First Space-VLBI Observations of Sagittarius A*

Johnson, Michael D. and Kovalev, Yuri Y. and Lisakov, Mikhail M. and Voitsik, Petr A. and Gwinn, Carl R. and Bruni, Gabriele (2021) First Space-VLBI Observations of Sagittarius A*. The Astrophysical Journal Letters, 922 (2). L28. ISSN 2041-8205

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Abstract

We report results from the first Earth-space VLBI observations of the Galactic Center supermassive black hole, Sgr A*. These observations used the space telescope Spektr-R of the RadioAstron project together with a global network of 20 ground telescopes, observing at a wavelength of 1.35 cm. Spektr-R provided baselines up to 3.9 times the diameter of the Earth, corresponding to an angular resolution of approximately 55 μas and a spatial resolution of 5.5RSch at the source, where RSch ≡ 2GM/c2 is the Schwarzschild radius of Sgr A*. Our short ground baseline measurements ( ≲ 80 Mλ) are consistent with an anisotropic Gaussian image, while our intermediate ground baseline measurements (100–250 Mλ) confirm the presence of persistent image substructure in Sgr A*. Both features are consistent with theoretical expectations for strong scattering in the ionized interstellar medium, which produces Gaussian scatter-broadening on short baselines and refractive substructure on long baselines. We do not detect interferometric fringes on any of the longer ground baselines or on any ground–space baselines. While space-VLBI offers a promising pathway to sharper angular resolution and the measurement of key gravitational signatures in black holes, such as their photon rings, our results demonstrate that space-VLBI studies of Sgr A* will require sensitive observations at submillimeter wavelengths.

Item Type: Article
Subjects: Middle Asian Archive > Physics and Astronomy
Depositing User: Managing Editor
Date Deposited: 04 May 2023 07:31
Last Modified: 24 Jul 2025 05:43
URI: http://peerreview.go2articles.com/id/eprint/412

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