Issue |
A&A
Volume 413, Number 2, January II 2004
|
|
---|---|---|
Page(s) | 609 - 622 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20031572 | |
Published online | 18 December 2003 |
Sulphur-bearing species in the star forming region L1689N
1
Observatoire de Bordeaux, BP 89, 33270 Floirac, France
2
Laboratoire d'Astrophysique, Observatoire de Grenoble, BP 53, 38041 Grenoble Cedex 9, France
3
CESR CNRS-UPS, BP 4346, 31028, Toulouse Cedex 04, France
4
LERMA & FRE 2460 du CNRS, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
Corresponding author: V. Wakelam, wakelam@observ.u-bordeaux.fr
Received:
10
June
2002
Accepted:
7
October
2003
We report observations of the expected main S-bearing
species (SO, SO2 and H2S) in the low-mass star forming region
L1689N. We obtained large scale (~) maps of
several transitions from these molecules with the goal to study the
sulphur chemistry, i.e. how the relative abundances change in the
different physical conditions found in L1689N. We identified eight
interesting regions, where we carried out a quantitative comparative
study: the molecular cloud (as reference position), five shocked
regions caused by the interaction of the molecular outflows with the
cloud, and the two protostars IRAS 16293-2422 and 16293E. In the
cloud we carefully computed the gas temperature and density by means
of a non-LTE LVG code, while in other regions we used previous
results. We hence derived the column density of SO, SO2 and H2S, together with SiO and H2CO – which were observed previously
– and their relevant abundance ratios. We find that SiO is the
molecule that shows the largest abundance variations in the shocked
regions, whereas S-bearing molecules show more moderate variations.
Remarkably, the region of the brightest SiO emission in L1689N
is undetected in SO2, H2S and H2CO and only marginally detected in SO. In the other weaker SiO
shocks, SO2 is enhanced with respect to SO. We propose a schema in
which the different molecular ratios correspond to different ages of
the shocks. Finally, we find that SO, SO2 and H2S have
significant abundance jumps in the inner hot core of IRAS 16293-2422
and discuss the implications of the measured abundances.
Key words: ISM: abundances / ISM: molecules / stars: formation / ISM: individual objects: L1689N / ISM: individual objects: IRAS 16293-2422
© ESO, 2004
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