Imprints of Dark Matter on Black Hole Shadows using Spherical Accretions

TL;DR

This paper investigates how dark matter influences black hole shadows and electromagnetic radiation, revealing that dark matter distribution significantly affects observable properties like flux intensity and shadow size, with potential implications for dark matter detection.

Contribution

It introduces models showing dark matter's impact on black hole shadows and electromagnetic flux, linking dark matter distribution to observable signatures and quasinormal modes.

Findings

Dark matter can increase or decrease electromagnetic flux intensity.

Dark matter distribution affects shadow radius and flux intensity.

High dark matter density near black holes is needed for significant effects.

Abstract

We study the possibility of identifying dark matter in the galactic center from the physical properties of the electromagnetic radiation emitted from a optical-thin disk region around a static and spherically symmetric black hole. In particular, we consider two specific models for the optical-thin disk region: a gas at rest and a gas in a radial free fall. Due to the effect of dark matter on the spacetime geometry, we find that the dark matter can increase or decrease the intensity of the electromagnetic flux radiation depending on the dark matter model. To this end, we analyze two simple dark matter models having different mass functions $\mathcal{M}(r)$, with a matter mass $M$, thickness $\Delta r_s$ along with a dark matter core radius surrounding the black hole. In addition to that, we explore the scenario of a perfect fluid dark matter surrounding the black hole. We show that in order to have significant effect of dark matter on the intensity of the electromagnetic flux radiation, a high energy density of dark matter near the black hole is needed. We also find that the surrounding dark matter distribution plays a key role on the shadow radius and the intensity of the electromagnetic flux radiation, respectively. Finally, we have used the relation between the shadow radius and the quasinormal modes (QNMs) to compute the real part of QNM frequencies.