape fraction, emergent luminosity, and
equivalent width, change with time and environment. Our results suggest that
LAEs evolve with redshift, and that early LAEs such as the most distant one
detected at z ~ 8.6 may be dwarf galaxies with a high star formation rate
fueled by infall of cold gas, and a low Lya escape fraction. |
2D Genus Topology of 21-cm Differential Brightness Temperature During
Cosmic Reionization: A novel method to characterize the topology of the early-universe
intergalactic medium during the epoch of cosmic reionization is presented. The
21-cm radiation background from high redshift is analyzed through the
calculation of the 2-dimensional (2D) genus. The radiative transfer of
hydrogen-ionizing photons and ionization-rate equations are calculated in a
suite of numerical simulations under various input parameters. The 2D genus is
calculated from the mock 21-cm images of the high-redshift Universe. We
construct the 2D genus curve by varying the threshold differential brightness
temperature, and compare this to the 2D genus curve of the underlying density
field. We find that (1) the 2D genus curve reflects the evolutionary track of
cosmic reionization and (2) the 2D genus curve can discriminate between certain
reionization scenarios and thus indirectly probe the properties of
radiation-sources. Choosing the right beam shape of a radio antenna is crucial
for this analysis. To this end, the Square Kilometre Array (SKA) is found to be
a suitable apparatus for this analysis in terms of sensitivity, even though
some deterioration of the data for this purpose is unavoidable under the
planned size of the antenna core. | Planck intermediate results. XVI. Profile likelihoods for cosmological
parameters: We explore the 2013 Planck likelihood function with a high-precision
multi-dimensional minimizer (Minuit). This allows a refinement of the
Lambda-cdm best-fit solution with respect to previously-released results, and
the construction of frequentist confidence intervals using profile likelihoods.
The agreement with the cosmological results from the Bayesian framework is
excellent, demonstrating the robustness of the Planck results to the
statistical methodology. We investigate the inclusion of neutrino masses, where
more significant differences may appear due to the non-Gaussian nature of the
posterior mass distribution. By applying the Feldman--Cousins prescription, we
again obtain results very similar to those of the Bayesian methodology.
However, the profile-likelihood analysis of the CMB combination
(Planck+WP+highL) reveals a minimum well within the unphysical negative-mass
region. We show that inclusion of the Planck CMB-lensing information
regularizes this issue, and provide a robust frequentist upper limit $M_\nu <
0.26 eV$ ($95%$ confidence) from the CMB+lensing+BAO data combination. |
Dark matter-baryon scattering effects on temperature perturbations and
implications for cosmic dawn: The nature of dark matter remains unknown, but upcoming measurements probing
the high-redshift Universe may provide invaluable insight. In the presence of
dark matter-baryon scattering, the suppression in the matter power spectrum and
the colder mean gas temperature are expected to modify the evolution of cosmic
dawn and reionization. However, the contributions from such interactions to the
baryon and dark matter temperature perturbations have been neglected thus far.
In this work, we derive these contributions, evolve the cosmological
perturbations until the end of the dark ages and show that they may have a
significant impact in the beginning of cosmic dawn. In particular, we find that
the amplitude of the temperature power spectrum at large scales can change by
up to 1--2 orders of magnitude and that the matter power spectrum is further
suppressed with respect to $\Lambda$CDM by $5$-$10\%$ at $k\sim 200\, {\rm
Mpc^{-1}}$ compared to the computation ignoring these contributions for
scattering cross sections at current CMB limits. As a case example, we also
compute the HI power spectrum from the dark ages, finding significant
differences due to the changes in the temperature and ionization fraction power
spectra. We argue that these new contributions must be included in studies of
this dark matter model relying on cosmic dawn and reionization observables. | SHARDS: Survey for High-z Absorption Red & Dead Sources: SHARDS, an ESO/GTC Large Program, is an ultra-deep (26.5 mag)
spectro-photometric survey with GTC/OSIRIS designed to select and study massive
passively evolving galaxies at z=1.0-2.3 in the GOODS-N field using a set of 24
medium-band filters (FWHM~17 nm) covering the 500-950 nm spectral range. Our
observing strategy has been planned to detect, for z>1 sources, the prominent
Mg absorption feature (at rest-frame ~280 nm), a distinctive, necessary, and
sufficient feature of evolved stellar populations (older than 0.5 Gyr). These
observations are being used to: (1) derive for the first time an unbiased
sample of high-z quiescent galaxies, which extends to fainter magnitudes the
samples selected with color techniques and spectroscopic surveys; (2) derive
accurate ages and stellar masses based on robust measurements of spectral
features such as the Mg(UV) or D(4000) indices; (3) measure their redshift with
an accuracy Delta(z)/(1+z)<0.02; and (4) study emission-line galaxies
(starbursts and AGN) up to very high redshifts. The well-sampled optical SEDs
provided by SHARDS for all sources in the GOODS-N field are a valuable
complement for current and future surveys carried out with other telescopes
(e.g., Spitzer, HST, and Herschel). |
POPSTAR Evolutionary Synthesis Models III: Photometric properties of
young star clusters and mixed populations: This is the third paper of a series reporting the results from the POPSTAR
evolutionary synthesis models. The main goal of this work is to present and
discuss the synthetic photometric properties of Single Stellar Populations
(SSPs) resulting from our POPSTAR code. Colours in the Johnson and SDSS
systems, halpha and hbeta luminosities and equivalent widths, and ionising
region size, have been computed for a wide range of metallicity (Z = 0.0001 -
0.05) and age (0.1 Myr to 20 Gyr). We demonstrate the importance of the
contribution of emission lines to broader-band photometry when characterising
stellar populations, through the presentation of both contaminated and
non-contaminated colours (in both the Johnson and SDSS systems). The tabulated
colours include stellar and nebular components, in addition to line emission.
The main application of these models is the determination of physical
properties of a given young ionising cluster, when only photometric
observations are available; for an isolated star forming region, the young star
cluster models can be used, free from the contamination of any underlying
background stellar population. In most cases, however, the ionising population
is usually embedded in a large and complex system, and the observed photometric
properties result from the combination of a young star-forming burst and the
underlying older population of the host. Therefore, the second objective of
this paper is to provide a grid of models useful in the interpretation of mixed
regions where the separation of young and old populations is not sufficiently
reliable. We describe the set of PopStar Spectral Energy Distributions, the
derived colours and other photometric parameters, for mixed populations where
an underlying host population is combined in different mass ratios with a
recent ionising burst. | The intergalactic medium in the cosmic web: The intergalactic medium (IGM) accounts for ~90% of baryons at all epochs and
yet its three dimensional distribution in the cosmic web remains mostly
unknown. This is so because the only feasible way to observe the bulk of the
IGM is through intervening absorption line systems in the spectra of bright
background sources, which limits its characterization to being one-dimensional.
Still, an averaged three dimensional picture can be obtained by combining and
cross-matching multiple one-dimensional IGM information with three-dimensional
galaxy surveys. Here, we present our recent and current efforts to map and
characterize the IGM in the cosmic web using galaxies as tracers of the
underlying mass distribution. In particular, we summarize our results on: (i)
IGM around star-forming and non-star-forming galaxies; (ii) IGM within and
around galaxy voids; and (iii) IGM in intercluster filaments. With these
datasets, we can directly test the modern paradigm of structure formation and
evolution of baryonic matter in the Universe. |
Forecasts for Next Generation tSZ Surveys: the Impact of a
Cosmology-Dependent Selection Function: The thermal Sunyaev-Zel'dovich (tSZ) effect is one of the primary tools for
finding and characterizing galaxy clusters. Several ground-based experiments
are either underway or are being planned for mapping wide areas of the sky at
$\sim 150$ GHz with large-aperture telescopes. We present cosmological
forecasts for a 'straw man' tSZ survey that will observe a sky area between
$200$ and $10^4$ deg$^2$ to an rms noise level between 2.8 and 20.2
$\mu$K-arcmin. The probes we consider are the cluster number counts (as a
function of the integrated Compton-$Y$ parameter and redshift) and their
angular clustering (as a function of redshift). At fixed observing time, we
find that wider surveys constrain cosmology slightly better than deeper ones
due to their increased ability to detect rare high-mass clusters. In all cases,
we notice that adding the clustering information does not practically improve
the constraints derived from the number counts. We compare forecasts obtained
by sampling the posterior distribution with the Markov-chain-Monte-Carlo method
against those derived using the Fisher-matrix formalism. We find that the
latter produces slightly optimistic constraints where errors are underestimated
at the 10 per cent level. Most importantly, we use an analytic method to
estimate the selection function of the survey and account for its response to
variations of the cosmological parameters in the likelihood function. Our
analysis demonstrates that neglecting this effect (as routinely done in the
literature) yields artificially tighter constraints by a factor of 2.2 and 1.7
for $\sigma_8$ and $\Omega_\mathrm{M}$, respectively. | Improving the modelling of redshift-space distortions: I. A bivariate
Gaussian description for the galaxy pairwise velocity distributions: As a step towards a more accurate modelling of redshift-space distortions in
galaxy surveys, we develop a general description of the probability
distribution function of galaxy pairwise velocities within the framework of the
so-called streaming model. For a given galaxy separation $\vec{r}$, such
function can be described as a superposition of virtually infinite local
distributions. We characterize these in terms of their moments and then
consider the specific case in which they are Gaussian functions, each with its
own mean $\mu$ and dispersion $\sigma$. Based on physical considerations, we
make the further crucial assumption that these two parameters are in turn
distributed according to a bivariate Gaussian, with its own mean and covariance
matrix. Tests using numerical simulations explicitly show that with this
compact description one can correctly model redshift-space distorsions on all
scales, fully capturing the overall linear and nonlinear dynamics of the galaxy
flow at different separations. In particular, we naturally obtain
Gaussian/exponential, skewed/unskewed distribution functions, depending on
separation as observed in simulations and data. Also, the recently proposed
single-Gaussian description of redshift-space distortions is included in this
model as a limiting case, when the bivariate Gaussian is collapsed to a
two-dimensional Dirac delta function. We also show how this description
naturally allows for the Taylor expansion of $1+\xi_S(\vec{s})$ around
$1+\xi_R(r)$, which leads to the Kaiser linear formula when truncated to second
order, expliciting its connection with the moments of the velocity distribution
functions. More work is needed, but these results indicate a very promising
path to make definitive progress in our program to improve RSD estimators. |
Euclid preparation: XII. Optimizing the photometric sample of the Euclid
survey for galaxy clustering and galaxy-galaxy lensing analyses: The accuracy of photometric redshifts (photo-zs) particularly affects the
results of the analyses of galaxy clustering with photometrically-selected
galaxies (GCph) and weak lensing. In the next decade, space missions like
Euclid will collect photometric measurements for millions of galaxies. These
data should be complemented with upcoming ground-based observations to derive
precise and accurate photo-zs. In this paper, we explore how the tomographic
redshift binning and depth of ground-based observations will affect the
cosmological constraints expected from Euclid. We focus on GCph and extend the
study to include galaxy-galaxy lensing (GGL). We add a layer of complexity to
the analysis by simulating several realistic photo-z distributions based on the
Euclid Consortium Flagship simulation and using a machine learning photo-z
algorithm. We use the Fisher matrix formalism and these galaxy samples to study
the cosmological constraining power as a function of redshift binning, survey
depth, and photo-z accuracy. We find that bins with equal width in redshift
provide a higher Figure of Merit (FoM) than equipopulated bins and that
increasing the number of redshift bins from 10 to 13 improves the FoM by 35%
and 15% for GCph and its combination with GGL, respectively. For GCph, an
increase of the survey depth provides a higher FoM. But the addition of faint
galaxies beyond the limit of the spectroscopic training data decreases the FoM
due to the spurious photo-zs. When combining both probes, the number density of
the sample, which is set by the survey depth, is the main factor driving the
variations in the FoM. We conclude that there is more information that can be
extracted beyond the nominal 10 tomographic redshift bins of Euclid and that we
should be cautious when adding faint galaxies into our sample, since they can
degrade the cosmological constraints. | A GMBCG Galaxy Cluster Catalog of 55,424 Rich Clusters from SDSS DR7: We present a large catalog of optically selected galaxy clusters from the
application of a new Gaussian Mixture Brightest Cluster Galaxy (GMBCG)
algorithm to SDSS Data Release 7 data. The algorithm detects clusters by
identifying the red sequence plus Brightest Cluster Galaxy (BCG) feature, which
is unique for galaxy clusters and does not exist among field galaxies. Red
sequence clustering in color space is detected using an Error Corrected
Gaussian Mixture Model. We run GMBCG on 8240 square degrees of photometric data
from SDSS DR7 to assemble the largest ever optical galaxy cluster catalog,
consisting of over 55,000 rich clusters across the redshift range from 0.1 < z
< 0.55. We present Monte Carlo tests of completeness and purity and perform
cross-matching with X-ray clusters and with the maxBCG sample at low redshift.
