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Session 11 - Elliptical Galaxies.
Display session, Monday, June 10
Two dimensional perfect elliptic disk models with minimal streaming were tested for stability by N-body integration. The perfect elliptic disks are the two dimensional limiting case of the perfect ellipsoids, in which the density is stratified on concentric triaxial ellipsoids, and the potential is exactly integrable: they could be viewed as models for both galactic bars and elliptical galaxies. Distribution functions f(E,I_3) which self-consistently reproduce the density distribution can be found numerically but are not unique: the angular momentum can vary from a maximum to a minimum value. The maximum-streaming models were investigated by Levine amp; Sparke (1994); here results are presented for the minimal angular momentum case. A modified marching scheme was used to compute the relative contributions to the final disk model of first a set of loop orbits, and then a set of box orbits. The placement of particles along the orbits for the N-body integrator was done with a ``quiet start'' technique which makes the distribution of particles as smooth as possible, thus minimizing initial random perturbations. All of these methods can easily be extended to work for integrable potentials in any number of dimensions.
Program listing for Monday