A spectral line survey of Orion KL in the bands 486-492 and 541-577 GHz with the Odin satellite. II. Data analysis
Journal article, 2007
Aims.We investigate the physical and chemical conditions in a typical star forming region, including an unbiased search for new molecules in a spectral region previously unobserved.
Methods.Due to its proximity, the Orion KL region offers a unique laboratory of molecular astrophysics in a chemically rich, massive star forming region. Several ground-based spectral line surveys have been made, but due to the absorption by water and oxygen, the terrestrial atmosphere is completely opaque at frequencies around 487 and 557 GHz. To cover these frequencies we used the Odin satellite to perform a spectral line survey in the frequency ranges 486-492 GHz and 541-577 GHz, filling the gaps between previous spectral scans. Odin's high main beam efficiency, $\eta_{{\rm mb}}$ = 0.9, and observations performed outside the atmosphere make our intensity scale very well determined.
Results.We observed 280 spectral lines from 38 molecules including isotopologues, and, in addition, 64 unidentified lines. A few U-lines have interesting frequency coincidences such as ND and the anion SH-. The beam-averaged emission is dominated by CO, H2O, SO2, SO, 13CO and CH3OH. Species with the largest number of lines are CH3OH, (CH3)2O, SO2, 13CH3OH, CH3CN and NO. Six water lines are detected including the ground state rotational transition 11,0-10,1 of o-H2O, its isotopologues o-H218O and o-H217O, the Hot Core tracing p-H2O transition 62,4-71,7, and the 20, 2-11,1 transition of HDO. Other lines of special interest are the 10-0$_$ transition of NH3 and its isotopologue 15NH3. Isotopologue abundance ratios of D/H, 12C/13C, 32S/34S, 34S/33S, and 18O/17O are estimated. The temperatures, column densities and abundances in the various subregions are estimated, and we find very high gas-phase abundances of H2O, NH3, SO2, SO, NO, and CH3OH. A comparison with the ice inventory of ISO sheds new light on the origin of the abundant gas-phase molecules.
interstellar medium
submillimeter
Orion KL nebula
interstellar molecules
Author
Carina Persson
Chalmers, Department of Radio and Space Science, Radio Astronomy and Astrophysics
Henrik Olofsson
Chalmers, Department of Radio and Space Science, Radio Astronomy and Astrophysics
N. Koning
University of Calgary
Per Bergman
Chalmers, Department of Radio and Space Science, National Facility for Radio Astronomy
P.F. Bernath
University of Waterloo
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
Stockholm Observatory
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, National Facility for Radio Astronomy
Chalmers, Department of Radio and Space Science, Radio Astronomy and Astrophysics
Aa. Sandqvist
Stockholm Observatory
Eva Wirström
Chalmers, Department of Radio and Space Science, Radio Astronomy and Astrophysics
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 476 2, December III 807-827Subject Categories
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361:20077225