Parsec Scale Faraday-Rotation Structure Across the Jets of 9 Active Galactic Nuclei

TL;DR

This study presents parsec-scale Faraday rotation measure maps of nine active galactic nuclei, revealing consistent transverse RM gradients that support the presence of helical magnetic fields in AGN jets.

Contribution

It provides new high-resolution RM maps and confirms the prevalence of transverse RM gradients, indicating widespread helical magnetic fields in AGN jets.

Findings

All nine AGN jets show significant transverse RM gradients.

Transverse RM gradients are consistent with helical or toroidal magnetic fields.

Results support the hypothesis of common helical magnetic structures in AGN jets.

Abstract

A number of groups have recently been active in searching for gradients in the ob- served Faraday rotation measure (RM) across jets of Active Galactic Nuclei (AGNs) on various scales and estimating their reliability. Such RM structures provide direct evidence for the presence of an azimuthal magnetic field component, which may be associated with a helical jet magnetic field, as is expected based on the results of many theoretical studies. We present new parsec-scale RM maps of 4 AGNs here, and analyze their transverse RM structures together with those for 5 previously published RM maps. All these jets display transverse RM gradients with significances of at least 3{\sigma}. This is part of an ongoing effort to establish how common transverse RM gradients that may be associated with helical or toroidal magnetic fields are in AGNs on parsec scales.