First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon
Abstract
Abstract Event Horizon Telescope (EHT) observations at 230 GHz have now imaged polarized emission around the supermassive black hole in M87 on event-horizon scales. This polarized synchrotron radiation probes the structure of magnetic fields and the plasma properties near the black hole. Here we compare the resolved polarization structure observed by the EHT, along with simultaneous unresolved observations with the Atacama Large Millimeter/submillimeter Array, to expectations from theoretical models. The low fractional linear polarization in the resolved image suggests that the polarization is scrambled on scales smaller than the EHT beam, which we attribute to Faraday rotation internal to the emission region. We estimate the average density n e ∼ 10 4–7 cm −3 , magnetic field strength B ∼ 1–30 G, and electron temperature T e ∼ (1–12) × 10 10 K of the radiating plasma in a simple one-zone emission model. We show that the net azimuthal linear polarization pattern may result from organized, poloidal magnetic fields in the emission region. In a quantitative comparison with a large library of simulated polarimetric images from general relativistic magnetohydrodynamic (GRMHD) simulations, we identify a subset of physical models that can explain critical features of the polarimetric EHT observations while producing a relativistic jet of sufficient power. The consistent GRMHD models are all of magnetically arrested accretion disks, where near-horizon magnetic fields are dynamically important. We use the models to infer a mass accretion rate onto the black hole in M87 of (3–20) × 10 −4 M ⊙ yr −1 .
Funding
- National Science Foundation
- Smithsonian Institution
- U.S. Department of Energy
- National Aeronautics and Space Administration
- John Templeton Foundation
- Gordon and Betty Moore Foundation
- Harvard University
- University of Chicago
- University of Arizona
- Compute Canada
- Space Telescope Science Institute
- Ministerio de Ciencia, Innovación y Universidades
- National Radio Astronomy Observatory
- Associated Universities
- International Max Planck Research School for Environmental, Cellular and Molecular Microbiology
- Flatiron Health
- Government of Canada
- Leverhulme Trust
- European Commission
- National Research Foundation
- Ministry of Education, Culture, Sports, Science and Technology
- Universiteit Leiden
- National Natural Science Foundation of China
- Universiteit van Amsterdam
- Radboud Universiteit
- Academia Sinica
- Chinese Academy of Sciences
- China Postdoctoral Science Foundation
- Consejo Nacional de Ciencia y Tecnología
- Nederlandse Organisatie voor Wetenschappelijk Onderzoek
- Ministerio de Economía y Competitividad
- Generalitat Valenciana
- Nuclear Safety and Security Commission
- Korea Astronomy and Space Science Institute
- National Research Foundation of Korea
- Max-Planck-Gesellschaft
- Vetenskapsrådet
- China Scholarship Council
- European Southern Observatory
- Centre National de la Recherche Scientifique
- Ministerio de Ciencia e Innovación
- Universidad Nacional Autónoma de México
- National Astronomical Observatory of Japan
- Junta de Andalucía
- Istituto Nazionale di Fisica Nucleare
- Instituto de Astrofísica de Andalucía
- Agencia Nacional de Investigación y Desarrollo
- Institut Périmètre de physique théorique
- East Asian Core Observatories Association
- Toray Science Foundation
- Office of Science
- National Nuclear Security Administration
- Natural Sciences and Engineering Research Council of Canada
- Japan Society for the Promotion of Science
- Consejo Superior de Investigaciones Científicas
- Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México
- National Institutes of Natural Sciences
- National Key Research and Development Program of China
- Office of International Science and Engineering
- Fermilab
- Los Alamos National Laboratory
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