The Galactic Center: Star Formation Near a Supermassive Black Hole?
Jessica Lu (UCLA) - Oct 23 at 12:00 noon
We present new proper motions for the massive, young stars at the Galactic Center, based on 10 years of
diffraction limited data from the Keck telescopes. Our proper motion measurements now have uncertainties
of only 1-2 km/s and allow us to explore the origin of the young stars that reside within the sphere of
influence of the supermassive black hole whose strong tidal forces make this region inhospitable for
star formation. Their presence, however, may be explained either by in situ star formation in an
accretion disk or as the remnants of a massive stellar cluster which spiraled in via dynamical friction.
Earlier stellar velocity vectors were used to postulate that all the young stars resided in two
counter-rotating stellar disks, which is consistent with both of the above formation scenarios. Our
precise proper motions allow us, for the first time, to determine the orbital parameters of each
individual star and thereby to test the hypothesis that the massive stars reside in two stellar disks.
Of the 26 young stars in this study that were previously proposed to lie on the inner, clockwise disk,
we find that nearly all exhibit orbital constraints consistent with such a disk. On the other hand, of
the 7 stars in this study previously proposed to lie in the outer, less well-defined counter-clockwise
disk, 6 exhibit inclinations that are inconsistent with such a disk, bringing into question the
existence of the outer disk. Furthermore, for stars in the inner disk that have eccentricity
constraints, we find several that have lower limits to the eccentricity of more than 0.4, implying
highly eccentric orbits. This stands in contrast to simple accretion disk formation scenarios which
typically predict predominantly circular orbits.
The seminar will be held in 544 Campbell Hall.
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