Atomic silicon towards the Orion-KL nebula

Abstract

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 68.5mum 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. 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