First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring

Abstract

Abstract The Event Horizon Telescope (EHT) has mapped the central compact radio source of the elliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Here we consider the physical implications of the asymmetric ring seen in the 2017 EHT data. To this end, we construct a large library of models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by general relativistic ray tracing. We compare the observed visibilities with this library and confirm that the asymmetric ring is consistent with earlier predictions of strong gravitational lensing of synchrotron emission from a hot plasma orbiting near the black hole event horizon. The ring radius and ring asymmetry depend on black hole mass and spin, respectively, and both are therefore expected to be stable when observed in future EHT campaigns. Overall, the observed image is consistent with expectations for the shadow of a spinning Kerr black hole as predicted by general relativity. If the black hole spin and M87’s large scale jet are aligned, then the black hole spin vector is pointed away from Earth. Models in our library of non-spinning black holes are inconsistent with the observations as they do not produce sufficiently powerful jets. At the same time, in those models that produce a sufficiently powerful jet, the latter is powered by extraction of black hole spin energy through mechanisms akin to the Blandford-Znajek process. We briefly consider alternatives to a black hole for the central compact object. Analysis of existing EHT polarization data and data taken simultaneously at other wavelengths will soon enable new tests of the GRMHD models, as will future EHT campaigns at 230 and 345 GHz.

Keywords

Affiliated Institutions

• Goethe University Frankfurt DE
• Nederlandse Onderzoekschool Voor Astronomie
• National Sun Yat-sen University TW
• Harvard University US
• Instituto de Astrofísica de Andalucía ES
• Institute of Astronomy and Astrophysics, Academia Sinica TW
• National Radio Astronomy Observatory US
• Institut de Radioastronomie Millimétrique FR
• 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
• Chalmers University of Technology SE
• Korea University of Science and Technology KR
• Fermi National Accelerator Laboratory US
• Boston University US
• Leiden University NL
• Kogakuin University JP
• University of Naples Federico II IT
• Kavli Institute for the Physics and Mathematics of the Universe JP
• University of Amsterdam NL
• Parc Científic de la Universitat de València ES
• Perimeter Institute CA
• Center for Astrophysics Harvard & Smithsonian US
• University of Illinois Urbana-Champaign US
• University of Chicago US
• University of Arizona US
• University of Waterloo CA
• Joint Institute for VLBI ERIC NL
• East Asian Observatory US
• University of Pretoria ZA
• Massachusetts Institute of Technology US
• 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
• Istituto Nazionale di Fisica Nucleare, Sezione di Napoli IT
• Cornell University US
• Max Planck Institute for Extraterrestrial Physics DE
• The Institute of Statistical Mathematics JP
• The University of Tokyo JP
• Woodwell Climate Research Center US
• National Astronomical Observatory of Japan JP
• Radboud University Nijmegen NL
• Kitt Peak National Observatory US

Related Publications