A Catalog of 71 Coronal Line Galaxies in MaNGA: [NeV] is an Effective AGN Tracer

TL;DR

This study compiles the largest catalog of coronal line galaxies from MaNGA data, demonstrating that [NeV] emission is an effective tracer for high-luminosity AGNs, especially in low-dust environments.

Contribution

It presents the first large-scale analysis of optical coronal lines in MaNGA galaxies, establishing [NeV] as a reliable indicator of luminous AGNs.

Findings

[NeV] emission effectively identifies high-luminosity AGNs.

Coronal line detections are higher in galaxies with low dust extinction.

Iron coronal lines are likely destroyed by dust in high [OIII] luminosity galaxies.

Abstract

Despite the importance of AGN in galaxy evolution, accurate AGN identification is often challenging, as common AGN diagnostics can be confused by contributions from star formation and other effects (e.g., Baldwin-Phillips-Terlevich diagrams). However, one promising avenue for identifying AGNs are ``coronal emission lines" (``CLs"), which are highly ionized species of gas with ionization potentials $\ge$ 100 eV. These CLs may serve as excellent signatures for the strong ionizing continuum of AGN. To determine if CLs are in fact strong AGN tracers, we assemble and analyze the largest catalog of optical CL galaxies using the Sloan Digital Sky Survey's Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) catalog. We detect CL emission in 71 MaNGA galaxies, out of the 10,010 unique galaxies from the final MaNGA catalog, with $\ge$ 5$\sigma$ confidence. In our sample, we measure [NeV]$\lambda$3347, $\lambda$3427, [FeVII]$\lambda$3586, $\lambda$3760, $\lambda$6086, and [FeX]$\lambda$6374 emission and crossmatch the CL galaxies with a catalog of AGNs that were confirmed with broad line, X-ray, IR, and radio observations. We find that [NeV] emission, compared to [FeVII] and [FeX] emission, is best at identifying high luminosity AGN. Moreover, we find that the CL galaxies with the least dust extinction yield the most iron CL detections. We posit that the bulk of the iron CLs are destroyed by dust grains in the galaxies with the highest [OIII] luminosities in our sample, and that AGN in the galaxies with low [OIII] luminosities are possibly too weak to be detected using traditional techniques.