The jet-driven molecular outflow of HH 211

We present high angular resolution (down to 1:5 00 ) interferometric maps of the CO J=1 !0 and J=2 !1 emis- sion in the molecular outflow associated with the extremely young HH 211 jet, which is located in the IC 348 molecular com- plex. At velocities close to the systemic velocity, the CO emis- sion traces the outflow cavities, while an extremely collimated, continuous jet-like structure is observed at high CO velocities. The continuum emission reveals a 0:2 M dust condensa- tion surrounding the central exciting (Class 0) protostar, clearly resolved and elongated perpendicular to the jet axis. The strong (bow-)shocks observed in vibrationally excited H2 emission are located at the terminal ends of the jet and the low-velocity CO cavities are precisely situated in their wake. Hence, the overall structure of HH 211 perfectly fits into the picture of a jet-driven flow and strongly supports shock-entrainment models as the for- mation mechanisms of young, embedded molecular outflows. The shape of the cavities traced by the low-velocity CO emis- sion can actually be (surprisingly well) reproduced by a simple, semi-analytical toy-model of a jet-driven flow, in which prompt entrainment occurs at the head of a travelling bow-shock. The estimated jet mass and mass loss rate yield a timescale of order one thousand years, in agreement with the kinematical age. Fi- nally, we discuss the physical properties of the different parts of the outflow, and especially the actual nature of the high-velocity CO jet.