Issue |
A&A
Volume 425, Number 1, October I 2004
|
|
---|---|---|
Page(s) | 77 - 87 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20040362 | |
Published online | 10 September 2004 |
Diffraction-limited bispectrum speckle interferometry of the nuclear region of the Seyfert galaxy NGC 1068 in the H and K' bands *
1
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: weigelt@mpifr-bonn.mpg.de
2
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
3
Special Astrophysical Observatory, Nizhnij Arkhyz, Zelenchuk region, Karachai-Cherkesia 357147, Russia
4
Institut für Theoretische Astrophysik der Universität Heidelberg, Tiergartenstraße 15, 69121 Heidelberg, Germany
5
Institute for Computational Astrophysics, Saint Mary's University, Halifax, NS B3H 3C3, Canada
Received:
1
March
2004
Accepted:
4
June
2004
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 39 mas or
1.3
2.8 pc (FWHM of a single-component Gaussian fit;
fit range 30–80% of the telescope cut-off frequency; the
diameter errors are ±4 mas), and the position angle (PA)
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 26
58 mas is
obtained for the compact K' component. In the H band, the FWHM
diameter of the compact core is approximately
18
45 mas (±4 mas), and the PA is
–18 ± 4°. The extended northern component
(PA ~ 0°) 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 ± 90 mJy (i.e., K' ~ 8.2m) and
70 ± 20 mJy (H ~ 10.4m), respectively. The PA
of –16 ± 4° of the compact 18
39 mas core
is very similar to that of the western wall
(PA ~ –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 0.1–1 pc). The northern extended 400 mas structure lies near the western wall of the ionization
cone and coincides with the inner radio jet (PA ~ 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.
Key words: techniques: interferometric / galaxies: fundamental parameters / galaxies: nuclei / galaxies: photometry / galaxies: Seyfert / galaxies: individual: NGC 1068
© ESO, 2004
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