Origin of the ring ellipticity in the black hole images of M87
Journal article, 2025
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+−000302 with a position angle of ξ = 50.1−+7662 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.
galaxies: active
accretion, accretion disks
gravitation
black hole physics
Author
Rohan Dahale
Spanish National Research Council (CSIC)
I. Cho
Korea Astronomy and Space Science Institute
Spanish National Research Council (CSIC)
Yonsei University
Kotaro Moriyama
Spanish National Research Council (CSIC)
National Astronomical Observatory of Japan
K. Wiik
Tuorla Observatory
University of Turku
Aalto University
Paul Tiede
Harvard-Smithsonian Center for Astrophysics
Harvard University
J. L. Gomez
Spanish National Research Council (CSIC)
Chi Kwan Chan
University of Arizona
R. Gold
Heidelberg University
University of Southern Denmark
Institut für Theoretische Physik Heidelberg
Vadim Y. Bernshteyn
University of Arizona
Marianna Foschi
Spanish National Research Council (CSIC)
Britton Jeter
Academia Sinica
Hung-Yi Pu
Academia Sinica
National Taiwan Normal University
Boris Georgiev
University of Arizona
Abhishek V. Joshi
Grainger College of Engineering
Alejandro Cruz-Osorio
Goethe University Frankfurt
Universidad Nacional Autónoma de México
Iniyan Natarajan
Harvard University
Harvard-Smithsonian Center for Astrophysics
Avery E. Broderick
Perimeter Institute for Theoretical Physics
University of Waterloo
León David Sosapanta Salas
Anton Pannekoek Institute for Astronomy
Koushik Chatterjee
University of Maryland
Kazunori Akiyama
Harvard University
National Astronomical Observatory of Japan
Massachusetts Institute of Technology (MIT)
E. Albentosa-Ruiz
Universitat de Valencia
Antxon Alberdi
Spanish National Research Council (CSIC)
Walter Alef
Max Planck Society
Juan-Carlos Algaba
University of Malaya
Richard Anantua
Rice University
Harvard University
University of Texas
Harvard-Smithsonian Center for Astrophysics
K. Asada
Academia Sinica
R. Azulay
Universitat de Valencia
Max Planck Society
U. Bach
Max Planck Society
A. K. Baczko
Max Planck Society
David Ball
University of Arizona
Mislav Baloković
Yale University
Bidisha Bandyopadhyay
University of Concepcion
John Barrett
Massachusetts Institute of Technology (MIT)
M. Bauböck
Grainger College of Engineering
Bradford A. Benson
Fermi National Accelerator Laboratory
University of Chicago
Dan Bintley
James Clerk Maxwell Telescope
East Asian Observatory
Lindy Blackburn
Harvard University
Harvard-Smithsonian Center for Astrophysics
R. Blundell
Harvard-Smithsonian Center for Astrophysics
K. L. Bouman
California Institute of Technology (Caltech)
G. C. Bower
Academia Sinica
University of Hawaii
M. Bremer
Institut de Radioastronomie Millimétrique (IRAM)
Roger Brissenden
Harvard University
Harvard-Smithsonian Center for Astrophysics
Silke Britzen
Max Planck Society
D. Broguière
Institut de Radioastronomie Millimétrique (IRAM)
Thomas Bronzwaer
Radboud University
Sandra Bustamente
University of Massachusetts
Douglas Ferreira Carlos
University of Sao Paulo (USP)
J. E. Carlstrom
The Enrico Fermi Institute
University of Chicago
A. Chael
Princeton University
Dominic O. Chang
Harvard University
Harvard-Smithsonian Center for Astrophysics
S. Chatterjee
Cornell University
Ming Tang Chen
Academia Sinica
Yongjun Chen
Chinese Academy of Sciences
X. P. Cheng
Korea Astronomy and Space Science Institute
Pierre Christian
WattTime
Nicholas S. Conroy
Harvard-Smithsonian Center for Astrophysics
University of Illinois
John Conway
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Thomas M. Crawford
University of Chicago
G. Crew
Massachusetts Institute of Technology (MIT)
Yuzhu Cui
Shanghai Jiao Tong University
Zhejiang Lab
Brandon Curd
Harvard-Smithsonian Center for Astrophysics
Harvard University
University of Texas
Jordy Davelaar
Princeton University
Mariafelicia De Laurentis
National Institute for Nuclear Physics
University of Naples Federico II
R. P. Deane
Rhodes University
University of Pretoria
University of Witwatersrand
Jessica Dempsey
James Clerk Maxwell Telescope
Netherlands Institute for Radio Astronomy (ASTRON)
East Asian Observatory
Gregory Desvignes
Max Planck Society
Paris Observatory
Jason Dexter
JILA
Vedant Dhruv
Grainger College of Engineering
Indu K. Dihingia
Shanghai Jiao Tong University
S. Doeleman
Harvard University
Harvard-Smithsonian Center for Astrophysics
Sergio A. Dzib
Max Planck Society
Ralph P. Eatough
Chinese Academy of Sciences
Max Planck Society
Razieh Emami
Harvard-Smithsonian Center for Astrophysics
Joseph R. Farah
University of California
Las Cumbres Observatory Global Telescope Network
V. Fish
Massachusetts Institute of Technology (MIT)
E. Fomalont
National Radio Astronomy Observatory
H.D. Falcke
University of Arizona
R. Fraga-Encinas
Radboud University
William T. Freeman
Google Inc.
Massachusetts Institute of Technology (MIT)
P. Friberg
James Clerk Maxwell Telescope
East Asian Observatory
Christian M. Fromm
Max Planck Society
Goethe University Frankfurt
University of Würzburg
Antonio Fuentes
Spanish National Research Council (CSIC)
Peter Galison
Harvard University
Charles F. Gammie
University of Illinois
Grainger College of Engineering
Roberto Garcia
Institut de Radioastronomie Millimétrique (IRAM)
Olivier Gentaz
Institut de Radioastronomie Millimétrique (IRAM)
Gertie Geertsema
Royal Netherlands Meteorological Institute
C. Goddi
University of Cagliari
Istituto nazionale di astrofisica (INAF)
University of Sao Paulo (USP)
National Institute for Nuclear Physics
Arturo I. Gómez-Ruiz
National Institute of Astrophysics, Optics and Electronics
National Council for Science and Technology Mexico
Minfeng Gu
Chinese Academy of Sciences
M. Gurwell
Harvard-Smithsonian Center for Astrophysics
K. Hada
University of Tokyo
National Astronomical Observatory of Japan
Daryl Haggard
McGill University
R. Hesper
University of Groningen
Dirk Heumann
University of Arizona
Luis C. Ho
Beijing University of Technology
P. T. P. Ho
Academia Sinica
East Asian Observatory
James Clerk Maxwell Telescope
Mareki Honma
National Astronomical Observatory of Japan
University of Tokyo
The Graduate University for Advanced Studies (SOKENDAI)
Chih Wei L. Huang
Academia Sinica
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 699 A279RadioNet 4
European Commission (EC) (EC/H2020/730562), 2017-01-01 -- 2020-12-31.
Onsala space observatory infrastructure
Swedish Research Council (VR) (2017-00648), 2018-01-01 -- 2021-12-31.
Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
DOI
10.1051/0004-6361/202555235