A Parametric model for the shapes of black-hole shadows in non-Kerr spacetimes

Abstract

The Event Horizon Telescope (EHT) is taking the first images of black holes resolved at horizon scales to measure their shadows and probe accretion physics. A promising avenue for testing the hypothesis that astrophysical black holes are described by the Kerr solution to Einstein's equations is to compare the size and shape of the shadow a black hole casts on the surrounding emission to the predictions of the Kerr metric. We develop here an efficient parametric framework to perform this test. We carry out ray-tracing simulations for several parametrized non-Kerr metrics to create a large data set of non-Kerr shadows that probe the allowed parameter space for the free parameters of each metric. We then perform principal components analysis (PCA) on this set of shadows and show that only a small number of components are needed to accurately reconstruct all shadows within the set. We further show that the amplitude of the PCA components are smoothly related to the free parameters in the metrics, and therefore, that these PCA components can be fit to EHT observations in order to place constraints on the free parameters of these metrics that will help quantify any potential deviations from the Kerr solution.

arXiv commentNew figure added, new simulations run correcting typo in previous work, accepted to ApJ

References in corpus (36)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• Monitoring stellar orbits around the Massive Black Hole in the Galactic Center
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• Measuring Distance and Properties of the Milky Way's Central Supermassive Black Hole with Stellar Orbits
• Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole
• Shadows and strong gravitational lensing: a brief review
• Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum: II. Black-Hole Images
• A Metric for Rapidly Spinning Black Holes Suitable for Strong-Field Tests of the No-Hair Theorem
• A new method for shadow calculations: application to parameterised axisymmetric black holes
• Apparent shape of super-spinning black holes
• Mapping spacetimes with LISA: inspiral of a test-body in a `quasi-Kerr' field
• Null geodesics and shadow of a rotating black hole in extended Chern-Simons modified gravity
• The Current Ability to Test Theories of Gravity with Black Hole Shadows
• Shadows of spherically symmetric black holes and naked singularities
• General parametrization of axisymmetric black holes in metric theories of gravity
• Shadow of five-dimensional rotating Myers-Perry black hole
• Photon Rings around Kerr and Kerr-like Black Holes
• A coordinate-independent characterization of a black hole shadow
• Towards a formalism for mapping the spacetimes of massive compact objects: Bumpy black holes and their orbits
• Bumpy Black Holes in Alternate Theories of Gravity
• A Quantitative Test of the No-Hair Theorem with Sgr A* using stars, pulsars, and the Event Horizon Telescope
• An explanation of the Newman-Janis Algorithm
• Testing General Relativity with the Event Horizon Telescope
• Shape and position of the shadow in the $\delta =2$ Tomimatsu-Sato space-time
• Shadow casted by a Konoplya-Zhidenko rotating non-Kerr black hole
• Spacetime and orbits of bumpy black holes
• A General Relativistic Null Hypothesis Test with Event Horizon Telescope Observations of the black-hole shadow in Sgr A*
• Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum: I. Properties of a Quasi-Kerr Spacetime
• A Ray-Tracing Algorithm for Spinning Compact Object Spacetimes with Arbitrary Quadrupole Moments. I. Quasi-Kerr Black Holes
• GRay: a Massively Parallel GPU-Based Code for Ray Tracing in Relativistic Spacetimes
• On generic parametrizations of spinning black-hole geometries
• Systematic Study of Event Horizons and Pathologies of Parametrically Deformed Kerr Spacetimes
• Shadows of CPR black holes and tests of the Kerr metric
• Approximate Waveforms for Extreme-Mass-Ratio Inspirals in Modified Gravity Spacetimes
• Masses of Nearby Supermassive Black Holes with Very-Long Baseline Interferometry
• Exploring the Spectral Space of Low Redshift QSOs

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• Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A${}^{\ast }$
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• The Shape of the Black Hole Photon Ring: A Precise Test of Strong-Field General Relativity
• Observing the Inner Shadow of a Black Hole: A Direct View of the Event Horizon
• Photon rings of spherically symmetric black holes and robust tests of non-Kerr metrics
• Parameters estimation and strong gravitational lensing of nonsingular Kerr-Sen black holes
• Black Hole Images as Tests of General Relativity: Effects of Spacetime Geometry
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• Measuring Spin from Relative Photon Ring Sizes
• Photon ring test of the Kerr hypothesis: Variation in the ring shape
• Can supermassive black hole shadows test the Kerr metric?
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• Rotating Black Holes in Horndeski Gravity: Thermodynamic and Gravitational Lensing
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• Separating Astrophysics and Geometry in Black Hole Images
• Chaotic Shadows of Black Holes: A Short Review
• Black Hole Glimmer Signatures of Mass, Spin, and Inclination
• Probing the Black Hole Metric. I. Black Hole Shadows and Binary Black-Hole Inspirals
• On the approximation of the black hole shadow with a simple polar curve
• Brightness Asymmetry of Black Hole Images as a Probe of Observer Inclination
• Disformal transformation of stationary and axisymmetric solutions in modified gravity
• On Kerr black hole deformations admitting a Carter constant and an invariant criterion for the separability of the wave equation
• Generating Rotating Spacetime in Ricci-Based Gravity: Naked Singularity as a Black Hole Mimicker
• Is a black hole shadow a reliable test of the no-hair theorem?
• Chaotic photon orbits and shadows of a non-Kerr object described by the Hartle-Thorne spacetime
• Tidal forces in parametrized spacetime: Rezzolla-Zhidenko parametrization
• Measuring the Ellipticity of M 87* Images
• Principal-Component Interferometric Modeling (PRIMO), an Algorithm for EHT Data I: Reconstructing Images from Simulated EHT Observations
• Exploring departures from Schwarzschild black hole in $f(R)$ gravity
• Measuring Black Hole Light Echoes with Very Long Baseline Interferometry
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• Fractal signatures of non-Kerr spacetimes in the shadow of light-ring bifurcations
• Identifying the Event Horizons of Parametrically Deformed Black-Hole Metrics
• Determining parameters of Kerr-Newman black holes by shadow observation from finite distance and spatial infinity
• Light ring images of double photon spheres in black hole and wormhole space-times
• PATOKA: Simulating Electromagnetic Observables of Black Hole Accretion
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