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Interferometric CO observations of submillimeter-faint, radio-selected starburst galaxies at z ~ 2

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 Kovács, 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. doi:10.1086/592137.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Neri, R.0000-0002-7176-4046
Bertoldi, F.0000-0002-1707-1775
Smail, Ian0000-0003-3037-257X
Blain, A. W.0000-0001-7489-5167
Cox, P.0000-0003-2027-8221
Genzel, R.0000-0002-2767-9653
Ivison, R. J.0000-0001-5118-1313
Omont, A.0000-0002-4721-3922
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
Funding AgencyGrant Number
Institut national des sciences de l'Univers (INSU)UNSPECIFIED
Max Planck GesellschaftUNSPECIFIED
Instituto Geografico Nacional (IGN)UNSPECIFIED
Canadian Space Agency (CSA)UNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Subject Keywords:cosmology: observations, galaxies: evolution, galaxies: formation, galaxies: high-redshift, galaxies: starburst
Issue or Number:2
Record Number:CaltechAUTHORS:20090721-114831864
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14627
Deposited By: Ruth Sustaita
Deposited On:12 Aug 2009 21:38
Last Modified:08 Nov 2021 23:13

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