# The structure of the Orion Nebula in the direction of Theta 1 Ori C

## TL;DR

This paper presents a new model of the Orion Nebula's structure near Theta 1 Ori C, integrating optical and infrared spectral data to reveal layered velocity components and their relation to stellar winds and expanding shells.

## Contribution

It introduces a comprehensive model combining multiple spectral lines to map the nebula's layered structure and velocity components, advancing understanding of its dynamics.

## Key findings

- Closest ionization layer is 1.3 pc from Theta 1 Ori C
- Foreground [C II] emission is part of an expanding shell
- Layers are blueshifted due to stellar wind pressure

## Abstract

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 micron line have shown that there are new velocity systems associated with the foreground Veil and the material lying between Theta 1 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 Theta 1 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 Theta 1 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 micron 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.