High-Frequency-Resolution Studies of Hi, OH, and CH20 Absorption Spectra in Sagittarius A

Absorption profiles towards Sgr A have been observed in the 1420-1667-, and 4830-MHz lines of H I, OH, and CH2O, with velocity resolutions of 1.67, 1.42, and 0.49 km/sec, respectively. The 0-, -50-, and +45-km/sec H I absorption features and the +40- and - 130-km/sec OH absorption features were also observed with higher velocity resolutions ranging from 0.42 to 0.10 km/sec. The +40-km/sec absorption features are very broad and smooth with only slight structure, supporting the picture of rotation of the cloud of origin as a uniform body. This compact cloud, near the Galactic center, has a high relative abund- ance of molecules such as OH, CH2O, and NH8, and also contains H I but no detectable 1120. The NH3 emission is concentrated towards one side of the cloud. The H I profile contains a local feature at +5.8 km/sec, and a flat shoulder from +3.5 to -6.5 km/sec coming from the Sagittarius and Norma-Scutum spiral arms, which also have a higher relative abundance of molecules than the local arm. The - 130-km/sec absorption feature seen in OH is not detectable in CH1O, an effect due to the smaller beam used in the CH2O observations. Distinct asymmetry is present in the absorption feature due to the 3-kpc arm.