Bibcode
Lopez-Rodriguez, E.; Packham, C.; Young, S.; Elitzur, M.; Levenson, N. A.; Mason, R. E.; Ramos-Almeida, C.; Alonso-Herrero, A.; Jones, T. J.; Perlman, E.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 431, Issue 3, p.2723-2736
Fecha de publicación:
5
2013
Número de citas
18
Número de citas referidas
16
Descripción
An optically and geometrically thick torus obscures the central engine
of active galactic nuclei (AGN) from some lines of sight. From a
magnetohydrodynamical framework, the torus can be considered to be a
particular region of clouds surrounding the central engine where the
clouds are dusty and optically thick. In this framework, the magnetic
field plays an important role in the creation, morphology and evolution
of the torus. If the dust grains within the clouds are assumed to be
aligned by paramagnetic alignment, then the ratio of the intrinsic
polarization and visual extinction, P(per cent)/Av, is a
function of the magnetic field strength. To estimate the visual
extinction through the torus and constrain the polarization mechanisms
in the nucleus of the type 2 AGN, IC 5063, we developed a polarization
model to fit both the total and polarized flux in a 1.2-arcsec
(˜263 pc) aperture. The polarization model is consistent with the
nuclear polarization observed at Kn (2.0-2.3 μm) being
produced by dichroic absorption from aligned dust grains with a visual
extinction through the torus of 48 ± 2 mag. We estimated the
intrinsic polarization arising from dichroic absorption to be
P^{{dic}}_{{{K_n}}} = 12.5 ± 2.7 per cent. We consider the
physical conditions and environment of the gas and dust for the torus of
IC 5063. Then, through paramagnetic alignment, we estimate a magnetic
field strength in the range of 12-128 mG in the near-infrared emitting
regions of the torus of IC 5063. Alternatively, we estimate the magnetic
field strength in the plane of the sky using the Chandrasekhar-Fermi
method. The minimum magnetic field strength in the plane of the sky is
estimated to be 13 and 41 mG depending of the conditions within the
torus of IC 5063. These techniques afford the chance to make a survey of
AGN, to investigate the effects of magnetic field strength on the torus,
accretion and interaction to the host galaxy.
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