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HI in Molecular Clouds: Irradiation by FUV plus Cosmic Rays by Sternberg, Amiel; Bialy, Shmuel; Gurman, Alon is a scholarly article available to read on EtoBox.

What is HI in Molecular Clouds: Irradiation by FUV plus Cosmic Rays about?

We extend the analytic theory presented by Sternberg et al. (2014) and Bialy & Sternberg (2016) for the production of atomic hydrogen (HI) via FUV photodissociation at the boundaries of dense interstellar molecular (H$_2$) clouds, to also include the effects of penetrating (low-energy) cosmic-rays for the growth of the total HI column densities. We compute the steady-state abundances of the HI and H$_2$ in one-dimensional gas slabs in which the FUV photodissociation rates are reduced by depth-dependent H$_2$ self-shielding and dust absorption, and in which the cosmic-ray ionization rates are either constant or reduced by transport effects. The solutions for the HI and H$_2$ density profiles and the integrated HI columns, depend primarily on the ratios $I_{\rm UV}/Rn$ and $\zeta/Rn$, where $I_{\rm UV}$ is the intensity of the photodissociating FUV field, $\zeta$ is the H$_2$ cosmic-ray ionization rate, $n$ is the hydrogen gas density, and $R$ is the dust-surface H$_2$ formation rate coefficient. We present computations for a wide range of FUV field strengths, cosmic-ray ionization rates, and dust-to-gas ratios. We develop analytic expressions for the growth of the HI column densitie

Author

Sternberg, Amiel; Bialy, Shmuel; Gurman, Alon

Published

2023

Language

EN