General relativistic polarized radiative transfer: building a dynamics-observations interface

TL;DR

This paper develops a comprehensive general relativistic polarized radiative transfer framework, enabling accurate modeling of polarized emissions from relativistic sources like black holes and jets, crucial for interpreting observations and determining black hole spins.

Contribution

It provides a practical derivation of GR polarized radiative transfer equations and a fast calculation method for synchrotron emission and polarization effects, tailored for low luminosity AGNs.

Findings

Derived GR polarized radiative transfer equations from fundamental principles.

Provided a fast computational recipe for synchrotron emissivities and Faraday effects.

Highlighted the importance of these methods for constraining black hole spins.

Abstract

The rising amount of polarized observations of relativistic sources requires the correct theory for proper model fitting. The equations for general relativistic (GR) polarized radiative transfer are derived starting from the Boltzmann equation and basic ideas of general relativity. The derivation is aimed at providing a practical guide to reproducing the synchrotron part of radio & sub-mm emission from low luminosity active galactic nuclei (LLAGNs), in particular Sgr A*, and jets. The recipe for fast exact calculation of cyclo-synchrotron emissivities, absorptivities, Faraday rotation and conversion coefficients is given for isotropic particle distributions. The multitude of physical effects influencing simulated spectrum is discussed. The application of the prescribed technique is necessary to determine the black hole (BH) spin in LLAGNs, constraining it with all observations of total flux, linear and circular polarization fractions, and electric vector position angle as functions of the observed frequency.