Shapes of Black Hole Shadows in Accretion Disks

Can we determine the spin parameters of black holes by observations of black hole shadows in accretion disks? In order to answer this question, we have investigated the shapes and positions of black hole shadows in optically thick accretion disks around Kerr black holes. In conclusion, in order to measure black hole spin parameters from shapes and positions of black hole shadows, it is crucially important to determine the position of the center of mass of a black hole in the region of a black hole shadow.