Red Galaxy Growth and the Halo Occupation Distribution

TL;DR

This study investigates the growth of red galaxies over the past 7 billion years within dark matter halos, analyzing their distribution, stellar mass evolution, and the relationship between galaxy and halo mass.

Contribution

It provides new insights into the halo occupation distribution and the stellar mass growth of red galaxies, highlighting that halo mergers do not always result in rapid central galaxy growth.

Findings

Half of halos with mass 10^{11.9} Msun/h host a red central galaxy.

Red galaxy stellar mass has doubled since z=1.

Most stellar mass in clusters resides in satellites and intra-cluster light.

Abstract

We have traced the past 7 Gyr of red galaxy stellar mass growth within dark matter halos. We have determined the halo occupation distribution, which describes how galaxies reside within dark matter halos, using the observed luminosity function and clustering of 40,696 0.2<z<1.0 red galaxies in Bootes. Half of 10^{11.9} Msun/h halos host a red central galaxy, and this fraction increases with increasing halo mass. We do not observe any evolution of the relationship between red galaxy stellar mass and host halo mass, although we expect both galaxy stellar masses and halo masses to evolve over cosmic time. We find that the stellar mass contained within the red population has doubled since z=1, with the stellar mass within red satellite galaxies tripling over this redshift range. In cluster mass halos most of the stellar mass resides within satellite galaxies and the intra-cluster light, with a minority of the stellar mass residing within central galaxies. The stellar masses of the most luminous red central galaxies are proportional to halo mass to the power of a third. We thus conclude that halo mergers do not always lead to rapid growth of central galaxies. While very massive halos often double in mass over the past 7 Gyr, the stellar masses of their central galaxies typically grow by only 30%.