Nitrogen fractionation in external galaxies. Issue 4 (30th April 2019)

• Record Type: Journal Article
• Authors: Viti, Serena; Fontani, Francesco; Jiménez-Serra, Izaskun; Holdship, Jonathan
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 486:Issue 4(2019)
• Page Start: 4805
• Page End: 4812
• Publication Date: 2019-04-30
• Subjects: ISM: abundances -- ISM: molecules -- galaxies: ISM; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz1172
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: In star-forming regions in our own Galaxy, the 14 N/ 15 N 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 14 N/ 15 N 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.