Friday, January 30, 2009
Star Formation Around the Supermassive Black Hole at the Center of our Galaxy
Department of Astronomy, California Institute of Technology
The case for a supermassive black hole at the center of our Milky Way galaxy has been made by monitoring the motions of stars orbiting the unseen dark mass with high resolution images. Many of these orbiting stars are young (6 Myr) and their existence is puzzling given that the strong tidal forces from the black hole make typical modes of star formation unlikely. Proposed alternatives include models where the stars formed far from the black hole and migrated to their current location and models where the stars formed in situ, where they are observed today, in a massive gas disk around the black hole similar to those around active galactic nuclei (AGN) in other galaxies. Using over 10 years of high resolution images obtained at the Keck telescope, we measure the dynamics of these young stars to explore their origins. Our results show that nearly 50% of the young stars appear to reside in a disk with a steep (1/r^2) drop in the number of young stars away from the black hole. This result favors in situ formation models. However, the stars in the disk have high eccentricities and half the young stars reside off the disk, which may indicate that the stars formed in a geometry more complex than a simple disk.
Refreshments at 4:00 PM. Seminar begins at 4:10 PM.
Building 8, Room 241
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