A multiwavelength consensus on the main sequence of star-forming galaxies at z ∼ 2

Abstract

We compare various star formation rate (SFR) indicators for star-forming\ngalaxies at $1.4<z<2.5$ in the COSMOS field. The main focus is on the SFRs from\nthe far-IR (PACS-Herschel data) with those from the ultraviolet, for galaxies\nselected according to the BzK criterion. FIR-selected samples lead to a vastly\ndifferent slope of the SFR-stellar mass ($M_*$) relation, compared to that of\nthe dominant main sequence population as measured from the UV, since the FIR\nselection picks predominantly only a minority of outliers. However, there is\noverall agreement between the main sequences derived with the two SFR\nindicators, when stacking on the PACS maps the BzK-selected galaxies. The\nresulting logarithmic slope of the SFR-{$M_*$} relation is $\\sim0.8-0.9$, in\nagreement with that derived from the dust-corrected UV-luminosity. Exploiting\ndeeper 24$\\mu$m-Spitzer data we have characterized a sub-sample of galaxies\nwith reddening and SFRs poorly constrained, as they are very faint in the $B$\nband. The combination of Herschel with Spitzer data have allowed us to largely\nbreak the age/reddening degeneracy for these intriguing sources, by\ndistinguishing whether a galaxy is very red in B-z because of being heavily\ndust reddened, or whether because star formation has been (or is being)\nquenched. Finally, we have compared our SFR(UV) to the SFRs derived by stacking\nthe radio data and to those derived from the H$\\alpha$ luminosity of a sample\nof star-forming galaxies at $1.4<z<1.7$. The two sets of SFRs are broadly\nconsistent as they are with the SFRs derived from the UV and by stacking the\ncorresponding PACS data in various mass bins.\n