Degenerate equilibrium states of collisionless stellar systems |
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Authors: | P-H Chavanis & J Sommeria |
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Institution: | Ecole Normale Supérieure de Lyon, 69364 Lyon Cedex 07, France |
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Abstract: | We study spherically symmetrical equilibrium states of collisionless stellar systems confined to a spherical box. These equilibrium states correspond to the statistics introduced by Lynden-Bell in his theory of 'violent relaxation', and are described by a Fermi–Dirac distribution function. We compute the corresponding equilibrium diagram and show that a global entropy maximum exists for any accessible control parameter. This equilibrium state shows a pronounced separation between a degenerate core and a halo. We therefore check that degeneracy is able to stop the gravitational collapse (of a collisionless system), and we propose a simple model for the 'core–halo' structure. We also discuss the relevance of our study for real galaxies or other astrophysical systems such as massive neutrinos. |
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Keywords: | celestial mechanics stellar dynamics galaxies: general |
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