anchor
stringlengths 50
3.92k
| positive
stringlengths 55
6.16k
|
|---|---|
The Last Journey. II. SMACC -- Subhalo Mass-loss Analysis using Core
Catalogs: This paper introduces SMACC -- Subhalo Mass-loss Analysis using Core
Catalogs. SMACC adds a mass model to substructure merger trees based on halo
"core tracking." Our approach avoids the need for running expensive subhalo
finding algorithms and instead uses subhalo mass-loss modeling to assign masses
to halo cores. We present details of the SMACC methodology and demonstrate its
excellent performance in describing halo substructure and its evolution.
Validation of the approach is carried out using cosmological simulations at
significantly different resolutions. We apply SMACC to the 1.24
trillion-particle Last Journey simulation and construct core catalogs with the
additional mass information. These catalogs can be readily used as input to
semi-analytic models or subhalo abundance matching approaches to determine
approximate galaxy distributions, as well as for in-depth studies of
small-scale structure evolution. | The Stellar Mass Growth of Brightest Cluster Galaxies in the IRAC
Shallow Cluster Survey: The details of the stellar mass assembly of brightest cluster galaxies (BCGs)
remain an unresolved problem in galaxy formation. We have developed a novel
approach that allows us to construct a sample of clusters that form an
evolutionary sequence, and have applied it to the Spitzer IRAC Shallow Cluster
Survey (ISCS) to examine the evolution of BCGs in progenitors of present-day
clusters with mass of (2.5-4.5)x10^{14}Msun. We follow the cluster mass growth
history extracted from a high resolution cosmological simulation, and then use
an empirical method that infers the cluster mass based on the ranking of
cluster luminosity to select high-z clusters of appropriate mass from ISCS to
be progenitors of the given set of z=0 clusters. We find that, between z=1.5
and 0.5, the BCGs have grown in stellar mass by a factor of 2.3, which is
well-matched by the predictions from a state-of-the-art semi-analytic model.
Below z=0.5 we see hints of differences in behavior between the model and
observation. |
Using Faraday Rotation to Probe MHD Instabilities in Intracluster Media: It has recently been suggested that conduction-driven magnetohydrodynamic
(MHD) instabilities may operate at all radii within an intracluster medium
(ICM), and profoundly affect the structure of a cluster's magnetic field. Where
MHD instabilities dominate the dynamics of an ICM, they will re-orient magnetic
field lines perpendicular to the temperature gradient inside a cooling core, or
parallel to the temperature gradient outside it. This characteristic structure
of magnetic field could be probed by measurements of polarized radio emission
from background sources. Motivated by this possibility we have constructed 3-d
models of a magnetized cooling core cluster and calculated Faraday rotation
measure (RM) maps in the plane of the sky under realistic observing conditions.
We compare a scenario in which magnetic field geometry is characterized by
conduction driven MHD instabilities to that where it is determined by isotropic
turbulent motions. We find that future high-sensitivity spectro-polarimetric
measurements of RM, such as will be enabled by the Expanded Very Large Array
and Square Kilometer Array can distinguish between these two cases with
plausible exposure times. Such observations will test the existence of
conduction-driven MHD instabilities in dynamically relaxed cooling core
clusters. More generally, our findings imply that observations of Faraday RM
should be able to discern physical mechanisms that result in qualitatively
different magnetic field topologies, without a priori knowledge about the
nature of the processes. | Evidence for Intermediate BLR of Reverberation-Mapped AGN PG 0052+251: In this manuscript, we study properties of BLR of well-known
reverberation-mapped AGN, in order to find reliable evidence for intermediate
BLR. We firstly check properties of mapped AGN collected from literature in
plane of $\sHb^2/\sHa^2$ vs $\RHa/\RHb$. Commonly, virial BH masses based on
observed broad H$\alpha$ and H$\beta$ should be coincident. However, among the
mapped objects, PG0052 and NGC4253 are two apparent outliers in the plane of
$\sHb^2/\sHa^2$ vs $\RHa/\RHb$, which indicate BLRs of PG0052 and NGC4253 have
some special characters. Then based on the 55 public spectra of PG0052, BLR of
PG0052 is been carefully studied in detail. We find that line width ratio of
total observed broad H$\alpha$ to total observed broad H$\beta$ is $\sim$0.7,
which is much smaller than theoretical/observational value of $\sim$0.9.
Furthermore, flux ratio of total broad H$\alpha$ to total broad H$\beta$ is
about 6.8 (Balmer Decrement), which is not one reasonable value for BLUE quasar
PG 0052+251. Moreover, properties of line cores based on PCA technique confirm
there is one inner broad component and one seriously obscured intermediate
broad component in BLR of PG0052. If the seriously obscured intermediate BLR
was accepted, properties of PG0052 in the plane of $\sHb^2/\sHa^2$ vs
$\RHa/\RHb$ could be well reproduced, which indicates that the intermediate BLR
actually is well appropriate to mapped quasar PG 0052+251. Finally, the large
distance between inner component of BLR and intermediate component of BLR based
on CCF results rejects the possibility that the intermediate component is
probably extended part of inner component of BLR. |
The Importance of Slow-roll Corrections During Multi-field Inflation: We re-examine the importance of slow-roll corrections during the evolution of
cosmological perturbations in models of multi-field inflation. We find that in
many instances the presence of light degrees of freedom leads to situations in
which next to leading order slow-roll corrections become significant. Examples
where we expect such corrections to be crucial include models in which modes
exit the Hubble radius while the inflationary trajectory undergoes an abrupt
turn in field space, or during a phase transition. We illustrate this with two
examples -- hybrid inflation and double quadratic inflation. Utilizing both
analytic estimates and full numerical results, we find that corrections can be
as large as 20%. Our results have implications for many existing models in the
literature, as these corrections must be included to obtain accurate
observational predictions -- particularly given the level of accuracy expected
from CMB experiments such as Planck | Extended Chameleons: We extend the chameleon models by considering Scalar-Fluid theories where the
coupling between matter and the scalar field can be represented by a quadratic
effective potential with density-dependent minimum and mass. In this context,
we study the effects of the scalar field on Solar System tests of gravity and
show that models passing these stringent constraints can still induce large
modifications of Newton's law on galactic scales. On these scales we analyse
models which could lead to a percent deviation of Newton's law outside the
virial radius. We then model the dark matter halo as a Navarro-Frenk-White
profile and explicitly find that the fifth force can give large contributions
around the galactic core in a particular model where the scalar field mass is
constant and the minimum of its potential varies linearly with the matter
density. At cosmological distances, we find that this model does not alter the
growth of large scale structures and therefore would be best tested on galactic
scales, where interesting signatures might arise in the galaxy rotation curves. |
Observational constraints of the gravitational waves in the Brans-Dicke
theory: Einstein frame and Jordan-Brans-Dicke frame: We investigate the quantum origin of the primordial cosmological
gravitational waves in the Brans-Dicke theory in the two conformally related
frames, the Jordan-Brans-Dicke frame and the Einstein frame. We calculated the
theoretical observable in both frames and we compared both with General
Relativity. We compute the number of gravitons $N_k$ produced during inflation
and the observables: power spectrum $P_T$, spectral index $n_T$ and energy
density $\Omega_k$. The comparison shows that for the case of the particles
number $N_k$ the results are the same in both frames and in General Relativity
when the Brans-Dicke parameter is much bigger than unity. For the spectral
index $n_T$ we show that it is possible to get a scale invariant perturbation
in the Jordan-Brans-Dicke frame when $\omega\rightarrow\infty$ and in the
Einstein frame when $\omega\rightarrow\pm\infty$. In both frames, the results
found for the power spectrum $P_T$ and the energy density $\Omega$ show that
the prefered values of $\omega$ are diferente from that that are found in the
local tests. | Propagation of Ultra High Energy Cosmic Rays in Extragalactic Magnetic
Fields: A view from cosmological simulations: We use the CRPropa code to simulate the propagation of ultra high energy
cosmic rays (with energy $\geq 10^{18} \rm eV$ and pure proton composition)
through extragalactic magnetic fields that have been simulated with the
cosmological ENZO code.We test both primordial and astrophysical magnetogenesis
scenarios in order to investigate the impact of different magnetic field
strengths in clusters, filaments and voids on the deflection of cosmic rays
propagating across cosmological distances. We also study the effect of
different source distributions of cosmic rays around simulated Milky-Way like
observers. Our analysis shows that the arrival spectra and anisotropy of events
are rather insensitive to the distribution of extragalactic magnetic fields,
while they are more affected by the clustering of sources within a $\sim 50$
Mpc distance to observers. Finally, we find that in order to reproduce the
observed degree of isotropy of cosmic rays at $\sim $ EeV energies, the average
magnetic fields in cosmic voids must be $\sim 0.1 \rm \ nG$, providing limits
on the strength of primordial seed fields. |
Gaia: a Window to Large Scale Flows: Using redshifts as a proxy for galaxy distances, estimates of the 2D
transverse peculiar velocities of distant galaxies could be obtained from
future measurements of proper motions. We provide the mathematical framework
for analyzing 2D transverse motions and show that they offer several advantages
over traditional probes of large scale motions. They are completely independent
of any intrinsic relations between galaxy properties, hence they are
essentially free of selection biases. They are free from homogeneous and
inhomogeneous Malmquist biases that typically plague distance indicator
catalogs. They provide additional information to traditional probes which yield
line-of-sight peculiar velocities only. Further, because of their 2D nature,
fundamental questions regarding vorticity of large scale flows can be
addressed. Gaia for example is expected to provide proper motions of at least
bright galaxies with high central surface brightness, making proper motions a
likely contender traditional probes based on current and future distance
indicator measurements. | The influence of the effective number of active and sterile neutrinos on
the determination of the values of cosmological parameters: In the presented work we consider the influence of a hypothetical sterile
neutrino (with eV-scale mass) on the determination of cosmological parameters.
If it is detected, it will be necessary to include it into the $\Lambda \rm
CDM$ model with the fixed values of its mass $m_{\rm s}$ and mixing angle
$\theta_{s}$, which is the main method used through this paper. Apart from
that, the seesaw mechanism requires there to be at least two sterile states,
one of them being much heavier than the active ones. The heavier sterile state
($m_{s}\sim1$ keV) would decay and increase the effective number of active
neutrinos. Therefore, the influence of a change in the effective number of
relativistic neutrino species $N_{\rm eff}$ was studied as well, which could be
caused by, for example, the decay processes of the above-mentioned sterile
neutrinos, as well as processes leading to an increase in the temperature of
relic neutrinos $T_{\rm C\nu B}$. The effects studied in this work lead to a
significant change in the estimates of the cosmological parameters, including
the value of $H_{0}$. It has been discovered that the accounting of the sterile
neutrino with masses $m=1$ and $2.7$ eV leads to a decrease in the estimate of
the current Hubble parameter value $H_{0}$ and, therefore, exacerbates the
``$H_{0}$-tension'' problem. An increase in the value of the effective number
of relativistic neutrino species leads, on the contrary, to an increase in the
$H_{0}$ estimate, resolving the above-mentioned problem at $N_{\rm
eff}=3.0+0.9$, which is equivalent to an increase of the neutrino temperature
up to $T ^{\,0}_{\rm C\nu B}=1.95+0.14\,\rm K$. At the same time, the rest of
the cosmological parameters do not change significantly, leaving us within the
framework of the standard $\Lambda \rm CDM$ model. |
Inference from the 21cm signal: Once we have a measurement, how do we extract this information from the
signal? This chapter focusses on the inference of the interesting astrophysics
and cosmology once we obtain a detection of the 21-cm signal.
Essentially, inference of the astrophysics can be broken down into three
parts:
1. Characterisation of the observed data: The observed 21-cm signal varies
spatially as well as along the line-of-sight (frequency or redshift dimension)
to provide a full three dimensional movie of the intergalactic medium in the
early Universe. However, we cannot perform a full pixel-by-pixel comparison
between theoretical models and the observed signal. Instead, we require a
variety of statistical methods to average the observational data in order to be
able to better characterise and compare the behaviour of the faint signal.
2. An efficient method to model the 21-cm signal: In order to interpret the
observations and understand the astrophysical processes responsible, we must be
able to produce physically motivated models capable of replicating the signal.
Further, these must be as computationally efficient as possible in order to be
able to realistically investigate the 21-cm signal.
3. A robust probabilistic framework to extract the physics: The observed
21-cm signal is dependent on numerous physical processes, which within our
models or simulations are described by many unknown parameters. Further, these
contain approximations in order to deal with the requisite dynamic range. We
must be able to characterise our ignorance in a meaningful way in order to be
truly able to infer the astrophysical processes of the epoch of reionisation
and cosmic dawn.
In this chapter we will focus on each separately, discussing the current
state-of-the-art in inferring astrophysical and cosmological information from
the 21cm signal. | Constraints on dark energy from the CSST galaxy clusters: We study the potential of the galaxy cluster sample expected from the China
Space Station Telescope (CSST) survey to constrain dark energy properties. By
modelling the distribution of observed cluster mass for a given true mass to be
log-normal and adopting a selection threshold in the observed mass $M_{200m}
\geq 0.836 \times 10^{14} h^{-1}M_{\odot}$, we find about $4.1 \times 10^{5}$
clusters in the redshift range $0 \leq z \leq 1.5$ can be detected by the CSST.
We construct the Fisher matrix for the cluster number counts from CSST, and
forecast constraints on dark energy parameters for models with constant
($w_0$CDM) and time dependent ($w_0w_a$CDM) equation of state. In the
self-calibration scheme, the dark energy equation of state parameter $w_0$ of
$w_0$CDM model can be constrained to $\Delta w_0 = 0.036$. If $w_a$ is added as
a free parameter, we obtain $\Delta w_0 = 0.077$ and $\Delta w_a = 0.39$ for
the $w_0w_a$CDM model, with a Figure of Merit for ($w_0,w_a$) to be 68.99.
Should we had perfect knowledge of the observable-mass scaling relation
(``known SR" scheme), we would obtain $\Delta w_0 = 0.012$ for $w_0$CDM model,
$\Delta w_0 = 0.062$ and $\Delta w_a = 0.24$ for $w_0w_a$CDM model. The dark
energy Figure of Merit of ($w_0,w_a$) increases to 343.25. By extending the
maximum redshift of the clusters from $z_{max} \sim 1.5$ to $z_{max} \sim 2$,
the dark energy Figure of Merit for ($w_0,w_a$) increases to 89.72
(self-calibration scheme) and 610.97 (``known SR" scheme), improved by a factor
of $\sim 1.30$ and $\sim 1.78$, respectively. We find that the impact of
clusters' redshift uncertainty on the dark energy constraints is negligible as
long as the redshift error of clusters is smaller than 0.01, achievable by
CSST. We also find that the bias in logarithm mass must be calibrated to be
$0.30$ or better to avoid significant dark energy parameter bias. |
The Mira Distance to M101 and a 4% Measurement of H0: The giant spiral galaxy M101 is host to the nearest recent Type Ia Supernova
(SN 2011fe) and thus has been extensively monitored in the near-infrared to
study the late-time lightcurve of the supernova. Leveraging this existing
baseline of observations, we derive the first Mira-based distance to M101 by
discovering and classifying a sample of 211 Miras with periods ranging from 240
to 400 days in the supernova field. Combined with new HST WFC3/IR channel
observations, our dataset totals 11 epochs of F110W (HST $YJ$) and 13 epochs of
F160W (HST $H$) data spanning $\sim$2900 days. We adopt absolute calibrations
of the Mira Period-Luminosity Relation based on geometric distances to the
Large Magellanic Cloud and the water megamaser host galaxy NGC 4258, and find
$\mu_{\rm M101} = $ 29.10 $\pm$ 0.06 mag. This distance is in 1$\sigma$
agreement with most other recent Cepheid and Tip of the Red Giant Branch
distance measurements to M101. Including the previous Mira-SNIa host, NGC 1559
and SN 2005df, we determine the fiducial SN Ia peak luminosity, $M^0_B = -19.27
\pm 0.09$ mag. With the Hubble diagram of SNe Ia, we derive $H_0 = 72.37 \pm
2.97 $ km s$^{-1}$Mpc$^{-1}$, a $4.1\%$ measurement of $H_0$ using Miras. We
find excellent agreement with recent Cepheid distance ladder measurements of
$H_0$ and confirm previous indications that the local universe value of $H_0$
is higher than the early-universe value at $\sim$ $95\%$ confidence. Currently,
the Mira-based $H_0$ measurement is still dominated by the statistical
uncertainty in the SN Ia peak magnitude. | Dark matter from gravitational particle production at reheating: We show that curvature induced particle production at reheating generates
adiabatic dark matter if there are non-minimally coupled spectator scalars
weakly coupled to visible matter. The observed dark matter abundance implies an
upper bound on spectator masses $m$ and non-minimal coupling values $\xi$. For
example, assuming quadratic inflation, instant reheating and a single spectator
scalar with only gravitational couplings, the observed dark matter abundance is
obtained for $m\sim 0.1$ GeV and $\xi \sim 1$. Larger mass and coupling values
of the spectator are excluded as they would lead to overproduction of dark
matter. |
Hunting for the host galaxy groups of binary black holes and the
application in constraining Hubble constant: The discovery of gravitational-wave (GW) signals, produced by the coalescence
of stellar-mass binary black holes (SBBHs), opens a new window to study the
astrophysical origins and dynamical evolutions of compact binaries. In
addition, these GW events can be treated as the standard sirens to constrain
various cosmological parameters. Both issues require the host identification
for these GW events, with help of the spatial resolution of GW detector
networks. In this paper, we investigate the capabilities of various detector
networks for identifying the SBBHs' host galaxy groups, rather than their host
galaxies, which can overcome the influence of galaxies' proper motions in dark
matter halos for measuring the cosmological parameters. In our analysis, the
group catalog of SDSS DR7 with redshift $z\in(0.01,0.1)$ is considered as an
example of the application. We find that for the second-generation (2G)
detector network, the host galaxy groups of around $(0.7-6.9)$ SBBHs can be
identified per year assuming all sources are $30-30\ M_{\odot}$ binaries, and
that all five detectors in the network are in lock 100\% of the time. For the
3G detector network, this number becomes $(3.9-40.0)$ yr$^{-1}$. We also
investigate the potential constraint on the Hubble constant $H_0$ by these GW
events, if their redshift information is extracted from the candidates of host
galaxy groups. We find that, by five-year's full time observations, 2G detector
network is expected to give a constraint of $\Delta H_0/H_0\sim (1\%,4\%)$,
which can be more than two order smaller if considering the 3G detector
network. | Bounds from ISW-galaxy cross-correlations on generalized covariant
Galileon models: Several modified cosmological models exist, which also try to address the
tensions between data and predictions of the $\Lambda$-CDM model. Galileon
models are particular scalar tensor theories that represent one such
possibilities. While it is commonly understood that there may be
inconsistencies between predictions of some Galileon models and observations,
in particular concerning ISW-galaxy cross-correlations, there is no proof yet
that these models are completely ruled out. Indeed, by using a specific
background in the generalized covariant Galileon theory known as the the
tracker solution, here we show that, after imposing all standard theoretical
stability constraints, it is still possible to identify a region in the
parameter space of the model that allows for positive ISW-galaxy
cross-correlations. By a physical interpretation in terms of a chi-square
analysis, we confirm the expectation that in this viable region the predictions
of generalized covariant Galileon theory on the tracker solution background
have higher likelihood when they approach the physics of the $\Lambda$-CDM
model. |
Selection Effects in the SDSS Quasar Sample: The Filter Gap Footprint: In the Sloan Digital Sky Survey (SDSS) quasars are targeted using colors and
anything that can cause the identifying characteristics of the colors to
disappear can create problems in the source selection process. Quasar spectra
contain strong emission lines that can seriously affect the colors in
photometric systems in which the transmission characteristics vary abruptly and
significantly with redshift. When a strong line crosses a gap between two
filter passbands the color effects induced by the line change abruptly, and
there is also a dimming in apparent brightness compared to those redshifts
where the strong line is inside a filter passband where the transmission is
high. The strong emission lines in quasars, combined with the varying
detectability introduced by the transmission pattern of the five filters, will
result in a filter-gap footprint being imprinted on the N(z) distribution, with
more quasars being missed when a strong line falls in a filter gap. It is shown
here that a periodicity of Delta(z)~0.6 is imprinted on the redshift-number
distribution by this selection effect. Because this effect cannot be rigorously
corrected for, astronomers need to be aware of it in any investigation that
uses the SDSS N(z) distribution. Its presence also means that the SDSS quasar
data cannot be used either to confirm or to rule out the Delta(z)~0.6 redshift
period reported previously in other, unrelated quasar data. | HerMES: A Deficit in the Surface Brightness of the Cosmic Infrared
Background Due to Galaxy Cluster Gravitational Lensing: We have observed four massive galaxy clusters with the SPIRE instrument on
the Herschel Space Observatory and measure a deficit of surface brightness
within their central region after subtracting sources. We simulate the effects
of instrumental sensitivity and resolution, the source population, and the
lensing effect of the clusters to estimate the shape and amplitude of the
deficit. The amplitude of the central deficit is a strong function of the
surface density and flux distribution of the background sources. We find that
for the current best fitting faint end number counts, and excellent lensing
models, the most likely amplitude of the central deficit is the full intensity
of the cosmic infrared background (CIB). Our measurement leads to a lower limit
to the integrated total intensity of the CIB of I(250 microns) >
0.69_(-0.03)^(+0.03) (stat.)_(-0.06)^(+0.11) (sys.) MJy/sr, with more CIB
possible from both low-redshift sources and from sources within the target
clusters. It should be possible to observe this effect in existing high angular
resolution data at other wavelengths where the CIB is bright, which would allow
tests of models of the faint source component of the CIB. |
Relics as probes of galaxy cluster mergers: Galaxy clusters grow by mergers with other clusters and galaxy groups. These
mergers create shocks within the intracluster medium (ICM). It is proposed that
within the shocks particles can be accelerated to extreme energies. In the
presence of a magnetic field these particles should then form large regions
emitting synchrotron radiation, creating so-called radio relics. An example of
a cluster with relics is CIZA J2242.8+5301. Here we present hydrodynamical
simulations of idealized binary cluster collisions with the aim of constraining
the merger scenario for this cluster. We conclude that by using the location,
size and width of double radio relics we can set constraints on the mass
ratios, impact parameters, timescales, and viewing geometries of binary cluster
merger events. | ARC: Adaptive Ray-tracing with CUDA, a New Ray Tracing Code for Parallel
GPUs: We present the methodology of a photon-conserving, spatially-adaptive,
ray-tracing radiative transfer algorithm, designed to run on multiple parallel
Graphic Processing Units (GPUs). Each GPU has thousands computing cores, making
them ideally suited to the task of tracing independent rays. This ray-tracing
implementation has speed competitive with approximate momentum methods, even
with thousands of ionization sources, without sacrificing accuracy and
resolution. Here, we validate our implementation with the selection of tests
presented in the "cosmological radiative transfer codes comparison project," to
demonstrate the correct behavior of the code. We also present a selection of
benchmarks to demonstrate the performance and computational scaling of the
code. As expected, our method scales linearly with the number of sources and
with the square of the dimension of the 3D computational grid. Our current
implementation is scalable to an arbitrary number of nodes possessing GPUs, but
is limited to a uniform resolution 3D grid. Cosmological simulations of
reionization with tens of thousands of radiation sources and intergalactic
volumes sampled with 1024$^3$ grid points take about 30 days on 64 GPUs to
reach complete reionization. |
Biased total mass of cool core galaxy clusters by Sunyaev-Zel'dovich
effect measurements: The Sunyaev Zel'dovich (SZ) effect from galaxy clusters is one of the most
powerful cosmological tools for investigating the large-scale Universe. The big
advantage of the SZ effect is its redshift independence, which is not the case
for visible and X-ray observations. It allows us to directly estimate the
cluster's total mass from the integrated comptonization parameter Y, even for
distant clusters. However, not having a full knowing intra-cluster medium (ICM)
physics can affect the results. By taking self-similar temperature and density
profiles of the ICM into account, we studied how different ICM morphologies can
affect the cluster total mass estimation. With the help of the high percentage
of cool core (CC) clusters, as observed so far, the present analysis focuses on
studying this class of objects. A sample of eight nearby (0.1 < z < 0.5) and
high-mass (M > 10^(14) M_sun) clusters observed by Chandra was considered. We
simulated SZ observations of these clusters through X-ray derived information
and analyzed the mock SZ data again with the simplistic assumption of an
isothermal beta-model profile for the ICM. The bias on the recovered cluster
total mass using different sets of assumptions is estimated to be 50% higher in
the case of hydrostatic equilibrium. Possible contributions to the total bias
due to the line-of-sight integration and the considered ICM template are taken
into account. The large biases on total mass recovery firmly support, if still
necessary, cluster modeling based on more sophisticated universal profiles as
derived by X-ray observations of local objects and hydrodynamical simulations. | Herschel-ATLAS: Rapid evolution of dust in galaxies in the last 5
billion years: We present the first direct and unbiased measurement of the evolution of the
dust mass function of galaxies over the past 5 billion years of cosmic history
using data from the Science Demonstration Phase of the Herschel-ATLAS. The
sample consists of galaxies selected at 250{\mu}m which have reliable
counterparts from SDSS at z < 0.5, and contains 1867 sources. Dust masses are
calculated using both a single temperature grey-body model for the spectral
energy distribution and also using a model with multiple temperature
components. The dust temperature for either model shows no trend with redshift.
Splitting the sample into bins of redshift reveals a strong evolution in the
dust properties of the most massive galaxies. At z = 0.4 - 0.5, massive
galaxies had dust masses about five times larger than in the local Universe. At
the same time, the dust-to-stellar mass ratio was about 3-4 times larger, and
the optical depth derived from fitting the UV-sub-mm data with an energy
balance model was also higher. This increase in the dust content of massive
galaxies at high redshift is difficult to explain using standard dust evolution
models and requires a rapid gas consumption timescale together with either a
more top-heavy IMF, efficient mantle growth, less dust destruction or
combinations of all three. This evolution in dust mass is likely to be
associated with a change in overall ISM mass, and points to an enhanced supply
of fuel for star formation at earlier cosmic epochs. |
Keck Spectroscopy of Gravitationally Lensed z=4 Galaxies: Improved
Constraints on the Escape Fraction of Ionizing Photons: The fraction of ionizing photons that escape from young star-forming galaxies
is one of the largest uncertainties in determining the role of galaxies in
cosmic reionization. Yet traditional techniques for measuring this fraction are
inapplicable at the redshifts of interest due to foreground screening by the
Lyman alpha forest. In an earlier study, we demonstrated a reduction in the
equivalent width of low-ionization absorption lines in composite spectra of
Lyman break galaxies at z=4 compared to similar measures at z=3. This might
imply a lower covering fraction of neutral gas and hence an increase with
redshift in the escape fraction of ionizing photons. However, our spectral
resolution was inadequate to differentiate between several alternative
explanations, including changes with redshift in the outflow kinematics. Here
we present higher quality spectra of 3 gravitationally lensed Lyman break
galaxies at z=4 with a spectral resolution sufficient to break this degeneracy
of interpretation. We present a method for deriving the covering fraction of
low-ionization gas as a function of outflow velocity and compare the results
with similar quality data taken for galaxies at lower redshift. We find a
significant trend of lower covering fractions of low-ionization gas for
galaxies with strong \Lya emission. In combination with the demographic trends
of \Lya emission with redshift from our earlier work, our results provide new
evidence for a reduction in the average H I covering fraction, and hence an
increase in the escape fraction of ionizing radiation from Lyman break
galaxies, with redshift. | Strong Conformity and Assembly Bias: Towards a Physical Understanding of
the Galaxy-Halo Connection in SDSS Clusters: Understanding the physical connection between cluster galaxies and massive
haloes is key to mitigating systematic uncertainties in next-generation cluster
cosmology. We develop a novel method to infer the level of conformity between
the stellar mass of the brightest central galaxies~(BCGs) $M_*^{BCG}$ and the
satellite richness $\lambda$, defined as their correlation coefficient
$\rho_{cc}$ at fixed halo mass, using the abundance and weak lensing of SDSS
clusters as functions of $M_*^{BCG}$ and $\lambda$. We detect a halo
mass-dependent conformity as
$\rho_{cc}{=}0.60{+}0.08\ln(M_h/3{\times}10^{14}M_{\odot}/h)$. The strong
conformity successfully resolves the "halo mass equality" conundrum discovered
in Zu et al. 2021 -- when split by $M_*^{BCG}$ at fixed $\lambda$, the low and
high-$M_*^{BCG}$ clusters have the same average halo mass despite having a
$0.34$ dex discrepancy in average $M_*^{BCG}$. On top of the best-fitting
conformity model, we develop a cluster assembly bias~(AB) prescription
calibrated against the CosmicGrowth simulation, and build a conformity+AB model
for the cluster weak lensing measurements. Our model predicts that with a
${\sim}20\%$ lower halo concentration $c$, the low-$M_*^{BCG}$ clusters are
${\sim}10\%$ more biased than the high-$M_*^{BCG}$ systems, in excellent
agreement with the observations. We also show that the observed conformity and
assembly bias are unlikely due to projection effects. Finally, we build a toy
model to argue that while the early-time BCG-halo co-evolution drives the
$M_*^{BCG}$-$c$ correlation, the late-time dry merger-induced BCG growth
naturally produces the $M_*^{BCG}$-$\lambda$ conformity despite the well-known
anti-correlation between $\lambda$ and $c$. Our method paves the path towards
simultaneously constraining cosmology and cluster formation with future cluster
surveys. |
Diagnosing multiplicative error by lensing magnification of type Ia
supernovae: Weak lensing causes spatially coherent fluctuations in flux of type Ia
supernovae (SNe Ia). This lensing magnification allows for weak lensing
measurement independent of cosmic shear. It is free of shape measurement errors
associated with cosmic shear and can therefore be used to diagnose and
calibrate multiplicative error. Although this lensing magnification is
difficult to measure accurately in auto correlation, its cross correlation with
cosmic shear and galaxy distribution in overlapping area can be measured to
significantly higher accuracy. Therefore these cross correlations can put
useful constraint on multiplicative error, and the obtained constraint is free
of cosmic variance in weak lensing field. We present two methods implementing
this idea and estimate their performances. We find that, with $\sim 1$ million
SNe Ia that can be achieved by the proposed D2k survey with the LSST telescope
(Zhan et al. 2008), multiplicative error of $\sim 0.5\%$ for source galaxies at
$z_s\sim 1$ can be detected and larger multiplicative error can be corrected to
the level of $0.5\%$. It is therefore a promising approach to control the
multiplicative to the sub-percent level required for stage IV projects. The
combination of the two methods even has the potential to diagnose and calibrate
galaxy intrinsic alignment, which is another major systematic error in cosmic
shear cosmology. | Probing Lepton Asymmetry with 21 cm Fluctuations: We investigate the issue of how accurately we can constrain the lepton number
asymmetry xi_nu = mu_nu/T_nu in the Universe by using future observations of 21
cm line fluctuations and cosmic microwave background (CMB). We find that
combinations of the 21 cm line and the CMB observations can constrain the
lepton asymmetry better than big-bang nucleosynthesis (BBN). Additionally, we
also discuss constraints on xi_nu in the presence of some extra radiation, and
show that the 21 cm line observations can substantially improve the constraints
obtained by CMB alone, and allow us to distinguish the effects of the lepton
asymmetry from the ones of extra radiation. |
Intergalactic Magnetic Fields from First-Order Phase Transitions: We study the generation of intergalactic magnetic fields in two models for
first-order phase transitions in the early Universe that have been studied
previously in connection with the generation of gravitational waves (GWs): the
Standard Model supplemented by an $|H|^6$ operator (SM+$H^6$) and a classically
scale-invariant model with an extra gauged U(1) $B - L$ symmetry (SM$_{B-L}$).
