Shadow of a black hole surrounded by dark matter

Abstract

We consider a simple spherical model consisting of a Schwarzschild black hole of mass M and a dark matter of mass ∆M around it. The general formula for the radius of black-hole shadow has been derived in this case. It is shown that the change of the shadow is not negligible, once the effective radius of the dark matter halo is of order ∼ √ 3M ∆M . For this to happen, for example, for the galactic black hole, the dark matter must be concentrated near the black hole. For small deviations from the Schwarzschild limit, the dominant contribution into the size of a shadow is due to the dark matter under the photon sphere, but at larger deviations, the matter outside the photon sphere cannot be ignored.

Shadows and deflection angle of charged and slowly rotating black holes in Einstein-Æther theory

“…In literature, the theory of black hole shadows is well-developed and is under investigation for decades. Some notable results of black hole shadows are already discussed in the literature, to list a few: Schwarzschild black hole surrounded by a Bach-Weyl ring [7]; Einstein-dilaton-Gauss-Bonnet black hole [8]; Konoplya-Zhidenko or more general parameterized black holes [9,10]; Einstein-Maxwell-Chern-Simon black hole [11]; Einstein-Maxwell-Dilaton-Axion black hole [12]; Kerr-Newman-Kasuya black hole [13]; Kerr-Perfect fluid dark matter black hole [14]; Kerr-de Sitter black hole [15]; Kerr-MOG black hole [16,17]; rotating regular black hole [18]; Kerr-Sen black hole [19]; charged rotating black hole in f (R) gravity [20], noncommutative black holes [21], Tomimatsu-Sato spacetime [22], black hole surrounded by dark matter halo [23][24][25], shadow images of a rotating global monopole [26], testing the rotational nature of the supermassive object M87 and possible signals for extra dimensions in the shadow of M87 [27,28] etc, and also naked singularities [29,30]. Recently, there also are some interesting works about the curvature and topology of the geometry of the black hole shadows [31,32].…”

Quantum corrected black holes: Quasinormal modes, scattering, shadows

“…The other characteristic is the grey-body factors which say how much of the initial flux of Hawking radiation will penetrate the potential barrier and reach a distant observer. Finally, the shadows cast by a black hole is important to determine the near horizon geometry (see for example [9][10][11][12][13][14][15][16][17] * roman.konoplya@gmail.com and references therein). The current experiments related to detection of gravitational waves from black holes as well as observations of the electromagnetic spectrum in their vicinity [18] leave an ample room for interpretation of the near horizon geometry of black holes, because the parameters of black holes and the models for the matter, surrounding them, are known with large uncertainty and freedom of interpretation.…”

Black hole shadow of a rotating polytropic black hole by the Newman–Janis algorithm without complexification

“…Replacing the metric function F (r) = − 2M r + r 2 L 2 in Eqs. (45) and (46), the impact parameters (ξ, η) associated to the unstable null geodesics around the rotating BH are given by…”

“…Over the years the shadow of the Schwarzschild geometry was considered in [28,29], while the shadow cast by the Kerr solution was studied in [30] (see also [31]). Shadows of Kerr BHs with scalar hair and BH shadows in other frameworks have been considered in [32,33] and [34][35][36][37][38][39][40][41][42][43][44][45][46][47], respectively. To explore the physics behind the so-called BH shadows, an alternative tool is provided by the well-known NJA.…”