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The influence of massive gas clouds on stellar velocity dispersions in galactic discs.

Lacey, C.G. (1984) 'The influence of massive gas clouds on stellar velocity dispersions in galactic discs.', Monthly notices of the Royal Astronomical Society., 208 (4). pp. 687-707.


This paper calculates the evolution of the three components of the velocity dispersion of the stars in a galactic disc due to the influence of massive gas clouds in circular orbits in the disc. We find that there are two phases in this evolution: an initial transient phase in which the shape of the velocity ellipsoid relaxes to a final shape depending only on the ratio Ω/κ of the circular to the radial epicyclic frequencies, followed by a steady heating phase in which for typical disc stars the velocity dispersion σ varies as dσ2/dt∝NcM2cν/σ2, where Nc and Mc are the surface density and mass of the clouds and ν is the vertical epicyclic frequency. We also find that the amount of stellar heating predicted will be comparable with that observed, for young stars at least, if cloud masses are near the upper end of the observationally allowed range, but that the ratio of vertical to horizontal velocity dispersions predicted disagrees with that observed. This may indicate that other disc heating mechanisms are important.

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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 1993 Royal Astronomical Society. Provided by the NASA Astrophysics Data System. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:No date available
Date deposited:26 February 2015
Date of first online publication:December 1984
Date first made open access:No date available

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