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N. P. Abel, G. J. Ferland (U. Kentucky)
The Orion Complex is the best studied region of active star formation, with observational data available over the entire electromagnetic spectrum. These extensive observations give us a good idea of the physical structure of Orion, that being a thin (~ 0.1 parsec) blister H II region on the face of the molecular cloud OMC-1. A PDR, where the transition from atoms & ions to molecules occurs, forms an interface between the two. Most of the physical processes are driven by starlight from the Trapezium cluster, with the star Ori C being the strongest source of radiation. Observations made towards lines of sight near Ori C reveal numerous H II and molecular line intensities. Photoionization calculations have played an important role in determining the physical properties of the regions where these lines originate, but thus far have treated the H II region and PDR as separate problems. Actually these regions are energized by the same source of radiation, with the gas hydrodynamics providing the physical link between them.
Here were present a unified physical model of a single ray through the Orion Complex. We choose a region ~60’’ west of Ori C, where extensive observations exist. These include lines that originate within the H II region, background PDR, and from regions deep inside OMC-1 itself. An improved treatment of the grain, molecular hydrogen, and CO physics have all been developed as part of the continuing evolution of the plasma code Cloudy, so that we can now simultaneously predict the full spectrum with few free parameters. This provides a holistic approach that will be validated in this well-studied environment then extended to the distant starburst galaxies.
Acknowledgements: We thank the NSF and NASA for support.
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The author(s) of this abstract have provided an email address for comments about the abstract: npabel2@uky.edu
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.