Four quadrant phase mask K-band coronagraphy of NGC 1068 with NAOS-CONICA at VLT

¹ LESIA, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon, France e-mail: damien.gratadour@obspm.fr
² DOTA-ONERA, Avenue de la division Leclerc, 92322 Chatillon, France
³ ESO, Karl-Schwarzschild Strasse 2, 85748 Garching bei München, Germany

Received: 10 August 2004
Accepted: 1 September 2004

Abstract

We observed the nucleus of NGC 1068 at Ks with NAOS-CONICA on the VLT, using the new four quadrant phase mask coronagraph that we recently developed. As the K-band emission is dominated by an intense compact central source, previous K-band adaptive optics images were severely affected by the limited exposure time and by scattered light in the immediate vicinity of the source. Thanks to the use of this new type of coronagraph coupled to adaptive optics, the complex dust structure near the central core is becoming observable at a resolution of 0.07´´. North of the nucleus, an elongated, bending structure, and a series of four elongated and well aligned knots, superposable on the same pattern previously observed by us at 3.8 and 4.8 μm are well identified. This agrees with our first interpretation that, given the direction they align in, these knots may trace shocks induced in the ISM by the passage of the jet, very close to its origin. Moreover, precise relative photometry supports our interpretation of very small dust grains transiently heated by UV photons of the central source. To the South we detect a new group of filamentary structures, distributed in a cone at about 150 pc from the core. They might trace the redshifted southern narrow line region, seen through the dust. Finally, on larger scale (within a radius of three hundred pc) the source has an overall biconical shape whose angle matches well with the bicone observed in the UV-visible.