ALMA observations of the very young Class 0 protostellar system HH 211-mms: a 30-au dusty disk with a disk-wind traced by SO?

TL;DR

This study uses high-resolution ALMA observations to reveal a 30-au dusty disk and a disk wind in the very young HH 211-mms protostellar system, providing insights into early disk formation and evolution.

Contribution

It presents the first detailed imaging of a very young Class 0 protostellar disk at 7 AU resolution, showing a thick, nearly edge-on disk with a traced disk wind.

Findings

Detected a ~30 au dusty disk with a thick, nearly edge-on structure.

Identified a rotating disk atmosphere and bipolar outflow traced by SO.

Estimated the protostellar mass to be less than ~50 Jupiter masses.

Abstract

HH 211-mms is one of the youngest Class 0 protostellar systems in Perseus at ~ 235 pc away. We have mapped its central region at up to ~ 7 AU (0.03") resolution. A dusty disk is seen deeply embedded in a flattened envelope, with an intensity jump in dust continuum at ~ 350 GHz. It is nearly edge-on and is almost exactly perpendicular to the jet axis. It has a size of ~ 30 au along the major axis. It is geometrically thick, indicating that the (sub)millimeter light emitting grains have yet to settle to the midplane. Its inner part is expected to have transformed into a Keplerian rotating disk with a radius of ~ 10 au. A rotating disk atmosphere and a compact rotating bipolar outflow are detected in SO. The outflow fans out from the inner disk surfaces and is rotating in the same direction as the flattened envelope, and hence could trace a disk wind carrying away angular momentum from the inner disk. From the rotation of the disk atmosphere, the protostellar mass is estimated to be <~ 50 M_Jup. Together with results from the literature, our result favors a model where the disk radius grows linearly with the protostellar mass, as predicted by models of pre-stellar dense core evolution that asymptotes to an $r^{-1}$ radial profile for both the column density and angular velocity.