Property of young massive clusters in a galaxy–galaxy merger remnant

摘要

We investigate the properties of young massive clusters (YMCs) in a galaxy–galaxy merger remnant by analyzing the data obtained by a gas-rich major merger simulation in Matsui et?al. (2012, ApJ, 746, 26). We found that the YMCs are distributed at a few kpc and at ～10?kpc from the galactic center; in other words, there are two components of their distribution. The former are formed in filamentary and turbulent gas generated at a few kpc from the center as a result of galaxy encounters, and the latter are formed in tidal tails which are far from the center. The YMCs are much less concentrated than galaxy stars. The mass function of the YMCs is dN/dM∝M?2. Most YMCs are formed between the second encounter and the final coalescence phase of the galactic cores, and their formation rate is especially high at the final coalescence phase. Most of them consist of single stellar population in age, but YMCs with multi-stellar populations in age are also formed. The multiple populations are produced by the following process: a YMC captures dense gas, and another generation of stars form within the cluster. There are several YMCs formed in an isolated disk before the encounter of galaxies. These candidates contain stars with various ages by capturing dense gas and forming stars. YMCs in a merger remnant have various orbits, but a large fraction of candidates have circular orbits.