Analytical ray-tracing of synchrotron emission around accreting black holes

TL;DR

This paper develops an analytical ray-tracing method for polarized synchrotron emission around black holes, enabling fast modeling of polarimetric images considering complex matter motions and geometries.

Contribution

It introduces a novel analytical formalism for polarized light ray-tracing in curved spacetime, accounting for non-equatorial matter elevation and non-circular motions.

Findings

Derived analytical expressions for intensity and polarization transformations.

Applicable to static and dynamic polarimetric imaging of black hole environments.

Enhances understanding of polarization signatures in strong gravity regimes.

Abstract

Polarimetric images of accreting black holes encode important information about laws of strong gravity and relativistic motions of matter. Recent advancements in instrumentation enabled such studies in two objects: supermassive black holes M87* and Sagittarius A*. Light coming from these sources is produced by synchrotron mechanism whose polarization is directly linked to magnetic field lines, and propagates towards the observer in a curved spacetime. We study the distortions of the gas image by the analytical ray-tracing technique for polarized light artpol, that is adapted for the case of synchrotron emission. We derive analytical expressions for fast conversion of intensity/flux, polarization degree and polarization angle from the local to observer's coordinates. We put emphasis on the non-zero matter elevation above the equatorial plane and non-circular matter motions. Applications of the developed formalism include static polarimetric imaging of the black hole vicinity and dynamic polarimetric signatures of matter close to the compact object.