Detection of CS and C2H in absorption.
Abstract
A search has been conducted for CS(J = 2 - 1), C2H(N = 1 - 0), and N2H(+)(J = 1 - 0) absorptions towards W 49, DR 21, and Cas A. CS and C2H were detected in absorption against W 49 and C2H against DR 21. The fractional abundances (relative to H2) towards W 49 are estimated to be about 5 x 10 to the -9th for CS, 5 x 10 to the -8th for C2H, and less than 5 x 10 to the -10th for N2H(+). Somewhat lower values are obtained as upper limits towards Cas A. The detections of absorption features of these and other molecules imply that many molecular species are abundant also in clouds, where the density is so low that the energy levels of the molecules are not appreciably excited above the cosmic background radiation. The observations will be compared with earlier observations of HCO(+) and HCN towards the same sources.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- December 1984
- Bibcode:
- 1984A&A...141..323N
- Keywords:
-
- Absorption Spectra;
- Astronomical Spectroscopy;
- Interstellar Matter;
- Molecular Clouds;
- Abundance;
- Carbon Compounds;
- Hydrocarbons;
- Molecular Ions;
- Molecular Spectra;
- Positive Ions;
- Sulfur Compounds;
- Astrophysics