Chapman, S. C. and Neri, R. and Bertoldi, F. and Smail, Ian and Greve, T. R. and Trethewey, D. and Blain, A. W. and Cox, P. and Genzel, R. and Ivison, R. J. and Kovacs, A. and Omont, A. and Swinbank, A. M. (2008) Interferometric CO observations of submillimeter-faint, radio-selected starburst galaxies at z ~ 2. Astrophysical Journal, 689 (2). pp. 889-896. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20090721-114831864
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High-redshift, dust-obscured galaxies, selected to be luminous in the radio but relatively faint at 850 µm, appear to represent a different population from the ultraluminous submillimeter-bright population. They may be star-forming galaxies with hotter dust temperatures, or they may have lower far-infrared luminosities and larger contributions from obscured active galactic nuclei (AGNs). Here we present observations of three z ~ 2 examples of this population, which we term "submillimeter-faint radio galaxies" (SFRGs; RG J163655, RG J131236, and RG J123711) in CO(3-2) using the IRAM Plateau de Bure Interferometer to study their gas and dynamical properties.We estimate the molecular gas mass in each of the three SFRGs (8.3 x 10^9, <5.6 x 10^9, and 15.4 ; 10^9 M☉, respectively) and, in the case of RG J163655, a dynamical mass by measurement of the width of the CO(3-2) line (8 x 10^(10) csc^2i M☉). While these gas masses are substantial, on average they are 4 times lower than submillimeter-selected galaxies (SMGs). Radio-inferred star formation rates (‹SFR_radio› = 970 M☉ y^(-1)) suggest much higher star formation efficiencies than are found forSMGs and shorter gas depletion timescales (~11 Myr), much shorter than the time required to form their current stellar masses (~160 Myr; ~ 10^(11) M☉). By contrast, star formation rates (SFRs) may be overestimated by factors of a few, bringing the efficiencies in line with those typically measured for other ultraluminous star-forming galaxies and suggesting that SFRGs are more like ultraviolet-selected (UV-selected) star-forming galaxies with enhanced radio emission. A tentative detection of RG J163655 at 350 µm suggests hotter dust temperatures, and thus gas-to-dust mass fractions, similar to the SMGs.
|Additional Information:||© 2008. The American Astronomical Society. Received 2008 February 27; accepted 2008 July 22. We thank an anonymous referee for a very careful reading and helpful comments. This work is based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS ( France), MPG (Germany), and IGN (Spain). S. C. C. acknowledges a fellowship from the Canadian Space Agency and an NSERC discovery grant. I. S. acknowledges support from the Royal Society. A. M. S. acknowledges support from STFC. We acknowledge the use of GILDAS software (see http://www.iram.fr/IRAMFR/GILDAS).|
|Subject Keywords:||cosmology: observations, galaxies: evolution, galaxies: formation, galaxies: high-redshift, galaxies: starburst|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||12 Aug 2009 21:38|
|Last Modified:||26 Dec 2012 11:05|
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