Research Note

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

¹ INAF – Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
e-mail: simone.antoniucci@oa-roma.astro.it
² DIBRIS, Università di Genova, via Dodecaneso 35, 16146 Genova, Italy
³ INAF – Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy

Received: 4 April 2014
Accepted: 9 May 2014

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.