# Broadband, radio spectro-polarimetric study of 100 radiative-mode and jet-mode AGN

## TL;DR

This study uses broadband spectro-polarimetry to analyze the polarization and magnetic field structures of 100 extragalactic radio sources, revealing differences between AGN types and their polarization properties.

## Contribution

It introduces a polarization model-fitting method to characterize multiple RM components and compares polarization properties of radiative- and jet-mode AGN.

## Key findings

- High polarization sources have low Faraday depolarization and are dominated by a single RM component.
- Jet-mode AGN have more ordered magnetic fields than radiative-mode AGN.
- Jet-mode AGN show a preferred magnetic field orientation perpendicular to the jet direction.

## Abstract

We present the results from a broadband (1 to 3 GHz), spectro-polarimetry study of the integrated emission from 100 extragalactic radio sources with the ATCA, selected to be highly linearly polarized at 1.4 GHz. We use a general purpose, polarization model-fitting procedure that describes the Faraday rotation measure (RM) and intrinsic polarization structure of up to three distinct polarized emission regions or 'RM components' of a source. Overall, 37%/52%/11% of sources are best fit by one/two/three RM components. However, these fractions are dependent on the signal-to-noise ratio (S/N) in polarization (more RM components more likely at higher S/N). In general, our analysis shows that sources with high integrated degrees of polarization at 1.4 GHz have low Faraday depolarization, are typically dominated by a single RM component, have a steep spectral index, and a high intrinsic degree of polarization. After classifying our sample into radiative-mode and jet-mode AGN, we find no significant difference between the Faraday rotation or Faraday depolarization properties of jet-mode and radiative-mode AGN. However, there is a statistically significant difference in the intrinsic degree of polarization between the two types, with the jet-mode sources having more intrinsically ordered magnetic field structures than the radiative-mode sources. We also find a preferred perpendicular orientation of the intrinsic magnetic field structure of jet-mode AGN with respect to the jet direction, while no clear preference is found for the radiative-mode sources.