Stellar and gas dynamics of interacting ring galaxies
The development of ring and arc structure due to the collision of a spherical galaxy normal to the plane of a disk galaxy is studied with analytic and numerical models. In the numerical model, the disk contains one-tenth of its mass in gas and the hydrodynamics equations are solved using the method of Smoothed Particle Hydrodynamics. It is found that axisymmetric collisions between equal mass galaxies produce a strong expanding ring with a complex three-dimensional structure. Density and velocity profiles for the disk are given. Off-center collisions produce greater gas density enhancements in the non-nuclear portion of the disk when compared to the axisymmetric case. Strong gas interactions in the off-center collisions cause the stellar and gaseous flows to follow separate trajectories. If star formation is associated with the strongest gas shocks and greatest gas densities, the morphology of ring galaxies is strongly dependent on a proper treatment of gas dynamical processes. A Rayleigh-Taylor instability is believed to be present in the strong shock regions, which could contribute to the knotty structure observed in ring galaxies.
ring galaxy, axisymmetric collisions, gas interactions
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign