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S.A. Lamb (UIUC), N.C. Hearn, J.A. Van Schelt (U.Chicago), I.S. Marinova (U.Texas)
We report the results of a series of moderately high-resolution N-body simulations of collision and subsequent merger of pairs of comparable mass galaxies that have been chosen to represent typical members of galaxy clusters. The model disk galaxies have dark matter halos approximately four times more massive than the combined stellar mass, and have disk-bulge ratios similar to either Sab or S0 galaxies. Both disk-disk galaxy collisions and elliptical-disk galaxy collisions have been investigated, and their long-term evolution to a merged state followed. We have used the tree-gravity part of the 'Tillamook' N-body code of Hearn (2002, Ph.D Thesis, UIUC), with between 250,000 and a million particles. We simulate the merger of galaxies approaching at nearly the escape velocity with a range of impact parameters that lead to both slightly off-center and glancing collisions. Following these mergers, we find that by a time of approximately 2 Gyr past closest initial approach, a central high-density region has formed in the combined dark matter halo with a radius of approximately 80 kpc, if we scale our model disk galaxies to the mass and radius of the Milky Way. Within the new, asymmetric, extended dark matter halos formed in the mergers, are long-lived streams, 'fans', and shells of stellar material. Most of the dark matter remains in the region occupied by luminous matter throughout the simulation, but some amount is spread to very large radii and between 20% and 30% would be lost to the overall potential in a cluster. (We acknowledge support from DOE LLNL B506657. The simulations were performed on the Turing Computer Cluster at UIUC.)
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.