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Astron. Astrophys. 318, 252-255 (1997)

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P. Maréchal 1, L. Pagani 1, W.D. Langer 2 and A. Castets 3

1 DEMIRM, Observatoire de Paris, 61 Av. de l'Observatoire, F-75014 Paris, France
2 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
3 Observatoire de Grenoble, B.P. 53X, F-38041 Grenoble Cedex, France

Received 22 April 1996 / Accepted 20 June 1996


After our first tentative detection of the molecular oxygen 16 O18 O isotopomer obtained during the winter '92/93 (Pagani et al. 1993), we attempted to confirm our results by making a deep search in other sources and in other positions in L134N. We have not been able to confirm the original detection in any other place in L134N but we obtain good upper limits towards NGC 2264(IRS2), TMC2, OMC3 and L134N (4', -1') and (5.2', -1) which give an O2 /CO ratio upper limit near 0.1 - the lowest yet obtained toward galactic sources - instead of 0.3-0.4 as predicted by gas phase chemical equilibrium models. As our sample consists of eight cold or lukewarm dark clouds, the low abundance of O2 with respect to CO seems to be a general characteristic of dark clouds.

Key words: ISM: clouds; molecules; abundances – radio lines: ISM

Send offprint requests to: P. Maréchal (Priscilla.Marechal@obspm.fr)

© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998