The Relation between Cool Cluster Cores and Herschel-detected Star Formation in Brightest Cluster Galaxies

March 2012 • 2012ApJ...747...29R

Authors • Rawle, T. D. • Edge, A. C. • Egami, E. • Rex, M. • Smith, G. P. • Altieri, B. • Fiedler, A. • Haines, C. P. • Pereira, M. J. • Pérez-González, P. G. • Portouw, J. • Valtchanov, I. • Walth, G. • van der Werf, P. P. • Zemcov, M.

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 (24-500 μm), 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 _⊙ yr^-1. 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 Hα emission is also correlated with obscured star formation. For all but the most luminous BCGs (L _TIR > 2 × 10¹¹ L _⊙), only a small (lsim0.4 mag) reddening correction is required for SFR(Hα) to agree with SFR_FIR. The relatively low Hα 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 from normal stellar mass loss.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

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Greg Walth

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