Issue |
A&A
Volume 393, Number 3, October III 2002
|
|
---|---|---|
Page(s) | 1035 - 1051 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20021062 | |
Published online | 01 October 2002 |
1–2.5 μm spectra of jets from young stars: Strong
emission in
HH111, HH240-241 and HH120*
INAF-Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Italy e-mail: bruni,caratti,teresa,dloren@mporzio.astro.it
Corresponding author: B. Nisini, bruni@mporzio.astro.it
Received:
4
June
2002
Accepted:
19
July
2002
As part of a 1–2.5 μm spectroscopic survey of jets and molecular outflows,
we present the spectra of three Herbig Haro chains
(HH111, HH240/241, HH120) characterized by strong emission from
several transitions originating from the first 13 fine structure levels.
Such emission is correlated with optical
emission and appears to decrease moving away from the driving source.
From the analysis of the
lines we have derived electron densities values in the
range
–
cm-3, which are systematically larger than
those inferred from optical
line ratios.
We suggest that
lines, having critical densities higher than the optical
transitions, trace either regions of the post-shock cooling layers
with higher compression, or a section of the jet axis at a higher degree
of ionization.
Strong H2 emission lines are also detected along the three flows and their
analysis indicates that a combination of different shocks
can be responsible for their excitation
in the different objects. Consequently the
line emission, which requires the presence of fast dissociative shocks,
is completely independent from the excitation mechanism giving rise to the
molecular emission.
In addition to the
and H2 lines, emission from other species such as
,
,
as well as recombination lines from the Paschen
series are detected and have been used as a reference to infer the gas-phase
iron abundance in the observed HH objects. We estimate a grain destruction efficiency
of about 30–60%: the highest value is found for HH240A, which also shows the
highest degree of excitation among the observed objects.
Key words: stars: circumstellar matter / infrared: ISM / ISM: Herbig-Haro objects / ISM: jets and outflows
© ESO, 2002
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