Dark Matter Constraints from the Sagittarius Dwarf and Tail System

2MASS has provided a three-dimensional map of the > 360◦, wrapped tidal tails of the Sagittarius (Sgr) dwarf spheroidal galaxy, as traced by M giant stars. With the inclusion of radial velocity data for stars along these tails, strong constraints exist for dynamical models of the Milky Way-Sgr interaction. N-body simulations of Sgr disruption with model parameters spanning a range of initial conditions (e.g., Sgr mass and orbit, Galactic rotation curve, halo flattening) are used to find parameterizations that match almost every extant observational constraint of the Sgr system. We discuss the implications of the Sgr data and models for the orbit, mass and M/L of the Sgr bound core as well as the strength, flattening, and lumpiness of the Milky Way potential. 1. Observational Constraints The relatively nearby Sagittarius (Sgr) dwarf galaxy offers the opportunity to explore in exquisite detail the interaction of a satellite with its parent galaxy. Moreover, the extensive Sgr tidal tail system gives sensitive leverage on the properties of the Galactic potential, much as polar ring galaxies have been exploited to determine the properties of extragalactic systems (e.g., Sparke 2002). Since Sgr’s discovery by Ibata, Gilmore & Irwin (1994), this archetype of a dwarf galaxy merger has remained difficult to study because its core (centered at [l, b] = [6,−14]◦), lies obscured by foreground dust and stars of the Galactic disk and bulge. However, the Two Micron All Sky Survey (2MASS) has opened a new