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J/A+A/305/960 Interstellar S isotopes (Chin+, 1996)
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Interstellar sulfur isotopes and stellar oxygen burning
Chin Y.-N., Henkel C., Whiteoak J.B., Langer N., Churchwell E.B.
<Astron. Astrophys. 305, 960 (1996)>
=1996A&A...305..960C (SIMBAD/NED BibCode)
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ADC_Keywords: Radio lines
Keywords: nuclear reactions, nucleosynthesis, abundances - ISM: abundances -
ISM: molecules - Galaxy: evolution; abundances - radio lines: ISM
Description:
A ^12^C^32^S, ^13^C^32^S, ^12^C^34^S, and ^12^C^33^S J=2-1 line survey
has been made to study interstellar ^32^S/^34^S and ^34^S/^33^S ratios
from the galactic disk. The four CS isotopomers were detected in 20 star
forming regions with galactocentric distances between 3 and 9kpc. From a
comparison of line velocities, the C^33^S J=2-1 rest frequency is ~250kHz
below the value given in the Lovas (1992) catalog. Taking ^12^C/^13^C
ratios from Wilson & Rood (1994) and assuming equal ^12^C^32^S and
^13^C^32^S excitation temperatures and beam filling factors, ^12^C^32^S
opacities are in the range 3 to 15; average ^32^S/^34^S and ^34^S/^33^S
isotope ratios are 24.4+/-5.0 and 6.27+/-1.01, respectively. While no
systematic variation in the ^34^S/^33^S isotope ratio is found, the
^32^S/^34^S ratio increases with galactocentric distance when accounting
for the ^12^C/^13^C gradient of the galactic disk. A fit to the unweighted
data yields ^32^S/^34^S=3.3+/-0.5(D_GC_/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.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1 89 80 Line parameters from unsmoothed J=2-1 spectra
of the four measured CS isotopomers
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Byte-by-byte Description of file: table1
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Bytes Format Units Label Explanations
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2- 15 A14 --- Object Object
17- 18 I2 h RAh Right ascension (1950)
20- 21 I2 min RAm Right ascension (1950)
23- 26 F4.1 s RAs Right ascension (1950)
28 A1 --- DE- Declination sign
29- 30 I2 deg DEd Declination (1950)
32- 33 I2 arcmin DEm Declination (1950)
35- 36 I2 arcsec DEs Declination (1950)
38- 43 A6 --- Molec Molecule
45- 47 I3 mK rms rms noise of the spectrum in units of Tmb (1)
49- 55 F7.3 K.km/s IntTmb Integral of main beam brightness
temperature in the velocity
57- 61 F5.3 K.km/s e_IntTmb Error on the integral of main beam
brightness temperature in the velocity
62- 67 F6.3 K Tmb Main beam brightness temperature
69- 74 F6.1 km/s VLSR LSR velocity
76- 78 F3.1 km/s FWHM Full width to half maximum linewidths
80- 83 I4 km/s Vel1 Lower value of the velocity range
85- 88 I4 km/s Vel2 Upper value of the velocity range
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Note (1): rms contains the r.m.s. noise of the spectrum in units of Tmb.
This is only then equivalent to the Tmb r.m.s. error, if the
line is only seen in one channel. If the line is broader, the error
in Tmb is smaller.
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(End) Simona Mei [CDS] 07-Sep-1995