First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole

Abstract

Abstract We present measurements of the properties of the central radio source in M87 using Event Horizon Telescope data obtained during the 2017 campaign. We develop and fit geometric crescent models (asymmetric rings with interior brightness depressions) using two independent sampling algorithms that consider distinct representations of the visibility data. We show that the crescent family of models is statistically preferred over other comparably complex geometric models that we explore. We calibrate the geometric model parameters using general relativistic magnetohydrodynamic (GRMHD) models of the emission region and estimate physical properties of the source. We further fit images generated from GRMHD models directly to the data. We compare the derived emission region and black hole parameters from these analyses with those recovered from reconstructed images. There is a remarkable consistency among all methods and data sets. We find that >50% of the total flux at arcsecond scales comes from near the horizon, and that the emission is dramatically suppressed interior to this region by a factor >10, providing direct evidence of the predicted shadow of a black hole. Across all methods, we measure a crescent diameter of 42 ± 3 μ as and constrain its fractional width to be <0.5. Associating the crescent feature with the emission surrounding the black hole shadow, we infer an angular gravitational radius of GM / Dc 2 = 3.8 ± 0.4 μ as. Folding in a distance measurement of gives a black hole mass of . This measurement from lensed emission near the event horizon is consistent with the presence of a central Kerr black hole, as predicted by the general theory of relativity.

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Affiliated Institutions

• National Sun Yat-sen University TW
• Harvard University US
• Institute of Astronomy and Astrophysics, Academia Sinica TW
• California Institute of Technology US
• Rhodes University ZA
• Universitat de València ES
• Netherlands Institute for Radio Astronomy NL
• National Institute of Astrophysics, Optics and Electronics MX
• University of Groningen NL
• Fermi National Accelerator Laboratory US
• University of Amsterdam NL
• Parc Científic de la Universitat de València ES
• Perimeter Institute CA
• University of Illinois Urbana-Champaign US
• Chinese Academy of Sciences CN
• University of Arizona US
• Nanjing University CN
• East Asian Observatory US
• Massachusetts Institute of Technology US
• Shanghai Astronomical Observatory CN
• Cornell University US
• Woodwell Climate Research Center US
• Kitt Peak National Observatory US
• Goethe University Frankfurt DE
• Nederlandse Onderzoekschool Voor Astronomie
• Instituto de Astrofísica de Andalucía ES
• National Radio Astronomy Observatory US
• Institut de Radioastronomie Millimétrique FR
• Institute of High Energy Physics CN
• Chalmers University of Technology SE
• Korea University of Science and Technology KR
• Boston University US
• Leiden University NL
• Kogakuin University JP
• Kavli Institute for the Physics and Mathematics of the Universe JP
• Peking University CN
• Center for Astrophysics Harvard & Smithsonian US
• University of Chicago US
• University of Waterloo CA
• Joint Institute for VLBI ERIC NL
• University of Pretoria ZA
• Korea Astronomy and Space Science Institute KR
• Max Planck Institute for Radio Astronomy DE
• The Graduate University for Advanced Studies, SOKENDAI JP
• St Petersburg University RU
• Kavli Institute for Theoretical Sciences CN
• Istituto Nazionale di Fisica Nucleare, Sezione di Napoli IT
• Max Planck Institute for Extraterrestrial Physics DE
• The Institute of Statistical Mathematics JP
• The University of Tokyo JP
• National Astronomical Observatory of Japan JP
• Radboud University Nijmegen NL

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