63 research outputs found
Baryonic Imprints on DM Halos: The concentration-mass relation in the CAMELS simulations
The physics of baryons in halos, and their subsequent influence on the total
matter phase space, has a rich phenomenology and must be well understood in
order to pursue a vast set of questions in both cosmology and astrophysics. We
use the CAMELS simulation suite to quantify the impact of four different galaxy
formation parameters/processes (as well as two cosmological parameters) on the
concentration-mass relation, . We construct a
simulation-informed nonlinear model for concentration as a function of halo
mass, redshift, and 6 cosmological/astrophysical parameters. This is done for
two galaxy formation models, IllustrisTNG and SIMBA, using 1000 simulations of
each. We extract the imprints of galaxy formation across a wide range in mass
and in redshift finding many strong mass- and redshift-dependent features. Comparisons
between the IllustrisTNG and SIMBA results show the astrophysical model choices
cause significant differences in the mass and redshift dependence of these
baryon imprints. Finally, we use existing observational measurements of to provide rough limits on the four astrophysical
parameters. Our nonlinear model is made publicly available and can be used to
include CAMELS-based baryon imprints in any halo model-based analysis.Comment: [v1]: 8 figures, 14 page
Detecting deviations from Gaussianity in high-redshift CMB lensing maps
While the probability density function (PDF) of the cosmic microwave
background (CMB) convergence field approximately follows a Gaussian
distribution, small contributions from structures at low redshifts make the
overall distribution slightly non-Gaussian. Some of this late-time component
can be modelled using the distribution of galaxies and subtracted off from the
original CMB lensing map to produce a map of matter distribution at high
redshifts. Using this high-redshift mass map, we are able to directly study the
early phases of structure formation and look for deviations from our standard
model. In this work, we forecast the detectability of signatures of
non-Gaussianity due to nonlinear structure formation at . Although we
find that detecting such signatures using ongoing surveys will be challenging,
we forecast that future experiments such as the CMB-S4 will be able to make
detections of 7.Comment: 9 pages, 9 figures. Comments welcom
Calibrated Ultra Fast Image Simulations for the Dark Energy Survey
Weak lensing by large-scale structure is a powerful technique to probe the
dark components of the universe. To understand the measurement process of weak
lensing and the associated systematic effects, image simulations are becoming
increasingly important. For this purpose we present a first implementation of
the (; Refregier & Amara
2014), a coherent framework for studying systematic effects in weak lensing. It
allows us to model and calibrate the shear measurement process using image
simulations from the Ultra Fast Image Generator (UFig; Berge et al. 2013). We
apply this framework to a subset of the data taken during the Science
Verification period (SV) of the Dark Energy Survey (DES). We calibrate the UFig
simulations to be statistically consistent with DES images. We then perform
tolerance analyses by perturbing the simulation parameters and study their
impact on the shear measurement at the one-point level. This allows us to
determine the relative importance of different input parameters to the
simulations. For spatially constant systematic errors and six simulation
parameters, the calibration of the simulation reaches the weak lensing
precision needed for the DES SV survey area. Furthermore, we find a sensitivity
of the shear measurement to the intrinsic ellipticity distribution, and an
interplay between the magnitude-size and the pixel value diagnostics in
constraining the noise model. This work is the first application of the
framework to data and shows how it can be used to methodically
study the impact of systematics on the cosmic shear measurement.Comment: 14 pages, 9 Figures, submitted to Ap
A Multi-Chamber System for Analyzing the Outgassing, Deposition, and Associated Optical Degradation Properties of Materials in a Vacuum
We report on the Camera Materials Test Chamber, a multi-vessel apparatus
which analyzes the outgassing consequences of candidate materials for use in
the vacuum cryostat of a new telescope camera. The system measures the
outgassing products and rates of samples of materials at different
temperatures, and collects films of outgassing products to measure the effects
on light transmission in six optical bands. The design of the apparatus
minimizes potential measurement errors introduced by background contamination.Comment: 9 pages, 10 figures, published in RSI (minor edits made to match
journal accepted version
An Integrated System at the Bleien Observatory for Mapping the Galaxy
We describe the design and performance of the hardware system at the Bleien
Observatory. The system is designed to deliver a map of the Galaxy for studying
the foreground contamination of low-redshift (z=0.13--0.43) H
intensity mapping experiments as well as other astronomical Galactic studies.
This hardware system is composed of a 7m parabolic dish, a dual-polarization
corrugated horn feed, a pseudo correlation receiver, a Fast Fourier Transform
spectrometer, and an integrated control system that controls and monitors the
progress of the data collection. The main innovative designs in the hardware
are (1) the pseudo correlation receiver and the cold reference source within
(2) the high dynamic range, high frequency resolution spectrometer and (3) the
phase-switch implementation of the system. This is the first time these
technologies are used together for a L-band radio telescope to achieve an
electronically stable system, which is an essential first step for wide-field
cosmological measurements. This work demonstrates the prospects and challenges
for future H intensity mapping experiments.Comment: 11 pages, 12 figures, 1 table, Submitted to MNRA
The Effect of Splashback on Weak Lensing Mass Estimates of Galaxy Clusters and Groups
The splashback radius of a dark matter halo, which corresponds to the first
apocenter radius reached by infalling matter and substructures, has been
detected around galaxy clusters using a multitude of observational methods,
including weak lensing measurements. In this manuscript, we present how the
splashback feature in the halo density profile affects galaxy cluster masses
derived through weak lensing measurements if it is not accounted for. We find
that the splashback radius has an increasingly large effect on group-sized
halos towards . Depending on the
model and the radial scale used, the cluster/group masses can be biased low by
more than 0.1 dex. This bias, in turn, would result in a slightly lower
value if propagated into a cluster cosmology analysis. The
splashback effect with group-sized dark matter halos may become important to
consider, given the increasingly stringent cosmological constraints coming from
optical wide-field surveys
The Halo Boundary of Galaxy Clusters in the SDSS
Mass around dark matter halos can be divided into "infalling" material and
"collapsed" material that has passed through at least one pericenter.
Analytical models and simulations predict a rapid drop in the halo density
profile associated with the transition between these two regimes. Using data
from SDSS, we explore the evidence for such a feature in the density profiles
of galaxy clusters and investigate the connection between this feature and a
possible phase space boundary. We first estimate the steepening of the outer
galaxy density profile around clusters: the profiles show an abrupt steepening,
providing evidence for truncation of the halo profile. Next, we measure the
galaxy density profile around clusters using two sets of galaxies selected
based on color. We find evidence of an abrupt change in the galaxy colors that
coincides with the location of the steepening of the density profile. Since
galaxies are likely to be quenched of star formation and turn red inside of
clusters, this change in the galaxy color distribution can be interpreted as
the transition from an infalling regime to a collapsed regime. We also measure
this transition using a model comparison approach which has been used recently
in studies of the "splashback" phenomenon, but find that this approach is not a
robust way to quantify the significance of detecting a splashback-like feature.
Finally, we perform measurements using an independent cluster catalog to test
for potential systematic errors associated with cluster selection. We identify
several avenues for future work: improved understanding of the small-scale
galaxy profile, lensing measurements, identification of proxies for the halo
accretion rate, and other tests. With upcoming data from the DES, KiDS and HSC
surveys, we can expect significant improvements in the study of halo
boundaries.Comment: 17 pages, 8 figure
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