First M87 Event Horizon Telescope Results. VII. Polarization of the Ring

Kazunori Akiyama , Juan Carlos Algaba , Antxon Alberdi , Walter Alef , Richard Anantua , Keiichi Asada , Rebecca Azulay , Anne-Kathrin Baczko , David Ball , Mislav Baloković , John Barrett , Bradford A. Benson , Dan Bintley , Lindy Blackburn , Raymond Blundell , Wilfred Boland , Katherine L. Bouman , Geoffrey C. Bower , Hope Boyce , Michael Bremer , Christiaan D. Brinkerink , Roger Brissenden , Silke Britzen , Avery E. Broderick , Dominique Broguiere , Thomas Bronzwaer , Do-Young Byun , John E. Carlstrom , Andrew Chael , Chi-Kwan Chan , Shami Chatterjee , Koushik Chatterjee , Ming-Tang Chen , Yongjun Chen , Paul M. Chesler , Ilje Cho , Pierre Christian , John E. Conway , James M. Cordes , Thomas M. Crawford , Geoffrey B. Crew , Alejandro Cruz-Osorio , Yuzhu Cui , Jordy Davelaar , Mariafelicia de Laurentis , Roger Deane , Jessica Dempsey , Gregory Desvignes (1) , Jason Dexter , Sheperd S. Doeleman , Ralph P. Eatough , Heino Falcke , Joseph Farah , Vincent L. Fish , Ed Fomalont , H. Alyson Ford , Raquel Fraga-Encinas , William T. Freeman , Per Friberg , Christian M. Fromm , Antonio Fuentes , Peter Galison , Charles F. Gammie , Roberto García , Olivier Gentaz , Boris Georgiev , Ciriaco Goddi , Roman Gold , José L. Gómez , Arturo I. Gómez-Ruiz , Minfeng Gu , Mark Gurwell , Kazuhiro Hada , Daryl Haggard , Michael H. Hecht , Ronald Hesper , Luis C. Ho , Paul Ho , Mareki Honma , Chih-Wei L. Huang , Lei Huang , David H. Hughes , Shiro Ikeda , Makoto Inoue , Sara Issaoun , David J. James , Buell T. Jannuzi , Michael Janssen , Britton Jeter , Wu Jiang , Alejandra Jimenez-Rosales , Michael D. Johnson , Svetlana Jorstad , Taehyun Jung , Mansour Karami , Ramesh Karuppusamy , Tomohisa Kawashima , Garrett K. Keating , Mark Kettenis , Dong-Jin Kim , Jae-Young Kim , Jongsoo Kim , Junhan Kim , Motoki Kino , Jun Yi Koay , Yutaro Kofuji , Patrick M. Koch , Shoko Koyama , Michael Kramer , Carsten Kramer , Thomas P. Krichbaum , Cheng-Yu Kuo , Tod R. Lauer , Sang-Sung Lee , Aviad Levis , Yan-Rong Li , Zhiyuan Li , Michael Lindqvist , Rocco Lico , Greg Lindahl , Jun Liu , Kuo Liu , Elisabetta Liuzzo , Wen-Ping Lo , Andrei P. Lobanov , Laurent Loinard , Colin Lonsdale , Ru-Sen Lu , Nicholas R. Macdonald , Jirong Mao , Nicola Marchili , Sera Markoff , Daniel P. Marrone , Alan P. Marscher , Iván Martí-Vidal , Satoki Matsushita , Lynn D. Matthews , Lia Medeiros , Karl M. Menten , Izumi Mizuno , Yosuke Mizuno , James M. Moran , Kotaro Moriyama , Monika Moscibrodzka , Cornelia Müller , Gibwa Musoke , Alejandro Mus Mejías , Daniel Michalik , Andrew Nadolski , Hiroshi Nagai , Neil M. Nagar , Masanori Nakamura , Ramesh Narayan , Gopal Narayanan , Iniyan Natarajan , Antonios Nathanail , Joey Neilsen , Roberto Neri , Chunchong Ni , Aristeidis Noutsos , Michael A. Nowak , Hiroki Okino , Héctor Olivares , Gisela N. Ortiz-León , Tomoaki Oyama , Feryal Özel , Daniel C. M. Palumbo , Jongho Park , Nimesh Patel , Ue-Li Pen , Dominic W. Pesce , Vincent Piétu , Richard Plambeck , Aleksandar Popstefanija , Oliver Porth , Felix M. Pötzl , Ben Prather , Jorge A. Preciado-López , Dimitrios Psaltis , Hung-Yi Pu , Venkatessh Ramakrishnan , Ramprasad Rao , Mark G. Rawlings , Alexander W. Raymond , Luciano Rezzolla , Angelo Ricarte , Bart Ripperda , Freek Roelofs , Alan Rogers , Eduardo Ros , Mel Rose , Arash Roshanineshat , Helge Rottmann , Alan L. Roy , Chet Ruszczyk , Kazi L. J. Rygl , Salvador Sánchez , David Sánchez-Arguelles , Mahito Sasada , Tuomas Savolainen , F. Peter Schloerb , Karl-Friedrich Schuster , Lijing Shao , Zhiqiang Shen , Des Small , Bong Won Sohn , Jason Soohoo , He Sun , Fumie Tazaki , Alexandra J. Tetarenko , Paul Tiede , Remo P. J. Tilanus , Michael Titus , Kenji Toma , Pablo Torne , Tyler Trent , Efthalia Traianou , Sascha Trippe , Ilse van Bemmel , Huib Jan van Langevelde , Daniel R. van Rossum , Jan Wagner , Derek Ward-Thompson , John Wardle , Jonathan Weintroub , Norbert Wex , Robert Wharton , Maciek Wielgus , George N. Wong , Qingwen Wu , Doosoo Yoon , André Young , Ken Young , Ziri Younsi , Feng Yuan , Ye-Fei Yuan , J. Anton Zensus , Guang-Yao Zhao , Shan-Shan Zhao

