Simulations of M87 and Sgr A* Imaging with the Millimetron Space Observatory on near-Earth orbits

Abstract

High resolution imaging of supermassive black holes shadows is a direct way to verify the theory of general relativity at extreme gravity conditions. Very Long Baseline Interferometry (VLBI) observations at millimeter/sub-millimeter wavelengths can provide such angular resolution for supermassive black holes, located in Sgr A* and M87. Recent VLBI observations of M87 with the Event Horizon Telescope (EHT) has shown such capabilities. The maximum obtainable spatial resolution of EHT is limited by Earth diameter and atmospheric phase variations. In order to improve the image resolution longer baselines are required. Radioastron space mission has successfully demonstrated the capabilities of Space-Earth VLBI with baselines much larger than Earth diameter. Millimetron is a next space mission of the Russian Space Agency that will operate at millimeter wavelengths. Nominal orbit of the observatory will be located around Lagrangian L2 point of the Sun-Earth system. In order to optimize the VLBI mode, we consider a possible second stage of the mission that could use near-Earth high elliptical orbit (HEO). In this contribution a set of near Earth orbits is used for the synthetic space-ground VLBI observations of Sgr A* and M87 in joint Millimetron and EHT configuration. General-relativistic magnetohydrodynamic models (GRMHD) for black hole environment of Sgr A* and M87 are used for static and dynamic imaging simulations at 230 GHz. A comparison is made between ground and space-ground baselines. It demonstrates that joined observations with Millimetron and EHT facilities significantly improve the image resolution and allow obtaining the dynamic snapshot images of Sgr A*.

Analytical perturbations of relativistic images in Kerr space-time

“…While higher-order images remain beyond the observational capabilities of current interferometry with terrestrial baselines, some projects aiming for the extension of very long baseline interferometry technique (VLBI) seem feasible within the next decade [29][30][31][32]. They predict that (sub)millimeter interferometric observations with ≃ 0.1 µas resolution and ≃ 1 µJy sensitivity could access more than a million supermassive black hole shadows and even the first and second-order photon rings.…”