CAIRNS: The Cluster and Infall Region Nearby Survey. II. Environmental Dependence of Infrared Mass-to-Light Ratios

Abstract

CAIRNS (Cluster and Infall Region Nearby Survey) is a spectroscopic survey of the infall regions surrounding nine nearby rich clusters of galaxies. In our previous paper, we used redshifts within ~10 h -1 Mpc of the centers of the clusters to determine the mass profiles of the clusters based on the phase-space distribution of the galaxies. Here, we use Two Micron All Sky Survey photometry and an additional 515 redshifts to investigate the environmental dependence of near-infrared mass-to-light ratios. In the virial regions, the halo occupation function is nonlinear; the number of bright galaxies per halo increases more slowly than the mass of the halo. On larger scales, the light contained in galaxies is less clustered than the mass in rich clusters. Specifically, the mass-to-light ratio inside the virial radius