Formation and Assembly History of Stellar Components in Galaxies as a Function of Stellar and Halo Mass

Galaxy mass assembly is an end product of structure formation in the ACDM cosmology. As an extension of Lee & Yi, we investigate the assembly history of stellar components in galaxies as a function of halo environments and stellar mass using semi-analytic approaches. In our fiducial model, halo mass intrinsically determines the formation and assembly of the stellar mass. Overall, the ex situ fraction slowly increases in central galaxies with increasing halo mass but sharply increases for logM(*)/M-circle dot greater than or similar to 11. A similar trend is also found in satellite galaxies, which implies that mergers are essential to build stellar masses above logM(*)/M-circle dot similar to 11. We also examine the time evolution of the contribution of mass growth channels. Mergers become the primary channel in the mass growth of central galaxies when their host halo mass begins to exceed logM(200)/M-circle dot similar to 13. However, satellite galaxies seldom reach the merger-dominant phase despite their reduced star-formation activities due to environmental effects.