Evidence for Significant Growth in the Stellar Mass of Brightest Cluster Galaxies over the Past 10 Billion Years

TL;DR

This study demonstrates that brightest cluster galaxies have grown significantly in stellar mass over the past 10 billion years, primarily through dry mergers, with observed growth aligning more closely with semi-analytic models than previous estimates.

Contribution

It provides new empirical evidence of BCG mass growth over cosmic time, correcting for cluster mass correlations and comparing results with theoretical models.

Findings

BCGs' stellar mass increased by a factor of 1.8 from z=0.9 to z=0.2

Observed BCG masses at z=0.9 are 1.5 times higher than model predictions

Most mass growth likely occurs via dry mergers with minimal star formation

Abstract

Using new and published data, we construct a sample of 160 brightest cluster galaxies (BCGs) spanning the redshift interval 0.03 < z < 1.63. We use this sample, which covers 70% of the history of the universe, to measure the growth in the stellar mass of BCGs after correcting for the correlation between the stellar mass of the BCG and the mass of the cluster in which it lives. We find that the stellar mass of BCGs increase by a factor of 1.8 between z=0.9 and z=0.2. Compared to earlier works, our result is closer to the predictions of semi-analytic models. However, BCGs at z=0.9, relative to BCGs at z=0.2, are still a factor of 1.5 more massive than the predictions of these models. Star formation rates in BCGs at z~1 are generally to low to result in significant amounts of mass. Instead, it is likely that most of the mass build up occurs through mainly dry mergers in which perhaps half of the mass is lost to the intra-cluster medium of the cluster.