Exploring how deviations from the Kerr metric can affect SMBH images

Black holes (BH) are objects described by General Relativity (GR), particularly by the Kerr solution. However, this solution is based on simplifying assumptions. To achieve a more realistic approach, we investigate the impact of deviations from the Kerr solution on the imaging of supermassive black holes (SMBH). We conduct General Relativistic Radiation Transport simulations using a Kerr-Like metric, which includes four nonlinear free deviation functions and is stationary, axis-symmetric, and asymptotically flat. The RAPTOR I code, an open-source ray-tracing code capable of handling arbitrary spacetimes, is employed to generate the images. We analyze the asymmetry, diameter, and shadow displacement of the BH to compare them with those of a Kerr BH. Our findings confirm that these deviations significantly affect the shape of the shadow. However, we acknowledge the importance of considering the matter distribution and emissivities surrounding the BH, as the results cannot be solely inferred from the shape of the photon ring.