Measurement of Rare CO Isotopomers Toward the Ophiuchi Molecular Cloud Emission of Translucent Molecular Clouds: Observations and PDR Models
Abstract
We report the detection of 13C17O, and present observations of three additional rare CO isotopomers made towards core C of the ρ Ophiuchi molecular cloud. The data encompass single pointed observations of the J = 1 → 0 and J = 2 → 1 rotational transitions for C18O, C17O and 13C17O, and the J = 1 → 0 transition for 13C18O. Emission is detected for all isotopes and transitions observed. For the two 17O-containing species, the interstellar spectra display a partially resolved hyperfine spectrum due to the I = 5/2 spin of the 17O nucleus. The isotope abundance ratios derived from these measurements are [12C] / [13C] = 65.0 ± 6.3(stat.) ± 9.2(syst.) and [18O] / [17O] = 4.15 ± 0.52(stat.) ± 0.59(syst.), consistent with recent measurements for nearby molecular clouds. Thus, our measurements support the idea that both ratios are smaller in the local ISM than their terrestrial value of 89 and 5.5.
- Publication:
-
SFChem 2002: Chemistry as a Diagnostic of Star Formation
- Pub Date:
- 2003
- Bibcode:
- 2003cdsf.conf..254B