Deciphering the 3-D Orion Nebula-II: A low-ionization region of multiple velocity components southwest of Theta1OriC confounds interpretation of low velocity resolution studies of temperature, density, and abundance

TL;DR

This study reveals complex, multi-velocity, low-ionization regions in the Orion Nebula that complicate previous measurements of its physical conditions and abundances, emphasizing the need for high spectral resolution in future analyses.

Contribution

The paper identifies multiple velocity components in the Orion Nebula's southwest region, challenging previous assumptions and highlighting the importance of high spectral resolution for accurate diagnostics.

Findings

Discovery of two distinct velocity systems in the Orion Nebula.

Identification of low-ionization, complex regions affecting abundance measurements.

Implication that earlier studies may have oversimplified the nebula's structure.

Abstract

We establish that there are two velocity systems along lines-of-sight that contribute to the emission-line spectrum of the the brightest parts of the Orion Nebula. These overlie the Orion-S embedded molecular cloud southwest of the dominant ionizing star (Theta1OriC). Examination of 10x10" samples of high spectral resolution emission-line spectra of this region reveals it to be of low ionization, with velocities and ionization different from the central part of the Nebula. These properties jeopardize earlier determinations of abundance and physical conditions since they indicate that this region is much more complex than has been assumed in analyzing earlier spectroscopic studies and argue for use of very high spectral resolution or known simple regions in future studies.