University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Friday, October 24th 2014
Speaker: Dr. Enrique Rodriguez,l U Texas-San Antonio
Subject: Revealing the Core of Active Galactic Nuclei Through Infrared Polarimetry

Magnetohydrodynamical theories consider the torus of Active Galactic
Nuclei (AGN) to be part of an outflow wind moving away from the central
engine. In this framework, the torus is a particular region of the
outflowing wind, where dusty and optically thick clouds are formed. The
outflows are strongly related to the accretion rate and magnetic field
strength, which play an important role in the creation, morphology and
evolution of the torus. Through high-angular (~0.1''-0.6") infrared (IR,
1-13 um) polarimetric observations, this talk presents (1) the role of
the magnetic fields in the torus of AGN, and (2) the polarized
synchrotron core of Cygnus A.

Although several models have been made to account for the outflowing
dusty winds from the central engine, the magnetic field strength at the
position of the torus remains poorly characterized. Through near-IR
polarimetry using MMTPol at the 6.5-m MMT, the magnetic field strengths,
accretion and outflow rates within the clumpy torus of NGC 1068 were
estimated. These results provide information about the torus evolution
within the AGN unified scheme. For the archetypical radio-loud AGN,
Cygnus A, mid-IR imaging polarimetry using CanariCam (7.5-13 um) on the
10.4-m Gran Telescopio CANARIAS revealed a highly polarized, 11+/-3% at
8.7 um, unresolved core. Polarimetric modeling suggests that the MIR
polarization arises from a synchrotron component from the pc-scale jet
in the core of Cygnus A. This result represents the most compelling MIR
polarization detection of synchrotron radiation from the pc-scale jet in
Cygnus A.

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