MULTICONFIGURATION VLA H92-ALPHA OBSERVATIONS OF SAGITTARIUS A WEST AT 1-ARCESECOND RESOLUTION

Sagittarius A (Sgr A) West has been observed in the H 92alpha line at 8.3 GHz using the Very Large Array with an angular resolution of approximately 1'', a velocity resolution of 14 km s-1, and an rms noise of approximately 0.15 mJy beam-1. The global kinematics and electron temperatures of the H II region have been determined. This determination of the kinematics has been done with almost an order of magnitude greater resolution and sensitivity than previous radio recombination line observations. These observations have a factor of 2 greater angular and velocity resolution than recent [Ne II] imaging spectral line observations; this kinematic determination does not support the one-armed spiral model suggested by the [Ne II] observations. Rather, three major kinematic features are identified: the western arc; the northern arm; and the extended bar. The western arc is modeled as part of a ring with an inner radius of 25''(1 pc) and is in circular rotation about a point near Sgr A *. The modeled ring with a position angle of 22-degrees and inclination of 56-degrees has a rotational velocity of 105 km s-1, and the interior mass appears to be approximately 3.5 x 10(6) M.. The previously reported high electron temperatures south of Sgr A * have been explained as a superposition of the bar (at nu(LSR) = 0 km s-1) and the northern arm (at nu(LSR) = -250 km s-1), and a uniform electron temperature of approximately 7000 K is observed throughout Sgr A West. Additionally, observation of stimulated emission at the position of the nonthermal point source Sgr A * has been interpreted as evidence of an infalling cloud from the circumnuclear disk. The He 92alpha line has been possibly detected at the 2.5 sigma level, with a Y+(He+/H+) of approximately 5%. Finally, the data were used to derive a 3 sigma upper limit to the line-of-sight magnetic field strength in the northern arm of Sgr A West of approximately 8 mG.