Chemical evolution of gas-rich galaxy mergers

We investigate numerically the chemodynamical evolution of major disc-disc galaxy mergers in order to explore the origin of the mass-dependent chemical, photometric and spectroscopic properties observed in elliptical galaxies. We investigate especially the dependence of the fundamental properties on merger progenitor disc mass (M-d). Three main results are obtained in this study: 1. More massive (luminous) ellipticals formed by galaxy mergers between more massive spirals have higher metallicity (Z) and thus show redder colours; the typical metallicity ranges from similar to 1.0 solar abundance (Z similar to 0.02) for ellipticals formed by mergers with M-d = 10(10) M. to similar to 2.0 solar (Z similar to 0.04) for those with M-d = 10(12) M.. 2. Both the Mg-2 line index in the central part of ellipticals (R less than or equal to 0.1 R-e) and the radial gradient of Mg-2 (Delta Mg-2 / Delta log R) are more likely to be larger for massive ellipticals. Delta Mg-2 / Delta log R correlates reasonably well with the central Mg-2 in ellipticals. For most of the present merger models, ellipticals show a positive radial gradient of the H-beta line index. 3. Both M/L-B and M/L-K (where M, L-B, and L-K are the total stellar mass of galaxy mergers, the B-band and the K-band luminosities, respectively) depend on galactic mass in such a way that more massive ellipticals have larger M/L-B and smaller M/L-K.