The Polarized Image of a Synchrotron-emitting Ring of Gas Orbiting a Black Hole

Abstract

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Observational Signatures of Black Hole Accretion: Rotating vs. Spherical Flows with Tilted Magnetic Fields

“…For example, 𝛽 2 = 1 (−1) stands for purely radial (azimuthal) polarization, and 𝛽 2 = ± 𝑖 represents the intermediate states where the radial and azimuthal components are equal (see e.g. is by definition perpendicular to the magnetic field direction, here the fact that the simulated polarization pattern is too radial indicates that the magnetic field is probably too azimuthal (Narayan et al 2021). One striking result in Fig.…”

Electromagnetic signatures of strong-field gravity from accreting black holes

“…The latter has attracted renewed interest in the context of EHT measurements with the polarimetric resolution (Event Horizon Telescope Collab. et al, 2021;Narayan et al, 2021).…”

Polarized Image of Equatorial Emission in the Kerr Geometry

“…2 ) circular orbit of zero angular momentum with angular velocity ω s = ω(r s , θ s = π 2 ). 1 The tetrad that describes the ZAMO local rest frame consists of its fourvelocity u µ = e µ (t) (u µ u µ = −1) and three orthogonal unit spacelike vectors:…”

“…The description of polarized images in both Schwarzschild and Kerr is greatly simplified by conservation of the Penrose-Walker constant [32]. Recently, a simplified toy model of synchrotron emission around a Schwarzschild black hole was presented in [1], which took advantage of an additional simplification: an approximation developed by Beloborodov [33] with which the polarized image can be computed analytically. Here, we extend the toy model of [1] using tools developed in [34][35][36][37] to include the effects of spin by generalizing to the Kerr geometry, for which a Beloborodov-like approximation is not available.…”

“…Using analytic results in the Kerr geometry, we can model the effects of spin on the image of hotspot emission and generate images of Q, U time variation in direct and indirect images that reproduce observed polarization loops. Our model can be directly compared to simulated and observed values for the case of near-infrared flares, in which the influence of Faraday effects, absorption, and background emission are insignificant [1].…”