THE EXCITATION AND KINEMATICS OF DR21(OH) FROM OBSERVATIONS OF CS

We have mapped the young star formation region DR21(OH) in the J = 2-1 and 1-0 transitions of CS and (CS)-S-34, and have obtained spectra with high signal-to-noise ratios towards the three main continuum sources within the core. We find that the CS emission corresponds closely with the thermal continuum, and that all three continuum sources are well separated in velocity as well as spatially. We suggest that wing emission in the CS lines is associated with an outflow originating from DR21(OH)Main, which also excites the observed CH3OH masers. Our CS line profiles show clear self-absorption redshifted by about 0.5 km s-1 relative to the rest velocity of the cloud. In order to account for this feature, we also suggest that there is residual contraction of the outer, less dense, parts of the cloud. By approximating this cloud structure as two components, namely a warm background component plus cooler, foreground absorbing gas, we use an LTE model to examine the excitation of the cloud core. We find good agreement between our excitation temperatures and the temperatures derived from dust emission. The advantages and limitations of the model are also discussed.