Stellar Mass Assembly of Brightest Cluster Galaxies at Late Times

TL;DR

This study investigates the stellar mass growth of brightest cluster galaxies (BCGs) at late cosmic times using cluster samples at redshifts 0.4 and 0.2, finding minimal growth contrary to model predictions.

Contribution

It constructs statistically linked progenitor-descendant cluster samples at different redshifts to study BCG mass assembly history.

Findings

BCGs grow only a few percent in stellar mass between z~0.4 and z~0.2.

Observed growth is much lower than semi-analytic model predictions.

Supports the idea that BCGs assemble most of their mass earlier in cosmic history.

Abstract

Understanding the formation history of brightest cluster galaxies is an important topic in galaxy formation. Utilizing the Planck Sunyaev-Zel'dovich cluster catalog, and applying the Ansatz that the most massive halos at one redshift remain among the most massive ones at a slightly later cosmic epoch, we have constructed cluster samples at redshift z~0.4 and z~0.2 that can be statistically regarded as progenitor-descendant pairs. This allows us to study the stellar mass assembly history of BCGs in these massive clusters at late times, finding the degree of growth between the two epochs is likely at only few percent level, which is far lower compared to the prediction from a state-of-the-art semi-analytic galaxy formation model.