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Jeans instability criterion modified by external tidal field

Jog, Chanda J (2013) Jeans instability criterion modified by external tidal field. In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 434 (1). L56-L60.

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Official URL: http://dx.doi.org/10.1093/mnrasl/slt077


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.

Item Type: Journal Article
Additional Information: copyright for this article belongs to OXFORD UNIV PRESS,ENGLAND
Keywords: hydrodynamics; instabilities; galaxies: kinematics and dynamics; galaxies: star formation; galaxies: structure
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Depositing User: Id for Latest eprints
Date Deposited: 28 Dec 2013 06:17
Last Modified: 28 Dec 2013 06:25
URI: http://eprints.iisc.ac.in/id/eprint/47989

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