HD/H$_2$ ratio in the diffuse interstellar medium
Abstract
We present a semi-analytical description of the relative HD/H2 abundance in the diffuse interstellar medium. We found three asymptotics of the relative HD/H abundance for different parts of the medium and their dependence on the physical parameters, namely, number density, intensity of the ultraviolet field, cosmic-ray ionization rate and metallicity. Our calculations are in a good agreement with the full network calculations using Meudon PDR code. We found that in the case of low metallicity and/or higher cosmic ray ionization rate, HD formation rate is significantly enhanced, HD/H2 ratio increases, and the DI/HD transition occurs at a lower penetration depth of UV radiation than the HI/H transition. This can explain the observed difference in the HD/H abundance between the local and high-redshift measurements.
Cite
@article{arxiv.1911.12325,
title = {HD/H$_2$ ratio in the diffuse interstellar medium},
author = {S. A. Balashev and D. N. Kosenko},
journal= {arXiv preprint arXiv:1911.12325},
year = {2020}
}
Comments
5 pages, 3 figures, accepted for publication in MNRAS letters