Influences of accretion flow and dilaton charge on the images of Einstein-Maxwell-dilation black holes

Abstract

The characteristics and images of Einstein-Maxwell-dilaton (EMD) black holes are examined in this paper, focusing on their effective potential, photon trajectories, and images with both thin and thick accretion disks. We find that the shadow and photon sphere radii decrease as the dilaton charge increases. As the observation inclination increases, the direct and secondary images become distinct, with the direct image appearing hat-shaped. Simulations indicate that the brightness of the shadow and photon ring is higher in static spherical accretion flows compared to infalling ones. The study also shows that in thin disk accretion flows, direct emission predominantly influences the observed luminosity, while photon ring emission is less significant. Additionally, the appearance of black hole images varies with the observer’s inclination angle.