Separating Astrophysics and Geometry in Black Hole Images

Abstract

The observation of the shadow of the supermassive black hole M87${}^{\ast }$ by the Event Horizon Telescope (EHT) is sensitive to the spacetime geometry near the circular photon orbit and beyond, and it thus has the potential to test general relativity in the strong field regime. Obstacles to this program, however, include degeneracies between putative deviations from general relativity and both the description of the accretion flow and the uncertainties on "calibration parameters", such as e.g. the mass and spin of the black hole. In this work, we introduce a formalism, based on a principal component analysis, capable of reconstructing the black hole metric (i.e. the "signal") in an agnostic way, while subtracting the "foreground" due to the uncertainties in the calibration parameters and the modelling of the accretion flow. We apply our technique to simulated mock data for spherically symmetric black holes surrounded by a thick accretion disk. We show that separation of signal and foreground may be possible with next generation EHT-like experiments.

12 pages, 3 figures, Minor changes, Published Version

References in corpus (16)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• Black Hole Shadows, Photon Rings, and Lensing Rings
• Constraints on black-hole charges with the 2017 EHT observations of M87*
• Gravitational Test Beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole
• A new method for shadow calculations: application to parameterised axisymmetric black holes
• Spontaneously scalarised Kerr black holes
• Quasinormal-mode spectrum of Kerr black holes and its geometric interpretation
• New parametrization for spherically symmetric black holes in metric theories of gravity
• Shadows of Einstein-dilaton-Gauss-Bonnet black holes
• The BayesWave analysis pipeline in the era of gravitational wave observations
• When is g_{tt} g_{rr} = -1?
• The Inverse Problem for Hawking Radiation
• Theory-agnostic tests of gravity with black hole shadows

Cited by in corpus (12)

• Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A${}^{\ast }$
• Shadows of boson and Proca stars with thin accretion disks
• Black Hole Images as Tests of General Relativity: Effects of Spacetime Geometry
• An Upper Limit on the Charge of the Black Hole Sgr A* from EHT Observations
• Kerr black holes with synchronised Proca hair: lensing, shadows and EHT constraints
• Adaptive Analytical Ray Tracing of Black Hole Photon Rings
• Spherical accretion in alternative theories of gravity
• Effects of Born-Infeld electrodynamics on black hole shadows
• Multi-level images around Kerr-Newman black holes
• Eikonal quasinormal modes and photon orbits of deformed Schwarzschild black holes
• A parametrized quasi-normal mode framework for non-Schwarzschild metrics
• Multi-ring images of thin accretion disk of a regular naked compact object