A spectroscopic study of the DR 21 outflow source. III. The CO line emission

New, high-angular resolution observations of ¹²CO, ¹³CO, C¹⁸O J= 1-0 and H₅₃ α hydrogen recombination line emission from the energetic DR 21 outflow are presented and discussed. The high-velocity CO emission is clearly bipolar with the blueshifted outflow lobe lying to the west and the redshifted lobe to the east of the DR 21 cloud core. These observations suggest that the DR 21 outflow is probably the most massive (> 3000 M_⊙) and energetic (> 2 × 10⁴⁸ ergs) young-stellar outflow yet discovered in the Galaxy. This extraordinarily energetic outflow is not only capable of supporting the DR 21 cloud against collapse but may even lead to the eventual destruction of the cloud core. In addition to the main outflow, the CO maps reveal a second high-velocity bipolar flow which also originates from within the DR 21 cloud core but extends along a N-S axis, perpendicular to the E-W axis of the main outflow. We therefore suggest that the massive DR 21 star-forming region may harbor more than one outflow source. It is possible that during the formation of the DR 21 stellar cluster, several energetic outflows may have been active at the same time thus accounting for the extraordinarily high values of outflow mass and energy which we currently observe.