THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope
Authors: Broderick Avery E. , Gold Roman , Karami Mansour , Preciado-López Jorge A. , Tiede Paul , Pu Hung-Yi , Akiyama Kazunori , Alberdi Antxon , Alef Walter , Asada Keiichi , Azulay Rebecca , Baczko Anne-Kathrin , Baloković Mislav , Barrett John , Bintley Dan , Blackburn Lindy , Boland Wilfred , Bouman Katherine L. , Bower Geoffrey C. , Bremer Michael , Brinkerink Christiaan D. , Brissenden Roger , Britzen Silke , Broguiere Dominique , Bronzwaer Thomas , Byun Do-Young , Carlstrom John E. , Chael Andrew , Chatterjee Shami , Chatterjee Koushik , Chen Ming-Tang , Chen 陈永 Yongjun 军 , Cho Ilje , Conway John E. , Cordes James M. , Crew Geoffrey B. , Cui Yuzhu , Davelaar Jordy , De Laurentis Mariafelicia , Deane Roger , Dempsey Jessica , Desvignes Gregory , Doeleman Sheperd S. , Eatough Ralph P. , Falcke Heino , Fish Vincent L. , Fomalont Ed , Fraga-Encinas Raquel , Friberg Per , Fromm Christian M. , Galison Peter , Gammie Charles F. , García Roberto , Gentaz Olivier , Georgiev Boris , Goddi Ciriaco , Gómez José L. , Gu 顾敏 Minfeng 峰 , Gurwell Mark , Hada Kazuhiro , Hecht Michael H. , Hesper Ronald , Ho 何子 Luis C. 山 , Ho Paul , Honma Mareki , Huang Chih-Wei L. , Huang 黄 Lei 磊 , Hughes David H. , Inoue Makoto , Issaoun Sara , James David J. , Janssen Michael , Jeter Britton , Jiang 江 Wu 悟 , Jiménez-Rosales Alejandra , Johnson Michael D. , Jorstad Svetlana , Jung Taehyun , Karuppusamy Ramesh , Kawashima Tomohisa , Keating Garrett K. , Kettenis Mark , Kim Jae-Young , Kim Jongsoo , Kino Motoki , Koay Jun Yi , Koch Patrick M. , Koyama Shoko , Kramer Michael , Kramer Carsten , Krichbaum Thomas P. , Kuo Cheng-Yu , Lee Sang-Sung , Li 李彦 Yan-Rong 荣 , Li 李志 Zhiyuan 远 , Lindqvist Michael , Lico Rocco , Liu Kuo , Liuzzo Elisabetta , Lo Wen-Ping , Lobanov Andrei P. , Loinard Laurent , Lonsdale Colin , Lu 路如 Ru-Sen 森 , MacDonald Nicholas R. , Mao 毛基 Jirong 荣 , Marscher Alan P. , Martí-Vidal Iván , Matsushita Satoki , Matthews Lynn D. , Menten Karl M. , Mizuno Yosuke , Mizuno Izumi , Moran James M. , Moriyama Kotaro , Moscibrodzka Monika , Müller Cornelia , Nagai Hiroshi , Nagar Neil M. , Nakamura Masanori , Narayan Ramesh , Narayanan Gopal , Natarajan Iniyan , Neri Roberto , Ni Chunchong , Noutsos Aristeidis , Okino Hiroki , Olivares Héctor , Ortiz-León Gisela N. , Oyama Tomoaki , Palumbo Daniel C. M. , Park Jongho , Pen Ue-Li , Pesce Dominic W. , Piétu Vincent , Plambeck Richard , PopStefanija Aleksandar , Porth Oliver , Prather Ben , Ramakrishnan Venkatessh , Rao Ramprasad , Rawlings Mark G. , Raymond Alexander W. , Rezzolla Luciano , Ripperda Bart , Roelofs Freek , Rogers Alan , Ros Eduardo , Rose Mel , Rottmann Helge , Ruszczyk Chet , Ryan Benjamin R. , Rygl Kazi L. J. , Sánchez Salvador , Sánchez-Arguelles David , Sasada Mahito , Savolainen Tuomas , Schloerb F. Peter , Schuster Karl-Friedrich , Shao Lijing , Shen 沈志 Zhiqiang 强 , Small Des , Sohn Bong Won , SooHoo Jason , Tazaki Fumie , Tilanus Remo P. J. , Titus Michael , Toma Kenji , Torne Pablo , Traianou Efthalia , Trippe Sascha , Tsuda Shuichiro , van Bemmel Ilse , van Langevelde Huib Jan , van Rossum Daniel R. , Wagner Jan , Wardle John , Weintroub Jonathan , Wex Norbert , Wharton Robert , Wielgus Maciek , Wong George N. , Wu 吴庆 Qingwen 文 , Yoon Doosoo , Young André , Young Ken , Younsi Ziri , Yuan 袁 Feng 峰 , Yuan 袁业 Ye-Fei 飞 , Zensus J. Anton , Zhao Guangyao , Zhao Shan-Shan , Zhu Ziyan ,   (The Event Horizon Telescope Collaboration)
Published: July 2020

Abstract
The Event Horizon Telescope (EHT) provides the unprecedented ability to directly resolve the structure and dynamics of black hole emission regions on scales smaller than their horizons. This has the potential to critically probe the mechanisms by which black holes accrete and launch outflows, and the structure of supermassive black hole spacetimes. However, accessing this information is a formidable analysis challenge for two reasons. First, the EHT natively produces a variety of data types that encode information about the image structure in nontrivial ways; these are subject to a variety of systematic effects associated with very long baseline interferometry and are supplemented by a wide variety of auxiliary data on the primary EHT targets from decades of other observations. Second, models of the emission regions and their interaction with the black hole are complex, highly uncertain, and computationally expensive to construct. As a result, the scientific utilization of EHT observations requires a flexible, extensible, and powerful analysis framework. We present such a framework, Themis, which defines a set of interfaces between models, data, and sampling algorithms that facilitates future development. We describe the design and currently existing components of Themis, how Themis has been validated thus far, and present additional analyses made possible by Themis that illustrate its capabilities. Importantly, we demonstrate that Themis is able to reproduce prior EHT analyses, extend these, and do so in a computationally efficient manner that can efficiently exploit modern high-performance computing facilities. Themis has already been used extensively in the scientific analysis and interpretation of the first EHT observations of M87.