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 ΔM around it. The general formula for the radius of blackhole 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 ∼√{ 3 MΔM }. 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.
 Publication:

Physics Letters B
 Pub Date:
 August 2019
 DOI:
 10.1016/j.physletb.2019.05.043
 arXiv:
 arXiv:1905.00064
 Bibcode:
 2019PhLB..795....1K
 Keywords:

 General Relativity and Quantum Cosmology
 EPrint:
 7 pages, 6 figures, revtex, the published version