A physically-based model of the ionizing radiation from active galaxies for photoionization modeling

Abstract

We present a simplified model of Active Galactic Nucleus (AGN) continuum emission designed for photoionization modeling. The new model {\sc oxaf} reproduces the diversity of spectral shapes that arise in physically-based models. We identify and explain degeneracies in the effects of AGN parameters on model spectral shapes, with a focus on the complete degeneracy between the black hole mass and AGN luminosity. Our re-parametrized model {\sc oxaf} removes these degeneracies and accepts three parameters which directly describe the output spectral shape: the energy of the peak of the accretion disk emission $E_{\mathrm{peak}}$, the photon power-law index of the non-thermal emission $\Gamma$, and the proportion of the total flux which is emitted in the non-thermal component $p_{\mathrm{NT}}$. The parameter $E_{\mathrm{peak}}$ is presented as a function of the black hole mass, AGN luminosity, and `coronal radius' of the {\sc optxagnf} model upon which {\sc oxaf} is based. We show that the soft X-ray excess does not significantly affect photoionization modeling predictions of strong emission lines in Seyfert narrow-line regions. Despite its simplicity, {\sc oxaf} accounts for opacity effects where the accretion disk is ionized because it inherits the `color correction' of {\sc optxagnf}. We use a grid of {\sc mappings} photoionization models with {\sc oxaf} ionizing spectra to demonstrate how predicted emission-line ratios on standard optical diagnostic diagrams are sensitive to each of the three {\sc oxaf} parameters. The {\sc oxaf} code is publicly available in the Astrophysics Source Code Library.

14 pages, 9 figures, 1 table. Accepted for publication in ApJ

References in corpus (5)

• The Host Galaxies and Classification of Active Galactic Nuclei
• Emission-line Diagnostics of Low Metallicity AGN
• Testing Accretion Disk Theory in Black Hole X-ray Binaries
• Probing the Physics of Narrow Line Regions in Active Galaxies II: The Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7)
• Probing the physics of narrow-line regions of Seyfert galaxies I: The case of NGC 5427

Cited by in corpus (10)

• Understanding Galaxy Evolution through Emission Lines
• EPOCHS VII: Discovery of high redshift ($6.5<z<12$) AGN candidates in JWST ERO and PEARLS data
• Probing the Physics of Narrow Line Regions in Active Galaxies IV: Full data release of The Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7)
• GASP XIX: AGN and their outflows at the center of jellyfish galaxies
• The mass-metallicity relation of local active galaxies
• Inspiraling streams of enriched gas observed around a massive galaxy 11 billion years ago
• The mass-metallicity and fundamental metallicity relations in non-AGN and AGN-host galaxies
• Multi-line assessment of narrow-line regions in $z\sim$ 3 radio galaxies
• An interacting galaxy pair at the origin of a light echo
• The Kinematics and Ionization Structure of the Extended Emission Line Region of QSO E1821+643