Ya. B. Zeldovich All-Moscow Seminar of Astrophysicists

A torus of molecular gas and dust is one of the key components of unified schemes of active galactic nuclei (AGN): it provides the material for accretion onto the supermassive black hole and is held responsible for the orientation-dependent obscuration of the central engine. I will present the results and current status of infrared interferometry of these dust distributions in AGN in the infrared. Our observations have shown that both the hot inner rim as well as the warm body of the torus scale with the square root of the luminosity of the AGN and we find that the warm dust in the body of the torus is located at about 30 times larger radii than the inner hot rim. The large scatter about the size-luminosity relation in the mid-infrared hints at significant differences between the tori in individual galaxies, questioning the current picture of the same dusty doughnut in all AGN. I will especially focus on the results for the Circinus galaxy, the closest Seyfert 2 galaxy. It is the object studied best by mid-infrared interferometry. Its nucleus is well resolved, so that a precise determination of the properties of the individual dust components and of the profile of the radial dust distribution can be obtained. The recent detection of a strong outburst in this AGN makes it even more interesting. Measurements of the light curve of this event in the infrared will allow to study the dust distribution using reverberation techniques.