EDP Sciences
Press Release
Free Access
Volume 466, Number 3, May II 2007
Page(s) 999 - 1003
Section Interstellar and circumstellar matter
DOI https://doi.org/10.1051/0004-6361:20065500
Published online 24 April 2007

A&A 466, 999-1003 (2007)
DOI: 10.1051/0004-6361:20065500

Molecular oxygen in the $\rho$ Ophiuchi cloud

B. Larsson1, R. Liseau1, L. Pagani2, P. Bergman3, 4, P. Bernath5, N. Biver6, J. H. Black3, R. S. Booth3, V. Buat7, J. Crovisier6, C. L. Curry5, M. Dahlgren3, P. J. Encrenaz2, E. Falgarone8, P. A. Feldman9, M. Fich5, H. G. Florén1, M. Fredrixon3, U. Frisk10, G. F. Gahm1, M. Gerin8, M. Hagström3, J. Harju11, T. Hasegawa12, Å. Hjalmarson3, L. E. B. Johansson3, K. Justtanont1, A. Klotz13, E. Kyrölä14, S. Kwok12, 15, A. Lecacheux6, T. Liljeström16, E. J. Llewellyn17, S. Lundin10, G. Mégie18, G. F. Mitchell19, D. Murtagh20, L. H. Nordh21, L.-Å. Nyman4, M. Olberg3, A. O. H. Olofsson3, G. Olofsson1, H. Olofsson1, 3, G. Persson3, R. Plume12, H. Rickman22, I. Ristorcelli13, G. Rydbeck3, A. A. Sandqvist1, F. V. Schéele10, G. Serra13, S. Torchinsky23, N. F. Tothill19, K. Volk12, T. Wiklind3, 24, C. D. Wilson25, A. Winnberg3, and G. Witt26

1  Stockholm Observatory, AlbaNova University Center, 106 91 Stockholm, Sweden;
    e-mail: name@astro.su.se
2  LERMA & UMR 8112 du CNRS, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
3  Onsala Space Observatory, 439 92 Onsala, Sweden
4  APEX team, ESO, Santiago, Casilla 19001, Santiago 19, Chile
5  Department of Physics, University of Waterloo, Waterloo, ON N2L 3G1, Canada
6  LESIA, Observatoire de Paris, Section de Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France
7  Laboratoire d'Astronomie Spatiale, BP 8, 13376 Marseille Cedex 12, France
8  LERMA & UMR 8112 du CNRS, École Normale Supérieure, 24 rue Lhomond, 75005 Paris, France
9  Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada
10  Swedish Space Corporation, PO Box 4207, 171 04 Solna, Sweden
11  Observatory, PO Box 14, University of Helsinki, 00014 Helsinki, Finland
12  Department of Physics and Astronomy, University of Calgary, Calgary, ABT 2N 1N4, Canada
13  CESR, 9 avenue du Colonel Roche, BP 4346, 31029 Toulouse, France
14  Finnish Meteorological Institute, PO Box 503, 00101 Helsinki, Finland
15  Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, Taipei 106, Taiwan
16  Metsähovi Radio Observatory, Helsinki University of Technology, Otakaari 5A, 02150 Espoo, Finland
17  Department of Physics and Engineering Physics, 116 Science Place, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada
18  Institut Pierre Simon Laplace, CNRS-Université Paris 6, 4 place Jussieu, 75252 Paris Cedex 05, France
19  Department of Astronomy and Physics, Saint Mary's University, Halifax, NS, B3H 3C3, Canada
20  Global Environmental Measurements Group, Chalmers University of Technology, 412 96 Göteborg, Sweden
21  Swedish National Space Board, Box 4006, 171 04 Solna, Sweden
22  Uppsala Astronomical Observatory, Box 515, 751 20 Uppsala, Sweden
23  Canadian Space Agency, St-Hubert, J3Y 8Y9, Québec, Canada
24  ESA Space Telescope Division, STScI, 3700 San Martin Drive Baltimore, MD 21218, USA
25  Department of Physics and Astronomy, McMaster University, Hamilton, ON, L8S 4M1, Canada
26  Department of Meteorology, Stockholm University, 106 91 Stockholm, Sweden

(Received 26 April 2006 / Accepted 15 February 2007)

Context.Molecular oxygen, O2, has been expected historically to be an abundant component of the chemical species in molecular clouds and, as such, an important coolant of the dense interstellar medium. However, a number of attempts from both ground and from space have failed to detect O2 emission.
Aims.The work described here uses heterodyne spectroscopy from space to search for molecular oxygen in the interstellar medium.
Methods.The Odin satellite carries a 1.1 m sub-millimeter dish and a dedicated 119 GHz receiver for the ground state line of O2. Starting in 2002, the star forming molecular cloud core $\rho \, {\rm Oph \, A}$ was observed with Odin for 34 days during several observing runs.
Results.We detect a spectral line at $v_{\rm LSR}$ =+3.5 km s-1 with $\Delta v_{\rm FWHM}=1.5$ km s-1, parameters which are also common to other species associated with $\rho \, {\rm Oph \, A}$. This feature is identified as the O2 ( $N_J = 1_1 {\rm -} 1_0$) transition at 118 750.343 MHz.
Conclusions.The abundance of molecular oxygen, relative to H2 , is $5 \times 10^{-8}$ averaged over the Odin beam. This abundance is consistently lower than previously reported upper limits.

Key words: ISM: individual objects: $\rho$ Oph A -- ISM: clouds -- ISM: molecules -- ISM: abundances -- stars: formation -- radio lines: ISM

© ESO 2007

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