The Flattened, Rotating Molecular Gas Core of Protostellar Jet HH 212

The recently discovered protostellar jet known as HH212 is beautifullysymmetric, with a series of paired shock knots and bow shocks on either side ofthe exciting source region, IRAS 05413-0104 (Zinnecker et al. 1998). We presentVLA ammonia maps of the IRAS 05413-0104 molecular gas envelope in which theprotostellar jet source is embedded. We find that the envelope, with mass of0.2 M(sun) detected by the interferometer, is flattened perpendicular to thejet axis with a FWHM diameter of 12000 AU and an axis ratio of 2:1, as seen inNH3 (1,1) emission. There is a velocity gradient of about 4-5 km sec^-1 pc^-1across the flattened disk-like core, suggestive of rotation around an axisaligned with the jet. Flux-weighted mean velocities increase smoothly withradius with a roughly constant velocity gradient. In young (Class 0) systemssuch as HH212, a significant amount of material is still distributed in a largesurrounding envelope, and thus the observable kinematics of the system mayreflect the less centrally condensed, youthful state of the source andobscuration of central dynamics. The angular momentum of this envelope materialmay be released from infalling gas through rotation in the HH212 jet, as recentobservations suggest (Davis et al. 2000). A blue-shifted wisp or bowl ofemitting gas appears to be swept up along the blue side of the outflow,possibly lining the cavity of a wider angle wind around the more collimatedshock jet axis. Our ammonia (2,2)/(1,1) ratio map indicates that this very coldcore is heated to 14 Kelvin degrees in a centrally condensed area surroundingthe jet source. This edge-on core and jet system appears to be young and deeplyembedded. This environment, however, is apparently not disrupting the pristinesymmetry and collimation of the jet.Comment: 12 pages, including figures. Pages 11 and 12 are both Figure 2; Page 12 is a color version and the gradients in it do not print correctly on black-and-white printers. Thus ignore page 12 if printing or viewing in black-and-whit