We consider contributions to magnetic fields generated by bubble collisions and
by turbulence in the primordial plasma, and we consider the hypotheses that
helicity is seeded in the gauge field or kinetically. We study the conditions
under which the intergalactic magnetic fields generated may be larger than the
lower bounds from blazar observations, and correlate them with the
observability of GWs and possible collider signatures. In the SM+$H^6$ model
bubble collisions alone cannot yield large enough magnetic fields, whereas
turbulence may do so. In the SM$_{B-L}$ model bubble collisions and turbulence
may both yield magnetic fields above the blazar bound unless the B$-$L gauge
boson is very heavy. In both models there may be observable GW and collider
signatures if sufficiently large magnetic fields are generated. | The Core-collapse rate from the Supernova Legacy Survey: We use three years of data from the Supernova Legacy Survey (SNLS) to study
the general properties of core-collapse and type Ia supernovae. This is the
first such study using the "rolling search" technique which guarantees
well-sampled SNLS light curves and good efficiency for supernovae brighter than
$i^\prime\sim24$. Using host photometric redshifts, we measure the supernova
absolute magnitude distribution down to luminosities $4.5 {\rm mag}$ fainter
than normal SNIa. Using spectroscopy and light-curve fitting to discriminate
against SNIa, we find a sample of 117 core-collapse supernova candidates with
redshifts $z<0.4$ (median redshift of 0.29) and measure their rate to be larger
than the type Ia supernova rate by a factor $4.5\pm0.8(stat.) \pm0.6 (sys.)$.
This corresponds to a core-collapse rate at $z=0.3$ of $[1.42\pm 0.3(stat.)
\pm0.3(sys.)]\times10^{-4}\yr^{-1}(h_{70}^{-1}\Mpc)^{-3}$. |
Qualitative probe of interacting dark energy with redshift-space
distortions: The imprint of interacting dark energy (IDE) needs to be correctly identified
in order to avoid bias in constraints on IDE. This paper investigates the
large-scale imprint of IDE in redshift space distortions, using $Euclid$-like
photometric prescriptions. A first attempt at incorporating the IDE dynamics in
the galaxy (clustering and evolution) biases is made. Without IDE dynamics
taken into account in the galaxy biases, as is conventionally done, the results
suggest that for a constant dark energy equation of state parameter, an IDE
model where the dark energy transfer rate is proportional to the dark energy
density exhibits an alternating, positive-negative effect in the redshift space
distortions angular power spectrum. However, when the IDE dynamics is
incorporated in the galaxy biases, it is found that the apparent
positive-negative alternating effect vanishes: implying that neglecting IDE
dynamics in the galaxy biases can result in ''artefacts'' that can lead to
incorrect identification of the IDE imprint. In general, the results show that
multi-tracer analysis will be needed to beat down cosmic variance in order for
the redshift space distortions angular power spectrum as a statistic to be a
viable diagnostic of IDE. Moreover, it is found that redshift space distortions
hold the potential to constrain IDE on large scales, at redshifts $z \,{\leq}\,
1$; with the scenario having IDE dynamics incorporated in the biases showing
better potential. | Cosmology with cosmic web environments II. Redshift-space auto and cross
power spectra: Degeneracies among parameters of the cosmological model are known to
drastically limit the information contained in the matter distribution. In the
first paper of this series, we shown that the cosmic web environments; namely
the voids, walls, filaments and nodes; can be used as a leverage to improve the
real-space constraints on a set of six cosmological parameters, including the
summed neutrino mass.
Following-upon these results, we propose to study the achievable constraints
of environment-dependent power spectra in redshift space where the velocities
add up information to the standard two-point statistics by breaking the
isotropy of the matter density field. A Fisher analysis based on a set of
thousands of Quijote simulations allows us to conclude that the combination of
power spectra computed in the several cosmic web environments is able to break
some degeneracies. Compared to the matter monopole and quadrupole information
alone, the combination of environment-dependent spectra tightens down the
constraints on key parameters like the matter density or the summed neutrino
mass by up to a factor of $5.5$. Additionally, while the information contained
in the matter statistic quickly saturates at mildly non-linear scales in
redshift space, the combination of power spectra in the environments appears as
a goldmine of information able to improve the constraints at all the studied
scales from $0.1$ to $0.5$ $h$/Mpc and suggests that further improvements are
reachable at even finer scales. |
Dark Matter Superfluidity: In these lectures I describe a theory of dark matter superfluidity developed
in the last few years. The dark matter particles are axion-like, with masses of
order eV. They Bose-Einstein condense into a superfluid phase in the central
regions of galaxy halos. The superfluid phonon excitations in turn couple to
baryons and mediate a long-range force (beyond Newtonian gravity). For a
suitable choice of the superfluid equation of state, this force reproduces the
various galactic scaling relations embodied in Milgrom's law. Thus the dark
matter and modified gravity phenomena represent different phases of a single
underlying substance, unified through the rich and well-studied physics of
superfluidity. | Measured redshift invariance of photon velocity: We report the first direct photon velocity measurements for extragalactic
objects. A fiber-optic, photon time-of-flight instrument, optimized for
relatively dim sources ($m 12$), is used to measure the velocity of visible
photons emanating from galaxies and quasars. Lightspeed is found to be
$3.00\pm0.03\times10^{8} \mathrm{m s}^{-1}$, and is invariant, within
experimental error, over the range of redshifts measured ($0\leq z\leq1.33$).
This measurement provides additional validation of Einstein's theory of General
Relativity (GR) and is consistent with the
Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) metricl, as well as several
alternative cosmological models, notably the hyperbolic anti-de Sitter metric,
though not with the pseudo-Euclidean de Sitter metric. |
Generating primordial features at large scales in two field models of
inflation: We investigate the generation of features at large scales in the primordial
power spectrum (PPS) when inflation is driven by two scalar fields. In
canonical single field models of inflation, these features are often generated
due to deviations from the slow-roll regime. While deviations from slow-roll
can be naturally achieved in two field models due to a sharp turn in the
trajectory in the field space, features at the largest scales of the types
suggested by CMB temperature anisotropies are more difficult to achieve in
models involving two canonical scalar fields due to the presence of
isocurvature fluctuations. We show instead that a coupling between the kinetic
terms of the scalar fields can easily produce such features. We discuss models
whose theoretical predictions are consistent with current observations and
highlight the implications of our results. | Mapmaking for Precision 21 cm Cosmology: In order to study the "Cosmic Dawn" and the Epoch of Reionization with 21 cm
tomography, we need to statistically separate the cosmological signal from
foregrounds known to be orders of magnitude brighter. Over the last few years,
we have learned much about the role our telescopes play in creating a
putatively foreground-free region called the "EoR window." In this work, we
examine how an interferometer's effects can be taken into account in a way that
allows for the rigorous estimation of 21 cm power spectra from interferometric
maps while mitigating foreground contamination and thus increasing sensitivity.
This requires a precise understanding of the statistical relationship between
the maps we make and the underlying true sky. While some of these calculations
would be computationally infeasible if performed exactly, we explore several
well-controlled approximations that make mapmaking and the calculation of map
statistics much faster, especially for compact and highly redundant
interferometers designed specifically for 21 cm cosmology. We demonstrate the
utility of these methods and the parametrized trade-offs between accuracy and
speed using one such telescope, the upcoming Hydrogen Epoch of Reionization
Array, as a case study. |
A pan-chromatic view of the galaxy cluster XMMU J1230.3+1339 at z=0.975
- Observing the assembly of a massive system: We present a comprehensive galaxy cluster study of XMMU J1230.3+1339 based on
a joint analysis of X-ray data, optical imaging and spectroscopy observations,
weak lensing results, and radio properties for achieving a detailed
multi-component view of this newly discovered system at z=0.975. We find an
optically very rich and massive system with
M200$\simeq$(4.2$\pm$0.8)$\times$10^14 M$\sun$, Tx$\simeq$5.3(+0.7--0.6)keV,
and Lx$\simeq$(6.5$\pm$0.7)$\times$10^44 erg/s, for which various widely used
mass proxies are measured and compared. We have identified multiple
cluster-related components including a central fly-through group close to core
passage with associated marginally extended 1.4GHz radio emission possibly
originating from the turbulent wake region of the merging event. On the cluster
outskirts we see evidence for an on-axis infalling group with a second
Brightest Cluster Galaxy (BCG) and indications for an additional off-axis group
accretion event. We trace two galaxy filaments beyond the nominal cluster
radius and provide a tentative reconstruction of the 3D-accretion geometry of
the system. In terms of total mass, ICM structure, optical richness, and the
presence of two dominant BCG-type galaxies, the newly confirmed cluster XMMU
J1230.3+1339 is likely the progenitor of a system very similar to the local
Coma cluster, differing by 7.6 Gyr of structure evolution. | Chasing the Tail of Cosmic Reionization with Dark Gap Statistics in the
Ly$α$ Forest over $5 < z < 6$: We present a new investigation of the intergalactic medium (IGM) near the end
of reionization using "dark gaps" in the Lyman-alpha (Ly$\alpha$) forest. Using
spectra of 55 QSOs at $z_{\rm em}>5.5$, including new data from the XQR-30 VLT
Large Programme, we identify gaps in the Ly$\alpha$ forest where the
transmission averaged over 1 comoving $h^{-1}\,{\rm Mpc}$ bins falls below 5%.
Nine ultra-long ($L > 80~h^{-1}\,{\rm Mpc}$) dark gaps are identified at $z<6$.
In addition, we quantify the fraction of QSO spectra exhibiting gaps longer
than $30~h^{-1}\,{\rm Mpc}$, $F_{30}$, as a function of redshift. We measure
$F_{30} \simeq 0.9$, 0.6, and 0.15 at $z = 6.0$, 5.8, and 5.6, respectively,
with the last of these long dark gaps persisting down to $z \simeq 5.3$.
Comparing our results with predictions from hydrodynamical simulations, we find
that the data are consistent with models wherein reionization extends
significantly below redshift six. Models wherein the IGM is essentially fully
reionized that retain large-scale fluctuations in the ionizing UV background at
$z \lesssim 6$ are also potentially consistent with the data. Overall, our
results suggest that signature of reionization in the form of islands of
neutral hydrogen and/or large-scale fluctuations in the ionizing background
remain present in the IGM until at least $z \simeq 5.3$. |
Large-scale alignments from WMAP and Planck: We revisit the alignments of the largest structures observed in the cosmic
microwave background (CMB) using the seven and nine-year WMAP and first-year
Planck data releases. The observed alignments -- the quadrupole with the
octopole and their joint alignment with the direction of our motion with
respect to the CMB (the dipole direction) and the geometry of the Solar System
(defined by the Ecliptic plane) -- are generally in good agreement with results
from the previous WMAP data releases. However, a closer look at full-sky data
on the largest scales reveals discrepancies between the earlier WMAP data
releases (three to seven-year) and the final nine-year release. There are also
discrepancies between all the WMAP data releases and the first-year Planck
release. Nevertheless, both the WMAP and Planck data confirm the alignments of
the largest observable CMB modes in the Universe. In particular, the p-values
for the mutual alignment between the quadrupole and octopole, and the alignment
of the plane defined by the two with the dipole direction, are both at the
greater than 3-sigma level for all three Planck maps studied. We also calculate
conditional statistics on the various alignments and find that it is currently
difficult to unambiguously identify a leading anomaly that causes the others or
even to distinguish correlation from causation. | Effects of Variable Newton Constant During Inflation: In this paper the effects of time-dependent Newton constant G during
inflation are studied. We present the formalism of curvature perturbations in
an inflationary system with a time-dependent Newton constant. As an example we
consider a toy model in which G undergoes a sudden change during inflation. By
imposing the appropriate matching conditions the imprints of this sharp change
in G on curvature perturbation power spectrum are studied. We show that if G
increases (decreases) during the transition the amplitude of curvature
perturbations on large scales decreases (increases). In our model with a sudden
change in G a continuous sinusoidal modulations on curvature power spectrum is
induced. However, in a realistic scenario in which the change in G has some
finite time scale we expect these sinusoidal modulations to be damped on short
scales. The generated features may be used to explain the observed glitches on
CMB power spectrum. This puts a bound on $\Delta G$ during inflation of roughly
the same order as current bounds on $\Delta G$ during the entire observed age
of the universe. |
Models of universe with a polytropic equation of state: I. The early
universe: We construct models of universe with a generalized equation of state
$p=(\alpha \rho+k\rho^{1+1/n})c^2$ having a linear component and a polytropic
component. In this paper, we consider positive indices $n>0$. In that case, the
polytropic component dominates in the early universe where the density is high.
For $\alpha=1/3$, $n=1$ and $k=-4/(3\rho_P)$, we obtain a model of early
universe describing the transition from a pre-radiation era to the radiation
era. The universe exists at any time in the past and there is no singularity.
However, for $t<0$, its size is less than the Planck length $l_P=1.62 10^{-35}
m$. In this model, the universe undergoes an inflationary expansion with the
Planck density $\rho_P=5.16 10^{99} g/m^3$ that brings it to a size $a_1=2.61
10^{-6} m$ at $t_1=1.25 10^{-42} s$ (about 20 Planck times $t_P$). For
$\alpha=1/3$, $n=1$ and $k=4/(3\rho_P)$, we obtain a model of early universe
with a new form of primordial singularity: The universe starts at t=0 with an
infinite density and a finite radius $a=a_1$. Actually, this universe becomes
physical at a time $t_i=8.32 10^{-45} s$ from which the velocity of sound is
less than the speed of light. When $a\gg a_1$, the universe evolves like in the
standard model. We describe the transition from the pre-radiation era to the
radiation era by analogy with a second order phase transition where the Planck
constant $\hbar$ plays the role of finite size effects (the standard Big Bang
theory is recovered for $\hbar=0$). | CARPool Covariance: Fast, unbiased covariance estimation for large-scale
structure observables: The covariance matrix $\boldsymbol{\Sigma}$ of non-linear clustering
statistics that are measured in current and upcoming surveys is of fundamental
interest for comparing cosmological theory and data and a crucial ingredient
for the likelihood approximations underlying widely used parameter inference
and forecasting methods. The extreme number of simulations needed to estimate
$\boldsymbol{\Sigma}$ to sufficient accuracy poses a severe challenge.
Approximating $\boldsymbol{\Sigma}$ using inexpensive but biased surrogates
introduces model error with respect to full simulations, especially in the
non-linear regime of structure growth. To address this problem we develop a
matrix generalization of Convergence Acceleration by Regression and Pooling
(CARPool) to combine a small number of simulations with fast surrogates and
obtain low-noise estimates of $\boldsymbol{\Sigma}$ that are unbiased by
construction. Our numerical examples use CARPool to combine GADGET-III $N$-body
simulations with fast surrogates computed using COmoving Lagrangian
Acceleration (COLA). Even at the challenging redshift $z=0.5$, we find variance
reductions of at least $\mathcal{O}(10^1)$ and up to $\mathcal{O}(10^4)$ for
the elements of the matter power spectrum covariance matrix on scales
$8.9\times 10^{-3}<k_\mathrm{max} <1.0$ $h {\rm Mpc^{-1}}$. We demonstrate
comparable performance for the covariance of the matter bispectrum, the matter
correlation function and probability density function of the matter density
field. We compare eigenvalues, likelihoods, and Fisher matrices computed using
the CARPool covariance estimate with the standard sample covariance estimators
and generally find considerable improvement except in cases where $\Sigma$ is
severely ill-conditioned. |
Stellar Mass and color dependence of the three-point correlation
function of galaxies in the local universe: The three-point correlation function (3PCF) for galaxies provides an
opportunity to measure the non-Gaussianity generated from nonlinear structure
formation and also probes information about galaxy formation and evolution that
is generally not available from the two-point correlation function (2PCF). We
measure the 3PCF of the Sloan Digital Sky Survey DR7 main sample galaxies in
both redshift and projected spaces on scales up to 40Mpc/h. We explore the
dependence of the 3PCF on galaxy stellar mass and color in order to constrain
the formation and evolution for galaxies of different properties. The study of
the dependence on these properties also helps better constrain the relation
between galaxy stellar mass and color and the properties of their hosting
dark-matter halos. We focus on the study of the reduced 3PCF, Q, defined as the
ratio between the 3PCF and the sum of the products of the 2PCFs. We find a very
weak stellar mass dependence of Q in both redshift and projected spaces. On
small scales, more massive galaxies tend to have slightly higher amplitudes of
Q. The shape dependence of Q is also weak on these small scales, regardless of
stellar mass and color. The reduced 3PCF has a strong color dependence for the
low-mass galaxies, while no significant dependence on color is found for the
high-mass galaxies. Low-mass red galaxies have higher amplitudes and stronger
shape dependence of the reduced 3PCF than the blue galaxies, implying that
these low-mass red galaxies tend to populate filamentary structures. The linear
galaxy bias model fails to interpret the color dependence of Q, emphasizing the
importance of a nonvanishing quadratic bias parameter in the correct modeling
of the galaxy color distribution. | Self-calibrating the gravitational shear-intrinsic ellipticity-intrinsic
ellipticity (GII) cross-correlation: We extend the 3-point intrinsic alignment self-calibration technique to the
gravitational shear-intrinsic ellipticity-intrinsic ellipticity (GII)
bispectrum. The proposed technique will allow the measurement and removal of
the GII intrinsic alignment contamination from the cross-correlation weak
lensing signal. While significantly decreased from using cross-correlations
instead of auto-correlation in a single photo-z bin, the GII contamination
persists in adjacent photo-z bins and must be accounted for and removed from
the lensing signal. We relate the GII and galaxy density-intrinsic
ellipticity-intrinsic ellipticity (gII) bispectra through use of the galaxy
bias, and develop the estimator necessary to isolate the gII bispectrum from
observations. We find that the GII self-calibration technique performs at a
level comparable to that of the gravitational shear-gravitational
shear-intrinsic ellipticity correlation (GGI) self-calibration technique, with
measurement error introduced through the gII estimator generally negligible
when compared to minimum survey error. The accuracy of the relationship between
the GII and gII bispectra typically allows the GII self-calibration to reduce
the GII contamination by a factor of 10 or more for all adjacent photo-z bin
combinations at $\ell>300$. For larger scales, we find that the GII
contamination can be reduced by a factor of 3-5 or more. The GII
self-calibration technique is complementary to the existing GGI
self-calibration technique, which together will allow the total intrinsic
alignment cross-correlation signal in 3-point weak lensing to be measured and
removed. |
Theoretical bounds on the tensor-to-scalar ratio in the cosmic microwave
background: Tensor modes in the cosmic microwave background are one of the most robust
signatures of inflation. We derive theoretical bounds on the tensor fraction,
as a generalization of the well-known Lyth bound. Under reasonable assumptions,
the new bounds are at least two orders of magnitude stronger than the original
one. We comment on a previously derived generalization, the so-called
Efstathiou-Mack relationship. We also derive a new absolute upper bound on
tensors using de Sitter entropy bounds. | Quasars as high-redshift standard candles: In the past few years, we built a Hubble diagram of quasars up to redshift
z$\sim$7, based on the nonlinear relation between quasars' x-ray and UV
luminosities. Such a Hubble diagram shows a >4$\sigma$ deviation from the
standard flat $\Lambda$CDM model at z>1.5. Given the important consequences of
this result, it is fundamental to rule out any systematic effect in the
selection of the sample and/or in the flux measurements, and to investigate
possible redshift dependences of the relation, that would invalidate the use of
quasars as standard candles. Here we review all the observational results
supporting our method: the match of the Hubble diagram of quasars with that of
supernovae in the common redshift range, the constant slope of the relation at
all redshifts, the redshift non-evolution of the spectral properties of our
sources both in the x-rays and in the UV. An independent test of our results
requires the observation of other standard candles at high redshift. In
particular, we expect that future observations of supernovas at z>2 will
confirm the deviation from the concordance model found with the Hubble diagram
of quasars. |
Anisotropic inflation reexamined: upper bound on broken rotational
invariance during inflation: The presence of a light vector field coupled to a scalar field during
inflation makes a distinct prediction: the observed correlation functions of
the cosmic microwave background (CMB) become statistically anisotropic. We
study the implications of the current bound on statistical anisotropy derived
from the Planck 2013 CMB temperature data for such a model. The previous
calculations based on the attractor solution indicate that the magnitude of
anisotropy in the power spectrum is proportional to $N^2$, where $N$ is the
number of $e$-folds of inflation counted from the end of inflation. In this
paper, we show that the attractor solution is not compatible with the current
bound, and derive new predictions using another branch of anisotropic
inflation. In addition, we improve upon the calculation of the mode function of
perturbations by including the leading-order slow-roll corrections. We find
that the anisotropy is roughly proportional to
$[2(\varepsilon_H+4\eta_H)/3-4(c-1)]^{-2}$, where $\varepsilon_H$ and $\eta_H$
are the usual slow-roll parameters and $c$ is the parameter in the model,
regardless of the form of potential of an inflaton field. The bound from Planck
implies that breaking of rotational invariance during inflation (characterized
by the background homogeneous shear divided by the Hubble rate) is limited to
be less than ${\cal O}(10^{-9})$. This bound is many orders of magnitude
smaller than the amplitude of breaking of time translation invariance, which is
observed to be ${\cal O}(10^{-2})$. | The Past History of Galaxy Clusters told by their present neighbors: Galaxy clusters can play a key role in modern cosmology provided their
evolution is properly understood. However, observed clusters give us only a
single timeframe of their dynamical state. Therefore, finding present
observable data of clusters that are well correlated to their assembly history
constitutes an inestimable tool for cosmology. Former studies correlating
environmental descriptors of clusters to their formation history are dominated
by halo mass - environment relations. This paper presents a mass-free
correlation between the present neighbor distribution of cluster-size halos and
the latter mass assembly history. From the Big Multidark simulation, we extract
two large samples of random halos with masses ranging from Virgo to Coma
cluster sizes. Additionally, to find the main environmental culprit for the
formation history of the Virgo cluster, we compare the Virgo-size halos to 200
Virgo-like halos extracted from simulations that resemble the local Universe.
The number of neighbors at different cluster-centric distances permits
discriminating between clusters with different mass accretion histories.
Similarly to Virgo-like halos, clusters with numerous neighbors within a
distance of about 2 times their virial radius experience a transition at z~1
between an active period of mass accretion, relative to the mean, and a quiet
history. On the contrary, clusters with few neighbors share an opposite trend:
from passive to active assembly histories. Additionally, clusters with massive
companions within about 4 times their virial radius tend to have recent active
merging histories. Therefore, the radial distribution of cluster neighbors
provides invaluable insights into the past history of these objects. |
CppTransport: a platform to automate calculation of inflationary
correlation functions: CppTransport is a numerical platform that can automatically generate and
solve the evolution equations for the 2- and 3-point correlation functions (in
field space and for the curvature perturbation) for any inflationary model with
canonical kinetic terms. It makes no approximations beyond the applicability of
tree-level perturbation theory. Given an input Lagrangian, CppTransport
performs symbolic calculations to determine the 'Feynman rules' of the model
and generates efficient C++ to integrate the correlation functions of interest.
It includes a visualization suite that automates extraction of observable
quantities from the raw n-point functions and generates high quality plots with
minimal manual intervention. It is intended to be used as a collaborative
platform, promoting the rapid investigation of models and systematizing their
comparison with observation. This guide describes how to install and use the
system, and illustrates its use through some simple examples. | Discrepant Mass Estimates in the Cluster of Galaxies Abell 1689: We present a new mass estimate of a well-studied gravitational lensing
cluster, Abell 1689, from deep Chandra observations with a total exposure of
200 ks. Within r=200 h-1 kpc, the X-ray mass estimate is systematically lower
than that of lensing by 30-50%. At r>200 h-1 kpc, the mass density profiles
from X-ray and weak lensing methods give consistent results. The most recent
weak lensing work suggest a steeper profile than what is found from the X-ray
analysis, while still in agreement with the mass at large radii. Previous
studies have suggested that cooler small-scale structures can bias X-ray
temperature measurements or that the northern part of the cluster is disturbed.
We find these scenarios unlikely to resolve the central mass discrepancy since
the former requires 70-90% of the space to be occupied by these cool structures
and excluding the northern substructure does not significantly affect the total
mass profiles. A more plausible explanation is a projection effect. We also
find that the previously reported high hard-band to broad-band temperature
ratio in A1689, and many other clusters observed with Chandra, may be resulting
from the instrumental absorption that decreases 10-15% of the effective area at
~1.75 keV. |
Dark matter phenomenology of high speed galaxy cluster collisions: We perform a general computational analysis of possible post-collision mass
distributions in high-speed galaxy cluster collisions in the presence of weakly
self-interacting dark matter. Using this analysis, we show that weakly
self-scattering dark matter can impart subtle yet measurable features in the
mass distributions of colliding galaxy clusters even without significant
disruptions to the dark matter halos of the colliding galaxy clusters
themselves. Most profound such evidences are found to reside in the tails of
dark matter halos' distributions, in the space between the colliding galaxy
clusters. This feature appears in our simulations as shells of scattered dark
matter expanding in alignment with the outgoing original galaxy clusters,
contributing significant densities to projected mass distributions at large
distances from collision centers and large scattering angles up to $90^\circ$.
Our simulations indicate that as much as 20% of the total collision's mass may
be deposited into such structures without noticeable disruptions to the main
galaxy clusters. Such structures at large scattering angles are forbidden
however in purely gravitational high-speed galaxy cluster collisions.
