The Rarity of Star Formation in Brightest Cluster Galaxies as Measured by WISE

TL;DR

This study measures mid-infrared star formation rates in 245 nearby brightest cluster galaxies, revealing that most are passively evolving with very low star formation, and only two are highly active.

Contribution

First measurement of 12 micron star formation indicator for all nearby BCGs using WISE data, showing rarity of significant star formation in these galaxies.

Findings

99% of BCGs have star formation rates below 10 solar masses per year

Only Perseus A and Cygnus A have star formation rates above 40 solar masses per year

Star formation contributes minimally to BCG growth at present

Abstract

We present the mid-infrared (IR) star formation rates of 245 X-ray selected, nearby (z<0.1) brightest cluster galaxies (BCGs). A homogeneous and volume limited sample of BCGs was created by X-ray selecting clusters with L_x > 1x10^44 erg/s. The Wide-Field Infrared Survey Explorer (WISE) AllWISE Data Release provides the first measurement of the 12 micron star formation indicator for all BCGs in the nearby Universe. Perseus A and Cygnus A are the only galaxies in our sample to have star formation rates of > 40 M_sol/yr, indicating that these two galaxies are highly unusual at current times. Stellar populations of 99 +/- 0.6 % of local BCGs are (approximately) passively evolving, with star formation rates of <10 M_sol/yr. We find that in general, star formation produces only modest BCG growth at the current epoch.