The evolution in the stellar mass of Brightest Cluster Galaxies over the past 10 billion years

TL;DR

This study measures the growth of the most massive galaxies in galaxy clusters over the past 10 billion years, finding broad agreement with models and hints of slowed growth in recent epochs.

Contribution

It provides a new observational dataset of BCG stellar mass evolution over 10 billion years and compares it with theoretical models, highlighting potential recent slowdown in growth.

Findings

BCGs' stellar mass growth broadly matches models.

Growth rate may be slowing in last 3.5 billion years.

Sample includes 132 clusters with mass estimates.

Abstract

Using a sample of 98 galaxy clusters recently imaged in the near infra-red with the ESO NTT, WIYN and WHT telescopes, supplemented with 33 clusters from the ESO archive, we measure how the stellar mass of the most massive galaxies in the universe, namely Brightest Cluster Galaxies (BCG), increases with time. Most of the BCGs in this new sample lie in the redshift range $0.2<z<0.6$, which has been noted in recent works to mark an epoch over which the growth in the stellar mass of BCGs stalls. From this sample of 132 clusters, we create a subsample of 102 systems that includes only those clusters that have estimates of the cluster mass. We combine the BCGs in this subsample with BCGs from the literature, and find that the growth in stellar mass of BCGs from 10 billion years ago to the present epoch is broadly consistent with recent semi-analytic and semi-empirical models. As in other recent studies, tentative evidence indicates that the stellar mass growth rate of BCGs may be slowing in the past 3.5 billion years. Further work in collecting larger samples, and in better comparing observations with theory using mock images is required if a more detailed comparison between the models and the data is to be made.