Quasinormal modes and shadow of Schwarzschild black holes embedded in a Dehnen-type dark matter halo exhibiting a cloud of strings
Аннотация
Abstract In this paper we consider a static spherically symmetric black hole (BH) embedded in a Dehnen-(1, 4, 0)-type dark matter (DM) halo in the presence of a cloud string. We examine and present data on how the core density of the DM halo parameter and the cloud string parameter affect BH attributes such as quasinormal modes (QNMs) and shadow cast. To do this, we first look into the effective potential of perturbation equations for three types of perturbation fields with different spins: massless scalar field, electromagnetic field and gravitational field. Then, using the sixth-order Wentzel–Kramers–Brillouin approximation, we examine QNMs of the BH disturbed by the three fields and derive quasinormal frequencies. The changes in QNM versus the core density parameter and the cloud string parameter for three disturbances are explored. We also investigate how the core density and the cloud string parameter affect the photon sphere and shadow radius. Interestingly, the study shows that the influence of Dehnen-type DM and cloud strings increases both the photon sphere and the shadow radius. Finally, we employ observational data from Sgr A ⋆ and M87 ⋆ to set limitations on the BH parameters.