Superdense massive galaxies in the ESO Distant Cluster Survey (EDisCS)

TL;DR

This study reveals that the median size of cluster galaxies remains largely unchanged from redshift 0.7 to 0.04, while the most massive galaxies have significantly grown, highlighting the importance of progenitor bias in galaxy evolution.

Contribution

It demonstrates that the apparent size evolution of cluster galaxies is largely due to sample selection effects rather than true physical growth.

Findings

Median size of non-BCG cluster galaxies is only slightly smaller at high redshift.

Massive BCGs and galaxies with M*>4x10^11 Msun have doubled or quadrupled in size.

Progenitor bias significantly influences observed size evolution of passive galaxies.

Abstract

We find a significant number of massive and compact galaxies in clusters from the ESO Distant Clusters Survey (EDisCS) at 0.4<z<1. They have similar stellar masses, ages, sizes and axial ratios to local z~0.04 compact galaxies in WINGS clusters, and to z=1.4-2 massive and passive galaxies found in the general field. If non-BCG cluster galaxies of all densities, morphologies and spectral types are considered, the median size of EDisCS galaxies is only a factor 1.18 smaller than in WINGS. We show that for morphologically selected samples, the morphological evolution taking place in a significant fraction of galaxies during the last Gyrs may introduce an apparent, spurious evolution of size with redshift, which is actually due to intrinsic differences in the selected samples. We conclude that the median mass-size relation of cluster galaxies does not evolve significantly from z~0.7 to z~0.04. In contrast, the masses and sizes of BCGs and galaxies with M*>4x10^11 Msun have significantly increased by a factor of 2 and 4, respectively, confirming the results of a number of recent works on the subject. Our findings show that progenitor bias effects play an important role in the size-growth paradigm of massive and passive galaxies.