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Black hole parameter estimation with synthetic very long baseline interferometry data from the ground and from space

Roelofs, F; Fromm, CM; Mizuno, Y; Davelaar, J; Janssen, M; Younsi, Z; Rezzolla, L; (2021) Black hole parameter estimation with synthetic very long baseline interferometry data from the ground and from space. Astronomy & Astrophysics , 650 , Article A56. 10.1051/0004-6361/202039745. Green open access

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Abstract

Context. The Event Horizon Telescope (EHT) has imaged the shadow of the supermassive black hole in M 87. A library of general relativistic magnetohydrodynamics (GMRHD) models was fit to the observational data, providing constraints on black hole parameters. Aims. We investigate how much better future experiments can realistically constrain these parameters and test theories of gravity. Methods. We generated realistic synthetic 230 GHz data from representative input models taken from a GRMHD image library for M 87, using the 2017, 2021, and an expanded EHT array. The synthetic data were run through an automated data reduction pipeline used by the EHT. Additionally, we simulated observations at 230, 557, and 690 GHz with the Event Horizon Imager (EHI) Space VLBI concept. Using one of the EHT parameter estimation pipelines, we fit the GRMHD library images to the synthetic data and investigated how the black hole parameter estimations are affected by different arrays and repeated observations. Results. Repeated observations play an important role in constraining black hole and accretion parameters as the varying source structure is averaged out. A modest expansion of the EHT already leads to stronger parameter constraints in our simulations. High-frequency observations from space with the EHI rule out all but ∼15% of the GRMHD models in our library, strongly constraining the magnetic flux and black hole spin. The 1σ constraints on the black hole mass improve by a factor of five with repeated high-frequency space array observations as compared to observations with the current ground array. If the black hole spin, magnetization, and electron temperature distribution can be independently constrained, the shadow size for a given black hole mass can be tested to ∼0.5% with the EHI space array, which allows tests of deviations from general relativity. With such a measurement, high-precision tests of the Kerr metric become within reach from observations of the Galactic Center black hole Sagittarius A*.

Type: Article
Title: Black hole parameter estimation with synthetic very long baseline interferometry data from the ground and from space
Open access status: An open access version is available from UCL Discovery
DOI: 10.1051/0004-6361/202039745
Publisher version: http://dx.doi.org/10.1051/0004-6361/202039745
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: galaxies: nuclei – black hole physics – telescopes – atmospheric effects – techniques: high angular resolution – techniques: interferometric
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10129385
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