The Use of Faraday Rotation Sign Maps as a Diagnostic for Helical Jet Magnetic Fields

Abstract

We present maps of the sign of the Faraday Rotation measure [sign(RM)] obtained from multi-frequency radio observations on the Very Long Baseline Array (VLBA). Many of the Active Galactic Nuclei (AGN) considered have B-field structures with a central "spine" of B-field orthogonal to the jet and/or a longitudinal B-field near one or both edges of the jet. This structure can plausibly be interpreted as being caused by a helical/toroidal jet magnetic field. Faraday Rotation is a rotation of the plane of polarization that occurs when the polarized radiation passes through a magnetized plasma. The sign of the RM is determined by the direction of the line-of-sight B-Field in the region causing the Faraday Rotation, and an ordered toroidal or helical magnetic field associated with an AGN jet will thus produce a distinctive bilateral distribution of positive and negative RMs across the jet. We present and discuss sign(RM) maps and their possible interpretation regarding the magnetic field geometries for several sources.

From the proceedings of Beamed and Unbeamed Gamma-Rays from Galaxies, April 11-15, 2011, Muonio, Finland. 5 pages, 4 figures

References in corpus (1)

• Multifrequency Polarimetry of the Nrao 140 Jet: Possible Detection of a Helical Magnetic Field and Constraints on its Pitch Angle

Cited by in corpus (4)

• MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VIII. Faraday rotation in parsec-scale AGN jets
• Polarization signatures of unresolved radio sources
• Using Coordinated Observations in Polarised White Light and Faraday Rotation to Probe the Spatial Position and Magnetic Field of an Interplanetary Sheath
• Imaging VLBI polarimetry data from Active Galactic Nuclei using the Maximum Entropy Method