Polarized Image of a Synchrotron-emitting Ring in Einstein-Maxwell-scalar Theory

TL;DR

This paper explores how scalar fields coupled to electromagnetic fields in Einstein-Maxwell-scalar theory affect the polarization patterns of synchrotron-emitting rings around hairy black holes, revealing potential observational signatures.

Contribution

It provides the first analysis of polarized images of hairy black holes in Einstein-Maxwell-scalar theory, highlighting effects of scalar-electromagnetic coupling on polarization.

Findings

Polarization patterns are qualitatively similar to Schwarzschild black holes.

Scalar-electromagnetic coupling amplifies polarization intensity.

Coupling and charge induce deviations in electric vector position angle.

Abstract

This study investigates polarized images of an equatorial synchrotron-emitting ring surrounding hairy black holes within the Einstein-Maxwell-scalar theory. Our analysis demonstrates qualitative similarities between the polarization patterns of hairy black holes and Schwarzschild black holes. However, due to the non-minimal coupling between the scalar and electromagnetic fields, an increase in black hole charge and coupling constant can substantially amplify polarization intensity and induce deviations in the electric vector position angle. These effects may offer observational signatures to distinguish hairy black holes from Schwarzschild black holes.