Formation of giant globular cluster G1 and the origin of the M 31 stellar halo

¹ School of Physics, University of New South Wales, Sydney 2052, Australia
² Astronomical Institute, Tohoku University, Sendai, 980-8578, Japan e-mail: chiba@astr.tohoku.ac.jp

Corresponding author: K. Bekki, bekki@bat.phys.unsw.edu.au

Received: 20 September 2003
Accepted: 21 October 2003

Abstract

We demonstrate that globular cluster G1 could have been formed by tidal interaction between M 31 and a nucleated dwarf galaxy (dE,N). Our fully self-consistent numerical simulations show that during tidal interaction between M 31 and G1's progenitor dE,N with mag and its nucleus mass of ~10⁷ , the dark matter and the outer stellar envelope of the dE,N are nearly completely stripped whereas the nucleus can survive the tidal stripping because of its initially compact nature. The naked nucleus (i.e., G1) has orbital properties similar to those of its progenitor dE,N. The stripped stars form a metal-poor ([Fe/H] ~ -1) stellar halo around M 31 and its structure and kinematics depend strongly on the initial orbit of G1's progenitor dE,N. We suggest that the observed large projected distance of G1 from M 31 (~40 kpc) can give some strong constraints on the central density of the dark matter halo of dE,N. We discuss these results in the context of substructures of M 31's stellar halo recently revealed by Ferguson et al. ([CITE]).