TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 65 (No. 10), pp. 1117-1122, 2013

New insights into the study of magnetic field in the clumpy torus of AGN using near-infrared polarimetry

E. Lopez-Rodriguez1,2, C. Packham1,2, S. Young3, M. Elitzur4, N. A. Levenson5, R. E. Mason6, C. Ramos Almeida7,8, A. Alonso-Herrero9, T. J. Jones10, and E. Perlman11

1Department of Physics & Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA
2Department of Astronomy, University of Florida, 211 Bryant Space Science Center, P.O. Box 11205, Gainesville, FL 32611-2055, USA
3Centre for Astrophysics Research, Science & Technology Research Institute, University of Hertfordshire, Hatfield, AL10 9AB, UK
4Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506, USA
5Gemini Observatory, Southern Operations Center, c/o AURA, Casilla 603, La Serena, Chile
6Gemini Observatory, Northern Operations Center, 670 N. A'ohoku Place, Hilo, HI 96720
7Instituto de Astrofísica de Canarias, C/Vía Láctea, s/n, E-38205, La Laguna, Tenerife, Spain
8Departamento de Astrofísica, Universidad de La Laguna, E-38205, La Laguna, Tenerife, Spain
9Instituto de Física de Cantabria, CSIC-Universidad de Cantabria, 39005 Santander, Spain
10Department of Astronomy, University of Minnesota, 116 Church Street S. E., Minneapolis, MN 55455, USA
11Department of Physics and Space Sciences, 150 W. University Blvd., Florida Institute of Technology, Melbourne, FL 32901, USA

(Received November 14, 2012; Revised April 10, 2013; Accepted May 20, 2013; Online published October 24, 2013)

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 PdicKn = 12.5 ± 2.7%. The dust grain alignment mechanism is assumed to be produced by paramagnetic relaxation. In this case, the intrinsic polarisation, PdicKn, 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.
Key words: AGN, torus - infrared: polarimetry.

Corresponding author E-mail: elr@astro.ufl.edu

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