Zanella, A, Daddi, E, Magdis, G, Diaz Santos, T, Cormier, D, Liu, D, Cibinel, A, Gobat, R, Dickinson, M, Sargent, M, Popping, G, Madden, S C, Bethermin, M, Hughes, T M, Valentino, F, Rujopakarn, W, Pannella, M, Bournaud, F, Walter, F, Wang, T, Elbaz, D and Coogan, R (2018) The [C II] emission as a molecular gas mass tracer in galaxies at low and high redshift. Monthly Notices of the Royal Astronomical Society, 481 (2). pp. 1976-1999. ISSN 0035-8711

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Abstract

We present ALMA Band 9 observations of the [C II]158um emission for a sample of 10 main-sequence galaxies at redshift z ~ 2, with typical stellar masses (log M*/Msun ~ 10.0 - 10.9) and star formation rates (~ 35 - 115 Msun/yr). Given the strong and well understood evolution of the interstellar medium from the present to z = 2, we investigate the behaviour of the [C II] emission and empirically identify its primary driver. We detect [C II] from six galaxies (four secure, two tentative) and estimate ensemble averages including non detections. The [C II]-to-infrared luminosity ratio (L[C II]/LIR) of our sample is similar to that of local main-sequence galaxies (~ 2 x 10^-3), and ~ 10 times higher than that of starbursts. The [C II] emission has an average spatial extent of 4 - 7 kpc, consistent with the optical size. Complementing our sample with literature data, we find that the [C II] luminosity correlates with galaxies' molecular gas mass, with a mean absolute deviation of 0.2 dex and without evident systematics: the [C II]-to-H2 conversion factor (alpha_[C II] ~ 30 Msun/Lsun) is largely independent of galaxies' depletion time, metallicity, and redshift. [C II] seems therefore a convenient tracer to estimate galaxies' molecular gas content regardless of their starburst or main-sequence nature, and extending to metal-poor galaxies at low and high redshifts. The dearth of [C II] emission reported for z > 6 - 7 galaxies might suggest either a high star formation efficiency or a small fraction of UV light from star formation reprocessed by dust.

Item Type:	Article
Schools and Departments:	School of Mathematical and Physical Sciences > Physics and Astronomy
Research Centres and Groups:	Astronomy Centre
Subjects:	Q Science > QB Astronomy
Depositing User:	Mark Sargent
Date Deposited:	28 Nov 2018 11:52
Last Modified:	28 Nov 2018 11:52
URI:	http://sro.sussex.ac.uk/id/eprint/80491

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