VALES I: the molecular gas content in star-forming dusty H-ATLAS galaxies up to z = 0.35
Rodighiero, G.; Ivison, R. J.; Cooray, A.; Ibar, E.; Baes, M.; Dannerbauer, H.; Dunne, L.; Dye, S.; Eales, S.; Michałowski, M. J.; Valiante, E.; van der Werf, P.; Hughes, T. M.; Smith, M. W. L.; Sansom, A. E.; Riechers, D.; Aravena, M.; Cassata, P.; Herrera-Camus, R.; Maddox, S. J.; Furlanetto, C.; Bourne, N.; Davies, L. J. M.; Lara-López, M. A.; Driver, S. P.; Molina, J.; Villanueva, V.
Chile, Mexico, Australia, United Kingdom, Germany, Belgium, United States, Spain, Brazil, Italy, Netherlands
Abstract
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 Valparaíso 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) × 1010 K km s-1 pc2, equivalent to log ({M}_{gas}/M_{⊙}) =8.9 - 10.9 assuming an αCO = 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 _{{M}_{H2}}/(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 LIR = 1011-12 L⊙. Combining our observations with data taken from the literature, we propose that star formation efficiencies can be parametrized by log [{SFR/{M}_{H_2}}] = 0.19 × {(log {L_{IR}} - 11.45)}-8.26- 0.41 × arctan [-4.84 (log {{L}_{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.