Hot dust in the active nucleus of NGC 7469 probed by adaptive optics observations ?

The use of adaptive optics has allowed to reach in the infrared an angular resolution around 0.35 " , allowing to study the temperature, mass and distribution of the dust component within the 400 pc radius central region of NGC 7469. We have obtained L and L' band images which show an unresolved core (r<55 pc) embedded in an extended emission component. Not to mention the ring of star formation, known to be present at r∼1.5 " , which cannot be studied from this data set because of its quite low surface brightness and will not be discussed here. We find that about 55% of the 3.5 and 3.8 µm flux across the 1.4 " ×1.4 " central region arises from the unresolved core. The hot and warm dust grain density in the extended component follows an r −1.5 law, and the dust temperature ranges from 900 K (r∼130 pc) to ∼300 K (r∼400 pc). The mass of hot (T =900 K) dust within a r∼200 pc central region is ∼0.05 M and it accounts for 36% of the 2.2 µm emission in this region. These results are in good agreement with a composite model of active nucleus including a parsec scale dusty torus surrounded by an extended hot dust region located in the NLR and heated by the central engine.