Simple dynamical models of the Sagittarius dwarf galaxy

We present two simple dynamical models for Sagittarius based on N-body simu lations of the progressive disruption of a satellite galaxy orbiting for 12 .5 Gyr within a realistic Galactic potential. In both models the satellite initially has observable properties similar to those of current outlying dw arfs; in one case it is purely stellar while in the other it is embedded in an extended massive halo. The purely stellar progenitor is a King model wi th a total velocity dispersion of 18.9 km s(-1), a core radius of 0.44 kpc and a tidal radius of 3 kpc. The initial stellar distribution in the other case follows a King profile with the same core radius, a slightly larger to tal velocity dispersion and similar extent. Both these models are consisten t with all published data on the current Sagittarius system, they match not only the observed properties of the main body of Sagittarius, but also tho se reported for unbound debris at larger distances.