Mathematics – Dynamical Systems
Scientific paper
Jul 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007dda....38.0503v&link_type=abstract
American Astronomical Society, DDA meeting #38, #5.03
Mathematics
Dynamical Systems
Scientific paper
I will present results of an analysis of N-body simulations of halo mergers designed to investigate the mechanisms responsible for driving mixing in phase-space and the evolution to dynamical equilibrium. The focus of the study is on mixing in energy and angular momentum. We show that mixing occurs in step-like fashion following pericenter passages of the halos. This makes mixing during a merger unlike other well known mixing processes such as phase mixing and chaotic mixing whose rates scale with local dynamical time. We conclude that the mixing process that drives the system to equilibrium is primarily a response to energy and angular momentum redistribution that occurs due to impulsive tidal shocking and dynamical friction rather than a result of chaotic mixing in a changing potential. We confirm previous findings that show that the majority of particles retain strong memory of their original kinetic energies and angular momenta but do experience changes in their potential energies owing to the tidal shocks they experience during pericenter passages. A significant fraction of mass ( 40%) in the merger remnant lies outside its formal virial radius and that this matter is ejected roughly uniformly from all radii outside the inner regions. We will also present preliminary results on the evolution of phase-space density in numerical simulations with the goal of understading the origin of the "power-law" phase-space density profiles of collisionless halos in hierarchical structure formation simulations. The implications of these results for our understanding of relaxation in collisionless dynamical systems will be emphasized. This work is funded in part by NSF grants AST-0307351, AST-0507666, AST-0239759 and PHY-0114422; NASA grant NAG5-13274; and DOE grant DE-FG02-04ER41323. SK acknowledges support from the Swiss National Science Foundation.
Bohn C.
Kazantzidis Stelios
Kravtsov Andrey V.
Valluri Monica
Vass Ileana M.
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