These tests indicate high completeness and purity across the full redshift
range for clusters with 15 or more members. |
Quantifying dimensionality: Bayesian cosmological model complexities: We demonstrate a measure for the effective number of parameters constrained
by a posterior distribution in the context of cosmology. In the same way that
the mean of the Shannon information (i.e. the Kullback-Leibler divergence)
provides a measure of the strength of constraint between prior and posterior,
we show that the variance of the Shannon information gives a measure of
dimensionality of constraint. We examine this quantity in a cosmological
context, applying it to likelihoods derived from Cosmic Microwave Background,
large scale structure and supernovae data. We show that this measure of
Bayesian model dimensionality compares favourably both analytically and
numerically in a cosmological context with the existing measure of model
complexity used in the literature. | Constraints on OH Megamaser Excitation from a Survey of OH Satellite
Lines: We report the results of a full-Stokes survey of all four 18 cm OH lines in
77 OH megamasers (OHMs) using the Arecibo Observatory. This is the first survey
of OHMs that included observations of the OH satellite lines; only 4 of the 77
OHMs have existing satellite line observations in the literature. In 5 sources,
satellite line emission is detected, with 3 of the 5 sources re-detections of
previously published sources. The 2 sources with new detections of satellite
line emission are IRAS F10173+0829, which was detected at 1720 MHz, and IRAS
F15107+0724, for which both the 1612 MHz and 1720 MHz lines were detected. In
IRAS F15107+0724, the satellite lines are partially conjugate, as 1720 MHz
absorption and 1612 MHz emission have the same structure at some velocities
within the source, along with additional broader 1612 MHz emission. This is the
first observed example of conjugate satellite lines in an OHM. In the remaining
sources, no satellite line emission is observed. The detections and upper
limits are generally consistent with models of OHM emission in which all of the
18 cm OH lines have the same excitation temperature. There is no evidence for a
significant population of strong satellite line emitters among OHMs. |
The Cosmic Microwave Background: a strange characteristic: The ratio of the self-gravitational energy density of the scattering
particles in the universe to the energy density of the scattered photons in the
cosmic microwave background (CMB) is the same in any volume of space. These two
energy densities are equal at a radiation temperature on the order of the
present CMB temperature. | The TeV-mass curvaton: We consider the constraints for a curvaton with mass m ~ 1 TeV and show that
they are not consistent with a purely quadratic potential. Even if the curvaton
self-interactions were very weak, they must be accounted for as they affect the
dynamical evolution of the curvature perturbation. We show that the only
TeV-mass curvaton interaction potential that yields the correct perturbation
amplitude, decays before the dark matter freeze-out, and does not give rise to
non-Gaussian perturbations that are in conflict with the present limits, is
given by V_int= sigma^8/M^4. The decay width of the curvaton should be in the
range Gamma= 10^-15...10^-17 GeV. The model typically predicts large
non-linearity parameters f_NL and g_NL that should be observable by the Planck
satellite. We also discuss various physical possibilities to obtain the
required small curvaton decay rate. |
A distortion of very--high--redshift galaxy number counts by
gravitational lensing: The observed number counts of high-redshift galaxy candidates have been used
to build up a statistical description of star-forming activity at redshift z >~
7, when galaxies reionized the Universe. Standard models predict that a high
incidence of gravitational lensing will probably distort measurements of flux
and number of these earliest galaxies. The raw probability of this happening
has been estimated to be ~ 0.5 percent, but can be larger owing to
observational biases. Here we report that gravitational lensing is likely to
dominate the observed properties of galaxies with redshifts of z >~ 12, when
the instrumental limiting magnitude is expected to be brighter than the
characteristic magnitude of the galaxy sample. The number counts could be
modified by an order of magnitude, with most galaxies being part of multiply
imaged systems, located less than 1 arcsec from brighter foreground galaxies at
z ~ 2. This lens-induced association of high-redshift and foreground galaxies
has perhaps already been observed among a sample of galaxy candidates
identified at z ~ 10.6. Future surveys will need to be designed to account for
a significant gravitational lensing bias in high-redshift galaxy samples. | The Double Galaxy Cluster Abell 2465 III. X-ray and Weak-lensing
Observations: We report Chandra X-ray observations and optical weak-lensing measurements
from Subaru/Suprime-Cam images of the double galaxy cluster Abell 2465
(z=0.245). The X-ray brightness data are fit to a beta-model to obtain the
radial gas density profiles of the northeast (NE) and southwest (SW)
sub-components, which are seen to differ in structure. We determine core radii,
central temperatures, the gas masses within $r_{500c}$, and the total masses
for the broader NE and sharper SW components assuming hydrostatic equilibrium.
The central entropy of the NE clump is about two times higher than the SW.
Along with its structural properties, this suggests that it has undergone
merging on its own. The weak-lensing analysis gives virial masses for each
substructure, which compare well with earlier dynamical results. The derived
outer mass contours of the SW sub-component from weak lensing are more
irregular and extended than those of the NE. Although there is a weak
enhancement and small offsets between X-ray gas and mass centers from weak
lensing, the lack of large amounts of gas between the two sub-clusters
indicates that Abell 2465 is in a pre-merger state. A dynamical model that is
consistent with the observed cluster data, based on the FLASH program and the
radial infall model, is constructed, where the subclusters currently separated
by ~1.2Mpc are approaching each other at ~2000km/s and will meet in ~0.4Gyr. |
Dwarf spheroidals in the M81 Group - Metallicity distribution functions
and population gradients: We study the dwarf spheroidal galaxies in the nearby M81 group in order to
construct their photometric metallicity distributions and to investigate the
potential presence of population gradients. We select all the dwarf spheroidals
with available Hubble Space Telescope / Advanced Camera for Surveys archival
observations, nine in total. We interpolate isochrones so as to assign a
photometric metallicity to each star within a selection box in the
color-magnitude diagram of each dwarf galaxy. We assume that the dwarf
spheroidals contain mainly an old stellar population. In order to search for
metallicity gradients, we examine the spatial distribution of two stellar
populations that we separate according to their metallicities. As a result, we
present the photometric metallicity distribution functions, the cumulative
histograms and smoothed density maps of the metal-poor and metal-rich stars as
well as of the intermediate-age stars. From our photometric data we find that
all the dwarf spheroidals show a wide range in metallicities, with mean values
that are typical for old and metal-poor systems, with the exception of one
dwarf spheroidal, namely IKN. Some of our dwarf spheroidals exhibit
characteristics of transition-type dwarfs. Compared to the Local Group
transition type dwarfs, the M81 group ones appear to have mean metallicity
values slightly more metal-rich at a given luminosity. All the dwarf
spheroidals considered here appear to exhibit either population gradients or
spatial variations in the centroids of their metal-poor and metal-rich
population. In addition, there are luminous AGB stars detected in all of them
with spatial distributions suggesting that they are well mixed with the old
stars. | Debiasing with Diffusion: Probabilistic reconstruction of Dark Matter
fields from galaxies with CAMELS: Galaxies are biased tracers of the underlying cosmic web, which is dominated
by dark matter components that cannot be directly observed. Galaxy formation
simulations can be used to study the relationship between dark matter density
fields and galaxy distributions. However, this relationship can be sensitive to
assumptions in cosmology and astrophysical processes embedded in the galaxy
formation models, that remain uncertain in many aspects. In this work, we
develop a diffusion generative model to reconstruct dark matter fields from
galaxies. The diffusion model is trained on the CAMELS simulation suite that
contains thousands of state-of-the-art galaxy formation simulations with
varying cosmological parameters and sub-grid astrophysics. We demonstrate that
the diffusion model can predict the unbiased posterior distribution of the
underlying dark matter fields from the given stellar mass fields, while being
able to marginalize over uncertainties in cosmological and astrophysical
models. Interestingly, the model generalizes to simulation volumes
approximately 500 times larger than those it was trained on, and across
different galaxy formation models. Code for reproducing these results can be
found at https://github.com/victoriaono/variational-diffusion-cdm |
The galaxy group NGC2563: We present a $Chandra$ study of the hot intragroup medium (hIGM) of the
galaxy group NCG2563. The $Chandra$ mosaic observations, with a total exposure
time of ~430 ks, allow the gas density to be detected beyond $R_{200}$ and the
gas temperature out to 0.75 $R_{200}$. This represents the first observational
measurement of the physical properties of a poor groups beyond $R_{500}$. By
capitalizing on the exquisite spatial resolution of $Chandra$ that is capable
to remove unrelated emission from point sources and substructures, we are able
to radially constrain the inhomogeneities of gas ("clumpiness"), gas fraction,
temperature and entropy distribution. Although there is some uncertainty in the
measurements, we find evidences of gas clumping in the virialization region,
with clumping factor of about 2 - 3 at $R_{200}$. The gas clumping-corrected
gas fraction is significantly lower than the cosmological baryon budget. These
results may indicate a larger impact of the gas inhomogeneities with respect to
the prediction from hydrodynamic numerical simulations, and we discuss possible
explanations for our findings. | Evaluating backreaction with the ellipsoidal collapse model: We evaluate the effect of structure formation on the average expansion rate
with a statistical treatment where density peaks and troughs are modelled as
homogeneous ellipsoids. This extends earlier work that used spherical regions.
We find that the shear and the presence of filamentary and planar structures
have only a small impact on the results. The expansion rate times the age of
the universe $Ht$ increases from 2/3 to 0.83 at late times, in order of
magnitude agreement with observations, although the change is slower and takes
longer than in the real universe. We discuss shortcomings that have to be
addressed for this and similar statistical models in the literature to develop
into realistic quantitative treatment of backreaction. |
Compact Binary Merger Rate in Dark-Matter Spikes: Nowadays, the existence of supermassive black holes (SMBHs) in the center of
galactic halos is almost confirmed. An extremely dense region referred to as
dark-matter spike is expected to form around central SMBHs as they grow and
evolve adiabatically. In this work, we calculate the merger rate of compact
binaries in dark-matter spikes while considering halo models with spherical and
ellipsoidal collapses. Our findings exhibit that ellipsoidal-collapse dark
matter halo models can potentially yield the enhancement of the merger rate of
compact binaries. Finally, our results confirm that the merger rate of
primordial black hole binaries is consistent with the results estimated by the
LIGO-Virgo detectors, while such results can not be realized for primordial
black hole-neutron star binaries. | Cosmology at at Crossroads: Tension with the Hubble Constant: We are at an interesting juncture in cosmology. With new methods and
technology, the accuracy in measurement of the Hubble constant has vastly
improved, but a recent tension has arisen that is either signaling new physics
or as-yet unrecognized uncertainties. |
Angular Power Spectra of the Millimeter Wavelength Background Light from
Dusty Star-forming Galaxies with the South Pole Telescope: We use data from the first 100 square-degree field observed by the South Pole
Telescope (SPT) in 2008 to measure the angular power spectrum of temperature
anisotropies contributed by the background of dusty star-forming galaxies
(DSFGs) at millimeter wavelengths. From the auto and cross-correlation of 150
and 220 GHz SPT maps, we significantly detect both Poisson distributed and, for
the first time at millimeter wavelengths, clustered components of power from a
background of DSFGs. The spectral indices between 150 and 220 GHz of the
Poisson and clustered components are found to be 3.86 +- 0.23 and 3.8 +- 1.3
respectively, implying a steep scaling of the dust emissivity index beta ~ 2.
