The Opportunities and Challenges of AO Astrometry of Stars at the Galactic Center

Sylvana Yelda (UCLA)

The recent advent of adaptive optics on 8-10 m class telescopes has
increased the number of stars and the astrometric precision for
measuring orbits of stars in the center of the Galaxy.  Stellar orbits
are powerful tools for studying the supermassive black hole, Sgr A*,
and its environs.  However, our knowledge of the orbital parameters is
currently limited by systematic errors.  These errors are associated
with geometric optical distortion, differential atmospheric
refraction, and reference frame construction.  I will discuss how we
have overcome these sources of systematic error and show the resulting
improvements in our knowledge of the central potential and the
dynamics of stars at larger radii.  Improved stellar orbits at large
radii will help 1) constrain star formation scenarios used to explain
the mysterious presence of young stars in the vicinity of a
supermassive black hole, and 2) explain the apparent lack of a stellar
cusp in the giant star population.