ALMA discovery of a rotating SO/SO$_2$ flow in HH212. A possible MHD disk wind?

TL;DR

This study uses ALMA observations to identify a rotating, slower molecular flow in HH212, suggesting a magnetohydrodynamic disk wind that influences the jet and outflow structure, with implications for star formation efficiency.

Contribution

First observational evidence of a rotating MHD disk wind in HH212, linking molecular flow characteristics with theoretical predictions and jet launching mechanisms.

Findings

Detected a rotating SO/SO₂ flow wider and slower than the jet.

Broad outflow cavity likely shaped by a slow wind, not a fast one.

Disk wind could limit star formation efficiency to 50%.

Abstract

We wish to constrain the possible contribution of a magnetohydrodynamic disk wind (DW) to the HH212 molecular jet. We mapped the flow base with ALMA Cycle 4 at 0.13"$\sim$ 60 au resolution and compared these observations with synthetic DW predictions. We identified, in SO/SO$_2$, a rotating flow that is wider and slower than the axial SiO jet. The broad outflow cavity seen in C$^{34}$S is not carved by a fast wide-angle wind but by this slower agent. Rotation signatures may be fitted by a DW of a moderate lever arm launched out to $\sim$ 40 au with SiO tracing dust-free streamlines from 0.05-0.3 au. Such a DW could limit the core-to-star efficiency to $\leq$50%.