FAUST III. Misaligned rotations of the envelope, outflow, and disks in the multiple protostellar system of VLA 1623$-$2417

TL;DR

This study investigates the misaligned rotations of the envelope, outflows, and disks in the VLA 1623 protostellar system, revealing complex dynamics and magnetic field interactions in a low-mass star-forming region.

Contribution

It provides the first detailed analysis of rotation misalignments and velocity gradients in VLA 1623, highlighting the influence of magnetic fields and outflow dynamics.

Findings

The circum-binary disk of VLA 1623A is misaligned by about 12 degrees with the outflow.

A velocity gradient opposite to the envelope and outflow was detected toward VLA 16293B.

The outflow's launching radius is estimated to be 5-16 au, assuming rotation causes the velocity gradient.

Abstract

We report a study of the low-mass Class-0 multiple system VLA 1623AB in the Ophiuchus star-forming region, using H$^{13}$CO$^+$ ($J=3-2$), CS ($J=5-4$), and CCH ($N=3-2$) lines as part of the ALMA Large Program FAUST. The analysis of the velocity fields revealed the rotation motion in the envelope and the velocity gradients in the outflows (about 2000 au down to 50 au). We further investigated the rotation of the circum-binary VLA 1623A disk as well as the VLA 1623B disk. We found that the minor axis of the circum-binary disk of VLA 1623A is misaligned by about 12 degrees with respect to the large-scale outflow and the rotation axis of the envelope. In contrast, the minor axis of the circum-binary disk is parallel to the large-scale magnetic field according to previous dust polarization observations, suggesting that the misalignment may be caused by the different directions of the envelope rotation and the magnetic field. If the velocity gradient of the outflow is caused by rotation, the outflow has a constant angular momentum and the launching radius is estimated to be $5-16$ au, although it cannot be ruled out that the velocity gradient is driven by entrainments of the two high-velocity outflows. Furthermore, we detected for the first time a velocity gradient associated with rotation toward the VLA 16293B disk. The velocity gradient is opposite to the one from the large-scale envelope, outflow, and circum-binary disk. The origin of its opposite gradient is also discussed.