The Hierarchical Build‐Up of Massive Galaxies and the Intracluster Light sincez= 1

Abstract

We use a set of simulation-based models for the dissipationless evolution of galaxies since z = 1 to constrain the fate of accreted satellites embedded in dark matter subhalos. These models assign stellar mass to dark matter halos at z = 1 by relating the observed galaxy stellar mass function (GSMF) to the halo + subhalo mass function monotonically. The evolution of the stellar mass content is then followed using halo merger trees extracted from N-body simulations. Our models are differentiated only in the fate assigned to satellite galaxies once subhalos, within which satellites are embedded, disrupt. These models are confronted with the observed evolution in the massive end of the GSMF, the z ~ 0 brightest cluster galaxy (BCG) to cluster mass relation, and the combined BCG and intracluster light (ICL) luminosity distribution—all observables expected to evolve approximately dissipationlessly since z = 1. The combined observational constraints favor a model in which the vast majority (≳80%) of satellite stars from disrupted subhalos go into the ICL (operationally defined here as light below a surface brightness cut of μi ≈ 23 mag arcsec-2). Conversely, models that leave behind a significant population of satellite galaxies once the subhalo has disrupted are strongly disfavored, as are models that put a significant fraction of satellite stars into the BCG. Our results show that observations of the ICL provide useful and unique constraints on models of galaxy merging and the dissipationless evolution of galaxies in groups and clusters.