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TwitterA&A 457, 157-166 (2006)
DOI: 10.1051/0004-6361:20054746
HH135/HH136 - a luminous H
outflow towards a
high-mass protostar
R. Gredel Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: gredel@mpia.de
(Received 21 December 2005 / Accepted 4 May 2006)
Abstract
Context.Molecular hydrogen observations towards Herbig-Haro objects provide
the possibility of studying physical processes related to star formation.
Aims.Observations towards the luminous IRAS source IRAS 11101-5928 and
the associated Herbig-Haro objects HH135/HH136 are obtained
to understand whether high-mass stars form via the same
physical processes as their low-mass counterparts.
Methods.Near-infrared imaging and spectroscopy are used to infer H2 excitation
characteristics. A theoretical H2 spectrum is constructed from a
thermal ro-vibrational population distribution and compared to the
observations.
Results.The observations reveal the presence of
a well-collimated, parsec-sized H2 outflow
with a total H2 luminosity of about 
.
The bulk of the molecular gas is characterized
by a ro-vibrational excitation temperature of
K. A
small fraction (0.3%) of the molecular gas is very hot, with
excitation temperatures around 5500 K.
The molecular emission is associated with strong
[FeII] emission.
The H2 and [FeII] emission characteristics
indicate the presence of fast,
dissociative J-shocks at speeds of
km s-1.
Electron densities of
ne = 3500-4000 cm-3 are inferred
from the [FeII] line ratios.
Conclusions.The large H2 luminosity combined
with the very
large source luminosity suggests that the high-mass protostar
that powers the HH135/HH136 flow forms via accretion, but with a
significantly increased accretion rate compared to that
of low-mass protostars.
Key words: ISM: individual objects: HH135 -- ISM: individual objects: HH136 -- ISM: Herbig-Haro objects -- ISM: jets and outflows
© ESO 2006