Optical and JWST Mid-IR Emission Line Diagnostics for Simultaneous IMBH and Stellar Excitation in z~0 Dwarf Galaxies

Abstract

Current observational facilities have yet to conclusively detect $10^3-10^4{M}_{\odot }$ intermediate mass black holes (IMBHs) that fill in the evolutionary gap between early universe seed black holes and $z\sim 0$ supermassive black holes. Dwarf galaxies present an opportunity to reveal active IMBHs amidst persistent star formation. We introduce photoionization simulations tailored to address key physical uncertainties: coincident vs. non-coincident mixing of IMBH and starlight excitation, open vs. closed surrounding gas cloud geometries, and different AGN SED shapes. We examine possible AGN emission line diagnostics in the optical and mid-IR, and find that the diagnostics are often degenerate with respect to the investigated physical uncertainties. In spite of these setbacks, and in contrast to recent work, we are able to show that [O III]/H$\beta$ typically remains bright for dwarf AGN powered by IMBHs down to $10^3{M}_{\odot }$. Dwarf AGN are predicted to have inconsistent star-forming and Seyfert/LINER classifications using the most common optical diagnostics. In the mid-IR, [O IV] 25.9$\mu$m and [Ar II] 6.98$\mu$m are less sensitive to physical uncertainties than are optical diagnostics. Based on these emission lines, we provide several mid-IR emission line diagnostic diagrams with demarcations for separating starbursts and AGN with varying levels of activity. The diagrams are valid over a wide range of ionization parameters and metallicities out to $z\sim 0.1$, so will prove useful for future JWST observations of local dwarf AGN in the search for IMBHs. We make our photoionization simulation suite freely available.

24 pages, 13 figures, accepted to ApJ

References in corpus (30)

• The Host Galaxies and Classification of Active Galactic Nuclei
• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• Present-day cosmic abundances. A comprehensive study of nearby early B-type stars and implications for stellar and Galactic evolution and interstellar dust models
• Modelling the nebular emission from primeval to present-day star-forming galaxies
• H3+ in Diffuse Interstellar Clouds: a Tracer for the Cosmic-Ray Ionization Rate
• The elemental composition of the Sun II. The iron group elements Sc to Ni
• The elemental composition of the Sun I. The intermediate mass elements Na to Ca
• The Herschel Dwarf Galaxy Survey: I. Properties of the low-metallicity ISM from PACS spectroscopy
• Galaxies with Wolf-Rayet signatures in the low-redshift Universe - A survey using the Sloan Digital Sky Survey
• The elemental composition of the Sun III. The heavy elements Cu to Th
• A 0.8-2.4 microns spectral atlas of Active Galactic Nuclei
• Modeling Sulfur Depletion in Interstellar Clouds
• Mid-Infrared Spectral Diagnostics of Nuclear and Extra-Nuclear Regions in Nearby Galaxies
• The Herschel Dwarf Galaxy Survey: II. Physical conditions, origin of [CII] emission, and porosity of the multiphase low-metallicity ISM
• Excitation properties of galaxies with the highest [OIII]/[OII] ratios: No evidence for massive escape of ionizing photons
• The Limitations of Optical Spectroscopic Diagnostics in Identifying AGNs in the Low Mass Regime
• Ionization correction factors and dust depletion patterns in giant HII regions
• Sensitivity of PDR Calculations to Microphysical Details
• The Abundance of Interstellar Fluorine and Its Implications
• Improved Fe II emission line models for AGN using new atomic datasets
• METAL: The Metal Evolution, Transport, and Abundance in the Large Magellanic Cloud Hubble program. I. Overview and Initial Results
• CLOUDY view of the warm corona
• The initial gas-phase sulfur abundance in the Orion Molecular Cloud from sulfur radio recombination lines
• Comparison of Theoretical Starburst Photoionisation Models for Optical Diagnostics
• Disentangling the physical parameters of gaseous nebulae and galaxies
• Stromlo Stellar Tracks: non-solar scaled abundances for massive stars
• Theoretical Modeling of Emission-Line galaxies: New Classification Parameters for Mid-Infrared and Optical Spectroscopy
• Do stellar-mass and super-massive black holes have similar dining habits?
• Addressing the [O III]/H\b{eta} Offset of Dwarf Galaxies in the RESOLVE Survey
• An Atlas of Star-Forming Galaxy Equivalent Widths

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• MIRACLE II: Unveiling the multi-phase gas interplay in the circumnuclear region of NGC 1365 via multi-cloud modeling
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• Recovering the properties of the interstellar medium through integrated spectroscopy: application to the z~0 ECO volume-limited star-forming galaxy sample