Properties of the Outer Halos of Galaxies from the Study of Globular Clusters

This paper reviews some recent work on the properties of the outer halos of galaxies. I particularly focus on recent and upcoming advances made with the study of globular clusters. Globular clusters can be observed out to ~100 kpc from the centers of galaxies, allowing the study of galactic halos well beyond the regions probed by many other techniques such as observations of the integrated light of galaxies. In the few well-studied cases to date, the study of globular cluster systems has provided dynamical evidence for dark matter halos around elliptical galaxies, and demonstrated kinematic differences between different globular cluster populations that shed light on the formation history of their host galaxies.