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Left, top and middle: Diffraction-limited $K'$-band image of NGC 1068 reconstructed by bispectrum speckle interferometry. The image shows the compact core (yellow) with its tail-shaped, north-western extension at P.A. of approximately -16degr as well as the northern and south-eastern extended components (red). In addition to these structures, the first diffraction ring around the compact component is visible. The contour levels are 1, 2, 4, 8, 16, 32, and 64% of the peak intensity. North is up, and east is to the left. Right, top and middle: Diffraction-limited H-band image, which also shows the tail-shaped, north-western extension. The contour levels are 4, 8, 16, 32, and 64% of the peak intensity. Bottom: MERLIN 5 GHz contour map superposed on our K'-band image. The center of the radio component S1 coincides with the center of the K'-band peak. The P.A. of -16degr of the 18x39 mas K'-band core is very similar to that of the western wall (P.A. ~ -15degr) of the bright region of the ionization cone. The northern extended 400 mas structure (red) aligns with the direction of the inner radio jet (S1 - C). The northern borderline of the northern component is almost perpendicular to the radio jet direction between C and NE. The P.A. of the south-eastern extended component is similar to the P.A. of S1 - S2.

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, p. 77-87 (2004)

Abstract

We present near-infrared bispectrum speckle interferometry studies of the nuclear region of the Seyfert\,2 galaxy NGC 1068. A diffraction-limited $K'$-band image with 74\,mas resolution and the first $H$-band image with 57\,mas resolution were reconstructed from speckle interferograms obtained with the SAO 6\,m 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 18\,$\times$\,39\,mas or 1.3\,$\times$\,2.8\,pc (FWHM of a single-component Gaussian fit; fit range 30--80{\%} of the telescope cut-off frequency; the diameter errors are $\pm$\,4\,mas), and the position angle (P.A.) of the north-western extension is --16\,$\pm$\,4{\degr}. 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 26\,$\times$\,58\,mas is obtained for the compact $K'$ component. In the $H$ band, the FWHM diameter of the compact core is approximately 18\,$\times$\,45\,mas ($\pm$\,4\,mas), and the P.A. is --18\,$\pm$\,4{\degr}. The extended northern component (P.A.\,$\sim$\,0{\degr}) has an elongated structure with a length of about 400\,mas or 29\,pc. 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\,$\pm$\,90\,mJy (i.e., $K'$\,$\sim$\,8.2$^m$) and 70\,$\pm$\,20\,mJy ($H$\,$\sim$\,10.4$^m$), respectively. The P.A. of --16\,$\pm$\,4{\degr} of the compact 18\,$\times$\,39\,mas core is very similar to that of the western wall (P.A.\,$\sim$\,--15{\degr}) 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 -- 1\,pc). The northern extended 400\,mas structure lies near the western wall of the ionization cone and coincides with the inner radio jet (P.A.\,$\sim \,11${\degr}). 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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