Probing jets from young embedded sources: clues from HST near-IR [Fe II] images

TL;DR

This study uses high-resolution HST near-infrared [Fe II] imaging to analyze the structure, velocities, and asymmetries of jets from young embedded stars, providing new insights into jet collimation and potential binary companions.

Contribution

First high-resolution near-infrared imaging of Class 0/I jets revealing detailed jet widths, trajectories, and asymmetries, and suggesting possible stellar companions.

Findings

Jets are highly collimated up to large distances.

Counter-jets are detected in all cases, with velocities of a few hundred km/s.

Evidence of a low-mass stellar companion in HH 111.

Abstract

We present near-infrared [Fe II] images of four Class 0/I jets (HH 1/2, HH 34, HH 111, HH 46/47) observed with the Hubble Space Telescope Wide Field Camera 3. The unprecedented angular resolution allows us to measure proper motions, jet widths and trajectories, and extinction along the jets. In all cases, we detect the counter-jet which was barely visible or invisible at shorter wavelengths. We measure tangential velocities of a few hundred km/s, consistent with previous HST measurements over 10 years ago. We measure the jet width as close as a few tens of au from the star, revealing high collimations of about 2 degrees for HH 1, HH 34, HH 111 and about 8 degrees for HH 46, all of which are preserved up to large distances. For HH 34, we find evidence of a larger initial opening angle of about 7 degrees. Measurement of knot positions reveals deviations in trajectory of both the jet and counter-jet of all sources. Analysis of asymmetries in the inner knot positions for HH 111 suggests the presence of a low mass stellar companion at separation 20-30 au. Finally, we find extinction values of 15-20 mag near the source which gradually decreases moving downstream along the jet. These observations have allowed us to study the counter-jet at unprecedented high angular resolution, and will be a valuable reference for planning future JWST mid-infrared observations which will peer even closer into the jet engine.