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Date and Time of the Query: 2019-06-26 T06:28:43 PDT
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For refcode 2014MNRAS.445.2378D:
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NED Abstract

Copyright by Royal Astronomical Society. 2014MNRAS.445.2378D Systematic variation of the ^12^CO/^13^CO ratio as a function of star formation rate surface density Davis, Timothy A. Abstract. We show that the ^12^CO/^13^CO intensity ratio in nearby galaxies varies systematically as a function of the star formation rate surface density (Sigma_SFR_) and gas surface density. The same effect is observed in different transitions, and in the ^12^CO/C^18^O ratio, while the ^13^CO/C^18^O ratio appears to remain constant as a function of Sigma_SFR_. We discuss the cause of these variations, considering both changes in the physical state of the gas and chemical changes that lead to abundance variations. We used the observed correlations with C^18^O to suggest that abundance variations are unlikely to be causing the systematic trend observed with Sigma_SFR_, and thus that the mean gas temperature and/or velocity dispersion are systematically higher in higher SFR surface density regions. We present the best-fitting relations between Sigma_SFR_ and the ^12^CO/^13^CO and ^12^CO/C^18^O ratios, and discuss how this effect can help us predict CO isotope emission from galaxies across the known Universe. Key words: ISM: abundances, ISM: molecules, galaxies: ISM, galaxies: star formation
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