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Published September 20, 2013 | Submitted + Published
Journal Article Open

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 deg^2 of the Cosmic Evolution Survey. The 3077 DOGs have 〈z〉 = 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) × 10^(12) L_☉ and (0.77 ± 0.08) × 10^(12) 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.

Additional Information

© 2013 American Astronomical Society. Received 2013 April 16, accepted for publication 2013 July 22. Published 2013 September 5. We thank the anonymous referee for useful comments that helped improve this paper. We thank Jason Melbourne for insightful discussions. SPIRE has been developed by a consortium of institutes led by Cardiff University (UK) and including: University of Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, University of Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCLMSSL, UKATC, Univ. Sussex (UK); and Caltech, JPL, NHSC, University of Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC, UKSA (UK); and NASA (USA). This research has made use of data from the HerMES project (http://hermes.sussex.ac.uk/). HerMES is a Herschel Key Programme utilizing Guaranteed Time from the SPIRE instrument team, ESAC scientists, and a mission scientist. The data presented in this paper will be released through the HerMES Database in Marseille, HeDaM (http://hedam.oamp.fr/HerMES/). We our thankful to the COSMOS collaboration for granting us access to their catalogs and we gratefully acknowledge the contributions of the entire COSMOS team that have made this work possible. More information on the COSMOS survey is available at http://hermes.sussex.ac.uk/. This work is based (in part) on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. We acknowledge support from a GAANN fellowship (to J.A.C.), NSF CAREER AST-0645427 (A.C. and H.F.), and NASA funds to the US HerMES team through JPL. S.O. acknowledges support from the Science and Technology Facilities Council [grant number ST/I000976/1]. Some of the data (spectroscopic redshifts) presented here were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community.We are most fortunate to have the opportunity to conduct observations from this mountain. Facilities: Herschel (SPIRE), Spitzer (IRAC, MIPS), Subaru (Suprime Cam), Keck:II (DEIMOS)

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