Convincing identification of such structures in real colliding galaxy clusters
would be a clear indication of the self-interacting nature of dark matter. Our
findings may explain the dark matter ring feature recently found in the
long-range reconstructions of the mass distribution of the colliding galaxy
cluster CL0024+017. | First underground results with NEWAGE-0.3a direction-sensitive dark
matter detector: A direction-sensitive dark matter search experiment at Kamioka underground
laboratory with the NEWAGE-0.3a detector was performed. The NEWAGE- 0.3a
detector is a gaseous micro-time-projection chamber filled with CF4 gas at 152
Torr. The fiducial volume and target mass are 20*25*31 cm3 and 0.0115 kg,
respectively. With an exposure of 0.524 kgdays, improved spin-dependent weakly
interacting massive particle (WIMP)-proton cross section limits by a
direction-sensitive method were achieved including a new record of 5400 pb for
150 GeV/c2 WIMPs. We studied the remaining background and found that ambient
gamma-rays contributed about one-fifth of the remaining background and
radioactive contaminants inside the gas chamber contributed the rest. |
Zoomed cosmological simulations of Milky Way sized halos in f(R)-gravity: We investigate the impact of f(R) modified gravity on the internal properties
of Milky Way sized dark matter halos in a set of cosmological zoom simulations
of seven halos from the Aquarius suite, carried out with our code MG-GADGET in
the Hu & Sawicki f(R) model. Also, we calculate the fifth forces in ideal
NFW-halos as well as in our cosmological simulations and compare them against
analytic model predictions for the fifth force inside spherical objects. We
find that these theoretical predictions match the forces in the ideal halos
very well, whereas their applicability is somewhat limited for realistic
cosmological halos. Our simulations show that f(R) gravity significantly
affects the dark matter density profile of Milky Way sized objects as well as
their circular velocities. In unscreened regions, the velocity dispersions are
increased by up to 40% with respect to LCDM for viable f(R) models. This
difference is larger than reported in previous works. The Solar circle is fully
screened in $f_{R0} = -10^{-6}$ models for Milky Way sized halos, while this
location is unscreened for slightly less massive objects. Within the scope of
our limited halo sample size, we do not find a clear dependence of the
concentration parameter of dark matter halos on $f_{R0}$. | The Carnegie-Chicago Hubble Program. VIII. An Independent Determination
of the Hubble Constant Based on the Tip of the Red Giant Branch: We present a new and independent determination of the local value of the
Hubble constant based on a calibration of the Tip of the Red Giant Branch
(TRGB) applied to Type Ia supernovae (SNeIa). We find a value of Ho = 69.8 +/-
0.8 (+/-1.1\% stat) +/- 1.7 (+/-2.4\% sys) km/sec/Mpc. The TRGB method is both
precise and accurate, and is parallel to, but independent of the Cepheid
distance scale. Our value sits midway in the range defined by the current
Hubble tension. It agrees at the 1.2-sigma level with that of the Planck 2018
estimate, and at the 1.7-sigma level with the SHoES measurement of Ho based on
the Cepheid distance scale. The TRGB distances have been measured using deep
Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging of
galaxy halos. The zero point of the TRGB calibration is set with a distance
modulus to the Large Magellanic Cloud of 18.477 +/- 0.004 (stat) +/-0.020 (sys)
mag, based on measurement of 20 late-type detached eclipsing binary (DEB)
stars, combined with an HST parallax calibration of a 3.6 micron Cepheid
Leavitt law based on Spitzer observations. We anchor the TRGB distances to
galaxies that extend our measurement into the Hubble flow using the recently
completed Carnegie Supernova Project I sample containing about 100
well-observed SNeIa. There are several advantages of halo TRGB distance
measurements relative to Cepheid variables: these include low halo reddening,
minimal effects of crowding or blending of the photometry, only a shallow
(calibrated) sensitivity to metallicity in the I-band, and no need for multiple
epochs of observations or concerns of different slopes with period. In
addition, the host masses of our TRGB host-galaxy sample are higher on average
than the Cepheid sample, better matching the range of host-galaxy masses in the
CSP distant sample, and reducing potential systematic effects in the SNeIa
measurements. |
The Shape Dependence of Vainshtein Screening in the Cosmic Matter
Bispectrum: One of the most pressing questions in modified gravity is how deviations from
general relativity can manifest in upcoming galaxy surveys. This is especially
relevant for theories exhibiting Vainshtein screening, where such deviations
are efficiently suppressed within a (typically large) Vainshtein radius.
However, Vainshtein screening is known to be shape dependent: it is most
effective around spherical sources, weaker around cylindrical objects and
completely absent for planar sources. The Cosmic Web therefore offers a testing
ground, as it displays many shapes in the form of clusters, filaments and
walls.
In this work, we explicitly derive the signature of the shape dependence of
Vainshtein screening on the matter bispectrum, by considering a cubic Galileon
model with a conformal coupling to matter and a cosmological constant. We
perform a second order perturbative analysis, deriving analytic, integral
expressions for the bispectrum, which we integrate using hi_class. We find that
the shape dependence of Vainshtein screening enters the bispectrum with a
unique scale-factor dependence of $\propto a^{3/2}$. The magnitude of the
effect today is up to 2 % for a model whose linear growth rate deviates up to 5
% from $\Lambda$CDM. | Probing the X-Ray Binary Populations of the Ring Galaxy NGC 1291: We present Chandra studies of the X-ray binary (XRB) populations in the bulge
and ring regions of the ring galaxy NGC 1291. We detect 169 X-ray point sources
in the galaxy, 75 in the bulge and 71 in the ring, utilizing the four available
Chandra observations totaling an effective exposure of 179 ks. We report
photometric properties of these sources in a point-source catalog. There are
~40% of the bulge sources and ~25% of the ring sources showing >3\sigma
long-term variability in their X-ray count rate. The X-ray colors suggest that
a significant fraction of the bulge (~75%) and ring (~65%) sources are likely
low-mass X-ray binaries (LMXBs). The spectra of the nuclear source indicate
that it is a low-luminosity AGN with moderate obscuration; spectral variability
is observed between individual observations. We construct 0.3-8.0 keV X-ray
luminosity functions (XLFs) for the bulge and ring XRB populations, taking into
account the detection incompleteness and background AGN contamination. We reach
90% completeness limits of ~1.5\times10^{37} and ~2.2\times10^{37} erg/s for
the bulge and ring populations, respectively. Both XLFs can be fit with a
broken power-law model, and the shapes are consistent with those expected for
populations dominated by LMXBs. We perform detailed population synthesis
modeling of the XRB populations in NGC 1291, which suggests that the observed
combined XLF is dominated by an old LMXB population. We compare the bulge and
ring XRB populations, and argue that the ring XRBs are associated with a
younger stellar population than the bulge sources, based on the relative
overdensity of X-ray sources in the ring, the generally harder X-ray color of
the ring sources, the overabundance of luminous sources in the combined XLF,
and the flatter shape of the ring XLF. |
Constraining Coupling Constants' Variation with Supernovae, Quasars, and
GRBs: Dirac, in 1937 proposed the variation of coupling constants derived from his
large number hypothesis. Efforts have continued since then to constrain their
variation by various methods. We briefly discuss several methods used for the
purpose while focusing primarily on the use of supernovae type 1a, quasars, and
gamma-ray bursts (GRBs) as cosmological probes for determining cosmological
distances. Supernovae type Ia (SNeIa) are considered the best standard candles
since their intrinsic luminosity can be determined precisely from their light
curves. However, they have only been observed up to about redshift $z=2.3$,
mostly at $z<1.5$. Quasars are the brightest non-transient cosmic sources in
the Universe. They have been observed up to $z=7.5$. Certain types of quasars
can be calibrated well enough for their use as standard candles but with a
higher degree of uncertainty in their intrinsic luminosity than the SNeIa. GRBs
are even brighter than quasars, observed up to $z=9.4$. Their radiation lasts
from 10s of milliseconds to several minutes and, in rare cases, for a few
hours. However, they are even more challenging to calibrate as standard candles
than quasars. What if the standard candles' intrinsic luminosities are affected
when the coupling constants become dynamic? This paper uses our earlier finding
that the speed of light c, the gravitational constant G, the Planck constant h,
and the Boltzmann constant k variations are correlated as $G\thicksim
c^{3}\thicksim h^{3}\thicksim k^{3/2}$ with
$(\dot{G}/G)_{0}=3(\dot{c}/c)_{0}=(\dot{h}/h)_{0}=1.5 (\dot{k}/k)_{0}=5.4H_{0}
=3.90(\pm 0.04)\times 10^{-10} yr^{-1}$ corroborates it with SNeIa, quasars,
and GRBs observational data. Also, we show that this covarying coupling
constant model may be better than the standard {\Lambda}CDM model for using
quasars and GRBs as standard candles and predict the mass of the GRBs scales as
$((1+z)^{1/3}-1)$. | Impact of an accurate modeling of primordial chemistry in high
resolution studies: The formation of the first stars in the Universe is regulated by a sensitive
interplay of chemistry and cooling with the dynamics of a self-gravitating
system. As the outcome of the collapse and the final stellar masses depend
sensitively on the thermal evolution, it is necessary to accurately model the
thermal evolution in high resolution simulations. As previous investigations
raised doubts regarding the convergence of the temperature at high resolution,
we investigate the role of the numerical method employed to model the chemistry
and the thermodynamics. Here we compare the standard implementation in the
adaptive-mesh refinement code \verb|ENZO|, employing a first order backward
differentiation formula (BDF), with the 5th order accurate BDF solver
\verb|DLSODES|. While the standard implementation in \verb|ENZO| shows a strong
dependence on the employed resolution, the results obtained with \verb|DLSODES|
are considerably more robust, both with respect to the chemistry and
thermodynamics, but also for dynamical quantities such as density, total energy
or the accretion rate. We conclude that an accurate modeling of the chemistry
and thermodynamics is central for primordial star formation. |
Fingerprints of Galactic Loop I on the Cosmic Microwave Background: We investigate possible imprints of galactic foreground structures such as
the "radio loops" in the derived maps of the cosmic microwave background.
Surprisingly there is evidence for these not only at radio frequencies through
their synchrotron radiation, but also at microwave frequencies where emission
by dust dominates. This suggests the mechanism is magnetic dipole radiation
from dust grains enriched by metallic iron or ferrimagnetic materials. This new
foreground we have identified is present at high galactic latitudes, and
potentially dominates over the expected $B$-mode polarization signal due to
primordial gravitational waves from inflation. | Chameleon Dark Energy and Atom Interferometry: Atom interferometry experiments are searching for evidence of chameleon
scalar fields with ever-increasing precision. As experiments become more
precise, so too must theoretical predictions. Previous work has made numerous
approximations to simplify the calculation, which in general requires solving a
3-dimensional nonlinear partial differential equation (PDE). In this paper, we
introduce a new technique for calculating the chameleonic force, using a
numerical relaxation scheme on a uniform grid. This technique is more general
than previous work, which assumed spherical symmetry to reduce the PDE to a
1-dimensional ordinary differential equation (ODE). We examine the effects of
approximations made in previous efforts on this subject, and calculate the
chameleonic force in a set-up that closely mimics the recent experiment of
Hamilton et al. Specifically, we simulate the vacuum chamber as a cylinder with
dimensions matching those of the experiment, taking into account the
backreaction of the source mass, its offset from the center, and the effects of
the chamber walls. Remarkably, the acceleration on a test atomic particle is
found to differ by only 20% from the approximate analytical treatment. These
results allow us to place rigorous constraints on the parameter space of
chameleon field theories, although ultimately the constraint we find is the
same as the one we reported in Hamilton et al. because we had slightly
underestimated the size of the vacuum chamber. This new computational technique
will continue to be useful as experiments become even more precise, and will
also be a valuable tool in optimizing future searches for chameleon fields and
related theories. |
Characteristic features of gravitational wave lensing as probe of lens
mass model: To recognize gravitational wave lensing events and being able to
differentiate between similar lens models will be of crucial importance once
one will be observing several lensing events of gravitational waves per year.
In this work, we study the lensing of gravitational waves in the context of
LISA sources and wave-optics regime. While different papers before ours studied
microlensing effects enhanced by simultaneous strong lensing, we focus on
frequency (time) dependent phase effects produced by one lens that will be
visible with only one lensed image. We will show how, in the interference
regime (i.e. when interference patterns are present in the lensed image), we
are able to i) distinguish a lensed waveform from an unlensed one, and ii)
differentiate between different lens models. In pure wave-optics, on the other
hand, the feasibility of the study depends on the SNR of the signal and/or the
magnitude of the lensing effect. To achieve these goals we study the phase of
the amplification factor of the different lens models and its effect on the
unlensed waveform, and we exploit the signal-to-noise calculation for a
qualitative analysis. | Constraining self-interacting dark matter with scaling laws of observed
halo surface densities: The observed surface densities of dark matter halos are known to follow a
simple scaling law, ranging from dwarf galaxies to galaxy clusters, with a weak
dependence on their virial mass. Here we point out that this can not only be
used to provide a method to determine the standard relation between halo mass
and concentration, but also to use large samples of objects in order to place
constraints on dark matter self-interactions that can be more robust than
constraints derived from individual objects. We demonstrate our method by
considering a sample of about 50 objects distributed across the whole halo mass
range, and by modelling the effect of self-interactions in a way similar to
what has been previously done in the literature. Using additional input from
simulations then results in a constraint on the self-interaction cross section
per unit dark matter mass of about $\sigma/m_\chi\lesssim 0.3$ cm$^2$/g. We
expect that these constraints can be significantly improved in the future, and
made more robust, by i) an improved modelling of the effect of
self-interactions, both theoretical and by comparison with simulations, ii)
taking into account a larger sample of objects and iii) by reducing the
currently still relatively large uncertainties that we conservatively assign to
the surface densities of individual objects. The latter can be achieved in
particular by using kinematic observations to directly constrain the average
halo mass inside a given radius, rather than fitting the data to a pre-selected
profile and then reconstruct the mass. For a velocity-independent
cross-section, our current result is formally already somewhat smaller than the
range $0.5-5$ cm$^2$/g that has been invoked to explain potential
inconsistencies between small-scale observations and expectations in the
standard collisionless cold dark matter paradigm. |
Stochastic Background of Gravitational Waves Generated by Eccentric
Neutron Star Binaries: Binary systems emit gravitational waves in a well-known pattern; for binaries
in circular orbits, the emitted radiation has a frequency that is twice the
orbital frequency. Systems in eccentric orbits, however, emit gravitational
radiation in the higher harmonics too. In this paper, we are concerned with the
stochastic background of gravitational waves generated by double neutron star
systems of cosmological origin in eccentric orbits. We consider in particular
the long-lived systems, that is, those binaries for which the time to
coalescence is longer than the Hubble time ($\sim 10$Gyr). Thus, we consider
double neutron stars with orbital frequencies ranging from $10^{-8}$ to
$2\times 10^{-6}$Hz. Although in the literature some papers consider the
spectra generated by eccentric binaries, there is still space for alternative
approaches for the calculation of the backgrounds. In this paper, we use a
method that consists in summing the spectra that would be generated by each
harmonic separately in order to obtain the total background. This method allows
us to clearly obtain the influence of each harmonic on the spectra. In
addition, we consider different distribution functions for the eccentricities
in order to investigate their effects on the background of gravitational waves
generated. At last, we briefly discuss the detectability of this background by
space-based gravitational wave antennas and pulsar timing arrays. | Counterrotating Stars in Simulated Galaxy Disks: Counterrotating stars in disk galaxies are a puzzling dynamical feature whose
origin has been ascribed to either satellite accretion events or to disk
instabilities triggered by deviations from axisymmetry. We use a cosmological
simulation of the formation of a disk galaxy to show that counterrotating
stellar disk components may arise naturally in hierarchically-clustering
scenarios even in the absence of merging. The simulated disk galaxy consists of
two coplanar, overlapping stellar components with opposite spins: an inner
counterrotating bar-like structure made up mostly of old stars surrounded by an
extended, rotationally-supported disk of younger stars. The opposite-spin
components originate from material accreted from two distinct filamentary
structures which at turn around, when their net spin is acquired, intersect
delineating a "V"-like structure. Each filament torques the other in opposite
directions; the filament that first drains into the galaxy forms the inner
counterrotating bar, while material accreted from the other filament forms the
outer disk. Mergers do not play a substantial role and most stars in the galaxy
are formed in situ; only 9% of all stars are contributed by accretion events.
The formation scenario we describe here implies a significant age difference
between the co- and counterrotating components, which may be used to
discriminate between competing scenarios for the origin of counterrotating
stars in disk galaxies. |
Fermi/LAT observations of Dwarf Galaxies highly constrain a Dark Matter
Interpretation of Excess Positrons seen in AMS-02, HEAT, and PAMELA: It is shown that a Weakly Interacting Massive dark matter Particle (WIMP)
interpretation for the positron excess observed in a variety of experiments,
HEAT, PAMELA, and AMS-02, is highly constrained by the Fermi/LAT observations
of dwarf galaxies. In particular, this paper has focused on the annihilation
channels that best fit the current AMS-02 data (Boudaud et al., 2014). The
Fermi satellite has surveyed the $\gamma$-ray sky, and its observations of
dwarf satellites are used to place strong bounds on the annihilation of WIMPs
into a variety of channels. For the single channel case, we find that dark
matter annihilation into {$b\bar{b}$, $e^+e^-$, $\mu^+\mu^-$, $\tau^+\tau^-$,
4-$e$, or 4-$\tau$} is ruled out as an explanation of the AMS positron excess
(here $b$ quarks are a proxy for all quarks, gauge and Higgs bosons). In
addition, we find that the Fermi/LAT 2$\sigma$ upper limits, assuming the
best-fit AMS-02 branching ratios, exclude multichannel combinations into
$b\bar{b}$ and leptons. The tension between the results might relax if the
branching ratios are allowed to deviate from their best-fit values, though a
substantial change would be required. Of all the channels we considered, the
only viable channel that survives the Fermi/LAT constraint and produces a good
fit to the AMS-02 data is annihilation (via a mediator) to 4-$\mu$, or mainly
to 4-$\mu$ in the case of multichannel combinations. | Halo concentration strengthens dark matter constraints in galaxy-galaxy
strong lensing analyses: A defining prediction of the cold dark matter (CDM) cosmological model is the
existence of a very large population of low-mass haloes. This population is
absent in models in which the dark matter particle is warm (WDM). These
alternatives can, in principle, be distinguished observationally because halos
along the line-of-sight can perturb galaxy-galaxy strong gravitational lenses.
Furthermore, the WDM particle mass could be deduced because the cut-off in
their halo mass function depends on the mass of the particle. We systematically
explore the detectability of low-mass haloes in WDM models by simulating and
fitting mock lensed images. Contrary to previous studies, we find that halos
are harder to detect when they are either behind or in front of the lens.
Furthermore, we find that the perturbing effect of haloes increases with their
concentration: detectable haloes are systematically high-concentration haloes,
and accounting for the scatter in the mass-concentration relation boosts the
expected number of detections by as much as an order of magnitude. Haloes have
lower concentration for lower particle masses and this further suppresses the
number of detectable haloes beyond the reduction arising from the lower halo
abundances alone. Taking these effects into account can make lensing
constraints on the value of the mass function cut-off at least an order of
magnitude more stringent than previously appreciated. |
Disks in the sky: A reassessment of the WMAP "cold spot": We reassess the evidence that WMAP temperature maps contain a statistically
significant "cold spot" by repeating the analysis using simple circular top-hat
(disk) weights, as well as Gaussian weights of varying width. Contrary to
previous results that used Spherical Mexican Hat Wavelets, we find no
significant signal at any scale when we compare the coldest spot from our sky
to ones from simulated Gaussian random, isotropic maps. We trace this apparent
discrepancy to the fact that WMAP cold spot's temperature profile just happens
to favor the particular profile given by the wavelet. Since randomly generated
maps typically do not exhibit this coincidence, we conclude that the original
cold spot significance originated at least partly due to a fortuitous choice of
using a particular basis of weight functions. We also examine significance of a
more general measure that returns the most significant result among several
choices of the weighting function, angular scale of the spot, and the
statistics applied, and again find a null result. | Pulsar Timing Probes of Primordial Black Holes and Subhalos: Pulsars act as accurate clocks, sensitive to gravitational redshift and
acceleration induced by transiting clumps of matter. We study the sensitivity
of pulsar timing arrays (PTAs) to single transiting compact objects, focusing
on primordial black holes and compact subhalos in the mass range from $10^{-12}
M _{\odot}$ to well above $100~M_\odot$. We find that the Square Kilometer
Array can constrain such objects to be a subdominant component of the dark
matter over this entire mass range, with sensitivity to a dark matter
sub-component reaching the sub-percent level over significant parts of this
range. We also find that PTAs offer an opportunity to probe substantially less
dense objects than lensing because of the large effective radius over which
such objects can be observed, and we quantify the subhalo concentration
parameters which can be constrained. |
What size halos do local LIRGs live in?: This work investigates the preferred environment of local Luminous IR
Galaxies (LIRGs) in terms of the host halos that they inhabit, and in
comparison to a control galaxy sample. The LIRGs are drawn from the IRAS Point
Source Catalogue redshift survey (PSCz), while the control sample is drawn from
the 2MASS redshift survey (2MRS). A friends-of-friends algorithm was run on the
2MRS sample to identify galaxies living in the same dark matter halos and the
PSCz galaxies were then associated with these identified halos. We show that
the relative probability of finding local LIRGs with respect to 2MASS galaxies
is largest in approximately group size halos (Mhalo~10^13M_sun), and declines
both in the cluster regime and in smaller halos. This confirms, using a
different technique than in previous work, that local LIRGs are indeed more
abundant in group environments than elsewhere. We also find a trend between the
LIR values of LIRGs and their location within their host dark matter halos,
such that the average location of LIRGs with high IR luminosity is closer to
the halo centre than for low IR luminosity galaxies. Moreover, this trend does
not seem to depend on halo mass. | Fast magnetic field amplification in the early Universe: growth of
collisionless plasma instabilities in turbulent media: In this work we report a numerical study of the cosmic magnetic field
amplification due to collisionless plasma instabilities. The collisionless
magnetohydrodynamic equations derived account for the pressure anisotropy that
leads, in specific conditions, to the firehose and mirror instabilities. We
study the time evolution of seed fields in turbulence under the influence of
such instabilities. An approximate analytical time evolution of magnetic field
is provided. The numerical simulations and the analytical predictions are
compared. We found that i) amplification of magnetic field was efficient in
firehose unstable turbulent regimes, but not in the mirror unstable models, ii)
the growth rate of the magnetic energy density is much faster than the
turbulent dynamo, iii) the efficient amplification occurs at small scales. The
analytical prediction for the correlation between the growth timescales with
pressure anisotropy ratio is confirmed by the numerical simulations. These
results reinforce the idea that pressure anisotropies - driven naturally in a
turbulent collisionless medium, e.g. the intergalactic medium -, could
efficiently amplify the magnetic field in the early Universe
(post-recombination era), previous to the collapse of the first large-scale
gravitational structures. This mechanism, though fast for the small scale
fields ($\sim$kpc scales), is however unable to provide relatively strong
magnetic fields at large scales. Other mechanisms that were not accounted here
(e.g., collisional turbulence once instabilities are quenched, velocity shear,
or gravitationally induced inflows of gas into galaxies and clusters) could
operate afterwards to build up large scale coherent field structures in the
long time evolution. |
Shock-ionization in the Extended Emission-Line Region of 3C~305. The
last piece of the (optical) puzzle: We present new Gemini spectroscopical data of the Extended Emission-Line
Region of 3C~305 radio galaxy in order to achieve the final answer of the
long-standing question about the ionizing mechanism. The spectra show strong
kinematic disturbances within the most intense line-emitting region. The
relative intensities amongst the emission lines agree with the gas being
shocked during the interaction of the powerful radio jets with the ambient
medium. The emission from the recombination region acts as a very effective
cooling mechanism, which is supported by the presence of a neutral outflow.
However, the observed intensity is almost an order of magnitude lower than
expected in a pure shock model. So auto-ionizing shock models, in low-density
and low-abundance regime, are required in order to account for the observed
emission within the region. This scenario also supports the hypothesis that the
optical emitting gas and the X-ray plasma are in pressure balance. | Bayesian inferences of galaxy formation from the K-band luminosity and
HI mass functions of galaxies: constraining star formation and feedback: We infer mechanisms of galaxy formation for a broad family of semi-analytic
models (SAMs) constrained by the K-band luminosity function and HI mass
function of local galaxies using tools of Bayesian analysis. Even with a broad
search in parameter space the whole model family fails to match to constraining
data. In the best fitting models, the star formation and feedback parameters in
low-mass haloes are tightly constrained by the two data sets, and the analysis
reveals several generic failures of models that similarly apply to other
existing SAMs. First, based on the assumption that baryon accretion follows the
dark matter accretion, large mass-loading factors are required for haloes with
circular velocities lower than 200 km/s, and most of the wind mass must be
expelled from the haloes. Second, assuming that the feedback is powered by
Type-II supernovae with a Chabrier IMF, the outflow requires more than 25% of
the available SN kinetic energy. Finally, the posterior predictive
distributions for the star formation history are dramatically inconsistent with
observations for masses similar to or smaller than the Milky-Way mass. The
inferences suggest that the current model family is still missing some key
physical processes that regulate the gas accretion and star formation in
galaxies with masses below that of the Milky Way. |
Re-Examining the Evidence of the Hercules-Corona-Borealis Great Wall: In the {\Lambda}-CDM paradigm of cosmology, anisotropies larger than 260 Mpc
shouldn't exist. However, the existence of the Hercules-Corona Borealis Great
Wall (HCB) is purported to challenge this principle by some with an estimated
size exceeding 2000 Mpc. Recently, some have challenged the assertion of the
existence of the HCB, attributing the anisotropy to sky exposure effects. It
has never been explained why the original methods purporting the existence of
the HCB produce anisotropies, even if sky-exposure effects are taken into
account. In this paper, I apply the methods of the original papers purporting
the existence of the HCB in various Monte-Carlo simulations that assume
isotropy to analyze the empirical meaning of the significance levels of the
original tests used. I find that, although the statistical tests at first
glance show significant anisotropies present in the suspect sample, Monte-Carlo
simulations can easily reproduce the sample in most cases, and if not, the
differences can be accounted for by other statistical considerations. An
updated sample raises the probability of drawing the observed clustering from
an isotropic sample ten-fold in some cases. Thus the statistical tests used in
prior studies overestimate the significance of the observed anisotropy, and an
updated sample returns even less significant probabilities. Given the ability
to reproduce the observed anisotropy in Monte-Carlo simulations, the new,
higher probabilities of being drawn from isotropy for an updated sample, and
the work of previous papers attributing anisotropies to sky-selection effects,
the existence of the HCB must be treated as doubtful at best. | G-Bounce Inflation: Towards Nonsingular Inflation Cosmology with
Galileon Field: We study a nonsingular bounce inflation model, which can drive the early
universe from a contracting phase, bounce into an ordinary inflationary phase,
followed by the reheating process. Besides the bounce that avoided the Big-Bang
singularity which appears in the standard cosmological scenario, we make use of
the Horndesky theory and design the kinetic and potential forms of the
lagrangian, so that neither of the two big problems in bouncing cosmology,
namely the ghost and the anisotropy problems, will appear. The cosmological
perturbations can be generated either in the contracting phase or in the
inflationary phase, where in the latter the power spectrum will be
scale-invariant and fit the observational data, while in the former the
perturbations will have nontrivial features that will be tested by the large
scale structure experiments. We also fit our model to the CMB TT power
spectrum. |
Stellar population models at high spectral resolution: We present new, high-to-intermediate spectral resolution stellar population
models, based on four popular libraries of empirical stellar spectra, namely
Pickles, ELODIE, STELIB and MILES. These new models are the same as our
previous models, but with higher resolution and based on empirical stellar
spectra, while keeping other ingredients the same including the stellar
energetics, the atmospheric parameters and the treatment of the
Thermally-Pulsating Asymptotic Giant Branch and the Horizontal Branch
morphology. We further compute very high resolution (R=20,000) models based on
the theoretical stellar library MARCS which extends to the near-infrared. We
therefore provide merged high resolution stellar population models, extending
from ~1000 AA to 25,000 AA. We compare how these libraries perform in stellar
population models and highlight spectral regions where discrepancies are found.
We confirm our previous findings that the flux around the V-band is lower (in a
normalised sense) in models based on empirical libraries than in those based on
the BaSeL-Kurucz library, which results in a bluer B-V colour. Most noticeably
the theoretical library MARCS gives results fully consistent with the empirical
libraries. This same effect is also found in other models using MILES, namely
Vazdekis et al. and Conroy & Gunn, even though the latter authors reach the
opposite conclusion. The bluer predicted B-V colour (by 0.05 magnitudes in our
models) is in better agreement with both the colours of Luminous Red Galaxies
and globular cluster data. We test the models on their ability to reproduce,
through full spectral fitting, the ages and metallicities of galactic globular
clusters as derived from CMD fitting and find overall good agreement.
{Abridged} | Connecting early and late epochs by f(z)CDM cosmography: The cosmographic approach is gaining considerable interest as a
model-independent technique able to describe the late expansion of the
universe. Indeed, given only the observational assumption of the cosmological
principle, it allows to study the today observed accelerated evolution of the
Hubble flow without assuming specific cosmological models. In general,
cosmography is used to reconstruct the Hubble parameter as a function of the
redshift, assuming an arbitrary fiducial value for the current matter density,
$\Omega_m$, and analysing low redshift cosmological data. Here we propose a
different strategy, linking together the parametric cosmographic behavior of
the late universe expansion with the small scale universe. In this way, we do
not need to assume any "a priori" values for the cosmological parameters, since
these are constrained at early epochs using both the Cosmic Microwave
Background Radiation (CMBR) and Baryonic Acoustic Oscillation (BAO) data. In
order to test this strategy, we describe the late expansion of the universe
using the Pad\'e polynomials. This approach is discussed in the light of the
recent $H(z)$ values indicators, combined with Supernovae Pantheon sample,
galaxy clustering and early universe data, as CMBR and BAO. We found an
interesting dependence of the current matter density value with cosmographic
parameters, proving the inaccuracy of setting the value of $\Omega_m$ in
cosmographic analyses, and a non-negligible effect of the cosmographic
parameters on the CMBR temperature anisotropy power spectrum. Finally, we found
that the cosmographic series, truncated at third order, shows a better $\chi^2$
best fit value then the vanilla $\Lambda$CDM model. This can be interpreted as
the requirement that higher order corrections have to be considered to
correctly describe low redshift data and remove the degeneration of the models. |
Reheating in Gauss-Bonnet-coupled inflation: We investigate the feasibility of models of inflation with a large
Gauss-Bonnet coupling at late times, which have been shown to modify and
prevent the end of inflation. Despite the potential of Gauss-Bonnet models in
predicting favourable power spectra, capable of greatly lowering the
tensor-to-scalar-ratio compared to now-disfavoured models of standard chaotic
inflation, it is important to also understand in what context it is possible
for post-inflationary (p)reheating to proceed and hence recover an acceptable
late-time cosmology. We argue that in the previously-studied inverse power law
coupling case, reheating cannot happen due to a lack of oscillatory solutions
for the inflaton, and that neither instant preheating nor gravitational
particle production would avoid this problem due to the persistence of the
inflaton's energy density, even if it were to partially decay. Hence we proceed
to define a minimal generalisation of the model which can permit perturbative
reheating and study the consequences of this, including heavily modified
dynamics during reheating and predictions of the power spectra. | Evidence of an interaction from resolved stellar populations: The
curious case of NGC1313: The galaxy NGC1313 has attracted the attention of various studies due to the
peculiar morphology observed in optical bands, although it is classified as a
barred, late-type galaxy with no apparent close-by companions. However, the
velocity field suggests an interaction with a satellite companion. Using
resolved stellar populations, we study different parts of the galaxy to
understand further its morphology. Based on HST/ACS images, we estimated star
formation histories by means of the synthetic CMD method in different areas in
the galaxy. Incompleteness limits our analysis to ages younger than ~100Myr.
