Possibility of Observing Photon Rings Using High-Frequency Space Radio Interferometry with Very Long Bases

In the paper, the possibility of observing photon rings in the close vicinity of supermassive black holes using space very long baseline radio interferometry at a frequency of 600 GHz has been examined. The 600-GHz range is promising for such observations by very long baseline radio interferometry because high frequency reduces the contribution of radio emission scattering by the interstellar medium and also makes it possible to increase the angular resolution of the interferometer. High angular resolution and low scattering, in turn, have suggested the possible detection of photon rings in the close vicinity of supermassive black holes. To estimate these possibilities, modeling of the visibility amplitude distribution from the baseline projection has been performed, taking into account various possible sensitivity parameters of the interferometer. Based on the results, the prospects for the 600-GHz range in terms of observing photon rings have been shown. In addition, the requirements for the on-board receiving complex of a space interferometer have been formulated, at which detection of photon rings is feasible.