Numerical simulations of ring galaxies: First ring events, star formation, and AM0644-741

We examine first ring events in collisional galaxy simulations in order to model physical systems such as AM0644-741 and to draw broader conclusions about the nature of first ring formation events. Rings in collisional remnant galaxies such as AM0644-741 are the result of the gas response of a disk galaxy to the near-center collision of a smaller neighboring galaxy. We discuss resolution biases in typical density-based star formation laws, offer an experimental star formation recipe of rndra dt , and also investigate the relatively low significance of heating, cooling and feedback mechanisms in determining the gross morphology and kinematics of collisional systems. Utilizing a very large search of the pericenter passage impact parameter phase space, we set constraints on the likely mass of the primary galaxy as well as providing insight into the time scales involved for ring formation and ring lifetime. We then focus on one simulation in depth to produce both a morphological and kinematic match to ring galaxy AM0644-741. A general approach to simulating observed systems is then presented.