Black hole parameter estimation with synthetic Very Long Baseline Interferometry data from the ground and from space

Abstract

The Event Horizon Telescope (EHT) has imaged the shadow of the supermassive black hole in M87. A library of general relativistic magnetohydrodynamics (GMRHD) models was fit to the observational data, providing constraints on black hole parameters. We investigate how much better future experiments can realistically constrain these parameters and test theories of gravity. We generate realistic synthetic 230 GHz data from representative input models taken from a GRMHD image library for M87, using the 2017, 2021, and an expanded EHT array. The synthetic data are run through a data reduction pipeline used by the EHT. Additionally, we simulate 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 investigate how the black hole parameter estimations are affected by different arrays and repeated observations. 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. High-frequency observations from space rule out all but ~15% of the GRMHD models in our library, strongly constraining the magnetic flux and black hole spin. The 1$\sigma$ 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, which allows tests of deviations from general relativity. High-precision tests of the Kerr metric become within reach from observations of the Galactic Center black hole Sagittarius A*.

21 pages, 18 figures, accepted for publication in Astronomy & Astrophysics

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Cited by in corpus (17)

• Testing Horndeski Gravity from EHT Observational Results for Rotating Black Holes
• Estimating the cosmological constant from shadows of Kerr--de Sitter black holes
• Observational Signatures of Frame Dragging in Strong Gravity
• EHT observables as a tool to estimate parameters of supermassive black holes
• Testing the linear relationship between black hole mass and variability timescale in low-luminosity AGN at submillimeter wavelengths
• Measuring the Ellipticity of M 87* Images
• Impacts of nonthermal emission on the images of a black hole shadow and extended jets in two-temperature GRMHD simulations
• Imaging the event horizon of M87* from space on different timescales
• Deep learning inference with the Event Horizon Telescope I. Calibration improvements and a comprehensive synthetic data library
• On the Universality of Energy Extraction from Black Hole Spacetimes
• GALLIFRAY -- A geometric modeling and parameter estimation framework for black hole images using bayesian techniques
• The Core-shift of Sagittarius A* as a Discriminant between Disk and Jet Emission Models with millimeter-VLBI
• The science case and challenges of space-borne sub-millimeter interferometry
• The Nature of Black Hole Shadows
• Lunar Time Ephemeris $\text{LTE440}$: definitions, algorithm and performance
• PATOKA: Simulating Electromagnetic Observables of Black Hole Accretion
• Parameter Inference of Black Hole Images using Deep Learning in Visibility Space