Determination of the 3-Dimensional Motions of Ionized Gas in the Galactic Center

Doug Roberts1,2, Farhad Yusef-Zadeh2

1 Adler Planetarium & Astronomy Museum
2 Northwestern University

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A number of measurements have successfully detected proper motion of ionized gas and stars near Sgr A*. We compare the radial velocities of ionized gas in the inner parsec of the Galaxy in three epochs separated over a nine year period (February 1993, October 1999 and May 2002). VLA observations were carried out in the H92-alpha radio recombination line from Sgr A West; each observation had identical velocity coverage (-420 to +20 km s-1) as well as velocity (14 km s-1) and spatial (1.0" x 1.25" (alpha x delta) resolutions. Accurate velocity fields were derived from Gaussian fitting the data from each epoch; radial acceleration was determined by comparing the fitted velocity fields. The radial acceleration results are combined with the radial velocity field as well as proper motion velocities to derive the most stringent limits yet determined on the gas motions near Sgr A* as well as the relative geometry of ionized features with respect to Sgr A*.