A spectral line survey of Orion KL in the bands 486-492 and 541-577 GHz with the Odin satellite. I. The observational data
Journal article, 2007
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.
interstellar medium
Orion KL nebula
submillimeter
interstellar molecules
Author
Henrik Olofsson
Chalmers, Department of Radio and Space Science, Radio Astronomy and Astrophysics
Carina Persson
Chalmers, Department of Radio and Space Science, Radio Astronomy and Astrophysics
N. Koning
University of Calgary
Per Bergman
Radio Astronomy and Astrophysics
P.F. Bernath
University of Arizona
John H Black
Chalmers, Department of Radio and Space Science, Radio Astronomy and Astrophysics
U. Frisk
Swedish Space Corporation (SSC)
W. Geppert
Stockholm University
T.I. Hasegawa
University of Calgary
Åke Hjalmarson
Chalmers, Department of Radio and Space Science, Radio Astronomy and Astrophysics
S. Kwok
University of Calgary
B. Larsson
AlbaNova University Center
A. Lecacheux
LESIA - Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique
Albert Nummelin
Chalmers, Computer Science and Engineering (Chalmers)
Michael Olberg
Chalmers, Department of Radio and Space Science, Radio Astronomy and Astrophysics
Chalmers, Department of Radio and Space Science, National Facility for Radio Astronomy
Aa. Sandqvist
AlbaNova University Center
Eva Wirström
Chalmers, Department of Radio and Space Science, Radio Astronomy and Astrophysics
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 476 number 2, December III 791-806Subject Categories
Physical Sciences
Astronomy, Astrophysics and Cosmology
Geophysics
DOI
10.1051/0004-6361:20077229