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Published July 2014 | Submitted + Published
Journal Article Open

Optical-faint, Far-infrared-bright Herschel Sources in the CANDELS Fields: Ultra-luminous Infrared Galaxies at z > 1 and the Effect of Source Blending

Abstract

The Herschel very wide field surveys have charted hundreds of square degrees in multiple far-IR (FIR) bands. While the Sloan Digital Sky Survey (SDSS) is currently the best resource for optical counterpart identifications over such wide areas, it does not detect a large number of Herschel FIR sources and leaves their nature undetermined. As a test case, we studied seven "SDSS-invisible," very bright 250 μm sources (S_(250) > 55 mJy) in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey fields where we have a rich multi-wavelength data set. We took a new approach to decompose the FIR sources, using the near-IR or the optical images directly for position priors. This is an improvement over the previous decomposition efforts where the priors are from mid-IR data that still suffer from the problem of source blending. We found that in most cases the single Herschel sources are made of multiple components that are not necessarily at the same redshifts. Our decomposition succeeded in identifying and extracting their major contributors. We show that these are all ultra-luminous infrared galaxies at z ~ 1-2 whose high L_(IR) is mainly due to dust-obscured star formation. Most of them would not be selected as submillimeter galaxies. They all have complicated morphologies indicative of mergers or violent instability, and their stellar populations are heterogeneous in terms of stellar masses, ages, and formation histories. Their current ultra-luminous infrared galaxy phases are of various degrees of importance in their stellar mass assembly. Our practice provides a promising starting point for developing an automatic routine to reliably study bright Herschel sources.

Additional Information

© 2014 The American Astronomical Society. Received 2013 December 1; accepted 2014 April 8; published 2014 June 11. We thank the anonymous referee for the critical reading and useful comments which helped improve the quality of the paper. We thank M. Bolzonella for providing the latest update of the Hyperz code, C. Peng for the useful discussion of the GALFIT code, R. Siebenmorgen for explaining a number of details of the SK07 models, R. Ivison for allowing the use of the non-public radio map in the EGS field, and E. Laird and K. Nandra for the AEGIS Chandra X-ray catalog that is not yet public. We also thank M. Dickinson, H. Ferguson, J. Newman, and M. Salvato for their useful comments. H.Y.,M.S., and Z.M. acknowledge the support of Spitzer RSA 1445905. This work is based on observations made by Herschel, an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Support for Program number HST-GO-12060 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. This work is also 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. Support for this work was provided by NASA through an award issued by JPL/Caltech. This work also makes use of the SDSS. Funding for the creation and distribution of the SDSS Archive has been provided by theAlfred P. Sloan Foundation, the Participating Institutions, the National Aeronautics and Space Administration, the National Science Foundation, the Department of Energy, the Japanese Monbukagakusho, and the Max Planck Society. The SDSS Web site is http://www.sdss.org. The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the University of Chicago, Fermilab, the Institute for Advanced Study, the Japan ParticipationGroup, The Johns Hopkins University, Los Alamos National Laboratory, the Max Planck Institute for Astronomy, the Max Planck Institute for Astrophysics, New Mexico State University, the University of Pittsburgh, Princeton University, the US Naval Observatory, and the University of Washington. This paper has used data obtained by the SHARDS project, funded by the Spanish MINECO grant AYA2012-31277, and based on observations made with the Gran Telescopio Canarias (GTC).

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Submitted - 1312.0902v2.pdf

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Created:
August 22, 2023
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October 17, 2023