Unified schemes of active galactic nuclei ( AGN ) require an obscuring dusty torus around the central source , giving rise to Seyfert 1 line spectrum for pole-on viewing and Seyfert 2 characteristics in edge-on sources .
Although the observed IR is in broad agreement with this scheme , the behavior of the 10 µm silicate feature and the width of the far-IR emission peak remained serious problems in all previous modeling efforts .
We show that these problems find a natural explanation if the dust is contained in \sim 5–10 clouds along radial rays through the torus .
The spectral energy distributions ( SED ) of both type 1 and type 2 sources are properly reproduced from different viewpoints of the same object if the optical depth at visual of each cloud obeys \tau _ { V } \gtrsim 60 and the clouds ’ mean free path increases roughly in proportion to radial distance .