The dynamical evolution of rotating stellar systems.

The evolution of dense rotating systems is studied through the use of N-body simulations. The initial configuration for each experiment is an isotropic Kuzmin-Kutuzov model. Hernquist's tree code is utilized to simulate the dynamical evolution, with dynamical relaxation produced by the graininess of the low-N potential field. We have modified the code to simulate physical stellar collisions, stellar evolution, mass loss and remnant formation, and star formation. Material ejected though stellar mass loss was allowed to escape some systems and was reprocessed through star formation in others. Systems whose constituent particles follow a Salpeter initial mass function rapidly undergo core collapse through Spitzer's mass segregation instability. The lump of high mass stars which condenses at the center wanders about the core in Brownian motion. All rotationally flattened systems show a decrease in flattening with time. Angular momentum transport is directed radially outward: systems containing equal mass stars transport angular momentum more efficiently than do systems following a Salpeter spectrum. In all systems the velocity dispersion in the halo evolves toward a radially biased state. In systems containing a central black hole, the dispersion becomes tangentially biased in the core, whereas it remains isotropic in systems with no black hole. Collisions occur primarily in the core; energy equipartition causes the merger remnants to sink to the system center. In systems where ejecta (due to stellar evolution processes) are allowed to escape the system, mass loss from the heavy core stars temporarily reduces the core density and collision rate. Collisions tend to produce a single dominant stellar merger remnant, as opposed to a swarm of intermediate-mass stars. In cases where we have suppressed all processes except relaxation and physical collisions, objects with greater flattening: produce larger dominant stars. Most of the simulations performed reproduced the ratio of the central collision time scale to the central relaxation time scale found in the dwarf elliptical galaxy M32; many reproduced other features as well. The rapid central evolution of these systems due to collisions and relaxation suggests that we are either viewing M32 at a peculiar moment in its history, or that its dynamically-inferred central density is at least in part due to the present of a massive dark object, presumably a black hole.PhDAstronomyPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/130194/2/9721940.pd