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2017 Spring Science Colloquia

Finding Black Holes with Astrometric Microlensing

Presented by: Jessica Lu  (University of California Berkeley)
Category: Science Colloquia   Duration: 1 hour   Broadcast date: February 22, 2017
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Our Galaxy most likely hosts 10^8-10^9 million stellar mass black holes. The exact number and mass function of these black holes contains important information regarding our Galaxy's star formation history, stellar mass function, and the fate of very massive stars. However, isolated stellar black holes have yet to be detected. To date, stellar mass black holes have only been definitively detected in binary systems with accreting companions or merging to produce gravitational waves. In principle, the presence of isolated black holes can be inferred from astrometric and photometric signatures produced when they lens light from a background star. We attempt to detect the astrometric lensing signatures of several photometrically identified microlensing events, toward the Galactic Bulge. Long-duration events (t_Einstein > 100 days) were selected as the most likely black hole candidates and were observed using several years of laser-guided adaptive optics observations from the W. M. Keck telescopes. I will present results from this search. I will also present prospects for future precision-astrometry experiments with ground-based adaptive optics systems and space missions such as HST, JWST, and WFIRST.