DUST EMISSION ASSOCIATED WITH DR21(OH)

We have mapped a section of the star-forming molecular cloud near DR21(OH) at high resolution in 1.3-mm thermal dust continuum. We see emission arising from a north-south ridge several parsecs in length, and we have identified eight distinct, compact sources located within the ridge. We find extensive diffuse emission associated with the ridge that comprises most of the mass in the cloud. Comparing our dust map with existing molecular data, it appears that even (CO)-O-18 becomes optically thick towards the dense cores, resulting in estimates of the hydrogen column density based on the (CO)-O-18 data that are low by up to a factor of 10. Where the (CO)-O-18 emission is reliably optically thin, the derived column density is in agreement with that we derive from the dust, using standard abundances for both. All the cores we detect at 1.3 mm require the presence of embedded young stars to account for the observed flux. The total mass of the area mapped is 3 x 10(4) M. (d/3 kpc)2.