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A Redshift Survey of Herschel Far-infrared Selected Starbursts and Implications for Obscured Star Formation

Casey, C. M. and Bock, J. and Bridge, C. and Cooray, A. and Vieira, J. D. and Viero, M. (2012) A Redshift Survey of Herschel Far-infrared Selected Starbursts and Implications for Obscured Star Formation. Astrophysical Journal, 761 (2). Art. No. 140. ISSN 0004-637X.

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We present Keck spectroscopic observations and redshifts for a sample of 767 Herschel-SPIRE selected galaxies (HSGs) at 250, 350, and 500 μm, taken with the Keck I Low Resolution Imaging Spectrometer and the Keck II DEep Imaging Multi-Object Spectrograph. The redshift distribution of these SPIRE sources from the Herschel Multitiered Extragalactic Survey peaks at z = 0.85, with 731 sources at z < 2 and a tail of sources out to z ~ 5. We measure more significant disagreement between photometric and spectroscopic redshifts (〈Δz/(1 + z_(spec))〉 = 0.29) than is seen in non-infrared selected samples, likely due to enhanced star formation rates and dust obscuration in infrared-selected galaxies. The infrared data are used to directly measure integrated infrared luminosities and dust temperatures independent of radio or 24 μm flux densities. By probing the dust spectral energy distribution (SED) at its peak, we estimate that the vast majority (72%-83%) of z < 2 Herschel-selected galaxies would drop out of traditional submillimeter surveys at 0.85-1 mm. We find that dust temperature traces infrared luminosity, due in part to the SPIRE wavelength selection biases, and partially from physical effects. As a result, we measure no significant trend in SPIRE color with redshift; if dust temperature were independent of luminosity or redshift, a trend in SPIRE color would be expected. Composite infrared SEDs are constructed as a function of infrared luminosity, showing the increase in dust temperature with luminosity, and subtle change in near-infrared and mid-infrared spectral properties. Moderate evolution in the far-infrared (FIR)/radio correlation is measured for this partially radio-selected sample, with q_(IR) ∝(1 + z)^(–0.30±0.02) at z < 2. We estimate the luminosity function and implied star formation rate density contribution of HSGs at z < 1.6 and find overall agreement with work based on 24 μm extrapolations of the LIRG, ULIRG, and total infrared contributions. This work significantly increased the number of spectroscopically confirmed infrared-luminous galaxies at z » 0 and demonstrates the growing importance of dusty starbursts for galaxy evolution studies and the build-up of stellar mass throughout cosmic time.

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Cooray, A.0000-0002-3892-0190
Additional Information:© 2012 American Astronomical Society. Received 2012 July 26; accepted 2012 October 15; published 2012 December 4. We thank the anonymous reviewer for a very useful, constructive report that improved the manuscript. C.M.C. is generously supported by a Hubble Fellowship from Space Telescope Science Institute, grant HST-HF-51268.01-A. The data presented herein 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. This work would not be possible without the hard work and dedication of the Keck Observatory night and day staff; special thanks to Marc Kassis, Luca Rizzi and Greg Wirth for help and advice while observing. The analysis pipeline used to reduce the DEIMOS data was developed at UC Berkeley with support from NSF grant AST-0071048. Thanks to Nick Scoville and Brian Siana for useful discussions which improved the paper. SPIRE has been developed by a consortium of institutes led by Cardiff Univ. (UK) and including: Univ. Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, Univ. Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, Univ. Sussex (UK); and Caltech, JPL, NHSC, Univ. 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 ( HerMES is a Herschel Key Programme utilizing Guaranteed Time from the SPIRE instrument team, ESAC scientists and a mission scientist. HerMES is described in Oliver et al. (2012). The SPIRE data presented in this paper will be released through the HerMES Database in Marseille, HeDaM (
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF-51268.01-A
W. M. Keck FoundationUNSPECIFIED
Canadian Space Agency (CSA)UNSPECIFIED
National Astronomical Observatories, Chinese Academy of Sciences (NAOC)UNSPECIFIED
Commissariat à l’Energie Atomique (CEA)UNSPECIFIED
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Ministerio de Ciencia e Innovación (MCINN)UNSPECIFIED
Swedish National Space Board (SNSB)UNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
United Kingdom Space Agency (UKSA)UNSPECIFIED
Subject Keywords:galaxies: evolution; galaxies: high-redshift; galaxies: starburst; infrared: galaxies; submillimeter: galaxies
Record Number:CaltechAUTHORS:20130111-152856336
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Official Citation:A Redshift Survey of Herschel Far-infrared Selected Starbursts and Implications for Obscured Star Formation C. M. Casey et al. 2012 ApJ 761 140
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36334
Deposited By: Ruth Sustaita
Deposited On:11 Jan 2013 23:49
Last Modified:07 Dec 2016 20:25

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