Dust Emission from Active Galactic Nuclei

Unified schemes of active galactic nuclei (AGN) require an obscuring dustytorus around the central source, giving rise to Seyfert 1 line spectrum forpole-on viewing and Seyfert 2 characteristics in edge-on sources. Although theobserved IR is in broad agreement with this scheme, the behavior of the 10micron silicate feature and the width of the far-IR emission peak remainedserious problems in all previous modeling efforts. We show that these problemsfind a natural explanation if the dust is contained in about 5-10 clouds alongradial rays through the torus. The spectral energy distributions (SED) of bothtype 1 and type 2 sources are properly reproduced from different viewpoints ofthe same object if the visual optical depth of each cloud is larger than about60 and the clouds' mean free path increases roughly in proportion to radialdistance.Comment: 11 pages, submitted to ApJ Letter