Authors
                Prof.
            
                        Nancy Levenson
            
  Date and time
                                    31 Mar 2009 - 00:00 Europe/London
                            Address
                                    Aula
Talk language
                                    English
                            Serie number
                                    0
                            Description
                                    Dust reprocesses the intrinsic radiation of active galactic nuclei (AGN) to emerge at longer wavelengths.  The mid-infrared (MIR) luminosity depends broadly on luminosity of the central engine, but in detail it also depends on the dust distribution.  Spectroscopic differences, both at optical and IR wavelengths, indicate that the immediate dusty surroundings of the AGN are not spherically symmetric, as in standard unified AGN schemes, but the small-scale MIR emission due to the surrounding "torus" is isotropic, where absorption-corrected X-ray luminosity serves as a proxy for the intrinsic AGN luminosity.  A clumpy local environment can account for these observations.  Moreover, the inhomogeneous torus models also accommodate several unusual observations, such as MIR silicate emission from obscured AGN.