1. Deriving a multivariate αCO conversion function using the [C II]/CO (1-0) ratio and its application to molecular gas scaling relations.
- Author
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Accurso, G., Saintonge, A., Catinella, B., Cortese, L., Davé, R., Dunsheath, S. H., Genzel, R., Gracia-Carpio, J., Heckman, T. M., Jimmy, Kramer, C., Cheng Li, Lutz, K., Schiminovich, D., Schuster, K., Sternberg, A., Sturm, E., Tacconi, L. J., Tran, K. V., and Wang, J.
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RADIO lines , *GALAXIES , *BAYESIAN analysis , *GALACTIC evolution , *INTERSTELLAR medium - Abstract
We present Herschel PACS observations of the [C II] 158 μm emission line in a sample of 24 intermediate mass (9 < logM*/M☉ < 10) and low metallicity (0.4 < Z/Z☉ < 1.0) galaxies from the xCOLD GASS survey. In combination with IRAM CO(1-0) measurements, we establish scaling relations between integrated and molecular region L[C II]/LCO(1-0) ratios as a function of integrated galaxy properties. A Bayesian analysis reveals that only two parameters, metallicity and offset from the main sequence, Δ(MS), are needed to quantify variations in the luminosity ratio; metallicity describes the total dust content available to shield CO from UV radiation, while Δ(MS) describes the strength of this radiation field. We connect the L[C II]/LCO(1-0) ratio to the CO-to-H2 conversion factor and find a multivariate conversion function, which can be used up to z ~ 2.5. This function depends primarily on metallicity, with a second-order dependence on Δ(MS). We apply this to the full xCOLD GASS and PHIBSS1 surveys and investigate molecular gas scaling relations. We find a flattening of the relation between gas mass fraction and stellar mass at logM* < 10.0. While the molecular gas depletion time varies with sSFR, it is mostly independent of mass, indicating that the low LCO/SFR ratios long observed in low-mass galaxies are entirely due to photodissociation of CO and not to an enhanced star formation efficiency. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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