The HH34 outflow as seen in [Fe ii] 1.64 µm by LBT-LUCI

Abstract

Context. Dense atomic jets from young stars copiously emit in [Fe ii] IR lines, which can, therefore, be used to trace the immediate environments of embedded protostars.
Aims: We want to investigate the morphology of the bright [Fe ii] 1.64 μm line in the jet of the source HH34 IRS and compare it with the most commonly used optical tracer [S ii].
Methods: We analyse a 1.64 μm narrow-band filter image obtained with the Large Binocular Telescope (LBT) LUCI instrument, which covers the HH34 jet and counterjet. A point spread function deconvolution algorithm was applied to enhance spatial resolution and make the IR image directly comparable to a [S ii] HST image of the same source.
Results: The [Fe ii] 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''from the central source. The morphology of the [Fe ii] emission is remarkably similar to that of the [S ii] emission, and the relative positions of [Fe ii] and [S ii] peaks are shifted according to proper motion measurements, which were previously derived from HST images. An analysis of the [Fe ii]/[S ii] 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.

Based on observations obtained with the Large Binocular Telescope.