HerMES: The Far-infrared Emission from Dust-obscured Galaxies

Calanog, J. A. and Wardlow, J. and Fu, Hai and Cooray, A. and Assef, R. J. and Bock, J. and Casey, C. M. and Conley, A. and Farrah, D. and Ibar, E. and Kartaltepe, J. and Magdis, G. and Marchetti, L. and Oliver, S. J. and Pérez-Fournon, I. and Riechers, D. and Rigopoulou, D. and Roseboom, I. G. and Schulz, B. and Scott, Douglas and Symeonidis, M. and Vaccari, M. and Viero, M. and Zemcov, M. (2013) HerMES: The Far-infrared Emission from Dust-obscured Galaxies. The Astrophysical Journal, 775 (1). p. 61. ISSN 0004-637X

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Abstract

Dust-obscured galaxies (DOGs) are an ultraviolet-faint, infrared-bright galaxy population that reside at z ~ 2 and are believed to be in a phase of dusty star-forming and active galactic nucleus (AGN) activity. We present far-infrared (far-IR) observations of a complete sample of DOGs in the 2 deg2 of the Cosmic Evolution Survey. The 3077 DOGs have langzrang = 1.9 ± 0.3 and are selected from 24 μm and r + observations using a color cut of r + - [24] >= 7.5 (AB mag) and S 24 >= 100 μJy. Based on the near-IR spectral energy distributions, 47% are bump DOGs (star formation dominated) and 10% are power-law DOGs (AGN-dominated). We use SPIRE far-IR photometry from the Herschel Multi-tiered Extragalactic Survey to calculate the IR luminosity and characteristic dust temperature for the 1572 (51%) DOGs that are detected at 250 μm (>=3σ). For the remaining 1505 (49%) that are undetected, we perform a median stacking analysis to probe fainter luminosities. Herschel-detected and undetected DOGs have average luminosities of (2.8 ± 0.4) × 1012 L ⊙ and (0.77 ± 0.08) × 1012 L ⊙, and dust temperatures of (33 ± 7) K and (37 ± 5) K, respectively. The IR luminosity function for DOGs with S 24 >= 100 μJy is calculated, using far-IR observations and stacking. DOGs contribute 10%-30% to the total star formation rate (SFR) density of the universe at z = 1.5-2.5, dominated by 250 μm detected and bump DOGs. For comparison, DOGs contribute 30% to the SFR density for all z = 1.5-2.5 galaxies with S 24 >= 100 μJy. DOGs have a large scatter about the star formation main sequence and their specific SFRs show that the observed phase of star formation could be responsible for their total observed stellar mass at z ~ 2.