Relative depolarization of the black hole photon ring in GRMHD models of Sgr A* and M87*. Issue 3 (22nd March 2021)

• Record Type: Journal Article
• Authors: Jiménez-Rosales, A; Dexter, J; Ressler, S M; Tchekhovskoy, A; Bauböck, M; Dallilar, Y; de Zeeuw, P T; Drescher, A; Eisenhauer, F; von Fellenberg, S; Gao, F; Genzel, R; Gillessen, S; Habibi, M; Ott, T; Stadler, J; Straub, O; Widmann, F
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 503:Issue 3(2021)
• Page Start: 4563
• Page End: 4575
• Publication Date: 2021-03-22
• Subjects: accretion, accretion discs -- black hole physics -- MHD -- polarization -- radiative transfer; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab784
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Using general relativistic magnetohydrodynamic simulations of accreting black holes, we show that a suitable subtraction of the linear polarization per pixel from total intensity images can enhance the photon ring feature. We find that the photon ring is typically a factor of ≃2 less polarized than the rest of the image. This is due to a combination of plasma and general relativistic effects, as well as magnetic turbulence. When there are no other persistently depolarized image features, adding the subtracted residuals over time results in a sharp image of the photon ring. We show that the method works well for sample, viable GRMHD models of Sgr A* and M87*, where measurements of the photon ring properties would provide new measurements of black hole mass and spin, and potentially allow for tests of the 'no-hair' theorem of general relativity.