Signatures of Star Formation in Brightest Cluster Galaxies

TL;DR

This paper reviews evidence of star formation and other activity signatures in brightest cluster galaxies, highlighting differences based on cluster selection and presenting early survey results with recent updates.

Contribution

It provides a synthesis of recent observations of activity in BCGs, including star formation indicators and the impact of cluster environment.

Findings

Mid-IR spectra suggest star formation in some BCGs.

Emission-line BCG incidence varies with cluster type.

Recent UV and H-alpha surveys show low activity in REXCESS BCGs, with recent discoveries increasing detected activity.

Abstract

I discuss and review recent studies of the signatures of activity in brightest cluster galaxies. Mid-IR spectra appear to show indications of star formation in a sample of 9 BCGs from de Messieres et al. (2009). Other processes like cosmic ray heating and conduction may play a role. The incidence of emission-line BCGs in X-ray selected clusters is higher than in optically-selected clusters, and higher still in systems known to be cool cores. We report early results of a UV and H-alpha survey of the BCGs in the REXCESS sample, which reveals that this sample has an interestingly low number of emission-line or UV excess systems. [Note added post facto: fainter emission-line sources discovered this summer increasses the rate to 22%.]