Shadows of quintessential dark energy black holes in the domain of outer communication

Abstract

The rotating black holes in the quintessential dark energy correspond to three horizons: inner, outer, and quintessential horizon. The domain of outer communication is the region between outer and quintessential horizon. Here in this work, we study the photon region and shadows of the quintessential dark energy black holes when the observer stays statically in the domain of outer communication. The quintessential dark energy black holes shadow characterizes by its mass (M), spin parameter (a), quintessential dark energy parameter (ωq), and normalization factor (γ). The dark energy parameter ωq can take values between −1.1<ωq<−1/3 and follows the equation of state ωq = pressure(p)/energy density(ρq). This state parameter significantly affects the shape and the size of the black hole shadow. We generalize all the geodesic equations of motion for ωq and obtain relation to visualizing the black hole shadow by a static observer at any arbitrary distance in the domain of outer communication. We estimate the black hole shadow observables: radius Rs, distortion parameter δs, and the shadow area A. Using the numerical values of shadow radius Rs and area A, we obtain the angular diameter (θd) of the black hole shadow. The angular diameter of the M87 and Sgr A∗ black holes shadow are 42±3μas and 48.7±7μas respectively as observe by Event Horizon Telescope (EHT). In this case, the angular diameter of the black hole shadow varies from θd≈21o±4 with γ from 0.08/M to 0.12/M for the state parameter ωq=−2/3 when the static observer at ro=5M in the domain of outer communication.