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

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

dc.contributor.author	Narayan, Ramesh
dc.contributor.author	Azulay Romero, Rebecca Sarah
dc.contributor.author	Martí Vidal, Iván
dc.contributor.author	Mus, Alejandro
dc.contributor.author	EHT Collaboration
dc.date.accessioned	2022-05-24T14:17:13Z
dc.date.available	2022-05-24T14:17:13Z
dc.date.issued	2021
dc.identifier.citation	Narayan, Ramesh Azulay Romero, Rebecca Sarah Martí Vidal, Iván Mus, Alejandro EHT Collaboration 2021 The Polarized Image of a Synchrotron-emitting Ring of Gas Orbiting a Black Hole Astrophysical Journal 912 1 35
dc.identifier.uri	https://hdl.handle.net/10550/82967
dc.description.abstract	Synchrotron radiation from hot gas near a black hole results in a polarized image. The image polarization is determined by effects including the orientation of the magnetic field in the emitting region, relativistic motion of the gas, strong gravitational lensing by the black hole, and parallel transport in the curved spacetime. We explore these effects using a simple model of an axisymmetric, equatorial accretion disk around a Schwarzschild black hole. By using an approximate expression for the null geodesics derived by Beloborodov and conservation of the Walker-Penrose constant, we provide analytic estimates for the image polarization. We test this model using currently favored general relativistic magnetohydrodynamic simulations of M87, using ring parameters given by the simulations. For a subset of these with modest Faraday effects, we show that the ring model broadly reproduces the polarimetric image morphology. Our model also predicts the polarization evolution for compact flaring regions, such as those observed from Sgr A with GRAVITY. With suitably chosen parameters, our simple model can reproduce the EVPA pattern and relative polarized intensity in Event Horizon Telescope images of M87*. Under the physically motivated assumption that the magnetic field trails the fluid velocity, this comparison is consistent with the clockwise rotation inferred from total intensity images.
dc.language.iso	eng
dc.relation.ispartof	Astrophysical Journal, 2021, vol. 912, num. 1, p. 35
dc.subject	Astrofísica
dc.subject	Camps magnètics
dc.title	The Polarized Image of a Synchrotron-emitting Ring of Gas Orbiting a Black Hole
dc.type	journal article	es_ES
dc.date.updated	2022-05-24T14:17:13Z
dc.identifier.doi	10.3847/1538-4357/abf117
dc.identifier.idgrec	153673
dc.rights.accessRights	open access	es_ES