MSX Observations of Diffuse UV Emission in Orion

Abstract

We have observed intense diffuse radiation in the UV (1400 Å - 2600 Å) from three fields around M42 in Orion. Intensities of 20000 photons cm-2 sr-1 s-1 Å-1 were observed to the east and west of M42 with 8000 photons cm-2 sr-1 s-1 Å-1 south of the nebula. Enhanced emission, perhaps associated with a nearby complex of molecular clouds observed in CO, was detected in one of the fields. The IRAS 1000 μm emission in that region is highly correlated with the UV intensity with a UV-IR ratio of 40 photons cm-2 sr-1 s-1 Å-1 (MJy sr-1)-1. In the other two fields there was no structure in the diffuse emission nor was there any correlation with the IRAS emission.