A Consistent Microlensing Model for the Galactic Bar

Abstract

We compute a microlensing map for the Galactic bar. The predicted event rate and event duration distribution are consistent with the $55$ events recently reported by the MACHO and OGLE collaborations. Most of the events are due to lensing by stars in the near end of the bar. Lens mass functions with about 30-60\% of lens mass as brown dwarfs are rejected at $2-6\sigma$ levels. To make our model useful for other workers, we tabulate the bar's optical depth and average event duration (scaled to $1M_\odot$ lenses) on a grid of Galactic coordinates. The distance and the proper motions of the lens and the source are derived from a consistent dynamical model of the stellar bar, which has originally been built to fit data on the stellar light and stellar/gas kinematics of the bar. We explore several alternative models and we find that our standard model best matches observations.