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Astron. Astrophys. 336, 823-828 (1998)


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

O. Marco 1 and D. Alloin 2

1 Observatoire de Paris, DESPA (URA CNRS 264), F-92195 Meudon, France
2 Service d'Astrophysique, CE Saclay (URA CNRS 2052), F-91191 Gif-sur-Yvette, France

Received 8 July 1997 / Accepted 27 March 1998

Abstract

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[FORMULA]55 pc) embedded in an extended emission component. Not to mention the ring of star formation, known to be present at r[FORMULA] 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 3.8µm flux across the 1.4"[FORMULA]1.4" central region arises from the unresolved core. The hot and warm dust grain density in the extended component follows an [FORMULA] law, and the dust temperature ranges from 900 K (r[FORMULA] 130 pc) to [FORMULA] 300 K (r[FORMULA] 400 pc). The mass of hot (T=900 K) dust within a r[FORMULA] 200 pc central region is [FORMULA] 0.05 [FORMULA] and it accounts for 36% of the 2.2µm 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.

Key words: galaxies: individual: NGC 7469 – galaxies: Seyfert – galaxies: nuclei – infrared: galaxies

* Based on observations collected at the European Southern Observatory, La Silla, Chile.

Send offprint requests to: O. Marco

© European Southern Observatory (ESO) 1998

Online publication: July 27, 1998

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