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

Galaxy clusters' structure, dominated by dark matter, is traced by member galaxies in the optical and hot intracluster medium (ICM) in X-rays. We compare the radial distribution of these components and determine the mass-to-light ratio versus 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 2.2 m Max-Planck-Gesellschaft/European Southern Observatory telescope are used to determine the number density profiles of the galaxy distribution out to r₂₀₀. These are compared to electron density profiles of the ICM obtained using XMM-Newton, and dark matter profiles inferred from scaling relations and a Navarro-Frenk-White 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 versus mass relation within r₂₀₀ of (3.0 ± 0.4) × 10^2 h M_{⊙} L_{⊙}^{-1} at 10¹⁵ M_⊙ with slope 0.16 ± 0.14, consistent with most previous results.