Galaxy interactions and mergers lead to bursts of star formation, but also play a major role in forming new stellar structures: rings, tails, shells, and more importantly massive star clusters that could be the progenitors of globular clusters and, maybe in some cases, of tidal dwarf galaxies and/or ultracompact dwarf galaxies. Examples of formation of massive/compact star clusters in the tidal tails of major mergers are shown on Fig. 11. A detailed review of structure formation and star cluster formation/evolution in galaxy interactions and mergers can be found in Bournaud (2010a).
Figure 11. Simulations (left, Wetzstein et al. 2007) and observations (right) of massive star cluster formation in a "beads-on-a-string" mode, typical for Jeans instabilities in tidal tails.