Microlensing of Globular Clusters as a Probe of Galactic Structure

The spatial distribution of compact dark matter in our Galaxy can bedetermined in a few years of monitoring Galactic globular clusters formicrolensing. Globular clusters are the only dense fields of stars distributedthroughout the three-dimensional halo and hence are uniquely suited to probeits structure. The microlensing optical depths towards different clusters havevarying contributions from the thin disk, thick disk, bulge, and halo of theGalaxy. Although measuring individual optical depths to all the clusters is adaunting task, we show that interesting Galactic structure information can beextracted with as few as $40$--$120$ events in total for the entire globularcluster system (observable with 2--5 years of monitoring). The globular clustermicrolensing is particularly sensitive to the core radius of the halo massdistribution and to the scale length, surface mass density, and radial scaleheight variations of the thin disk.Comment: 14 pages, 1 figure. Submitted to ApJ Letters. Uses aastex macro