Letter to the Editor

VLTI/VINCI observations of the nucleus of NGC 1068 using the adaptive optics system MACAO ^*

¹ European Southern Observatory, Karl Schwarzschild-Str. 2, 85748 Garching, Germany
² LESIA, Observatoire de Paris, 92195 Meudon Cedex, France
³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

Corresponding author: M. Wittkowski, mwittkow@eso.org

Received: 8 March 2004
Accepted: 20 March 2004

Abstract

We present the first near-infrared K-band long-baseline interferometric measurement of the nucleus of the prototype Seyfert 2 Galaxy NGC 1068 with resolution  10 mas obtained with the Very Large Telescope Interferometer (VLTI) and the two 8.2 m diameter Unit Telescopes UT 2 and UT 3. The adaptive optics system MACAO (Multi Application Curvature Adaptive Optics) was employed to deliver wavefront-corrected beams to the K-band commissioning instrument VINCI. A squared visibility amplitude of 16.3 ± 4.3% was measured for NGC 1068 at a sky-projected baseline length of 45.8 m and azimuth angle 44.9 deg. This value corresponds to a FWHM of the K-band intensity distribution of 5.0 ± 0.5 mas (0.4 ± 0.04 pc at the distance of NGC 1068) if it consists of a single Gaussian component. Taking into account K-band speckle interferometry observations (Wittkowski et al. [CITE]; Weinberger et al. [CITE]; Weigelt et al. [CITE]), we favor a multi-component model for the intensity distribution where a part of the flux originates from scales clearly smaller than ~5 mas (0.4 pc), and another part of the flux from larger scales. The K-band emission from the small (5 mas) scales might arise from substructure of the dusty nuclear torus, or directly from the central accretion flow viewed through only moderate extinction.