ZANELLA, ANITAANITAZANELLADaddi, E.E.DaddiMagdis, G.G.MagdisDiaz Santos, T.T.Diaz SantosCormier, D.D.CormierLiu, D.D.LiuCibinel, A.A.CibinelGobat, R.R.GobatDickinson, M.M.DickinsonSargent, M.M.SargentPopping, G.G.PoppingMadden, S. C.S. C.MaddenBethermin, M.M.BetherminHughes, T. M.T. M.HughesValentino, F.F.ValentinoRujopakarn, W.W.RujopakarnPannella, M.M.PannellaBournaud, F.F.BournaudWalter, F.F.WalterWang, T.T.WangElbaz, D.D.ElbazCoogan, R. T.R. T.Coogan2020-10-022020-10-0220180035-8711http://hdl.handle.net/20.500.12386/27552We 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<SUB>⋆</SUB>/M<SUB>☉</SUB> ∼ 10.0-10.9) and star formation rates (∼35-115 M<SUB>☉</SUB> yr<SUP>-1</SUP>). 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]/L<SUB>IR</SUB>) of our sample is similar to that of local main-sequence galaxies (∼2 × 10<SUP>-3</SUP>), 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-H<SUB>2</SUB> conversion factor (α _[C II] ∼ 30 M<SUB>☉</SUB>/L<SUB>☉</SUB>) 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.STAMPAenArticle10.1093/mnras/sty23942-s2.0-85058453548000449764000040https://academic.oup.com/mnras/article-abstract/481/2/1976/50901722018MNRAS.481.1976ZFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_6 Stars and stellar systems