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.

Publication Date

10-21-2009

Comments

This is a pre-copyedited, author-produced version of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review.

F. Antonini, R. Capuzzo-Dolcetta, D. Merritt; A counterpart to the radial-orbit instability in triaxial stellar systems, Monthly Notices of the Royal Astronomical Society, Volume 399, Issue 2, 21 October 2009, Pages 671–682

The version of record is available online at: https://doi.org/10.1111/j.1365-2966.2009.15342.x

Also archived in: arXiv:0901.4485 v1 Jan 28, 2009

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type

Article

Department, Program, or Center

School of Physics and Astronomy (COS)

Campus

RIT – Main Campus

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