Blind Detections of CO J = 1-0 in 11 H-ATLAS Galaxies at z = 2.1-3.5 with the GBT/Zpectrometer
Ivison, R. J.; Frayer, D. T.; Clements, D. L.; González-Nuevo, J.; Smail, Ian; Fritz, J.; Cooray, A.; Ibar, E.; Negrello, M.; De Zotti, G.; Bussmann, R. S.; Riechers, D. A.; Auld, R.; Baes, M.; Baker, A. J.; Cava, A.; Dannerbauer, H.; Dariush, A.; Dunne, L.; Dye, S.; Eales, S.; Harris, A. I.; Hopwood, R.; Jarvis, M. J.; Maddox, S.; Swinbank, A. M.; van der Werf, P. P.; Buttiglione, S.; Smith, D. J. B.; Temi, P.; Wardlow, J.; Rigby, E.
United States, United Kingdom, Netherlands, Belgium, Italy, Spain, Austria, France, New Zealand, South Africa
Abstract
We report measurements of the carbon monoxide ground state rotational transition (12C16O 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 μm. 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 μm selected galaxies is strikingly similar to the optical redshifts of 850 μm-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 μ from spectroscopic data alone, yielding μ ~ 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 1013 L ⊙.