Halo Wide Binaries and Moving Clusters as Probes of the Dynamical and Merger History of our Galaxy

Wide or fragile pairs are sensitive probes of the galactic potential, and they have been used to provide information about the galactic tidal field, the density of GMC and the amount of dark matter present in both the disk and the halo. Halo wide binaries and moving clusters, since they are likely to be the remains of past mergers or of dissolved clusters, can provide information on the dynamical and merger history of our Galaxy. Such remnants should continue to show similar motions over times of the order of their ages. We have looked for phase space groupings among the low metallicity stars of Beers et al. (2000) and of Schuster et al. (2004) and have identified a number of candidate moving clusters. In several of the moving clusters from the data of Schuster et al. we found a wide CPM binary already identified in the catalogue of wide binaries among high-velocity and metal-poor stars of Allen et al. (2000). Spectroscopic follow-up studies of these stars would confirm the physical reality of the group, as well as allow us to distinguish whether their progenitors are dissolved clusters or accreted systems. The proper motions of the Beers et al. stars are too small to appear in the CPM binary searches so far conducted, but the members of the moving groups we have identified are prime candidates for such searches.