TY - JOUR
T1 - Black Hole Images as Tests of General Relativity
T2 - Effects of Plasma Physics
AU - Özel, Feryal
AU - Psaltis, Dimitrios
AU - Younsi, Ziri
N1 - Funding Information:
D.P. and F.O. acknowledge support from NSF PIRE award OISE-1743747, NSF AST-1715061, and NASA ATP award 80NSSC20K0521. Z.Y. is supported by a UK Research & Innovation (UKRI) Stephen Hawking Fellowship and acknowledges partial support from a Leverhulme Trust Early Career Fellowship. We thank Monika Mościbrodzka and Ramesh Narayan for detailed comments on the manuscript. We also thank Lia Medeiros, Mariafelicia de Laurentis, and all members of the Gravitational Physics Working Group of the EHT, for helpful discussions and comments. We thank the anonymous referee for a careful reading of the manuscript and valuable comments. This research has made use of NASA’s Astrophysics Data System.
Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.
PY - 2022/12/1
Y1 - 2022/12/1
N2 - The horizon-scale images of black holes obtained with the Event Horizon Telescope have provided new probes of their metrics and tests of general relativity. The images are characterized by a bright, near-circular ring from the gravitationally lensed emission from the hot plasma and a deep central depression cast by the black hole. The metric tests rely on the fact that the bright ring closely traces the boundary of the black hole shadow with a small displacement that has been quantified using simulations. In this paper we develop a self-consistent covariant analytic model of the accretion flow that spans a broad range of plasma conditions and black hole properties to explore the general validity of this result. We show that, for any physical model of the accretion flow, the ring always encompasses the outline of the shadow and is not displaced by it by more than half the ring width. This result is a consequence of conservation laws and basic thermodynamic considerations and does not depend on the microphysics of the plasma or the details of the numerical simulations. We also present a quantitative measurement of the bias between the bright ring and the shadow radius based on the analytical models.
AB - The horizon-scale images of black holes obtained with the Event Horizon Telescope have provided new probes of their metrics and tests of general relativity. The images are characterized by a bright, near-circular ring from the gravitationally lensed emission from the hot plasma and a deep central depression cast by the black hole. The metric tests rely on the fact that the bright ring closely traces the boundary of the black hole shadow with a small displacement that has been quantified using simulations. In this paper we develop a self-consistent covariant analytic model of the accretion flow that spans a broad range of plasma conditions and black hole properties to explore the general validity of this result. We show that, for any physical model of the accretion flow, the ring always encompasses the outline of the shadow and is not displaced by it by more than half the ring width. This result is a consequence of conservation laws and basic thermodynamic considerations and does not depend on the microphysics of the plasma or the details of the numerical simulations. We also present a quantitative measurement of the bias between the bright ring and the shadow radius based on the analytical models.
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U2 - 10.3847/1538-4357/ac9fcb
DO - 10.3847/1538-4357/ac9fcb
M3 - Article
AN - SCOPUS:85145306349
SN - 0004-637X
VL - 941
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 88
ER -