A Counterpart to the radial-orbit instability in triaxial stellar systems

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Title: A Counterpart to the radial-orbit instability in triaxial stellar systems
Author: Antonini, Fabio; Capuzzo-Dolcetta, Roberto; Merritt, David
Abstract: Self-consistent solutions for triaxial mass models are highly non-unique. In general, some of these solutions might be dynamically unstable, making them inappropriate as descriptions of steady-state galaxies. Here we demonstrate for the first time the existence in triaxial galaxy models of an instability similar to the radial-orbit instability of spherical models. The instability manifests itself when the number of box orbits, with predominantly radially motions, is sufficiently large. N-body simulations verify that the evolution is due neither to chaotic orbits nor to departures of the model from selfconsistency, but rather to a collective mode. The instability transforms the triaxial model into a more prolate, but still triaxial, configuration. Stable triaxial models are obtained when the mass contribution of radial orbits is reduced. The implications of our results for the shapes of dark-matter halos are discussed.
Description: Also archived in: arXiv:0901.4485 v1 Jan 28, 2009
Record URI: http://hdl.handle.net/1850/8325
Date: 2009-01

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