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

TL;DR

This study compares optical and X-ray profiles of galaxy clusters from the REXCESS sample, revealing differences in galaxy distributions and their relation to dark matter, and establishing a mass-to-light ratio relation.

Contribution

It provides a comparative analysis of optical and X-ray profiles in galaxy clusters, highlighting the effects of ram pressure stripping and galaxy interactions on galaxy distributions.

Findings

Red sequence galaxies trace total matter profile.

Blue galaxy distribution is shallower than dark matter.

Mass-to-light ratio at 10^15 M_sun is (300±40) h M_sun/L_sun.

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 $\left(3.0\pm0.4\right) \times 10^2\, h\,\mathrm{M}_{\odot}\,\mathrm{L}_{\odot}^{-1}$ at $10^{15}\,\mathrm{M}_{\odot}$ with slope $0.16 \pm 0.14$, consistent with most previous results.