IAU Symposium Abstract S186-064P

Stellar Population of Dissipative Merger

Y. Shioya1, K.Bekki2
1 Center for Interdisciplinary Research, Tohoku Univ. <shioya@astr.tohoku.ac.jp>
2 Astronomical Institute, Tohoku Univ. <bekki@astr.tohoku.ac.jp>

For the formation of elliptical galaxies, two dominant and competing scenarios are proposed. One is the protogalactic gravitational collapse and the other is merger of disk galaxies (merger hypothesis). As already known, it is difficult to reproduce the color - luminosity relation and the metallicity gradient observed for elliptical galaxies in the framework of stellar disk mergers. However, in general, disk galaxies include gaseous component and it is considered that the gas mass fractions of disk galaxies in the early universe is larger than those in our neighborhood. Thus, we numerically investigate chemical and dynamical evolution of gas-rich galaxy mergers in a self-consistent manner. We especially investigate the dependence of the nature of stellar population of merger remnants on the rapidity of gas consumption by star formation during merging. We found that galaxy mergers with more (less) rapid gas consumption by star formation show a larger (smaller) degree of metal enrichment and a shallower (steeper) metallicity gradient. We discuss tha validity of merger hypothesis based on our results.