The Poisson and clustered power detected in SPT, BLAST (at 600, 860, and 1200
GHz), and Spitzer (1900 GHz) data can be understood in the context of a simple
model in which all galaxies have the same graybody spectrum with dust
emissivity index of beta = 2 and dust temperature T_d = 34 K. In this model,
half of the 150 GHz background light comes from redshifts greater than 3.2. We
also use the SPT data to place an upper limit on the amplitude of the kinetic
Sunyaev-Zel'dovich power spectrum at l = 3000 of 13 uK^2 at 95% confidence. | Is the CMB asymmetry due to the kinematic dipole?: Parity violation found in the Cosmic Microwave Background (CMB) radiation is
a crucial clue for the non-standard cosmological model or the possible
contamination of various foreground residuals and/or calibration of the CMB
data sets. In this paper, we study the directional properties of the CMB parity
asymmetry by excluding the $m=0$ modes in the definition of parity parameters.
We find that the preferred directions of the parity parameters coincide with
the CMB kinematic dipole, which implies that the CMB parity asymmetry may be
connected with the possible contamination of the residual dipole component. We
also find that such tendency is not only localized at $l=2,3$, but in the
extended multipole ranges up to $l\sim 22$. |
Cosmic backgrounds of relic gravitons and their absolute normalization: Provided the consistency relations are not violated, the recent Bicep2
observations pin down the absolute normalization, the spectral slope and the
maximal frequency of the cosmic graviton background produced during inflation.
The properly normalized spectra are hereby computed from the lowest frequencies
(of the order of the present Hubble rate) up to the highest frequency range in
the GHz region. Deviations from the conventional paradigm cannot be excluded
and are examined by allowing for different physical possibilities including, in
particular, a running of the tensor spectral index, an explicit breaking of the
consistency relations and a spike in the high-frequency tail of the spectrum
coming either from a post-inflationary phase dominated by a stiff fluid of from
the contribution of waterfall fields in a hybrid inflationary context. The
direct determinations of the tensor to scalar ratio at low frequencies, if
confirmed by the forthcoming observations, will also affect and constrain the
high-frequencies uncertainties. The limits on the cosmic graviton backgrounds
coming from wide-band interferometers (such as Ligo/Virgo, Lisa and Bbo/Decigo)
together with a more accurate scrutiny of the tensor B mode polarization at low
frequencies will set direct bounds on the post-inflationary evolution and on
other unconventional completions of the standard lore. | Multiband Photopolarimetric Monitoring of the Outburst of the Blazar
3C~454.3 in 2007: We report on optical-near-infrared photopolarimetric observations of a blazar
3C 454.3 over 200 d. The object experienced an optical outburst in July 2007.
This outburst was followed by a short state fainter than $V=15.2$ mag lasting
$\sim 25$ d. The object, then, entered an active state during which we observed
short flares having a timescale of 3-10 d. The object showed two types of
features in the color-magnitude relationship. One is a "bluer-when-brighter"
trend in the outburst state, and the other is a "redder-when-brighter" trend in
the faint state. These two types of features suggest a contribution of a
thermal emission to the observed flux, as suspected in previous studies. Our
polarimetric observation detected two episodes of the rotation of the
polarization vector. The first one was a counterclockwise rotation in the $QU$
plane during the outburst state. After this rotation event of the polarization
vector, the object entered a rapidly fading stage. The second one was seen in a
series of flares during the active state. Each flare had a specific position
angle of polarization, and it apparently rotated clockwise from the first to
the last flares. Thus, the object exhibited rotations of the polarization
vector in opposite directions. We estimated a decay timescale of the short
flares during the active state, and then calculated an upper limit of the
strength of the magnetic field, $B$=0.2 G, assuming a typical beaming factor of
blazars, $\delta=20$. This upper limit of $B$ is smaller than those previously
estimated from spectral analysis. |
An Analytic Treatment of Underdamped Axionic Blue Isocurvature
Perturbations: Previous computations of strongly blue tilted axionic isocurvature spectra
were computed in the parametric region in which the lightest time-dependent
mass is smaller than the Hubble expansion rate during inflation, leading to an
overdamped time evolution. Here we present the strongly blue tilted axionic
isocurvature spectrum in an underdamped time evolution parametric regime.
Somewhat surprisingly, there exist parametric regions with a strong resonant
spectral behavior that leads to a rich isocurvature spectral shape. We focus on
computing this resonant spectrum analytically in a large parametric region
amenable to such computations. Because the spectrum is sensitive to
nonperturbative classical field dynamics, a wide variety of analytic techniques
are used including a time-space effective potential obtained by integrating out
high frequency fluctuations. | Dark Energy from the log-transformed convergence field: A logarithmic transform of the convergence field improves `the information
content', ie., the overall precision associated with the measurement of the
amplitude of the convergence power spectrum by improving the covariance matrix
properties. The translation of this improvement in the information content to
that in cosmological parameters, such as those associated with dark energy,
requires knowing the sensitivity of the log-transformed field to those
cosmological parameters. In this paper we use N-body simulations with ray
tracing to generate convergence fields at multiple source redshifts as a
function of cosmology. The gain in information associated with the
log-transformed field does lead to tighter constraints on dark energy
parameters, but only if shape noise is neglected. The presence of shape noise
quickly diminishes the advantage of the log mapping, more quickly than we would
expect based on the information content. With or without shape noise, using a
larger pixel size allows for a more efficient log-transformation. |
Cosmological Simulations of Two-Component Wave Dark Matter: Wave (fuzzy) dark matter ($\psi$DM) consists of ultralight bosons, featuring
a solitonic core within a granular halo. Here we extend $\psi$DM to two
components, with distinct particle masses $m$ and coupled only through gravity,
and investigate the resulting soliton-halo structure via cosmological
simulations. Specifically, we assume $\psi$DM contains $75$ per cent major
component and $25$ per cent minor component, fix the major-component particle
mass to $m_{\rm major}=1\times10^{-22}\,{\rm eV}$, and explore two different
minor-component particle masses with $m_{\rm major}:m_{\rm minor}=3:1$ and
$1:3$, respectively. For $m_{\rm major}:m_{\rm minor}=3:1$, we find that (i)
the major- and minor-component solitons coexist, have comparable masses, and
are roughly concentric. (ii) The soliton peak density is significantly lower
than the single-component counterpart, leading to a smoother soliton-to-halo
transition and rotation curve. (iii) The combined soliton mass of both
components follows the same single-component core-halo mass relation. In
dramatic contrast, for $m_{\rm major}:m_{\rm minor}=1:3$, a minor-component
soliton cannot form with the presence of a stable major-component soliton; the
total density profile, for both halo and soliton, is thus dominated by the
major component and closely follows the single-component case. To support this
finding, we propose a toy model illustrating that it is difficult to form a
soliton in a hot environment associated with a deep gravitational potential.
The work demonstrates the extra flexibility added to the multi-component
$\psi$DM model can resolve observational tensions over the single-component
model while retaining its key features. | Pressure Support vs. Thermal Broadening in the Lyman-alpha Forest I:
Effects of the Equation of State on Longitudinal Structure: In the low density intergalactic medium (IGM) that gives rise to the
Lyman-alpha forest, gas temperature and density are tightly correlated. The
velocity scale of thermal broadening and the Hubble flow across the gas Jeans
scale are of similar magnitude (Hlambda_J ~ sigma_th). To separate the effects
of gas pressure support and thermal broadening on the Lya forest, we compare
spectra extracted from two smoothed particle hydrodynamics (SPH) simulations
evolved with different photoionization heating rates (and thus different Jeans
scales), imposing different temperature-density relations on the evolved
particle distributions. The turnover scales in the flux power spectrum and flux
autocorrelation function are determined mainly by thermal broadening rather
than pressure. However, the insensitivity to pressure arises partly from a
cancellation effect with a sloped temperature-density relation (T ~ rho^{0.6}
in our simulations): the high density peaks in the colder, lower pressure
simulation are less smoothed by pressure support than in the hotter simulation,
and it is this higher density gas that experiences the strongest thermal
broadening. Changes in thermal broadening and pressure support have comparably
important effects on the flux probability distribution (PDF), which responds
directly to the gas overdensity distribution rather than the scale on which it
is smooth. Tests on a lower resolution simulation show that our statistical
results are converged even at this lower resolution. While thermal broadening
generally dominates the longitudinal structure in the Lya forest, we show in
Paper II that pressure support determines the transverse coherence of the
forest observed towards close quasar pairs. [ABRIDGED] |
Dark Matter Density Profiles in Dwarf Galaxies: Linking Jeans Modeling
Systematics and Observation: The distribution of dark matter in dwarf galaxies can have important
implications on our understanding of galaxy formation as well as the particle
physics properties of dark matter. However, accurately characterizing the dark
matter content of dwarf galaxies is challenging due to limited data and complex
dynamics that are difficult to accurately model. In this paper, we apply
spherical Jeans modeling to simulated stellar kinematic data of spherical,
isotropic dwarf galaxies with the goal of identifying the future observational
directions that can improve the accuracy of the inferred dark matter
distributions in the Milky Way dwarf galaxies. We explore how the dark matter
inference is affected by the location and number of observed stars as well as
the line-of-sight velocity measurement errors. We use mock observation to
demonstrate the difficulty in constraining the inner core/cusp of the dark
matter distribution with datasets of fewer than 10,000 stars. We also
demonstrate the need for additional measurements to make robust estimates of
the expected dark matter annihilation signal strength. For the purpose of
deriving robust indirect detection constraints, we identify Ursa Major II, Ursa
Minor, and Draco as the systems that would most benefit from additional stars
being observed. | Mapping Luminous Blue Compact Galaxies with VIRUS-P: morphology, line
ratios and kinematics: [abridged] We carry out an integral field spectroscopy (IFS) study of a
sample of luminous BCGs, with the aim to probe the morphology, kinematics, dust
extinction and excitation mechanisms of their warm interstellar medium (ISM).
IFS data for five luminous BCGs were obtained using VIRUS-P, the prototype
instrument for the Visible Integral Field Replicable Unit Spectrograph,
attached to the 2.7m Harlan J. Smith Telescope at the McDonald Observatory.
VIRUS-P consists of a square array of 247 optical fibers, which covers a
109"x109" field of view, with a spatial sampling of 4.2" and a 0.3 filling
factor. We observed in the 3550-5850 Angstrom spectral range, with a resolution
of 5 A FWHM. From these data we built two-dimensional maps of the continuum and
the most prominent emission-lines ([OII]3727, Hgamma, Hbeta and [OIII]5007),
and investigate the morphology of diagnostic emission-line ratios and the
extinction patterns in the ISM as well as stellar and gas kinematics.
Additionally, from integrated spectra we infer total line fluxes and
luminosity-weighted extinction coefficients and gas-phase metallicities. All
galaxies exhibit an overall regular morphology in the stellar continuum, while
their warm ISM morphology is more complex: in II Zw 33 and Mrk 314, the
star-forming regions are aligned along a chain-structure; Haro 1, NGC 4670 and
III Zw 102 display several salient features, such as extended gaseous filaments
and bubbles. A significant intrinsic absorption by dust is present in all
galaxies, the most extreme case being III Zw 102. Our data reveal a manifold of
kinematical patterns, from overall regular gas and stellar rotation to complex
velocity fields produced by structurally and kinematically distinct components. |
AGN obscuration from winds: from dusty infrared-driven to warm and X-ray
photoionized: We present calculations of AGN winds at ~parsec scales, along with the
associated obscuration. We take into account the pressure of infrared radiation
on dust grains and the interaction of X-rays from a central black hole with hot
and cold plasma. Infrared radiation (IR) is incorporated in
radiation-hydrodynamic simulations adopting the flux-limited diffusion
approximation. We find that in the range of X-ray luminosities L=0.05 - 0.6
L_edd, the Compton-thick part of the flow (aka torus) has an opening angle of
approximately 72-75 degrees regardless of the luminosity. At L > 0.1 L_edd the
outflowing dusty wind provides the obscuration with IR pressure playing a major
role. The global flow consists of two phases: the cold flow at inclinations
\theta > 70 degrees and a hot, ionized wind of lower density at lower
inclinations. The dynamical pressure of the hot wind is important in shaping
the denser IR supported flow. At luminosities <0.1 L_edd episodes of outflow
are followed by extended periods when the wind switches to slow accretion. | Hunting Galactic Axion Dark Matter with Gravitationally Lensed Fast
Radio Bursts: Ultralight axion or axionlike particles are one of the most promising
candidates for dark matter because they are a well-motivated solution for the
theoretical strong $CP$ problem and observational issues on small scales, i.e.
the core-cusp problem and the satellite problem. A tiny coupling of axions and
photons induces birefringence. We propose the differential birefringence
measurements of multiple images of gravitationally lensed fast radio burst
(FRB) systems as probes of the Galactic axion dark matter (ADM) background. In
addition to general advantages of lensing systems, i.e. alleviating systematics
and intrinsic astrophysical dependencies, precise measurements of lensing time
delay and polarization angle in gravitationally lensed FRB systems make them a
more robust and powerful probe. We show that, with a single lensed FRB system
(which may be detected in large numbers in the SKA era), the axion-photon
coupling under the ADM background could be constrained to be $g_{a\gamma} < 7.3
\times 10^{-11}~ \mathrm{GeV^{-1}}$ for an axion mass
$m_a\sim10^{-20}~\mathrm{eV}$. This will be of great significance in achieving
synergistic searches of the Galactic ADM with other astrophysical probes and
laboratorial experiments. |
Constraints on cosmological parameters from Planck and BICEP2 data: We show that the tension introduced by the detection of large amplitude
gravitational wave power by the BICEP2 experiment with temperature anisotropy
measurements by the Planck mission is alleviated in models where extra light
species contribute to the effective number of relativistic degrees of freedom.