1 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics

In 2017 April, the Event Horizon Telescope (EHT) observed the near-horizon region around the supermassive black hole at the core of the M87 galaxy. These 1.3 mm wavelength observations revealed a compact asymmetric ring-like source morphology. This structure originates from synchrotron emission produced by relativistic plasma located in the immediate vicinity of the black hole. Here we present the corresponding linear-polarimetric EHT images of the center of M87. We find that only a part of the ring is significantly polarized. The resolved fractional linear polarization has a maximum located in the southwest part of the ring, where it rises to the level of ∼15%. The polarization position angles are arranged in a nearly azimuthal pattern. We perform quantitative measurements of relevant polarimetric properties of the compact emission and find evidence for the temporal evolution of the polarized source structure over one week of EHT observations. The details of the polarimetric data reduction and calibration methodology are provided. We carry out the data analysis using multiple independent imaging and modeling techniques, each of which is validated against a suite of synthetic data sets. The gross polarimetric structure and its apparent evolution with time are insensitive to the method used to reconstruct the image. These polarimetric images carry information about the structure of the magnetic fields responsible for the synchrotron emission. Their physical interpretation is discussed in an accompanying publication.

Keywords: Polarimetry; Radio interferometry; Very long baseline interferometry; Supermassive black holes; Active galactic nuclei; Low-luminosity active galactic nuclei; Astronomy data modeling; Galaxy accretion disks; Galaxies: individual: M87

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]

Kazunori Akiyama, Juan Carlos Algaba, Antxon Alberdi, Walter Alef, Richard Anantua, et al.. First M87 Event Horizon Telescope Results. VII. Polarization of the Ring. The Astrophysical Journal Letters, 2021, 910, ⟨10.3847/2041-8213/abe71d⟩. ⟨insu-03713798⟩