Deep Herschel view of obscured star formation in the Bullet cluster

July 2010 • 2010A&A...518L..14R

Authors • Rawle, T. D. • Chung, S. M. • Fadda, D. • Rex, M. • Egami, E. • Pérez-González, P. G. • Altieri, B. • Blain, A. W. • Bridge, C. R. • Fiedler, A. K. • Gonzalez, A. H. • Pereira, M. J. • Richard, J. • Smail, I. • Valtchanov, I. • Zemcov, M. • Appleton, P. N. • Bock, J. J. • Boone, F. • Clement, B. • Combes, F. • Dowell, C. D. • Dessauges-Zavadsky, M. • Ilbert, O. • Ivison, R. J. • Jauzac, M. • Kneib, J. -P. • Lutz, D. • Pelló, R. • Rieke, G. H. • Rodighiero, G. • Schaerer, D. • Smith, G. P. • Walth, G. L. • van der Werf, P. • Werner, M. W.

Abstract • 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.

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Phil Appleton

Senior Scientist

Greg Walth

Assistant Scientist