2017MNRAS.470.3775V

We present an extragalactic survey using observations from the Atacama Large Millimeter/submillimeter Array (ALMA) to characterize galaxy populations up to z = 0.35: the Valparaiso ALMA Line Emission Survey (VALES). We use ALMA Band-3 CO(1-0) observations to study the molecular gas content in a sample of 67 dusty normal star-forming galaxies selected from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). We have spectrally detected 49 galaxies at >5σ significance and 12 others are seen at low significance in stacked spectra. CO luminosities are in the range of (0.03-1.31) x 10¹⁰ K km s^–1 pc², equivalent to log(M_gas/M_☉) =8.9 – 10.9 assuming an α_CO = 4.6 (K km s^–1 pc²)^–1, which perfectly complements the parameter space previously explored with local and high-z normal galaxies. We compute the optical to CO size ratio for 21 galaxies resolved by ALMA at ∼3.5 arcsec resolution (6.5 kpc), finding that the molecular gas is on average ∼ 0.6 times more compact than the stellar component. We obtain a global Schmidt-Kennicutt relation, given by log[Σ_ SFR_/( M_☉  yr^–1 kpc^–2)] =(1.26 ±0.02) ×  log[Σ_MH2_/( M_☉ pc^–2)] - (3.6 ±0.2). We find a significant fraction of galaxies lying at 'intermediate efficiencies' between a long-standing mode of star formation activity and a starburst, specially at L_IR = 10^11–12 L_☉. Combining our observations with data taken from the literature, we propose that star formation efficiencies can be parametrized by log [ SFR/M_H2_] = 0.19 ×  (log L_IR - 11.45)-8.26- 0.41 ×[-4.84 (logL_IR-11.45) ]. Within the redshift range we explore (z < 0.35), we identify a rapid increase of the gas content as a function of redshift.