SMA Observations of the HH 212 Protostellar System Chin-Fei Lee, Paul P.T. Ho, Naomi Hirano, Henrik Beuther, Tyler L. Bourke, Hsien Shang,

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SMA Observations of the HH 212 Protostellar
SystemChin-Fei Lee, Paul P.T. Ho, Naomi Hirano,
Henrik Beuther, Tyler L. Bourke, Hsien Shang,
Qizhou Zhang
HH 212 is a nearby (460 pc) protostellar jet
discovered in H2 (blue images) powered by a Class
0 protostar, IRAS 05413-0104 (indicated as an
asterisk), in Orion. It is highly collimated and
symmetric with matched pairs of bow shocks on
either side of the protostar.
a)
b)
a) A flattened envelope is seen in C18O (J2-1)
(red image) surrounding the protostar
perpendicular to the jet axis, with its inner
part seen in 13CO (J2-1) (green image). It is
infalling toward the protostar with slow rotation
preserving specific angular momentum. A
rotationally supported (accretion) disk is
expected to form within the envelope at 70 AU.
The infall rate is 6x10-6 M? yr-1. A mass of
0.15 M? is derived for the protostar assuming a
dynamical infall. The accretion time is 3x104
yrs, as expected for a Class 0 protostar (Lee et
al. 2006). b) A CO (J2-1) outflow (green image)
is seen surrounding the H2 jet, with a narrow
waist around the protostar. The morphological
relationship between the H2 jet and the CO
outflow, and the kinematics of the CO outflow
along the jet axis are both consistent with those
seen in a jet-driven bow shock model. In this
model, the jet interacts and sweeps up the
ambient material into outflow shell through
jet-driven bow shocks (Lee et al. 2006). c) Like
H2 emission, CO (J3-2) (green image) and SiO
(J8-7) (red image) emission are seen along the
jet axis but extending closer to the protostar,
tracing the bow shocks and the continuous
structures in between. The jet is episodic and
bending. It may also be slightly precessing. A
hint of jet rotation is also seen across the jet
axis. The jet has a velocity of 100-200 km/s. The
mass-loss rate is (1-2)x10-6 M? yr-1, about
15-30 of the infall rate derived from the
envelope. The jet is presumably launched from the
inner part of the accretion disk (Lee et al.
2007). References1) Lee, C.-F., Ho, P.T.P., et
al. 2006, ApJ, 639, 2922) Lee, C.-F., Ho,
P.T.P., Hirano, N., et al., 2007, ApJ, 660, in
press
c)