Nitrogen fractionation in external galaxies
Abstract
In star-forming regions in our own Galaxy, the 14N/15N ratio is found to vary from ∼100 in meteorites, comets, and protoplanetary discs up to ∼1000 in pre-stellar and star-forming cores, while in external galaxies the very few single-dish large-scale measurements of this ratio lead to values of 100-450. The extent of the contribution of isotopic fractionation to these variations is, to date, unknown. In this paper, we present a theoretical chemical study of nitrogen fractionation in external galaxies in order to determine the physical conditions that may lead to a spread of the 14N/15N ratio from the solar value of ∼440 and hence evaluate the contribution of chemical reactions in the interstellar medium (ISM) to nitrogen fractionation. We find that the main cause of ISM enrichment of nitrogen fractionation is high gas densities, aided by high fluxes of cosmic rays.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 2019
- DOI:
- 10.1093/mnras/stz1172
- arXiv:
- arXiv:1904.11725
- Bibcode:
- 2019MNRAS.486.4805V
- Keywords:
-
- ISM: abundances;
- ISM: molecules;
- galaxies: ISM;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted by MNRAS