Stars in the red and blue He burning phases are used to trace the distribution
of recent star formation. Star formation histories suggest a burst in the
southern-west region. We support the idea that NGC1313 is experiencing an
interaction with a satellite companion, observed as a tidally disrupted
satellite galaxy in the south-west of NGC1313. However, we do not observe any
indication of a perturbation due to the interaction with the satellite galaxy
at other locations across the galaxy, suggesting that only a modest-sized
companion that did not trigger a global starburst was involved. |
On Decoupling the Integrals of Cosmological Perturbation Theory: Perturbation theory (PT) is often used to model statistical observables
capturing the translation and rotation-invariant information in cosmological
density fields. PT produces higher-order corrections by integration over linear
statistics of the density fields weighted by kernels resulting from recursive
solution of the fluid equations. These integrals quickly become
high-dimensional and naively require increasing computational resources the
higher the order of the corrections. Here we show how to decouple the
integrands that often produce this issue, enabling PT corrections to be
computed as a sum of products of independent 1-D integrals. Our approach is
related to a commonly used method for calculating multi-loop Feynman integrals
in Quantum Field Theory, the Gegenbauer Polynomial $x$-Space Technique (GPxT).
We explicitly reduce the three terms entering the 2-loop power spectrum,
formally requiring 9-D integrations, to sums over successive 1-D radial
integrals. These 1-D integrals can further be performed as convolutions,
rendering the scaling of this method $N_{\rm g} \log N_{\rm g}$ with $N_{\rm
g}$ the number of grid points used for each Fast Fourier Transform. This method
should be highly enabling for upcoming large-scale structure redshift surveys
where model predictions at an enormous number of cosmological parameter
combinations will be required by Monte Carlo Markov Chain searches for the
best-fit values. | Dwarf Galaxies with Optical Signatures of Active Massive Black Holes: We present a sample of 151 dwarf galaxies (10^8.5 < M_stellar < 10^9.5 Msun)
that exhibit optical spectroscopic signatures of accreting massive black holes
(BHs), increasing the number of known active galaxies in this stellar mass
range by more than an order of magnitude. Utilizing data from the Sloan Digital
Sky Survey Data Release 8 and stellar masses from the NASA-Sloan Atlas, we have
systematically searched for active BHs in ~25,000 emission-line galaxies with
stellar masses comparable to the Magellanic Clouds and redshifts z<0.055. Using
the narrow-line [OIII]/H-beta versus [NII]/H-alpha diagnostic diagram, we find
photoionization signatures of BH accretion in 136 galaxies, a small fraction of
which also exhibit broad H-alpha emission. For these broad-line AGN candidates,
we estimate BH masses using standard virial techniques and find a range of 10^5
< M_BH < 10^6 Msun and a median of M_BH ~ 2 x 10^5 Msun. We also detect broad
H-alpha in 15 galaxies that have narrow-line ratios consistent with
star-forming galaxies. Follow-up observations are required to determine if
these are true type 1 AGN or if the broad H-alpha is from stellar processes.
The median absolute magnitude of the host galaxies in our active sample is Mg =
-18.1 mag, which is ~1-2 magnitudes fainter than previous samples of AGN hosts
with low-mass BHs. This work constrains the smallest galaxies that can form a
massive BH, with implications for BH feedback in low-mass galaxies and the
origin of the first supermassive BH seeds. |
Improved EDELWEISS-III sensitivity for low-mass WIMPs using a profile
likelihood approach: We report on a dark matter search for a Weakly Interacting Massive Particle
(WIMP) in the mass range $m_\chi \in [4, 30]\,\mathrm{GeV}/c^2$ with the
EDELWEISS-III experiment. A 2D profile likelihood analysis is performed on data
from eight selected detectors with the lowest energy thresholds leading to a
combined fiducial exposure of 496 kg-days. External backgrounds from $\gamma$-
and $\beta$-radiation, recoils from $^{206}$Pb and neutrons as well as detector
intrinsic backgrounds were modelled from data outside the region of interest
and constrained in the analysis. The basic data selection and most of the
background models are the same as those used in a previously published analysis
based on Boosted Decision Trees (BDT). For the likelihood approach applied in
the analysis presented here, a larger signal efficiency and a subtraction of
the expected background lead to a higher sensitivity, especially for the lowest
WIMP masses probed. No statistically significant signal was found and upper
limits on the spin-independent WIMP-nucleon scattering cross section can be set
with a hypothesis test based on the profile likelihood test statistics. The 90%
C.L. exclusion limit set for WIMPs with $m_\chi = 4\,\mathrm{GeV/}c^2$ is $1.6
\times 10^{-39}\,\mathrm{cm^2}$, which is an improvement of a factor of seven
with respect to the BDT-based analysis. For WIMP masses above
$15\,\mathrm{GeV/}c^2$ the exclusion limits found with both analyses are in
good agreement. | A PDF PSA, or Never gonna set_xscale again -- guilty feats with
logarithms: In the course of doing astronomy, one often encounters plots of densities,
for example probability densities, flux densities, and mass functions. Quite
frequently the ordinate of these diagrams is plotted logarithmically to
accommodate a large dynamic range. In this situation, I argue that it is
critical to adjust the density appropriately, rather than simply setting the
x-scale to `log' in your favorite plotting code. I will demonstrate the basic
issue with a pedagogical example, then mention a few common plots where this
may arise, and finally some possible exceptions to the rule. |
Consistency of the local Hubble constant with the cosmic microwave
background: A significant tension has become manifest between the current expansion rate
of our Universe measured from the cosmic microwave background by the Planck
satellite and from local distance probes, which has prompted for
interpretations of that as evidence of new physics. Within conventional
cosmology a likely source of this discrepancy is identified here as a matter
density fluctuation around the cosmic average of the 40 Mpc environment in
which the calibration of Supernovae Type Ia separations with Cepheids and
nearby absolute distance anchors is performed. Inhomogeneities on this scale
easily reach 40% and more. In that context, the discrepant expansion rates
serve as evidence of residing in an underdense region of $\delta_{\rm
env}\approx-0.5\pm0.1$. The probability for finding this local expansion rate
given the Planck data lies at the 95% confidence level. Likewise, a
hypothetical equivalent local data set with mean expansion rate equal to that
of Planck, while statistically favoured, would not gain strong preference over
the actual data in the respective Bayes factor. These results therefore suggest
borderline consistency between the local and Planck measurements of the Hubble
constant. Generally accounting for the environmental uncertainty, the local
measurement may be reinterpreted as a constraint on the cosmological Hubble
constant of $H_0=74.7^{+5.8}_{-4.2}$ km/s/Mpc. The current simplified analysis
may be augmented with the employment of the full available data sets, an impact
study for the immediate $\lesssim10$ Mpc environment of the distance anchors,
more prone to inhomogeneities, as well as expansion rates measured by quasar
lensing, gravitational waves, currently limited to the same 40 Mpc region, and
local galaxy distributions. | How accurately can we measure the hydrogen 2S->1S transition rate from
the cosmological data?: Recent progress in observational cosmology, and especially the forthcoming
PLANCK mission data, open new directions in so-called precision cosmology. In
this paper we illustrate this statement considering the accuracy of
cosmological determination of the two-quanta decay rate of 2s hydrogen atom
state. We show that the PLANCK data will allow us to measure this decay rate
significantly better than in the laboratory experiments. |
The Physical Conditions of the Intrinsic N V Narrow Absorption Line
Systems of Three Quasars: We employ detailed photoionization models to infer the physical conditions of
intrinsic narrow absorption line systems found in high resolution spectra of
three quasars at z=2.6-3.0. We focus on a family of intrinsic absorbers
characterized by N V lines that are strong relative to the Ly-alpha lines. The
inferred physical conditions are similar for the three intrinsic N V absorbers,
with metallicities greater than 10 times the solar value (assuming a solar
abundance pattern), and with high ionization parameters (log U ~ 0). Thus, we
conclude that the unusual strength of the N V lines results from a combination
of partial coverage, a high ionization state, and high metallicity. We consider
whether dilution of the absorption lines by flux from the broad-emission line
region can lead us to overestimate the metallicities and we find that this is
an unlikely possibility. The high abundances that we infer are not surprising
in the context of scenarios in which metal enrichment takes place very early on
in massive galaxies. We estimate that the mass outflow rate in the absorbing
gas (which is likely to have a filamentary structure) is less than a few solar
masses per year under the most optimistic assumptions, although it may be
embedded in a much hotter, more massive outflow. | The VLT-FLAMES Tarantula Survey: The Tarantula Survey is an ambitious ESO Large Programme that has obtained
multi-epoch spectroscopy of over 1,000 massive stars in the 30 Doradus region
of the Large Magellanic Cloud. Here we introduce the scientific motivations of
the survey and give an overview of the observational sample. Ultimately,
quantitative analysis of every star, paying particular attention to the effects
of rotational mixing and binarity, will be used to address fundamental
questions in both stellar and cluster evolution. |
The impact of cosmic variance on simulating weak lensing surveys: Upcoming weak lensing surveys will survey large cosmological volumes to
measure the growth of cosmological structure with time and thereby constrain
dark energy. One major systematic uncertainty in this process is the
calibration of the weak lensing shape distortions, or shears. Most upcoming
surveys plan to test several aspects of their shear estimation algorithms using
sophisticated image simulations that include realistic galaxy populations based
on high-resolution data from the Hubble Space Telescope (HST). However,
existing datasets from the (HST) cover very small cosmological volumes, so
cosmic variance could cause the galaxy populations in them to be atypical. A
narrow redshift slice from such surveys could be dominated by a single large
overdensity or underdensity. In that case, the morphology-density relation
could alter the local galaxy populations and yield an incorrect calibration of
shear estimates as a function of redshift. We directly test this scenario using
the COSMOS survey, the largest-area (HST) survey to date, and show how the
statistical distributions of galaxy shapes and morphological parameters (e.g.,
S\'{e}rsic $n$) are influenced by redshift-dependent cosmic variance. The
typical variation in RMS ellipticity due to environmental effects is 5 per cent
(absolute, not relative) for redshift bins of width $\Delta z=0.05$, which
could result in uncertain shear calibration at the 1 per cent level. We
conclude that the cosmic variance effects are large enough to exceed the
systematic error budget of future surveys, but can be mitigated with careful
choice of training dataset and sufficiently large redshift binning. | Detectability and parameter estimation of stellar origin black hole
binaries with next generation gravitational wave detectors: We consider stellar-origin black hole binaries, which are among the main
astrophysical sources for next generation gravitational wave (GW) detectors
such as the Einstein Telescope (ET) and Cosmic Explorer (CE). Using population
models calibrated with the most recent LIGO/Virgo results from O3b run, we show
that ET and CE will be capable of detecting tens of thousands of such sources
(and virtually all of those present in our past light cone up to $z\lesssim
0.7$ for ET and $z\lesssim 1$ for CE) with a signal-to-noise ratio up to
several hundreds, irrespective of the detector design. When it comes to
parameter estimation, we use a Fisher-matrix analysis to assess the impact of
the design on the estimation of the intrinsic and extrinsic parameters. We find
that the CE detector, consisting of two distinct $L-$shape interferometers, has
better sky localization performance compared to ET in its triangular
configuration. We also find that the network is typically capable of measuring
the chirp mass, symmetric mass ratio and spins of the binary at order of
$10^{-5}$, $10^{-4}$ and $10^{-4}$ fractional error respectively. While the
fractional errors for the extrinsic parameters are of order $10^{-2}$ for the
sky localization, luminosity distance and inclination. |
Optical dropout galaxies lensed by the cluster A2667: We investigate the nature and the physical properties of z, Y and J-dropout
galaxies selected behind the lensing cluster A2667. This field is part of our
project aimed at identifying z~7-10 candidates accessible to spectroscopic
studies, based on deep photometry with ESO/VLT HAWK-I and FORS2 (zYJH and
Ks-band images, AB(3 sigma)~26-27) on a sample of lensing clusters extracted
from our multi-wavelength combined surveys with SPITZER, HST, and Herschel. In
this paper we focus on the complete Y and J-dropout sample, as well as the
bright z-dropouts fulfilling the selection criteria by Capak et al. (2011). 10
candidates are selected within the common field of ~33 arcmin2 (effective area
once corrected for contamination and lensing dilution). All of them are
detected in H and Ks bands in addition to J and/or IRAC 3.6/4.5, with
H(AB)~23.4 to 25.2, and have modest magnification factors. Although best-fit
photometric redshifts place all these candidates at high-z, the contamination
by low-z interlopers is estimated at 50-75% level based on previous studies,
and the comparison with the blank-field WIRCAM Ultra-Deep Survey (WUDS). The
same result is obtained when photometric redshifts include a luminosity prior,
allowing us to remove half of the original sample as likely z~1.7-3 interlopers
with young stellar pulations and strong extinction. Two additional sources
among the remaining sample could be identified at low-z based on a detection at
24 microns and on the HST z_850 band. These low-z interlopers are not well
described by current templates given the large break, and cannot be easily
identified based solely on optical and near-IR photometry. Given the estimated
dust extinction and high SFRs, some of them could be also detected in the IR or
sub-mm bands. After correction for likely contaminants, the observed counts at
z>7.5 seem to be in agreement with an evolving LF. (abridged) | Topology of neutral hydrogen distribution with the Square Kilometer
Array: Morphology of the complex HI gas distribution can be quantified by statistics
like the Minkowski functionals, and can provide a way to statistically study
the large scale structure in the HI maps both at low redshifts, and during the
epoch of reionization (EoR). At low redshifts, the 21cm emission traces the
underlying matter distribution. Topology of the HI gas distribution, as
measured by the genus, could be used as a "standard ruler". This enables the
determination of distance-redshift relation and also the discrimination of
various models of dark energy and of modified gravity. The topological analysis
is also sensitive to certain primordial non-Gaussian features. Compared with
two-point statistics, the topological statistics are more robust against the
nonlinear gravitational evolution, bias, and redshift-space distortion. The HI
intensity map observation naturally avoids the sparse sampling distortion,
which is an important systematic in optical galaxy survey. The large cosmic
volume accessible to SKA would provide unprecedented accuracy using such a
measurement... [abridged] |
White dwarfs as a probe of dark energy: We investigate the radial density distribution of the dynamical dark energy
inside the white dwarfs (WDs) and its possible impact on their intrinsic
structure. The minimally-coupled dark energy with barotropic equation of state
which has three free parameters (density, equation of state and effective sound
speed) is used. We analyse how such dark energy affects the mass-radius
relation for the WDs because of its contribution to the joint gravitational
potential of the system. For this we use Chandrasekhar model of the WDs, where
model parameters are the parameter of the chemical composition and the
relativistic parameter. To evaluate the dark energy distribution inside a WD we
solve the conservation equation in the spherical static metric. Obtained
distribution is used to find the parameters of dark energy for which the
deviation from the Chandrasekhar model mass-radius relation become
non-negligible. We conclude also, that the absence of observational evidence
for existence of WDs with untypical intrinsic structure (mass-radius relation)
gives us lower limit for the value of effective sound speed of dark energy
$c_s^2 \gtrsim 10^{-4}$ (in units of speed of light). | Fundamental parameters of FR II radio galaxies and their impact on
groups and clusters' environments: Radio galaxies are among the largest and most powerful single objects known
and are found at variety of redshifts, hence they are believed to have had a
significant impact on the evolving Universe. Their relativistic jets inject
considerable amounts of energy into the environments in which the sources
reside; thus the knowledge of the fundamental properties (such as kinetic
luminosities, lifetimes and ambient gas densities) of these sources is crucial
for understanding AGN feedback in galaxy clusters. In this work, we explore the
intrinsic and extrinsic fundamental properties of Fanaroff-Riley II (FR II)
objects through the construction of multidimensional Monte Carlo simulations
which use complete, flux limited radio catalogues and semi-analytical models of
FR IIs' time evolution to create artificial samples of radio galaxies. This
method allows us to set better limits on the confidence intervals of the
intrinsic and extrinsic fundamental parameters and to investigate the total
energy produced and injected to the clusters' environments by populations of FR
IIs at various cosmological epochs (0.0<z<2.0). We find the latter estimates to
be strikingly robust despite the strong degeneracy between the fundamental
parameters -- such a result points to a conclusive indicator of the scale of
AGN feedback in clusters of galaxies. |
Multiwavelength observations of 3C 454.3 II. The AGILE 2007 December
campaign: We report on the second AGILE multiwavelength campaign of the blazar 3C 454.3
during the first half of December 2007. This campaign involved AGILE, Spitzer,
Swift,Suzaku,the WEBT consortium,the REM and MITSuME telescopes,offering a
broad band coverage that allowed for a simultaneous sampling of the synchrotron
and inverse Compton (IC) emissions.The 2-week AGILE monitoring was accompanied
by radio to optical monitoring by WEBT and REM and by sparse observations in
mid-Infrared and soft/hard X-ray energy bands performed by means of Target of
Opportunity observations by Spitzer, Swift and Suzaku, respectively.The source
was detected with an average flux of~250x10^{-8}ph cm^-2s^-1 above 100
MeV,typical of its flaring states.The simultaneous optical and gamma-ray
monitoring allowed us to study the time-lag associated with the variability in
the two energy bands, resulting in a possible ~1-day delay of the gamma-ray
emission with respect to the optical one. From the simultaneous optical and
gamma-ray fast flare detected on December 12, we can constrain the delay
between the gamma-ray and optical emissions within 12 hours. Moreover, we
obtain three Spectral Energy Distributions (SEDs) with simultaneous data for
2007 December 5, 13, 15, characterized by the widest multifrequency coverage.
We found that a model with an external Compton on seed photons by a standard
disk and reprocessed by the Broad Line Regions does not describe in a
satisfactory way the SEDs of 2007 December 5, 13 and 15. An additional
contribution, possibly from the hot corona with T=10^6 K surrounding the jet,
is required to account simultaneously for the softness of the synchrotron and
the hardness of the inverse Compton emissions during those epochs. | L-PICOLA: A parallel code for fast dark matter simulation: Robust measurements based on current large-scale structure surveys require
precise knowledge of statistical and systematic errors. This can be obtained
from large numbers of realistic mock galaxy catalogues that mimic the observed
distribution of galaxies within the survey volume. To this end we present a
fast, distributed-memory, planar-parallel code, L-PICOLA, which can be used to
generate and evolve a set of initial conditions into a dark matter field much
faster than a full non-linear N-Body simulation. Additionally, L-PICOLA has the
ability to include primordial non-Gaussianity in the simulation and simulate
the past lightcone at run-time, with optional replication of the simulation
volume. Through comparisons to fully non-linear N-Body simulations we find that
our code can reproduce the $z=0$ power spectrum and reduced bispectrum of dark
matter to within 2% and 5% respectively on all scales of interest to
measurements of Baryon Acoustic Oscillations and Redshift Space Distortions,
but 3 orders of magnitude faster. The accuracy, speed and scalability of this
code, alongside the additional features we have implemented, make it extremely
useful for both current and next generation large-scale structure surveys.
L-PICOLA is publicly available at https://cullanhowlett.github.io/l-picola |
A New Era in Extragalactic Background Light Measurements: The Cosmic
History of Accretion, Nucleosynthesis and Reionization: (Brief Summary) What is the total radiative content of the Universe since the
epoch of recombination? The extragalactic background light (EBL) spectrum
captures the redshifted energy released from the first stellar objects,
protogalaxies, and galaxies throughout cosmic history. Yet, we have not
determined the brightness of the extragalactic sky from UV/optical to
far-infrared wavelengths with sufficient accuracy to establish the radiative
content of the Universe to better than an order of magnitude. Among many
science topics, an accurate measurement of the EBL spectrum from optical to
far-IR wavelengths, will address: What is the total energy released by stellar
nucleosynthesis over cosmic history? Was significant energy released by
non-stellar processes? Is there a diffuse component to the EBL anywhere from
optical to sub-millimeter? When did first stars appear and how luminous was the
reionization epoch? Absolute optical to mid-IR EBL spectrum to an
astrophysically interesting accuracy can be established by wide field imagingat
a distance of 5 AU or above the ecliptic plane where the zodiacal foreground is
reduced by more than two orders of magnitude. | Annual Modulation in Direct Dark Matter Searches: The measurement of an annual modulation in the event rate of direct dark
matter detection experiments is a powerful tool for dark matter discovery.
Indeed, several experiments have already claimed such a discovery in the past
decade. While most of them have later revoked their conclusions, and others
have found potentially contradictory results, one still stands today. This
paper explains the potential as well as the challenges of annual modulation
measurements, and gives an overview of past, present and future direct
detection experiments. |
Signatures of Cool Gas Fueling a Star-Forming Galaxy at Redshift 2.3: Galaxies are thought to be fed by the continuous accretion of intergalactic
gas, but direct observational evidence has been elusive. The accreted gas is
expected to orbit about the galaxy's halo, delivering not just fuel for
star-formation but also angular momentum to the galaxy, leading to distinct
kinematic signatures. Here we report observations showing these distinct
signatures near a typical distant star-forming galaxy where the gas is detected
using a background quasar passing 26 kpc from the host. Our observations
indicate that gas accretion plays a major role in galaxy growth since the
estimated accretion rate is comparable to the star-formation rate. | Euclid preparation: VI. Verifying the Performance of Cosmic Shear
Experiments: Our aim is to quantify the impact of systematic effects on the inference of
cosmological parameters from cosmic shear. We present an end-to-end approach
that introduces sources of bias in a modelled weak lensing survey on a
galaxy-by-galaxy level. Residual biases are propagated through a pipeline from
galaxy properties (one end) through to cosmic shear power spectra and
cosmological parameter estimates (the other end), to quantify how imperfect
knowledge of the pipeline changes the maximum likelihood values of dark energy
parameters. We quantify the impact of an imperfect correction for charge
transfer inefficiency (CTI) and modelling uncertainties of the point spread
function (PSF) for Euclid, and find that the biases introduced can be corrected
to acceptable levels. |
Interpreting the Ionization Sequence in AGN Emission-Line Spectra: We investigate the physical cause of the great range in the ionization level
seen in the spectra of narrow lined active galactic nuclei (AGN). Mean field
independent component analysis identifies examples of individual SDSS galaxies
whose spectra are not dominated by emission due to star formation (SF), which
we designate as AGN. We assembled high S/N ratio composite spectra of a
sequence of these AGN defined by the ionization level of their narrow-line
regions (NLR), extending down to very low-ionization cases. We used a local
optimally emitting cloud (LOC) model to fit emission-line ratios in this AGN
sequence. These included the weak lines that can be measured only in the
co-added spectra, providing consistency checks on strong line diagnostics.
After integrating over a wide range of radii and densities our models indicate
that the radial extent of the NLR is the major parameter in determining the
position of high to moderate ionization AGN along our sequence, providing a
physical interpretation for their systematic variation. Higher ionization AGN
contain optimally emitting clouds that are more concentrated towards the
central continuum source than in lower ionization AGN. Our LOC models indicate
that for the objects that lie on our AGN sequence, the ionizing luminosity is
anticorrelated with the NLR ionization level, and hence anticorrelated with the
radial concentration and physical extent of the NLR. A possible interpretation
that deserves further exploration is that the ionization sequence might be an
age sequence where low ionization objects are older and have systematically
cleared out their central regions by radiation pressure. We consider that our
AGN sequence instead represents a mixing curve of SF and AGN spectra, but argue
that while many galaxies do have this type of composite spectra, our AGN
sequence appears to be a special set of objects with negligible SF excitation. | The statistical nature of the brightest group galaxies: We examine the statistical properties of the brightest group galaxies (BGGs)
using a complete spectroscopic sample of groups/clusters of galaxies selected
from the Data Release 7 of the Sloan Digital Sky Survey. We test whether BGGs
and other bright members of groups are consistent with an ordered population
among the total population of group galaxies. We find that the luminosity
distributions of BGGs do not follow the predictions from the order statistics
(OS). The average luminosities of BGGs are systematically brighter than OS
predictions. On the other hand, by properly taking into account the brightening
effect of the BGGs, the luminosity distributions of the second brightest
galaxies are in excellent agreement with the expectations of OS. The
brightening of BGGs relative to the OS expectation is consistent with a
scenario that the BGGs on average have over-grown about 20 percent masses
relative to the other member galaxies. The growth ($\Delta M$) is not
stochastic but correlated with the magnitude gap ($G_{1,2}$) between the
brightest and the second brightest galaxy. The growth ($\Delta M$) is larger
for the groups having more prominent BGGs (larger $G_{1,2}$) and averagely
contributes about 30 percent of the final $G_{1,2}$ of the groups of galaxies. |
Calculated WIMP signals at the ANDES laboratory: comparison with
northern and southern located dark matter detectors: Weakly Interacting Massive Particles (WIMP) are possible components of the
Universe's Dark Matter. The detection of WIMP is signalled by the recoil of the
atomic nuclei which form a detector. CoGeNT at the Soudan Underground
Laboratory (SUL) and DAMA at the Laboratori Nazionali del Gran Sasso (LNGS)
have reported data on annual modulation of signals attributed to WIMP. Both
experiments are located in laboratories of the northern hemisphere. Dark matter
detectors are planned to operate (or already operate) in laboratories of the
southern hemisphere, like SABRE at Stawell Underground Physics Laboratory
(SUPL) in Australia, and DM-ICE in the South Pole. In this work we have
analysed the dependence of diurnal and annual modulation of signals, pertaining
to the detection of WIMP, on the coordinates of the laboratory, for experiments
which may be performed in the planned new underground facility ANDES (Agua
Negra Deep Experimental Site), to be built in San Juan, Argentina. We made
predictions for NaI and Ge-type detectors placed in ANDES, to compare with
DAMA, CoGeNT, SABRE and DM-ICE arrays, and found that the diurnal modulation of
the signals, at the site of ANDES, is amplified at its maximum value, both for
NaI (Ge)-type detectors, while the annual modulation remains unaffected by the
change in coordinates from north to south. | Multi-wavelength study of X-ray luminous clusters at z ~ 0.3 I. Star
formation activity of cluster galaxies: The current paradigm of cosmic formation and evolution of galaxy clusters
foresees growth mostly through merging. Galaxies in the infall region or in the
core of a cluster undergo transformations owing to different environmental
stresses. For two X-ray luminous clusters at redshift z ~ 0.3 with opposite
X-ray morphologies, RXCJ0014.3-3022 and RXCJ2308.3-0211, we assess differences
in galaxy populations as a function of cluster topography. Cluster large-scale
structure and substructure are determined from the combined photometry in the
B, V, and R bands, and from multi-object optical spectroscopy at low
resolution. A spectral index analysis is performed, based on the [OII] and
Hdelta features, and the D4000 break, available for more than 100 member
galaxies per cluster. Combination of spectral indices and FUV-optical colours
provides a picture of the star formation history in galaxies. In spite of the
potential presence of a small fraction of galaxies with obscured star formation
activity, the average star-formation history of cluster members is found to
depend on cluster-centric distance and on substructure. There is a sharp
increase in star formation activity along two well-defined filamentary
structures of the merging cluster RXCJ0014.3-3022, out to its virial radius and
beyond, produced by luminous (L ~ L*) and sub-L* galaxies. Conversely, the
regular cool-core cluster RXCJ2308.3-0211 mostly hosts galaxies which either
populate the red sequence or are becoming passive. These results suggest the
existence of a correspondence between assembly state and overall age of the
stellar populations of galaxies inside the virialized region and in the
surrounding large scale structure of massive clusters at z ~ 0.3. (Abridged) |
Precision Prediction of the Log Power Spectrum: At translinear scales, the log power spectrum captures significantly more
cosmological information than the standard power spectrum. At high wavenumbers
$k$, the Fisher information in the standard power spectrum $P(k)$ fails to
increase in proportion to $k$ in part due to correlations between large- and
small-scale modes. As a result, $P(k)$ suffers from an information plateau on
these translinear scales, so that analysis with the standard power spectrum
cannot access the information contained in these small-scale modes. The log
power spectrum $P_A(k)$, on the other hand, captures the majority of this
otherwise lost information. Until now there has been no means of predicting the
amplitude of the log power spectrum apart from cataloging the results of
simulations. We here present a cosmology-independent prescription for the log
power spectrum; this prescription displays accuracy comparable to that of Smith
et al. (2003), over a range of redshifts and smoothing scales, and for
wavenumbers up to $1.5h$ Mpc$^{-1}$. | Frequent Spin Reorientation of Galaxies due to Local Interactions: We study the evolution of angular momenta of ($M_*=10^{10}-10^{12}\msun$)
galaxies utilizing large-scale ultra-high resolution cosmological hydrodynamic
simulations and find that spin of the stellar component changes direction
frequently, caused by major mergers, minor mergers, significant gas inflows and
torques by nearby systems. The rate and nature of change of spin direction can
not be accounted for by large-scale tidal torques, because the latter fall
short in rates by orders of magnitude and because the apparent random swings of
the spin direction are inconsistent with alignment by linear density field. The
implications for galaxy formation as well as intrinsic alignment of galaxies
are profound. Assuming the large-scale tidal field is the sole alignment agent,
a new picture emerging is that intrinsic alignment of galaxies would be a
balance between slow large-scale coherent torquing and fast spin reorientation
by local interactions. What is still open is whether other processes, such as
feeding galaxies with gas and stars along filaments or sheets, introduce
coherence for spin directions of galaxies along the respective structures. |
A Strong Dichotomy in S0 Disk Profiles Between the Virgo Cluster and the
Field: We report evidence for a striking difference between S0 galaxies in the local
field and in the Virgo Cluster. While field S0 galaxies have disks whose
surface-brightness profiles are roughly equally divided between the three main
types (Types I, II, and III: single-exponential, truncated, and antitruncated),
Virgo S0s appear to be entirely lacking in disk truncations. More specifically,
the fraction of truncations in S0 galaxies with M_B < -17 is 28% +7/-6% for the
field, versus 0% +4/-0% for the Virgo Cluster galaxies; the difference is
significant at the 99.7% level. The discrepancy is made up almost entirely by
Type I profiles, which are almost twice as frequent in the Virgo Cluster as
they are in the field.
