The HH34 outflow as seen in [FeII]1.64um by LBT-LUCI

TL;DR

This study uses high-resolution IR imaging to analyze the HH34 jet, revealing detailed morphology, proper motion, and Fe depletion, and compares IR and optical tracers to understand jet composition and shock effects.

Contribution

It provides the first high-resolution IR imaging of the HH34 jet with PSF deconvolution, revealing detailed jet structure and Fe depletion patterns, and compares IR and optical emission features.

Findings

[FeII] emission closely matches [SII] morphology.

Fe gas is significantly depleted, up to 90%, in jet knots.

IR and optical images show consistent jet features and proper motions.

Abstract

Dense atomic jets from young stars copiously emit in [FeII] IR lines, which can, therefore, be used to trace the immediate environments of embedded protostars. We want to investigate the morphology of the bright [FeII] 1.64um line in the jet of the source HH34 IRS and compare it with the most commonly used optical tracer [SII]. We analyse a 1.64um narrow-band filter image obtained with the Large Binocular Telescope (LBT) LUCI instrument, which covers the HH34 jet and counterjet. A Point Spread Function (PSF) deconvolution algorithm was applied to enhance spatial resolution and make the IR image directly comparable to a [SII] HST image of the same source. The [FeII] emission is detected from both the jet, the (weak) counter-jet, and from the HH34-S and HH34-N bow shocks. The deconvolved image allows us to resolve jet knots close to about 1\arcsec from the central source. The morphology of the [FeII] emission is remarkably similar to that of the [SII] emission, and the relative positions of [FeII] and [SII] peaks are shifted according to proper motion measurements, which were previously derived from HST images. An analysis of the [FeII]/[SII] emission ratio shows that Fe gas abundance is much lower than the solar value with up to 90% of Fe depletion in the inner jet knots. This confirms previous findings on dusty jets, where shocks are not efficient enough to remove refractory species from grains.