Distribution of the disrupted satellite galaxies as a function of metallicity

¹ National Astronomical Observatory, Chinese Academy of Sciences, Beijing 100012, PR China
² Department of Physics, Hong Kong University, Hong Kong, PR China

Corresponding author: Y. Lu, ly@yac.bao.ac.cn

Received: 17 October 2001
Accepted: 9 April 2002

Abstract

Recent observations show that some dwarf satellite galaxies fall into the gravitational well of the Galaxy while being disrupted by the tidal force. As a consequence, the Galactic halo suffers contamination from this process, the stellar populations of the tidal disrupted satellites make an additional contribution and alter the intrinsic metallicity distribution of the halo stars. The distribution of this kind of disrupted satellite galaxy as a function of metallicity is investigated in this paper. The model is limited to one class of dwarf spherical satellite galaxy, that is assumed to have similar abundance patterns to the Galactic field halo stars. We discuss their distributions through the links between minor merger processes in the history of the Galaxy and the observed distribution of metal-poor field halo stars. The upper limit of 35% of the metal-poor halo field stars was established by merging of this kind of satellite galaxy with characteristic mass M_sat, and adopting the mass-metallicity relation among dwarf spheroidal galaxy, the distribution of the disrupted satellite galaxy as a function of metallicity is derived to reproduce the observed metallicity distribution of the extremely metal-poor halo field stars in the Galaxy. The problem of missing metal-free halo stars in the Galaxy is explained in this model as well.