Microlensing of globular clusters as a probe of galactic structure

The spatial distribution of compact dark matter in the Galaxy can be determined in a few years by monitoring Galactic globular clusters for microlensing. Globular clusters are the only dense fields of stars distributed throughout the three-dimensional halo, and hence, they are uniquely suited to probe its structure. The microlensing optical depths toward different clusters have varying contributions from the thin disk, thick disk, bulge, and halo of the Galaxy. Although measuring individual optical depths to all the clusters is a daunting task, we show that interesting Galactic structure information can be extracted with as few as 40-120 events in total for the entire globular cluster system (observable with 2-5 yr of monitoring). This experiment is particularly sensitive to the core radius of the halo mass distribution and to the parameters of the thin disk.