Shadow and photon sphere of black hole in clouds of strings and quintessence *

Abstract

Abstract In this study, we investigate the shadow and photon sphere of the black bole in clouds of strings and quintessence with static and infalling spherical accretions. We obtain the geodesics of the photons near a black hole with different impact parameters b to investigate how the string cloud model and quintessence influence the specific intensity by altering the geodesic and the average radial position of photons. In addition, the range of the string cloud parameter a is constrained to ensure that a shadow can be observed. Moreover, the light sources in the accretion follow a normal distribution with an attenuation factor γ, and we adopt a model of the photon emissivity to obtain the specific intensities. Furthermore, the shadow with static spherical accretion is plotted, which demonstrates that the apparent shape of the shadow is a perfect circle, and the value of γ influences the brightness of the photon sphere. Subsequently, we investigate the profile and specific intensity of the shadows with static and infalling spherical accretions, respectively. The interior of the shadows with an infalling spherical accretion will be darker than that with the static spherical accretion, and the specific intensity with both static and infalling spherical accretions gradually converges.