The Stellar Mass Growth of Brightest Cluster Galaxies in the IRAC Shallow Cluster Survey

TL;DR

This study investigates the stellar mass growth of brightest cluster galaxies (BCGs) over cosmic time using a novel cluster selection method applied to the IRAC Shallow Cluster Survey, finding significant growth consistent with models from redshift 1.5 to 0.5.

Contribution

It introduces a new approach to select cluster progenitors based on luminosity ranking and applies it to study BCG evolution in a large survey.

Findings

BCGs grow in stellar mass by a factor of 2.3 from z=1.5 to 0.5.

Observed growth matches semi-analytic model predictions.

Hints of divergence between models and observations below z=0.5.

Abstract

The details of the stellar mass assembly of brightest cluster galaxies (BCGs) remain an unresolved problem in galaxy formation. We have developed a novel approach that allows us to construct a sample of clusters that form an evolutionary sequence, and have applied it to the Spitzer IRAC Shallow Cluster Survey (ISCS) to examine the evolution of BCGs in progenitors of present-day clusters with mass of (2.5-4.5)x10^{14}Msun. We follow the cluster mass growth history extracted from a high resolution cosmological simulation, and then use an empirical method that infers the cluster mass based on the ranking of cluster luminosity to select high-z clusters of appropriate mass from ISCS to be progenitors of the given set of z=0 clusters. We find that, between z=1.5 and 0.5, the BCGs have grown in stellar mass by a factor of 2.3, which is well-matched by the predictions from a state-of-the-art semi-analytic model. Below z=0.5 we see hints of differences in behavior between the model and observation.