Submillimeter arcsecond-resolution mapping of the highly collimated protostellar jet HH 211

TL;DR

This study presents high-resolution submillimeter observations of the HH 211 protostellar jet, revealing detailed jet structure, episodic ejections, and potential jet rotation, advancing understanding of jet launching and collimation in star formation.

Contribution

First high-resolution submillimeter mapping of HH 211 revealing jet knots, rotation, and launching radius, providing new insights into protostellar jet physics.

Findings

Detected a chain of knots indicating internal shocks.

Estimated mass-loss rate of the jet as (0.7-2.8)×10^{-6} solar masses per year.

Observed velocity gradient suggesting jet rotation with a launching radius of 0.06-0.15 AU.

Abstract

We have mapped the protostellar jet HH 211 in 342 GHz continuum, SiO ($J=8-7$), and CO ($J=3-2$) emission at $\sim$ \arcs{1} resolution with the Submillimeter Array (SMA). Thermal dust emission is seen in continuum at the center of the jet, tracing an envelope and a possible optically thick compact disk (with a size $<$ 130 AU) around the protostar. A knotty jet is seen in CO and SiO as in \H2{}, but extending closer to the protostar. It consists of a chain of knots on each side of the protostar, with an interknot spacing of $\sim$ \arcs{2}$-$\arcs{3} or 600$-$900 AU and the innermost pair of knots at only $\sim$ \arcsa{1}{7} or 535 AU from the protostar. These knots likely trace unresolved internal (bow) shocks (i.e., working surfaces) in the jet, with a velocity range up to $\sim$ 25 \vkm{}. The two-sided mass-loss rate of the jet is estimated to be $\sim (0.7-2.8)\times 10^{-6}$ \solarmass{} yr$^{-1}$. The jet is episodic, precessing, and bending. A velocity gradient is seen consistently across two bright SiO knots (BK3 and RK2) perpendicular to the jet axis, with $\sim$ 1.5$\pm$0.8 \vkm{} at $\sim$ 30$\pm$15 AU, suggesting a presence of a jet rotation. The launching radius of the jet, derived from the potential jet rotation, is $\sim$ 0.15$-$0.06 AU in the inner disk.