Observational distinguishability of the Kerr and Kerr-Hayward metrics to EHT

Abstract

Astrophysical black holes appear well-represented by the Kerr metric, whose maximal analytic extension contains a ringlike curvature singularity. We study a phenomenological regularized modification of Kerr, the modified Kerr-Hayward metric, which removes curvature blowup at the level of the stationary metric while preserving in detail many features of polarized black hole images now testable by the Event Horizon Telescope (EHT). To establish this, we produce new general relativistic magnetohydrodynamics (GRMHD) simulations of a magnetized plasma in a Kerr-Hayward spacetime, then we extend the EHT analysis framework to perform polarized radiative transfer in this spacetime. We detail our methodology for implementing this modified spacetime into an open-source pipeline. From fluid quantities such as the magnetic flux parameter and jet efficiency, to image quantities such as the polarization pattern and the photon ring structure, our results for the Kerr-Hayward metric appear functionally indistinguishable from the Kerr metric. Our study finds that under the assumptions of a fixed-background GRMHD and polarized radiative transfer pipeline, this regularized phenomenological modification to the Kerr metric can yield observables that are effectively indistinguishable in EHT measurements.

19 pages, 6 figures

References in corpus (39)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• 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
• First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon
• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• Black Hole Shadows, Photon Rings, and Lensing Rings
• First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole
• Rotating regular black holes
• Generating rotating regular black hole solutions without complexification
• 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
• Observing the Inner Shadow of a Black Hole: A Direct View of the Event Horizon
• Can the EHT M87 results be used to test general relativity?
• First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization
• Polarized Image of Equatorial Emission in the Kerr Geometry
• On the Observable Shape of Black Hole Photon Rings
• Discriminating Accretion States via Rotational Symmetry in Simulated Polarimetric Images of M87
• Black Hole Images as Tests of General Relativity: Effects of Spacetime Geometry
• Reference Array and Design Consideration for the next-generation Event Horizon Telescope
• Towards a Non-singular Paradigm of Black Hole Physics
• Geodesic incompleteness of some popular regular black holes
• Distinguishing gravitational and emission physics in black-hole imaging: spherical symmetry
• Black Hole Images as Tests of General Relativity: Effects of Plasma Physics
• Decomposing the Internal Faraday Rotation of Black Hole Accretion Flows
• Black Hole Polarimetry I: A Signature of Electromagnetic Energy Extraction
• Measuring the shape of a black hole photon ring
• How narrow is the M87* ring? II. A new geometric model
• Using Machine Learning to Link Black Hole Accretion Flows with Spatially Resolved Polarimetric Observables
• Probing spacetime and accretion model for the Galactic Center: Comparison of Kerr and dilaton black hole shadows
• Brightness Asymmetry of Black Hole Images as a Probe of Observer Inclination
• Horizon-scale variability of M87* from 2017--2021 EHT observations
• Toward General-Relativistic Magnetohydrodynamics Simulations in Stationary Non-Vacuum Spacetimes
• Adiabatic Index in Fluid Models of Collisionless Black Hole Accretion
• The future ability to test theories of gravity with black-hole shadows
• Bayesian Black Hole Photogrammetry
• Spacetime Measurements with the Photon Ring
• Self-Gravitating Matter in Stationary and Axisymmetric Black Hole Spacetimes
• On the Universality of Energy Extraction from Black Hole Spacetimes