The reflection-symmetric wiggle of the young protostellar jet HH 211

TL;DR

This study uses high-resolution observations of the HH 211 jet to analyze its reflection-symmetric wiggle, revealing a possible very low-mass protobinary source and enhanced molecular abundances linked to internal shocks.

Contribution

It provides detailed imaging and modeling of the HH 211 jet, suggesting the presence of a low-mass protobinary and elucidating molecular abundance enhancements due to shocks.

Findings

Jet exhibits reflection-symmetric wiggle fitted by an orbiting source model.

Source likely a very low-mass protobinary with ~60 M_Jup and 4.6 AU separation.

Molecular abundances of SiO and SO are highly enhanced near the jet, related to shocks.

Abstract

HH 211 is a highly collimated jet originating from a nearby young Class 0 protostar. Here is a follow-up study of the jet with our previous observations at unprecedented resolution up to ~ 0.3" in SiO (J=8-7), CO (J=3-2), and SO (N_J=8_9-7_8). SiO, CO, and SO can all be a good tracer of the HH 211 jet, tracing the internal shocks in the jet. Although the emissions of these molecules show roughly the same morphology of the jet, there are detailed differences. In particular, the CO emission traces the jet closer to the source than the SiO and SO emissions. In addition, in the better resolved internal shocks, both the CO and SO emission are seen slightly ahead of the SiO emission. The jet is clearly seen on both sides of the source with more than one cycle of wiggle. The wiggle is reflection-symmetric about the source and can be reasonably fitted by an orbiting source jet model. The best-fit parameters suggest that the source itself could be a very low-mass protobinary with a total mass of ~ 60 M_Jup and a binary separation of ~ 4.6 AU. The abundances of SiO and SO in the gas phase are found to be highly enhanced in the jet as compared to the quiescent molecular clouds, even close to within 300 AU from the source where the dynamical time scale is <10 yrs. The abundance enhancements of these molecules are closely related to the internal shocks. The detected SiO is either the consequence of the release of Si-bearing material from dust grains or of its formation via gas chemistry in the shocks. The SO, on the other hand, seems to form via gas chemistry in the shocks.