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arXiv · 1611.05165

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

Adam D. Thomas·Brent A. Groves·Ralph S. Sutherland·Michael A. Dopita·Chichuan Jin·Lisa J. Kewley
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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.

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Adam D. Thomas, Brent A. Groves, Ralph S. Sutherland, Michael A. Dopita, Chichuan Jin, Lisa J. Kewley. 2016-11-16. A physically-based model of the ionizing radiation from active galaxies for photoionization modeling. https://doi.org/10.3847/1538-4357%2F833%2F2%2F266

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