Three-dimensional radiative transfer modeling of AGN dusty tori as a clumpy two-phase medium

TL;DR

This paper models AGN dusty tori as a 3D two-phase medium with clumps and interclump dust, analyzing how dust distribution affects infrared emission features and potentially explains observed near-infrared deficits.

Contribution

It introduces a novel 3D two-phase medium model for AGN dusty tori, incorporating complex clumpy structures and comparing their spectral energy distributions with smooth dust models.

Findings

Dust distribution impacts infrared SED shape.

Two-phase models can suppress the 10 micron silicate feature.

Two-phase dust distribution may explain near-infrared emission deficits.

Abstract

We investigate the emission of active galactic nuclei (AGN) dusty tori in the infrared domain. Following theoretical predictions coming from hydrodynamical simulations, we model the dusty torus as a 3D two-phase medium with high-density clumps and low-density medium filling the space between the clumps. Spectral energy distributions (SED) and images of the torus at different wavelengths are obtained using 3D Monte Carlo radiative transfer code SKIRT. Our approach of generating clumpy structure allows us to model tori with single clumps, complex structures of merged clumps or interconnected sponge-like structure. A corresponding set of clumps-only models and models with smooth dust distribution is calculated for comparison. We found that dust distribution, optical depth, clump size and their actual arrangement in the innermost region, all have an impact on the shape of near- and mid-infrared SED. The 10 micron silicate feature can be suppressed for some parameters, but models with smooth dust distribution are also able to produce a wide range of the silicate feature strength. Finally, we find that having the dust distributed in a two-phase medium, might offer a natural solution to the lack of emission in the near-infrared, compared to observed data, which affects clumpy models currently available in the literature.