Formation of Young Massive Clusters with Multiple Stellar Populations in Galaxy-Galaxy Merging Process

We have analized simulation data of a galaxy-galaxy merger (Matsui et al. 2012) and researched stellar age in young massive clusters (YMCs). We find that whereas most YMCs have single stellar population, the rest YMCs have multiple stellar populations. Such YMCs with multiple stellar populations are formed by capturing dense gas and forming next generation stars when they pass dense gas region. Since the captured gas is contaminated with metal ejected from TypeII supernovae, the YMC consists of stars with different metallicity.