Gaia will play an important role in providing information about star
formation histories, merging events, intergalactic streams etc., for nearby
galaxies of the Local Group. One of the most crucial contributions will be
proper motions, especially for stars in the outermost parts of the galaxies,
obtainable for stellar populations to ~150 kpc with RGB stars. Together with
radial velocities for the brightest giants <80 kpc, this will provide
membership information for individual stars and global kinematical picture of
the most nearby galaxies, including the Magellanic Clouds (MCs). Gaia will also
provide photometric metallicities (\sigma([M/H])<0.3) for individual giants
and/or supergiants in dwarf galaxies to ~200 kpc. MSTO ages will be possible
for the youngest stellar populations in the most nearby galaxies (e.g., MCs),
whereas stars on RGB/AGB may provide age estimates for populations to ~150 kpc.
Gaia will allow to study the outermost parts of the galaxies, which (because of
their large spatial extent) are difficult to assess from the ground. Apart from
allowing to clarify the structure and evolution of the dwarf galaxies, this
will also make it possible to investigate galactic tidal debris, thus providing
additional details for the global picture of formation and evolution of the
Milky Way Galaxy.Comment: Proceedings of "The Three Dimensional Universe With Gaia", Paris,
October 4-7, 2004, 4 pages, 3 figure