Physical Conditions and Variability Processes in AGN Jets through Multi-Frequency Linear and Circular Radio Polarization Monitoring

TL;DR

This study develops a high-precision radio polarimetry analysis method to investigate the physical conditions and variability in AGN jets, applying it to a large sample and modeling polarization behavior with radiative transfer simulations.

Contribution

It introduces a comprehensive data analysis approach for polarization recovery and applies it to a significant AGN sample, linking polarization variability to jet shock models.

Findings

Recovered polarization properties for 87 AGNs across multiple frequencies.

Identified physical conditions and processes responsible for polarization variability.

Modeled polarization behavior of blazar 3C 454.3 with internal shock simulations.

Abstract

Radio polarimetry is an invaluable tool to investigate the physical conditions and variability processes in active galactic nuclei (AGN) jets. However, detecting their linear and circular polarization properties is a challenging endeavor due to their low levels and possible depolarization effects. We have developed an end-to-end data analysis methodology to recover the polarization properties of unresolved sources with high accuracy. It has been applied to recover the linear and circular polarization of 87 AGNs measured by the F-GAMMA program from July 2010 to January 2015 with a mean cadence of 1.3 months. Their linear polarization was recovered at four frequencies between 2.64 and 10.45 GHz and the circular polarization at 4.85 and 8.35 GHz. The physical conditions required to reproduce the observed polarization properties and the processes which induce their variability were investigated with a full-Stokes radiative transfer code which emulates the synchrotron emission of modeled jets. The model was used to investigate the conditions needed to reproduce the observed polarization behavior for the blazar 3C 454.3, assuming that the observed variability is attributed to evolving internal shocks propagating downstream.