Visual Characteristics of a Rotating Black Hole in $4$D Einstein-Gauss-Bonnet Gravity with Thin Accretion Disk Under EHT Constraints

Abstract

This study investigates the visual characteristics of a rotating black hole (BH) within the fabric of $4$D Einstein-Gauss-Bonnet gravity illuminated with two illumination models, such as a celestial light sphere and a thin accretion disk. To visualize the BH shadow images, we use a recent fisheye camera model and ray-tracing method. And then, we focus on investigating the impact of the coupling parameter $\alpha$ and the spin parameter $a$ on the shadow images. The results exhibit that the shadow radius decreases, while the shadow deviation increases with the aid of $\alpha$. However, with respect to $a$, the shadow radius is slightly increased compared to the corresponding shadow deviation. For a celestial light sphere, the increasing values of $\alpha$, lead to a decrease in the corresponding photon ring, while the space-dragging effect becomes more prominent with increasing $a$. For a thin accretion disk, we enhance its inner edge to the BH event horizon, and the particle motion is different in the regions inside and outside the innermost stable circular orbit. The result demonstrates that the shadow becomes progressively asymmetric with $a$, while the overall size of the inner shadow gradually decreases with the variations of $\alpha$. Subsequently, we also investigated the distinct features of red-shift configurations on the disk for both direct and lensed images. Additionally, we used the latest observational data from M87* and Sgr A* to impose certain parameter constraints on $\alpha$; the results depict the consistency of our considering the BH model.