Shadows of Kerr-like black holes in a modified gravity theory

Abstract

In this paper, the shadows cast by non-rotating and rotating modified gravity black holes are investigated. In addition to the black hole spin parameter $a$ and the inclination angle $\theta$ of observer, another parameter $\alpha$ measuring the deviation of gravitational constant from the Newton one is also found to affect the shape of the black hole shadow. The result shows that, for fixed values of $a/M$ and $\theta$, the size and perimeter of the shadows cast by the non-rotating and rotating black holes significantly increase with the parameter $\alpha$, while the distortions decrease with $\alpha$. Moreover, the energy emission rate of the black hole in high energy case is also investigated, and the result shows that the peak of the emission rate decreases with the parameter $\alpha$.