We also show that inflationary models based on S-dual potentials are in
agreement with Planck and BICEP2 data. | Metal-poor Galaxies in the Local Universe: A galaxy's mean metallicity is usually closely correlated with its luminosity
and mass. Consequently the most metal-poor galaxies in the local universe are
dwarf galaxies. Blue compact dwarfs and tidal dwarfs tend to deviate from the
metallicity-luminosity relation by being too metal-poor or too metal-rich for
their luminosity, respectively. A less pronounced offset separates dwarf
spheroidal (dSph) and dwarf irregular galaxies, making the former too
metal-rich for their luminosity, which indicates different formation conditions
for these two types of dwarfs. While environment (photo-evaporation through
local re-ionization by massive galaxies, tidal and ram pressure stripping)
govern the observed morphology-distance relation, intrinsic properties (in
particular total mass) play a decisive role in dwarf galaxy evolution with
respect to the time and duration of star formation and the amount of
enrichment. The metallicity distribution functions of nearby dwarfs can be
understood taking pre-enrichment, gas infall, and winds into account. Many
dwarfs show evidence for inhomogeneous, localized enrichment. Ultra-faint
dSphs, which may have formed their metal-poor stars at high redshift via H2
cooling, show an overabundance of metal-deficient stars as compared to the
(inner) Galactic halo, but may, along with classical dSphs, have contributed
significantly to the build-up of the outer halo. The abundance ratios measured
in the irregular Large Magellanic Cloud are consistent with the postulated
early accretion of irregulars to form the inner Galactic halo. |
Fundamental physics with ESPRESSO: a new determination of the D/H ratio
towards PKS1937-101: Primordial abundances of light elements are sensitive to the physics of the
early Universe and can directly constrain cosmological quantities, such as the
baryon-to-photon ratio $\eta_{10}$, the baryon density and the number of
neutrino families. Deuterium is especially suited for these studies: its
primordial abundance is sensitive and monotonically dependent on $\eta_{10}$,
allowing an independent measurement of the cosmic baryon density that can be
compared, for instance, against the Planck satellite data. The primordial
deuterium abundance can be measured in high $H_I$ column density absorption
systems towards distant quasars. We report here a new measurement, based on
high-resolution ESPRESSO data, of the primordial $D_I$ abundance of a system at
redshift $z \sim 3.572$, towards PKS1937-101. Using only ESPRESSO data, we find
a D/H ratio of $2.638\pm0.128 \times 10^{-5}$, while including the available
UVES data improves the precision, leading to a ratio of $2.608 \pm 0.102 \times
10^{-5}$. The results of this analysis agree with those of the most precise
existing measurements. We find that the relatively low column density of this
system ($\log{N_{\rm H_I}/ {\rm cm}^{-2}}\sim18 $) introduces modelling
uncertainties, which become the main contributor to the error budget. | Using galaxy-galaxy weak lensing measurements to correct the
Finger-of-God: For decades, cosmologists have been using galaxies to trace the large-scale
distribution of matter. At present, the largest source of systematic
uncertainty in this analysis is the challenge of modeling the complex
relationship between galaxy redshift and the distribution of dark matter. If
all galaxies sat in the centers of halos, there would be minimal Finger-of-God
(FoG) effects and a simple relationship between the galaxy and matter
distributions. However, many galaxies, even some of the luminous red galaxies
(LRGs), do not lie in the centers of halos. Because the galaxy-galaxy lensing
is also sensitive to the off-centered galaxies, we show that we can use the
lensing measurements to determine the amplitude of this effect and to determine
the expected amplitude of FoG effects. We develop an approach for using the
lensing data to model how the FoG suppresses the power spectrum amplitudes and
show that the current data implies a 30% suppression at wavenumber k=0.2h/Mpc.
Our analysis implies that it is important to complement a spectroscopic survey
with an imaging survey with sufficient depth and wide field coverage. Joint
imaging and spectroscopic surveys allow a robust, unbiased use of the power
spectrum amplitude information: it improves the marginalized error of growth
rate fg=dln D/dln a by up to a factor of 2 over a wide range of redshifts
z<1.4. We also find that the dark energy equation-of-state parameter, w0, and
the neutrino mass, fnu, can be unbiasedly constrained by combining the lensing
information, with an improvement of 10--25% compared to a spectroscopic survey
without lensing calibration. |
The Halo Bispectrum in N-body Simulations with non-Gaussian Initial
Conditions: We present measurements of the bispectrum of dark matter halos in numerical
simulations with non-Gaussian initial conditions of the local type. We show, in
the first place, that the overall effect of primordial non-Gaussianity on the
halo bispectrum is larger than on the halo power spectrum when all measurable
configurations are taken into account. We then compare our measurements with a
tree-level perturbative prediction finding good agreement at large scale when
the constant Gaussian bias parameter, both linear and quadratic, and their
constant non-Gaussian corrections are fitted for. The best-fit values of the
Gaussian bias factors and their non-Gaussian, scale-independent corrections are
in qualitative agreement with the peak-background split expectations. In
particular, we show that the effect of non-Gaussian initial conditions on
squeezed configurations is fairly large (up to 30% for f_NL=100 at redshift
z=0.5) and results from contributions of similar amplitude induced by the
initial matter bispectrum, scale-dependent bias corrections as well as from
nonlinear matter bispectrum corrections. We show, in addition, that effects at
second order in f_NL are irrelevant for the range of values allowed by CMB and
galaxy power spectrum measurements, at least on the scales probed by our
simulations. Finally, we present a Fisher matrix analysis to assess the
possibility of constraining primordial non-Gaussianity with future measurements
of the galaxy bispectrum. We find that a survey with a volume of about 10 cubic
Gpc at mean redshift z ~ 1 could provide an error on f_NL of the order of a
few. This shows the relevance of a joint analysis of galaxy power spectrum and
bispectrum in future redshift surveys. | Dark Energy Induced Anisotropy in Cosmic Expansion: In order to understand the nature of the accelerating expansion of the
late-time universe, it is important to experimentally determine whether dark
energy is a cosmological constant or dynamical in nature. If dark energy
already exists prior to inflation, which is a reasonable assumption, then one
expects that a dynamical dark energy would leave some footprint in the
anisotropy of the late-time accelerated expansion. To demonstrate the viability
of this notion, we invoke the quintessence field with the exponential potential
as one of the simplest dynamical dark energy models allowed by observations. We
investigate the effects of its quantum fluctuations (the physical origin of the
perturbation being isocurvature) generated during inflation and having fully
positive correlation with the primordial curvature perturbations, and estimate
the anisotropy of the cosmic expansion so induced. We show that the primordial
amplitude of quantum fluctuations of quintessence field {\delta\phi}_P can be
related to the tensor-to-scalar ratio r, and we calculate the perturbed
luminosity distance to first order and the associated luminosity distance power
spectrum, which is an estimator of anisotropicity of late-time accelerated
expansion. We find that the gravitational potential at large scales and late
times is less decayed in QCDM compared to that in {\Lambda}CDM so that the
smaller the redshift and multipole, the more relative deficit of power in QCDM.
Our results of luminosity distance power spectrum also show the similar
conclusions of suppression as that of the previous investigation regarding the
effect of quantum fluctuations of quintessence field on the CMB temperature
anisotropies. |
Effective dark matter power spectra in $f(R)$ gravity: Using N-body simulations, we measure the power spectrum of the effective dark
matter density field, which is defined through the modified Poisson equation in
$f(R)$ cosmologies. We find that when compared to the conventional dark matter
power spectrum, the effective power spectrum deviates more significantly from
the $\Lambda$CDM model. For models with $f_{R0}=-10^{-4}$, the deviation can
exceed 150\% while the deviation of the conventional matter power spectrum is
less than 50\%. Even for models with $f_{R0}=-10^{-6}$, for which the
conventional matter power spectrum is very close to the $\Lambda$CDM
prediction, the effective power spectrum shows sizeable deviations. Our results
indicate that traditional analyses based on the dark matter density field may
seriously underestimate the impact of $f(R)$ gravity on galaxy clustering. We
therefore suggest the use of the effective density field in such studies. In
addition, based on our findings, we also discuss several possible methods of
making use of the differences between the conventional and effective dark
matter power spectra in $f(R)$ gravity to discriminate the theory from the
$\Lambda$CDM model. | CRASH3: cosmological radiative transfer through metals: Here we introduce CRASH3, the latest release of the 3D radiative transfer
code CRASH. In its current implementation CRASH3 integrates into the reference
algorithm the code Cloudy to evaluate the ionisation states of metals,
self-consistently with the radiative transfer through H and He. The feedback of
the heavy elements on the calculation of the gas temperature is also taken into
account, making of CRASH3 the first 3D code for cosmological applications which
treats self-consistently the radiative transfer through an inhomogeneous
distribution of metal enriched gas with an arbitrary number of point sources
and/or a background radiation. The code has been tested in idealized
configurations, as well as in a more realistic case of multiple sources
embedded in a polluted cosmic web. Through these validation tests the new
method has been proven to be numerically stable and convergent. We have studied
the dependence of the results on a number of physical quantities such as the
source characteristics (spectral range and shape, intensity), the metal
composition, the gas number density and metallicity. |
Spectrophotometric time series of SN 2011fe from the Nearby Supernova
Factory: We present 32 epochs of optical (3300-9700 \AA) spectrophotometric
observations of the nearby quintessential "normal" type Ia supernova (SN Ia) SN
2011fe in the galaxy M101, extending from -15 to +97 d with respect to B-band
maximum, obtained by the Nearby Supernova Factory collaboration. SN 2011fe is
the closest (\mu = 29.04) and brightest (Bmax = 9.94 mag) SN Ia observed since
the advent of modern large scale programs for the intensive periodic followup
of supernovae. Both synthetic light curve measurements and spectral feature
analysis attest to the normality of SN 2011fe. There is very little evidence
for reddening in its host galaxy. The homogeneous calibration, intensive time
sampling, and high signal-to-noise ratio of the data set make it unique. Thus
it is ideal for studying the physics of SN Ia explosions in detail, and for
furthering the use of SNe Ia as standardizable candles for cosmology. Several
such applications are shown, from the creation of a bolometric light curve and
measurement of the 56Ni mass, to the simulation of detection thresholds for
unburned carbon, direct comparisons with other SNe Ia, and existing spectral
templates. | Joint analysis of DES Year 3 data and CMB lensing from SPT and Planck
II: Cross-correlation measurements and cosmological constraints: Cross-correlations of galaxy positions and galaxy shears with maps of
gravitational lensing of the cosmic microwave background (CMB) are sensitive to
the distribution of large-scale structure in the Universe. Such
cross-correlations are also expected to be immune to some of the systematic
effects that complicate correlation measurements internal to galaxy surveys. We
present measurements and modeling of the cross-correlations between galaxy
positions and galaxy lensing measured in the first three years of data from the
Dark Energy Survey with CMB lensing maps derived from a combination of data
from the 2500 deg$^2$ SPT-SZ survey conducted with the South Pole Telescope and
full-sky data from the Planck satellite. The CMB lensing maps used in this
analysis have been constructed in a way that minimizes biases from the thermal
Sunyaev Zel'dovich effect, making them well suited for cross-correlation
studies. The total signal-to-noise of the cross-correlation measurements is
23.9 (25.7) when using a choice of angular scales optimized for a linear
(nonlinear) galaxy bias model. We use the cross-correlation measurements to
obtain constraints on cosmological parameters. For our fiducial galaxy sample,
which consist of four bins of magnitude-selected galaxies, we find constraints
of $\Omega_{m} = 0.272^{+0.032}_{-0.052}$ and $S_{8} \equiv \sigma_8
\sqrt{\Omega_{m}/0.3}= 0.736^{+0.032}_{-0.028}$ ($\Omega_{m} =
0.245^{+0.026}_{-0.044}$ and $S_{8} = 0.734^{+0.035}_{-0.028}$) when assuming
linear (nonlinear) galaxy bias in our modeling. Considering only the
cross-correlation of galaxy shear with CMB lensing, we find $\Omega_{m} =
0.270^{+0.043}_{-0.061}$ and $S_{8} = 0.740^{+0.034}_{-0.029}$. Our constraints
on $S_8$ are consistent with recent cosmic shear measurements, but lower than
the values preferred by primary CMB measurements from Planck. |
dm2gal: Mapping Dark Matter to Galaxies with Neural Networks: Maps of cosmic structure produced by galaxy surveys are one of the key tools
for answering fundamental questions about the Universe. Accurate theoretical
predictions for these quantities are needed to maximize the scientific return
of these programs. Simulating the Universe by including gravity and
hydrodynamics is one of the most powerful techniques to accomplish this;
unfortunately, these simulations are very expensive computationally.
