IAU Symposium Abstract S186-007T

The nature and fate of the Sagittarius dwarf galaxy

Rodrigo Ibata1
1 University of British Columbia, Vancouver, Canada < ibata@astro.ubc.ca >

The Sagittarius dwarf galaxy, located at a distance of $\sim 15$ kpc behind the Galactic bulge, is in the process of being tidally disrupted and assimilated into the Milky Way. This unique event allows us to probe the physics of galactic merging with unprecedented detail, and may shed light on the hypothesized population of primordial galaxies that merged to form the Milky Way. Numerical simulations are presented, constrained by the lastest kinematic and structural data, which show that the luminous component of this dwarf galaxy must reside within a substantial dark matter halo for the dwarf to have survived the Galactic tides long enough to be seen at the present time. The minimum mass of the dark halo is then ~ 5 x 108 Msun, which implies a global mass to light ratio of ~ 100. It is found that the eventual fate of all the plausible models is to disrupt into a stream of particles that follows closely the original orbit of the dwarf through the Galactic halo, remaining stable for many Gyr. However, the timescale for the complete disruption of the Sagittarius dwarf is model-dependent and remains presently unknown.