The Relation Between Cool Cluster Cores and Herschel-Detected Star Formation in Brightest Cluster Galaxies

TL;DR

This study investigates the link between cool cluster cores and star formation in Brightest Cluster Galaxies using far-infrared data, revealing that star formation is influenced by cluster cooling processes and is not primarily from stellar mass loss.

Contribution

It provides the first comprehensive FIR analysis of BCGs across a range of redshifts, establishing a strong correlation between star formation and cluster cooling times, and distinguishing the origin of cold gas.

Findings

Star formation rates range from 1 to 150 solar masses per year.

Infrared luminosity correlates with cluster X-ray gas cooling times in cool-core clusters.

Most cold gas in FIR-bright BCGs is unlikely from stellar mass loss.

Abstract

We present far-infrared (FIR) analysis of 68 Brightest Cluster Galaxies (BCGs) at 0.08 < z < 1.0. Deriving total infrared luminosities directly from Spitzer and Herschel photometry spanning the peak of the dust component (24-500um), we calculate the obscured star formation rate (SFR). 22(+6.2,-5.3)% of the BCGs are detected in the far-infrared, with SFR= 1-150 M_sun/yr. The infrared luminosity is highly correlated with cluster X-ray gas cooling times for cool-core clusters (gas cooling time <1 Gyr), strongly suggesting that the star formation in these BCGs is influenced by the cluster-scale cooling process. The occurrence of the molecular gas tracing Ha emission is also correlated with obscured star formation. For all but the most luminous BCGs (L_TIR > 2x10^11 L_sun), only a small (<0.4 mag) reddening correction is required for SFR(Ha) to agree with SFR_FIR. The relatively low Ha extinction (dust obscuration), compared to values reported for the general star-forming population, lends further weight to an alternate (external) origin for the cold gas. Finally, we use a stacking analysis of non-cool-core clusters to show that the majority of the fuel for star formation in the FIR-bright BCGs is unlikely to originate form normal stellar mass loss.