The persistent shadow of the supermassive black hole of M 87: I. Observations, calibration, imaging, and analysis*

• Published in: Astronomy & Astrophysics
• Main Authors: Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Bach, Uwe, Baczko, Anne Kathrin, Ball, David, Baloković, Mislav, Bandyopadhyay, Bidisha, Barrett, John, Bauböck, Michi, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Bustamante, Sandra, Carlstrom, John E., Chael, Andrew, Chan, Chi Kwan, Chang, Dominic O., Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming Tang, Chen, Yongjun, Cheng, Xiaopeng, Cho, Ilje, Christian, Pierre, Conroy, Nicholas S., Conway, John E., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, Dahale, Rohan, Davelaar, Jordy, Ramakrishnan, Venkatessh, Savolainen, Tuomas, Wiik, Kaj, Event Horizon Telescope Collaborat
• Other Authors: Department of Electronics and Nanoengineering, Metsähovi Radio Observatory, Anne Lähteenmäki Group, Massachusetts Institute of Technology MIT, CSIC - Institute of Astrophysics of Andalusia, Max Planck Institute for Radio Astronomy, University of Malaya, Harvard University, Academia Sinica Institute of Astronomy and Astrophysics, University of Arizona, Yale University, Universidad de Concepción, University of Illinois at Urbana-Champaign, Fermi National Accelerator Laboratory, East Asian Observatory, California Institute of Technology, McGill University, Institut de Radioastronomie Millimétrique, Perimeter Institute for Theoretical Physics, Radboud University Nijmegen, University of Massachusetts, University of Chicago, Princeton University, Cornell University, CAS - Shanghai Astronomical Observatory, Korea Astronomy and Space Science Institute, Fairfield University, Chalmers University of Technology, Universidad Nacional Autónoma de México, Science Support Office, Aalto-yliopisto, Aalto University
• Format: Article in Journal/Newspaper
• Language: English
• Published: EDP Sciences 2024
• Subjects: Accretion; accretion disks; Black hole physics; Galaxies: active; Galaxies: individual: M 87; Galaxies: jets; Gravitation; Greenland; Greenland Telescope
• Online Access: https://aaltodoc.aalto.fi/handle/123456789/127547; https://doi.org/10.1051/0004-6361/202347932

Publisher Copyright: © 2023 The Author(s). In April 2019, the Event Horizon Telescope (EHT) Collaboration reported the first-ever event-horizon-scale images of a black hole, resolving the central compact radio source in the giant elliptical galaxy M 87. These images reveal a ring with a southerly brightness distribution and a diameter of ∼42 μas, consistent with the predicted size and shape of a shadow produced by the gravitationally lensed emission around a supermassive black hole. These results were obtained as part of the April 2017 EHT observation campaign, using a global very long baseline interferometric radio array operating at a wavelength of 1.3 mm. Here, we present results based on the second EHT observing campaign, taking place in April 2018 with an improved array, wider frequency coverage, and increased bandwidth. In particular, the additional baselines provided by the Greenland telescope improved the coverage of the array. Multiyear EHT observations provide independent snapshots of the horizon-scale emission, allowing us to confirm the persistence, size, and shape of the black hole shadow, and constrain the intrinsic structural variability of the accretion flow. We have confirmed the presence of an asymmetric ring structure, brighter in the southwest, with a median diameter of 43.3-3.1+1.5 μas. The diameter of the 2018 ring is remarkably consistent with the diameter obtained from the previous 2017 observations. On the other hand, the position angle of the brightness asymmetry in 2018 is shifted by about 30 relative to 2017. The perennial persistence of the ring and its diameter robustly support the interpretation that the ring is formed by lensed emission surrounding a Kerr black hole with a mass ∼6.5× 109M. The significant change in the ring brightness asymmetry implies a spin axis that is more consistent with the position angle of the large-scale jet. Peer reviewed