FORMATION OF OB CLUSTERS - DETECTION OF SIO V = 0, J = 1-0 EMISSION AS AN INDICATOR OF COMPACT OUTFLOW SOURCES

During a survey for Silicon Monoxide (υ = 0, J = 1-0) emission from compact and ultra-compact H II regions, detections were made toward 12 Galactic H II regions. A comparison is drawn with the υ = 0, J = 2 → 1 SiO observations of the same regions. We conclude that most of the detected SiO emission probably originates from compact, hot, optically thick sources. From the observed large line widths, we further suggest that the SiO sources are probably associated with outflowing material from embedded young stars. υ = 0, J = 1 → 0 silicon monoxide absorption was also detected from the H II region Sgr B2. This absorption feature has a similar line width to that observed in other low-optical depth molecules toward this source such as NH3 and H2CO. A map of Sgr B2 was made on a 40″ grid and indicates broad underlying emission, peaked on the position of the absorption line with more extended narrower velocity features. In this case, the SiO emission may be sampling cooler extensive material.