Collisions of galaxies are often invoked to explain vio lent phenomena in the universe. The dynamics of in teracting galaxies is intrinsically three-dimensional and involves both gas and stellar dynamics. In general, a computational approach is needed to model galactic collisions. Galaxy encounters are studied using a hy brid N-body/hydrodynamics code, capable of integrat ing systems of stars, gas, and dark matter in a fully self-consistent manner. These experiments demon strate that gravitational coupling between gas and stars in galactic interactions can drive most of the gas throughout a galaxy into the nucleus of a merger rem nant. The high densities in these gas concentrations are likely to result in strong bursts of star formation. Hence, this process may explain the nuclear starbursts in some systems of interacting galaxies. Further col lapse of these gas concentrations can trigger even more intense activity if some gas is eventually ac creted by a supermassive black hole. Such an evolu tionary sequence may account for some quasars and active galactic nuclei.
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