Black Hole Shadow Observations with Space-Ground Interferometers

Abstract

We consider the black hole (BH) shadow images which can be restored by data processing and image recovery procedures in future space Very Large Baseline Interferometry (VLBI) missions. For Kerr BHs with masses and coordinates of SgrA*, M87* and M31*, illuminated by light source behind them, we consider three kinds of observation: the ground-based interferometer (similar to the Event Horizon Telescope), space-ground interferometer with a satellite in geocentric orbit and space-ground interferometer with a satellite located in Lagrange point \(L_2\). The significant difference between the images produced by the ground-based telescope alone and the one of the space VLBI with an added low-orbit satellite is caused by both the increased baseline and the improved of (u,v) coverage. The near-Earth configuration of the radio interferometer for the observation of BH shadows is the most preferable for the BH shadow observations among considered cases. With further increasing the orbit radius up to the Lagrange point \(L_2\) the density of the (u,v) filling decreases and the results appear less reliable. Model images for all the cases are presented.