RADIO-CONTINUUM AND RADIO RECOMBINATION LINE OBSERVATIONS OF SAGITTARIUS-B1 AND G0.6-0.0

The Very Large Array (VLA) was used to make high-resolution 3.6, 6, and 20 cm continuum and H110alpha recombination line observations of the Sgr B region. Although Sgr B2 has been the subject of numerous VLA investigations, this study is the first VLA investigation of Sgr B1 (GO.5-0.0) and GO.6-0.0. A major goal of this study was to image the ionized gas in Sgr B1 at high resolution. Unlike Sgr B2, which is dominated by numerous compact components, the emission from Sgr B1 arises from a wealth of extended bright rim and shell-like structures. One of these features is a bar of ionized gas approximately 6 pc in length. No other feature of this type and size has been previously discovered in the star-forming region. The presence of these large structures might be the result of individual compact H II regions having expanded and coalesced over time. Thus, Sgr B1 may be an evolved star-forming region. Another purpose of this study was to investigate the kinematics of the ionized gas in Sgr B1. The recombination line data indicate that there are two regions in Sgr BI that differ substantially in their kinematics. A single line with a width of approximately 30 km s-1 is observed on the western side of the region, while multiple velocity components are observed on the eastern side. The ionized gas in Sgr B1 has velocities predominantly in the range of 30 50 km s-1, although emission on the eastern side can be seen over a velocity range of 120 km s-1 Since the velocity of the ionized gas in Sgr B2 is near 65 km s-1, the proximity of Sgr Bl and Sgr B2 seems to be more than a chance superposition. The region GO.6-0.0 lies between the two major components of Sgr B and contains at least four compact sources. Its velocity is intermediate between Sgr BI and Sgr B2. In addition, an arc of emission to the east and south of these compact components seems to bridge Sgr B1 and Sgr B2, thus strengthening the argument that these regions are physically related.