More Evidence on HH 212's Circumstellar Disk, Stellar Jet and More

JET MOTION, INTERNAL WORKING SURFACES, AND NESTED SHELLS IN THE PROTOSTELLAR SYSTEM HH 212

Authors:

Lee et al

Abstract:

HH 212 is a nearby (400 pc) highly collimated protostellar jet powered by a Class 0 source in Orion. We have mapped the inner 80'' (~0.16 pc) of the jet in SiO ($J=8-7$) and CO ($J=3-2$) simultaneously at ~ 0farcs 5 resolution with the Atacama Millimeter/Submillimeter Array (SMA) at unprecedented sensitivity. The jet consists of a chain of knots and bow shocks with sinuous structures in between. Compared to what we saw in our previous observations with the SMA, the jet appears to be more continuous, especially in the northern part. Some of the knots are now observed to be associated with small bow shocks, with their bow wings curving back to the jet axis, as seen in pulsed jet simulations. Two of the knots are reasonably resolved, showing kinematics consistent with sideways ejection, possibly tracing the internal working surfaces formed by a temporal variation in the jet velocity. In addition, nested shells are seen in CO around the jet axis connecting to the knots and bow shocks, driven by them. The proper motion of the jet is estimated to be ~115 ± 50 km s−1, comparing with our previous observations. The jet has a small semi-periodical wiggle with a period of ~93 yr. The amplitude of the wiggle first increases with the distance from the central source and then stays roughly constant. One possible origin of the wiggle could be the kink instability in a magnetized jet.