Rotation and Outflow motions in the very low-mass Class 0 protostellar
  system HH 211 at subarcsecond resolution
  HH 211 is a nearby young protostellar system with a highly collimated jet. We
have mapped it in 352 GHz continuum, SiO (J=8-7), and HCO+ (J=4-3) emission at
up to ~ 0.2" resolution with the Submillimeter Array (SMA). The continuum
source is now resolved into two sources, SMM1 and SMM2, with a separation of ~
84 AU. SMM1 is seen at the center of the jet, probably tracing a (inner) dusty
disk around the protostar driving the jet. SMM2 is seen to the southwest of
SMM1 and may trace an envelope-disk around a small binary companion. A
flattened envelope-disk is seen in HCO+ around SMM1 with a radius of ~ 80 AU
perpendicular to the jet axis. Its velocity structure is consistent with a
rotation motion and can be fitted with a Keplerian law that yields a mass of ~
50+-15 Jupiter mass (a mass of a brown dwarf) for the protostar. Thus, the
protostar could be the lowest mass source known to have a collimated jet and a
rotating flattened envelope-disk. A small-scale (~ 200 AU) low-speed (~ 2 km/s)
outflow is seen in HCOP+ around the jet axis extending from the envelope-disk.
It seems to rotate in the same direction as the envelope-disk and may carry
away part of the angular momentum from the envelope-disk. The jet is seen in
SiO close to ~ 100 AU from SMM1. It is seen with a "C-shaped" bending. It has a
transverse width of <~ 40 AU and a velocity of ~ 170+-60 km/s. A possible
velocity gradient is seen consistently across its innermost pair of knots, with
~ 0.5 km/s at ~ 10 AU, consistent with the sense of rotation of the
envelope-disk. If this gradient is an upper limit of the true rotational
gradient of the jet, then the jet carries away a very small amount of angular
momentum of ~ 5 AU km/s and thus must be launched from the very inner edge of
the disk near the corotation radius.
