A 100 au-Wide Bipolar Rotating Shell Emanating From The HH 212Protostellar Disk: A Disk Wind?

TL;DR

This study resolves a bipolar rotating outflow shell and a collimated jet in the HH 212 protostellar system, providing insights into disk winds and the dynamics of early star formation.

Contribution

The paper presents high-resolution observations revealing a wide-opening rotating outflow shell and a collimated jet, suggesting the presence of a disk wind or disk material pushed by an unseen wind.

Findings

The outflow shell extends ~100 au and rotates with specific angular momentum ~40 au km/s.

The jet is aligned with the SiO jet, indicating shock interactions.

The disk atmosphere shows Keplerian rotation.

Abstract

HH 212 is a Class 0 protostellar system found to host a "hamburger"-shaped dusty disk with a rotating disk atmosphere and a collimated SiO jet at a distance of ~ 400 pc. Recently, a compact rotating outflow has been detected in SO and SO2 toward the center along the jet axis at ~ 52 au (0.13") resolution. Here we resolve the compact outflow into a small-scale wide-opening rotating outflow shell and a collimated jet, with the observations in the same S-bearing molecules at ~ 16 au (0.04") resolution. The collimated jet is aligned with the SiO jet, tracing the shock interactions in the jet. The wide-opening outflow shell is seen extending out from the inner disk around the SiO jet and has a width of ~ 100 au. It is not only expanding away from the center, but also rotating around the jet axis. The specific angular momentum of the outflow shell is ~ 40 au km/s. Simple modeling of the observed kinematics suggests that the rotating outflow shell can trace either a disk wind or disk material pushed away by an unseen wind from the inner disk or protostar. We also resolve the disk atmosphere in the same S-bearing molecules, confirming the Keplerian rotation there.