The Physics of the Coronal and Broad Line Regions for Galaxies in the Sloan Digital Sky Survey’s Mapping Nearby Galaxies at Apache Point Observatory Catalog

Negus, James

Graduate Thesis Or Dissertation

The Physics of the Coronal and Broad Line Regions for Galaxies in the Sloan Digital Sky Survey’s Mapping Nearby Galaxies at Apache Point Observatory Catalog Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/br86b501j

Abstract

There is growing evidence that Active Galactic Nucleus (AGN) processes play a vital role in galaxy evolution (e.g., regulating star formation and galactic growth). However, accurate AGN identification is often challenging, as common AGN diagnostics can be confused by contributions from star formation, supernovae, and shocks. However, one promising avenue for identifying the strong ionizing continuum of an AGN are “coronal emission lines” (“CLs”), which are highly ionized species of gas with ionization potentials ≥ 100 eV - above the limit of star formation. Here, I present my graduate work that explores the feasibility of using optical CLs to accurately trace AGNs, using the most extensive optical CL catalogs available, which I assembled using the Sloan Digital Sky Survey’s Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) catalog. In this work, I detect CL emission from [NeV], [FeVII], and/ or [FeX] with ≥ 5σ confidence. I focus particularly on the strength and distribution of the CLs; I also provide the fraction of confirmed CL AGNs to showcase the reliability of using CLs to detect AGNs. I then review the physical CL gas properties (e.g., electron temperatures and densities) to deduce the primary mechanism(s) that generate the CLs. Next, I discuss which CLs are ideal for identifying high luminosity AGNs and investigate the role of dust extinction on optical CL detections. I then search for broad Hα and Hβ emission, which trace the high velocity clouds found near the AGN accretion disk, and assemble one of the largest broad line (BL) MaNGA AGN catalogs. I detect 1,042 unique BL galaxies and find that 109 feature BLs from a companion galaxy, not the target MaNGA galaxy (i.e., “offset AGNs”). I conclude by considering how multi-wavelength CL observations (e.g., X-ray and IR) can help to improve AGN identification.

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