(Ralf Klessen & Pavel Kroupa)
We discuss self-consistent simulations of the dynamical evolution of a low-mass satellite galaxy without dark matter orbiting around the Milky Way. For the simulations, a particle-mesh code with nested sub-grids and a direct-summation N-body code running with the special purpose hardware device GRAPE are used. The calculations proceed for many orbital periods until well after the satellite dissolves by tidal torques.
In all cases the dynamical evolution converges to a remnant that contains a few per cent of the initial satellite mass. The stable remnant results from severe tidal shaping of the initial satellite. To an observer from Earth these remnants look strikingly similar to the Galactic dwarf spheroidal satellite galaxies. Their apparent mass-to-light ratios are very large despite the fact that they contain no dark matter.
The effect is larger for satellites on elongated orbits. This is a result of projection onto the observational plane. Assuming they are not dark matter dominated our model predicts that the Galactic dSph satellites should have rather large orbital eccentricities (e > 0.5) and a large spatial extent along the line-of-sight. Some remnants in or model have sub-structure that may be apparent in the morphology of the horizontal branch.