Shadow analysis for rotating black holes in the presence of plasma for an expanding universe

We explore the structure of shadow for a Kerr-de Sitter black hole with a nonmagnetized, pressureless plasma surrounding it. Specific plasma distributions are considered to separate the Hamilton-Jacobi equation and find the photon regions. An analytic formula describing the boundary curve of the shadow for such a black hole in an expanding universe for an observer at any finite point outside the horizon is derived. We observe deviations which are further explored by calculating the curvature radius at a particular point and distortion parameter for such structures in the presence and absence of plasma and calculate the diameter of the shadow.

Automated summary

This study explores the structure of a Kerr-de Sitter black hole shadow in the presence of a nonmagnetized, pressureless plasma, deriving an analytic formula for the boundary curve of the shadow in an expanding universe. Deviations are observed and further analyzed through calculations of curvature radius, distortion parameter, and shadow diameter with and without plasma influence.