Starbursts in multiple galaxy mergers

We numerically investigate stellar and gaseous dynamical evolution of merge rs among five identical late-type disk galaxies with the special emphasis o n star formation history and chemical evolution of multiple galaxy mergers. We found that multiple encounter and merging can trigger repetitive massiv e starbursts (typically similar to 100 M-. yr(-1)) owing to the strong tida l disturbance and the resultant gaseous dissipation during merging. The mag nitude of the starburst is found to depend on initial virial ratio (i.e., t he ratio of total kinematical energy to total potential energy) such that t he maximum star formation rate is larger for the merger with smaller virial ratio. Furthermore, we found that the time interval between the epochs of the triggered starbursts is longer for the merger with the larger virial ra tio. The remnant of a multiple galaxy merger with massive starbursts is fou nd to have a metal-poor gaseous halo that is formed by tidal stripping duri ng the merging. We accordingly suggest that a metal-poor gaseous halo in a field elliptical galaxy is a fossil record of the past multiple merging eve nts for the galaxy.