Optical and X-ray profiles in the REXCESS sample of galaxy clusters*

Abstract

Galaxy clusters' structure, dominated by dark matter, is traced by member galaxies in the optical and hot intra-cluster medium (ICM) in X-rays. We compare the radial distribution of these components and determine the mass-to-light ratio vs. system mass relation.We use 14 clusters from the REXCESS sample which is representative of clusters detected in X-ray surveys. Photometric observations with the Wide Field Imager on the 2.2m MPG/ESO telescope are used to determine the number density profiles of the galaxy distribution out to r 200 . These are compared to electron density profiles of the ICM obtained using XMM-Newton, and dark matter profiles inferred from scaling relations and an NFW model.While red sequence galaxies trace the total matter profile, the blue galaxy distribution is much shallower. We see a deficit of faint galaxies in the central regions of massive and regular clusters, and strong suppression of bright and faint blue galaxies in the centres of cool-core clusters, attributable to ram pressure stripping of gas from blue galaxies in high density regions of ICM and disruption of faint galaxies due to galaxy interactions. We find a mass-to-light ratio vs. mass relation within r 200 of (3.0 ± 0.4) × 10 2 h M L −1 at 10 15 M with slope 0.16 ± 0.14, consistent with most previous results.

The XMM Cluster Survey: new evidence for the 3.5-keV feature in clusters is inconsistent with a dark matter origin

“…This well-studied cluster is not reported as having AGN activity or any distinct morphological or galaxy properties (e.g. Böhringer et al 2007Böhringer et al , 2010Ettori et al 2015;Holland et al 2015;Lovisari & Reiprich 2018). The best-fitting temperature and metallicity (following method A, see Section 2) are T PN X = 4.78 +0.12 −0.12 keV and Z = 0.4 +0.04 −0.04 Z , respectively.…”

The Resolved Sunyaev--Zel'dovich Profiles of Nearby Galaxy Groups

“…where G is the gravitational constant, M (< r) is the enclosed mass assumed to be dominated by the dark matter. The dark matter density profile was estimated using an NFW profile with a concentration parameter c 500 = 3.2 (e.g., Holland et al 2015). The two models of the gas densities (fiducial vs. polynomial) returned similar binding energies of the gas ∼ 10 62 ergs at 3 R 500 .…”

Optical inverse-Compton emission from clusters of galaxies

“…where L * is the bolometric stellar luminosity and τT is the optical depth for the Thomson scattering. The typical massto-light ratio within the virial radius rvir is given by M/L ≈ 2.5 × 10 2 M ⊙ /L ⊙ (e.g., Sheldon et al 2009;Holland et al 2015), so that L * ≈ 1.6×10 45 M14 erg s −1 . The optical depth τT can be estimated as,…”