First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole

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Researchers

Research units

  • National Radio Astronomy Observatory Socorro
  • Massachusetts Institute of Technology
  • National Astronomical Observatory of Japan
  • Harvard University
  • CSIC
  • Max Planck Institute for Radio Astronomy
  • National Taiwan University
  • University of Valencia
  • University of Arizona
  • East Asian Observatory
  • Nederlandse Onderzoekschool voor Astronomie
  • California Institute of Technology
  • Academia Sinica Taiwan
  • Institut de Radio Astronomie Millimétrique
  • Radboud University Nijmegen
  • Perimeter Institute for Theoretical Physics
  • University of Waterloo
  • Korea Astronomy and Space Science Institute
  • University of Science and Technology UST
  • University of Chicago
  • Cornell University
  • University of Amsterdam
  • CAS - Shanghai Astronomical Observatory
  • Chinese Academy of Sciences
  • Chalmers University of Technology
  • Graduate University for Advanced Studies
  • University of Naples Federico II
  • Goethe University Frankfurt
  • University of Pretoria
  • Rhodes University
  • Max Planck Institute for Extraterrestrial Physics
  • Universidad de Concepcion

Abstract

We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These images show a prominent ring with a diameter of ∼40 μas, consistent with the size and shape of the lensed photon orbit encircling the "shadow" of a supermassive black hole. The ring is persistent across four observing nights and shows enhanced brightness in the south. To assess the reliability of these results, we implemented a two-stage imaging procedure. In the first stage, four teams, each blind to the others' work, produced images of M87 using both an established method (CLEAN) and a newer technique (regularized maximum likelihood). This stage allowed us to avoid shared human bias and to assess common features among independent reconstructions. In the second stage, we reconstructed synthetic data from a large survey of imaging parameters and then compared the results with the corresponding ground truth images. This stage allowed us to select parameters objectively to use when reconstructing images of M87. Across all tests in both stages, the ring diameter and asymmetry remained stable, insensitive to the choice of imaging technique. We describe the EHT imaging procedures, the primary image features in M87, and the dependence of these features on imaging assumptions.

Details

Original languageEnglish
Article numberL4
JournalAstrophysical Journal Letters
Volume875
Issue number1
Publication statusPublished - 10 Apr 2019
MoE publication typeA1 Journal article-refereed

    Research areas

  • black hole physics, galaxies: individual (M87), galaxies: jets, techniques: high angular resolution, techniques: image processing, techniques: interferometric

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