Schedule Jan 17, 2009
Formation of Globular Clusters in Colliding Galaxies
Takayuki Saitoh (Nat'l Obs. of Japan)

We use very high-resolution simulations of galaxy-galaxy collisions to study the formation of globular clusters. Our simulations resolve the multiphase nature of the inter-stellar medium, and thus can be used to locate star-forming sites robustly. We use a total of 1.5 X 10^7 particles to represent two gas-rich progenitor galaxies. During the first encounter, a very large filament is formed at the collision interface of the colliding galaxies. The filament's mass is ~ 10^9 Msun, and it consists mostly of dense and cold gases. The peak star formation rate in the filament reaches ~ 15 Msun yr^-1. Eleven self-bound star clusters are located in the giant filament after the starburst. These star clusters have masses of ~ 10^(6-7) Msun. They have little dark matter content. Star formation in individual star clusters is quenched in about ~ 10^7 yr; feedback effects of Type II supernovae are significant in the small mass systems. Consequently, stars in a cluster have a nearly uniform metallicity composition. The formation efficiency of star clusters in the filament, Mstars/Mfilament, is found to be ~ 0.18. at the final stage of the star cluster formation. Star clusters formed in this manner have simialr characteristic to observed metal-rich globular clusters.

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