Black Hole Shadow Observations with Space-Ground Interferometers

The study explores black hole (BH) shadow images which can be restored by data processing and image recovery procedures during space Very Large Baseline Interferometry (VLBI) missions in the future. For Kerr BHs with masses and coordinates of SgrA*, M87*, and M31*, all illuminated by a light source behind them, three kinds of observation are considered: 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 one from the space VLBI with an added low-orbit satellite is caused by both the increased baseline and the improved $$(u,{v})$$ coverage. The near-Earth configuration of the radio interferometer for BH shadow observations is the most preferable among the considered cases. As the orbit radius increases 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.