71 research outputs found
Impact of Weak Lensing Mass Calibration on eROSITA Galaxy Cluster Cosmological Studies -- a Forecast
We forecast the impact of weak lensing (WL) cluster mass calibration on the
cosmological constraints from the X-ray selected galaxy cluster counts in the
upcoming eROSITA survey. We employ a prototype cosmology pipeline to analyze
mock cluster catalogs. Each cluster is sampled from the mass function in a
fiducial cosmology and given an eROSITA count rate and redshift, where count
rates are modeled using the eROSITA effective area, a typical exposure time,
Poisson noise and the scatter and form of the observed X-ray luminosity-- and
temperature--mass--redshift relations. A subset of clusters have mock shear
profiles to mimic either those from DES and HSC or from the future Euclid and
LSST surveys. Using a count rate selection, we generate a baseline cluster
cosmology catalog that contains 13k clusters over 14,892~deg of
extragalactic sky. Low mass groups are excluded using raised count rate
thresholds at low redshift. Forecast parameter uncertainties for
, and are 0.023 (0.016; 0.014), 0.017 (0.012;
0.010), and 0.085 (0.074; 0.071), respectively, when adopting DES+HSC WL
(Euclid; LSST), while marginalizing over the sum of the neutrino masses. A
degeneracy between the distance--redshift relation and the parameters of the
observable--mass scaling relation limits the impact of the WL calibration on
the constraints, but with BAO measurements from DESI an improved
determination of to 0.043 becomes possible. With Planck CMB priors,
() can be determined to (), and the
summed neutrino mass limited to eV (at 95\%). If
systematics on the group mass scale can be controlled, the eROSITA group and
cluster sample with 43k objects and LSST WL could constrain
and to 0.007 and to 0.050.Comment: 28 pages, 13 figur
Cosmological Constraints from Galaxy Clusters and Groups in the eROSITA Final Equatorial Depth Survey
We present the first cosmological study of a sample of clusters,
which were identified in the Final Equatorial Depth Survey (eFEDS).
In a joint selection on X-ray and optical observables, the sample contains
clusters within a redshift range of , of which systems
are covered by the public data from the Hyper Suprime-Cam (HSC) survey that
enables uniform weak-lensing cluster mass constraints. With minimal
assumptions, at each cluster redshift we empirically model (1) the scaling
relations between the cluster halo mass and the observables, which include the
X-ray count rate, the optical richness, and the weak-lensing mass, and (2) the
X-ray selection in terms of the completeness function . Using the
richness distribution of the clusters, we directly measure the X-ray
completeness and adopt those measurements as informative priors for the
parameters of . In a blinded analysis, we obtain the cosmological
constraints , and
in a flat CDM cosmology. Extending to a flat CDM cosmology leads to
the constraint on the equation of state parameter of the dark energy of . The eFEDS constraints are in good agreement with the results
from the mission, the galaxy-galaxy lensing and clustering analysis of
the Dark Energy Survey, and the cluster abundance analysis of the SPT-SZ survey
at a level of . With the empirical modelling, this work
presents the first fully self-consistent cosmological constraints based on a
synergy between wide-field X-ray and weak lensing surveys.Comment: Accepted for publication in MNRAS. Figures 18 and 19 contain the main
results. Chains and cluster masses are at
https://github.com/inonchiu/eFEDSproduct
Is graphene on Ru(0001) a nanomesh?
The electronic structure of a single layer graphene on Ru(0001) is compared
with that of a single layer hexagonal boron nitride nanomesh on Ru(0001). Both
are corrugated sp2 networks and display a pi-band gap at the K point of their 1
x 1 Brillouin zone. Graphene has a distinct Fermi surface which indicates that
0.1 electrons are transferred per 1 x 1 unit cell. Photoemission from adsorbed
xenon identifies two distinct Xe 5p1/2 lines, separated by 240 meV, which
reveals a corrugated electrostatic potential energy surface. These two Xe
species are related to the topography of the system and have different
desorption energies.Comment: 5 pages, 4 figures, 1 tabl
Velocity Segregation and Systematic Biases In Velocity Dispersion Estimates With the SPT-GMOS Spectroscopic Survey
The velocity distribution of galaxies in clusters is not universal; rather,
galaxies are segregated according to their spectral type and relative
luminosity. We examine the velocity distributions of different populations of
galaxies within 89 Sunyaev Zel'dovich (SZ) selected galaxy clusters spanning . Our sample is primarily draw from the SPT-GMOS spectroscopic
survey, supplemented by additional published spectroscopy, resulting in a final
spectroscopic sample of 4148 galaxy spectra---2868 cluster members. The
velocity dispersion of star-forming cluster galaxies is % greater than
that of passive cluster galaxies, and the velocity dispersion of bright () cluster galaxies is % lower than the velocity dispersion of
our total member population. We find good agreement with simulations regarding
the shape of the relationship between the measured velocity dispersion and the
fraction of passive vs. star-forming galaxies used to measure it, but we find a
small offset between this relationship as measured in data and simulations in
which suggests that our dispersions are systematically low by as much as 3\%
relative to simulations. We argue that this offset could be interpreted as a
measurement of the effective velocity bias that describes the ratio of our
observed velocity dispersions and the intrinsic velocity dispersion of dark
matter particles in a published simulation result. Measuring velocity bias in
this way suggests that large spectroscopic surveys can improve dispersion-based
mass-observable scaling relations for cosmology even in the face of velocity
biases, by quantifying and ultimately calibrating them out.Comment: Accepted to ApJ; 21 pages, 11 figures, 5 table
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
CMB-S4---the next-generation ground-based cosmic microwave background (CMB)
experiment---is set to significantly advance the sensitivity of CMB
measurements and enhance our understanding of the origin and evolution of the
Universe, from the highest energies at the dawn of time through the growth of
structure to the present day. Among the science cases pursued with CMB-S4, the
quest for detecting primordial gravitational waves is a central driver of the
experimental design. This work details the development of a forecasting
framework that includes a power-spectrum-based semi-analytic projection tool,
targeted explicitly towards optimizing constraints on the tensor-to-scalar
ratio, , in the presence of Galactic foregrounds and gravitational lensing
of the CMB. This framework is unique in its direct use of information from the
achieved performance of current Stage 2--3 CMB experiments to robustly forecast
the science reach of upcoming CMB-polarization endeavors. The methodology
allows for rapid iteration over experimental configurations and offers a
flexible way to optimize the design of future experiments given a desired
scientific goal. To form a closed-loop process, we couple this semi-analytic
tool with map-based validation studies, which allow for the injection of
additional complexity and verification of our forecasts with several
independent analysis methods. We document multiple rounds of forecasts for
CMB-S4 using this process and the resulting establishment of the current
reference design of the primordial gravitational-wave component of the Stage-4
experiment, optimized to achieve our science goals of detecting primordial
gravitational waves for at greater than , or, in the
absence of a detection, of reaching an upper limit of at CL.Comment: 24 pages, 8 figures, 9 tables, submitted to ApJ. arXiv admin note:
text overlap with arXiv:1907.0447
Snowmass 2021 CMB-S4 White Paper
This Snowmass 2021 White Paper describes the Cosmic Microwave Background Stage 4 project CMB-S4, which is designed to cross critical thresholds in our understanding of the origin and evolution of the Universe, from the highest energies at the dawn of time through the growth of structure to the present day. We provide an overview of the science case, the technical design, and project plan
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