Photon ring polarimetry with next-generation black hole imaging I. M87*

Abstract

The near-horizon region of a black hole impacts linear (LP) and circular polarization (CP) through strong lensing of photons, adding large-scale symmetries and anti-symmetries to the polarized image. To probe the signature of lensing in polarimetry, we utilise a geometric model of concentric, Gaussian rings of equal radius to investigate the transition in the Fourier plane at which the photon ring signal begins to dominate over the direct image. We find analytic, closed-form expressions for the transition radii in total intensity, LP, and CP, wherein the resultant formulae are composed of ratios of tunable image parameters, with the overall "scale" set primarily by the thickness of the direct image. Using these formulae, we compute the transition radii for time-averaged images of M87* simulations at 230 GHz, studying both Magnetically Arrested Disc (MAD) and Standard and Normal Evolution (SANE) configurations for various spin and electron heating models. We compare geometric values to radii obtained directly from the simulations through a coherent averaging scheme. We find that nearly all MAD models have a photon ring-dominated CP signal on long baselines shorter than the Earth diameter at 230 GHz. Across favored models for the M87* accretion flow identified by EHT polarimetric constraints, we quantify the sensitivity and antenna size requirements for the next-generation EHT and the Black Hole Explorer orbiter to detect these features. We find that the stringent requirements for CP favour explorations using long baselines on the ground, while LP remains promising on Earth-space baselines.

Accepted by ApJ

References in corpus (23)

• 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. IV. Imaging the Central Supermassive Black Hole
• First M87 Event Horizon Telescope Results. II. Array and Instrumentation
• First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass
• A ring-like accretion structure in M87 connecting its black hole and jet
• First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization
• Discriminating Accretion States via Rotational Symmetry in Simulated Polarimetric Images of M87
• The Black Hole Explorer: Motivation and Vision
• Reference Array and Design Consideration for the next-generation Event Horizon Telescope
• The Photon Ring in M87*
• Photon ring test of the Kerr hypothesis: Variation in the ring shape
• Black Hole Images as Tests of General Relativity: Effects of Plasma Physics
• Adaptive Analytical Ray Tracing of Black Hole Photon Rings
• Black Hole Polarimetry I: A Signature of Electromagnetic Energy Extraction
• Measuring the shape of a black hole photon ring
• Prediction for the interferometric shape of the first black hole photon ring
• How narrow is the M87* ring? II. A new geometric model
• Demonstrating Photon Ring Existence with Single-Baseline Polarimetry
• Relative depolarization of the black hole photon ring in GRMHD models of Sgr A* and M87*
• Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes
• Photon Ring Interferometric Signatures Beyond The Universal Regime

Cited by in corpus (2)

• Limiting the Yukawa Gravity through the Black Hole Shadows of Sgr A* and M87*
• Orbit design for mitigating interstellar scattering effects in Earth-space VLBI observations of Sgr A*