Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nitrogen Fractionation in External Galaxies   In star forming regions in our own Galaxy, the 14N/15N ratio is found to vary
from $\sim$ 100 in meteorites, comets and protoplanetary disks up to $\sim$
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 $\sim$440 and hence evaluate the contribution of
chemical reactions in the 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.

17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
24
The categories of this paper are: dg-ga
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex