Active galactic nuclei (AGNs) are among the most spectacular objects in the sky. They display many energetic phenomena – relativistic jets, broad emission lines, X-rays, radio lobes – originating from accretion onto a supermassive black hole. The varying importance of these phenomena results in a complex classification of AGNs into quasars, radio galaxies, Seyfert galaxies etc. Much of this diversity seems caused by orientation effects: from certain viewpoints, circumnuclear dust clouds block the view of the central accretion disk and jets. The dust re-radiates the absorbed energy at infrared wavelengths. The universality of this model, and the dust geometry are still controversial; even the largest telescopes have not resolved the dust structures.
Recently, the new MID-infrared Interferometer (MIDI) was coupled to the European Southern Observatory's (ESO) Very Large Telescope Interferometer (VLTI). The great light collecting power of the two 8.2 meter diameter telescopes used in the VLTI allowed for the first time the detection of an interferometric optical/infrared spectrum from NGC 1068, an extra-galactic object. The spatial resolution of the two-telescope array, 30 milli-arcsec, corresponds to 2.5 parsec at the galaxy and allowed to resolve the obscuring dust structure of an AGN, while the spectral information obtained by MIDI in the astronomical infrared N-band (8-13.5 micron) allowed for an estimation of the dust composition based on the absorption lines of typical dust minerals in this band.
At the beginning of November 2003 a new and more extended data set has been obtained. Also at the 10m Keck telescope interferometric observations have been obtained. In addition, a number of other techniques have come to bear interesting results. These include adaptive optics measurements and X-ray and radio measurements.
This workshop will bring together the team that is carrying out the interferometric observations, astronomers that are in the process of detailed modeling the observed phenomenon and astronomers that are carrying out observations of AGN with other techniques. The program will contain a number of elements, including:
· an overview of the recent results of multiwavelength observations of nearby AGN.
· a detailed discussion of the VLTI data obtained together with a comparison of the various reduction methods
· a first confrontation of the various models with the data obtained last year.
The organisation of this workshop will be carried out by Huub Röttgering, Walter Jaffe (Leiden), Klaus Meisenheimer (Max Planck Institute, Heidelberg), Helene Sol (Meudon, Paris), Fabien Malbet (Grenoble).