Influence of plasma on the observational appearance of rotating black holes in Horndeski gravity

TL;DR

This paper investigates how plasma affects the appearance of rotating black holes in Horndeski gravity, analyzing light trajectories and shadows, and comparing results with Event Horizon Telescope data to constrain plasma properties.

Contribution

It introduces a detailed analysis of plasma effects on black hole shadows in Horndeski gravity, including uniform and non-uniform plasma distributions, and compares theoretical predictions with observational data.

Findings

Plasma significantly alters black hole shadow shapes.

Hair parameter and inclination angle influence shadow size.

Comparison with EHT data constrains plasma parameters.

Abstract

Exploring the influence of plasma on the light rays trajectories in the vicinity of black holes is significat since that astrophysical black holes are generally surrounded by a plasma medium. In this work, we analyze the null geodesics in the space-time of rotating hairy Horndeski black holes immersed in a plasma medium using the Hamilton-Jacobi method. By considering both uniform and non-uniform plasma distributions, we perform a comparative study of their effects on the black hole shadow. The impact of the hair parameter and the inclination angle on the black hole shadow is also investigated. Finally, the shadow results are compared with observational data of the Event Horizon Telescope for M87* to constrain the plasma parameter.