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Durham University

Department of Physics

Staff profile

Publication details for Professor Ian Smail

Huynh, M.T., Kimball, A.E., Norris, R.P., Smail, I., Chow, K.E., Coppin, K.E.K., Emonts, B.H.C., Ivison, R.J., Smolčić, V. & Swinbank, A.M. (2014). Detection of molecular gas in an ALMA [C II]-identified submillimetre galaxy at z = 4.44. Monthly Notices of the Royal Astronomical Society Letters 443(1): L54-L58.

Author(s) from Durham


We present the detection of 12CO(2–1) in the z = 4.44 submillimetre galaxy ALESS65.1 using the Australia Telescope Compact Array. A previous Atacama Large Millimeter/submillimeter Array study of submillimetre galaxies (SMGs) in the Extended Chandra Deep Field South determined the redshift of this optically and near-infrared undetected source through the measurement of [C II] 157.74 μm emission. Using the luminosity of the 12CO(2–1) emission, we estimate the gas mass to be Mgas ∼ 1.7 × 1010 M⊙. The gas depletion time-scale of ALESS65.1 is ∼ 25 Myr, similar to other high-redshift SMGs and consistent with z > 4 SMGs being the progenitors of massive ‘red-and-dead’ galaxies at z > 2. The ratio of the [C II], 12CO and far-infrared luminosities implies a strong far-ultraviolet field of G0 ∼ 103.25, which is at the high end of the far-ultraviolet fields seen in local starbursts, but weaker than the far-ultraviolet fields of most nearby ultraluminous infrared galaxies (ULIRGs). The high ratio of L[CII]/LFIR=1.0×10−3 observed in ALESS65.1, combined with L[CII]/LCO∼2300, is consistent with ALESS65.1 having more extended regions of intense star formation than local ULIRGs.