Dusty torus formation by anisotropic radiative pressure feedback of active galactic nuclei

TL;DR

This paper presents a model where anisotropic radiative pressure from accretion disks influences dust distribution, explaining observed AGN obscuration patterns and proposing a sequence for dusty torus evolution.

Contribution

It introduces a novel model of anisotropic radiative feedback shaping dusty torus formation and evolution in AGNs, accounting for observational trends and predicting new AGN types.

Findings

Anisotropic radiation causes dust to be blown out face-on, surviving edge-on.

The model reproduces the decreasing fraction of type 2 AGNs with luminosity.

Predicts bright AGNs with dusty tori but lacking broad line regions.

Abstract

The feedback by active galactic nuclei (AGNs) is significant for the formation and evolution of galaxies. It has been realized that the radiative pressure feedback could be an efficient mechanism due to the existence of dust. In this Letter, we discuss the effect of anisotropic radiative pressure, which is inevitable if the UV/optical emission arises from an accretion disk. The distribution of dusty gas should be also anisotropic due to the influence of the anisotropic disk radiation, i.e. the dust in the face-on direction of an accretion disk can be blown out relatively more easily, whereas the dust can survive in the edge-on direction. This result can explain the presence of some obscured AGNs with high Eddington ratios and can also quantitatively reproduce the observed decreasing fraction of type 2 AGNs with increasing luminosity. A sequence of AGN formation and evolution is also proposed, within the context of the formation, evolution and exhaustion of the dusty torus. Our model predicts the existence of bright AGNs with dusty tori, but without broad line regions. Finally we discuss the implications of the anisotropic radiation for the calculations of luminosity functions and radiation efficiencies of AGNs.