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

TL;DR

This paper investigates how accretion flow types and dilaton charge affect the observable images of Einstein-Maxwell-Dilaton black holes, revealing dependencies of shadow size, brightness, and image structure on these parameters.

Contribution

It provides new insights into the influence of dilaton charge and accretion flow geometry on black hole images, including detailed simulations of shadow and photon ring features.

Findings

Shadow and photon sphere radii decrease with increasing dilaton charge.

Brightness of shadow and photon ring is higher in static spherical accretion flows.

Image appearance varies significantly with observer inclination angle.

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 thin and thick accretion disks. We found that the shadow and photon sphere radii decrease with increasing dilaton charge. As the observation inclination increases, direct and secondary images become separate, 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, the direct emission predominantly influences observed luminosity, with photon ring emission being less significant. Additionally, the appearance of black hole images varies with the observer's inclination angle.