This suggests that S0 formation may be driven by different processes in
cluster and field environments, and that outer-disk effects can be useful tests
of S0 formation models. | Equivalence of the Fermat potential and the lensing potential approaches
to computing the integrated Sachs-Wolfe effect: We show in detail that the recently derived expression for evaluating the
integrated Sachs-Wolfe (ISW) temperature shift in the cosmic microwave
background (CMB) caused by individual embedded (compensated) lenses is
equivalent to the conventional approach for flat background cosmologies. The
conventional approach requires evaluating an integral of the time derivative of
the lensing potential, whereas the new Fermat potential approach is simpler and
only requires taking a derivative of the potential part of the time delay. |
Light Curves of 213 Type Ia Supernovae from the ESSENCE Survey: The ESSENCE survey discovered 213 Type Ia supernovae at redshifts 0.1 < z <
0.81 between 2002 and 2008. We present their R and I-band photometry, measured
from images obtained using the MOSAIC II camera at the CTIO 4 m Blanco
telescope, along with rapid-response spectroscopy for each object. We use our
spectroscopic follow-up observations to determine an accurate, quantitative
classification and a precise redshift. Through an extensive calibration program
we have improved the precision of the CTIO Blanco natural photometric system.
We use several empirical metrics to measure our internal photometric
consistency and our absolute calibration of the survey. We assess the effect of
various potential sources of systematic bias on our measured fluxes, and we
estimate that the dominant term in the systematic error budget from the
photometric calibration on our absolute fluxes is ~1%. | Precise determination of the inflationary epoch and constraints for
reheating: We present a simple formula that allows to calculate the value of the
inflaton field, denoted by $\phi$, at the scale with wavenumber mode $k$. In
the extreme case of instantaneous reheating $\phi_k$ is calculated exactly and
all inflationary observables and quantities of interest follow. This formula,
together with the fact that the scale factor $a_p$ at the pivot scale
wavenumber $k_p=0.05/Mpc$ lies in the radiation era, allows the development of
a diagrammatic approach to study the evolution of the universe. This scheme is
complementary to the usual analytical method and some interesting results,
independent of the model of inflation, can be obtained. As a concrete
application of the ideas developed here we discuss them with some detail using
the Starobinsky model of inflation. |
Can the Low Redshift Lyman Alpha Forest Constrain AGN Feedback Models?: We investigate the potential of low-redshift Lyman alpha (Ly$\alpha$) forest
for constraining active galactic nuclei (AGN) feedback models by analyzing the
Illustris and IllustrisTNG simulation at z=0.1. These simulations are ideal for
studying the impact of AGN feedback on the intergalactic medium (IGM) as they
share initial conditions with significant differences in the feedback
prescriptions. Both simulations reveal that the IGM is significantly impacted
by AGN feedback. Specifically, feedback is stronger in Illustris and results in
reducing cool baryon fraction to 23% relative to 39% in IllustrisTNG. However,
when comparing various statistics of Ly$\alpha$ forest such as 2D and
marginalized distributions of Doppler widths and H I column density, line
density, and flux power spectrum with real data, we find that most of these
statistics are largely insensitive to the differences in feedback models. This
lack of sensitivity arises because of the fundamental degeneracy between the
fraction of cool baryons and the H I photoionization rate ($\Gamma_{\rm HI}$)
as their product determines the optical depth of the Ly$\alpha$ forest. Since
the $\Gamma_{\rm HI}$ cannot be precisely predicted from first principles, it
needs to be treated as a nuisance parameter adjusted to match the observed
Ly$\alpha$ line density. After adjusting $\Gamma_{\rm HI}$, the distinctions in
the considered statistics essentially fade away. Only the Ly$\alpha$ flux power
spectrum at small spatial scales exhibits potentially observable differences,
although this may be specific to the relatively extreme feedback model employed
in Illustris. Without independent constraints on either $\Gamma_{\rm HI}$ or
cool baryon fraction, constraining AGN feedback with low-redshift Ly$\alpha$
forest will be very challenging. | Measurements of B-mode Polarization of the Cosmic Microwave Background
from 500 Square Degrees of SPTpol Data: We report a B-mode power spectrum measurement from the cosmic microwave
background (CMB) polarization anisotropy observations made using the SPTpol
instrument on the South Pole Telescope. This work uses 500 deg$^2$ of SPTpol
data, a five-fold increase over the last SPTpol B-mode release. As a result,
the bandpower uncertainties have been reduced by more than a factor of two, and
the measurement extends to lower multipoles: $52 < \ell < 2301$. Data from both
95 and 150 GHz are used, allowing for three cross-spectra: 95 GHz x 95 GHz, 95
GHz x 150 GHz, and 150 GHz x 150 GHz. B-mode power is detected at very high
significance; we find $P(BB < 0) = 5.8 \times 10^{-71}$, corresponding to a
$18.1 \sigma$ detection of power. An upper limit is set on the tensor-to-scalar
ratio, $r < 0.44$ at 95% confidence (the expected $1 \sigma$ constraint on $r$
given the measurement uncertainties is 0.22). We find the measured B-mode power
is consistent with the Planck best-fit $\Lambda$CDM model predictions. Scaling
the predicted lensing B-mode power in this model by a factor Alens, the data
prefer Alens = $1.17 \pm 0.13$. These data are currently the most precise
measurements of B-mode power at $\ell > 320$. |
Galaxy Group at z=0.3 Associated with the Damped Lyman Alpha System
Towards Quasar Q1127-145: (Abridged) We performed a spectroscopic galaxy survey, complete to m<20.3
(L_B>0.15L_B* at z=0.3), within 100x100" of the quasar Q1127-145 (z=1.18). The
VLT/UVES quasar spectrum contains three z<0.33 MgII absorption systems. We
obtained eight new galaxy redshifts, adding to the four previously known, and
galaxy star formation rates and metallicities were computed where possible. A
strong MgII system [W_r(2796)=1.8A], which is a known DLA, had three previously
identified galaxies; we found two additional galaxies associated with this
system. These five galaxies form a group with diverse properties, such as a
luminosity range of 0.04<L_B<0.63L_B*, an impact parameter range of 17<D<241kpc
and velocity dispersion of 115km/s. The DLA group galaxy redshifts span beyond
the 350km/s velocity spread of the metallic absorption lines of the DLA itself.
The two brightest group galaxies have SFRs of a few Msun/yr and should not have
strong winds. We have sufficient spectroscopic information to directly compare
three of the five group galaxies' (emission-line) metallicities with the DLA
(absorption) metallicity: the DLA metallicity is 1/10th solar, substantially
lower than the three galaxies' which range between less than 1/2 solar to solar
metallicity. HST/WFPC-2 imaging shows perturbed morphologies for the three
brightest group galaxies, with tidal tails extending 25kpc. We favor a scenario
where the DLA absorption originates from tidal debris in the group environment.
Another absorber exhibits weak MgII absorption [W_r(2796)=0.03A] and had a
previously identified galaxy at a similar redshift. We have identified a second
galaxy associated with this system. Both galaxies have solar metallicities and
unperturbed morphologies. The SFR of one galaxy is much lower than expected for
strong outflows. Finally, we have identified five galaxies at large impact
parameters with no associated MgII absorption. | Uncovering Drivers of Disk Assembly: Bulgeless Galaxies and the Stellar
Mass Tully-Fisher Relation: In order to determine what processes govern the assembly history of galaxies
with rotating disks, we examine the stellar mass Tully-Fisher relation over a
wide range in redshift partitioned according to whether or not galaxies contain
a prominent bulge. Using our earlier Keck spectroscopic sample, for which
bulge/total parameters are available from analyses of HST images, we find that
bulgeless disk galaxies with z > 0.8 present a significant offset from the
local Tully-Fisher relation whereas, at all redshifts probed, those with
significant bulges fall along the local relation. Our results support the
suggestion that bulge growth may somehow expedite the maturing of disk galaxies
onto the Tully-Fisher relation. We discuss a variety of physical hypotheses
that may explain this result in the context of kinematic observations of
star-forming galaxies at redshifts z = 0 and z > 2. |
Editorial note to "Large number coincidences and the anthropic principle
in cosmology": This is an editorial note to accompany reprinting as a Golden Oldie in the
Journal of General Relativity and Gravitation of the famous paper by Brandon
Carter on the anthropic principle in cosmology \cite{Car74}. This paper was
presented at IAU Symposium No. 63, entitled Confrontation of cosmological
theories with observational data, in 1973. | Early-type Host Galaxies of Type Ia Supernovae. I. Evidence for
Downsizing: Type Ia supernova (SN Ia) cosmology provides the most direct evidence for the
presence of dark energy. This result is based on the assumption that the
look-back time evolution of SN Ia luminosity, after light-curve corrections,
would be negligible. Recent studies show, however, that the Hubble residual
(HR) of SN Ia is correlated with the mass and morphology of host galaxies,
implying the possible dependence of SN Ia luminosity on host galaxy properties.
In order to investigate this more directly, we have initiated spectroscopic
survey for the early-type host galaxies, for which population age and
metallicity can be more reliably determined from the absorption lines. As the
first paper of the series, here we present the results from high
signal-to-noise ratio (>100 per pixel) spectra for 27 nearby host galaxies in
the southern hemisphere. For the first time in host galaxy studies, we find a
significant (~3.9sigma) correlation between host galaxy mass (velocity
dispersion) and population age, which is consistent with the "downsizing" trend
among non-host early-type galaxies. This result is rather insensitive to the
choice of population synthesis models. Since we find no correlation with
metallicity, our result suggests that stellar population age is mainly
responsible for the relation between host mass and HR. If confirmed, this would
imply that the luminosity evolution plays a major role in the systematic
uncertainties of SN Ia cosmology. |
Testing the nature of Dark Energy with Precision Cosmological
constraints: We present a Dark Energy (DE) model with a sound derivation as a natural
extension of the Standard Model of particle physics with no free parameters and
an excellent fit with current cosmological data improving by 21% the
$\Lambda$CDM fit of the Baryon Acoustic Oscillations (BAO) measurements,
specially designed to determine the dynamics of DE. DE corresponds to the
lightest bound state scalar particle $\phi$ with a potential
$V=\Lambda_c^{4+2/3}\phi^{-2/3}$ dynamically formed at the condensation energy
scale $\Lambda_c$ and scale factor $a_c$. The value of $\Lambda_c$, the
exponent $n=2/3$, and the initial conditions of $\phi$ are all derived
quantities. We obtain an exact constraint
$a_c\Lambda_c/\textrm{eV}=1.0939\times 10^{-4}$ and a theoretical prediction
$\Lambda_c=34 ^{+16}_{-11} \textrm{ eV}$, consistent with the best fit
$\Lambda_c=44.08\pm 0.27 \textrm{ eV}$. We test our model constraint on
$a_c\Lambda_c$ by allowing $a_c$ and $\Lambda_c$ to vary independently and
remarkably our prediction has a relative difference of only 0.2% with the best
fit value. Unlike a cosmological constant $\Lambda$, our DE model predicts the
amount of DE and leaves detectable cosmological imprints at different times and
scales at a background and perturbation level. | Effect of Foregrounds on the CMBR Multipole Alignment: We analyze the effect of foregrounds on the observed alignment of CMBR
quadrupole and octopole. The alignment between these multipoles is studied by
using a symmetry based approach which assigns a principal eigenvector (PEV) or
an axis with each multipole. We determine the significance of alignment between
these multipoles by using the Internal Linear Combination (ILC) 5 and 7 year
map s and also the maps obtained by using the Internal Power Spectrum
Estimation (IPSE) procedure. The effect of foreground cleaning is studied in
detail within the framework of the IPSE method both analytically and
numerically. By using simulated CMBR data, we study how the PEVs of the pure
simulated CMB map differ from those of the final cleaned map. We find that, in
general, the shift in the PEVs is relatively small and in random directions.
Due to the random nature of the shift we conclude that it can only lead to
misalignment rather than alignment of multipoles. We also directly estimate the
significance of alignment by using simulated cleaned maps. We find that the
results in this case are identical to those obtained by simple analytic
estimate or by using simulated pure CMB maps. |
Emergent perspective of Gravity and Dark Energy: There is sufficient amount of internal evidence in the nature of
gravitational theories to indicate that gravity is an emergent phenomenon like,
e.g, elasticity. Such an emergent nature is most apparent in the structure of
gravitational dynamics. It is, however, possible to go beyond the field
equations and study the space itself as emergent in a well-defined manner in
(and possibly only in) the context of cosmology. In the first part of this
review, I describe various pieces of evidence which show that gravitational
field equations are emergent. In the second part, I describe a novel way of
studying cosmology in which I interpret the expansion of the universe as
equivalent to the emergence of space itself. In such an approach, the dynamics
evolves towards a state of holographic equipartition, characterized by the
equality of number of bulk and surface degrees of freedom in a region bounded
by the Hubble radius. This principle correctly reproduces the standard
evolution of a Friedmann universe. Further, (a) it demands the existence of an
early inflationary phase as well as late time acceleration for its successful
implementation and (b) allows us to link the value of late time cosmological
constant to the e-folding factor during inflation. | Interpreting the HI 21-cm cosmology maps through Largest Cluster
Statistics -- I: Impact of the synthetic SKA1-Low observations: We analyse the evolution of the largest ionized region using the topological
and morphological evolution of the redshifted 21-cm signal coming from the
neutral hydrogen distribution during the different stages of reionization. For
this analysis, we use the "Largest Cluster Statistics" - LCS. We mainly study
the impact of the array synthesized beam on the LCS analysis of the 21-cm
signal considering the upcoming low-frequency Square Kilometer Array (SKA1-Low)
observations using a realistic simulation for such observation based on the
21cmE2E-pipeline using OSKAR. We find that bias in LCS estimation is introduced
in synthetic observations due to the array beam. This in turn shifts the
apparent percolation transition point towards the later stages of reionization.
The biased estimates of LCS, occurring due to the effect of the lower
resolution (lack of longer baselines) and the telescope synthesized beam will
lead to a biased interpretation of the reionization history. This is important
to note while interpreting any future 21-cm signal images from upcoming or
future telescopes like the SKA, HERA, etc. We conclude that one may need denser
$uv$-coverage at longer baselines for a better deconvolution of the array
synthesized beam from the 21-cm images and a relatively unbiased estimate of
LCS from such images. |
On the observability of coupled dark energy with cosmic voids: Taking N-body simulations with volumes and particle densities tuned to match
the SDSS DR7 spectroscopic main sample, we assess the ability of current void
catalogs (e.g., Sutter et al. 2012b) to distinguish a model of coupled dark
matter-dark energy from {\Lambda}CDM cosmology using properties of cosmic
voids. Identifying voids with the VIDE toolkit, we find no statistically
significant differences in the ellipticities, but find that coupling produces a
population of significantly larger voids, possibly explaining the recent result
of Tavasoli et al. (2013). In addition, we use the universal density profile of
Hamaus et al. (2014) to quantify the relationship between coupling and density
profile shape, finding that the coupling produces broader, shallower,
undercompensated profiles for large voids by thinning the walls between
adjacent medium-scale voids. We find that these differences are potentially
measurable with existing void catalogs once effects from survey geometries and
peculiar velocities are taken into account. | Neutrino point source searches for dark matter spikes: Any dark matter spikes surrounding black holes in our Galaxy are sites of
significant dark matter annihilation, leading to a potentially detectable
neutrino signal. In this paper we examine $10-10^5 M_\odot$ black holes
associated with dark matter spikes that formed in early minihalos and still
exist in our Milky Way Galaxy today, in light of neutrino data from the ANTARES
and IceCube detectors. In various regions of the sky, we determine the minimum
distance away from the solar system that a dark matter spike must be in order
to have not been detected as a neutrino point source for a variety of
representative dark matter annihilation channels. Given these constraints on
the distribution of dark matter spikes in the Galaxy, we place significant
limits on the formation of the first generation of stars in early minihalos --
stronger than previous limits from gamma-ray searches in Fermi Gamma-Ray Space
Telescope data. The larger black holes considered in this paper may arise as
the remnants of Dark Stars after the dark matter fuel is exhausted; thus
neutrino observations may be used to constrain the properties of Dark Stars.
The limits are particularly strong for heavier WIMPs. For WIMP masses $\sim 5
\,$TeV, we show that $\lesssim 10 \%$ of minihalos can host first stars that
collapse into BHs larger than $10^3 M_\odot$. |
CosmoSIS: modular cosmological parameter estimation: Cosmological parameter estimation is entering a new era. Large collaborations
need to coordinate high-stakes analyses using multiple methods; furthermore
such analyses have grown in complexity due to sophisticated models of cosmology
and systematic uncertainties. In this paper we argue that modularity is the key
to addressing these challenges: calculations should be broken up into
interchangeable modular units with inputs and outputs clearly defined. We
present a new framework for cosmological parameter estimation, CosmoSIS,
designed to connect together, share, and advance development of inference tools
across the community. We describe the modules already available in CosmoSIS,
including CAMB, Planck, cosmic shear calculations, and a suite of samplers. We
illustrate it using demonstration code that you can run out-of-the-box with the
installer available at http://bitbucket.org/joezuntz/cosmosis | Primordial Black Holes in non-linear perturbation theory: This thesis begins with a study of the origin of cosmological fluctuations
with special attention to those cases in which the non-Gaussian correlation
functions are large. The analysis shows that perturbations from an almost
massless auxiliary field generically produce large values of the non-linear
parameter f_NL. The effects of including non-Gaussian correlation functions in
the statistics of cosmological structure are explored by constructing a
non-Gaussian probability distribution function (PDF). Such PDF is derived for
the comoving curvature perturbation from first principles in the context of
quantum field theory, with n-point correlation functions as the only input. The
non-Gaussian PDF is then used to explore two important problems in the physics
of primordial black holes (PBHs): First, to compute non-Gaussian corrections to
the number of PBHs generated from the primordial curvature fluctuations. The
second application concerns new cosmological observables. The formation of PBHs
is known to depend on two main physical characteristics: the strength of the
gravitational field produced by the initial curvature inhomogeneity and the
pressure gradient at the edge of the curvature configuration. We account for
the probability of finding these configurations by using two parameters: The
amplitude of the inhomogeneity and its second radial derivative, evaluated at
the centre of the configuration. The implications of the derived probability
for the fraction of mass in the universe in the form of PBHs are discussed. |
Model-Independent Determination of the Cosmic Growth Factor: Since the discovery of the accelerated cosmic expansion, one of the most
important tasks in observational cosmology is to determine the nature of the
dark energy. We should build our understanding on a minimum of assumptions in
order to avoid biases from assumed cosmological models. The two most important
functions describing the evolution of the universe and its structures are the
expansion function E(a) and the linear growth factor D_+(a). The expansion
function has been determined in previous papers in a model-independent way
using distance moduli to type-Ia supernovae and assuming only a metric theory
of gravity, spatial isotropy and homogeneity. Here, we extend this analysis in
three ways: (1) We extend the data sample by combining the Pantheon
measurements of type-Ia supernovae with measurements of baryonic acoustic
oscillations; (2) we substantially simplify and generalise our method for
reconstructing the expansion function; and (3) we use the reconstructed
expansion function to determine the linear growth factor of cosmic structures,
equally independent of specific assumptions on an underlying cosmological model
other than the usual spatial symmetries. We show that the result is quite
insensitive to the initial conditions for solving the growth equation, leaving
the present-day matter-density parameter {\Omega}_m0 as the only relevant
parameter for an otherwise purely empirical and accurate determination of the
growth factor. | Scalar field descriptions of two dark energy models: We give a scalar field description of two dark energy parameterizations, and
we analyze in detail its cosmology both at the level of background evolution
and at the level of linear perturbations. In particular, we compute the
statefinder parameters and the growth index as functions of the red-shift for
both dark energy parameterizations, and the comparison with the $\Lambda CDM$
model as well as with a few well-known geometrical dark energy models is shown.
In addition, the combination parameter $A=f \sigma_8$ of both models is
compared against current data. |
Comments on Kormendy, Bender & Cornell (2011, Nature, 469, 374): Comments on Kormendy, Bender & Cornell's (2011, Nature, 469, 374) article
"Supermassive black holes do not correlate with galaxy disks or pseudobulges"
are provided. A number of scientific concerns regarding the data analysis and
conclusions are discussed. A broader historical perspective - difficult for
authors to supply within the confines of a Nature article - is also provided. | Dwarf Galaxies in the Coma Cluster: II. Spectroscopic and Photometric
Fundamental Planes: We present a study of the fundamental plane, FP, for a sample of 71 dwarf
galaxies in the core of Coma cluster in magnitude range $-21 < M_I <-15$.
Taking advantage of high resolution DEIMOS spectrograph on Keck II for
measuring the internal velocity dispersion of galaxies and high resolution
imaging of HST/ACS, which allows an accurate surface brightness modeling, we
extend the fundamental plane (FP) of galaxies to $\sim$1 magnitude fainter
luminosities than all the previous studies of the FP in Coma cluster. We find
that, the scatter about the FP depends on the faint-end luminosity cutoff, such
that the scatter increases for fainter galaxies. The residual from the FP
correlates with the galaxy colour, with bluer galaxies showing larger residuals
from FP.
We find $M/L \propto M^{-0.15\pm0.22}$ in F814W-band indicating that in faint
dwarf ellipticals, the $M/L$ ratio is insensitive to the mass. We find that
less massive dwarf ellipticals are bluer than their brighter counterparts,
possibly indicating ongoing star formation activity. Although tidal encounters
and harassment can play a part in removing stars and dark matter from the
galaxy, we believe that the dominant effect will be the stellar wind associated
with the star formation, which will remove material from the galaxy resulting
in larger $M/L$ ratios. We attribute the deviation of a number of faint blue
dwarfs from the FP of brighter ellipticals to this effect.
We also study other scaling relations involving galaxy photometric properties
including the photometric plane. We show that, compared to the FP, the scatter
about the photometric plane is smaller at the faint end. |
A new model of galaxy formation: How sensitive are predicted galaxy
luminosities to the choice of SPS model?: We present a new release of the GALFORM semi-analytical model of galaxy
formation and evolution, which exploits a Millennium Simulation-class N-body
run performed with the WMAP7 cosmology. We use this new model to study the
impact of the choice of stellar population synthesis (SPS) model on the
predicted evolution of the galaxy luminosity function. The semi-analytical
model is run using seven different SPS models. In each case we obtain the
rest-frame luminosity function in the far-ultra-violet, optical and
near-infrared (NIR) wavelength ranges. We find that both the predicted
rest-frame ultra-violet and optical luminosity function are insensitive to the
choice of SPS model. However, we find that the predicted evolution of the
rest-frame NIR luminosity function depends strongly on the treatment of the
thermally pulsating asymptotic giant branch (TP-AGB) stellar phase in the SPS
models, with differences larger than a factor of 2 for model galaxies brighter
than $M_{\rm AB}(K)-5$log$h<-22$ ($\sim$L$_*$ for $0\leq z\leq 1.5$). We have
also explored the predicted number counts of galaxies, finding remarkable
agreement between the results with different choices of SPS model, except when
selecting galaxies with very red optical-NIR colours. The predicted number
counts of these extremely red galaxies appear to be more affected by the
treatment of star formation in disks than by the treatment of TP-AGB stars in
the SPS models. | Herschel-SPIRE observations of the disturbed galaxy NGC4438: We present Herschel-SPIRE observations of the perturbed galaxy NGC4438 in the
Virgo cluster. These images reveal the presence of extra-planar dust up to ~4-5
kpc away from the galaxy's disk. The dust closely follows the distribution of
the stripped atomic and molecular hydrogen, supporting the idea that gas and
dust are perturbed in a similar fashion by the cluster environment.
Interestingly, the extra-planar dust lacks a warm temperature component when
compared to the material still present in the disk, explaining why it was
missed by previous far-infrared investigations. Our study provides evidence for
dust stripping in clusters of galaxies and illustrates the potential of
Herschel data for our understanding of environmental effects on galaxy
evolution. |
Quantum diffusion and large primordial perturbations from inflation: Quantum diffusion describes the inflow of vacuum quantum fluctuations as they
get amplified by gravitational instability, and stretched to large distances
during inflation. In this picture, the dynamics of the universe's expansion
becomes stochastic, and the statistics of the curvature perturbation is encoded
in the distribution of the duration of inflation. This provides a
non-perturbative framework to study cosmological fluctuations during inflation,
which is well-suited to the case of primordial black holes since they originate
from large fluctuations. We show that standard, perturbative expectations for
the primordial black hole abundance can be significantly modified by
quantum-diffusion effects, and we identify a few open challenges. | CO luminosity-Linewidth correlation of low and high redshift galaxies
and its possible cosmological utilization: A linear correlation has been proposed between the CO luminosity
($\rm{L}^{\prime}_{\rm{CO}}$) and full-width at half maximum (FWHM) for
high-redshift (z > 1) submillimeter galaxies. However, the controversy
concerning the $\rm{L}^{\prime}_{\rm{CO}}$-FWHM correlation seems to have been
caused by the use of heterogeneous samples (e.g., different transition lines)
and/or data with large measurement uncertainties. In order to avoid the
uncertainty caused by using different rotational transitions, in this work we
make an extensive effort to select only CO($J = 1-0$) data from the literature.
We separate these wide-ranging redshift data into two samples : the
low-redshift (z < 1) and high-redshift (z > 1) samples. The samples are
corrected for lensing magnification factors if gravitational-lensing effects
appeared in the observations. The correlation analysis shows that there exists
significant $\rm{L}^{\prime}_{\rm{CO}}$-FWHM correlations for both the
low-redshift and high-redshift samples. A comparison of the low- and
high-redshift $\rm{L}^{\prime}_{\rm{CO}}$-FWHM correlations does not show
strong evolution with redshift. Assuming that there is no evolution, we can use
this relation to determine the model independent distances of high-redshift
galaxies. We then constrain cosmological models with the calibrated
high-redshift CO data and the sample of Type Ia supernovae in the Union 2.1
compilation. In the constraint for wCDM with our samples, the derived values
are w_{0} = -1.02 {\pm} 0.17, {\Omega}_{m0} = 0.30{\pm}0.02, and H_{0} = 70.00
{\pm}0.60 km\,s^{-1}\,Mpc^{-1}. |
Scale Dependent Local Non-Gaussianity from Loops: We analyze multi-field inflationary systems which yield strongly scale
dependent non-Gaussianity with a shape that is very close to the local shape.
As in usual multi-field models, the non-Gaussianity arises from the non-linear
transfer of scalar field fluctuations to curvature perturbations. Here we
consider models in which higher order terms (loops) dominate over the lowest
order source of non-linearity. The magnitude of non-Gaussianity depends on an
infrared cutoff which is determined by our observational probes measuring
non-Gaussianity. In our models, the running is positive and large (n_{NG} ~
0.2) on CMB scales. The magnitude of the bispectrum is maximally of order
O(100), and grows on small scales. This can lead to interesting signals for
large scale structure. | The evolution of the dust temperatures of galaxies in the SFR$-M_{\ast}$
plane up to $z$$\,\thicksim\,$$2$: [Abridged] We study the evolution of the dust temperatures of galaxies in the
SFR-M* plane up to z~2 using observations from the Herschel Space Observatory.
Starting from a sample of galaxies with reliable star-formation rates (SFRs),
stellar masses (M*) and redshift estimates, we grid the SFR-M* parameter space
in several redshift ranges and estimate the mean Tdust of each SFR-M*-z bin.
