Parsec-scale Obscuring Accretion Disk with Large-Scale Magnetic Field in AGNs

Dorodnitsyn, A.; Kallman, T. R.

doi:10.3847/1538-4357/aa7264

Cited by 23 publications

(19 citation statements)

References 89 publications

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“…In the last decade, several theoretical models based on radiative hydro-dynamic simulations have been developed, which attempt to explain the origin and stability of the obscurer. The high covering is achieved either by bringing in host galaxy scale gas from random orientations (e.g., Hopkins et al 2012;Gaspari et al 2015), by black hole and star formation feedback processes in the inner hundred parsec (e.g., Wada 2012;Schartmann et al 2018), or by the black hole accretion system in isolation (e.g., Chan & Krolik 2016;Dorodnitsyn & Kallman 2017;Williamson et al 2019;Mościbrodzka & Proga 2013). However, such models have not yet been tested against X-ray reflection spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Physically motivated X-ray obscurer models

Buchner

Brightman

Baloković

et al. 2021

A&A

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Context. The nuclear obscurer of active galactic nuclei (AGN) is poorly understood in terms of its origin, geometry, and dynamics. Aims. We investigate whether physically motivated geometries emerging from hydro-radiative simulations can be differentiated with X-ray reflection spectroscopy. Methods. For two new geometries, the radiative fountain model and a warped disk, we release spectral models produced with the ray tracing code XARS. We contrast these models with spectra of three nearby AGN taken by NuSTAR and Swift/BAT. Results. Along heavily obscured sightlines, the models present different 4−20 keV continuum spectra. These can be differentiated by current observations. Spectral fits of the Circinus Galaxy favour the warped disk model over the radiative fountain, and clumpy or smooth torus models. Conclusions. The necessary reflector (NH ≥ 1025 cm2) suggests a hidden population of heavily Compton-thick AGN amongst local galaxies. X-ray reflection spectroscopy is a promising pathway to understand the nuclear obscurer in AGN.

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Section: Introductionmentioning

confidence: 99%

Physically motivated X-ray obscurer models

Buchner

Brightman

Baloković

et al. 2021

A&A

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“…We rely on magnetohydrodynamical (MHD) simulations to assume the overall structure of the magnetic field in the torus. Recent MHD simulations by Dorodnitsyn & Kallman (2017) assume an initial poloidal field in the torus. This poloidal field quickly and efficiently generates a toroidal field to maintain a long-lived torus due to differential rotation.…”

Section: Model Definitionmentioning

confidence: 99%

ALMA Polarimetry Measures Magnetically Aligned Dust Grains in the Torus of NGC 1068

López-Rodríguez

Alonso‐Herrero

García‐Burillo

et al. 2020

ApJ

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The obscuring structure surrounding active galactic nuclei (AGN) can be explained as a dust and gas flow cycle that fundamentally connects the AGN with their host galaxies. This structure is believed to be associated with dusty winds driven by radiation pressure. However, the role of magnetic fields, which are invoked in almost all models for accretion onto a supermassive black hole and outflows, is not thoroughly studied. Here we report the first detection of polarized thermal emission by means of magnetically aligned dust grains in the dusty torus of NGC 1068 using ALMA Cycle 4 polarimetric dust continuum observations (0. 07, 4.2 pc; 348.5 GHz, 860 µm). The polarized torus has an asymmetric variation across the equatorial axis with a peak polarization of 3.7 ± 0.5% and position angle of 109 ± 2 • (B-vector) at ∼ 8 pc east from the core. We compute synthetic polarimetric observations of magnetically aligned dust grains assuming a toroidal magnetic field and homogeneous grain alignment. We conclude that the measured 860 µm continuum polarization arises from magnetically aligned dust grains in an optically thin region of the torus. The asymmetric polarization across the equatorial axis of the torus arises from 1) an inhomogeneous optical depth, and 2) a variation of the velocity dispersion, i.e. variation of the magnetic field turbulence at sub-pc scales, from the eastern to the western region of the torus. These observations and modeling constrain the torus properties beyond spectral energy distribution results. This study strongly supports that magnetic fields up to a few pc contribute to the accretion flow onto the active nuclei.

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“…The MHD formulation produces a robust magnetorotational instability (MRI) which leads to inflow from dense regions near the midplane of the distribution, while evaporative flow occurs from moderate and high latitudes. Details of these dynamics are described in detail in Dorodnitsyn & Kallman (2017). Models are evolved for ∼60-80 dynamical times, where the dynamical time is given by t dyn = R 3 /2GM = 10 11 R 3/2 pc M 1/2 7 s and R pc is the fiducial radius in pc and M 7 is the mass of the black hole in 10 7 M .…”

Section: Dynamical Modelsmentioning

confidence: 99%

“…We have constructed hydrodynamic models for warm absorber gas using assumptions based on these current ideas: That the warm absorber gas represents an ionized component of the gas responsible for AGN unification and obscuration, with the ionization supplied by X-ray illumination from close to the black hole horizon, and that the outflow arises from thermal evaporation supplemented by radiation pressure (Dorodnitsyn et al 2008a,b;Dorodnitsyn et al 2016;Dorodnitsyn & Kallman 2017). These models incorporate the physics of X-ray heating and radiative cooling, radiative driving, toroidal geometry, and attenuation of the radiation from the central black hole.…”

Section: Introductionmentioning

confidence: 99%

Warm Absorber Diagnostics of AGN Dynamics

Kallman

Dorodnitsyn

2019

ApJ

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Warm absorbers and related phenomena are one of the observable manifestations of outflows or winds from active galactic nuclei (AGN). Warm absorbers are common in low luminosity AGN, they have been extensively studied observationally, and are well described by simple phenomenological models.However, major open questions remain: What is the driving mechanism? What is the density and geometrical distribution? How much associated fully ionized gas is there? What is the relation to the quasi-relativistic 'ultrafast outflows' (UFOs)? In this paper we present synthetic spectra for the observable properties of warm absorber flows and associated quantities. We use ab initio dynamical models, i.e. solutions of the equations of motion for gas in finite difference form. The models employ various plausible assumptions for the origin of the warm absorber gas and the physical mechanisms affecting its motion. The synthetic spectra are presented as an observational test of these models. In this way we explore various scenarios for warm absorber dynamics. We show that observed spectra place certain requirements on the geometrical distribution of the warm absorber gas, and that not all dynamical scenarios are equally successful at producing spectra similar to what is observed. arXiv:1906.05705v2 [astro-ph.HE]

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Parsec-scale Obscuring Accretion Disk with Large-Scale Magnetic Field in AGNs

Cited by 23 publications

References 89 publications

Physically motivated X-ray obscurer models

Physically motivated X-ray obscurer models

ALMA Polarimetry Measures Magnetically Aligned Dust Grains in the Torus of NGC 1068

Warm Absorber Diagnostics of AGN Dynamics

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