Probing Axions via Light Circular Polarization and Event Horizon Telescope

TL;DR

This paper explores how axion-like particles could influence light polarization near supermassive black holes, using recent Event Horizon Telescope data to constrain axion properties and suggest future polarization measurements as a probe.

Contribution

It introduces a novel mechanism for circular polarization generation via axion-photon interactions near SMBHs and discusses how polarization data can constrain axion parameters.

Findings

Significant circular polarization can be produced by axion-photon interactions.

Polarization measurements can constrain ultralight axion-like particle parameters.

Future precise polarization data can probe axion features near SMBHs.

Abstract

The impact of axion-like particles on the light polarization around the horizon of suppermassive black hole (SMBH) is discussed in the light of the latest polarization measurement of the Event Horizon Telescope (EHT). We investigate different sources of the polarization due to axion interaction with photons and the magnetic field of SMBH. These can modify the linear and circular polarization parameters of the emitted light. We have shown that a significant circular polarization can be produced via the photon scattering from the background magnetic field with axions as off-shell particles. This can further constrain the parameter space of ultralight axion-like particles and their couplings with photons. The future precise measurements of circular polarization can probe the features of ultralight axions in the near vicinity of SMBH.