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Published March 1, 2009 | Published
Journal Article Open

Hubble Space Telescope Morphologies of z ~ 2 Dust Obscured Galaxies. I. Power-Law Sources


We present high-spatial resolution optical and near-infrared imaging obtained using the ACS, WFPC2, and NICMOS cameras aboard the Hubble Space Telescope of 31 24 μm bright z ≈ 2 Dust Obscured Galaxies (DOGs) identified in the Boötes Field of the NOAO Deep Wide-Field Survey. Although this subset of DOGs have mid-IR spectral energy distributions dominated by a power-law component suggestive of an AGN, all but one of the galaxies are spatially extended and not dominated by an unresolved component at rest-frame UV or optical wavelengths. The observed V – H and I-H colors of the extended components are 0.2-3 magnitudes redder than normal star-forming galaxies. All but one have axial ratios >0.3, making it unlikely that DOGs are composed of an edge-on star-forming disk. We model the spatially extended component of the surface brightness distributions of the DOGs with a Sérsic profile and find effective radii of 1-6 kpc. This sample of DOGs is smaller than most submillimeter galaxies (SMGs), but larger than quiescent high-redshift galaxies. Nonparametric measures (Gini and M_20) of DOG morphologies suggest that these galaxies are more dynamically relaxed than local ULIRGs. We estimate lower limits to the stellar masses of DOGs based on the rest-frame optical photometry and find that these range from ~10^9-10^(11) M☉ . If major mergers are the progenitors of DOGs, then these observations suggest that DOGs may represent a postmerger evolutionary stage.

Additional Information

© 2009 American Astronomical Society. Received 2008 August 29; accepted 2008 November 11; published 2009 March 3. 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. and B.T.J. 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.

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