SIMBAD references

1997A&A...328..617M - Astronomy and Astrophysics, volume 328, 617-627 (1997/12-2)

Chemistry and rotational excitation of O2 in interstellar clouds. II. The 16O18O isotopomer.


Abstract (from CDS):

Although molecular oxygen O2 is predicted to be an important constituent of the interstellar gas, it has not yet been observed in Galactic interstellar clouds. While ongoing O2 observation projects in our Galaxy have to use stratospheric balloons or satellites, several teams have already tried to observe its isotopomer 16O18O with ground-based telescopes. In this paper, a chemical model of interstellar clouds including 18O and 13C isotopic reactions with a non-LTE calculation of 16O18O rotational population has been used to predict the intensity of the 3 16O18O lines observable from the ground, namely the 234, 298 and 402 GHz lines. These predictions are compared to the upper limits obtained by Marechal et al. (1997A&A...318..252M) and to the tentative detection obtained by Pagani et al. (1993A&A...274L..13P) towards L134N. We show that only the 234 GHz line is observable with today's receivers and that the strong upper limits we have reported are not compatible with a standard steady-state model. Clumpiness, high (0.7) C/O ratio or other non-standard models are required to explain our observations. The consequence of the 18O isotopic fractionation is also discussed.

Abstract Copyright:

Journal keyword(s): molecular processes - ISM: abundances, molecules - radio lines: ISM

VizieR on-line data: <Available at CDS (J/A+A/328/617): table4.tex table4a table4b table4c>

Simbad objects: 10

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