A Physically Based Model of the Ionizing Radiation From Active Galaxies for Photoionization Modeling

Childress, M.; Groves, Brent; Sutherland, Ralph S.; Dopita, Michael A.; Kewley, Lisa J.; Jin, Chichuan

doi:10.3847/1538-4357/833/2/266

Cited by 36 publications

(40 citation statements)

References 43 publications

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“…The high energy cutoff is set at 100 keV as in most fitting packages (e.g. OPTXAGN -standard AGN shape in CLOUDY, Done et al 2012;Thomas et al 2016). Observational data show a dispersion in this quantity from about 50 keV to over 200 keV but the measurements are still rare (for a compilation of measurements from NuSTAR, see Fabian et al 2015).…”

Section: Incident Continuummentioning

confidence: 99%

Modeling of the Quasar Main Sequence in the Optical Plane

Panda

Czerny

Adhikari

et al. 2018

ApJ

114

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The concept of the quasar main sequence is very attractive since it stresses correlations between various parameters and implies the underlying simplicity. In the optical plane defined by the width of the Hβ line and the ratio of the equivalent width of the Fe II to Hβ observed objects form a characteristic pattern. In this paper, we use a physically motivated model to explain the distribution of quasars in the optical plane. Continuum is modelled as an accretion disk with a hard X-ray power law uniquely tight to the disk at the basis of observational scaling, and the Broad Line Region distance is determined also from observational scaling. We perform the computations of the FeII and Hβ line production with the code CLOUDY. We have only six free parameters for an individual source: maximum temperature of the accretion disk, Eddington ratio, cloud density, cloud column density, microturbulence, and iron abundance, and only the last four remain as global parameters in our modelling of the whole sequence. Our theoretically computed points cover well the optical plane part populated with the observed quasars, particularly if we allow for super-Solar abundance of heavy elements. Explanation of the exceptionally strong Fe II emitter requires a stronger contribution from the dark sides of the clouds. Analyzing the way how our model covers the optical plane we conclude that there is no single simple driver behind the sequence, as neither the Eddington ratio nor broad band spectrum shape plays the dominant role. Also, the role of the viewing angle in providing the dispersion of the quasar main sequence is apparently not as strong as expected.

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Section: Incident Continuummentioning

confidence: 99%

Modeling of the Quasar Main Sequence in the Optical Plane

Panda

Czerny

Adhikari

et al. 2018

ApJ

114

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“…The Seyfert model components use an ionizing spectrum from Thomas et al (2016) that parameterizes the energy of the ionizing accretion disk emission by its peak energy, E peak . In Paper 1 we concluded that values of E peak in the range 40 − 50 eV result in plausible distributions of f NLR measurements.…”

Section: Model Datamentioning

confidence: 99%

The Mass–Metallicity Relation of Local Active Galaxies

Childress

Kewley

Dopita

et al. 2019

ApJ

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We systematically measure the gas-phase metallicities and the mass-metallicity relation of a large sample of local active galaxies for the first time. Observed emission-line fluxes from the Sloan Digital Sky Survey (SDSS) are compared to a four-dimensional grid of photoionization models using the Bayesian parameter estimation code NebulaBayes. For the first time we take into account arbitrary mixing between H II region and narrow-line region (NLR) emission, and the models are also varied with metallicity, ionization parameter in the NLR, and the gas pressure. The active galactic nucleus (AGN) oxygen abundance is found to increase by ∆O/H ∼ 0.1 dex as a function of host galaxy stellar mass over the range 10.1 < log M * /M < 11.3. We also measure the metallicity and ionization parameter of 231000 star-forming galaxies for comparison with the sample of 7670 Seyfert 2 galaxies. A systematic offset in oxygen abundance of 0.09 dex is observed between the mass-metallicity relations of the star-forming and active galaxies. We investigate potential causes of the offset, including sample selection and the treatment in the models of diffuse ionized gas, pressure, and ionization parameter. We cannot identify the major cause(s), but suspect contributions due to deficiencies in modeling the ionizing spectra and the treatment of dust physics. Optical diagnostic diagrams are presented with the star-forming and Seyfert data colored by the inferred oxygen abundance, ionization parameter and gas pressure, clearly illustrating the trends in these quantities.

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“…The NLR grid uses an oxaf ionizing spectrum (Thomas et al 2016), which has three parameters: the energy of the peak of the accretion disk emission E peak , the photon index of the inverse Compton scattered power-law tail Γ, and the proportion of the total flux that goes into the non-thermal tail, p NT . The two parameters Γ and p NT are somewhat anti-correlated, because decreasing the hardness of the power-law tail by increasing Γ has a similar effect (at the most relevant EUV energies and at fixed p NT ) as scaling up the power-law tail with p NT .…”

Section: Narrow Line Region Model Gridmentioning

confidence: 99%

Interrogating Seyferts with NebulaBayes: Spatially Probing the Narrow-line Region Radiation Fields and Chemical Abundances

Childress

Dopita

Kewley

et al. 2018

ApJ

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NebulaBayes is a new Bayesian code that implements a general method of comparing observed emission-line fluxes to photoionization model grids. The code enables us to extract robust, spatially resolved measurements of abundances in the extended narrow line regions (ENLRs) produced by Active Galactic Nuclei (AGN). We observe near-constant ionization parameters but steeply radially-declining pressures, which together imply that radiation pressure regulates the ENLR density structure on large scales. Our sample includes four 'pure Seyfert' galaxies from the S7 survey that have extensive ENLRs. NGC 2992 shows steep metallicity gradients from the nucleus into the ionization cones. An inverse metallicity gradient is observed in ESO 138-G01, which we attribute to a recent gas inflow or minor merger. A uniformly high metallicity and hard ionizing continuum are inferred across the ENLR of Mrk 573. Our analysis of IC 5063 is likely affected by contamination from shock excitation, which appears to soften the inferred ionizing spectrum. The peak of the ionizing continuum E peak is determined by the nuclear spectrum and the absorbing column between the nucleus and the ionized nebula. We cannot separate variation in this intrinsic E peak from the effects of shock or H II region contamination, but E peak measurements nevertheless give insights into ENLR excitation. We demonstrate the general applicability of NebulaBayes by analyzing a nuclear spectrum from the non-active galaxy NGC 4691 using a H II region grid. The NLR and H II region model grids are provided with NebulaBayes for use by the astronomical community.

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A Physically Based Model of the Ionizing Radiation From Active Galaxies for Photoionization Modeling

Cited by 36 publications

References 43 publications

Modeling of the Quasar Main Sequence in the Optical Plane

Modeling of the Quasar Main Sequence in the Optical Plane

The Mass–Metallicity Relation of Local Active Galaxies

Interrogating Seyferts with NebulaBayes: Spatially Probing the Narrow-line Region Radiation Fields and Chemical Abundances

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