Interstellar sulfur isotopes and stellar oxygen burning
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Y.-N. Chin
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Radioastronomisches Institut der Universität Bonn
- Auf dem Hügel 71, D-53121 Bonn, Germany
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C. Henkel
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Max-Planck-Institut für Radioastronomie
- Auf dem Hügel 69, D-53121 Bonn, Germany
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J.B. Whiteoak
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Australia Telescope National Facility, CSIRO Radiophysics Labs.
- P.O. Box 76, Epping, NSW 2121, Australia
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N. Langer
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Max-Planck-Institut für Astrophysik
- Karl-Schwarzschild-Str. 1, D-85740 Garching, Germany
- E.B. Churchwell
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University of Wisconsin, Astronomy Department
- 475 N. Charter St., Madison, WI 53706, USA
Paper published in January 1996 by the Main Journal of
Astronomy and Astrophysics in vol. 305, pp. 960 - 969.
If you want to have a look at the complete paper please click
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Abstract.
A 12C32S, 13C32S,
12C34S, and 12C33S J=2-1
line survey has been made to study interstellar 32S/34S
and 34S/33S ratios from the galactic disk.
The four CS isotopomers were detected in 20 star forming regions with
galactocentric distances between 3 and 9 kpc.
From a comparison of line velocities, the C33S J=2-1 rest
frequency is about 250 kHz below the value given in the Lovas (1992) catalog.
Taking 12C/13C ratios from Wilson & Rood (1994) and
assuming equal 12C32S and 13C32S
excitation temperatures and beam filling factors, 12C32S
opacities are in the range 3 to 15; average 32S/34S and
34S/33S isotope ratios are 24.4 ± 5.0 and
6.27 ± 1.01, respectively.
While no systematic variation in the 34S/33S isotope
ratio is found, the 32S/34S ratio increases with
galactocentric distance when accounting for the 12C/13C
gradient of the galactic disk.
A fit to the unweighted data yields 32S/34S =
3.3 ± 0.5 (dGC/kpc) + 4.1 ± 3.1 with a correlation
coefficient of 0.84.
Since the interstellar sulfur (S) isotopes are synthesized by oxygen burning
in massive stars, consequences for nucleosynthesis and models of chemical
evolution are briefly discussed.
Any suggestion or comments please
e-mail to einmann@asiaa.sinica.edu.tw.
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