S. Bialy, and A. Sternberg. (2016)cite arxiv:1601.02608Comment: ApJ. submitted. 13 pages, 9 Figures.
Abstract
We present a simple analytic procedure for generating atomic-to-molecular
(HI-to-H$_2$) density profiles for optically thick clouds illuminated by
far-ultraviolet radiation. Our procedure is based on the analytic theory for
the structure of 1D HI/H$_2$ photon-dominated regions, presented by Sternberg
et al. (2014). Depth-dependent HI and H$_2$ density fractions may be computed
for arbitrary gas density, far-ultraviolet field intensity, and the metallicity
dependent H$_2$ formation rate coefficient, and dust absorption cross section.
We use our procedure to generate a set of HI-to-H$_2$ transition profiles for a
wide range of conditions, from the weak- to strong-field limits, and from
super-solar down to low metallicities. We show that if presented as functions
of dust optical depth the HI and H$_2$ density profiles depend primarily on the
Sternberg "$G$ parameter" (dimensionless) that determines the dust
optical depth associated with the total photodissociated HI column. We derive a
universal analytic formula for the HI-to-H$_2$ transition points as a function
of just $G$. Our formula will be useful for interpreting emission-line
observations of HI/H$_2$ interfaces, for estimating star-formation thresholds,
and for sub-grid components in hydrodynamics simulations.
%0 Generic
%1 bialy2016analytic
%A Bialy, Shmuel
%A Sternberg, Amiel
%D 2016
%K H2 HI dissociation formation molecules
%T Analytic HI-to-H2 Photodissociation Transition Profiles
%U http://arxiv.org/abs/1601.02608
%X We present a simple analytic procedure for generating atomic-to-molecular
(HI-to-H$_2$) density profiles for optically thick clouds illuminated by
far-ultraviolet radiation. Our procedure is based on the analytic theory for
the structure of 1D HI/H$_2$ photon-dominated regions, presented by Sternberg
et al. (2014). Depth-dependent HI and H$_2$ density fractions may be computed
for arbitrary gas density, far-ultraviolet field intensity, and the metallicity
dependent H$_2$ formation rate coefficient, and dust absorption cross section.
We use our procedure to generate a set of HI-to-H$_2$ transition profiles for a
wide range of conditions, from the weak- to strong-field limits, and from
super-solar down to low metallicities. We show that if presented as functions
of dust optical depth the HI and H$_2$ density profiles depend primarily on the
Sternberg "$G$ parameter" (dimensionless) that determines the dust
optical depth associated with the total photodissociated HI column. We derive a
universal analytic formula for the HI-to-H$_2$ transition points as a function
of just $G$. Our formula will be useful for interpreting emission-line
observations of HI/H$_2$ interfaces, for estimating star-formation thresholds,
and for sub-grid components in hydrodynamics simulations.
@misc{bialy2016analytic,
abstract = {We present a simple analytic procedure for generating atomic-to-molecular
(HI-to-H$_2$) density profiles for optically thick clouds illuminated by
far-ultraviolet radiation. Our procedure is based on the analytic theory for
the structure of 1D HI/H$_2$ photon-dominated regions, presented by Sternberg
et al. (2014). Depth-dependent HI and H$_2$ density fractions may be computed
for arbitrary gas density, far-ultraviolet field intensity, and the metallicity
dependent H$_2$ formation rate coefficient, and dust absorption cross section.
We use our procedure to generate a set of HI-to-H$_2$ transition profiles for a
wide range of conditions, from the weak- to strong-field limits, and from
super-solar down to low metallicities. We show that if presented as functions
of dust optical depth the HI and H$_2$ density profiles depend primarily on the
Sternberg "$\alpha G$ parameter" (dimensionless) that determines the dust
optical depth associated with the total photodissociated HI column. We derive a
universal analytic formula for the HI-to-H$_2$ transition points as a function
of just $\alpha G$. Our formula will be useful for interpreting emission-line
observations of HI/H$_2$ interfaces, for estimating star-formation thresholds,
and for sub-grid components in hydrodynamics simulations.},
added-at = {2016-01-13T19:32:26.000+0100},
author = {Bialy, Shmuel and Sternberg, Amiel},
biburl = {https://www.bibsonomy.org/bibtex/243b04639d171536c18351b3fe1493546/miki},
description = {[1601.02608] Analytic HI-to-H2 Photodissociation Transition Profiles},
interhash = {b59a936dfbe2cd47689c6334b6f594af},
intrahash = {43b04639d171536c18351b3fe1493546},
keywords = {H2 HI dissociation formation molecules},
note = {cite arxiv:1601.02608Comment: ApJ. submitted. 13 pages, 9 Figures},
timestamp = {2016-01-13T19:32:26.000+0100},
title = {Analytic HI-to-H2 Photodissociation Transition Profiles},
url = {http://arxiv.org/abs/1601.02608},
year = 2016
}