2017A&A...604A..53C

We present the final data release of the APEX low-redshift legacy survey for molecular gas (ALLSMOG), comprising CO(2-1) emission line observations of 88 nearby, low-mass (10^8.5<M_*[M_☉]<10¹⁰) star-forming galaxies carried out with the 230GHz APEX-1 receiver on the APEX telescope. The main goal of ALLSMOG is to probe the molecular gas content of more typical and lower stellar mass galaxies than have been studied by previous CO surveys. We also present IRAM 30m observations of the CO(1-0) and CO(2-1) emission lines in nine galaxies aimed at increasing the M_*<10⁹M_☉ sample size.In this paper we describe the observations, data reduction and analysis methods and we present the final CO spectra together with archival HI 21cm line observations for the entire sample of 97 galaxies. At the sensitivity limit of ALLSMOG, we register a total CO detection rate of 47%. Galaxies with higher M_*, SFR, nebular extinction (A_V), gas-phase metallicity (O/H), and HI gas mass have systematically higher CO detection rates.In particular, the parameter according to which CO detections and non-detections show the strongest statistical differences is the gas-phase metallicity, for any of the five metallicity calibrations examined in this work. We investigate scaling relations between the CO(1-0) line luminosity (L'_CO(1–0)) and galaxy-averaged properties using ALLSMOG and a sub-sample of COLD GASS for a total of 185 sources that probe the local main sequence (MS) of star-forming galaxies and its ±0.3dex intrinsic scatter from M_*=10^8.5M_☉ to M_*=10¹¹M_☉. L'_CO(1–0) is most strongly correlated with the SFR, but the correlation with M_* is closer to linear and almost comparably tight. The relation between L'_CO(1–0) and metallicity is the steepest one, although deeper CO observations of galaxies with A_V<0.5mag may reveal an as much steep correlation with A_V. Our results suggest that star-forming galaxies across more than two orders of magnitude in M_* obey similar scaling relations between CO luminosity and the galaxy properties examined in this work. Besides SFR, the CO luminosity is likely most fundamentally linked to M_*, although we note that stellar mass alone cannot explain all of the variation in CO emission observed as a function of O/H and M_HI.