The Case for a Next Generation LMC Microlensing Survey

Abstract

Microlensing surveys search for the transient brightening of a background star that is the signature of gravitational lensing by a foreground compact object. This technique is an elegant way to search for astrophysical candidates that might comprise the dark matter halo of the Milky Way. While the current projects have successfully detected the phenomenon of microlensing and have reported many important results, the relatively large event rate reported towards the LMC remains a puzzle. The first step in resolving this mystery is determining the location of the excess lensing population. This will require a microlensing survey with an order of magnitude increase in sensitivity over current projects. I summarize the present status of microlensing surveys, and present (and advocate!) a next-generation project that should be capable of unambiguously determining whether the dark halo of the Galaxy is indeed made up of MACHOs, or whether the observed events are due to previously unappreciated ordinary stellar populations.