Image of the Kerr-Newman black hole surrounded by a thin accretion disk

TL;DR

This paper models the optical appearance of Kerr-Newman black holes with thin accretion disks, analyzing how spin, charge, and observation angle influence the image structure, redshift, and intensity at different frequencies.

Contribution

It provides a detailed ray-tracing analysis of Kerr-Newman black hole images, including effects of charge, inclination, and frequency, extending previous models.

Findings

Image structure varies with inclination and black hole parameters.

Redshift distribution is affected by inclination angle.

Intensity differs between frequencies and accretion scenarios.

Abstract

The image of a Kerr-Newman (KN) black hole (BH) surrounded by a thin accretion disk is derived. By employing elliptic integrals and ray-tracing methods, we analyze photon trajectories around the KN BH. At low observation inclination angles, the secondary image of particles is embedded within the primary image. However, as the inclination increases, the primary and secondary images separate, forming a hat-like structure. The spin and charge of the BH, along with the observer's inclination angle, affect the image's asymmetry and the distortion of the inner shadow. To investigate the redshift distribution on the accretion disk, we extended the inner boundary of the accretion disk to the event horizon. The results show that the redshift distribution is significantly influenced by the observation inclination angle. Furthermore, we conducted a detailed analysis of the KN BH image using fisheye camera ray-tracing techniques and found that the optical appearance and intensity distribution of the BH vary at different observation frequencies (specifically at 230GHz and 86GHz). We also examined differences in intensity distribution for prograde and retrograde accretion disk scenarios. Comparing observational at the two frequencies, we found that both the total intensity and peak intensity at 86GHz are higher than those at 230GHz.