Alternatively, gravity-only simulations are cheaper, but do not predict the
locations and properties of galaxies in the cosmic web. In this work, we use
convolutional neural networks to paint galaxy stellar masses on top of the dark
matter field generated by gravity-only simulations. Stellar mass of galaxies
are important for galaxy selection in surveys and thus an important quantity
that needs to be predicted. Our model outperforms the state-of-the-art
benchmark model and allows the generation of fast and accurate models of the
observed galaxy distribution. | Green's function of the cosmological thermalization problem: Energy release in the early Universe leads to spectral distortions of the
cosmic microwave background (CMB) which in the future might allow probing
different physical processes in the pre-recombination (z>~10^3) epoch.
Depending on the energy injection history, the associated distortion partially
thermalizes due to the combined action of Compton scattering, double Compton
scattering and Bremsstrahlung emission, a problem that in general is hard to
solve. Various analytic approximations describing the resulting distortion
exist, however, for small distortions and fixed background cosmology the
Green's function of the problem can be pre-computed numerically. Here we show
that this approach gives very accurate results for a wide range of thermal
histories, allowing fast and quasi-exact computation of the spectral distortion
given the energy release rate. Our method is thus useful for forecasts of
possible constraints on early-universe physics obtained from future
measurements of the CMB spectrum. |
Evolution of Infrared Luminosity functions of Galaxies in the AKARI
NEP-Deep field: Revealing the cosmic star formation history hidden by dust: Dust-obscured star-formation becomes much more important with increasing
intensity, and increasing redshift. We aim to reveal cosmic star-formation
history obscured by dust using deep infrared observation with the AKARI.
We construct restframe 8um, 12um, and total infrared (TIR) luminosity
functions (LFs) at 0.15<z<2.2 using 4128 infrared sources in the AKARI NEP-Deep
field. A continuous filter coverage in the mid-IR wavelength (2.4, 3.2, 4.1, 7,
9, 11, 15, 18, and 24um) by the AKARI satellite allows us to estimate restframe
8um and 12um luminosities without using a large extrapolation based on a SED
fit, which was the largest uncertainty in previous work. We have found that all
8um (0.38<z<2.2), 12um (0.15<z<1.16), and TIR LFs (0.2<z<1.6), show a
continuous and strong evolution toward higher redshift. In terms of cosmic
infrared luminosity density (Omega_IR), which was obtained by integrating
analytic fits to the LFs, we found a good agreement with previous work at
z<1.2, and that the Omega_IR evolves as propto (1+z)^4.4+-1.0. When we separate
contributions to Omega_IR by LIRGs and ULIRGs, we found more IR luminous
sources are increasingly more important at higher redshift. We found that the
ULIRG (LIRG) contribution increases by a factor of 10 (1.8) from z=0.35 to
z=1.4. | Consistent initial data for CMD perturbations: We investigate the initial condition which are simultaneously consistent with
perturbation equations in both the radiation-dominated and the mater-dominated
epochs. The exact formula for the spectrum transfer-function is derived. |
Cosmic Shear with Einstein Rings: We explore a new technique to measure cosmic shear using Einstein rings. In
Birrer et al. (2017), we showed that the detailed modelling of Einstein rings
can be used to measure external shear to high precision. In this letter, we
explore how a collection of Einstein rings can be used as a statistical probe
of cosmic shear. We present a forecast of the cosmic shear information
available in Einstein rings for different strong lensing survey configurations.
We find that, assuming that the number density of Einstein rings in the COSMOS
survey is representative, future strong lensing surveys should have a
cosmological precision comparable to the current ground based weak lensing
surveys. We discuss how this technique is complementary to the standard cosmic
shear analyses since it is sensitive to different systematic and can be used
for cross-calibration. | Testing modified gravity scenarios with direct peculiar velocities: The theoretical basis of dark energy remains unknown and could signify a need
to modify the laws of gravity on cosmological scales. In this study we
investigate how the clustering and motions of galaxies can be used as probes of
modified gravity theories, using galaxy and direct peculiar velocity auto- and
cross-correlation functions. We measure and fit these correlation functions in
simulations of $\Lambda$CDM, DGP, and $f(R)$ cosmologies and, by extracting the
characteristic parameters of each model, we show that these theories can be
distinguished from General Relativity using these measurements. We present
forecasts showing that with sufficiently large data samples, this analysis
technique is a competitive probe that can help place limits on allowed
deviations from GR. For example, a peculiar velocity survey reaching to $z=0.5$
with $20\%$ distance accuracy would constrain model parameters to 3-$\sigma$
confidence limits $\log_{10}|f_{R0}| < -6.45$ for $f(R)$ gravity and $r_c >
2.88 \, c/H_0$ for nDGP, assuming a fiducial GR model. |
Ecology of dark matter haloes -II. Effects of interactions on the
alignment of halo pairs: We use the Horizon Run 4 cosmological N -body simulation to study the effects
of distant and close interactions on the alignments of the shapes, spins, and
orbits of targets haloes with their neighbours, and their dependence on the
local density environment and neighbour separation. Interacting targets have a
significantly lower spin and higher sphericity and oblateness than all targets.
Interacting pairs initially have anti-parallel spins, but the spins develop
parallel alignment as time goes on. Neighbours tend to evolve in the plane of
rotation of the target, and in the direction of the major axis of prolate
haloes. Moreover, interactions are preferentially radial, while pairs with
non-radial orbits are preferentially prograde. The alignment signals are
stronger at high-mass and for close separations, and independent on the
large-scale density. Positive alignment signals are found at redshifts up to 4,
and increase with decreasing redshifts. Moreover, the orbits tend to become
prograde at low redshift, while no alignment is found at high redshift (z = 4). | Dwarf Galaxy Sized Monopoles as Dark Matter?: We propose a model of dark matter: galaxy-sized 't Hooft-Polyakov magnetic
monopoles in a new, extraordinarily weakly coupled SU(2) gauge sector with an
adjoint Higgs field and two flavors of fundamental fermions. We fit the
parameters by asserting that the dark matter halos of the lightest dwarf
spheroidal (dSph) galaxies consist of a single charge Q=1 monopole. Lensing and
wide binary bounds are then easily satisfied and the monopoles form in time to
help with CMB fluctuations. In this model dSph and low surface brightness (LSB)
halos automatically have (1) A minimum mass - Dirac quantization solves the
missing satellite problem, (2) A constant density core (r<r_1), (3) An
intermediate regime (r_1<r<r_2) with density proportional to 1/r^2. The model
predicts that (A) r_1 is proportional to the stellar rotational/dispersion
velocities at r_1<r<r_2, (B) r_2 is reasonably Q independent and so dSph halos
extend at least ten times farther than their half-light and tidal radii, (C)
The minimal stellar dispersion is 1/sqrt{2} times the next-smallest allowed
value. A serious potential problem with our proposal is that non-BPS monopoles
are repulsive. The Jackiw-Rebbi mechanism yields four species of monopoles, and
we assume that, for some choice of Yukawa couplings, one species is light and
serves only to screen the repulsive interactions of another. |
Constraining Cluster Virialization Mechanism and Cosmology using
Thermal-SZ-selected clusters from Future CMB Surveys: We forecast the number of galaxy clusters that can be detected via the
thermal Sunyaev-Zeldovich (tSZ) signals by future cosmic microwave background
(CMB) experiments, primarily the wide area survey of the CMB-S4 experiment but
also CMB-S4's smaller delensing survey and the proposed CMB-HD experiment. We
predict that CMB-S4 will detect 75,000 clusters with its wide survey of $f_{\rm
sky}$ = 50% and 14,000 clusters with its deep survey of $f_{\rm sky}$ = 3%. Of
these, approximately 1350 clusters will be at $z \ge 2$, a regime that is
difficult to probe by optical or X-ray surveys. We assume CMB-HD will survey
the same sky as the S4-Wide{}, and find that CMB-HD will detect $\times3$ more
overall and an order of magnitude more $z \ge 2$ clusters than CMB-S4. These
results include galactic and extragalactic foregrounds along with atmospheric
and instrumental noise. Using CMB-cluster lensing to calibrate cluster tSZ-mass
scaling relation, we combine cluster counts with primary CMB to obtain
cosmological constraints for a two parameter extension of the standard model
($\Lambda CDM+\sum m_{\nu}+w_{0}$). Besides constraining $\sigma(w_{0})$ to
$\lesssim 1\%$, we find that both surveys can enable a $\sim 2.5-4.5\sigma$
detection of $\sum m_{\nu}$, substantially strengthening CMB-only constraints.
