Radiative Transfer Modeling of Radio-band Linear Polarization Observations as a Probe of the Physical Conditions in the Jets of Gamma-ray Flaring Blazars

TL;DR

This paper presents a radiative transfer model incorporating relativistic shocks to interpret radio polarization and flux data from blazar jets, providing insights into jet physics during gamma-ray flares.

Contribution

The study introduces a comprehensive radiative transfer model that links polarization observations with jet shock properties, advancing understanding of jet dynamics during flaring events.

Findings

Model successfully reproduces polarization and flux data during flares

Identifies intrinsic jet flow changes over decades

Supports shock compression of turbulent magnetic fields with ordered components

Abstract

Since the mid-1980s the shock-in-jet model has been the preferred paradigm to explain radio-band flaring in blazar jets. We describe our radiative transfer model incorporating relativistically-propagating shocks, and illustrate how the 4.8, 8, and 14.5 GHz linear polarization and total flux density data from the University of Michigan monitoring program, in combination with the model, constrain jet flow conditions and shock attributes. Results from strong Fermi-era flares in 4 blazars with widely-ranging properties are presented. Additionally, to investigate jet evolution on decadal time scales we analyze 3 outbursts in OT 081 spanning nearly 3 decades and find intrinsic changes attributable to flow changes at a common spatial location, or, alternatively, to a change in the jet segment viewed. The model's success in reproducing these data supports a scenario in which relativistic shocks compress a plasma with an embedded passive, initially-turbulent magnetic field, with additional ordered magnetic field components, one of which may be helical.