Journal Article

Self-similar solutions for the dynamical condensation of a radiative gas layer

Kazunari Iwasaki and Toru Tsuribe

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 387, issue 4, pages 1554-1562
Published in print July 2008 | ISSN: 0035-8711
Published online July 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13294.x
Self-similar solutions for the dynamical condensation of a radiative gas layer

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A new self-similar solution describing the dynamical condensation of a radiative gas is investigated under a plane-parallel geometry. The dynamical condensation is caused by thermal instability. The solution is applicable to generic flow with a net cooling rate per unit volume and time ∝ρ2Tα, where ρ, T and α are the density, temperature and a free parameter, respectively. Given α, a family of self-similar solutions with one parameter η is found in which the central density and pressure evolve as follows: ρ(x= 0, t) ∝ (tct)−η/(2−α) and P(x= 0, t) ∝ (tct)(1−η)/(1−α), where tc is the epoch at which the central density becomes infinite. For η∼ 0 the solution describes the isochoric mode, whereas for η∼ 1 the solution describes the isobaric mode. The self-similar solutions exist in the range between the two limits; that is, for 0 < η < 1. No self-similar solution is found for α > 1. We compare the obtained self-similar solutions with the results of one-dimensional hydrodynamical simulations. In a converging flow, the results of the numerical simulations agree well with the self-similar solutions in the high-density limit. Our self-similar solutions are applicable to the formation of interstellar clouds (H i clouds and molecular clouds) by thermal instability.

Keywords: hydrodynamics; instabilities; ISM: structure

Journal Article.  4641 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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