Bibcode
DOI
Arribas, S.; Mediavilla, E.; Garcia-Lorenzo, B.
Referencia bibliográfica
Astrophysical Journal v.463, p.509
Fecha de publicación:
6
1996
Número de citas
52
Número de citas referidas
44
Descripción
Bidimensional spectroscopy of the circumnuclear region (central 10" x
8") of the Seyfert 2 galaxy NGC 1068 has been performed by means of an
optical fiber system. The 95 spectra obtained simultaneously include the
[N II] λλ6548, 6583, Hα, and [S II]
λλ6716,6731 emission lines. In the inner regions, the
velocity field obtained by cross-correlating the spectra shows a strong
S-distortion, which can be explained as due to the presence of radial
motions outside the galaxy's plane. The optical nucleus is displaced
with respect to the kinematic center. The spectra show multicomponent
line profiles due to the integration of several gaseous systems along
the line of sight. By using a model of four components, which fits the
line profiles obtained remarkably well, we accomplished a deprojection
of the corresponding kinematic systems, which allows the velocity fields
and line intensity maps of each system to be studied separately. The
AGN-like ionizing radiation field seems to exhibit a biconical
morphology, judging from the individual line intensity maps associated
with the distinct gaseous systems. This is in better agreement with
current active galactic nucleus (AGN) models for a Seyfert 2 than the
single conical structure proposed by other authors on the basis of
filter imaging maps. This result is supported by independent kinematic
(i.e., the existence of outflowing cones) and geometric (i.e., small
inclination of the cones with respect to the disk) arguments. We propose
that the hidden nucleus of NGC 1068 may be located toward northeast of
positions recently quoted. On the one hand, the origin of the outflowing
gas dominating the inner velocity field, which is likely to be related
directly to the active nucleus, is about 1" northeast of the optical
nucleus. The center of rotation derived from the outer velocity field
also sits northeast of the optical nucleus. On the other hand, the
bipolar morphology of the intensity maps of the distinct gaseous system
is centered close to the kinematic center, also supporting this
conclusion. The proposed location for the hidden nucleus is neither in
positional agreement with the radio peak nor with the peak at
midinfrared images, according to current astrometry. We have
reinterpreted the ionization map [O III]/(Hα + [N II]) and Hubble
Space Telescope images of NGC 1068 obtained by other authors, finding
that they are compatible with a biconical ionization morphology, and
with the proposed location for the hidden nucleus.