Dust temperatures are inferred using the stacked far-infrared flux densities of
our SFR-M*-z bins. At all redshifts, Tdust increases with infrared luminosities
(LIR), specific SFRs (SSFR; i.e., SFR/M*) and distances with respect to the
main sequence (MS) of the SFR-M* plane (i.e.,
D_SSFR_MS=log[SSFR(galaxy)/SSFR_MS(M*,z)]). The Tdust-SSFR and Tdust-D_SSFR_MS
correlations are statistically more significant than the Tdust-LIR one. While
the slopes of these three correlations are redshift-independent, their
normalizations evolve from z=0 and z~2. We convert these results into a recipe
to derive Tdust from SFR, M* and z. The existence of a strong Tdust-D_SSFR_MS
correlation provides us with information on the dust and gas content of
galaxies. (i) The slope of the Tdust-D__SSFR_MS correlation can be explained by
the increase of the star-formation efficiency (SFE; SFR/Mgas) with D_SSFR_MS as
found locally by molecular gas studies. (ii) At fixed D_SSFR_MS, the constant
Tdust observed in galaxies probing large ranges in SFR and M* can be explained
by an increase or decrease of the number of star-forming regions with
comparable SFE enclosed in them. (iii) At high redshift, the normalization
towards hotter temperature of the Tdust-D_SSFR_MS correlation can be explained
by the decrease of the metallicities of galaxies or by the increase of the SFE
of MS galaxies. All these results support the hypothesis that the conditions
prevailing in the star-forming regions of MS and far-above-MS galaxies are
different. |
Constraining Nonthermal Dark Matter's Impact on the Matter Power
Spectrum: The inclusion of a period of (effective) matter domination following
inflation and prior to the onset of radiation domination has interesting and
observable consequences for structure growth. During this early
matter-dominated era (EMDE), the Universe was dominated by massive particles,
or an oscillating scalar field, that decayed into Standard Model particles,
thus reheating the Universe. This decay process could also be the primary
source of dark matter. In the absence of fine-tuning between the masses of the
parent and daughter particles, both dark matter particles and Standard Model
particles would be produced with relativistic velocities. We investigate the
effects of the nonthermal production of dark matter particles with relativistic
velocities on the matter power spectrum by determining the resulting velocity
distribution function for the dark matter. We find that the vast majority of
dark matter particles produced during the EMDE are still relativistic at
reheating, so their free streaming erases the perturbations that grow during
the EMDE. The free streaming of the dark matter particles can also prevent the
formation of satellite galaxies around the Milky Way and the structures
observed in the Lyman-$\alpha$ forest. For a given reheat temperature, these
observations put an upper limit on the velocity of the dark matter particles at
their creation. For example, for a reheat temperature of 10 MeV, dark matter
must be produced with a Lorentz factor $\gamma \lesssim 550$. | Universal at last? The splashback mass function of dark matter halos: The mass function of dark matter halos is one of the most fundamental
statistics in structure formation. Many theoretical models (such as
Press-Schechter theory) are based on the notion that it could be universal,
meaning independent of redshift and cosmology, when expressed in the
appropriate variables. However, simulations exhibit persistent
non-universalities in the mass functions of the virial mass and other commonly
used spherical overdensity definitions. We systematically study the
universality of mass functions over a wide range of mass definitions, for the
first time including the recently proposed splashback mass, Msp. We confirm
that, in LambdaCDM cosmologies, all mass definitions exhibit varying levels of
non-universality that increase with peak height and reach between 20% and 500%
at the highest masses we can test. Mvir, M200m, and Msp exhibit similar levels
of non-universality. There are, however, two regimes where the splashback mass
functions are significantly more universal. First, they are universal to 10% at
z<2, whereas spherical overdensity definitions experience an evolution due to
dark energy. Second, when additionally considering self-similar cosmologies
with extreme power spectra, splashback mass functions are remarkably universal
(to between 40% and 60%) whereas their spherical overdensity counterparts reach
non-universalities between 180% and 450%. These results strongly support the
notion that the splashback radius is a physically motivated definition of the
halo boundary. We present a simple, universal fitting formula for splashback
mass functions that accurately reproduces our simulation data. |
On the Fast Random Sampling and Other Properties of the Three Point
Correlation Function in Galaxy Surveys: In the forthcoming large volume galaxy surveys higher order statistics will
provide complementary information to the usual two point statistics. Low
variance estimators of the Three Point Correlation Function (3CPF) of discrete
data count triangle configurations with vertices mixing data and random
catalogues. Large density random catalogues are used to reduce the shot noise,
which leads to a computational cost of one or two orders of magnitude more than
the pure data histogram. In this paper, we explore time reductions of the
isotropic 3PCF random sampling terms in periodic boxes without using random
catalogues. In the first approach, based on Hamilton's construction of his
famous two point estimator, we use an ad-hoc two point correlation term, while
for the second procedure we construct the operators from a geometrical
viewpoint, using two sides and their opening angle to describe the 3PCF
triangle configurations. We map the last result to the three triangle side
basis either numerically or analytically, and show that the latter approach
performs best when applied to synthetic data. Moreover, we elaborate on going
beyond periodic boxes, discuss other low variance n-point estimators and
present useful 3PCF visualization schemes. | The environment and characteristics of low redshift galaxies detected by
the Herschel-ATLAS: We investigate the ultraviolet and optical properties and environment of low
redshift galaxies detected in the Herschel Astrophysical Terahertz Large Area
Survey (H-ATLAS) science demonstration data. We use the Sloan Digital Sky
Survey seventh release and the Galaxy And Mass Assembly database to select
galaxies with r_Petro < 19.0 mag in the redshift range 0.02 < z < 0.2 and look
for their submillimeter counterparts in H-ATLAS. Our results show that at low
redshift, H-ATLAS detects mainly blue/star-forming galaxies with a minor
contribution from red systems which are highly obscured by dust. In addition we
find that the colour of a galaxy rather than the local density of its
environment determines whether it is detectable by H-ATLAS. The average dust
temperature of galaxies that are simultaneously detected by both PACS and SPIRE
is 25K \pm 4K, independent of environment. This analysis provides a glimpse of
the potential of the H-ATLAS data to investigate the submillimeter properties
of galaxies in the local universe. |
Constraining Bianchi Type I Universe With Type Ia Supernova and H(z)
Data: We use recent 36 observational Hubble data (OHD) in the redshift range
$0.07\leq z\leq 2.36$, latest \textgravedbl joint light curves\textacutedbl
(JLA) sample, comprised of 740 type Ia supernovae (SNIa) in the redshift range
$0.01\leq z \leq 1.30$, and their joint combination datasets to constrain
anisotropic Bianchi type I (BI) dark energy (DE) model. To estimate model
parameters, we apply Hamiltonian Monte Carlo technique. We also compute the
covariance matrix for BI dark energy model by considering different datasets to
compare the correlation between model parameters. To check the acceptability of
our fittings, all results are compared with those obtained from 9 year WMAP as
well as Planck (2015) collaboration. Our estimations show that at 68\%
confidence level the dark energy equation of state (EOS) parameter for OHD or
JLA datasets alone varies between quintessence and phantom regions whereas for
OHD+JLA dataset this parameter only varies in phantom region. It is also found
that the current cosmic anisotropy is of order $\sim10^{-3}$ which imply that
the OHD and JLA datasets do not put tight constraint on this parameter.
Therefore, to constraint anisotropy parameter, it is necessary to use high
redshif dataset namely cosmic microwave background (CMB). Moreover, from the
calculation of $p$-value associated with $\chi^{2}$ statistic we observed that
non of the $\omega \mbox{BI}$ and flat $\omega\mbox{CDM}$ models rule out by
OHD or JLA datasets. The deceleration parameter is obtained as $q=-0.46^{+0.89
+0.36}_{-0.41 -0.37}$, $q=-0.619^{+0.12 +0.20}_{-0.095 -0.24}$, and
$q=-0.52^{+0.080 +0.014}_{-0.046 -0.15}$ for OHD, SNIa, and OHD+SNIa data
respectively. | Environmental effects in the interaction and merging of galaxies in
zCOSMOS survey: The zCOSMOS-bright 10k spectroscopic sample reveals a strong environmental
dependence of close kinematic galaxy pair fractions in the redshift range 0.2 <
z < 1. The fraction of close pairs is three times higher in the top density
quartile than in the lowest one. This environmental variation in pair fractions
will translate into merger fractions since merger timescales are shown, based
on Millennium simulation catalogs, to be largely independent of environment.
While galactic properties of close kinematic pairs (morphologies and star
formation rates) may seem to be non-representative of an underlying galaxy
population, they can be explained by taking into account well-known effects of
environment, and changes caused by interactions. The latter is responsible for
an increase of irregular galaxies in pairs by a factor of 50-75%, with a
disproportionate increase in the number of irregular-irregular pairs (4-8
times), due to disturbance of about 15% of the disk galaxies in pairs. Another
sign of interaction is an observed boost in specific star formation rate
(factor 2-4) for the closest pairs. While significant for paired galaxies, this
triggered star-formation due to interactions represents only about 5% of the
integrated star-formation activity in our volume-limited sample. Although
majority of close kinematic pairs are in dense environments, the effects of
interactions appear to be strongest in the lower density environments. This may
introduce strong biases into observational studies of mergers, especially those
based on morphological criteria. Relative excess of post-starburst galaxies
observed in paired galaxies (factor \sim2) as well as excess of AGNs (factor of
over 2), linked with environmental dependence of the pair fractions could
indicate that early phases of interactions and merging are plausible candidates
for environmental quenching, observed in the global galaxy populations. |
Herschel PACS Spectroscopic Diagnostics of Local ULIRGs: Conditions and
Kinematics in Mrk 231: In this first paper on the results of our Herschel PACS survey of local
Ultraluminous Infrared Galaxies (ULIRGs), as part of our SHINING survey of
local galaxies, we present far-infrared spectroscopy of Mrk 231, the most
luminous of the local ULIRGs, and a type 1 broad absorption line AGN. For the
first time in a ULIRG, all observed far-infrared fine-structure lines in the
PACS range were detected and all were found to be deficient relative to the far
infrared luminosity by 1 - 2 orders of magnitude compared with lower luminosity
galaxies. The deficits are similar to those for the mid-infrared lines, with
the most deficient lines showing high ionization potentials. Aged starbursts
may account for part of the deficits, but partial covering of the highest
excitation AGN powered regions may explain the remaining line deficits. A
massive molecular outflow, discovered in OH and 18OH, showing outflow
velocities out to at least 1400 km/sec, is a unique signature of the clearing
out of the molecular disk that formed by dissipative collapse during the
merger. The outflow is characterized by extremely high ratios of 18O / 16O
suggestive of interstellar medium processing by advanced starbursts. | Globular Cluster Scale Sizes in Giant Galaxies: The Case of M87 and the
Role of Orbital Anisotropy and Tidal Filling: We present new Hubble Space Telescope imaging of the outer regions of M87 in
order to study its globular cluster (GC) population out to large galactocentric
distances. We discuss particularly the relationship between GC effective radii
$r_h$ and projected galactocentric distance $R_{gc}$. The observations suggest
a shallow trend $r_h \propto R_{gc}^{0.14}$ out to $R_{gc} \sim 100$ kpc, in
agreement with studies of other giant elliptical galaxies. To theoretically
reproduce this relationship we simulate GC populations with various
distributions of orbits. For an isotropic distribution of cluster orbits we
find a steeper trend of $r_h \propto R_{gc}^{0.4}$. Instead we suggest that (a)
if the cluster system has an orbital anisotropy profile, where orbits become
preferentially radial with increasing galactocentric distance, AND (b) if
clusters become more tidally under-filling with galactocentric distance, the
observed relationship can be recovered. We also apply this approach to the red
and blue GC populations separately and predict that red clusters are
preferentially under-filling at large $R_{gc}$ and have a more isotropic
distribution of orbits than blue clusters. |
Void asymmetries in the cosmic web: a mechanism for bulk flows: Bulk flows of galaxies moving with respect to the cosmic microwave background
are well established observationally and seen in the most recent LCDM
simulations. With the aid of an idealised Gadget-2 simulation, we show that
void asymmetries in the cosmic web can exacerbate local bulk flows of galaxies.
The Cosmicflows-2 survey, which has mapped in detail the 3D structure of the
Local Universe, reveals that the Local Group resides in a "local sheet" of
galaxies that borders a "local void" with a diameter of about 40 Mpc. The void
is emptying out at a rate of 16 km/s/Mpc. In a co-moving frame, the Local Sheet
is found to be moving away from the Local Void at ~ 260 km/s. Our model shows
how asymmetric collapse due to unbalanced voids on either side of a developing
sheet or wall can lead to a systematic movement of the sheet. We conjectured
that asymmetries could lead to a large-scale separation of dark matter and
baryons, thereby driving a dependence of galaxy properties with environment,
but we do not find any evidence for this effect. | Simulating the inflationary Universe: from single-field to the
axion-U(1) model: We present a nonlinear study of the inflationary epoch based on numerical
lattice simulations. Lattice simulations are a well-known tool in primordial
cosmology, and they have been extensively used to study the reheating epoch
after inflation. We generalize this known machinery to the inflationary epoch.
Being this the first simulation of the inflationary epoch much before the end
of inflation, the first part of the thesis focuses on the minimal single-field
model of inflation. We discuss the conceptual and technical ingredients needed
to simulate inflation on a lattice. The simulation is used to reproduce the
nearly scale-invariant spectrum of scalar perturbations, as well as the
oscillations in the power spectrum caused by a step in the potential. In the
second part, we focus on the more complicated axion-U(1) model of inflation and
present the first lattice simulation of this model during the deep inflationary
epoch. We use the simulation to discover new properties of primordial scalar
perturbations from this model. In the linear regime of the theory, we find
high-order non-Gaussianity (beyond trispectrum) to be key to describing the
statistical properties of scalar perturbations. Conversely, we find
perturbations to be nearly Gaussian in the nonlinear regime of the theory. This
relaxes existing constraints from the overproduction of primordial black holes,
allowing for a gravitational waves signal in the observable range of upcoming
experiments such as LISA. Our results show that lattice simulations can be a
powerful tool to study the inflationary epoch and its observational signatures. |
Preheating with Non-Minimal Kinetic Terms: We present the first 3+1-dimensional numerical simulations of scalar fields
with non-minimal kinetic terms. As an example, we examine the existence and
stability of preheating in the presence of a Dirac-Born-Infeld (DBI) inflaton
coupled to a canonical matter field. The simulations represent the full
non-linear theory in the presence of an expanding Universe. We show that
parametric resonance in the matter field, along with self-resonance in the
inflaton, repopulate the Universe with matter particles as efficiently as in
traditional preheating. | Despicable Dark Relics: generated by gravity with unconstrained masses: We demonstrate the existence of a generic, efficient and purely gravitational
channel producing a significant abundance of dark relics during reheating after
the end of inflation. The mechanism is present for any inert scalar with the
non-minimal curvature coupling $\xi R\chi^2$ and the relic production is
efficient for natural values $\xi = {\cal O}(1)$. The observed dark matter
abundance can be reached for a broad range of relic masses extending from $m
\sim 1 {\rm k eV}$ to $m \sim 10^{8} {\rm GeV}$, depending on the scale of
inflation and the dark sector couplings. Frustratingly, such relics escape
direct, indirect and collider searches since no non-gravitational couplings to
visible matter are needed. |
Dust and Metal Column Densities in Gamma-Ray Burst Host Galaxies: In this paper we present the results from the analysis of a sample of 28
gamma-ray burst (GRB) afterglow spectral energy distributions, spanning the
X-ray through to near-infrared wavelengths. This is the largest sample of GRB
afterglow spectral energy distributions thus far studied, providing a strong
handle on the optical depth distribution of soft X-ray absorption and
dust-extinction systems in GRB host galaxies. We detect an absorption system
within the GRB host galaxy in 79% of the sample, and an extinction system in
71% of the sample, and find the Small Magellanic Cloud (SMC) extinction law to
provide an acceptable fit to the host galaxy extinction profile for the
majority of cases, consistent with previous findings. The range in the soft
X-ray absorption to dust-extinction ratio, N_{H,X}/Av, in GRB host galaxies
spans almost two orders of magnitude, and the typical ratios are significantly
larger than those of the Magellanic Clouds or Milky Way. Although dust
destruction could be a cause, at least in part, for the large N_{H,X}/Av
ratios, the good fit provided by the SMC extinction law for the majority of our
sample suggests that there is an abundance of small dust grains in the GRB
environment, which we would expect to have been destroyed if dust destruction
were responsible for the large N_{H,X}/Av ratios. Instead, our analysis
suggests that the distribution of N_{H,X}/Av in GRB host galaxies may be mostly
intrinsic to these galaxies, and this is further substantiated by evidence for
a strong negative correlation between N_{H,X}/Av and metallicity for a
subsample of GRB hosts with known metallicity. Furthermore, we find the
N_{H,X}/Av ratio and metallicity for this subsample of GRBs to be comparable to
the relation found in other more metal-rich galaxies. | An improved Compton parameter map of thermal Sunyaev-Zeldovich effect
from Planck PR4 data: Taking advantage of the reduced levels of noise and systematics in the data
of the latest Planck release (PR4, also known as NPIPE), we construct a new
all-sky Compton-$y$ parameter map (hereafter, $y$-map) of the thermal
Sunyaev-Zeldovich (SZ) effect from the Planck PR4 data. A tailored Needlet
Internal Linear Combination (NILC) pipeline, first validated on detailed sky
simulations, is applied to the nine single-frequency Planck PR4 sky maps,
ranging from $30$ to $857$ GHz, to produce the PR4 $y$-map over 98% of the sky.
Using map comparisons, angular power spectra and one-point statistics we show
that the PR4 NILC $y$-map is of improved quality compared to that of the
previous PR2 release. The new $y$-map shows reduced levels of large-scale
striations associated with $1/f$ noise in the scan direction. Regions near the
Galactic plane also show lower residual contamination by Galactic thermal dust
emission. At small angular scales, the residual contamination by thermal noise
and cosmic infrared background (CIB) emission is found to be reduced by around
7% and 34%, respectively, in the PR4 $y$-map. The PR4 NILC $y$-map is made
publicly available for astrophysical and cosmological analyses of the thermal
SZ effect. |
An application of extreme value statistics to the most massive galaxy
clusters at low and high redshifts: In this work we present an application of general extreme value statistics
(GEV) to very massive single clusters at high and low redshifts. After
introducing the formalism, we apply this statistics to four very massive high
redshift clusters. Those clusters comprise ACT-CL J0102-4915 with a mass of
M_200m=(2.16+/-0.32)x10^{15} M_sun at a redshift of z=0.87, SPT-CL J2106-5844
with a mass of M_200m=(1.27+/-0.21)x10^{15} M_sun at z=1.132 and two clusters
found by the XMM-Newton Distant Cluster Project survey: XMMU J2235.32557 with a
mass of M_200c= (7.3+/-1.3)x10^{14} M_sun located at a redshift of z=1.4 and
XMMU J0044.0-2033 having a mass in the range of M_200c= (3.5-5.0)x10^{14} M_sun
at z=1.579. By relating those systems to their corresponding distribution
functions of being the most massive system in a given survey area, we find that
none of the systems alone is in extreme tension with LCDM. We confront these
results with a GEV analysis of four very massive low redshift clusters: A2163,
A370, RXJ1347-1145 and 1E0657-558, finding no tendency of the high-z systems to
be more extreme than the low-z ones. In addition, we study the extreme
quantiles of single clusters at high-z and present contour plots for fixed
quantiles in the mass vs. survey area plane for four redshift intervals,
finding that, in order to be significantly in conflict with LCDM, cluster
masses would have to be substantially higher than the currently observed ones. | Quadruple-peaked spectral line profiles as a tool to constrain
gravitational potential of shell galaxies: Stellar shells observed in many giant elliptical and lenticular as well as a
few spiral and dwarf galaxies, presumably result from galaxy mergers.
Line-of-sight velocity distributions of the shells could, in principle, if
measured with a sufficiently high S/N, constitute one of methods to constrain
the gravitational potential of the host galaxy. Merrifield & Kuijken (1998)
predicted a double-peaked line profile for stationary shells resulting from a
nearly radial minor merger. In this paper, we aim at extending their analysis
to a more realistic case of expanding shells, inherent to the merging process,
whereas we assume the same type of merger and the same orbital geometry. We use
analytical approach as well as test particle simulations to predict the
line-of-sight velocity profile across the shell structure. Simulated line
profiles are convolved with spectral PSFs to estimate the peak detectability.
The resulting line-of-sight velocity distributions are more complex than
previously predicted due to non-zero phase velocity of the shells. In
principle, each of the Merrifield & Kuijken (1998) peaks splits into two,
giving a quadruple-peaked line profile, which allows more precise determination
of the potential of the host galaxy and, moreover, contains additional
information. We find simple analytical expressions that connect the positions
of the four peaks of the line profile and the mass distribution of the galaxy,
namely the circular velocity at the given shell radius and the propagation
velocity of the shell. The analytical expressions were applied to a
test-particle simulation of a radial minor merger and the potential of the
simulated host galaxy was successfully recovered. The shell kinematics can thus
become an independent tool to determine the content and distribution of the
dark matter in shell galaxies, up to ~100 kpc from the center of the host
galaxy. |
Dark energy constraints from ESPRESSO tests of the stability of
fundamental couplings: ESPRESSO is a high-resolution-ultra-stable spectrograph for the VLT, whose
commissioning will start in 2017. One of its key science goals is to test the
stability of nature's fundamental couplings with unprecedented accuracy and
control of possible systematics. A total of 27 nights of the ESPRESSO
Consortium's guaranteed time observations (GTO) will be spent in testing the
stability of the fine-structure constant and other fundamental couplings. A set
of 14 priority optimal targets have been selected for the GTO period. Here we
briefly discuss the criteria underlying this selection and describe the
selected targets, and then present detailed forecasts of the impact of these
measurements on fundamental physics and cosmology, focusing on dark energy
constraints and using future supernova type Ia surveys as a comparison point.
We show how canonical reconstructions of the dark energy equation of state are
improved by the extended redshift range enabled by these spectroscopic
measurements, and also quantify additional improvements foreseen for a future
ELT-HIRES instrument. | Constraints on dark energy from H II starburst galaxy apparent magnitude
versus redshift data: In this paper we use H II starburst galaxy apparent magnitude versus redshift
data from Siegel et al. (2005) to constrain dark energy cosmological model
parameters. These constraints are generally consistent with those derived using
other data sets, but are not as restrictive as the tightest currently available
constraints. |
X-ray background and its correlation with the 21 cm signal: We use high resolution hydrodynamical simulations to study the contribution
to the X-ray background from high-$z$ energetic sources, such as X-ray
binaries, accreting nuclear black holes and shock heated interstellar medium.
Adopting the model discussed in Eide et al. (2018), we find that these X-ray
sources during the Epoch of Reionization (EoR) contribute less than a few
percent of the unresolved X-ray background. The same sources contribute to less
than $\sim$2\% of the measured angular power spectrum of the fluctuations of
the X-ray background. The outputs of radiative transfer simulations modeling
the EoR are used to evaluate the cross-correlations of X-ray background with
the 21~cm signal from neutral hydrogen. Such correlation could be used to
confirm the origin of the 21 cm signal, as well as give information on the
properties of the X-ray sources during the EoR. We find that the correlations
are positive during the early stages of reionization when most of the hydrogen
is neutral, while they become negative when the intergalactic medium gets
highly ionized, with the transition from positive to negative depending on both
the X-ray model and the scale under consideration. With {\tt SKA} as the
reference instrument for the 21~cm experiment, the predicted S/N for such
correlations is $<1$ if the corresponding X-ray survey is only able to resolve
and remove X-ray sources with observed flux $>10^{-15}\,\rm erg\, cm^{-2} \,
s^{-1}$, while the cumulative S/N from $l=1000$ to $10^{4}$ at $x_{\rm HI}=0.5$
is $\sim 5$ if sources with observed flux $>10^{-17}\,\rm erg\, cm^{-2} \,
s^{-1}$ are detected. | Numerical estimation of the escaping flux of massless particles created
in collisions around a Kerr black hole: The geodesics of massless particles produced in collisions near a rotating
black hole are solved numerically and a Monte Carlo integration of the momentum
distribution of the massless particles is performed to calculate the fraction
that escape the black hole to infinity. A distribution of in falling dark
matter particles, which are assumed to annihilate to massless particles, is
considered and an estimate of the emergent flux from the collisions is made.
The energy spectrum of the emergent particles is found to contain two Lorentz
shifted peaks centred on the mass of the dark matter. The separation of the
peaks is found to depend on the density profile of the dark matter and could
provide information about the size of the annihilation plateau around a black
hole and the mass of the dark matter particle. |
Observational implications of mattergenesis during inflation: The observed baryon asymmetry, as well as potentially an asymmetry in the
dark matter sector, can be produced through dissipative particle production
during inflation. A distinctive feature of this mechanism is the generation of
matter isocurvature perturbations that are fully (anti-)correlated with the
dominant adiabatic curvature perturbations. We show that chaotic warm inflation
models yield anti-correlated isocurvature modes that may partially or even
completely screen the contribution of primordial gravity waves to the CMB
temperature power spectrum. The tensor-to-scalar ratio inferred from the latter
may thus be parametrically smaller than the one deduced from B-mode
polarization maps, which is particularly relevant in the light of the recently
announced results of the BICEP2 experiment. | Light WIMPs, Equivalent Neutrinos, BBN, and the CMB: Recent updates to the observational determinations of the primordial
abundances of helium and deuterium are compared to the predictions of BBN to
infer the universal ratio of baryons to photons (or, the present Universe
baryon mass density parameter Omega_B h^2), as well as to constrain the
effective number of neutrinos (N_eff) and the number of equivalent neutrinos
(Delta N_nu). These BBN results are compared to those derived independently
from the Planck CMB data. In the absence of a light WIMP (chi), N_eff = 3.05(1
+ Delta N_nu/3). In this case, there is excellent agreement between BBN and the
CMB, but the joint fit finds that Delta N_nu = 0.40 +/- 0.17, disfavoring
standard big bang nucleosynthesis (SBBN: Delta N_nu = 0) at 2.4 sigma, as well
as a sterile neutrino (Delta N_nu = 1) at 3.5 sigma. In the presence of a light
WIMP, the relation between N_eff and Delta N_nu depends on the WIMP mass,
leading to degeneracies among N_eff, Delta N_nu, and m_chi. The complementary
and independent BBN and CMB data can break some of these degeneracies.
Depending on the nature of the light WIMP (Majorana or Dirac fermion, real or
complex scalar) the joint BBN + CMB analyses set a lower bound to m_chi in the
range from 0.5 to 5 MeV, and they identify best fit values for m_chi in the
range from 5 to 10 MeV. The joint BBN + CMB analyses find a best fit value for
the number of equivalent neutrinos, Delta N_nu = 0.65, nearly independent of
the nature of the WIMP. The best fit still disfavors the absence of dark
radiation (Delta N_nu = 0 at 95% confidence), while allowing for the presence
of a sterile neutrino (Delta N_nu = 1 at less than 1 sigma). For all cases
considered here, the lithium problem persists. These results, presented at the
2013 Rencontres de l'Observatoire de Paris - ESO Workshop, are based on Nollett
& Steigman 2013 (arXiv:1312.5725 [astro-ph.CO]). |
The WIRCam Deep Survey II: Mass Selected Clustering: We present an analysis of the clustering of galaxies from z ~ 2 to the
present day using the WIRCam Deep Survey (WIRDS). WIRDS combines deep
near-infrared data with the deep optical data from the CFHTLS Deep fields,
providing a photometric data-set over an effective area of 2.4 sq. deg., from
which accurate photometric redshifts and stellar masses can be estimated. We
use the data to calculate the angular correlation function for galaxy samples
split by star-formation activity, stellar mass and redshift. We estimate the
real-space clustering for each sample, determining clustering lengths and
power-law slopes. For galaxies selected by constant mass, we find that the
clustering scale shows no evolution up to z ~ 2. Splitting the galaxy sample by
mass, we see that higher mass galaxies have larger clustering scales at all
redshifts. We use our results to test the GALFORM semi-analytical galaxy
formation model and find the two are consistent. We split the galaxy population
into passive and star-forming populations and find that the passive galaxy
population shows a significantly larger clustering scale at all redshifts than
the star-forming population below masses of ~$10^{11}M_\odot/h$, showing that
even at z ~ 2 passive galaxies exist in denser environments than the bulk of
the star-forming galaxy population. For star-forming galaxies with stellar
masses $>10^{11}M_\odot/h$, we find a clustering strength of ~8Mpc/h across all
redshifts, comparable to the measurements for the passive population. Also, for
star-forming galaxies we see that clustering strength increases for higher
stellar mass systems, however there is little sign of a mass dependence in
passive galaxies. Finally, we investigate the connection between galaxy stellar
mass and dark matter halo mass, showing a clear correlation between the two in
both the WIRDS data and the GALFORM predictions. | Cosmological parameter constraints from SDSS luminous red galaxies: a
new treatment of large-scale clustering: We apply a new model for the spherically averaged correlation function at
large pair separations to the measurement of the clustering of luminous red
galaxies (LRGs) made from the SDSS by Cabre and Gaztanaga(2009). Our model
takes into account the form of the BAO peak and the large scale shape of the
correlation function. We perform a Monte Carlo Markov chain analysis for
different combinations of datasets and for different parameter sets. When used
in combination with a compilation of the latest CMB measurements, the LRG
clustering and the latest supernovae results give constraints on cosmological
parameters which are comparable and in remarkably good agreement, resolving the
tension reported in some studies. The best fitting model in the context of a
flat, Lambda-CDM cosmology is specified by Omega_m=0.261+-0.013,
Omega_b=0.044+-0.001, n_s=0.96+-0.01, H_0=71.6+-1.2 km/s/Mpc and
sigma_8=0.80+-0.02. If we allow the time-independent dark energy equation of
state parameter to vary, we find results consistent with a cosmological
constant at the 5% level using all data sets: w_DE=-0.97+-0.05. The large scale
structure measurements by themselves can constrain the dark energy equation of
state parameter to w_DE=-1.05+-0.15, independently of CMB or supernovae data.
