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2013MNRAS.434L..56J - Mon. Not. R. Astron. Soc., 434, L56-L60 (2013/September-1)

Jeans instability criterion modified by external tidal field.


Abstract (from CDS):

The well-known Jeans criterion describes the onset of instabilities in an infinite, homogeneous, self-gravitating medium supported by pressure. Most realistic astrophysical systems, however, are not isolated - instead they are under the influence of an external field such as the tidal field due to a neighbour. Here, we do a linear perturbation analysis for a system in an external field and obtain a generalized dispersion relation that depends on the wavenumber, the sound speed and also the magnitude of the tidal field. A typical, disruptive tidal field is shown to make the system more stable against perturbations, and results in a higher effective Jeans wavelength. The minimum mass that can become unstable is then higher (super-Jeans) than the usual Jeans mass. Conversely, in a compressive tidal field, perturbations can grow even when the mass is lower (sub-Jeans). This approach involving the inclusion of tidal field opens up a new way of looking at instabilities in gravitating systems. The treatment is general and the simple analytical form of the modified Jeans criterion obtained makes it easily accessible.

Abstract Copyright: © 2013 The Author Published by Oxford University Press on behalf of the Royal Astronomical Society (2013)

Journal keyword(s): hydrodynamics - instabilities - galaxies: kinematics and dynamics - galaxies: star formation - galaxies: structure

Simbad objects: 14

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