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
black hole physics
gravitation
accretion, accretion disks
Author
Rohan Dahale
Spanish National Research Council (CSIC)
I. Cho
Spanish National Research Council (CSIC)
Yonsei University
Korea Astronomy and Space Science Institute
Kotaro Moriyama
Spanish National Research Council (CSIC)
National Astronomical Observatory of Japan
K. Wiik
Aalto University
Tuorla Observatory
University of Turku
Paul Tiede
Harvard University
Harvard-Smithsonian Center for Astrophysics
J. L. Gomez
Spanish National Research Council (CSIC)
Chi Kwan Chan
University of Arizona
R. Gold
Heidelberg University
University of Southern Denmark
Vadim Y. Bernshteyn
University of Arizona
Marianna Foschi
Spanish National Research Council (CSIC)
Britton Jeter
Academia Sinica
Hung-Yi Pu
National Taiwan Normal University
Academia Sinica
Boris Georgiev
University of Arizona
Abhishek V. Joshi
Grainger College of Engineering
Alejandro Cruz-Osorio
Universidad Nacional Autónoma de México
Goethe University Frankfurt
Iniyan Natarajan
Harvard-Smithsonian Center for Astrophysics
Harvard University
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
National Astronomical Observatory of Japan
Harvard University
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
Harvard University
Rice 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
University of Chicago
Fermi National Accelerator Laboratory
Dan Bintley
James Clerk Maxwell Telescope
East Asian Observatory
Lindy Blackburn
Harvard-Smithsonian Center for Astrophysics
Harvard University
R. Blundell
Harvard-Smithsonian Center for Astrophysics
K. L. Bouman
California Institute of Technology (Caltech)
G. C. Bower
University of Hawaii
Academia Sinica
M. Bremer
Institut de Radioastronomie Millimétrique (IRAM)
Roger Brissenden
Harvard-Smithsonian Center for Astrophysics
Harvard University
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
University of Chicago
The Enrico Fermi Institute
A. Chael
Princeton University
Dominic O. Chang
Harvard-Smithsonian Center for Astrophysics
Harvard University
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
Zhejiang Lab
Shanghai Jiao Tong University
Brandon Curd
Harvard University
University of Texas
Harvard-Smithsonian Center for Astrophysics
Jordy Davelaar
Princeton University
Mariafelicia De Laurentis
University of Naples Federico II
National Institute for Nuclear Physics
R. P. Deane
University of Pretoria
University of Witwatersrand
Rhodes University
Jessica Dempsey
East Asian Observatory
Netherlands Institute for Radio Astronomy (ASTRON)
James Clerk Maxwell Telescope
Gregory Desvignes
Paris Observatory
Max Planck Society
Jason Dexter
JILA
Vedant Dhruv
Grainger College of Engineering
Indu K. Dihingia
Shanghai Jiao Tong University
S. Doeleman
Harvard-Smithsonian Center for Astrophysics
Harvard University
Sergio A. Dzib
Max Planck Society
Ralph P. Eatough
Max Planck Society
Chinese Academy of Sciences
Razieh Emami
Harvard-Smithsonian Center for Astrophysics
Joseph R. Farah
Las Cumbres Observatory Global Telescope Network
University of California
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
Massachusetts Institute of Technology (MIT)
Google Inc.
P. Friberg
James Clerk Maxwell Telescope
East Asian Observatory
Christian M. Fromm
Max Planck Society
University of Würzburg
Goethe University Frankfurt
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
National Institute for Nuclear Physics
Istituto nazionale di astrofisica (INAF)
University of Cagliari
University of Sao Paulo (USP)
Arturo I. Gómez-Ruiz
National Council for Science and Technology Mexico
National Institute of Astrophysics, Optics and Electronics
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
James Clerk Maxwell Telescope
East Asian Observatory
Academia Sinica
Mareki Honma
The Graduate University for Advanced Studies (SOKENDAI)
National Astronomical Observatory of Japan
University of Tokyo
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