Infrared Luminosities and Dust Properties of z ≈ 2 Dust-obscured Galaxies

Creators: Bussmann, R. S.; Dey, Arjun; Borys, C.; Desai, V.; Jannuzi, B. T.; Le Floc'h, E.; Melbourne, J.; Sheth, K.; Soifer, B. T.

Abstract

We present SHARC-II 350 μm imaging of twelve 24 μm bright (F_(24 μm) > 0.8 mJy) Dust-Obscured Galaxies (DOGs) and Combined Array for Research in Millimeter-wave Astronomy (CARMA) 1 mm imaging of a subset of two DOGs. These objects are selected from the Boötes field of the NOAO Deep Wide-Field Survey. Detections of four DOGs at 350 μm imply infrared (IR) luminosities which are consistent to within a factor of 2 of expectations based on a warm-dust spectral energy distribution (SED) scaled to the observed 24 μm flux density. The 350 μm upper limits for the 8 non-detected DOGs are consistent with both Mrk 231 and M82 (warm-dust SEDs), but exclude cold dust (Arp 220) SEDs. The two DOGs targeted at 1 mm were not detected in our CARMA observations, placing strong constraints on the dust temperature: T_(dust) > 35-60 K. Assuming these dust properties apply to the entire sample, we find dust masses of ≈ 3 × 10^8 M_⊙. In comparison to other dusty z ~ 2 galaxy populations such as submillimeter galaxies (SMGs) and other Spitzer-selected high-redshift sources, this sample of DOGs has higher IR luminosities (2 × 10^(13) L_⊙ versus 6 × 10^(12) L_⊙ for the other galaxy populations) that are driven by warmer dust temperatures (>35-60 K versus ~30 K) and lower inferred dust masses (3 × 10^8 M_⊙ versus 3 × 10^9 M_⊙). Wide-field Herschel and Submillimeter Common-User Bolometer Array-2 surveys should be able to detect hundreds of these power-law-dominated DOGs. We use the existing Hubble Space Telescope and Spitzer/InfraRed Array Camera data to estimate stellar masses of these sources and find that the stellar to gas mass ratio may be higher in our 24 μm bright sample of DOGs than in SMGs and other Spitzer-selected sources. Although much larger sample sizes are needed to provide a definitive conclusion, the data are consistent with an evolutionary trend in which the formation of massive galaxies at z ~ 2 involves a submillimeter bright, cold-dust, and star-formation-dominated phase followed by a 24 μm bright, warm-dust and AGN-dominated phase.

Additional Information

© 2009 The American Astronomical Society. Received 2009 May 27; accepted 2009 September 16; published 2009 October 8. 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 NASA contract 1407. Spitzer/MIPS guaranteed time observing was used to image the Bootes field at 24 μm and is critical for the selection of DOGs. We thank the SDWFS team (particularly Daniel Stern and Matt Ashby) for making the IRAC source catalogs publicly available. Data from the original IRAC shallow survey were used for initial stellar mass estimates. We thank the anonymous referee for a thorough review of the manuscript that helped improve the paper. We are grateful to the expert assistance of the staff of Kitt Peak National Observatory where the Bootes field observations of the NDWFS were obtained. The authors thank NOAO for supporting the NOAO Deep Wide-Field Survey. In particular, we thank Jenna Claver, Lindsey Davis, Alyson Ford, Emma Hogan, Tod Lauer, Lissa Miller, Erin Ryan, Glenn Tiede and Frank Valdes for their able assistance with the NDWFS data. We also thank the staff of the W. M. Keck Observatory, where some of the galaxy redshifts were obtained. R.S.B. gratefully acknowledges financial assistance from HST grant GO10890, without which this research would not have been possible. Support for Program number HSTGO10890 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. The research activities of A.D. are supported by NOAO, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. Support for E. Le Floc'h was provided by NASA through the Spitzer Space Telescope Fellowship Program. Facilities: Spitzer, CSO, and CARMA. This research made use of CSO (SHARC-II) and CARMA data. Support for CARMA construction was derived from the states of California, Illinois, and Maryland, the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the Associates of the California Institute of Technology, and the National Science Foundation. Ongoing CARMA development and operations are supported by the National Science Foundation under a cooperative agreement, and by the CARMA partner universities.

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