Mon. Not. R. Astron. Soc., 445, 2599-2620 (2014/December-2)
ALLSMOG: an APEX Low-redshift Legacy Survey for MOlecular Gas - I. Molecular gas scaling relations, and the effect of the CO/H2 conversion factor.
BOTHWELL M.S., WAGG J., CICONE C., MAIOLINO R., MOLLER P., ARAVENA M., DE BREUCK C., PENG Y., ESPADA D., HODGE J.A., IMPELLIZZERI C.M.V., MARTIN S., RIECHERS D. and WALTER F.
Abstract (from CDS):
We present ALLSMOG, the APEX Low-redshift Legacy Survey for MOlecular Gas. ALLSMOG is a survey designed to observe the CO(2 - 1) emission line with the APEX telescope, in a sample of local galaxies (0.01 < z < 0.03), with stellar masses in the range 8.5 < log(M*/M☉) < 10. This paper is a data release and initial analysis of the first two semesters of observations, consisting of 42 galaxies observed in CO(2 - 1). By combining these new CO(2 - 1) emission line data with archival H i data and SDSS optical spectroscopy, we compile a sample of low-mass galaxies with well-defined molecular gas masses, atomic gas masses, and gas-phase metallicities. We explore scaling relations of gas fraction and gas consumption time-scale, and test the extent to which our findings are dependent on a varying CO/H2 conversion factor. We find an increase in the H2/H i mass ratio with stellar mass which closely matches semi-analytic predictions. We find a mean molecular gas fraction for ALLSMOG galaxies of MH2/M* = (0.09-0.13), which decreases with stellar mass. This decrease in total gas fraction with stellar mass is in excess of some model predictions at low stellar masses. We measure a mean molecular gas consumption time-scale for ALLSMOG galaxies of 0.4-0.7 Gyr. We also confirm the non-universality of the molecular gas consumption time-scale, which varies (with stellar mass) from ∼ 100 Myr to ∼ 2 Gyr. Importantly, we find that the trends in the H2/H i mass ratio, gas fraction, and the non-universal molecular gas consumption time-scale are all robust to a range of recent metallicity-dependent CO/H2 conversion factors.
© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2014)
galaxies: abundances - galaxies: evolution - galaxies: formation - galaxies: statistics
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