TY - JOUR
T1 - First Sagittarius A∗ Event Horizon Telescope Results. VIII. Physical Interpretation of the Polarized Ring
AU - The Event Horizon Telescope Collaboration
AU - Akiyama, Kazunori
AU - Alberdi, Antxon
AU - Alef, Walter
AU - Algaba, Juan Carlos
AU - Anantua, Richard
AU - Asada, Keiichi
AU - Azulay, Rebecca
AU - Bach, Uwe
AU - Baczko, Anne Kathrin
AU - Ball, David
AU - Baloković, Mislav
AU - Bandyopadhyay, Bidisha
AU - Barrett, John
AU - Bauböck, Michi
AU - Benson, Bradford A.
AU - Bintley, Dan
AU - Blackburn, Lindy
AU - Blundell, Raymond
AU - Bouman, Katherine L.
AU - Bower, Geoffrey C.
AU - Boyce, Hope
AU - Bremer, Michael
AU - Brinkerink, Christiaan D.
AU - Brissenden, Roger
AU - Britzen, Silke
AU - Broderick, Avery E.
AU - Broguiere, Dominique
AU - Bronzwaer, Thomas
AU - Bustamante, Sandra
AU - Byun, Do Young
AU - Carlstrom, John E.
AU - Ceccobello, Chiara
AU - Chael, Andrew
AU - Chan, Chi Kwan
AU - Chang, Dominic O.
AU - Chatterjee, Koushik
AU - Chatterjee, Shami
AU - Chen, Ming Tang
AU - Chen, Yongjun
AU - Cheng, Xiaopeng
AU - Cho, Ilje
AU - Christian, Pierre
AU - Conroy, Nicholas S.
AU - Conway, John E.
AU - Cordes, James M.
AU - Ford, H. Alyson
AU - Jannuzi, Buell T.
AU - Marrone, Daniel P.
AU - Psaltis, Dimitrios
AU - Tilanus, Remo P.J.
N1 - Publisher Copyright:
© 2024 American Astronomical Society. All rights reserved.
PY - 2024/4/1
Y1 - 2024/4/1
N2 - In a companion paper, we present the first spatially resolved polarized image of Sagittarius A∗ on event horizon scales, captured using the Event Horizon Telescope, a global very long baseline interferometric array operating at a wavelength of 1.3 mm. Here we interpret this image using both simple analytic models and numerical general relativistic magnetohydrodynamic (GRMHD) simulations. The large spatially resolved linear polarization fraction (24%-28%, peaking at ∼40%) is the most stringent constraint on parameter space, disfavoring models that are too Faraday depolarized. Similar to our studies of M87∗, polarimetric constraints reinforce a preference for GRMHD models with dynamically important magnetic fields. Although the spiral morphology of the polarization pattern is known to constrain the spin and inclination angle, the time-variable rotation measure (RM) of Sgr A∗ (equivalent to ≈ 46° ± 12° rotation at 228 GHz) limits its present utility as a constraint. If we attribute the RM to internal Faraday rotation, then the motion of accreting material is inferred to be counterclockwise, contrary to inferences based on historical polarized flares, and no model satisfies all polarimetric and total intensity constraints. On the other hand, if we attribute the mean RM to an external Faraday screen, then the motion of accreting material is inferred to be clockwise, and one model passes all applied total intensity and polarimetric constraints: a model with strong magnetic fields, a spin parameter of 0.94, and an inclination of 150°. We discuss how future 345 GHz and dynamical imaging will mitigate our present uncertainties and provide additional constraints on the black hole and its accretion flow.
AB - In a companion paper, we present the first spatially resolved polarized image of Sagittarius A∗ on event horizon scales, captured using the Event Horizon Telescope, a global very long baseline interferometric array operating at a wavelength of 1.3 mm. Here we interpret this image using both simple analytic models and numerical general relativistic magnetohydrodynamic (GRMHD) simulations. The large spatially resolved linear polarization fraction (24%-28%, peaking at ∼40%) is the most stringent constraint on parameter space, disfavoring models that are too Faraday depolarized. Similar to our studies of M87∗, polarimetric constraints reinforce a preference for GRMHD models with dynamically important magnetic fields. Although the spiral morphology of the polarization pattern is known to constrain the spin and inclination angle, the time-variable rotation measure (RM) of Sgr A∗ (equivalent to ≈ 46° ± 12° rotation at 228 GHz) limits its present utility as a constraint. If we attribute the RM to internal Faraday rotation, then the motion of accreting material is inferred to be counterclockwise, contrary to inferences based on historical polarized flares, and no model satisfies all polarimetric and total intensity constraints. On the other hand, if we attribute the mean RM to an external Faraday screen, then the motion of accreting material is inferred to be clockwise, and one model passes all applied total intensity and polarimetric constraints: a model with strong magnetic fields, a spin parameter of 0.94, and an inclination of 150°. We discuss how future 345 GHz and dynamical imaging will mitigate our present uncertainties and provide additional constraints on the black hole and its accretion flow.
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U2 - 10.3847/2041-8213/ad2df1
DO - 10.3847/2041-8213/ad2df1
M3 - Article
AN - SCOPUS:85189437378
SN - 2041-8205
VL - 964
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L26
ER -