PI: Arlin Crotts, Columbia University, email@example.com
Address: 550 W.~120th St., New York, NY 10027, U.S.A.
CoI: Robert Uglesich, Columbia University
CoI: Geza Gyuk, University of California, San Diego
CoI: Andrew Gould, Ohio State University
CoI: Penny Sackett, Kapteyn Institute
CoI: Lawrence Widrow, Queens University
CoI: Konrad Kuijken, Kapteyn Institute
Title: The MEGA Survey: Mapping Microlensing in M31
Abstract: Microlensing surveys, while revealing a wealth of new knowledge, have missed their goal of determining what composes the Galactic dark matter halo, in part due to our location amidst the Galaxy and the paucity of useful sightlines through the Halo. We propose overcoming these difficulties and addressing questions unsettled by Galactic surveys, using MOSAIC and a technique we invented (difference image photometry of variables) to expand our microlensing survey of M31. Our technique in extracting light curves from extremely crowded environments has isolated many microlensing events found in our smaller M31 survey. With MOSAIC's large field and the high lensing optical depth predicted, our proposed survey should record ~ 75-150 events per season. The spatial distribution of these events will indicate the shape of the microlensing halo of M31, and separate self-lensing by M31 disk and bulge stars from those due to M31's halo. Masses of individual lenses should be constrained to within a factor of 2-3. Almost certainly, we would establish whether microlensing objects are significant to the halo mass in M31. Meanwhile, ~ 60000 new variable stars in M31 will be detected in the course of our survey. Miras and cepheids are good tracers of population age in a part of M31 where color-magnitude diagrams are problematic; along with new eclipsing variables these variables will provide good distance measures.
National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360