Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution
Authors: Kim Jae-Young , Krichbaum Thomas P. , Broderick Avery E. , Wielgus Maciek , Blackburn Lindy , Gómez José L. , Johnson Michael D. , Bouman Katherine L. , Chael Andrew , Akiyama Kazunori , Jorstad Svetlana , Marscher Alan P. , Issaoun Sara , Janssen Michael , Chan Chi-kwan , Savolainen Tuomas , Pesce Dominic W. , Özel Feryal , Alberdi Antxon , Alef Walter , Asada Keiichi , Azulay Rebecca , Baczko Anne-Kathrin , Ball David , Baloković Mislav , Barrett John , Bintley Dan , Boland Wilfred , Bower Geoffrey C. , Bremer Michael , Brinkerink Christiaan D. , Brissenden Roger , Britzen Silke , Broguiere Dominique , Bronzwaer Thomas , Byun Do-Young , Carlstrom John E. , Chatterjee Shami , Chatterjee Koushik , Chen Ming-Tang , Chen Yongjun , Cho Ilje , Christian Pierre , Conway John E. , Cordes James M. , Crew Geoffrey B. , Cui Yuzhu , Davelaar Jordy , De Laurentis Mariafelicia , Deane Roger , Dempsey Jessica , Desvignes Gregory , Dexter Jason , 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 , Gold Roman , Gómez-Ruiz Arturo I. , Gu Minfeng , Gurwell Mark , Hada Kazuhiro , Hecht Michael H. , Hesper Ronald , Ho Luis C. , Ho Paul , Honma Mareki , Huang Chih-Wei L. , Huang Lei , Hughes David H. , Ikeda Shiro , Inoue Makoto , James David J. , Jannuzi Buell T. , Jeter Britton , Jiang Wu , Jimenez-Rosales Alejandra , Jung Taehyun , Karami Mansour , Karuppusamy Ramesh , Kawashima Tomohisa , Keating Garrett K. , Kettenis Mark , Kim Junhan , Kim Jongsoo , Kino Motoki , Koay Jun Yi , Koch Patrick M. , Koyama Shoko , Kramer Michael , Kramer Carsten , Kuo Cheng-Yu , Lauer Tod R. , Lee Sang-Sung , Li Yan-Rong , Li Zhiyuan , Lindqvist Michael , Lico Rocco , Liu Kuo , Liuzzo Elisabetta , Lo Wen-Ping , Lobanov Andrei P. , Loinard Laurent , Lonsdale Colin , Lu Ru-Sen , MacDonald Nicholas R. , Mao Jirong , Markoff Sera , Marrone Daniel P. , Martí-Vidal Iván , Matsushita Satoki , Matthews Lynn D. , Medeiros Lia , Menten Karl M. , Mizuno Yosuke , Mizuno Izumi , Moran James M. , Moriyama Kotaro , Moscibrodzka Monika , Musoke Gibwa , 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 , Patel Nimesh , Pen Ue-Li , Piétu Vincent , Plambeck Richard , PopStefanija Aleksandar , Porth Oliver , Prather Ben , Preciado-López Jorge A. , Psaltis Dimitrios , Pu Hung-Yi , Ramakrishnan Venkatessh , Rao Ramprasad , Rawlings Mark G. , Raymond Alexander W. , Rezzolla Luciano , Ripperda Bart , Roelofs Freek , Rogers Alan , Ros Eduardo , Rose Mel , Roshanineshat Arash , Rottmann Helge , Roy Alan L. , Ruszczyk Chet , Ryan Benjamin R. , Rygl Kazi L. J. , Sánchez Salvador , Sánchez-Arguelles David , Sasada Mahito , Schloerb F. Peter , Schuster Karl-Friedrich , Shao Lijing , Shen Zhiqiang , Small Des , Sohn Bong Won , SooHoo Jason , Tazaki Fumie , Tiede Paul , Tilanus Remo P. J. , Titus Michael , Toma Kenji , Torne Pablo , Trent Tyler , Traianou Efthalia , Trippe Sascha , Tsuda Shuichiro , van Bemmel Ilse , van Langevelde Huib Jan , van Rossum Daniel R. , Wagner Jan , Wardle John , Ward-Thompson Derek , Weintroub Jonathan , Wex Norbert , Wharton Robert , Wong George N. , Wu Qingwen , Yoon Doosoo , Young André , Young Ken , Younsi Ziri , Yuan Feng , Yuan Ye-Fei , Zensus J. Anton , Zhao Guangyao , Zhao Shan-Shan , Zhu Ziyan , Algaba Juan-Carlos , Allardi Alexander , Amestica Rodrigo , Anczarski Jadyn , Bach Uwe , Baganoff Frederick K. , Beaudoin Christopher , Benson Bradford A. , Berthold Ryan , Blanchard Jay M. , Blundell Ray , Bustamente Sandra , Cappallo Roger , Castillo-Domínguez Edgar , Chang Chih-Cheng , Chang Shu-Hao , Chang Song-Chu , Chen Chung-Chen , Chilson Ryan , Chuter Tim C. , Rosado Rodrigo Córdova , Coulson Iain M. , Crowley Joseph , Derome Mark , Dexter Matthew , Dornbusch Sven , Dudevoir Kevin A. , Dzib Sergio A. , Eckart Andreas , Eckert Chris , Erickson Neal R. , Everett Wendeline B. , Faber Aaron , Farah Joseph R. , Fath Vernon , Folkers Thomas W. , Forbes David C. , Freund Robert , Gale David M. , Gao Feng , Geertsema Gertie , Graham David A. , Greer Christopher H. , Grosslein Ronald , Gueth Frédéric , Haggard Daryl , Halverson Nils W. , Han Chih-Chiang , Han Kuo-Chang , Hao Jinchi , Hasegawa Yutaka , Henning Jason W. , Hernández-Gómez Antonio , Herrero-Illana Rubén , Heyminck Stefan , Hirota Akihiko , Hoge James , Huang Yau-De , Violette Impellizzeri C. M. , Jiang Homin , John David , Kamble Atish , Keisler Ryan , Kimura Kimihiro , Kono Yusuke , Kubo Derek , Kuroda John , Lacasse Richard , Laing Robert A. , Leitch Erik M. , Li Chao-Te , Lin Lupin C.-C. , Liu Ching-Tang , Liu Kuan-Yu , Lu Li-Ming , Marson Ralph G. , Martin-Cocher Pierre L. , Massingill Kyle D. , Matulonis Callie , McColl Martin P. , McWhirter Stephen R. , Messias Hugo , Meyer-Zhao Zheng , Michalik Daniel , Montaña Alfredo , Montgomerie William , Mora-Klein Matias , Muders Dirk , Nadolski Andrew , Navarro Santiago , Neilsen Joseph , Nguyen Chi H. , Nishioka Hiroaki , Norton Timothy , Nowak Michael A. , Nystrom George , Ogawa Hideo , Oshiro Peter , Oyama Tomoaki , Parsons Harriet , Peñalver Juan , Phillips Neil M. , Poirier Michael , Pradel Nicolas , Primiani Rurik A. , Raffin Philippe A. , Rahlin Alexandra S. , Reiland George , Risacher Christopher , Ruiz Ignacio , Sáez-Madaín Alejandro F. , Sassella Remi , Schellart Pim , Shaw Paul , Silva Kevin M. , Shiokawa Hotaka , Smith David R. , Snow William , Souccar Kamal , Sousa Don , Sridharan Tirupati K. , Srinivasan Ranjani , Stahm William , Stark Antony A. , Story Kyle , Timmer Sjoerd T. , Vertatschitsch Laura , Walther Craig , Wei Ta-Shun , Whitehorn Nathan , Whitney Alan R. , Woody David P. , Wouterloot Jan G. A. , Wright Melvin , Yamaguchi Paul , Yu Chen-Yu , Zeballos Milagros , Zhang Shuo , Ziurys Lucy ,   The Event Horizon Telescope Collaboration
Published: April 2020

3C 279 is an archetypal blazar with a prominent radio jet that show broadband flux density variability across the entire electromagnetic spectrum. We use an ultra-high angular resolution technique – global Very Long Baseline Interferometry (VLBI) at 1.3 mm (230 GHz) – to resolve the innermost jet of 3C 279 in order to study its fine-scale morphology close to the jet base where highly variableγ-ray emission is thought to originate, according to various models. The source was observed during four days in April 2017 with the Event Horizon Telescope at 230 GHz, including the phased Atacama Large Millimeter/submillimeter Array (ALMA), at an angular resolution of ∼20 μas (at a redshift ofz = 0.536 this corresponds to ∼0.13 pc  ∼ 1700 Schwarzschild radii with a black hole massMBH = 8 × 108 M⊙). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation. We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across different imaging methods and model-fitting techniques, and therefore appears robust. Owing to its compactness and brightness, we associate the northern nuclear structure as the VLBI “core”. This morphology can be interpreted as either a broad resolved jet base or a spatially bent jet. We also find significant day-to-day variations in the closure phases, which appear most pronounced on the triangles with the longest baselines. Our analysis shows that this variation is related to a systematic change of the source structure. Two inner jet components move non-radially at apparent speeds of ∼15 cand ∼20 c(∼1.3 and ∼1.7 μas day−1, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3 mm core and the outer jet. The intrinsic brightness temperature of the jet components are ≲1010K, a magnitude or more lower than typical values seen at ≥7 mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C 279 becomes optically thin at short (mm) wavelengths.