IAU Symposium Abstract S186-033P

Star Formation in Collisions Between Two Gas-Rich Disk Galaxies

Curtis Struck1
1 Dept. of Physics \& Astronomy, Iowa State Univ., Ames, IA 50011 USA
< curt@iastate.edu >

Results of three-dimensional (SPH) simulations of collisions between two model galaxies, each consisting of a rigid halo and a gas-rich disk component, are presented. The companion to primary mass ratio is typically 0.2 - 0.35. Simple models of radiative cooling and heating from young star activity are also included in the simulations. Star formation is assumed to occur when the local gas density exceeds a threshold value. In these collisions the primary gas disk remains largely intact, though a gas bridge is splashed out between the two galaxies. The companion gas disk is usually disrupted by the impact, but reforms via accretion from the bridge. Star formation occurs in waves in the primary. The bridge is predicted to have essentially no ongoing star formation. These results agree with observations of the Cartwheel and VII Zw 466 ring galaxies. Star formation becomes possible in the companions after their gas disk reforms out of infalling bridge material. However, it is often delayed there, and in the central regions of the primary, apparently as a result of accretion heating.