Diffraction-limited Imaging and Photometry of NGC 1068

Abstract

The nearby Seyfert 2 galaxy NGC 1068 was observed with speckle imaging techniques in the nearinfrared H band (1.6 km) with the 200-inch Hale Telescope on Palomar Mountain and K band (2.2 km) with the 10 m Keck I Telescope at the W. M. Keck Observatory.Images with di †raction-limited or nearÈdi †raction-limited resolutions of were obtained and 0A .05È0A .1 used to search for structure in the nuclear region. Images of the nucleus of NGC 1068 reveal an extended region of emission, accounting for nearly 50% of the nuclear Ñux in the K band. This region extends 10 pc on either side of an unresolved point-source nucleus that is at most or 1.4 pc in size. 0A .02 Both the point source and the newly imaged extended emission are very red, with identical H[K colors corresponding to a color temperature of 800 K. While the point source is of a size to be consistent with grains in thermal equilibrium with the nuclear source, the extended emission is not. It must consist either of nuclear emission that has been reÑected o † an extended dusty disk or of small grains raised to transiently high temperatures by reÑected UV photons.

A new analysis of the nucleus of NGC 1068 with MIDI observations

“…Speckle imaging performed by Weinberger et al (1999) at the Keck Observatory led to consistent results.…”

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

“…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 ∼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.…”

“…The K-band visibility values obtained by speckle interferometry at spatial frequencies up to a baseline of 6−10 m (Wittkowski et al 1998: SAO 6 m telescope; Weinberger et al 1999: Keck 10 m; Weigelt et al 2004: SAO 6 m) are consistent with a single-component Gaussian intensity distribution with azimuthally averaged FWHM ∼ 30 mas (up to B = 6 m; Wittkowski et al 1998), and also with a larger ∼30−50 mas component plus a much smaller (unresolved) component (Weinberger et al 1999;Weigelt et al 2004).…”

“…However, since the speckle measurements show a structure with FWHM ∼ 30−50 mas, and the VLTI/VINCI FOV is∼56 mas, the total flux (Wittkowski et al 1998;Weinberger et al 1999;Weigelt et al 2004). Both measurements are only matched if the small component has a size clearly below ∼5 mas and if only part of the total flux in our FOV arises from this < ∼ 5 mas component, and another part from a larger component.…”

Diffraction-limited bispectrum speckle interferometry of the nuclear region of the Seyfert galaxy NGC 1068 in theHandK'bands

“…The reconstructed image is elongated and has a north-western tail at PA ∼ -20 • . Weinberger et al (1999) obtained a K-band visibility function of NGC 1068 with the 10 m Keck telescope as well as, for the first time, an H-band visibility with the 200 inch Palomar telescope. The phase of the Fourier transform of NGC 1068 was found to be consistent with zero.…”