The structure of the Orion Nebula in the direction of θ1 Ori C.
ABEL N.P., FERLAND G.J. and O'DELL C.R.
Abstract (from CDS):
We have used existing optical emission and absorption lines, [C II] emission lines, and H I absorption lines to create a new model for a central column of material near the Trapezium region of the Orion Nebula. This was necessary because recent high spectral resolution spectra of optical emission lines and imaging spectra in the [C II] 158 µm line have shown that there are new velocity systems associated with the foreground Veil and the material lying between θ1 Ori C and the main ionization front of the nebula. When a family of models generated with the spectral synthesis code Cloudy were compared with the surface brightness of the emission lines and strengths of the Veil absorption lines seen in the Trapezium stars, distances from θ1 Ori C were derived, with the closest, highest ionization layer being 1.3 pc. The line-of-sight distance of this layer is comparable with the size of the inner Huygens region in the plane of the sky. These layers are all blueshifted with respect to the Orion Nebula Cluster of stars, probably because of the pressure of a hot central bubble created by θ1 Ori C's stellar wind. We find velocity components that are ascribed to both sides of this bubble. Our analysis shows that the foreground [C II] 158 µm emission is part of a previously identified layer that forms a portion of a recently discovered expanding shell of material covering most of the larger Extended Orion Nebula.