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abstract
Collisions and mergers of between galaxies are spectacular events that may have profound implications for galactic evolution. A complete description of what happens in a merger challenges our understanding of not only stellar and gas dynamics, but also the process of star formation. However, there exists a rare class of colliding galaxies, the ring galaxies, which represent a more tractable dynamical problem than a more general merger. Ring galaxies are thought to form when an intruder galaxy makes a near ``bulls-eye'' collision with a disk galaxy, driving radially expanding density waves into the disk. Although not without complications, the inherent symmetry of the collison makes these ``cosmic accidents'' remarkable laboratories for studing the processes that lead to massive star formation. Results from a major multi-wavelength study of a dozen ring galaxies will form the basis of this talk. The observations will be compared with recent hydrodynamic simulations of ring galaxies.