We also study the evolution of intracluster medium by modelling the cluster
virialization ${\rm v}(z)$ and find tight constraints from CMB-S4, with further
factors of 3-4 improvement for CMB-HD. The binned cluster counts, Fisher
matrices, and other associated products can be downloaded from
https://github.com/sriniraghunathan/tSZ_cluster_forecasts. | The impact of the Universe's expansion rate on constraints on modified
growth of structure: In the context of modified gravity, at linear level, the growth of structure
in the Universe will be affected by modifications to the Poisson equation and
by the background expansion rate of the Universe. It has been shown that these
two effects lead to a degeneracy which must be properly accounted for if one is
to place reliable constraints on new forces on large scales or, equivalently,
modifications to General Relativity. In this paper we show that current
constraints are such that assumptions about the background expansion have
little impact on constraints on modifications to gravity. We do so by
considering the background of a $\Lambda$ Cold Dark Matter ($\Lambda$CDM)
universe, a universe with a more general equation of state for the dark energy,
and finally, a general, model-independent, expansion rate. We use Gaussian
Processes to model modifications to Poisson's equation and, in the case of a
general expansion rate, to model the redshift dependent Hubble rate. We
identify a degeneracy between modifications to Poisson's equation and the
background matter density, $\Omega_M$, which can only be broken by assuming a
model-dependent expansion rate. We show that, with current data, the
constraints on modifications to the Poisson equation via measurements of the
growth rate range between $10-20\%$ depending on the strength of our
assumptions on the Universe's expansion rate. |
Distribution of the heavy elements throughout the extended narrow line
region of the Seyfert galaxy NGC 7212: The latest observations of line and continuum spectra emitted from the
extended narrow line region (ENLR) of the Seyfert 2 galaxy NGC 7212 are
analysed using models accounting for photoionization from the active nucleus
and shocks. The results show that relatively high (500--800 \kms) shock
velocities appear on the edge of the cone and outside of it. The model-inferred
AGN flux, which is lower than $10^{-11}$ photons cm$^{-2}$ s$^{-1}$ eV$^{-1}$
at the Lyman limit, is more typical of low-luminosity AGN, and less so for
Seyfert 2 galaxies. The preshock densities are characteristic of the ENLR and
range between 80--150 cm$^{-3}$. Nitrogen and sulphur are found depleted by a
factor lower than 2, particularly at the eastern edge. Oxygen is depleted at
several locations. The Fe/H ratio is approximately solar, whereas the Ne/H
relative abundance is unusually high, 1.5--2 times the solar value. Modelling
the continuum spectral energy distribution (SED), we have found radio
synchrotron radiation generated by the Fermi mechanism at the shock front,
whereas the X-rays are produced by the bremsstrahlung from a relatively high
temperature plasma. | Large Scale Structure of the Universe: Galaxies are not uniformly distributed in space. On large scales the Universe
displays coherent structure, with galaxies residing in groups and clusters on
scales of ~1-3 Mpc/h, which lie at the intersections of long filaments of
galaxies that are >10 Mpc/h in length. Vast regions of relatively empty space,
known as voids, contain very few galaxies and span the volume in between these
structures. This observed large scale structure depends both on cosmological
parameters and on the formation and evolution of galaxies. Using the two-point
correlation function, one can trace the dependence of large scale structure on
galaxy properties such as luminosity, color, stellar mass, and track its
evolution with redshift. Comparison of the observed galaxy clustering
signatures with dark matter simulations allows one to model and understand the
clustering of galaxies and their formation and evolution within their parent
dark matter halos. Clustering measurements can determine the parent dark matter
halo mass of a given galaxy population, connect observed galaxy populations at
different epochs, and constrain cosmological parameters and galaxy evolution
models. This chapter describes the methods used to measure the two-point
correlation function in both redshift and real space, presents the current
results of how the clustering amplitude depends on various galaxy properties,
and discusses quantitative measurements of the structures of voids and
filaments. The interpretation of these results with current theoretical models
is also presented. |
MOND reveals the thermodynamics of gravity: We show that treating gravitation as a thermodynamical theory leads to the
modified Newton dynamics (MOND) equations if one takes into account the
Hubble's expansion. Then the universal MOND acceleration a0 is exactly twice
the product of the light velocity c and the Hubble constant H. No dark matter
is needed for the description of the galaxy rotational curves as well as for
the accounting for the additional gravitational lensing at large distances. | Effects of Anisotropic Stress in Interacting Dark Matter - Dark Energy
Scenarios: We study a novel interacting dark energy $-$ dark matter scenario where the
anisotropic stress of the large scale inhomogeneities is considered. The dark
energy has a constant equation of state and the interaction model produces
stable perturbations. The resulting picture is constrained using different
astronomical data aiming to measure the impact of the anisotropic stress on the
cosmological parameters. Our analyses show that a non-zero interaction in the
dark sector is allowed while a non-interaction scenario is recovered within
68\% CL. The anisotropic stress is also constrained to be small, and its zero
value is permitted within 68\% CL. The dark energy equation of state, $w_x$, is
also found to be close to `$-1$' boundary. However, from the ratio of the CMB
TT spectra, we see that the model has a mild deviation from the $\Lambda$CDM
cosmology while such deviation is almost forbidden from the CMB TT spectra
alone. Although the deviation is not much significant, but from the present
data, we cannot exclude such deviation. Overall, at the background level, the
model is close to the $\Lambda$CDM cosmology while at the level of
perturbations, a non-zero but a very small interaction in the dark sector is
permitted. Perhaps, a more accurate conclusion can be made with the next
generation of surveys. We also found that the region $w_x < -1$, is found to be
effective to release the tension on $H_0$. Finally, from the Bayesian analysis,
we find that $\Lambda$CDM remains in still preferred over the interacting
scenarios. |
Euclid preparation. XXXI. The effect of the variations in photometric
passbands on photometric-redshift accuracy: The technique of photometric redshifts has become essential for the
exploitation of multi-band extragalactic surveys. While the requirements on
photo-zs for the study of galaxy evolution mostly pertain to the precision and
to the fraction of outliers, the most stringent requirement in their use in
cosmology is on the accuracy, with a level of bias at the sub-percent level for
the Euclid cosmology mission. A separate, and challenging, calibration process
is needed to control the bias at this level of accuracy. The bias in photo-zs
has several distinct origins that may not always be easily overcome. We
identify here one source of bias linked to the spatial or time variability of
the passbands used to determine the photometric colours of galaxies. We first
quantified the effect as observed on several well-known photometric cameras,
and found in particular that, due to the properties of optical filters, the
redshifts of off-axis sources are usually overestimated. We show using simple
simulations that the detailed and complex changes in the shape can be mostly
ignored and that it is sufficient to know the mean wavelength of the passbands
of each photometric observation to correct almost exactly for this bias; the
key point is that this mean wavelength is independent of the spectral energy
distribution of the source}. We use this property to propose a correction that
can be computationally efficiently implemented in some photo-z algorithms, in
particular template-fitting. We verified that our algorithm, implemented in the
new photo-z code Phosphoros, can effectively reduce the bias in photo-zs on
real data using the CFHTLS T007 survey, with an average measured bias Delta z
over the redshift range 0.4<z<0.7 decreasing by about 0.02, specifically from
Delta z~0.04 to Delta z~0.02 around z=0.5. Our algorithm is also able to
produce corrected photometry for other applications. | Metal abundances in the high-redshift intergalactic medium: Twenty years of high-resolution spectroscopy at the 8-10 m class telescopes
have drastically expanded our view of the gas-phase metallicity in the z>2
universe. This contribution briefly summarizes how these studies reveal a
widespread metal pollution in the intergalactic medium with a median abundance
[C/H] ~ -3.5 at z~3 that is increasing by a factor of ~2-3 from z~4.3 to z~2.4.
At the higher densities that are typical of galactic halos, observations
uncover a metallicity spread of five orders of magnitude in Lyman limit
systems, ranging from super-solar ([M/H]~+0.7) to pristine ([M/H]< -4) gas
clouds. Finally, the neutral damped Ly-alpha systems are enriched to a median
metallicity of [M/H] ~ -1.5 that slowly declines with redshift up to z ~ 4.5,
at which point it appears to more rapidly evolve as one approaches the end of
reionization. |
Tests of Neutrino and Dark Radiation Models from Galaxy and CMB surveys: We analyze the ability of galaxy and CMB lensing surveys to constrain massive
neutrinos and new models of dark radiation. We present a Fisher forecast
analysis for neutrino mass constraints with the LSST galaxy survey and the CMB
S4 survey. A joint analysis of the three galaxy and shear 2-point functions,
along with key systematics parameters and Planck priors, constrains the
neutrino masses to $\sum m_\nu = 0.041\,$eV at 1-$\sigma$ level, comparable to
constraints expected from Stage 4 CMB lensing. If low redshift information from
upcoming spectroscopic surveys like DESI is included, the constraint becomes
$\sum m_\nu = 0.032\,$eV. These constraints are derived having marginalized
over the number of relativistic species ($N_{\rm eff}$), which is somewhat
degenerate with the neutrino mass. We also explore the gain by combining LSST
and CMB S4, that is, using the five relevant auto- and cross-correlations of
the two datasets. We conclude that advances in modeling the nonlinear regime
and the measurements of other parameters are required to ensure a neutrino mass
detection. Using the same datasets, we explore the ability of LSST-era surveys
to test "nonstandard" models with dark radiation. We find that if evidence for
dark radiation is found from $N_{\rm eff}$ measurements, the mass of the dark
radiation candidate can be measured at a 1-$\sigma$ level of $0.162\,$eV for
fermionic dark radiation, and $0.137\,$eV for bosonic dark radiation, for
$\Delta N_{\rm eff} = 0.15$. We also find that the NNaturalness model of
Arkani-Hamed et al 2016, with extra light degrees of freedom, has a sub-percent
effect on the power spectrum: even more ambitious surveys than the ones
considered here will be needed to test such models. | Reinterpreting Low Frequency LIGO/Virgo Events as Magnified Stellar-Mass
Black Holes at Cosmological Distances: Gravitational waves can be focussed by the gravity of an intervening galaxy,
just like light, thereby magnifying binary merging events in the far Universe.
High magnification by galaxies is found to be responsible for the brightest
sources detected in sky surveys, but the low angular resolution of LIGO/Virgo
is insufficient to check this lensing possibility directly. Here we find that
the first six binary black hole (BBH) merging events reported by LIGO/Virgo
show clear evidence for lensing in the plane of observed mass and source
distance. The four lowest frequency events follow an apparent locus in this
plane, which we can reproduce by galaxy lensing, where the higher the
magnification, the generally more distant the source so the wave train is
stretched more by the Universal expansion, by factors of 2-4. This revises the
reported BBH distances upwards by an order of magnitude, equal to the square
root of the magnification. Furthermore, the reported black hole masses must be
decreased by 2-4 to counter the larger stretch factor, since the orbital
frequency is used to derive the black hole masses. This lowers the masses to
5-15 solar masses, well below the puzzlingly high values of 20-35 solar masses
otherwise estimated, with the attraction of finding agreement in mass with
black holes orbiting stars in our own Galaxy, thereby implying a stellar origin
for the low frequency events in the far Universe. We also show that the other
two BBH events of higher frequency detected by LIGO/VIRGO, lie well below the
lensing locus, consistent with being nearby and unlensed. If this apparent
division between local and distant lensed events is reinforced by new
detections then the spins and masses of stellar black holes can be compared
over a timespan of 10 billion years by LIGO/Virgo. |
Impacts of dark energy on weighing neutrinos after Planck 2015: We investigate how dark energy properties impact the cosmological limits on
the total mass of active neutrinos. We consider two typical, simple dark energy
models (that have only one more additional parameter than $\Lambda$CDM), i.e.,
the $w$CDM model and the holographic dark energy (HDE) model, as examples, to
make an analysis. In the cosmological fits, we use the Planck 2015 temperature
and polarization data, in combination with other low-redshift observations,
including the baryon acoustic oscillations, type Ia supernovae, and Hubble
constant measurement, as well as the Planck lensing measurements. We find that,
once dynamical dark energy is considered, the degeneracy between $\sum m_\nu$
and $H_0$ will be changed, i.e., in the $\Lambda$CDM model, $\sum m_\nu$ is
anti-correlated with $H_0$, but in the $w$CDM and HDE models, $\sum m_\nu$
becomes positively correlated with $H_0$. Compared to $\Lambda$CDM, in the
$w$CDM model the limit on $\sum m_\nu$ becomes much looser, but in the HDE
model the limit becomes much tighter. In the HDE model, we obtain $\sum
m_\nu<0.113$ eV ($95\%$ CL) with the combined data sets, which is perhaps the
most stringent upper limit by far on neutrino mass. Thus, our result in the HDE
model is nearly ready to diagnose the neutrino mass hierarchy with the current
cosmological observations. | The Carina Project. V. The impact of NLTE effects on the iron content: We have performed accurate iron abundance measurements for 44 red giants
(RGs) in the Carina dwarf spheroidal (dSph) galaxy. We used archival,
high-resolution spectra (R~38,000) collected with UVES at ESO/VLT either in
slit mode (5) or in fiber mode (39, FLAMES/GIRAFFE-UVES). The sample is more
than a factor of four larger than any previous spectroscopic investigation of
stars in dSphs based on high-resolution (R>38,000) spectra. We did not impose
the ionization equilibrium between neutral and singly-ionized iron lines. The
effective temperatures and the surface gravities were estimated by fitting
stellar isochrones in the V, B-V color-magnitude diagram. To measure the iron
abundance of individual lines we applied the LTE spectrum synthesis fitting
method using MARCS model atmospheres of appropriate metallicity. We found
evidence of NLTE effects between neutral and singly-ionized iron abundances.
Assuming that the FeII abundances are minimally affected by NLTE effects, we
corrected the FeI stellar abundances using a linear fit between FeI and FeII
stellar abundance determinations.
