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arXiv · 1407.0463

Detection of molecular gas in an ALMA [CII]-identified Submillimetre Galaxy at z = 4.44

M. T. Huynh·A. E. Kimball·R. P. Norris·Ian Smail·K. E. Chow·K. E. K. Coppin·B. H. C. Emonts·R. J. Ivison·V. Smolcic·A. M. Swinbank
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Abstract

We present the detection of $^{12}$CO(2-1) in the $z = 4.44$ submillimetre galaxy ALESS65.1 using the Australia Telescope Compact Array. A previous ALMA study of submillimetre galaxies in the Extended Chandra Deep Field South determined the redshift of this optically and near-infrared undetected source through the measurement of [CII] 157.74 $\mu$m emission. Using the luminosity of the $^{12}$CO(2-1) emission we estimate the gas mass to be $M_{\rm gas} \sim 1.7 \times 10^{10}$ ${\rm M}_\odot$. The gas depletion timescale of ALESS65.1 is $\sim$ 25 Myr, similar to other high redshift submillimetre galaxies and consistent with $z > 4$ SMGs being the progenitors of massive "red-and-dead" galaxies at $z > 2$. The ratio of the [CII], $^{12}$CO and far-infrared luminosities implies a strong far-ultraviolet field of $G_0 \sim 10^{3.25}$, 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 ULIRGs. The high ratio of $L_{\rm [CII]}/L_{\rm FIR} = 1.0 \times 10^{-3}$ observed in ALESS65.1, combined with $L_{\rm [CII]}/L_{\rm CO} \sim 2300$, is consistent with ALESS65.1 having more extended regions of intense star formation than local ULIRGs.

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M. T. Huynh, A. E. Kimball, R. P. Norris, Ian Smail, K. E. Chow, K. E. K. Coppin, B. H. C. Emonts, R. J. Ivison, V. Smolcic, A. M. Swinbank. 2014-07-02. Detection of molecular gas in an ALMA [CII]-identified Submillimetre Galaxy at z = 4.44. https://doi.org/10.1093/mnrasl/slu077

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