Dusty Winds in Active Galactic Nuclei: Reconciling Observations with Models

Abstract

This Letter presents a revised radiative transfer model for the infrared (IR) emission of active galactic nuclei (AGNs). While current models assume that the IR is emitted from a dusty torus in the equatorial plane of the AGNs, spatially resolved observations indicate that the majority of the IR emission from ≲100 pc in many AGNs originates from the polar region, contradicting classical torus models. The new model CAT3D-WIND builds upon the suggestion that the dusty gas around the AGNs consists of an inflowing disk and an outflowing wind. Here, it is demonstrated that (1) such disk+wind models cover overall a similar parameter range of observed spectral features in the IR as classical clumpy torus models, e.g., the silicate feature strengths and mid-IR spectral slopes, (2) they reproduce the 3–5 μ m bump observed in many type 1 AGNs unlike torus models, and (3) they are able to explain polar emission features seen in IR interferometry, even for type 1 AGNs at relatively low inclination, as demonstrated for NGC3783. These characteristics make it possible to reconcile radiative transfer models with observations and provide further evidence of a two-component parsec-scale dusty medium around AGNs: the disk gives rise to the 3–5 μ m near-IR component, while the wind produces the mid-IR emission. The model SEDs will be made available for download.