We found that the Carina metallicity distribution based on the corrected FeI
abundances (44 RGs) has a weighted mean metallicity of [Fe/H]=-1.80 and a
weighted standard deviation of sigma=0.24 dex. The Carina metallicity
distribution based on the FeII abundances (27 RGs) gives similar estimates
([Fe/H]=-1.72, sigma=0.24 dex). The current weighted mean metallicities are
slightly more metal poor when compared with similar estimates available in the
literature. Furthermore, if we restrict our analysis to stars with the most
accurate iron abundances, ~20 FeI and at least three FeII measurements (15
stars), we found that the range in iron abundances covered by Carina RGs (~1
dex) agrees quite well with similar estimates based on high-resolution spectra. |
On the redshift of the bright BL Lac object PKS 0048-097: Aims: The determination of elusive redshifts of bright BL Lac objects
Methods: We use the capabilities of newly available spectrograph X-Shooter at
European Southern Observatory (ESO) Very Large Telescope, that combines high
resolution and a large wavelength range, to obtain UVB to near-IR spectra of BL
Lacs. Results: Our observations of PKS 0048-097 detect three emission lines
that permit to derive a redshift z = 0.635. Moreover, a Mg II absorption system
at z = 0.154 that is associated with a foreground spiral galaxy at 50 Kpc
projected distance is found. Conclusions: The obtained redshift allows us to
comment about the optical beaming factor and the absorption of the high energy
spectrum by the Extragalactic Background Light. | Determine the galaxy bias factors on large scales using bispectrum
method: We study whether the bias factors of galaxies can be unbiasedly recovered
from their power spectra and bispectra. We use a set of numerical N-body
simulations and construct large mock galaxy catalogs based upon the
semi-analytical model of Croton et al. (2006). We measure the reduced bispectra
for galaxies of different luminosity, and determine the linear and first
nonlinear bias factors from their bispectra. We find that on large scales down
to that of the wavenumber k=0.1h/Mpc, the bias factors b1 and b2 are nearly
constant, and b1 obtained with the bispectrum method agrees very well with the
expected value. The nonlinear bias factor b2 is negative, except for the most
luminous galaxies with M<-23 which have a positive b2. The behavior of b2 of
galaxies is consistent with the b2 mass dependence of their host halos. We show
that it is essential to have an accurate estimation of the dark matter
bispectrum in order to have an unbiased measurement of b1 and b2. We also test
the analytical approach of incorporating halo occupation distribution to model
the galaxy power spectrum and bispectrum. The halo model predictions do not fit
the simulation results well on the precision requirement of current
cosmological studies. |
Detecting the cosmological neutrino background in the CMB: Three relativistic particles in addition to the photon are detected in the
cosmic microwave background (CMB). In the standard model of cosmology, these
are interpreted as the three neutrino species. However, at the time of
CMB-decoupling, neutrinos are not only relativistic but they are also
freestreaming. Here, we investigate, whether the CMB is sensitive to this
defining feature of neutrinos, or whether the CMB-data allow to replace
neutrinos with a relativistic fluid. We show that free streaming particles are
preferred over a relativistic perfect fluid with $\Delta\chi^2\simeq 21$. We
also study the possibility to replace the neutrinos by a viscous fluid and find
that a relativistic viscous fluid with either the standard values $c_{\rm
eff}^2=c_{\rm vis}^2=1/3$ or best fit values for $c_{\rm eff}^2$ and $c_{\rm
vis}^2$ has $\Delta\chi^2=20$ and thus cannot provide a good fit to present CMB
data either. | New EoR Power Spectrum Limits From MWA Phase II Using the Delay Spectrum
Method and Novel Systematic Rejection: We present an analysis of Epoch of Reionization data from Phase II of the
Murchison Widefield Array using the \texttt{simpleDS} delay spectrum pipeline.
Prior work analyzed the same observations using the FHD/$\varepsilon$ppsilon
imaging pipeline, and so the present analysis represents the first time that
both principal types of 21 cm cosmology power spectrum estimation approaches
have been applied to the same data set. Our limits on the 21 cm power spectrum
amplitude span a range in $k$ space of $|k| < 1~h_{100}{\rm Mpc}^{-1}$ with a
lowest measurement of $\Delta^2(k) \leq$ $4.58\times10^3$ mK$^2$ at $k = 0.190
h_{100}\rm{Mpc}^{-1}$ and $z = 7.14$. In order to achieve these limits, we need
to mitigate a previously unidentified common mode systematic in the data set.
If not accounted for, this systematic introduces an overall \emph{negative}
bias that can make foreground contaminated measurements appear as stringent,
noise-limited constraints on the 21 cm signal amplitude. The identification of
this systematic highlights the risk in modeling systematics as
positive-definite contributions to the power spectrum and in ``conservatively''
interpreting all measurements as upper limits. |
Density and velocity profiles around cosmic voids: We study the evolution of the cross-correlation between voids and the mass
density field - i.e. of void profiles. We show that approaches based on the
spherical model alone miss an important contribution to the evolution on large
scales of most interest to cosmology: they fail to capture the well-known fact
that the large-scale bias factor of conserved tracers evolves. We also show
that the operations of evolution and averaging do not commute, but this
difference is only significant within about two effective radii. We show how to
include a term which accounts for the evolution of bias, which is directly
related to the fact that voids move. The void motions are approximately
independent of void size, so they are more significant for smaller voids that
are typically more numerous. This term also contributes to void-matter pairwise
velocities: including it is necessary for modeling the typical outflow speeds
around voids. It is, therefore, important for void redshift space distortions.
Finally, we show that the excursion set peaks/troughs approach provides a
useful, but not perfect framework for describing void profiles and their
evolution. | Scalar-Induced Gravitational Waves in a $Λ$CDM Cosmology: We reconsider the gravitational wave spectrum induced by scalar perturbations
in spatially flat Friedmann-Lema\^itre-Robertson-Walker spacetimes, focusing on
the matter- and $\Lambda$-dominated epochs. During matter domination,
sub-horizon modes are not free and a commonly applied approximation for the
derivative of the tensor perturbation is flawed. We show analytically that this
leads to a significant overestimation of the energy density spectrum. In
addition, we demonstrate that gauge-dependent non-oscillating tensor
perturbations appear in the presence of a cosmological constant. Complementing
the analytical calculations, we compute the according present-day spectrum
numerically for a Planck-like $\Lambda$CDM cosmology, finding that
non-oscillating growing modes appear during the transition between matter and
$\Lambda$ domination in conformal Newtonian gauge. |
Kriging Interpolating Cosmic Velocity Field: [abridged] Volume-weighted statistics of large scale peculiar velocity is
preferred by peculiar velocity cosmology, since it is free of uncertainties of
galaxy density bias entangled in mass-weighted statistics. However, measuring
the volume-weighted velocity statistics from galaxy (halo/simulation particle)
velocity data is challenging. For the first time, we apply the Kriging
interpolation to obtain the volume-weighted velocity field. Kriging is a
minimum variance estimator. It predicts the most likely velocity for each place
based on the velocity at other places. We test the performance of Kriging
quantified by the E-mode velocity power spectrum from simulations. Dependences
on the variogram prior used in Kriging, the number $n_k$ of the nearby
particles to interpolate and the density $n_P$ of the observed sample are
investigated. First, we find that Kriging induces $1\%$ and $3\%$ systematics
at $k\sim 0.1h{\rm Mpc}^{-1}$ when $n_P\sim 6\times 10^{-2} ({\rm Mpc}/h)^{-3}$
and $n_P\sim 6\times 10^{-3} ({\rm Mpc}/h)^{-3}$, respectively. The deviation
increases for decreasing $n_P$ and increasing $k$. When $n_P\lesssim 6\times
10^{-4} ({\rm Mpc}/h)^{-3}$, a smoothing effect dominates small scales, causing
significant underestimation of the velocity power spectrum. Second, increasing
$n_k$ helps to recover small scale power. However, for $n_P\lesssim 6\times
10^{-4} ({\rm Mpc}/h)^{-3}$ cases, the recovery is limited. Finally, Kriging is
more sensitive to the variogram prior for lower sample density. The most
straightforward application of Kriging on the cosmic velocity field does not
show obvious advantages over the nearest-particle method (Zheng et al. 2013)
and could not be directly applied to cosmology so far. However, whether
potential improvements may be achieved by more delicate versions of Kriging is
worth further investigation. | A persistent excess of galaxy-galaxy strong lensing observed in galaxy
clusters: Previous studies have revealed that the estimated probability of
galaxy-galaxy strong lensing in observed galaxy clusters exceeds the
expectations from the $\Lambda$ Cold Dark Matter cosmological model by one
order of magnitude. We aim to understand the origin of this excess by analyzing
a larger set of simulated galaxy clusters and investigating how the theoretical
expectations vary under different adopted prescriptions and numerical
implementations of star formation and feedback in simulations. We perform a
ray-tracing analysis of 324 galaxy clusters from the Three Hundred project,
comparing the Gadget-X and Gizmo-Simba runs. These simulations, which start
from the same initial conditions, are performed with different implementations
of hydrodynamics and galaxy formation models tailored to match different
observational properties of the Intra-Cluster-Medium and cluster galaxies. We
find that galaxies in the Gizmo-Simba simulations develop denser stellar cores
than their Gadget-X counterparts. Consequently, their probability for
galaxy-galaxy strong lensing is higher by a factor of $\sim 3$. This increment
is still insufficient to fill the gap with observations, as a discrepancy by a
factor $\sim 4$ still persists. In addition, we find that several simulated
galaxies have Einstein radii that are too large compared to observations. We
conclude that a persistent excess of galaxy-galaxy strong lensing exists in
observed galaxy clusters. The origin of this discrepancy with theoretical
predictions is still unexplained in the framework of the cosmological
hydrodynamical simulations. This might signal a hitherto unknown issue with
either the simulation methods or our assumptions regarding the standard
cosmological model. |
Comments on environmental effects in the origin of angular momenta in
galaxies: We examine the orientations of galaxies in 43 rich Abell galaxy clusters
belonging to superclusters and containing at least 100 members in the
considered area as a function of supercluster multiplicity. It is found that
the orientation of galaxies in the analyzed clusters is not random and the
alignment decreases with supercluster richness, although the effect is
statistically significant only for azimuthal angles. The dependence of galaxy
alignment on cluster location inside or outside a supercluster and on
supercluster multiplicity clearly shows the importance of environmental effects
on the origin of galaxy angular momenta. The comparison with alignment of
galaxies in a sample of rich Abell clusters not belonging to superclusters is
made too. | The effects of dust on the photometric parameters of decomposed disks
and bulges: We present results of a study to quantify the effects of dust on the derived
photometric parameters of disk and bulges obtained from bulge-disk
decomposition: scale-length, effective radius, Sersic index, disk axis-ratio,
and bulge-to-disk ratio. The dust induced changes in these parameters were
obtained by fitting simulated images of composite systems (containing a disk
and a bulge) produced using radiative transfer calculations. The simulations
were fitted with the GALFIT 3.0.2 data analysis algorithm. Fits were done with
both a combination of an exponential plus a variable-index Sersic function as
well as with a combination of two variable-index Sersic functions. We find that
dust is biasing the derived exponential scale-length of decomposed disks
towards smaller values than would be otherwise derived if the galaxy were to
have no bulge. Similarly, the derived bulge-to-disk ratio is biased towards
smaller values. However, the derived axis-ratio of the disk is not changed in
the decomposition process. The derived effective radius of decomposed disks of
systems having exponential bulges is found to be less affected by dust when
fits are done with two variable-index Sersic functions. For the same type of
fits dust is found to bias the value of the derived effective radius of
decomposed disks towards lower values for systems having de Vaucouleurs bulges.
All corrections derived in this paper are made available in electronic form. |
Simulating galaxy evolution with a non-universal stellar initial mass
function: We consider that the stellar initial mass function (IMF) depends on physical
properties of star-forming molecular clouds in galaxies and thereby investigate
how such a non-universal IMF (NUIMF) influences galaxy evolution. We
incorporate a NUIMF model into galaxy-scale chemodynamical simulations in order
to investigate the differences in chemical and dynamical evolution of disk
galaxies between the NUIMF and universal IMF (UIMF) models. In the adopted
NUIMF model, the three slopes of the Kroupa IMF depend independently on
densities and metallicities ([Fe/H]) of molecular gas clouds, and production
rates of metals and dust from massive and AGB stars can vary according to the
time evolution of the three IMF slopes. The preliminary results of the
simulations are as follows. Star formation rates in actively star-forming disk
galaxies can be significantly lower in the NUIMF model than in the UIMF model,
and the differences between the two models can be more remarkable in galaxies
with higher SFRs. Chemical enrichment can proceed more rapidly in the NUIMF
model and [Mg/Fe] for a given metallicity is higher in the NUIMF model. The
evolution of H2 fraction (f_H2) and dust-to-gas ratio (D) is more rapid in the
NUIMF model so that the final f_H2 and $D$ can be higher in the NUIMF model.
