Eccentric Accretion Disks in Active Galactic Nuclei

TL;DR

This paper proposes that eccentric accretion flows around supermassive black holes can explain various observed features of active galactic nuclei, including emission, variability, and the structure of broad-line regions.

Contribution

It introduces a model of eccentric accretion disks that unifies the origins of broad-line regions and X-ray coronae in AGNs, supported by theoretical and observational consistency.

Findings

Eccentric flows generate cascades explaining multiwavelength emission.

Non-axisymmetric temperature structures account for dust sublimation fronts and emission-line components.

Precession-driven variability reproduces observed X-ray power spectra and eruptions.

Abstract

We report that moderately eccentric flows around supermassive black holes (SMBHs), formed via either circumnuclear gas accretion or tidal disruption events, generate eccentricity cascades (from >0.8 to 0.2 outward), explaining multiwavelength emission and variability in active galactic nuclei (AGNs). The flows' non-axisymmetric temperature structure explains non-axisymmetric dust sublimation fronts, distinct broad emission-line components, and their radial motions. The innermost broad-line region (BLR) links to the SMBH vicinity through highly eccentric streams that produce soft X-rays at periapsis. General relativistic precession further compresses these flows, generating a hard X-ray continuum near the SMBH. Precession of the eccentric flow drives optical/X-ray variability, reproducing the observed X-ray power spectral density and occasional X- ray quasi-periodic eruptions. We thus propose eccentric accretion disks as a physical AGN model that unifies the elusive BLRs and X-ray corona. This model will enable detailed anatomy of AGNs and maximize their potential as cosmological standard candles.