Origin of the ring ellipticity in the black hole images of M87<sup>*</sup>

We investigate the origin of the elliptical ring structure observed in the images of the supermassive black hole M87 * , aiming to disentangle contributions from gravitational, astrophysical, and imaging effects. Leveraging the enhanced capabilities of the Event Horizon Telescope (EHT)'s 2018 array, including improved ( u , v )-coverage from the Greenland Telescope, we measured the ring's ellipticity using five independent imaging methods, obtaining a consistent average value of τ = 0.08 −0.02 +0.03 with a position angle of ξ = 50.1 −7.6 +6.2 degrees. To interpret this measurement, we compared it to general relativistic magnetohydrodynamic (GRMHD) simulations spanning a wide range of physical parameters including the thermal or nonthermal electron distribution function, spins, and ion-to-electron temperature ratios in both low- and high-density regions. We find no statistically significant correlation between spin and ellipticity in GRMHD images. Instead, we identify a correlation between ellipticity and the fraction of non-ring emission, particularly in nonthermal models and models with higher jet emission. These results indicate that the ellipticity measured from the M87 * emission structure is consistent with that expected from simulations of turbulent accretion flows around black holes, where it is dominated by astrophysical effects rather than gravitational ones. Future high-resolution imaging, including space very long baseline interferometry and long-term monitoring, will be essential to isolate gravitational signatures from astrophysical effects.

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Journal
Astronomy and Astrophysics
Published
2025-06-03
DOI
https://doi.org/10.1051/0004-6361/202555235
Primary Topic
Astrophysical Phenomena and Observations
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article
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article

Origin of the ring ellipticity in the black hole images of M87*

Wanga Mulaudzi, Ben Prather, Dimitrios Psaltis, Chunchong Ni et al.
Astronomy and Astrophysics
Astrophysical Phenomena and Observations
article

Origin of the ring ellipticity in the black hole images of M87*

Wanga Mulaudzi, Ben Prather, Dimitrios Psaltis, Chunchong Ni, Chi‐kwan Chan, Richard Anantua, Paul Yamaguchi, Ru-Sen Lu, M. Krämer, Doosoo Yoon, Teresa Toscano, Greg Lindahl, Lia Medeiros, Gopal Narayanan, Yuzhu Cui, S. Britzen, T. Savolainen, Ezequiel Albentosa-Ruíz, Saurabh Kumar, K. Wiik, Roman Gold, Monika Mościbrodzka, Douglas Ferreira Carlos, Angelo Ricarte, Ignacio Ruiz, D. Ward–Thompson, Des Small, Joey Neilsen, Kenji Toma, Tomohisa Kawashima, Michaël Janssen, Shoko Koyama, Ronald Hesper, Sandra Bustamante, A. Joana Kramer, Makoto Inoue, A. Alberdi, Zhi-Qiang Shen, Jesse Vos, Britton Jeter, Matthew Turk, Michael Titus, Paul T. P. Ho, Jordy Davelaar, Ue‐Li Pen, Laurent Loinard, Héctor Olivares, Ilje Cho, Santiago Navarro Fuentes, Jonathan Weintroub, Vedant Dhruv, Iniyan Natarajan, Paul Tiede, Sheperd S. Doeleman, Sera Markoff, Prashant Kocherlakota, Kamal Souccar, Dominique Broguière, R. Blundell, Satoki Matsushita, Gunther Witzel, Jason Soohoo, Efthalia Traianou, Hiroshi Nagai, G. Principe, Svetlana G. Jorstad, Ming‐Tang Chen, Izumi Mizuno, Bart Ripperda, Salvador Sánchez, Hiroki Okino, Alejandro Mus, Bong Won Sohn, Kaushik Satapathy, Cristina Romero-Cañizales, Anne-Kathrin Baczko, Bidisha Bandyopadhyay, Kazuhiro Hada, Guang-Yao Zhao, Mark Kettenis, Luciano Rezzolla, Wen-Ping Lo, John Barrett, Taehyun Jung, Peter Galison, Michael D. Johnson, Juan Carlos Algaba, Ilse van Bemmel, Razieh Emami, I. Myserlis, Amy Benson, Hung-Yi Pu, Kazunori Akiyama, J. A. Zensus, Motoki Kino, Aviad Levis, E. B. Fomalont, Per Friberg, Shiro Ikeda, Vincent L. Fish, Andrew Chael, Olivier Gentaz, Noemi La Bella, He Sun, Roger Deane, Lijing Shao, C. Goddi, Ramprasad Rao, Boris Georgiev, J. F. C. Wardle, Roger Brissenden, N. George Wong, Marianna Foschi, Michi Bauböck, S. Silpa, Andrzej J. Nowak, K. Schüster, Jonathan Schonfeld, J. Montgomery, M. Sánchez‐Portal, Ziri Younsi, Huib Jan van Langevelde, N. Marchili, Kotaro Moriyama, H. Falcke, U. Bach, Shan-Shan Zhao, Dhanya G. Nair, Sascha Trippe, Mareki Honma, Arash Roshanineshat, Helge Rottmann, G. Desvignes, M. Lindqvist, Sang-Sung Lee, Jason Dexter, Minfeng Gu, Maciek Wielgus, Jessica Dempsey, Pablo Torné, Shami Chatterjee, Mariafelicia De Laurentis, Cheng‐Yu Kuo, Fumie Tazaki, Freek Roelofs, Joseph Farah, Antonio Fuentes, Rebecca Azulay, C. Krämer, C. M. Violette Impellizzeri, Raquel Fraga-Encinas, A. L. Roy, C. Ho, Gibwa Musoke, Nimesh Patel, F. Charles Gammie, Michael Bremer, Antonios Nathanail, Kuo Liu, Thomas Bronzwaer, Tomoaki Oyama, Venkatessh Ramakrishnan, Alejandra Jiménez-Rosales, Georgios Filippos Paraschos, Mahito Sasada, Eric Carlström, David Sánchez-Argüelles, Mark Gurwell, Mikhail Lisakov, André Young, Harriet Parsons, Gertie Geertsema, Sara Issaoun, Pierre Christian, E. Ros, Katie M. Keating, Feryal Özel, Daryl Haggard, Jan Wagner, Lei Huang, R. Karuppusamy, Alejandro Cruz-Osorio, A. P. Lobanov, Koushik Chatterjee, Michael Fromm, Patrick M. Koch, Junghwan Oh, Dirk Heumann, Masanori Nakamura, José L. Gómez, Keiichi Asada, Rohan Dahale, Mislav Baloković, Ai-Ling Zeng, Robert Wharton, Malhar Nagar, Elisabetta Liuzzo, O. Chang, Jan Röder, Oliver Porth, Lindy Blackburn, Brandon Curd, Tyler Trent, Yosuke Mizuno, R. Nicholas MacDonald, Aristomenis Yfantis, Daniel C. M. Palumbo, Cornelia Müller, Joshua S. Stanway, Jae-Young Kim, Dong-Jin Kim, Shuo Zhang, Jongho Park, Jongsoo Kim, Lei Huang, Wei Yu, Hendrik Müller, J. E. Conway, Roberto García, William T. Freeman, H. Alyson Ford, M. Karl Menten, F. Peter Schloerb, Qingwen Wu, Ye‐Fei Yuan, V. Piétu, D. H. Hughes, Lynn D. Matthews, W. Alef, Yutaro Kofuji, Ye‐Fei Yuan, Junhan Kim, Iván Martí-Vidal, Dan Bintley, Aleksandar PopStefanija, Rocco Lico, E. Washington, John Lonsdale, David Ball, Adam C. Jones, J. David James, C. Bower, Michael E. Moran, D.S. León Salas, Nitika Yadlapalli, M. K. Crawford, S. Nicholas Conroy, J. Mao, Chet Ruszczyk, Jun Yi Koay, T. Buell Jannuzi, L.J. Kazi Rygl, P. Thomas Krichbaum, E. Amy Lowitz, P. Daniel Marrone, P. Alan Marscher, W. Dominic Pesce, Mark G. Rawlings, J. Alexandra Tetarenko, R. P. J. Tilanus, R. Daniel van Rossum, F. Michael Wondrak, G. Crew, L. Katherine Bouman, E. Avery Broderick, K. Indu Dihingia, A. Sergio Dzib, P. Ralph Eatough, I. Arturo Gómez-Ruiz, Vadim Y. Bernshteyn, Abhishek V. Joshi, Xiaopeng Cheng
article en

