Black hole shadow to probe modified gravity

TL;DR

This paper investigates black hole shadows in modified gravity with a cosmological constant, deriving constraints on nd analyzing effects on photon spheres and shadows, consistent with cosmological data.

Contribution

It provides new constraints on the cosmological constant from black hole shadow observations and explores its effects on photon spheres in modified gravity.

Findings

Constraints on rom M87* shadow data

Effects of nd spin on photon spheres

Agreement with cosmological measurements

Abstract

We study the black hole's shadow for Schwarzschild - de Sitter and Kerr - de Sitter metrics with the contribution of the cosmological constant \Lambda. Based on the reported parameters of the M87* black hole shadow we obtain constraints for the $\Lambda$ and show the agreement with the cosmological data. It is shown that, the coupling of the \Lambda-term with the spin parameter reveals peculiarities for the photon spheres and hence for the shadows. Within the parametrized post-Newtonian formalism the constraint for the corresponding \Lambda-determined parameter is obtained.