Which Stars are Ionizing the Orion Nebula ?

TL;DR

This study challenges the common assumption that Theta-1-Ori C is the main ionizing star of the Orion Nebula, revealing that Theta-2-Ori-A also significantly contributes to ionization outside the inner regions.

Contribution

It demonstrates the use of MUSE spectral imaging to identify ionizing sources and maps the 3-D structure of the nebula's ionization regions.

Findings

Theta-1-Ori-C dominates inner ionization

Theta-2-Ori-A influences outer regions

3-D mapping of ionization sources

Abstract

The common assumption that Theta-1-Ori C is the dominant ionizing source for the Orion Nebula is critically examined. This assumption underlies much of the existing analysis of the nebula. In this paper we establish through comparison of the relative strengths of emission lines with expectations from Cloudy models and through the direction of the bright edges of proplyds that Theta-2-Ori-A, which lies beyond the Bright Bar, also plays an important role. Theta-1-Ori-C does dominate ionization in the inner part of the Orion Nebula, but outside of the Bright Bar as far as the southeast boundary of the Extended Orion Nebula, Theta-2-Ori-A is the dominant source. In addition to identifying the ionizing star in sample regions, we were able to locate those portions of the nebula in 3-D. This analysis illustrates the power of MUSE spectral imaging observations in identifying sources of ionization in extended regions.