Anne Poncelet, Guy Perrin, Helene Sol, Coralie Doucet, and Pierre-Olivier Lagage
MID-INFRARED INTERFEROMETRIC OBSERVATIONS OF THE NUCLEUS OF NGC 1068 (Poster)

MID-INFRARED INTERFEROMETRIC OBSERVATIONS OF THE NUCLEUS OF NGC 1068

Anne Poncelet(1,2), Guy Perrin(2), Helene Sol(1), Coralie Doucet(3), and Pierre-Olivier Lagage(3)
(1)LUTH, Observatoire de Paris, 92195 Meudon Cedex
(2)LESIA, Observatoire de Paris, 92195 Meudon Cedex
(3)DSM/DAPNIA/Service d'Astrophysique, CEA Saclay, F-91191 Gif-sur-Yvette

NGC 1068 is one of the brightest and nearest Seyfert 2 galaxy, therefore it is unique for the study of the active galactic nucleus (AGN) it harbors. The MIR contribution of the AGN is thought to originate from the reradiation by dust of the UV emission coming from the central engine.

Here we present a new analysis of the first mid-infrared (MIR) $N$-band high-resolution interferometric observations of this AGN, obtained with MIDI (Mid-InfraReD Interferometer) of the VLTI. The resolution of 10 mas, never achieved in this band with an other technique, should allow from now on the MIR observations of the distribution of dust in the inner part of bright AGNs.

Both visibility measurements and MIDI spectrum obtained on NGC 1068 are well reproduced with a simple radiative transfer model with two concentric spherical components. A detailed $\chi^2$ analysis led to angular sizes and temperatures of respectively $\sim$ 35 and 83 mas, and $\sim$ 361 K and 226 K for the two components. Some other evidences strongly support such low temperatures. This modeling also provides the variation of optical depth as a function of wavelength for the extended component across the $N$-band pointing towards the presence of amorphous silicate grains. This provides the confirmation that MIDI actually carried out the first direct observations of the distribution of dust around the compact core of an AGN.

Besides, configurations of telescopes at VLTI do not allow to reach low spatial frequency. These points are however of first importance in order to put strong additional constrains on the modeling. Therefore, we used VISIR (the VLT Imager Spectrometer in the Infra-Red) images of the core of NGC 1068 obtained in january 2005 at 12.8 $\mu$m to derived visibility points from 0 to 8.2 m of baseline. Visibilities then derived show interesting features that will have to be taken into account in the modeling of interferometric data obtained with MIDI. These images are also important to make the link between the dust distribution around the nucleus and larger scales, a further step that is mandatory to get a global understanding of the sources of MIR emission in AGNs.