Abstract

We investigate the origin of the elliptical ring structure observed in the images of the supermassive black hole M87 * , aiming to disentangle contributions from gravitational, astrophysical, and imaging effects. Leveraging the enhanced capabilities of the Event Horizon Telescope (EHT)'s 2018 array, including improved ( u , v )-coverage from the Greenland Telescope, we measured the ring's ellipticity using five independent imaging methods, obtaining a consistent average value of τ = 0.08 −0.02 +0.03 with a position angle of ξ = 50.1 −7.6 +6.2 degrees. To interpret this measurement, we compared it to general relativistic magnetohydrodynamic (GRMHD) simulations spanning a wide range of physical parameters including the thermal or nonthermal electron distribution function, spins, and ion-to-electron temperature ratios in both low- and high-density regions. We find no statistically significant correlation between spin and ellipticity in GRMHD images. Instead, we identify a correlation between ellipticity and the fraction of non-ring emission, particularly in nonthermal models and models with higher jet emission. These results indicate that the ellipticity measured from the M87 * emission structure is consistent with that expected from simulations of turbulent accretion flows around black holes, where it is dominated by astrophysical effects rather than gravitational ones. Future high-resolution imaging, including space very long baseline interferometry and long-term monitoring, will be essential to isolate gravitational signatures from astrophysical effects.

Astronomy and AstrophysicsVol. 699
University of Lethbridge (CA), Canadian Institute for Advanced Research (CA), Boston University (US), Hiroshima University (JP), Goethe University Frankfurt (DE), Tokyo Electron (Japan) (JP), Tokyo Institute of Technology (JP), Kogakuin University (JP), University of Hawaiʻi at Mānoa (US), Leiden University (NL), California Institute of Technology (US), University of Science and Technology of China (CN), Las Cumbres Observatory Global Telescope Network (US), Google (United States) (US), Commonwealth Scientific and Industrial Research Organisation (AU), Centre National de la Recherche Scientifique (FR), Pontificia Universidad Católica de Valparaíso (CL), Georgia Institute of Technology (US), Royal Netherlands Meteorological Institute (NL), Institute of Astronomy and Astrophysics, Academia Sinica (TW), Woodwell Climate Research Center (US), Fermi National Accelerator Laboratory (US), National Taiwan Normal University (TW), Harvard University (US), Joint Institute for Laboratory 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