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Astron. Astrophys. 348, 227-232 (1999)

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Atomic silicon towards the Orion-KL nebula *

C. Gry 1, G. Pineau des Forêts 2 and C.M. Walmsley 3

1 ISO Data Centre, ESA Astrophysics Division, Villafranca del Castillo, P.O.Box 50727, E-28080 Madrid, Spain
2 Observatoire de Paris, F-92195 Meudon Principal Cedex, France
3 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy

Received 8 April 1999 / Accepted 7 June 1999


We have used the Long Wavelength Spectrometer (LWS) on board ISO to observe the fine structure lines of atomic silicon at 68.5 and 129.7 microns towards the Orion Kleinmann-Low nebula. Our data show evidence for the detection of the J=2-1 transition at 68.5µm with a signal-to-noise ratio of 5. We consider the formation of the observed emission line and conclude that it is likely to form in the C-shock associated with the outflow emanating from the young massive stars in that complex. We give limits on the shock velocity and magnetic field required to explain the observed line in this manner.

Key words: ISM: abundances – ISM: H ii regions – ISM: individual objects: Orion-KL nebula – ISM: jets and outflows

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) with the participation of ISAS and NASA

Send offprint requests to: M. Walmsley

Correspondence to: walmsley@arcetri.astro.it

© European Southern Observatory (ESO) 1999

Online publication: July 16, 1999