Dynamics of Ionized Gas at the Galactic Center: Very Large Array Observations of the Three-Dimensional Velocity Field and Location of the Ionized Streams in Sagittarius A West

We present new results based on high-resolution observations of Sgr A West at the Galactic center with the Very Large Array (VLA) at 1.3 cm. By combining recent observations with those made at earlier epochs with the VLA at wavelengths of 1.3 and 3.6 cm, we measured proper motions for 71 compact HII components in the central 80 (3 pc, assuming D = 8 pc). Using VLA archival data for the H92α radio recombination line, we also investigated radial velocities in the LSR velocity range from +200 to –415 km s. Combining proper motion and radial velocity measurements, we have determined the three-dimensional velocity distribution in Sgr A West. We find that the three ionized streams (Northern Arm, Eastern Arm, and Western Arc) in the central 3 pc can be modeled with three bundles of Keplerian orbits around Sgr A*. Assuming that each