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Session 97 - Galactic Structure, Galactic Center.
Oral session, Friday, January 09

[97.04] Proper Motion of Ionized Gas at the Galactic Center

F. Yusef-Zadeh (Northwestern U.), D. A. Roberts (U. Illinois), J. Biretta (STScI)

We present radio continuum observations of the spiral-shaped ionized feature (Sgr A West) within the inner pc of the Galactic center at three epochs spanning 1986 to 1995. The VLA A-configuration was used at \lambda2cm (resolution of 0.1''\times0.2''). We detect proper motions of a number of features in the Northern and Eastern Arms of Sgr A West including the ionized gas associated with IRS 13 with V(RA)= 113\pm10, V(Dec)=150\pm15 km s^-1 and IRS 10 V(RA)= 122\pm11, V(Dec)=24\pm34 km s^-1. The proper motion measurements when combined with H92\alpha radio recombination line data (Roberts and Goss 1993, ApJS, 86, 133) show an unambiguous direction of the ionized flow supporting the infall picture of the Northern and Eastern arms toward the Galactic center. In addition, a number of high-velocity ionized features appear to be on an unbound orbit assuming a 2.45 million solar mass of dark matter resides at the Galactic center. This implies a picture in which the gas features are externally driven into the Galactic center.

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