NOAO >   Observing Info >   Approved Programs >   2004B-0321

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Proposal Information for 2004B-0321


PI: Arlin Crotts, Columbia University, arlin@astro.columbia.edu
Address: Department of Astronomy, 550 W.~120th St., New York, NY

CoI: \small Cseresnjes, Uglesich, Bergier, Columbia University (& Mt. Sinai SM)
CoI: De Jong, Kuijken, Kapteyn Institute/Leiden
CoI: Edward Baltz, Stanford University
CoI: Geza Gyuk, Adler Planetarium/University of Chicago
CoI: Will Sutherland, VISTA Project, Royal Observatory Edinburgh
CoI: Lawrence Widrow, Queens University

Title: Microlensing in M31 at Large Distances and for Large Masses

Abstract: We have recently found many microlensing events in M31 on ~ 10^6s timescales, corresponding to ~ 1 M_\odot or less. A large number of events of this nature are also being found by the wider angular area survey we have completed (with significant KPNO 4m/MOSAIC data), and have largely analyzed. The initial evidence lends strong support to the idea that a large fraction of galaxy dark matter halos consist of stellar-mass objects. Continuing with the 4m/MOSAIC, however, we can easily extend these results to longer timescales, probing wholely new and interesting regimes in microlensing events: 1) black holes from very massive objects (~ 30 - 300 M_\odot) which might be expected to have formed very early and collected in nascent galaxy halos, and 2) stellar mass objects at large galactocentric distances from both M31 and the Galaxy, which might form a diffuse dark matter halo in the Local Group. This approach makes efficient use of a relatively small amount of continuing 4m/MOSAIC time (following our 33 epochs from 1997-2004), buttressed by our previous data, to produce a unique and otherwise difficult result for interesting classes of microlensing objects, as well as yielding a valuable baseline for extended stellar variability studies. The extended baseline will further enhance our studies on smaller timescales by making those events more robust against baseline variations, and revealing and detailing more slowly changing variable stars.


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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