Gas-phase SO
in absorption towards massive protostars*
1
Kapteyn Institute, PO Box 800, 9700 AV Groningen, The Netherlands
2
Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands
3
SRON, PO Box 800, 9700 AV Groningen, The Netherlands
Corresponding author: J. V. Keane, jacquie@astro.rug.nl
Received:
18
June
2001
Accepted:
11
July
2001
We present the first detection of the 
ro-vibrational
band of gas-phase 
in absorption in the mid-infrared spectral region around
7.3
of a sample of deeply embedded massive protostars. Comparison with
model spectra shows that the derived excitation temperatures correlate with
previous C2H2 and HCN studies, indicating that the same warm gas
component is probed. The column densities are similar along all lines
of sight suggesting that the formation has saturated, but not destroyed,
and the absolute abundances of are high (~10-7). Both the
high temperature and the high abundance of the detected are not
easily explained by standard hot core chemistry models. Likewise,
indicators of shock induced chemistry are lacking.
Key words: stars: formation / ISM: abundances / ISM: molecules
© ESO, 2001