45 research outputs found
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
CLUMP-3D. Testing CDM with galaxy cluster shapes
The CDM model of structure formation makes strong predictions on
concentration and shape of DM (dark matter) halos, which are determined by mass
accretion processes. Comparison between predicted shapes and observations
provides a geometric test of the CDM model. Accurate and precise
measurements needs a full three-dimensional analysis of the cluster mass
distribution. We accomplish this with a multi-probe 3D analysis of the X-ray
regular CLASH (Cluster Lensing And Supernova survey with Hubble) clusters
combining strong and weak lensing, X-ray photometry and spectroscopy, and the
Sunyaev-Zel'dovich effect. The cluster shapes and concentrations are consistent
with CDM predictions. The CLASH clusters are randomly oriented, as
expected given the sample selection criteria. Shapes agree with numerical
results for DM-only halos, which hints at baryonic physics being not so
effective in making halos rounder.Comment: v2: 8 pages, in press on ApJL. Extended discussion on regularity. One
of three new companion papers of the CLUMP-3D project (Keiichi Umetsu et al.,
arxiv:1804.00664; I-Non Chiu et al., arXiv:1804.00676
CLUMP-3D: three-dimensional lensing and multi-probe analysis of MACS J1206.2−0847, a remarkably regular cluster
Multi-wavelength techniques can probe the distribution and the physical properties of baryons and dark matter in galaxy clusters from the inner regions out to the peripheries. We present a full three-dimensional analysis combining strong and weak lensing, X-ray surface brightness and temperature, and the Sunyaev–Zel'dovich effect. The method is applied to MACS J1206.2−0847, a remarkably regular, face-on, massive, M_(200) = (1.1 ± 0.2) × 10^(15) M⊙ h^(−1), cluster at z = 0.44. The measured concentration, c_(200) = 6.3 ± 1.2, and the triaxial shape are common to haloes formed in a Λ cold dark matter scenario. The gas has settled in and follows the shape of the gravitational potential, which is evidence of pressure equilibrium via the shape theorem. There is no evidence for significant non-thermal pressure and the equilibrium is hydrostatic
CLUMP-3D: Three-dimensional Shape and Structure of 20 CLASH Galaxy Clusters from Combined Weak and Strong Lensing
We perform a three-dimensional triaxial analysis of 16 X-ray regular and 4
high-magnification galaxy clusters selected from the CLASH survey by combining
two-dimensional weak-lensing and central strong-lensing constraints. In a
Bayesian framework, we constrain the intrinsic structure and geometry of each
individual cluster assuming a triaxial Navarro-Frenk-White halo with arbitrary
orientations, characterized by the mass , halo concentration
, and triaxial axis ratios (), and investigate scaling relations between these halo
structural parameters. From triaxial modeling of the X-ray-selected subsample,
we find that the halo concentration decreases with increasing cluster mass,
with a mean concentration of at the pivot
mass . This is consistent with the
result from spherical modeling, . Independently
of the priors, the minor-to-major axis ratio of our full
sample exhibits a clear deviation from the spherical configuration
( at with uniform
priors), with a weak dependence on the cluster mass. Combining all 20 clusters,
we obtain a joint ensemble constraint on the minor-to-major axis ratio of
and a lower bound on the
intermediate-to-major axis ratio of at the
level from an analysis with uniform priors. Assuming priors on the axis ratios
derived from numerical simulations, we constrain the degree of triaxiality for
the full sample to be at ,
indicating a preference for a prolate geometry of cluster halos. We find no
statistical evidence for an orientation bias ()
(abridged)Comment: Accepted by the ApJ. This is one of the three companion papers,
including Umetsu et al. 2018 (arXiv:1804.00664) and Sereno et al. 2018
(arXiv:1804.00667), in the CLUMP-3D project. Go go go, HoHo