Kerr-like Black Hole Surrounded by Cold Dark Matter Halo: The Shadow Images and EHT Constraints

TL;DR

This paper models the shadow images of a Kerr-like black hole within a cold dark matter halo, analyzing how parameters like spin, density, and scale radius affect observable features, with implications for EHT constraints.

Contribution

It introduces a detailed simulation of black hole shadows considering dark matter halo effects and assesses parameter influences on observable shadow features.

Findings

Increased spin shifts circular orbits rightwards.

Higher critical density and scale radius enlarge the shadow.

Retrograde flow reduces shadow intensity and creates crescent shapes.

Abstract

Here we provide shadow images of a Kerr-like black hole (BH) in cold dark matter (CDM) halo illuminated with a celestial light source and a thin accretion disk. The impact of spin parameter, critical density and the scale radius on the observed images of BHs is carefully addressed. The results indicate that as spin parameter increases, the circular orbits are shifted rightwards, while the larger values of critical density and the scale radius are the cause to enhance the radius of circular orbits of the BH shadow. In the case of the celestial light source, the impact of critical density on shadow distortion is negligible, but this influence is relatively smaller and becomes appreciable when the scale radius has larger values. Next, we discuss the intensity and the size of the inner shadow, which are gradually increasing with the increase of both parameters. On the other hand, in the case of retrograde flow, the intensity of the shadow images significantly decreases, and a crescent moon emerges on the upper right side of the screen. Subsequently, the distinctive features of red-shift factors for direct and lensed images with prograde and retrograde flows are discussed. The outcomes indicate that the distribution of red-shift factors and the optical appearance are closely related to the behavior of accreting flow as well as to relevant parameters.