Journal Article

Thermal instability in rotating galactic coronae

Carlo Nipoti

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 406, issue 1, pages 247-263
Published in print July 2010 | ISSN: 0035-8711
Published online July 2010 | e-ISSN: 1365-2966 | DOI:
Thermal instability in rotating galactic coronae

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The thermal stability of rotating, stratified, unmagnetized atmospheres is studied by means of linear-perturbation analysis, finding stability, overstability or instability, depending not only on the properties of the gas distribution but also on the nature of the perturbations. In the relevant case of distributions with outward-increasing specific entropy and angular momentum, axisymmetric perturbations grow exponentially, unless their wavelength is short enough that they are damped by thermal conduction; non-axisymmetric perturbations typically undergo overstable oscillations in the limit of zero conductivity, but are effectively stabilized by thermal conduction, provided rotation is differential. To the extent that the studied models are representative of the poorly constrained hot atmospheres of disc galaxies, these results imply that blob-like, cool overdensities are unlikely to grow in galactic coronae, suggesting an external origin for the high-velocity clouds of the Milky Way.

Keywords: hydrodynamics; instabilities; ISM: clouds; ISM: kinematics and dynamics; galaxies: formation

Journal Article.  8546 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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