We do not find convincing evidence for an evolving equation of state. We
provide a set of "extended distance priors" that contain the most relevant
information from the CMB power spectrum and the shape of the LRG correlation
function which can be used to constrain dark energy models and spatial
curvature. Our model should provide an accurate description of the clustering
even in much larger, forthcoming surveys, such as those planned with NASA's
JDEM or ESA's Euclid mission. |
High resolution simulations of the reionization of an isolated Milky Way
- M31 galaxy pair: We present the results of a set of numerical simulations aimed at studying
reionization at galactic scale. We use a high resolution simulation of the
formation of the Milky Way-M31 system to simulate the reionization of the local
group. The reionization calculation was performed with the post-processing
radiative transfer code ATON and the underlying cosmological simulation was
performed as part of the CLUES project. We vary the source models to bracket
the range of source properties used in the literature. We investigate the
structure and propagation of the galatic ionization fronts by a visual
examination of our reionization maps. Within the progenitors we find that
reionization is patchy, and proceeds locally inside out. The process becomes
patchier with decreasing source photon output. It is generally dominated by one
major HII region and 1-4 additional isolated smaller bubbles, which eventually
overlap. Higher emissivity results in faster and earlier local reionization. In
all models, the reionization of the Milky Way and M31 are similar in duration,
i.e. between 203 Myr and 22 Myr depending on the source model, placing their
zreion between 8.4 and 13.7. In all models except the most extreme, the MW and
M31 progenitors reionize internally, ignoring each other, despite being
relatively close to each other even during the epoch of reionization. Only in
the case of strong supernova feedback suppressing star formation in haloes less
massive than 10^9 M_sun, and using our highest emissivity, we find that the MW
is reionized by M31. | On the Number of Cosmic Strings: The number of cosmic strings in the observable universe is relevant in
determining the probability of detecting such cosmic defects through their
gravitational signatures. In particular, we refer to the observation of
gravitational lensing events and anisotropy in the CMB radiation induced by
cosmic strings. In this paper, a simple method is adopted to obtain an
approximate estimate of the number of segments of cosmic strings, crossing the
particle horizon, which fall inside the observed part of the universe. We show
that there is an appreciable difference in the expected number of segments
which differentiates cosmic strings arising in Abelian Higgs and Nambu-Goto
models, and that a different choice of setting for the cosmological model can
lead to significant differences in the expected number of cosmic string
segments. Of this number, the fraction realistically detectable may be
considerably smaller. |
POLARBEAR Constraints on Cosmic Birefringence and Primordial Magnetic
Fields: We constrain anisotropic cosmic birefringence using four-point correlations
of even-parity $E$-mode and odd-parity $B$-mode polarization in the cosmic
microwave background measurements made by the POLARization of the Background
Radiation (POLARBEAR) experiment in its first season of observations. We find
that the anisotropic cosmic birefringence signal from any parity-violating
processes is consistent with zero. The Faraday rotation from anisotropic cosmic
birefringence can be compared with the equivalent quantity generated by
primordial magnetic fields if they existed. The POLARBEAR nondetection
translates into a 95% confidence level (C.L.) upper limit of 93 nanogauss (nG)
on the amplitude of an equivalent primordial magnetic field inclusive of
systematic uncertainties. This four-point correlation constraint on Faraday
rotation is about 15 times tighter than the upper limit of 1380 nG inferred
from constraining the contribution of Faraday rotation to two-point
correlations of $B$-modes measured by Planck in 2015. Metric perturbations
sourced by primordial magnetic fields would also contribute to the $B$-mode
power spectrum. Using the POLARBEAR measurements of the $B$-mode power spectrum
(two-point correlation), we set a 95% C.L. upper limit of 3.9 nG on primordial
magnetic fields assuming a flat prior on the field amplitude. This limit is
comparable to what was found in the Planck 2015 two-point correlation analysis
with both temperature and polarization. We perform a set of systematic error
tests and find no evidence for contamination. This work marks the first time
that anisotropic cosmic birefringence or primordial magnetic fields have been
constrained from the ground at subdegree scales. | Satellite Kinematics III: Halo Masses of Central Galaxies in SDSS: We use the kinematics of satellite galaxies that orbit around the central
galaxy in a dark matter halo to infer the scaling relations between halo mass
and central galaxy properties. Using galaxies from the Sloan Digital Sky
Survey, we investigate the halo mass-luminosity relation (MLR) and the halo
mass-stellar mass relation (MSR) of central galaxies. In particular, we focus
on the dependence of these scaling relations on the colour of the central
galaxy. We find that red central galaxies on average occupy more massive haloes
than blue central galaxies of the same luminosity. However, at fixed stellar
mass there is no appreciable difference in the average halo mass of red and
blue centrals, especially for M* $\lsim$ 10^{10.5} h^{-2} Msun. This indicates
that stellar mass is a better indicator of halo mass than luminosity.
Nevertheless, we find that the scatter in halo masses at fixed stellar mass is
non-negligible for both red and blue centrals. It increases as a function of
stellar mass for red centrals but shows a fairly constant behaviour for blue
centrals. We compare the scaling relations obtained in this paper with results
from other independent studies of satellite kinematics, with results from a
SDSS galaxy group catalog, from galaxy-galaxy weak lensing measurements, and
from subhalo abundance matching studies. Overall, these different techniques
yield MLRs and MSRs in fairly good agreement with each other (typically within
a factor of two), indicating that we are converging on an accurate and reliable
description of the galaxy-dark matter connection. We briefly discuss some of
the remaining discrepancies among the various methods. |
Generating Merger Trees for Dark Matter Haloes: A Comparison of Methods: Halo merger trees describe the hierarchical mass assembly of dark matter
haloes, and are the backbone for modeling galaxy formation and evolution.
Merger trees constructed using Monte Carlo algorithms based on the extended
Press-Schechter (EPS) formalism are complementary to those extracted from
N-body simulations, and have the advantage that they are not trammeled by
limited numerical resolution and uncertainties in identifying (sub)haloes and
linking them between snapshots. This paper compares multiple EPS-based merger
tree algorithms to simulation results using four diagnostics: progenitor mass
function (PMF), mass assembly history (MAH), merger rate per descendant halo,
and the unevolved subhalo mass function (USMF). In general, algorithms based on
spherical collapse yield major-merger rates that are too high by a factor of
two, resulting in MAHs that are systematically offset. Assuming ellipsoidal
collapse solves most of these issues, but the particular algorithm investigated
here that incorporates ellipsoidal collapse dramatically overpredicts the
minor-merger rate for massive haloes. The only algorithm in our comparison that
yields MAHs, merger rates, and USMFs in good agreement with simulations, is
that by Parkinson et al. (2008). However, this is not a true EPS-based
algorithm as it draws its progenitor masses from a PMF calibrated against
simulations, rather than `predicted' by EPS. Finally we emphasize that the
benchmarks used to test the EPS algorithms are obtained from simulations and
are hampered by significant uncertainties themselves. In particular, MAHs and
halo merger rates obtained from simulations by different authors reveal
discrepancies that easily exceed 50 percent, even when based on the same
simulation. Given this status quo, merger trees constructed using the Parkinson
et al. algorithm are as accurate as those extracted from N-body simulations. | Neutrino-electron magnetohydrodynamics in an expanding Universe: We derive a new model for neutrino-plasma interactions in an expanding
universe that incorporates the collective effects of the neutrinos on the
plasma constituents. We start from the kinetic description of a multi-species
plasma in the flat Friedmann-Robertson-Walker metric, where the particles are
coupled to neutrinos through the charged- and neutral-current forms of the weak
interaction. We then derive the fluid equations and specialize our model to (a)
the lepton epoch, where we consider a pair electron-positron plasma interacting
with electron (anti-)neutrinos, and (b) after the electron-positron
annihilation, where we model an electron-proton plasma and take the limit of
slow ions and inertia-less electrons to obtain a set of neutrino-electron
magnetohydrodynamics (NEMHD) equations. In both models, the dynamics of the
plasma is affected by the neutrino motion through a ponderomotive force and, as
a result, new terms appear in the induction equation that can act as a source
for magnetic field generation in the early universe. A brief discussion on the
possible applications of our model is proposed. |
Dark matter halos around isolated ellipticals: We investigate the distribution of the luminous and the dark matter
components in the isolated ellipticals NGC 7052 and NGC 7785, embedded in an
emitting hot gas halo, by means of relevant X-ray and photometric data. In
order to calculate the dark matter distribution in these rare objects, we
performed an improved X-ray analysis of the XMM-Newton data of NGC 7785, and we
used former results based on Chandra data of NGC 7052. For each object we also
derived the stellar spheroid length scale from the surface photometry and the
spheroid stellar mass from an analysis of the galaxy spectral energy
distribution. We find that a dark matter component is present in these objects.
It is subdominant and mixed with the luminous matter inside the optical region
half-light radius wide, while it dominates the gravitational potential at outer
radii. On the whole, the dark halo structure is very similar to that found
around spirals of comparable luminosity and it is well reproduced by a Burkert
halo, while a Sersic spheroid accounts well for the baryonic component. | X-IFU/Athena view of the most distant galaxy clusters in the Universe: The X-ray Integral Field Unit (X-IFU) on-board the second large ESA mission
''Athena'' will be a high spatial (5'') and spectral (2.5eV) resolution X-ray
imaging spectrometer, operating in the 0.2-12 keV energy band. It will address
the science question of the assembly and evolution through cosmic time of the
largest halos of matter in the Universe, groups and clusters of galaxies. To
this end, we present an on-going feasibility study to demonstrate the X-IFU
capabilities to unveil the physics of massive halos at their epoch of
formation. Starting from a distant (z=2) group of galaxies ($M_{500} = 7\cdot
10^{13} M_\odot/h$) extracted from the HYDRANGEA cosmological and
hydrodynamical numerical simulations, we perform an end-to-end simulation of
X-IFU observations. From the reconstruction of the global, 1D and 2D
quantities, we plan to investigate the various X-IFU science cases for clusters
of galaxies, such as the chemical enrichment of the intra-cluster medium (ICM),
the dynamical assembly of groups and clusters and the impact of feedback from
galaxy and super-massive black hole evolution. |
Euclid: Covariance of weak lensing pseudo-$C_\ell$ estimates.
Calculation, comparison to simulations, and dependence on survey geometry: An accurate covariance matrix is essential for obtaining reliable
cosmological results when using a Gaussian likelihood. In this paper we study
the covariance of pseudo-$C_\ell$ estimates of tomographic cosmic shear power
spectra. Using two existing publicly available codes in combination, we
calculate the full covariance matrix, including mode-coupling contributions
arising from both partial sky coverage and non-linear structure growth. For
three different sky masks, we compare the theoretical covariance matrix to that
estimated from publicly available N-body weak lensing simulations, finding good
agreement. We find that as a more extreme sky cut is applied, a corresponding
increase in both Gaussian off-diagonal covariance and non-Gaussian super-sample
covariance is observed in both theory and simulations, in accordance with
expectations. Studying the different contributions to the covariance in detail,
we find that the Gaussian covariance dominates along the main diagonal and the
closest off-diagonals, but further away from the main diagonal the super-sample
covariance is dominant. Forming mock constraints in parameters describing
matter clustering and dark energy, we find that neglecting non-Gaussian
contributions to the covariance can lead to underestimating the true size of
confidence regions by up to 70 per cent. The dominant non-Gaussian covariance
component is the super-sample covariance, but neglecting the smaller connected
non-Gaussian covariance can still lead to the underestimation of uncertainties
by 10--20 per cent. A real cosmological analysis will require marginalisation
over many nuisance parameters, which will decrease the relative importance of
all cosmological contributions to the covariance, so these values should be
taken as upper limits on the importance of each component. | Dark Energy Survey Year 3 Results: Cosmology from Cosmic Shear and
Robustness to Data Calibration: This work, together with its companion paper, Secco and Samuroff et al.
(2021), presents the Dark Energy Survey Year 3 cosmic shear measurements and
cosmological constraints based on an analysis of over 100 million source
galaxies. With the data spanning 4143 deg$^2$ on the sky, divided into four
redshift bins, we produce the highest significance measurement of cosmic shear
to date, with a signal-to-noise of 40. We conduct a blind analysis in the
context of the $\Lambda$CDM model and find a 3% constraint of the clustering
amplitude, $S_8\equiv \sigma_8 (\Omega_{\rm m}/0.3)^{0.5} =
0.759^{+0.025}_{-0.023}$. A $\Lambda$CDM-Optimized analysis, which safely
includes smaller scale information, yields a 2% precision measurement of $S_8=
0.772^{+0.018}_{-0.017}$ that is consistent with the fiducial case. The two
low-redshift measurements are statistically consistent with the Planck Cosmic
Microwave Background result, however, both recovered $S_8$ values are lower
than the high-redshift prediction by $2.3\sigma$ and $2.1\sigma$ ($p$-values of
0.02 and 0.05), respectively. The measurements are shown to be internally
consistent across redshift bins, angular scales and correlation functions. The
analysis is demonstrated to be robust to calibration systematics, with the
$S_8$ posterior consistent when varying the choice of redshift calibration
sample, the modeling of redshift uncertainty and methodology. Similarly, we
find that the corrections included to account for the blending of galaxies
shifts our best-fit $S_8$ by $0.5\sigma$ without incurring a substantial
increase in uncertainty. We examine the limiting factors for the precision of
the cosmological constraints and find observational systematics to be
subdominant to the modeling of astrophysics. Specifically, we identify the
uncertainties in modeling baryonic effects and intrinsic alignments as the
limiting systematics. |
Galactic Outflows in Absorption and Emission: Near-UV Spectroscopy of
Galaxies at 1<z<2: We study large-scale outflows in a sample of 96 star-forming galaxies at
1<z<2, using near-UV spectroscopy of FeII and MgII absorption and emission. The
average blueshift of the FeII interstellar absorption lines with respect to the
systemic velocity is -85+/-10 km/s at z~1.5, with standard deviation 87 km/s;
this is a decrease of a factor of two from the average blueshift measured for
far-UV interstellar absorption lines in similarly selected galaxies at z~2. The
profiles of the MgII 2796, 2803 lines show much more variety than the FeII
profiles, which are always seen in absorption; MgII ranges from strong emission
to pure absorption, with emission more common in galaxies with blue UV slopes
and at lower stellar masses. Outflow velocities, as traced by the centroids and
maximum extent of the absorption lines, increase with increasing stellar mass
with 2-3sigma significance, in agreement with previous results. We study fine
structure emission from FeII*, finding several lines of evidence in support of
the model in which this emission is generated by the re-emission of continuum
photons absorbed in the FeII resonance transitions in outflowing gas. In
contrast, photoionization models indicate that MgII emission arises from the
resonant scattering of photons produced in HII regions, accounting for the
differing profiles of the MgII and FeII lines. A comparison of the strengths of
the FeII absorption and FeII* emission lines indicates that massive galaxies
have more extended outflows and/or greater extinction, while two-dimensional
composite spectra indicate that emission from the outflow is stronger at a
radius of ~10 kpc in high mass galaxies than in low mass galaxies. | A theoretical framework for combining techniques that probe the link
between galaxies and dark matter: We develop a theoretical framework that combines measurements of
galaxy-galaxy lensing, galaxy clustering, and the galaxy stellar mass function
in a self-consistent manner. While considerable effort has been invested in
exploring each of these probes individually, attempts to combine them are still
in their infancy despite the potential of such combinations to elucidate the
galaxy-dark matter connection, to constrain cosmological parameters, and to
test the nature of gravity. In this paper, we focus on a theoretical model that
describes the galaxy-dark matter connection based on standard halo occupation
distribution techniques. Several key modifications enable us to extract
additional parameters that determine the stellar-to-halo mass relation and to
simultaneously fit data from multiple probes while allowing for independent
binning schemes for each probe. In a companion paper, we demonstrate that the
model presented here provides an excellent fit to galaxy-galaxy lensing, galaxy
clustering, and stellar mass functions measured in the COSMOS survey from z=0.2
to z=1.0. We construct mock catalogs from numerical simulations to investigate
the effects of sample variance and covariance on each of the three probes.
Finally, we analyze and discuss how trends in each of the three observables
impact the derived parameters of the model. In particular, we investigate the
various features of the observed galaxy stellar mass function (low-mass slope,
plateau, knee, and high-mass cut-off) and show how each feature is related to
the underlying relationship between stellar and halo mass. We demonstrate that
the observed plateau feature in the stellar mass function at Mstellar~2x10^10
Msun is due to the transition that occurs in the stellar-to-halo mass relation
at Mhalo ~ 10^12 Msun from a low-mass power-law regime to a sub-exponential
function at higher stellar mass. |
All-Sky Analysis of the General Relativistic Galaxy Power Spectrum: We perform an all-sky analysis of the general relativistic galaxy power
spectrum using the well-developed spherical Fourier decomposition. Spherical
Fourier analysis expresses the observed galaxy fluctuation in terms of the
spherical harmonics and spherical Bessel functions that are angular and radial
eigenfunctions of the Helmholtz equation, providing a natural orthogonal basis
for all-sky analysis of the large-scale mode measurements. Accounting for all
the relativistic effects in galaxy clustering, we compute the spherical power
spectrum and its covariance matrix and compare it to the standard
three-dimensional power spectrum to establish a connection. The spherical power
spectrum recovers the three-dimensional power spectrum at each wavenumber k
with its angular dependence mu_k encoded in angular multipole l, and the
contributions of the line-of-sight projection to galaxy clustering such as the
gravitational lensing effect can be readily accommodated in the spherical
Fourier analysis. A complete list of formulas for computing the relativistic
spherical galaxy power spectrum is also presented. | Hot gas halos around disk galaxies: Confronting cosmological simulations
with observations: Models of disk galaxy formation commonly predict the existence of an extended
reservoir of accreted hot gas surrounding massive spirals at low redshift. As a
test of these models, we use X-ray and H-alpha data of the two massive,
quiescent edge-on spirals NGC 5746 and NGC 5170 to investigate the amount and
origin of any hot gas in their halos. Contrary to our earlier claim, the
Chandra analysis of NGC 5746, employing more recent calibration data, does not
reveal any significant evidence for diffuse X-ray emission outside the optical
disk, with a 3-sigma upper limit to the halo X-ray luminosity of 4e39 erg/s. An
identical study of the less massive NGC 5170 also fails to detect any
extraplanar X-ray emission. By extracting hot halo properties of disk galaxies
formed in cosmological hydrodynamical simulations, we compare these results to
expectations for cosmological accretion of hot gas by spirals. For Milky
Way-sized galaxies, these high-resolution simulations predict hot halo X-ray
luminosities which are lower by a factor of ~2 compared to our earlier results
reported by Toft et al. (2002). We find the new simulation predictions to be
consistent with our observational constraints for both NGC 5746 and NGC 5170,
while also confirming that the hot gas detected so far around more actively
star-forming spirals is in general probably associated with stellar activity in
the disk. Observational results on quiescent disk galaxies at the high-mass end
are nevertheless providing powerful constraints on theoretical predictions, and
hence on the assumed input physics in numerical studies of disk galaxy
formation and evolution. |
Constraints on secret neutrino interactions after Planck: (Abridged) Neutrino interactions beyond the standard model may affect the
cosmological evolution and can be constrained through observations. We consider
the possibility that neutrinos possess secret scalar or pseudoscalar
interactions mediated by the Nambu-Goldstone boson of a still unknown
spontaneously broken global $U(1)$ symmetry, as in, e.g. , Majoron models. In
such scenarios, neutrinos still decouple at $T\simeq 1$ MeV, but become tightly
coupled again ('recouple') at later stages of the cosmological evolution. We
use available observations of CMB anisotropies, including Planck 2013 and the
joint BICEP2/Planck 2015 data, to derive constraints on the quantity
$\gamma_{\nu \nu}^4$, parameterizing the neutrino collision rate due to
(pseudo)scalar interactions. We consider both a minimal extension of the
standard $\Lambda$CDM model, and scenarios with extra relativistic species or
non-vanishing tensors. We find a typical constraint $\gamma_{\nu \nu}^4 <
0.9\times 10^{-27}$ (95% C.L.), implying an upper limit on the redshift
$z_{rec}$ of neutrino recoupling $< 8500$. In the framework of Majoron models,
the upper limit on $\gamma_{\nu \nu}$ roughly translates on a constraint $g <
8.2\times 10^{-7}$ on the Majoron-neutrino coupling constant $g$. In general,
the data show a weak ($\sim 1\sigma$) but intriguing preference for non-zero
values of $\gamma_{\nu \nu}^4$, with best fits in the range $\gamma_{\nu \nu}^4
= (0.15 - 0.35)\times 10^{-27}$, depending on the particular dataset. This is
more evident when either observations from ACT and SPT are included, or the
possibility of non-vanishing tensor modes is considered. In particular, for the
minimal model $\Lambda$CDM +$\gamma_{\nu \nu}$ and including the Planck 2013,
ACT and SPT data, we report $\gamma_{\nu \nu}^4=( 0.45^{+0.15}_{-0.38}
)\times10^{-27}$ ($200 < z_{rec} < 5700$) at 68% confidence level. | Secular Aberration Drift and IAU Definition of ICRS: The gravitational attraction of the Galactic centre leads to the centrifugal
acceleration of the Solar system barycentre. It results in secular aberration
drift which displaces the position of the distant radio sources. The effect
should be accounted for in high-precision astrometric reductions as well as by
the corresponding update of the ICRS definition. |
Evolution of the Halpha luminosity function: The Smithsonian Hectospec Lensing Survey (SHELS) is a window on the star
formation history over the last 4 Gyr. SHELS is a spectroscopically complete
survey for Rtot < 20.3 over 4 square degrees. We use the 10k spectra to select
a sample of pure star forming galaxies based on their Halpha emission line. We
use the spectroscopy to determine extinction corrections for individual
galaxies and to remove active galaxies in order to reduce systematic
uncertainties. We use the large volume of SHELS with the depth of a narrowband
survey for Halpha galaxies at z ~ 0.24 to make a combined determination of the
Halpha luminosity function at z ~ 0.24. The large area covered by SHELS yields
a survey volume big enough to determine the bright end of the Halpha luminosity
function from redshift 0.100 to 0.377 for an assumed fixed faint-end slope
alpha = -1.20. The bright end evolves: the characteristic luminosity L*
increases by 0.84 dex over this redshift range. Similarly, the star formation
density increases by 0.11 dex. The fraction of galaxies with a close neighbor
increases by a factor of 2-5 for L(Halpha) >~ L* in each of the redshift bins.
We conclude that triggered star formation is an important influence for star
forming galaxies with Halpha emission. | Strongly lensed supernovae as a self-sufficient probe of the distance
duality relation: The observation of strongly lensed Type Ia supernovae enables both the
luminosity and angular diameter distance to a source to be measured
simultaneously using a single observation. This feature can be used to measure
the distance duality parameter $\eta(z)$ without relying on multiple datasets
and cosmological assumptions to reconstruct the relation between angular and
luminosity distances. In this paper, we show how this can be achieved by future
observations of strongly lensed Type Ia systems. Using simulated datasets, we
reconstruct the function $\eta(z)$ using both parametric and non-parametric
approaches, focusing on Genetic Algorithms and Gaussian processes for the
latter. In the parametric approach, we find that in the realistic scenario of
$N_{\rm lens}=20$ observed systems, the parameter $\epsilon_0$ used to describe
the trend of $\eta(z)$ can be constrained with the precision achieved by
current SNIa and BAO surveys, while in the futuristic case ($N_{\rm
lens}=1000$) these observations could be competitive with the forecast
precision of upcoming LSS and SN surveys. Using the machine learning approaches
of Genetic Algorithms and Gaussian processes, we find that both reconstruction
methods are generally well able to correctly recover the underlying fiducial
model in the mock data, even in the realistic case of $N_{\rm lens}=20$. Both
approaches learn effectively from the features of the mock data points,
yielding $1\sigma$ constraints that are in excellent agreement with the
parameterised results. |
BeyondPlanck X. Planck LFI frequency maps with sample-based error
propagation: We present Planck LFI frequency sky maps derived within the BeyondPlanck
framework. This framework draws samples from a global posterior distribution
that includes instrumental, astrophysical and cosmological parameters, and the
main product is an entire ensemble of frequency sky map samples. This ensemble
allows for computationally convenient end-to-end propagation of low-level
instrumental uncertainties into higher-level science products. We show that the
two dominant sources of LFI instrumental systematic uncertainties are
correlated noise and gain fluctuations, and the products presented here support
- for the first time - full Bayesian error propagation for these effects at
full angular resolution. We compare our posterior mean maps with traditional
frequency maps delivered by the Planck collaboration, and find generally good
agreement. The most important quality improvement is due to significantly lower
calibration uncertainties in the new processing, as we find a fractional
absolute calibration uncertainty at 70 GHz of $\delta g_{0}/g_{0} =5 \cdot
10^{-5}$, which is nominally 40 times smaller than that reported by Planck
2018. However, the original Planck 2018 estimate has a non-trivial statistical
interpretation, and this further illustrates the advantage of the new framework
in terms of producing self-consistent and well-defined error estimates of all
involved quantities without the need of ad hoc uncertainty contributions. We
describe how low-resolution data products, including dense pixel-pixel
covariance matrices, may be produced directly from the posterior samples
without the need for computationally expensive analytic calculations or
simulations. We conclude that posterior-based frequency map sampling provides
unique capabilities in terms of low-level systematics modelling and error
propagation, and may play an important role for future CMB B-mode experiments.
(Abridged.) | On the Diffuse Lyman-alpha Halo Around Lyman-alpha Emitting Galaxies: Ly$\alpha$ photons scattered by neutral hydrogen atoms in the circumgalactic
media or produced in the halos of star-forming galaxies are expected to lead to
extended Ly$\alpha$ emission around galaxies. Such low surface brightness
Ly$\alpha$ halos (LAHs) have been detected by stacking Ly$\alpha$ images of
high-redshift star-forming galaxies. We study the origin of LAHs by performing
radiative transfer modeling of nine $z=3.1$ Lyman-Alpha Emitters (LAEs) in a
high resolution hydrodynamic cosmological galaxy formation simulation. We
develop a method of computing the mean Ly$\alpha$ surface brightness profile of
each LAE by effectively integrating over many different observing directions.
Without adjusting any parameters, our model yields an average Ly$\alpha$
surface brightness profile in remarkable agreement with observations. We find
that observed LAHs cannot be accounted for solely by photons originating from
the central LAE and scattered to large radii by hydrogen atoms in the
circumgalactic gas. Instead, Ly$\alpha$ emission from regions in the outer halo
is primarily responsible for producing the extended LAHs seen in observations,
which potentially includes both star-forming and cooling radiation. With the
limit on the star formation contribution set by the ultra-violet (UV) halo
measurement, we find that cooling radiation can play an important role in
forming the extended LAHs. We discuss the implications and caveats of such a
picture. |
The cosmic lithium problem: an observer's perspective: Using the cosmological constants derived from WMAP, the standard big bang
nucleosynthesis (SBBN) predicts the light elements primordial abundances for
4He, 3He, D, 6Li and 7Li. These predictions are in satisfactory agreement with
the observations, except for lithium which displays in old warm dwarfs an
abundance depleted by a factor of about 3. Depletions of this fragile element
may be produced by several physical processes, in different stellar
evolutionary phases, they will be briefly reviewed here, none of them seeming
yet to reproduce the observed depletion pattern in a fully convincing way. | Probing the statistical isotropy of the universe with Planck data of the
cosmic microwave background: We study the angular distribution of temperature fluctuations in the cosmic
microwave background (CMB) to probe the statistical isotropy of the universe by
using precise full-sky CMB data with a model-independent approach. We
investigated the temperature-temperature angular correlations in the four
Planck foreground-cleaned CMB maps that were released recently. We performed a
directional analysis on the CMB sphere to search directions in which the
temperature-temperature angular correlations are extreme. Our analyses confirm
a preferred axis in the CMB sphere, pointing in the direction $(l,b) \simeq
(260^{\circ}, 130^{\circ})$, at the $98\% -99\%$ confidence level. In this
direction, the CMB angular correlations exceed the antipodal direction most
strongly. This preferred direction is unexpected in the $\Lambda$CDM
cosmological model and represents a significant deviation from results obtained
by applying the same procedure to simulated statistically isotropic CMB maps.
This result confirms the north-south asymmetry in the most recent Planck data.
This phenomenon is one of the previously reported CMB anomalies. We performed a
robust detection of the north-south asymmetry in the temperature-temperature
angular correlations, with a slightly different statistical significance, in
the four Planck foreground-cleaned CMB maps. Moreover, we performed consistency
tests by adding foreground and noise, both Planck data products, to the CMB map
we studied, and we also investigated and discarded possible bias in our method.
After these detailed analyses, we conclude that the north-south asymmetry
phenomenon is present with a high statistical significance in the Planck CMB
maps we studied. This result confirms previous reports in the literature in the
past 20 years. |
Non-linear statistics of primordial black holes from gaussian curvature
perturbations: We develop the non-linear statistics of primordial black holes generated by a
gaussian spectrum of primordial curvature perturbations. This is done by
employing the compaction function as the main statistical variable under the
constraints that: a) the over-density has a high peak at a point $\vec{x}_0$,
b) the compaction function has a maximum at a smoothing scale $R$, and finally,
c) the compaction function amplitude at its maximum is higher than the
threshold necessary to trigger a gravitational collapse into a black hole of
the initial over-density. Our calculation allows for the fact that the patches
which are destined to form PBHs may have a variety of profile shapes and sizes.
