Abstract
We present J, H and Kn imaging polarimetry of IC5063. NIR polarimetry observations may advance our understanding of the mechanisms of polarisation and hence magnetic field strength in the torus of AGN. In these proceedings we summarize the polarisation results of the central 1.2″ aperture (~263 pc) of IC5063. We present a simple polarising model to account for various mechanisms of polarisation in the central regions of IC5063. The model is consistent with dichroic absorption from diffuse stellar emission through dust in the nuclear bulge and electron scattering as dominant mechanisms of polarisation at J and H. Dichroic absorption from aligned dust grains within the torus of IC5063 is dominant at Kn with a visual extinction of Av = 48±2 mag by the torus. Through the use of various components to the central engine of IC5063, we estimated the intrinsic polarisation from dichroic absorption to be . The dust grain alignment mechanism is assumed to be produced by paramagnetic relaxation. In this case, the intrinsic polarisation, , and the visual extinction by the torus, Av, are related with the magnetic field strength. The magnetic field strength is estimated to be in the range of 12–128 mG, for the physical conditions and environments of the gas and dust in the NIR emitting regions of the torus of IC5063.
Highlights
The Unified Model (Antonucci, 1993; Urry and Padovani, 1995) of Active Galactic Nuclei (AGN) holds that all AGN are essentially the same object, viewed from different lines of sight (LOS)
The model is consistent with dichroic absorption from diffuse stellar emission through dust in the nuclear bulge and electron scattering as dominant mechanisms of polarisation at J and H
Through the use of various components to the central engine of IC5063, we estimated the intrinsic polarisation from dichroic absorption to be PdKinc = 12.5 ± 2.7%
Summary
The Unified Model (Antonucci, 1993; Urry and Padovani, 1995) of Active Galactic Nuclei (AGN) holds that all AGN are essentially the same object, viewed from different lines of sight (LOS). Recent high-spatial resolution observations of Seyfert galaxies, for both types of AGN, have shown that the clumpy torus model can account for the NIR and MIR emission (see Mason et al, 2006; Ramos Almeida et al, 2009, 2011; Alonso-Herrero et al, 2011). These investigations permit, from a statistical view, an examination of the general properties of the torus, i.e. inclination to our LOS, number of clouds, covering factor, optical depth of clouds, etc.
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