The Polarized Image of a Synchrotron-emitting Ring of Gas Orbiting a Black Hole

Ramesh Narayan , Daniel C. M. Palumbo , Michael D. Johnson , Zachary Gelles , Elizabeth Himwich , Dominic O. Chang , Angelo Ricarte , Jason Dexter , Charles F. Gammie , Andrew A. Chael , Kazunori Akiyama , Antxon Alberdi , Walter Alef , Juan Carlos Algaba , 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 , 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) , Sheperd S. Doeleman , Ralph P. Eatough , Heino Falcke , Joseph Farah , Vincent L. Fish , Ed Fomalont , H. Alyson Ford , Raquel Fraga-Encinas , Per Friberg , Christian M. Fromm , Antonio Fuentes , Peter Galison , 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 , 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 , Hiroshi Nagai , Neil M. Nagar , Masanori Nakamura , 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 , 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 , 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

Synchrotron radiation from hot gas near a black hole results in a polarized image. The image polarization is determined by effects including the orientation of the magnetic field in the emitting region, relativistic motion of the gas, strong gravitational lensing by the black hole, and parallel transport in the curved spacetime. We explore these effects using a simple model of an axisymmetric, equatorial accretion disk around a Schwarzschild black hole. By using an approximate expression for the null geodesics derived by Beloborodov and conservation of the Walker-Penrose constant, we provide analytic estimates for the image polarization. We test this model using currently favored general relativistic magnetohydrodynamic simulations of M87*, using ring parameters given by the simulations. For a subset of these with modest Faraday effects, we show that the ring model broadly reproduces the polarimetric image morphology. Our model also predicts the polarization evolution for compact flaring regions, such as those observed from Sgr A* with GRAVITY. With suitably chosen parameters, our simple model can reproduce the EVPA pattern and relative polarized intensity in Event Horizon Telescope images of M87*. Under the physically motivated assumption that the magnetic field trails the fluid velocity, this comparison is consistent with the clockwise rotation inferred from total intensity images.

Keywords: Accretion; Black holes; Polarimetry; Magnetic fields

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

Ramesh Narayan, Daniel C. M. Palumbo, Michael D. Johnson, Zachary Gelles, Elizabeth Himwich, et al.. The Polarized Image of a Synchrotron-emitting Ring of Gas Orbiting a Black Hole. The Astrophysical Journal, 2021, 912, ⟨10.3847/1538-4357/abf117⟩. ⟨insu-03713780⟩