First large scale Herbig-Haro jet driven by a proto-brown dwarf
  We report the discovery of a new Herbig-Haro jet, HH 1165, in SOAR
narrow-band imaging of the vicinity of the sigma Orionis cluster. HH 1165 shows
a spectacular extended and collimated spatial structure, with a projected
length of 0.26 pc, a bent C-shaped morphology, multiple knots, and fragmented
bow-shocks at the apparent ends of the flow. The Halpha image shows a bright
halo with a clumpy distribution of material seen around the driving source, and
curved reflection nebulosity tracing the outflow cavities. The driving source
of HH 1165 is a Class I proto-brown dwarf, Mayrit 1701117 (M1701117), with a
total (dust+gas) mass of ~36 MJup and a bolometric luminosity of ~0.1 Lsun.
High-resolution VLT/UVES spectra of M1701117 show a wealth of emission lines
indicative of strong outflow and accretion activity. SOAR/Goodman
low-resolution spectra along the jet axis show an asymmetrical morphology for
HH 1165. We find a puzzling picture wherein the north-west part exhibits a
classical HH jet running into a pre-dominantly neutral medium, while the
southern part resembles an externally irradiated jet. The C-shaped bending in
HH 1165 may be produced by the combined effects from the massive stars in the
ionization front to the east, the sigma Orionis core to the west, and the close
proximity to the B2-type star HR 1950. HH 1165 shows all of the signatures to
be considered as a scaled-down version of parsec-length HH jets, and can be
termed as the first sub-stellar analog of a protostellar HH jet system.
