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D. F. Figer (STScI/JHU), D. Gilmore (STScI), M. Morris, I. S. McLean, E. E. Becklin (UCLA), A. M. Gilbert, J. R. Graham (UCB), J. E. Larkin (UCLA), N. A. Levenson (JHU), H. I. Teplitz (GSFC)
We present newly-obtained radial velocities for over 100 stars projected onto the central parsec of the Galaxy, using the NIRSPEC instrument on the Keck II telescope. The majority of these data have velocity errors (~1 km s-1) which are a factor of about 30 smaller than those obtained so far with proper motion measurements. From our data, we establish a first epoch of radial velocity measurements which can be compared to subsequent epochs to measure reliable accelerations (1 km s-1 yr-1) over a timespan of several years, which corresponds to the magnitude expected for the most favorable cases. The ultimate intent is to combine these data with proper-motion measurements to map the dark matter distribution, i.e. stellar remnants or WIMPS, in the radial range between 1 to 5 arcseconds around the central black hole. The present data set is analyzed to constrain the dynamical history of old and young stellar populations in the central parsec. We find that the old stars have a gaussian velocity distribution with a median of -12 km s-1 (blueshift) and a standard deviation of 104 km s-1; we interpret the median velocity as the solar motion with respect to the Galactic Center, consistent with no Galactocentric radial motion of the Local Standard of Rest. The old stars exhibit no correlated motion with respect to field location.
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The author(s) of this abstract have provided an email address for comments about the abstract: figer@stsci.edu