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TwitterA&A 476, 791-806 (2007)
DOI: 10.1051/0004-6361:20077229
A spectral line survey of Orion KL in the bands 486-492 and 541-577 GHz with the Odin satellite
I. The observational data
A. O. H. Olofsson1, 2, C. M. Persson 1, N. Koning3, P. Bergman1, 4, P. F. Bernath5, 6, 7, J. H. Black1, U. Frisk8, W. Geppert9, T. I. Hasegawa3, 10, Å. Hjalmarson1, S. Kwok3, 11, B. Larsson12, A. Lecacheux13, A. Nummelin14, M. Olberg1, Aa. Sandqvist12, and E. S. Wirström11 Onsala Space Observatory (OSO), 43992 Onsala, Sweden
e-mail: henrik@oso.chalmers.se
2 LERMA, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
3 Department of Physics and Astronomy, University of Calgary, Calgary, AB T2N 1N4, Canada
4 European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago, Chile
5 Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA
6 Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
7 Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
8 Swedish Space Corporation, PO Box 4207, 17104 Solna, Sweden
9 Molecular Physics Division, Department of Physics, Stockholm University AlbaNova, 10691 Stockholm, Sweden
10 Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, Taipei 106, Taiwan, R.O.C.
11 Department of Physics, University of Hong Kong, Hong Kong, PR China
12 Stockholm Observatory, AlbaNova University Center, 10691 Stockholm, Sweden
13 LESIA, Observatoire de Paris, Section de Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France
14 Computer science and engineering, Chalmers University of Technology, 41296 Göteborg, Sweden
(Received 2 February 2007 / Accepted 30 August 2007 )
Abstract
Aims.Spectral line surveys are useful since they allow
identification of new molecules and new lines in uniformly calibrated
data sets. The subsequent multi-transition analysis will provide improved
knowledge of molecular abundances, cloud temperatures and densities, and
may also reveal previously unsuspected blends of molecular lines, which
otherwise may lead to erroneous conclusions. Nonetheless, large portions of
the sub-millimetre spectral regime remain unexplored due to severe absorptions
by H2O and O2 in the terrestrial atmosphere. The purpose of
the measurements presented here is to cover wavelength regions at and around
0.55 mm - regions largely unobservable from the ground.
Methods.Using the Odin astronomy/aeronomy satellite, we performed the first
spectral survey of the Orion KL molecular cloud core in the bands
486-492 and 541-576 GHz with rather uniform sensitivity
(22-25 mK baseline noise). Odin's 1.1 m size telescope, equipped with four
cryo-cooled tuneable mixers connected to broad band
spectrometers, was used in a satellite position-switching mode. Two
mixers simultaneously observed different 1.1 GHz
bands using frequency steps of 0.5 GHz (25 h each).
An on-source integration time of 20 h was achieved for most bands.
The entire campaign consumed ~1100 orbits, each containing one
hour of serviceable astro-observation.
Results.We identified 280 spectral lines from 38 known interstellar
molecules (including isotopologues) having intensities in the range 80
to 0.05 K. An additional 64 weak lines remain unidentified.
Apart from the ground state rotational 11,0-10,1
transitions of ortho-H2O, H218O and H217O,
the high energy 62,4-71,7 line of
para-H2O (Eu=867
K)
and the HDO(20,2-11,1) line have been observed, as well as the
10-01 lines from NH3 and its rare isotopologue
15NH3.
We suggest assignments for some unidentified features, notably the new
interstellar molecules ND and SH-. Severe blends have been detected
in the line wings of the H218O, H217O and 13CO lines
changing the true linewidths of the outflow emission.
Key words: ISM: individual: objects: Orion KL -- ISM: lines and bands -- ISM: molecules -- line: identification -- submillimeter -- surveys
© ESO 2007