Photon Ring Symmetries in Simulated Linear Polarization Images of Messier 87*

Abstract

The Event Horizon Telescope (EHT) recently released the first linearly polarized images of the accretion flow around the supermassive black hole Messier 87*, hereafter \m{}. The spiraling polarization pattern found in EHT images favored magnetically arrested disks (MADs) as the explanation for the EHT image. With next-generation improvements to very long baseline interferometry (VLBI) on the horizon, understanding similar polarized features in the highly lensed structure known as the "photon ring," where photons make multiple half-orbits about the black hole before reaching the observer, will be critical to analysis of future images. Recent work has indicated that this image region may be depolarized relative to more direct emission. We expand this observation by decomposing photon half-orbits in the EHT library of simulated images of the \m{} accretion system and find that images of MAD simulations show a relative depolarization of the photon ring attributable to destructive interference of oppositely spiraling electric field vectors; this antisymmetry, which arises purely from strong gravitational lensing, can produce up to $\sim 50\%$ depolarization in the photon ring region with respect to the direct image. In systems that are not magnetically arrested and with the exception of systems with high spin and ions and electrons of equal temperature, we find that highly lensed indirect sub-images are almost completely depolarized, causing a modest depolarization of the photon ring region in the complete image. We predict that next-generation EHT observations of \m{} polarization should jointly constrain the black hole spin and the underlying emission and magnetic field geometry.

Accepted to ApJ. 11 pages, 4 figures

References in corpus (23)

• Array Programming with NumPy
• 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. IV. Imaging the Central Supermassive Black Hole
• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• First M87 Event Horizon Telescope Results. II. Array and Instrumentation
• First M87 Event Horizon Telescope Results. III. Data Processing and Calibration
• First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon
• First M87 Event Horizon Telescope Results. VII. Polarization of the Ring
• Universal Interferometric Signatures of a Black Hole's Photon Ring
• Lensing by Kerr Black Holes
• Observing the Inner Shadow of a Black Hole: A Direct View of the Event Horizon
• The Null Geodesics of the Kerr Exterior
• Universal Polarimetric Signatures of the Black Hole Photon Ring
• Evaluation of New Submillimeter VLBI Sites for the Event Horizon Telescope
• The Polarized Image of a Synchrotron Emitting Ring of Gas Orbiting a Black Hole
• Polarized Image of Equatorial Emission in the Kerr Geometry
• Discriminating Accretion States via Rotational Symmetry in Simulated Polarimetric Images of M87
• Iharm3D: Vectorized General Relativistic Magnetohydrodynamics
• Black Hole Magnetic Fields and Their Imprint on Circular Polarization Images
• The Jet-Disk Boundary Layer in Black Hole Accretion
• Unraveling circular polarimetric images of magnetically arrested accretion flows near event horizon of a black hole
• Relative depolarization of the black hole photon ring in GRMHD models of Sgr A* and M87*

Cited by in corpus (1)

• How Spatially Resolved Polarimetry Informs Black Hole Accretion Flow Models