Issue |
A&A
Volume 411, Number 3, December I 2003
|
|
---|---|---|
Page(s) | 335 - 342 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20031376 | |
Published online | 17 November 2003 |
High angular resolution K-band spectroscopy of the nucleus of NGC 1068 with PUEO-GRIF (CFHT)
1
LESIA, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon, France e-mail: firstname.lastname@obspm.fr
2
CFHT Corporation, 68-1238 Mamalahoa Highway, Kamulea HI 96743, USA
Corresponding author: D. Gratadour, damien.gratadour@obspm.fr
Received:
21
January
2003
Accepted:
7
July
2003
We provide new high angular resolution K-band
spectroscopic observations of the nucleus of NGC 1068
obtained with the new 3-D spectrograph GriF coupled to PUEO, the
CFHT adaptive optics system. Results match well with the general
framework of the unified model of active galactic nuclei (AGN) and
bring more precise evaluation of the size and structure of the
close AGN environment. The K-band emission is dominated by the
thermal continuum of the compact central source (albeit resolved:
´´) with a color temperature around 950 K
(reddened sublimation temperature of the dust, corresponding to
1200 K when deredenned), interpreted as the border of a
sublimation cavity within the dust torus, surrounding the central
core. Coronal emission lines ([
], [
] and
[
]) are detected from a few tenths of arcseconds
around this compact source and a new [
] emission spot
is found at 0.7´´ north of the central source. The Brackett
γ emission features a very broad component
(
km s-1) in the central 200 mas and we
claim that it correponds to the broad line region seen through the
dust. A narrower component (
km s-1) is
seen at larger angular distance and is likely the trace of the
narrow line region. Molecular hydrogen emission lines are detected
beyond 0.6´´ of the central source. We interpret the lack of
emission in the center as a lack of excited molecular H2 along
the line of sight, because of the putitative dust torus shading
gas from UV photons. No evidence of stellar activity in a 1´´
radius around the central source can be found. We also compare
these observations to the results of a numerical model of a torus
harboring an active galactic nucleus. The main characteristics of
the observed spectra (slope, flux) match well with the unified
scheme of AGN, in the case of a dense (
) obscuring
torus containing silicate grains with an inclination angle of
around 22° with regards to the line of sight.
Key words: galaxies: Seyfert / galaxies: individual: NGC 1068 / infrared: galaxies / instrumentation: adaptive optics / instrumentation: spectrographs / radiative transfer
© ESO, 2003
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