AAS 207th Meeting, 8-12 January 2006
Session 80 Evolution of Galaxies, Galaxies Surveys II
Poster, Tuesday, 9:20am-6:30pm, January 10, 2006, Exhibit Hall

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[80.02] Violent Relaxation and Chaos in Galactic Mergers

I.M. Vass (University of Florida, Gainesville), M. Valluri (Univ. of Chicago), S. Kazantzidis, A.V. Kravtsov (Univ. of Zurich & Univ. of Chicago), C.L. Bohn (Northern Illinois University)

We investigate the mechanisms responsible for violent relaxation by analyzing N-body simulations of the merger and relaxation of dark matter halos. The principal goal of this study is to establish whether there is a connection between the mixing in phase-space that occurs during gravitational collapse (``violent relaxation") and chaotic mixing in equilibrium potentials. We identify several new measures to quantify chaoticity in phase-space in systems with rapidly varying potentials and try to establish a connection between the global relaxation of the potential and microscopic relaxation in phase-space. We demonstrate (by use of similar measures in an isolated N-body halo simulation) that only the particles in the inner 30-40% of the mass of the halo are fully mixed in phase-space and that this section corresponds to the region where local crossing times are short enough that the orbits have experienced significant mixing via the same kind of processes as those that occur in isolated systems. The primary difference appears in the volume of phase-space available to the particles in the two systems. We discuss implications of these results to our understanding of the formation of cuspy dark matter halos and the origin of power-law phase-space density distributions.

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