Light-weight Local Group Dwarf Spheroidal Galaxies

Abstract

A simple and natural explanation for the dynamics and morphology of the Local Group Dwarf Spheroidal galaxies, Draco (Dra) and Ursa Minor (UMi), is that they are weakly unbound stellar systems with no significant dark matter component. A gentle, but persistent, Milky Way (MW) tide has left them in their current kinematic and morphological state. This short paper reviews the parametric tidal interaction model which accounts for their behavior and discusses new statistical evidence from the observed stellar distribution in Dra which implies that its total mass is not dominated by collisionless dark matter (DM).

to appear in Publications of the Astronomical Society of the Pacific, proceedings of Satellites and Tidal Streams, La Palma, Spain, May 26-30, 2003