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The Hubble deep field-north SCUBA super-map – IV. Characterizing submillimetre galaxies using deep Spitzer imaging

Pope, Alexandra and Scott, Douglas and Dickinson, Mark and Chary, Ranga-Ram and Morrison, Glenn and Borys, Colin and Sajina, Anna and Alexander, David M. and Daddi, Emanuele and Frayer, David T. and MacDonald, Emily and Stern, Daniel (2006) The Hubble deep field-north SCUBA super-map – IV. Characterizing submillimetre galaxies using deep Spitzer imaging. Monthly Notices of the Royal Astronomical Society, 370 (3). pp. 1185-1207. ISSN 0035-8711.

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We present spectral energy distributions (SEDs), Spitzer colours, and infrared (IR) luminosities for 850-μm selected galaxies in the Great Observatories Origins Deep Survey Northern (GOODS-N) field. Using the deep Spitzer Legacy images and new data and reductions of the Very Large Array-Hubble Deep Field (VLA-HDF) radio data, we find statistically secure counterparts for 60 per cent (21/35) of our submillimetre (submm) sample, and identify tentative counterparts for another 12 objects. This is the largest sample of submm galaxies with statistically secure counterparts detected in the radio and with Spitzer. Half of the secure counterparts have spectroscopic redshifts, while the other half have photometric redshifts. We find that in most cases the 850-μm emission is dominated by a single 24-μm source, with a median flux density of 241 μJy, leading to a median 24-to-850-μm flux density ratio of 0.040. A composite rest-frame SED shows that the submm sources peak at longer wavelengths than those of local ultraluminous infrared galaxies (ULIRGs). Using a basic grey-body model, 850-μm selected galaxies appear to be cooler than local ULIRGs of the same luminosity. This demonstrates the strong selection effects, both locally and at high redshift, which may lead to an incomplete census of the ULIRG population. The SEDs of submm galaxies are also different from those of their high-redshift neighbours, the near-IR selected BzK galaxies, whose mid-IR-to-radio SEDs are more like those of local ULIRGs. Using 24-μm, 850-μm and 1.4-GHz observations, we fit templates that span the mid-IR through radio to derive the integrated IR luminosity (LIR) of the submm galaxies and find a median value of LIR(8–1000 μm) = 6.0 × 1012 L. By themselves, 24-μm and radio fluxes are able to predict LIR reasonably well because they are relatively insensitive to temperature. However, the submm flux by itself consistently overpredicts LIR when using spectral templates which obey the local ULIRG temperature–luminosity relation. The shorter Spitzer wavelengths sample the stellar bump at the redshifts of the submm sources, and we find that the Spitzer photometry alone provides a model-independent estimate of the redshift, σ[Δz/(1 + z)] = 0.07. The median redshift for our secure submm counterparts is 2.0. Using X-ray and mid-IR data, only 5 per cent of our secure counterparts (1/21) show strong evidence for an active galactic nucleus dominating the LIR.

Item Type:Article
Related URLs:
URLURL TypeDescription
Pope, Alexandra0000-0001-8592-2706
Scott, Douglas0000-0002-6878-9840
Dickinson, Mark0000-0001-5414-5131
Chary, Ranga-Ram0000-0001-7583-0621
Sajina, Anna0000-0002-1917-1200
Alexander, David M.0000-0002-5896-6313
Daddi, Emanuele0000-0002-3331-9590
Frayer, David T.0000-0003-1924-1122
Stern, Daniel0000-0003-2686-9241
Additional Information:© 2006 The Authors. Accepted 2006 May 16. Received 2006 May 12; in original form 2005 November 3. We are grateful to the referee, Rob Ivison, for his helpful comments and suggestions which greatly improved this manuscript. We would like to thank Jasper Wall for advice on statistics and Kristen Coppin for help with the submm flux deboosting. We thank Bahram Mobasher and Thomas Dahlen for providing the photometric redshifts for the submm galaxies and Harry Ferguson for work on the GOODS IRAC simulations. We would also like to thank our colleagues Scott Chapman and Mark Halpern who helped orchestrate the SCUBA campaign in the GOODS-N region. This work was supported by the Natural Sciences and Engineering Research Council of Canada and the Canadian Space Agency. DMA acknowledges support from the Royal Society. ED gratefully acknowledges support through the Spitzer Fellowship Programme, under award 1268429. The James Clerk Maxwell Telescope is operated by The Joint Astronomy Centre on behalf of the Particle Physics and Astronomy Research Council of the United Kingdom, the Netherlands Organisation for Scientific Research, and the National Research Council of Canada. Much of the data used for our analysis were obtained via the Canadian Astronomy Data Centre, which is operated by the Herzberg Institute of Astrophysics, National Research Council of Canada and also supported by the Canadian Space Agency. Support for GOODS, part of the Spitzer Space Telescope Legacy Science Programme, was provided by NASA through Contract Number 1224666 issued by JPL, Caltech, under NASA contract 1407. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). [E.D. was a] Spitzer Fellow. This paper has been typeset from a TEX/LATEX file prepared by the author.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASA Spitzer Fellowship1268429
Particle Physics and Astronomy Research Council (PPARC)UNSPECIFIED
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
National Research Council of CanadaUNSPECIFIED
Canadian Space Agency (CSA)UNSPECIFIED
Subject Keywords:galaxies : evolution; galaxies : formation; galaxies : starburst; infrared : galaxies; submillimetre
Issue or Number:3
Record Number:CaltechAUTHORS:POPmnras06
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9634
Deposited By: Tony Diaz
Deposited On:20 Feb 2008
Last Modified:03 Oct 2019 00:02

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