HerMES: the far-infrared emission from dust-obscured galaxies

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 (z) = 1.9 ± 0.3 and are selected from 24µm and r+ observations using a color cut of r+ - [24] 7.5 (AB mag) and S24 100µJy. 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 250µm (3s). 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 S24 100µJy 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 250µm detected and bump DOGs. For comparison, DOGs contribute 30% to the SFR density for all z = 1.5–2.5 galaxies with S24 100µJy. 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.