Opened 5 years ago

# update H2 grain catalysis rate

Reported by: Owned by: Gary J. Ferland nobody major chemical network trunk

### Description

this paper also uses the update grain catalysis theory now used in the meudon code

Title:
Full SED fitting with the KOSMA-\tau\ PDR code - I. Dust modelling
Authors:
Röllig, M.; Szczerba, R.; Ossenkopf, V.; Glück, C.
Publication:
eprint arXiv:1211.3546
Publication Date:
11/2012
Origin:
ARXIV
Keywords:
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Galaxy Astrophysics
Comment:
accepted for publication in A&A; doi:10.1051/0004-6361/201118190
Bibliographic Code:
2012arXiv1211.3546R
Abstract
We revised the treatment of interstellar dust in the KOSMA-\tau\
PDR model code to achieve a consistent description of the
dust-related physics in the code. The detailed knowledge of the
dust properties is then used to compute the dust continuum emission
together with the line emission of chemical species. We coupled the
KOSMA-\tau\ PDR code with the MCDRT (multi component dust radiative
transfer) code to solve the frequency-dependent radiative transfer
equations and the thermal balance equation in a dusty clump under
the assumption of spherical symmetry, assuming thermal equilibrium
in calculating the dust temperatures, neglecting non-equilibrium
effects. We updated the calculation of the photoelectric heating
and extended the parametrization range for the photoelectric
heating toward high densities and UV fields. We revised the
computation of the H2 formation on grain surfaces to include the
Eley-Rideal effect, thus allowing for high-temperature H2
formation. We demonstrate how the different optical properties,
temperatures, and heating and cooling capabilities of the grains
influence the physical and chemical structure of a model cloud. The
most influential modification is the treatment of H2 formation on
grain surfaces that allows for chemisorption. This increases the
total H2 formation significantly and the connected H2 formation
heating provides a profound heating contribution in the outer
layers of the model clumps. The contribution of PAH surfaces to the
photoelectric heating and H2 formation provides a boost to the
temperature of outer cloud layers, which is clearly traced by
high-J CO lines. Increasing the fraction of small grains in the
dust size distribution results in hotter gas in the outer cloud
layers caused by more efficient heating and cooler cloud centers,
which is in turn caused by the more efficient FUV extinction.


### comment:1 Changed 4 years ago by Gary J. Ferland

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