Transverse Faraday-Rotation Gradients Across the Jets of 15 Active Galactic Nuclei

Abstract

The presence of a helical magnetic field threading the jet of an Active Galactic Nucleus (AGN) should give rise to a gradient in the observed Faraday rotation measure (RM) across the jet, due to the associated systematic change in the line-of-sight magnetic field. Reports of observations of transverse RM gradients across AGN jets have appeared in the literature starting from 2002, but concerns were raised about the resolution required for these gradients to be reliable, and there was a lack of a full understanding of the best approach to accurate estimation of the uncertainties of local RM values. These questions have now been resolved by recent Monte Carlo simulations carried out by various groups, enabling both a verification of previously published results and reliable analyses of new data. We consider here RM gradients across the jet structures of 15 AGN, some previously published in the refereed literature but without a correct and complete error analysis, and some published for the first time here, all of which have monotonic transverse RM gradients with significances of at least 3 sigma.

10 pages, 3 figures, 3 tables; Accepted for publication in MNRAS. arXiv admin note: text overlap with arXiv:1410.6653

References in corpus (5)

• MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VIII. Faraday rotation in parsec-scale AGN jets
• Aligning VLBI Images of Active Galactic Nuclei at Different Frequencies
• Radio Circular Polarization Produced in Helical Magnetic Fields in Eight Active Galactic Nuclei
• Are Spine--Sheath Polarization Structures in the Jets of Active Galactic Nuclei Associated with Helical Magnetic Fields?
• Multifrequency Polarimetry of the Nrao 140 Jet: Possible Detection of a Helical Magnetic Field and Constraints on its Pitch Angle

Cited by in corpus (9)

• Faraday rotation in the jet of M87 inside the Bondi radius: indication of winds from hot accretion flows confining the relativistic jet
• POLAMI: Polarimetric Monitoring of Active Galactic Nuclei at Millimetre Wavelengths. III. Characterisation of total flux density and polarisation variability of relativistic jets
• Cosmic Magnetism in Centimeter and Meter Wavelength Radio Astronomy
• Parsec Scale Faraday-Rotation Structure Across the Jets of 9 Active Galactic Nuclei
• Rotation and toroidal magnetic field effects on the stability of two-component jets
• 18-22 cm VLBA Faraday rotation studies of six AGN jets
• High resolution VLBI polarisation imaging of AGN with the Maximum Entropy Method
• Observational signatures of magnetic field structure in relativistic AGN jets
• Radiative Transfer Modeling of Radio-band Linear Polarization Observations as a Probe of the Physical Conditions in the Jets of Gamma-ray Flaring Blazars