Deep Herschel view of obscured star formation in the Bullet cluster

We use deep, five band (100-500 μm) data from the Herschel Lensing Survey (HLS) to fully constrain the obscured star formation rate, SFR_FIR, of galaxies in the Bullet cluster (z = 0.296), and a smaller background system (z = 0.35) in the same field. Herschel detects 23 Bullet cluster members with a total SFR_FIR = 144±14 M_⊙ yr^-1. On average, the background system contains brighter far-infrared (FIR) galaxies, with ~50% higher SFR_FIR (21 galaxies; 207± 9 M_⊙ yr^-1). SFRs extrapolated from 24 μm flux via recent templates (SFR_{24 µm}) agree well with SFR_FIR for ~60% of the cluster galaxies. In the remaining ~40%, SFR_{24 µm} underestimates SFR_FIR due to a significant excess in observed S₁₀₀/S₂₄ (rest frame S₇₅/S₁₈) compared to templates of the same FIR luminosity.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Data presented in this paper were analyzed using “The Herschel Interactive Processing Environment (HIPE)”, a joint development by the Herschel Science Ground Segment Consortium, consisting of ESA, the NASA Herschel Science Center, and the HIFI, PACS and SPIRE consortia.