ALMA/NOEMA high-z star-forming galaxies

We detect ^12^CO (J_up_=2-5) emission lines in 50 sources, and [CI](^3^P_1_-^3^P_0_) emission in eight, at z=1.2-4.8 and with a median redshift of 2.9+/-0.2. By supplementing our data with literature sources, we construct a statistical CO spectral line energy distribution and find that the ^12^CO line luminosities in SMGs peak at J_up_~6, consistent with similar studies.

We also test the correlations of the CO, [CI], and dust as tracers of the gas mass, finding the three to correlate well, although the CO and dust mass as estimated from the 3-mm continuum are preferable. We estimate that SMGs lie mostly on or just above the star-forming main sequence, with a median gas depletion timescale, t_dep_=M_gas_/SFR, of 210+/-40Myr for our sample. Additionally, t_dep_ declines with redshift across z~1-5, while the molecular gas fraction, {mu}_gas_=M_gas_/M_*_, increases across the same redshift range.