Publications
of the
MPIfR Optical & Infrared Interferometry Group

G. Weigelt, M. Wittkowski, Y.Y. Balega, T. Beckert, W.J. Duschl, K.-H. Hofmann, A.B. Men'shchikov, D. Schertl

Diffraction-Limited Bispectrum Speckle Interferometry of the Nuclear Region of the Seyfert Galaxy NGC 1068 in the H and K' Bands

A&A 425, 77 (2004)

Abstract

We present near-infrared bispectrum speckle interferometry studies of the nuclear region of the Seyfert2 galaxy NGC 1068. A diffraction- limited K'-band image with 74mas resolution and the first H-band image with 57mas resolution were reconstructed from speckle interferograms obtained with the SAO 6m telescope. The resolved structure consists of a compact core and an extended northern and south-eastern component. The compact core is resolved at all position angles and has a north-western, tail-shaped extension as well as a fainter, south-eastern extension. The K'-band FWHM diameter of this compact core is approximately 18x39mas or 1.3x2.8pc (FWHM of a single-component Gaussian fit; fit range 30-80% of the telescope cut-off frequency; the diameter errors are +-4mas, and the position angle (P.A.) of the north-western extension is -16+-4°. If 40% of the flux from the compact K' core is emission from a point source and 60% from a Gaussian intensity distribution, then a slightly larger FWHM of approximately 26x58mas is obtained for the compact K' component. In the H band, the FWHM diameter of the compact core is approximately 18x45mas (+-4mas), and the P.A. is -18+-4°. The extended northern component (P.A.~0°) has an elongated structure with a length of about 400mas or 29pc. The extended south-eastern component is fainter than the northern component. The K'- and H-band fluxes from the resolved compact core were measured to be 350+-90mJy (i.e., K'~8.2m) and 70+-20mJy (H~10.4m), respectively. The P.A.of -16+-4° of the compact 18x39mas core is very similar to that of the western wall (P.A.~-15°) of the bright region of the ionization cone. This suggests that the H- and K'-band emission from the compact core is both thermal emission and scattered light from dust near the western wall of a low-density, conical cavity or from the innermost region of a parsec-scale dusty torus that is heated by the central source (the dust sublimation radius of NGC 1068 is approximately 0.1 - 1pc). The northern extended 400mas structure lies near the western wall of the ionization cone and coincides with the inner radio jet (P.A.~11°). The large distance from the core suggests that the K'-band emission of the northern extended component is scattered light from the western cavity region and the radio jet region.

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