First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole

Kazunori Akiyama;Antxon Alberdi;Walter Alef;Keiichi Asada;Rebecca Azulay;Anne-Kathrin Baczko;David Ball;Mislav Baloković;John Barrett;Dan Bintley;Lindy Blackburn;Wilfred Boland;Katherine L. Bouman;Geoffrey C. Bower;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;Ilje Cho;Pierre Christian;John E. Conway;James M. Cordes;Geoffrey B. Crew;Yuzhu Cui;Jordy Davelaar;Mariafelicia De Laurentis;Roger Deane;Jessica Dempsey;Gregory Desvignes;Jason Dexter;Sheperd S. Doeleman;Ralph P. Eatough;Heino Falcke;Vincent L. Fish;Ed Fomalont;Raquel Fraga-Encinas;William T. Freeman;Per Friberg;Christian M. Fromm;José L. Gómez;Peter Galison;Charles F. Gammie;Roberto García;Olivier Gentaz;Boris Georgiev;Ciriaco Goddi;Roman Gold;Minfeng Gu;Mark Gurwell;Kazuhiro Hada;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;Michael D. Johnson;Svetlana Jorstad;Taehyun Jung;Mansour Karami;Ramesh Karuppusamy;Tomohisa Kawashima;Garrett K. Keating;Mark Kettenis;Jae-Young Kim;Junhan Kim;Jongsoo Kim;Motoki Kino;Jun Yi Koay;Patrick M. Koch;Shoko Koyama;Michael Kramer;Carsten Kramer;Thomas P. Krichbaum;Cheng-Yu Kuo;Tod R. Lauer;Sang-Sung Lee;Yan-Rong Li;Zhiyuan Li;Michael Lindqvist;Kuo Liu;Elisabetta Liuzzo;Wen-Ping Lo;Andrei P. Lobanov;Laurent Loinard;Colin Lonsdale;Ru-Sen Lu;Nicholas R. MacDonald;Jirong Mao;Sera Markoff;Daniel P. Marrone;Alan P. Marscher;Iván Martí-Vidal;Satoki Matsushita;Lynn D. Matthews;Lia Medeiros;Karl M. Menten;Yosuke Mizuno;Izumi Mizuno;James M. Moran;Kotaro Moriyama;Monika Moscibrodzka;Cornelia Müller;Hiroshi Nagai;Neil M. Nagar;Masanori Nakamura;Ramesh Narayan;Gopal Narayanan;Iniyan Natarajan;Roberto Neri;Chunchong Ni;Aristeidis Noutsos;Hiroki Okino;Héctor Olivares;Tomoaki Oyama;Feryal Özel;Daniel C. M. Palumbo;Nimesh Patel;Ue-Li Pen;Dominic W. Pesce;Vincent Piétu;Richard Plambeck;Aleksandar PopStefanija;Oliver Porth;Ben Prather;Jorge A. Preciado-López;Dimitrios Psaltis;Hung-Yi Pu;Venkatessh Ramakrishnan;Ramprasad Rao;Mark G. Rawlings;Alexander W. Raymond;Luciano Rezzolla;Bart Ripperda;Freek Roelofs;Alan Rogers;Eduardo Ros;Mel Rose;Arash Roshanineshat;Helge Rottmann;Alan L. Roy;Chet Ruszczyk;Benjamin R. Ryan;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;Fumie Tazaki;Paul Tiede;Remo P. J. Tilanus;Michael Titus;Kenji Toma;Pablo Torne;Tyler Trent;Sascha Trippe;Shuichiro Tsuda;Ilse van Bemmel;Huib Jan van Langevelde;Daniel R. van Rossum;Jan Wagner;John Wardle;Jonathan Weintroub;Norbert Wex;Robert Wharton;Maciek Wielgus;George N. Wong;Qingwen Wu;André Young;Ken Young;Ziri Younsi;Feng Yuan;Ye-Fei Yuan;J. Anton Zensus;Guangyao Zhao;Shan-Shan Zhao;Ziyan Zhu;Joseph R. Farah;Zheng Meyer-Zhao;Daniel Michalik;Andrew Nadolski;Hiroaki Nishioka;Nicolas Pradel;Rurik A. Primiani;Kamal Souccar;Laura Vertatschitsch;Paul Yamaguchi

2019-01-01

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Abstract

We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These images show a prominent ring with a diameter of similar to 40 mu as, consistent with the size and shape of the lensed photon orbit encircling the "shadow" of a supermassive black hole. The ring is persistent across four observing nights and shows enhanced brightness in the south. To assess the reliability of these results, we implemented a two-stage imaging procedure. In the first stage, four teams, each blind to the others' work, produced images of M87 using both an established method (CLEAN) and a newer technique (regularized maximum likelihood). This stage allowed us to avoid shared human bias and to assess common features among independent reconstructions. In the second stage, we reconstructed synthetic data from a large survey of imaging parameters and then compared the results with the corresponding ground truth images. This stage allowed us to select parameters objectively to use when reconstructing images of M87. Across all tests in both stages, the ring diameter and asymmetry remained stable, insensitive to the choice of imaging technique. We describe the EHT imaging procedures, the primary image features in M87, and the dependence of these features on imaging assumptions.