Cosmological constraints from galaxy clusters and groups in the eROSITA final equatorial depth survey
Abstract
We present the first cosmological study of a sample of eROSITA clusters, which were identified in the eROSITA Final Equatorial Depth Survey (eFEDS). In a joint selection on Xray and optical observables, the sample contains 455 clusters within a redshift range of 0.1 < z < 1.2, of which 177 systems are covered by the public data from the Hyper SuprimeCam (HSC) survey that enables uniform weaklensing 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 Xray count rate, the optical richness, and the weaklensing mass, and (2) the Xray selection in terms of the completeness function $\mathcal {C}$. Using the richness distribution of the clusters, we directly measure the Xray completeness and adopt those measurements as informative priors for the parameters of $\mathcal {C}$. In a blinded analysis, we obtain the cosmological constraints $\Omega _{\mathrm{m}}= 0.245^{+0.048}_{0.058}$, $\sigma _{8}= 0.833^{+0.075}_{0.063}$, and $S_{8}\equiv \sigma _{8}\left(\Omega _{\mathrm{m}}/0.3\right)^{0.3}= 0.791^{+0.028}_{0.031}$ in a flat ΛCDM cosmology. Extending to a flat wCDM cosmology leads to the constraint on the equation of state parameter of the dark energy of w = 1.25 ± 0.47. The eFEDS constraints are in good agreement with the results from the Planck mission, the galaxygalaxy lensing and clustering analysis of the Dark Energy Survey, and the cluster abundance analysis of the SPTSZ survey at a level of ≲ 1σ. With the empirical modelling, this work presents the first fully selfconsistent cosmological constraints based on a synergy between widefield Xray and weak lensing surveys.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 June 2023
 DOI:
 10.1093/mnras/stad957
 arXiv:
 arXiv:2207.12429
 Bibcode:
 2023MNRAS.522.1601C
 Keywords:

 gravitational lensing: weak;
 galaxies: clusters: general;
 cosmological parameters;
 dark energy;
 largescale structure of Universe;
 Xrays: galaxies: clusters;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 Accepted for publication in MNRAS. Figures 18 and 19 contain the main results. Chains and cluster masses are at https://github.com/inonchiu/eFEDSproducts