The predicted PBH abundances depend on the power spectrum of primordial
fluctuations. For a very peaked power spectrum, our non-linear statistics, the
one based on the linear over-density and the one based on the use of curvature
perturbations, all predict a narrow distribution of PBH masses and comparable
abundance. For broader power spectra the linear over-density statistics
over-estimate the abundance of primordial black holes while the curvature-based
approach under-estimates it. Additionally, for very large smoothing scales, the
abundance is no longer dominated by the contribution of a mean over-density but
rather by the whole statistical realisations of it. | X-ray Point Sources and Radio Galaxies in Clusters of Galaxies: Using Chandra imaging spectroscopy and VLA L-band maps, we have identified
radio galaxies at P(1.4 GHz) >= 3x10^{23} W Hz^{-1} and X-ray point sources
(XPSs) at L(0.3-8 keV) >= 10^{42} ergs s^{-1} in 11 moderate redshift
(0.2<z<0.4) clusters of galaxies. Each cluster is uniquely chosen to have a
total mass similar to predicted progenitors of the present-day Coma Cluster.
Within a projected radius of 1 Mpc we detect 20 radio galaxies and 8 XPSs
confirmed to be cluster members above these limits. 75% of these are detected
within 500 kpc of the cluster center. This result is inconsistent with a random
selection from bright, red sequence ellipticals at the > 99.999% level. All but
one of the XPSs are hosted by luminous ellipticals which otherwise show no
other evidence for AGN activity. These objects are unlikely to be highly
obscured AGN since there is no evidence for large amounts of X-ray or optical
absorption. The most viable model for these sources are low luminosity BL Lac
Objects. The expected numbers of lower luminosity FR 1 radio galaxies and BL
Lacs in our sample converge to suggest that very deep radio and X-ray images of
rich clusters will detect AGN in a large fraction of bright elliptical galaxies
in the inner 500 kpc. Because both the radio galaxies and the XPSs possess
relativistic jets, they can inject heat into the ICM. Using the most recent
scalings of P_jet ~ L_radio^{0.5} from Birzan et al. (2008), radio sources
weaker than our luminosity limit probably contribute the majority of the heat
to the ICM. If a majority of ICM heating is due to large numbers of low power
radio sources, triggered into activity by the increasing ICM density as they
move inward, this may be the feedback mechanism necessary to stabilize cooling
in cluster cores. |
Dynamics of Lyman Break Galaxies and Their Host Halos: We present deep two-dimensional spectra of 22 candidate and confirmed Lyman
break galaxies (LBGs) at redshifts 2<z<4 in the Hubble Deep Field (HDF)
obtained at the Keck II telescope. The targets were preferentially selected
with spatial extent and/or multiple knot morphologies, and we used slitmasks
and individual slits tilted to optimize measurement of any spatially resolved
kinematics. The median target magnitude was I_814=25.3, and total exposure
times ranged from 10 to 50 ks. We measure redshifts, some new, ranging from
z=0.2072 to z=4.056, including two interlopers at z<1, and resulting in a
sample of 14 LBGs with a median redshift z=2.424. The morphologies and
kinematics of the close pairs and multiple knot sources in our sample are
generally inconsistent with galaxy formation scenarios postulating that LBGs
occur only at the bottom of the potential wells of massive host halos; rather,
they support ``collisional starburst'' models with significant major merger
rates and a broad halo occupation distribution. For 13 LBGs with possible
kinematic signatures, we estimate simple dynamical masses ranging from 4e9 h^-1
M_sun to 1.1e11 h^-1 M_sun for individual galaxies and from <10e10 h^-1 to
~10^14 h^-1 M_sun with a median value 1e13 h^-1 M_sun for host dark matter
halos. Comparison with a recent numerical galaxy formation model implies that
the pairwise velocities might not reflect true dynamical masses. We compare our
dynamical mass estimates directly to stellar masses and find no evidence for a
strong correlation. The diversity of morphologies and dynamics implies that
LBGs represent a broad range of galaxy or proto-galaxy types in a variety of
evolutionary or merger stages rather than a uniform class with a narrow range
of mass. | The real and apparent convergence of N-body simulations of the dark
matter structures: is the Navarro-Frenk-White profile real?: We consider the reasons why a cuspy NFW-like profile persistently occurs in
N-body simulations, in contradiction to some astronomical observations. The
routine method of testing the convergence of N-body simulations (in particular,
the negligibility of two-body scattering effect) is to find the conditions
under which the shape of the formed structures is insensitive to numerical
parameters. The results obtained with this approach suggest a surprisingly
minor role of the particle collisions: the central density profile remains
untouched and close to NFW, even if the simulation time significantly exceeds
the collisional relaxation time $\tau_r$. We analyze the test body distribution
in the halo center with help of the Fokker-Planck equation. It turns out that
the Fokker-Planck diffusion transforms any reasonable initial distribution into
NFW-like profile $\rho\propto r^{-1}$ in a time shorter than $\tau_r$. On the
contrary, profile $\rho\propto r^{-1}$ should survive much longer, being a sort
of attractor: the Fokker-Planck diffusion is self-compensated in this case.
Thus the test body scattering may create a stable NFW-like pseudosolution that
can be mixed up with the real convergence. This fact might help to eliminate
the well-known 'cusp vs. core' problem. |
No-go guide for late-time solutions to the Hubble tension: Matter
perturbations: The Hubble tension seems to be a crisis with $\sim5\sigma$ discrepancy
between the most recent local distance ladder measurement from type Ia
supernovae calibrated by Cepheids and the global fitting constraint from the
cosmic microwave background data. To narrow down the possible late-time
solutions to the Hubble tension, we have used in a recent study [Phys. Rev. D
105, L021301 (2022)] an improved inverse distance ladder method calibrated by
the absolute measurements of the Hubble expansion rate at high redshifts from
the cosmic chronometer data, and found no appealing evidence for new physics at
the late time beyond the $\Lambda$CDM model characterized by a parametrization
based on the cosmic age. In this paper, we further investigate the perspective
of this improved inverse distance ladder method by including the late-time
matter perturbation growth data. Independent of the dataset choices, model
parametrizations, and diagnostic quantities ($S_8$ and $S_{12}$), the new
physics at the late time beyond the $\Lambda$CDM model is strongly disfavored
so that the previous late-time no-go guide for the Hubble tension is further
strengthened. | The lensing efficiencies of MACS X-ray selected versus RCS optically
selected galaxy clusters: The statistics of strongly lensed arcs in samples of galaxy clusters provide
information on cluster structure that is complementary to that from individual
clusters. However, samples of clusters that have been analyzed to date have
been either small, heterogeneous, or observed with limited angular resolution.
We measure the lensed-arc statistics of 97 clusters imaged at high angular
resolution with the Hubble Space Telescope, identifying lensed arcs using two
automated arc detection algorithms. The sample includes similar numbers of
X-ray selected (MACS) and optically selected (RCS) clusters, and spans cluster
redshifts in the range 0.2 < z < 1. We compile a catalogue of 42 arcs in the
X-ray selected subsample and 7 arcs in the optical subsample. All but five of
these arcs are reported here for the first time. At 0.3 < z < 0.7, the X-ray
selected clusters have a significantly higher mean frequency of arcs, 1.2+/-0.2
per cluster, versus 0.2+/-0.1 in the optical sample. The strikingly different
lensing efficiencies indicate that X-ray clusters trace much larger mass
concentrations, despite the similar optical luminosities of the X-ray and
optical clusters. The mass difference is supported also by the lower space
density of the X-ray clusters, and by the small Einstein radii of the few arcs
in the optical sample. Higher-order effects, such as differences in
concentration or substructure, may also contribute. |
A simplified view of blazars: clearing the fog around long-standing
selection effects: We propose a scenario where blazars are classified as flat-spectrum radio
quasars (FSRQs), BL Lacs, low synchrotron, or high synchrotron peaked objects
according to a varying mix of the Doppler boosted radiation from the jet, the
emission from the accretion disk, the broad line region, and the light from the
host galaxy. In this framework the peak energy of the synchrotron power
(nu_peak) in blazars is independent of source type and of radio luminosity. We
test this new approach, which builds upon unified schemes, using extensive
Monte Carlo simulations and show that it can provide simple answers to a number
of long-standing issues including, amongst others, the different cosmological
evolution of BL Lacs selected in the radio and X-ray bands, the larger nu_peak
values observed in BL Lacs, the fact that high synchrotron peaked blazars are
always of the BL Lac type, and the existence of FSRQ/BL Lac transition objects.
Objects so far classified as BL Lacs on the basis of their observed weak, or
undetectable, emission lines are of two physically different classes:
intrinsically weak lined objects, more common in X-ray selected samples, and
heavily diluted broad lined sources, more frequent in radio selected samples,
which explains some of the confusion in the literature. We also show that
strong selection effects are the main cause of the diversity observed in radio
and X-ray samples, and that the correlation between luminosity and nu_peak,
that led to the proposal of the "blazar sequence", is also a selection effect
arising from the comparison of shallow radio and X-ray surveys, and to the fact
that high nu_peak-high radio power objects have never been considered because
their redshift is not measurable. | Iron and alpha-element Production in the First One Billion Years after
the Big Bang: We present measurements of carbon, oxygen, silicon, and iron in quasar
absorption systems existing when the universe was roughly one billion years
old. We measure column densities in nine low-ionization systems at 4.7 < z <
6.3 using Keck, Magellan, and VLT optical and near-infrared spectra with
moderate to high resolution. The column density ratios among C II, O I, Si II,
and Fe II are nearly identical to sub-DLAs and metal-poor ([M/H] < -1) DLAs at
lower redshifts, with no significant evolution over 2 < z < 6. The estimated
intrinsic scatter in the ratio of any two elements is also small, with a
typical r.m.s. deviation of <0.1 dex. These facts suggest that dust depletion
and ionization effects are minimal in our z > 4.7 systems, as in the
lower-redshift DLAs, and that the column density ratios are close to the
intrinsic relative element abundances. The abundances in our z > 4.7 systems
are therefore likely to represent the typical integrated yields from stellar
populations within the first gigayear of cosmic history. Due to the time limit
imposed by the age of the universe at these redshifts, our measurements thus
place direct constraints on the metal production of massive stars, including
iron yields of prompt supernovae. The lack of redshift evolution further
suggests that the metal inventories of most metal-poor absorption systems at z
> 2 are also dominated by massive stars, with minimal contributions from
delayed Type Ia supernovae or AGB winds. The relative abundances in our systems
broadly agree with those in very metal-poor, non-carbon-enhanced Galactic halo
stars. This is consistent with the picture in which present-day metal-poor
stars were potentially formed as early as one billion years after the Big Bang. |
Radio and mid-infrared identification of BLAST source counterparts in
the Chandra Deep Field South: We have identified radio and/or mid-infrared counterparts to 198 out of 350
sources detected at >=5 sigma over ~ 9 square degrees centered on the Chandra
Deep Field South (CDFS) by the Balloon-borne Large Aperture Submillimeter
Telescope (BLAST) at 250, 350 and 500 um. We have matched 114 of these
counterparts to optical sources with previously derived photometric redshifts
and fitted SEDs to the BLAST fluxes and fluxes at 70 and 160 um acquired with
the Spitzer Space Telescope. In this way, we have constrained dust
temperatures, total far-infrared/sub-millimeter luminosities and star formation
rates for each source. Our findings show that on average, the BLAST sources lie
at significantly lower redshifts and have significantly lower rest-frame dust
temperatures compared to submm sources detected in surveys conducted at 850 um.
We demonstrate that an apparent increase in dust temperature with redshift in
our sample arises as a result of selection effects. Finally, we provide the
full multi-wavelength catalog of >= 5 sigma BLAST sources contained within the
complete ~ 9 square degree survey area. | What is the super-sample covariance? A fresh perspective for
second-order shear statistics: Cosmological analyses of second-order weak lensing statistics require precise
and accurate covariance estimates. These covariances are impacted by two
sometimes neglected terms: A negative contribution to the Gaussian covariance
due to finite survey area and the super-sample covariance (SSC) which for the
power spectrum contains the impact by Fourier modes larger than the survey
window. We show here that these two effects are connected and can be seen as
correction terms to the "large-field-approximation", the asymptotic case of an
infinitely large survey area. We describe the two terms collectively as
"Finite-Field-Terms".
We derive the covariance of second-order shear statistics from first
principles. For this, we use an estimator in real space without relying on an
estimator for the power spectrum. The resulting covariance does not scale
inversely with the survey area, as naively assumed. This scaling is only
correct under the large-field approximation when the contribution of the
finite-field terms tends to zero. Furthermore, all parts of the covariance, not
only the SSC, depend on the power- and trispectrum at all modes, including
those larger than the survey. We also show that it is generally impossible to
transform an estimate for the power spectrum covariance into the covariance of
a real-space statistic. Such a transformation is only possible in the
asymptotic case of the "large-field approximation".
Additionally, we find that the total covariance of a real-space statistic can
be calculated using correlation functions estimates on spatial scales smaller
than the survey window. Consequently, estimating covariances of real-space
statistics, in principle, does not require information on spatial scales larger
than the survey area. We demonstrate that this covariance estimation method is
equivalent to the standard sample covariance method. |
Gas Clumping in the Outskirts of Lambda-CDM Clusters: Recent Suzaku X-ray observations revealed that the observed entropy profile
of the intracluster medium (ICM) deviates significantly from the prediction of
hydrodynamical simulations of galaxy clusters. In this work, we show that gas
clumping introduces significant biases in X-ray measurements of the ICM
profiles in the outskirts of galaxy clusters. Using hydrodynamical simulations
of galaxy cluster formation in a concordance Lambda-CDM model, we demonstrate
that gas clumping leads to an overestimate of the observed gas density and
causes flattening of the entropy profile. Our results suggest that gas clumping
must be taken into account when interpreting X-ray measurements of cluster
outskirts. | A numerical study of primordial magnetic field amplification by
inflation-produced gravitational waves: We numerically study the interaction of inflation-produced magnetic fields
with gravitational waves, both of which originate from quantum fluctuations
during inflation. The resonance between the magnetic field perturbations and
the gravitational waves has been suggested as a possible mechanism for magnetic
field amplification. However, some analytical studies suggest that the effect
of the inflationary gravitational waves is too small to provide significant
amplification. Our numerical study shows more clearly how the interaction
affects the magnetic fields and confirms the weakness of the influence of the
gravitational waves. We present an investigation based on the
magnetohydrodynamic approximation and take into account the differences of the
Alfven speed. |
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses VIII.
Deconvolution of high resolution near-IR images and simple mass models for 7
gravitationally lensed quasars: We apply the iterative MCS deconvolution method (ISMCS) to near-IR HST
archives data of seven gravitationally lensed quasars currently monitored by
the COSMOGRAIL collaboration: HE 0047-1756, RX J1131-1231, SDSS J1138+0314,
SDSS J1155+6346, SDSS J1226-0006, WFI J2026-4536 and HS 2209+1914. In doing so,
we obtain relative positions for the lensed images and shape parameters for the
light distribution of the lensing galaxy in each system. The lensed image
positions are derived with 1-2 mas accuracy. To predict time delays and to test
the ability of simple mass models to reproduce the observed configuration,
isothermal and de Vaucouleurs mass models are calculated for the whole sample
using state-of-the-art modeling techniques. The effect of the lens environment
on the lens mass models is taken into account with a shear term. Doubly imaged
quasars are equally well fitted by each of these models. A large amount of
shear is necessary to reproduce SDSS J1155+6346 and SDSS J1226-006. In the
latter case, we identify a nearby galaxy as the dominant source of shear. The
quadruply imaged quasar SDSS J1138+0314 is well reproduced by simple lens
models, which is not the case for the two other quads, RX J1131-1231 and WFI
J2026-4536. This might be the signature of astrometric perturbations due to
massive substructures in the lensing galaxy unaccounted for by the models.
Other possible explanations are also presented. | Real Space Approach to CMB deboosting: The effect of our Galaxy's motion through the Cosmic Microwave Background
rest frame, which aberrates and Doppler shifts incoming photons measured by
current CMB experiments, has been shown to produce mode-mixing in the multipole
space temperature coefficients. However, multipole space determinations are
subject to many difficulties, and a real-space analysis can provide a
straightforward alternative. In this work we describe a numerical method for
removing Lorentz- boost effects from real-space temperature maps. We show that
to deboost a map so that one can accurately extract the temperature power
spectrum requires calculating the boost kernel at a finer pixelization than one
might naively expect. In idealized cases that allow for easy comparison to
analytic results, we have confirmed that there is indeed mode mixing among the
spherical harmonic coefficients of the temperature. We find that using a boost
kernel calculated at Nside=8192 leads to a 1% bias in the binned boosted power
spectrum at l~2000, while individual Cls exhibit ~5% fluctuations around the
binned average. However, this bias is dominated by pixelization effects and not
the aberration and Doppler shift of CMB photons that causes the fluctuations.
Performing analysis on maps with galactic cuts does not induce any additional
error in the boosted, binned power spectra over the full sky analysis. For
multipoles that are free of resolution effects, there is no detectable
deviation between the binned boosted and unboosted spectra. This result arises
because the power spectrum is a slowly varying function of and does not show
that, in general, Lorentz boosts can be neglected for other cosmological
quantities such as polarization maps or higher-point functions. |
A panchromatic study of BLAST counterparts: total star-formation rate,
morphology, AGN fraction and stellar mass: We carry out a multi-wavelength study of individual galaxies detected by the
Balloon-borne Large Aperture Submillimeter Telescope (BLAST) and identified at
other wavelengths, using data spanning the radio to the ultraviolet (UV). We
develop a Monte Carlo method to account for flux boosting, source blending, and
correlations among bands, which we use to derive deboosted far-infrared (FIR)
luminosities for our sample. We estimate total star-formation rates for BLAST
counterparts with z < 0.9 by combining their FIR and UV luminosities. Star
formation is heavily obscured at L_FIR > 10^11 L_sun, z > 0.5, but the
contribution from unobscured starlight cannot be neglected at L_FIR < 10^11
L_sun, z < 0.25. We assess that about 20% of the galaxies in our sample show
indication of a type-1 active galactic nucleus (AGN), but their submillimeter
emission is mainly due to star formation in the host galaxy. We compute stellar
masses for a subset of 92 BLAST counterparts; these are relatively massive
objects, with a median mass of ~10^11 M_sun, which seem to link the 24um and
SCUBA populations, in terms of both stellar mass and star-formation activity.
The bulk of the BLAST counterparts at z<1 appear to be run-of-the-mill
star-forming galaxies, typically spiral in shape, with intermediate stellar
masses and practically constant specific star-formation rates. On the other
hand, the high-z tail of the BLAST counterparts significantly overlaps with the
SCUBA population, in terms of both star-formation rates and stellar masses,
with observed trends of specific star-formation rate that support strong
evolution and downsizing. | Reconstruction of a direction-dependent primordial power spectrum from
Planck CMB data: We consider the possibility that the primordial curvature perturbation is
direction-dependent. To first order this is parameterised by a quadrupolar
modulation of the power spectrum and results in statistical anisotropy of the
CMB, which can be quantified using `bipolar spherical harmonics'. We compute
these for the Planck DR2-2015 SMICA map and estimate the noise covariance from
Planck Full Focal Plane 9 simulations. A constant quadrupolar modulation is
detected with 2.2 sigma significance, dropping to 2 sigma when the primordial
power is assumed to scale with wave number k as a power law. Going beyond
previous work we now allow the spectrum to have arbitrary scale-dependence. Our
non-parametric reconstruction then suggests several spectral features, the most
prominent at k ~ 0.006/Mpc. When a constant quadrupolar modulation is fitted to
data in the range 0.005 < k Mpc < 0.008, its preferred directions are found to
be related to the cosmic hemispherical asymmetry and the CMB dipole. To
determine the significance we apply two test statistics to our reconstructions
of the quadrupolar modulation from data, against reconstructions of
realisations of noise only. With a test statistic sensitive only to the
amplitude of the modulation, the reconstructions from the multipole range 30 <
l < 1200 are unusual with 2.1 sigma significance. With the second test
statistic, sensitive also to the direction, the significance rises to 6.9
sigma. Our approach is easily generalised to include other data sets such as
polarisation, large-scale structure and forthcoming 21-cm line observations
which will enable these anomalies to be investigated further. |
Spherical collapse and halo abundance in shift-symmetric Galileon theory: We present the nonlinear growth of bound cosmological structures using the
spherical collapse approach in the shift-symmetric Galileon theories. In
particular, we focus on the class of models belonging to the Kinetic Gravity
Braiding by adopting a general parametrization of the action encoding a large
set of models by means of four free parameters: two defining the background
evolution and two affecting the perturbations. For the latter we identify their
specific signatures on the linearised critical density contrast, nonlinear
effective gravitational coupling and the virial overdensity and how they drive
their predictions away from $\Lambda$CDM. We then use the results of the
spherical collapse model to predict the evolution of the halo mass function. We
find that the shift-symmetric model predicts a larger number of objects
compared to $\Lambda$CDM for masses $M \gtrsim 10^{14} h^{-1} \mathrm{M}_\odot$
and such number increases for larger deviations from the standard model.
Therefore, the shift-symmetric model shows detectable signatures which can be
used to distinguish it from the standard scenario. | Cosmological constraints on the neutrino mass including systematic
uncertainties: When combining cosmological and oscillations results to constrain the
neutrino sector, the question of the propagation of systematic uncertainties is
often raised. We address this issue in the context of the derivation of an
upper bound on the sum of the neutrino masses ($\Sigma m_\nu$) with recent
cosmological data. This work is performed within the
${{\mathrm{\Lambda{CDM}}}}$ model extended to $\Sigma m_\nu$, for which we
advocate the use of three mass-degenerate neutrinos. We focus on the study of
systematic uncertainties linked to the foregrounds modelling in CMB data
analysis, and on the impact of the present knowledge of the reionisation
optical depth. This is done through the use of different likelihoods built from
Planck data. Limits on $\Sigma m_\nu$ are derived with various combinations of
data, including the latest Baryon Acoustic Oscillations (BAO) and Type Ia
Supernovae (SN) results. We also discuss the impact of the preference for
current CMB data for amplitudes of the gravitational lensing distortions higher
than expected within the ${{\mathrm{\Lambda{CDM}}}}$ model, and add the Planck
CMB lensing. We then derive a robust upper limit: $\Sigma m_\nu< 0.17\hbox{ eV
at }95\% \hbox{CL}$, including 0.01 eV of foreground systematics. We also
discuss the neutrino mass repartition and show that today's data do not allow
one to disentangle normal from inverted hierarchy. The impact on the other
cosmological parameters is also reported, for different assumptions on the
neutrino mass repartition, and different high and low multipole CMB
likelihoods. |
Distribution of Si, Fe, and Ni in the Intracluster Medium of the Coma
Cluster: We studied the distributions of Si, Fe, and Ni in the intracluster medium
(ICM) of the Coma cluster, one of the largest clusters in the nearby universe,
using XMM-Newton data up to 0.5 r180 and Suzaku data of the central region up
to 0.16 r180. Using the flux ratios of Ly alpha of H-like Si and 7.8 keV blend
to K alpha of He-like Fe, the abundance ratios of Si to Fe and Ni to Fe of the
ICM were derived using APEC model v2.0.1. The Si/Fe ratio in the ICM of the
Coma cluster shows no radial gradient. The emission weighted averages of the
Si/Fe ratio in the ICM within 0.0--0.2 r180, 0.2--0.5 r180, and 0.0--0.5 r180
are 0.97 +- 0.11, 1.05 +- 0.36 and 0.99 +- 0.13, respectively, in solar units
using the solar abundance of Lodders (2003). These values are close to those of
smaller clusters and groups of galaxies. Using the Suzaku data of the central
region, the derived Ni/Fe ratio of the ICM is 0.6--1.5 in solar units,
according to the same solar abundance table. The systematic difference in the
derived abundance ratios by different plasma codes are about 10%. Therefore,
for the ICM in the Coma cluster, the abundance pattern of Si, Fe, and Ni is
consistent with the same mixture of the yields of SN II and SN Ia in our
Galaxy. Within 0.5 r180}, the cumulative iron-mass-to-light ratio increases
with radius, and its radial profile is similar to those of relaxed smaller
clusters with cD galaxies at their center. Considering the observed Si/Fe
ratio, the cumulative metal-mass-to-light ratios at 0.5 r180 are compared with
theoretical expectations. | A Galileon Design of Slow Expansion: We show a model of the slow expansion, in which the scale invariant spectrum
of curvature perturbation is adiabatically induced by its increasing mode, by
applying a generalized Galileon field. In this model, initially \epsilon << -1,
which then is rapidly increasing, during this period the universe is slowly
expanding. There is not the ghost instability, the perturbation theory is
healthy. When \epsilon \sim -1, the slow expansion phase ends, and the
available energy of field can be released and the universe reheats. This
scenario might be a viable design of the early universe. |
The ISW effect and the lack of large-angle CMB temperature correlations: It is by now well established that the magnitude of the two-point
angular-correlation function of the cosmic microwave background temperature
anisotropies is anomalously low for angular separations greater than about 60
degrees. Physics explanations of this anomaly typically focus on the properties
of the Universe at the surface of last scattering, relying on the fact that
large-angle temperature fluctuations are dominated by the Sachs-Wolfe effect
(SW). However, these fluctuations also receive important contributions from the
integrated Sachs-Wolfe effect (ISW) at both early (eISW) and late ($\ell$ISW)
times. Here we study the correlations in those large-angle temperature
fluctuations and their relative contributions to $S_{1/2}$ -- the standard
measure of the correlations on large angular scales. We find that in the
best-fitting $\Lambda$CDM cosmology, while the auto-correlation of the early
contributions (SW plus eISW) dominates $S_{1/2}$, there are also significant
contributions originating from cross-terms between the early and late
contributions. In particular, realizations of $\Lambda$CDM with low $S_{1/2}$
are typically produced from a combination of somewhat low pure-early
correlations and accidental cancellations among early-late correlations. We
also find that if the pure $\ell$ISW auto-correlations were the only
contribution to $S_{1/2}$ in $\Lambda$CDM, then the $p$-value of the observed
cut-sky $S_{1/2}$ would be unremarkable. This suggests that physical mechanisms
operating only at or near the last scattering surface could explain the
observed lack of large-angle correlations, though this is not the typical
resolution within $\Lambda$CDM. | On Modeling and Measuring the Temperature of the z~5 IGM: The temperature of the low-density intergalactic medium (IGM) at high
redshift is sensitive to the timing and nature of hydrogen and HeII
reionization, and can be measured from Lyman-alpha forest absorption spectra.
Since the memory of intergalactic gas to heating during reionization gradually
fades, measurements as close as possible to reionization are desirable. In
addition, measuring the IGM temperature at sufficiently high redshifts should
help to isolate the effects of hydrogen reionization since HeII reionization
starts later, at lower redshift. Motivated by this, we model the IGM
temperature at z>5 using semi-numeric models of patchy reionization. We
construct mock Lyman-alpha forest spectra from these models and consider their
observable implications. We find that the small-scale structure in the
Lyman-alpha forest is sensitive to the temperature of the IGM even at redshifts
where the average absorption in the forest is as high as 90%. We forecast the
accuracy at which the z~5 IGM temperature can be measured using existing
samples of high resolution quasar spectra, and find that interesting
constraints are possible. For example, an early reionization model in which
reionization ends at z~10 should be distinguishable -- at high statistical
significance -- from a lower redshift model where reionization completes at
z~6. We discuss improvements to our modeling that may be required to robustly
interpret future measurements. |
Identifying Variations to the IMF at High-$z$ Through Deep Radio Surveys: In this article I briefly describe how deep radio surveys may provide a means
to identify variations in the upper end of the initial mass function (IMF) in
star-forming galaxies at high redshifts (i.e., $z\gtrsim$3). At such high
redshifts, I argue that deep radio continuum observations at frequencies
$\gtrsim$10 GHz using next generation facilities (e.g., EVLA, MeerKAT, SKA/NAA)
will likely provide the most accurate measurements for the ionizing photon
rates (star formation rates; SFRs) of normal galaxies since their non-thermal
emission should be highly suppressed due to the increased inverse Compton (IC)
losses from the cosmic microwave background (CMB), leaving only thermal
(free-free) emission detectable. Thus, a careful analysis of such observations
in combination with future ALMA and JWST data, measuring the rest-frame
far-infrared and UV emission from the same population of galaxies, may yield
the best means to search for variability in the stellar IMF at such epochs. | Harmonic in-painting of CMB sky by constrained Gaussian realization: The presence of astrophysical emissions between the last scattering surface
and our vantage point requires us to apply a foreground mask on CMB sky map,
leading to large cut around the Galactic equator and numerous holes. Since many
CMB analyses, including non-Gaussianity study may be performed on a whole sky
map in a more straightforward and reliable manner, it is of utmost importance
to develop an efficient method to in-paint the CMB sky map, while still
preserving statistical properties. In this letter, we consider Monte-Carlo
simulation of constrained Gaussian field and derive it for CMB anisotropy in
harmonic space, where a feasible implementation is possible with good
approximation. We applied our method to the simulated data, which confirms the
masked area is in-painted in a way compliant with the expected statistical
properties. Subsequently, we applied our method to the WMAP foreground-reduced
maps and investigated the anomalous alignment between quadrupole and octupole
components. From our investigation, we find the alignment in the
foreground-reduced maps is even higher than the ILC map. In particular, we find
the highest alignment in the V band map, which has less foreground
contamination than other bands. Therefore, we find it hard to attribute the
alignment to residual foregrounds. Our method will be complementary to other
efforts on in-painting or reconstructing the masked CMB data, and of great use
to Planck surveyor and future missions. |
Subsets and Splits
No saved queries yet
Save your SQL queries to embed, download, and access them later. Queries will appear here once saved.