Observations of the 145.5 micron [O I] emission line in the Orion Nebula

We have obtained a first set of observations of the [O I] 3P0 -3P1 (145.5 μm) transition. We observed the line both in a 1' x 1' beam centered on the Trapezium and in a 7' x 7' beam encompassing most of the Orion Nebula. We also have constructed a wide-beam (7' x 7') map of the region which shows that most of the emission is confined to the central regions of the nebula. These observations may be compared with reported measurement of the 3P1-3P2 (63.2 μm) transition in Orion and are consistent with optically thin emission in the 145.5 μm line and self-absorbed 63.2 μm emission lines. We discuss mechanisms for the excitation of neutral oxygen and conclude that much of the observed emission originates in the thin, radio recombination line-emitting C II/H I envelope bordering on the H II region