The [C II] emission as a molecular gas mass tracer in galaxies at low and high redshifts

Journal
Date Issued
2018
Author(s)
•
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.
•
•
Bournaud, F.
•
Walter, F.
•
Wang, T.
•
Elbaz, D.
•
Coogan, R. T.
DOI
Abstract
We present ALMA Band 9 observations of the [C II]158 μm emission for a sample of 10 main-sequence galaxies at redshift z ∼ 2, with typical stellar masses (log M⋆/M☉ ∼ 10.0-10.9) and star formation rates (∼35-115 M☉ yr-1). 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 and two tentative) and estimate ensemble averages including non-detections. The [C II]-to-infrared luminosity ratio ([C II]/LIR) of our sample is similar to that of local main-sequence galaxies (∼2 × 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 (α _[C II] ∼ 30 M☉/L☉) 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 ultraviolet light from star formation reprocessed by dust.
Volume
481
Issue
2
Start page
1976
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2018MNRAS.481.1976Z
Rights
open.access
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