Wide field imaging from space: Galaxy formation from nearby stellar populations

In the Galaxy and Local Group, proper motion studies could settle the contribution of cool white dwarfs to the halo dark matter mass and define the dynamics of the Galactic bulge. The white dwarf cooling age method could be applied to a larger number of globular clusters and could include measurements covering the whole of a given cluster. This powerful method can constrain the age of the Universe as well as the early star formation history of globular clusters. A wide field imager could derive main sequence turnoff ages for the interaction streams and multiple globular clusters in the M31 halo, as well as in other Local Group galaxies. Imaging in the halos of nearby galaxies to 10 Mpc, including the Virgo cluster, could map out tidal streams and debris tail and would help to define the stellar populations (and therefore the assembly history and nature of) Galactic halos.