2020MNRAS.497.4333V

In the interstellar medium carbon exists in the form of two stable isotopes ¹²C and ¹³C and their ratio is a good indicator of nucleosynthesis in galaxies. However, chemical fractionation can potentially significantly alter this ratio and in fact observations of carbon fractionation within the same galaxy has been found to vary from species to species. In this paper, we theoretically investigate the carbon fractionation for selected abundant carbon-bearing species in order to determine the conditions that may lead to a spread of the ¹²C/¹³C ratio in external galaxies. We find that carbon fractionation is sensitive to almost all the physical conditions we investigated, it strongly varies with time for all species but CO, and shows pronounced differences across species. Finally, we discuss our theoretical results in the context of the few observations of the ¹²C/¹³C in both local and higher redshift galaxies.