Rotating Motion of the Outflow of IRAS 16293-2422 A1 at its Origin Point near the Protostar

TL;DR

This study uses high-resolution ALMA observations to analyze the rotating outflow structure of IRAS 16293-2422 A1, revealing its origin, angular momentum, and implications for outflow launching mechanisms in a complex protostellar system.

Contribution

First high-resolution ALMA imaging of IRAS 16293-2422 A1's outflow, demonstrating rotation and linking outflow origin to the protostar or its disk.

Findings

Outflow originates from protostar A1 or its circumstellar disk.

Detected rotation motion in SO and OCS emissions.

Estimated specific angular momentum of outflowing gas.

Abstract

The Class 0 protostar IRAS 16293$-$2422 Source A is known to be a binary system (A1 and A2) or even a multiple system, which processes a complex outflow structure. We have observed this source in the C$^{34}$S, SO, and OCS lines at 3.1 mm with the Atacama Large Millimeter/submillimeter Array (ALMA). A substructure of this source is traced by our high angular-resolution observation (0\farcs12; 20 au) of the continuum emission. The northwest-southeast (NW-SE) outflow on a 2\arcsec\ scale is detected in the SO ($J_N$ = $2_2$--$1_1$) line. Based on the morphology of the SO distribution, this bipolar outflow structure seems to originate from the protostar A1 and its circumstellar disk, or the circummultiple structure of Source A. The rotation motion of the NW-SE outflow is detected in the SO and OCS emissions. We evaluate the specific angular momentum of the outflowing gas to be $(8.6 - 14.3) \times 10^{-4}$ km s$^{-1}$ pc. If the driving source of this outflow is the protostar A1 and its circumstellar disk, it can be a potential mechanism to extract the specific angular momentum of the disk structure. These results can be a hint for the outflow launching mechanism in this source. Furthermore, they provide us with an important clue to resolve the complicated structure of IRAS 16293$-$2422 Source A.