Blind detections of CO J=1-0 IN 11 H-ATLAS Galaxies at z=2.1-3.5 with the GBT/Zpectrometer

A.I. Harris, A. J. Baker, D. T. Frayer, Ian Smail, A.M. Swinbank, D. A. Riechers, P. P. van der Werf, R. Auld, M. Baes, R. S. Bussmann, S. Buttiglione, A. Cava, D. L. Clements, A. Cooray, H. Dannerbauer, A. Dariush, G. De Zotti, L. Dunne, S. Dye, S. EalesJ. Fritz, J. Gonzalez-Nuevo, R. Hopwood, E. Ibar, R. J. Ivison, M.J. Jarvis, S. Maddox, M. Negrello, E. Rigby, Daniel Smith, P. Temi, J. Wardlow

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We report measurements of the carbon monoxide ground state rotational transition ((CO)-C-12-O-16 J = 1-0) with the Zpectrometer ultrawideband spectrometer on the 100 m diameter Green Bank Telescope. The sample comprises 11 galaxies with redshifts between z = 2.1 and 3.5 from a total sample of 24 targets identified by Herschel-ATLAS photometric colors from the SPIRE instrument. Nine of the CO measurements are new redshift determinations, substantially adding to the number of detections of galaxies with rest-frame peak submillimeter emission near 100 mu m. The CO detections confirm the existence of massive gas reservoirs within these luminous dusty star-forming galaxies (DSFGs). The CO redshift distribution of the 350 mu m selected galaxies is strikingly similar to the optical redshifts of 850 mu m-selected submillimeter galaxies in 2.1 <= z <= 3.5. Spectroscopic redshifts break a temperature-redshift degeneracy; optically thin dust models fit to the far-infrared photometry indicate characteristic dust temperatures near 34 K for most of the galaxies we detect in CO. Detections of two warmer galaxies, and statistically significant nondetections, hint at warmer or molecule-poor DSFGs with redshifts that are difficult to determine from Herschel-SPIRE photometric colors alone. Many of the galaxies identified by H-ATLAS photometry are expected to be amplified by foreground gravitational lenses. Analysis of CO linewidths and luminosities provides a method for finding approximate gravitational lens magnifications mu from spectroscopic data alone, yielding mu similar to 3-20. Corrected for magnification, most galaxy luminosities are consistent with an ultraluminous infrared galaxy classification, but three are candidate hyper-LIRGs with luminosities greater than 10(13) L-circle dot

Original languageEnglish
Article number152
Number of pages14
JournalThe Astrophysical Journal
Issue number2
Publication statusPublished - 20 Jun 2012


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