The chemical evolution of the halo of the M33 galaxy

The chemical evolution of the halo of the M33 (Triangle) galaxy is considered. We suppose a galactic stellar halo to be formed as separate fragments which then merge. Our results show that the M33 halo metallicity distribution function can be reproduced in the framework of such a merger scenario of the chemical evolution. The halo stellar population of M33 was likely formed from two fragments only. It was found that gas accretion plays a significant role during the evolution of fragments before their merger. The presence of gas accretion during the fragment evolution allows us to obtain a gas mass fraction which is sufficient for the disk formation after the merger of the fragments.