SIMBAD references

New, H₂ v=1-0S(1) narrow-band and K-band images of one of the most massive and most energetic YSO outflows known, DR21, are presented. We also present H₂ line profiles at positions across both outflow lobes. The complex, turbulent nature of the outflow is clearly evident in both the images and the line profiles. Remarkable asymmetries in the line profiles and oscillations in the line peak velocities are measured, particularly in the southwestern outflow lobe. We model the profiles with both planar and unresolved, bow shaped shocks. Also, from our data, and from a consideration of earlier work, two outflow episodes are inferred: an early jet produces a narrow cone-like flow towards the southwest, and a late core-dispersal phase generates the supersonic turbulence, observed here through wide, oscillating profiles from planar shock waves. These two phases are being increasingly recognised in other outflows from deeply-embedded stars.