GEPI

The Andromeda galaxy, M31, appears to be a typical spiral galaxy in the local universe. Its haunted halo is likely associated with a rich merger history, which is currently assumed to be caused by multiple minor mergers. Under the disk-rebuilding frame of spiral galaxy formation, we investigate the possibility that M31 could be formed from a major merger. With the help of N-body/hydrodynamical simulation, we think that we have succeeded in testing such a hypotheses of major merger origin of M31 by reproducing several of the crucial morphology parameters and stellar relics, such as bulge fraction, disk scale length in both stars and gas, as well as the Giant Stream and its kinematics. As the impact of the merger event, interestingly, we find that Milky Way possibly captured some material, for instance the Magellanic clouds, which is ejected from the merger event of M31. I will present the works in details and explain their formation from the point view of galactic dynamics.