NOAO >   Observing Info >   Approved Programs >   2002B-0269

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Proposal Information for 2002B-0269


PI: Arlin Crotts, Columbia University, arlin@astro.columbia.edu
Address: 550 W.~120th St., New York, NY 10027, U.S.A.

CoI: Alves, Cseresnjes, Uglesich, Columbia University
CoI: De Jong, Kuijken, Sackett, Kapteyn Institute
CoI: Geza Gyuk, University of California, San Diego
CoI: Andrew Gould, Ohio State University
CoI: Will Sutherland, Oxford University
CoI: Lawrence Widrow, Queens University

Title: The MEGA Survey: Mapping Microlensing in M31

Abstract: Microlensing surveys, while uncovering a wealth of new knowledge, have fallen short of their goal of determining what composes the Galactic dark matter halo, in part due to our location amidst the Galaxy and the few 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 method of extracting light curves from highly crowded environments has isolated many microlensing events in our smaller M31 field. 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 M31's microlensing halo and separate self-lensing by M31 disk and bulge stars from those due to M31's halo. Individual lens masses can be measured to within a factor of 2-3. Almost certainly, we can learn if microlensing objects are significant to the halo mass in M31. Meanwhile, ~ 60000 new variable stars will be detected during 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 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



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