Simulations of close encounter between galaxies: behaviour of interstellar gas clouds and enhancement of star formation rate

Numerical simulations are performed of close encounters between a parent galaxy with a disc system and a perturbing galaxy. Cloud particles are used in constructing the disc of the parent galaxy, in order to investigate the behaviour of the interstellar gas clouds and the influence of the encounter on the star formation rate. Star formation is assumed to take place when a pair of cloud particles collide. In the most violent encounter investigated, the prominent bridge and tail are formed by the passage of the perturbing galaxy. As these structures develop, the star formation rate begins to rise because the cloud-cloud collisions become more frequent. (author)