1302.3297 (M. T. Huynh et al.)

Physical Conditions of the Gas in an ALMA [CII]-identified Submillimetre Galaxy at z = 4.44    [PDF]

M. T. Huynh, R. P. Norris, K. E. K. Coppin, B. H. C. Emonts, R. J. Ivison, N. Seymour, Ian Smail, V. Smolcic, A. M. Swinbank, W. N. Brandt, S. C. Chapman, H. Dannerbauer, C. De Breuck, T. R. Greve, J. A. Hodge, A. Karim, K. K. Knudsen, K. M. Menten, P. P. van der Werf, F. Walter, A. Weiss

We present CO(2-1) observations of the submillimetre galaxy ALESS65.1 performed with the Australia Telescope Compact Array at 42.3 GHz. A previous ALMA study of submillimetre galaxies in the Extended Chandra Deep Field South detected [CII] 157.74 micron emission from this galaxy at a redshift of z = 4.44. No CO(2-1) emission was detected but we derive a firm upper limit to the cold gas mass in ALESS65.1 of M_gas < 1.7 x 10^10 M_odot. The estimated gas depletion timescale is <50 Myr, which is similar to other high redshift SMGs, and consistent with z > 4 SMGs being the likely progenitors of massive red-and-dead galaxies at z > 2. The ratio of the [CII], CO and far-infrared luminosities implies a strong far-ultraviolet field of G_0 > 10^3, as seen in Galactic star forming regions or local ULIRGs. The observed L_[CII]/L_FIR = 2.3 x 10^{-3} is high compared to local ULIRGs and, combined with L_[CII]/L_CO > 2700, it is consistent with ALESS65.1 either having an extended (several kpc) [CII] emitting region or lower than solar metallicity.

View original: http://arxiv.org/abs/1302.3297