Formation of massive stellar clumps in gas-rich disks is more strongly
suppressed owing to the stronger SN feedback effect in the NUIMF model. The
radial density profiles of new stars within the central 1kpc are shallower in
the NUIMF model. | The SDSS Coadd: Cross-Correlation Weak Lensing and Tomography of Galaxy
Clusters: The shapes of distant galaxies are sheared by intervening galaxy clusters. We
examine this effect in Stripe 82, a 275 square degree region observed multiple
times in the Sloan Digital Sky Survey and coadded to achieve greater depth. We
obtain a mass-richness calibration that is similar to other SDSS analyses,
demonstrating that the coaddition process did not adversely affect the lensing
signal. We also propose a new parameterization of the effect of tomography on
the cluster lensing signal which does not require binning in redshift, and we
show that using this parameterization we can detect tomography for stacked
clusters at varying redshifts. Finally, due to the sensitivity of the
tomographic detection to accurately marginalizing over the effect of the
cluster mass, we show that tomography at low redshift (where dependence on
exact cosmological models is weak) can be used to constrain mass profiles in
clusters. |
Cosmological Constraints on the Higgs Boson Mass: For a robust interpretation of upcoming observations from PLANCK and LHC
experiments it is imperative to understand how the inflationary dynamics of a
non-minimally coupled Higgs scalar field with gravity may affect the
determination of the inflationary observables. We make a full proper analysis
of the WMAP7+SN+BAO dataset in the context of the non-minimally coupled Higgs
inflation field with gravity. For the central value of the top quark pole mass
m_T=171.3 GeV, the fit of the inflation model with non-minimally coupled Higgs
scalar field leads to the Higgs boson mass between 143.7 and 167 GeV (95% CL).
We show that the inflation driven by a non-minimally coupled scalar field to
the Einstein gravity leads to significant constraints on the scalar spectral
index and tensor-to-scalar ratio when compared with the similar constraints
tensor to from the standard inflation with minimally coupled scalar field. We
also show that an accurate reconstruction of the Higgs potential in terms of
inflationary observables requires an improved accuracy of other parameters of
the Standard Model of particle physics as the top quark mass and the effective
QCD coupling constant. | Primordial Non-Gaussianities from Inflation Models: This is a pedagogical review on primordial non-Gaussianities from inflation
models. We introduce formalisms and techniques that are used to compute such
quantities. We review different mechanisms which can generate observable large
non-Gaussianities during inflation, and distinctive signatures they leave on
the non-Gaussian profiles. They are potentially powerful probes to the dynamics
of inflation. We also provide a non-technical and qualitative summary of the
main results and underlying physics. |
A Uniform Spherical Goat (Problem): Explicit Solution for Homologous
Collapse's Radial Evolution in Time: The homologous collapse from rest of a uniform density sphere under its self
gravity is a well-known toy model for the formation dynamics of astronomical
objects ranging from stars to galaxies. Equally well-known is that the
evolution of the radius with time cannot be explicitly obtained because of the
transcendental nature of the differential equation solution. Rather, both
radius and time are written parametrically in terms of the development angle
$\theta$. We here present an explicit integral solution for radius as a
function of time, exploiting methods from complex analysis recently applied to
the mathematically-similar 'geometric goat problem'. Our solution can be
efficiently evaluated using a Fast Fourier Transform and allows for arbitrary
sampling in time, with a simple Python implementation that is $\sim$$100\times$
faster than using numerical root-finding to achieve arbitrary sampling. Our
explicit solution is advantageous relative to the usual approach of first
generating a uniform grid in $\theta$, since this latter results in a
non-uniform radial or time sampling, less useful for applications such as
generation of sub-grid physics models. | A New Estimator for Phase Statistics: We introduce a novel statistic to probe the statistics of phases of Fourier
modes in two-dimensions (2D) for weak lensing convergence field $\kappa$. This
statistic contains completely independent information compared to that
contained in observed power spectrum. We compare our results against
state-of-the-art numerical simulations as a function of source redshift and
find good agreement with theoretical predictions. We show that our estimator
can achieve better signal-to-noise compared to the commonly employed statistics
known as the line correlation function (LCF). Being a two-point statistics, our
estimator is also easy to implement in the presence of complicated noise and
mask, and can also be generalised to higher-order. While applying this
estimator for the study of lensed CMB maps, we show that it is important to
include post-Born corrections in the study of statistics of phase. |
The stripping of a galaxy group diving into the massive cluster A2142: Structure formation in the current Universe operates through the accretion of
group-scale systems onto massive clusters. The detection and study of such
accreting systems is crucial to understand the build-up of the most massive
virialized structures we see today. We report the discovery with XMM-Newton of
an irregular X-ray substructure in the outskirts of the massive galaxy cluster
Abell 2142. The tip of the X-ray emission coincides with a concentration of
galaxies. The bulk of the X-ray emission of this substructure appears to be
lagging behind the galaxies and extends over a projected scale of at least 800
kpc. The temperature of the gas in this region is 1.4 keV, which is a factor of
~4 lower than the surrounding medium and is typical of the virialized plasma of
a galaxy group with a mass of a few 10^13M_sun. For this reason, we interpret
this structure as a galaxy group in the process of being accreted onto the main
dark-matter halo. The X-ray structure trailing behind the group is due to gas
stripped from its original dark-matter halo as it moves through the
intracluster medium (ICM). This is the longest X-ray trail reported to date.
For an infall velocity of ~1,200 km s-1 we estimate that the stripped gas has
been surviving in the presence of the hot ICM for at least 600 Myr, which
exceeds the Spitzer conduction timescale in the medium by a factor of >~400.
Such a strong suppression of conductivity is likely related to a tangled
magnetic field with small coherence length and to plasma microinstabilities.
The long survival time of the low-entropy intragroup medium suggests that the
infalling material can eventually settle within the core of the main cluster. | Nearby Galaxies in the 2micron All Sky Survey I. K-band Luminosity
Functions: Differential K-band luminosity functions (LFs) are presented for a complete
sample of 1613 nearby bright galaxies segregated by visible morphology. The LF
for late-type spirals follows a power law that rises towards low luminosities
whereas the LFs for ellipticals, lenticulars and bulge-dominated spirals are
peaked and decline toward both higher and lower luminosities. Each
morphological type (E, S0, S0/a-Sab, Sb-Sbc, Sc-Scd) contributes approximately
equally to the overall K-band luminosity density of galaxies in the local
universe. Type averaged bulge/disk ratios are used to subtract the disk
component leading to the prediction that the K-band LF for bulges is bimodal
with ellipticals dominating the high luminosity peak, comprising 60% of the
bulge luminosity density in the local universe with the remaining 40%
contributed by lenticulars and the bulges of spirals. Overall, bulges
contribute 30% of the galaxy luminosity density at K in the local universe with
spiral disks making up the remainder. If bulge luminosities indicate central
black hole masses, then our results predict that the black hole mass function
is also bimodal. |
Euclid preparation: II. The EuclidEmulator -- A tool to compute the
cosmology dependence of the nonlinear matter power spectrum: We present a new power spectrum emulator named EuclidEmulator that estimates
the nonlinear correction to the linear dark matter power spectrum. It is based
on a spectral decomposition method called polynomial chaos expansion. All steps
in the construction of the emulator have been tested and optimized: the large
high-resolution N-body simulations carried out with PKDGRAV3 were validated
using a simulation from the Euclid Flagship campaign and demonstrated to have
converged up to wavenumbers $k\approx 5\,h\,{\rm Mpc}^{-1}$ for redshifts
$z\leq 5$. The emulator is constructed using the uncertainty quantification
software UQLab and it has been optimized first by creating mock emulators based
on Takahashi's HALOFIT. We show that it is possible to successfully predict the
performance of the final emulator in this way prior to performing any N-body
simulations. We provide a C-code to calculate the nonlinear correction at a
relative accuracy of $\sim0.3\%$ with respect to N-body simulations within 50
ms. The absolute accuracy of the final nonlinear power spectrum is comparable
to one obtained with N-body simulations, i.e. $\sim 1\%$ for $k\lesssim
1\,h\,{\rm Mpc}^{-1}$ and $z\lesssim 3.5$. This enables efficient forward
modeling in the nonlinear regime allowing for maximum likelihood estimation of
cosmological parameters. EuclidEmulator has been compared to HALOFIT and
CosmicEmu, an alternative emulator based on the Mira-Titan Universe, and shown
to be more accurate than these other approaches. This work paves a new way for
optimal construction of future emulators that also consider other cosmological
observables, use higher resolution input simulations and investigate higher
dimensional cosmological parameter spaces. | UV Background Fluctuations and Three-Point Correlations in the Large
Scale Clustering of the Lyman-alpha Forest: Using the Ly$\alpha$ mass assignment scheme (LyMAS), we make theoretical
predictions for the 3-dimensional 3-point correlation function (3PCF) of the
Ly$\alpha$ forest at redshift $z=2.3$. We bootstrap results from the (100
$h^{-1} \mbox{ Mpc}$)$^3$ Horizon hydrodynamic simulation to a (1 $h^{-1}$
Gpc)$^3$ $N$-body simulation, considering both a uniform UV background (UVB)
and a fluctuating UVB sourced by quasars with a comoving $n_q \approx 10^{-5}$
$h^3$ Mpc$^{-3}$ placed either in massive halos or randomly. On scales of
$10-30$ $h^{-1} \mbox{ Mpc}$, the flux 3PCF displays hierarchical scaling with
the square of the 2PCF, but with an unusual value of $Q \equiv
\zeta_{123}/(\xi_{12} \xi_{13} + \xi_{12} \xi_{23} + \xi_{13} \xi_{23}) \approx
-4.5$ that reflects the low bias of the Ly$\alpha$ forest and the
anti-correlation between mass density and transmitted flux. For halo-based
quasars and an ionizing photon mean free path of $\lambda = 300$ $h^{-1} \mbox{
Mpc}$ comoving, UVB fluctuations moderately depress the 2PCF and 3PCF, with
cancelling effects on $Q$. For $\lambda = 100$ $h^{-1} \mbox{ Mpc}$ or 50
$h^{-1} \mbox{ Mpc}$, UVB fluctuations substantially boost the 2PCF and 3PCF on
large scales, shifting the hierarchical ratio to $Q \approx -3$. We scale our
simulation results to derive rough estimate of the 3PCF detectability in
observational data sets for the redshift range $z=2.1 - 2.6$. At $r = 10$
$h^{-1} \mbox{ Mpc}$ and 20 $h^{-1} \mbox{ Mpc}$, we predict a signal-to-noise
(SNR) of $\sim$ 9 and $\sim$ 7, respectively, for both BOSS and eBOSS, and
$\sim$ 37 and $\sim$ 25 for DESI. At $r = 40$ $h^{-1} \mbox{ Mpc}$ the
predicted SNR is lower by $\sim$ 3$-$5 times. Measuring the flux 3PCF would be
a novel test of the conventional paradigm of the Ly$\alpha$ forest and help
separate the contributions of UVB fluctuations and density fluctuations to
Ly$\alpha$ forest clustering. |
Non-linear structure formation in the "Running FLRW" cosmological model: We present a suite of cosmological N-body simulations describing the "Running
Friedmann-Lema{\"i}tre-Robertson-Walker" (R-FLRW) cosmological model. This
model is based on quantum field theory in a curved space-time and extends
{\Lambda}CDM with a time-evolving vacuum density, {\Lambda}(z), and
time-evolving gravitational Newton's coupling, G(z). In this paper we review
the model and introduce the necessary analytical treatment needed to adapt a
reference N-body code. Our resulting simulations represent the first
realisation of the full growth history of structure in the R-FLRW cosmology
into the non-linear regime, and our normalisation choice makes them fully
consistent with the latest cosmic microwave background data. The
post-processing data products also allow, for the first time, an analysis of
the properties of the halo and sub-halo populations. We explore the
degeneracies of many statistical observables and discuss the steps needed to
break them. Furthermore, we provide a quantitative description of the
deviations of R-FLRW from {\Lambda}CDM, which could be readily exploited by
future cosmological observations to test and further constrain the model. | Optimal filters for the moving lens effect: We assess the prospects for detecting the moving lens effect using
cosmological surveys. The bulk motion of cosmological structure induces a
small-scale dipolar temperature anisotropy of the cosmic microwave radiation
(CMB), centered around halos and oriented along the transverse velocity field.
We introduce a set of optimal filters for this signal, and forecast that a high
significance detection can be made with upcoming experiments. We discuss the
prospects for reconstructing the bulk transverse velocity field on large scales
using matched filters, finding good agreement with previous work using
quadratic estimators. |
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