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

Abstract

We present the first near-infrared K-band long-baseline interferometric measurement of the prototype Seyfert 2 galaxy NGC 1068 with resolution lambda/B \~ 10 mas obtained with the Very Large Telescope Interferometer (VLTI) and the two 8.2m Unit Telescopes UT2 and UT3. The adaptive optics system MACAO 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. 1998; Weinberger et al. 1999; Weigelt et al. 2004), we favor a multi-component model for the intensity distribution where a part of the flux originates from scales clearly smaller than about 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.