Journal Article

Modelling H<sub>2</sub> formation in the turbulent interstellar medium: solenoidal versus compressive turbulent forcing

Milica Micic, Simon C. O. Glover, Christoph Federrath and Ralf S. Klessen

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 421, issue 3, pages 2531-2542
Published in print April 2012 | ISSN: 0035-8711
Published online April 2012 | e-ISSN: 1365-2966 | DOI:
Modelling H2 formation in the turbulent interstellar medium: solenoidal versus compressive turbulent forcing

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We present results from high-resolution 3D simulations of the turbulent interstellar medium (ISM) that study the influence of the nature of the turbulence on the formation of molecular hydrogen. We have examined both solenoidal (divergence-free) and compressive (curl-free) turbulent driving, and show that compressive driving leads to faster H2 formation, owing to the higher peak densities produced in the gas. The difference in the H2 formation rate can be as much as an order of magnitude at early times, but declines at later times as the highest density regions become fully molecular and stop contributing to the total H2 formation rate. We have also used our results to test a simple prescription suggested by Gnedin et al. for modelling the influence of unresolved density fluctuations on the H2 formation rate in large-scale simulations of the ISM. We find that this approach works well when the H2 fraction is small, but breaks down once the highest density gas becomes fully molecular.

Keywords: astrochemistry; molecular processes; turbulence; methods: numerical; ISM: clouds; ISM: molecules

Journal Article.  8186 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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