What are the dynamics like in and around the dwarf spheroidals - where is the dark matter - how far do the tidal tails extend? Kinematics and metallicities of Local Group stars:
One can measure the velocities and chemical compositions of thousands of stars in a galaxy, and like the project above to study the Milky Way halo, investigate the 5-space that the spectra provide. Cold dark matter simulations of the Local Group predicts the existence of a thousand dwarf galaxies - where are they? Could they be the halos of the remaining galaxies? Might the few remaining ~20 dwarf galaxies in the Local Group be those that had an overabundance of dark matter? If so, what is the distribution of that mass, in and around the dwarfs?
These questions can be addressed with R ~ 5000 spectra of a few 100 (dwarfs) to 1000 spectra per galaxy. Combined with astrometric results from planned space interferometers, the 3-space velocities for dwarf stars can be derived. If tails can be unambiguously identified, the orbits will be very well-determined.