New Radio Sources and the Composite Structure of Component B in the Very Young Protostellar System IRAS 16293-2422

TL;DR

This study presents high-resolution radio observations of IRAS 16293-2422, revealing a recent bipolar ejection event, a potential extended dusty structure, and detailed insights into the system's disk and jet components.

Contribution

It provides the first evidence of a bipolar ejection in a low-mass protostar and details the structure of the circumstellar disk and jet in IRAS 16293-2422.

Findings

Detection of a split in component A2 indicating a bipolar ejection

Possible identification of an extended dusty structure associated with component Ab

Confirmation of optically thick thermal dust emission from component B

Abstract

In this article, we report high-resolution (~ 0.1" -- 0.3"), high-sensitivity (~ 50 -100 uJy beam-1) Very Large Array 0.7 and 1.3 cm observations of the young stellar system IRAS 16293-2422 in rho-Ophiuchus. In the 0.7 cm image, component A to the south-east of the system looks like its usual binary self. In the new 1.3 cm image, however, component A2 appears to have split into two sub-components located roughly symmetrically around the original position of A2. This change of morphology is likely the result of a recent bipolar ejection, one of the very first such events observed in a low-mass source. Also in component A, a marginal detection of 0.7 cm emission associated with the submillimeter component Ab is reported. If confirmed, this detection would imply that Ab is a relatively extended dusty structure, where grain coagulation may already have taken place. With an angular size increasing with frequency, and an overall spectra index of 2, the emission from component B to the north-west of the system is confirmed to be dominated by optically thick thermal dust emission associated with a fairly massive, nearly face-on, circumstellar disk. In the central region, however, we find evidence for a modest free-free contribution that originates in a structure elongated roughly in the east-west direction. We argue that this free-free component traces the base of the jet driving the large-scale bipolar flow at a position angle of about 110 degrees that has long been known to be powered by IRAS 16293-2422.