Formation of ω Centauri by Tidal Stripping of a Dwarf Galaxy

Abstract

We have investigated whether or not a tidal stripping scenario can reproduce the observed surface brightness profile of ω Centauri using N-body simulations. Assuming that the progenitor of ω Cen is a dwarf elliptical galaxy, we model it with a King model with a core radius the same as that of ω Cen. A dark matter halo of the dwarf is not taken into account. We consider two different models of the Milky Way potential: a singular isothermal sphere and a three-component model. The progenitor dwarf is expressed as an N-body system, which orbits in the fixed Galactic potential. The dwarf lost more than 90% of its mass during the first few pericenter passages. Thereafter, the mass remains practically constant. The final surface density profile is in good agreement with the observational data on ω Cen, if the pericenter distance of the orbit of the progenitor dwarf is around 500 pc. This value is within the error bar of the current proper-motion data on ω Cen and Galactic parameters. Although our simulation is limited to a King-like progenitor dwarf without a dark matter halo, it strongly suggests that the current density profile of ω Cen is nicely reproduced by a tidal stripping scenario, in other words, that ω Cen can plausibly be identified with a stripped dwarf elliptical galaxy.