Modified Gravity Black Holes and their Observable Shadows

TL;DR

This paper investigates how modified gravity black holes differ from standard ones in their shadow sizes and discusses how EHT observations can test the validity of Einstein's general relativity in strong gravity regimes.

Contribution

It analyzes the observable shadows of non-rotating and rotating MOG black holes, highlighting how their sizes depend on the parameter lpha, and proposes using EHT data to test gravity theories.

Findings

Shadow sizes increase with the parameter lpha.

EHT measurements can distinguish between Einstein's GR and modified gravity.

Modified gravity black holes have larger shadows than their GR counterparts.

Abstract

The shadows cast by non-rotating and rotating modified gravity (MOG) black holes are determined by the two parameters mass $M$ and angular momentum $J=Ma$. The sizes of the shadows cast by the spherically symmetric static Schwarzschild-MOG and Kerr-MOG rotating black holes increase significantly as the free parameter $\alpha$ is increased from zero. The Event Horizon Telescope (EHT) shadow image measurements can determine whether Einstein's general relativity is correct or whether it should be modified in the presence of strong gravitational fields.