First Very Long Baseline Interferometry Detections at 870 μm
Authors: Raymond Alexander W. , Doeleman Sheperd S. , Asada Keiichi , Blackburn Lindy , Bower Geoffrey C. , Bremer Michael , Broguiere Dominique , Chen Ming-Tang , Crew Geoffrey B. , Dornbusch Sven , Fish Vincent L. , García Roberto , Gentaz Olivier , Goddi Ciriaco , Han Chih-Chiang , Hecht Michael H. , Huang Yau-De , Janssen Michael , Keating Garrett K. , Koay Jun Yi , Krichbaum Thomas P. , Lo Wen-Ping , Matsushita Satoki , Matthews Lynn D. , Moran James M. , Norton Timothy J. , Patel Nimesh , Pesce Dominic W. , Ramakrishnan Venkatessh , Rottmann Helge , Roy Alan L. , Sánchez Salvador , Tilanus Remo P. J. , Titus Michael , Torne Pablo , Wagner Jan , Weintroub Jonathan , Wielgus Maciek , Young André , Akiyama Kazunori , Albentosa-Ruíz Ezequiel , Alberdi Antxon , Alef Walter , Algaba Juan Carlos , Anantua Richard , Azulay Rebecca , Bach Uwe , Baczko Anne-Kathrin , Ball David , Balokovic Mislav , Bandyopadhyay Bidisha , Barrett John , Bauböck Michi , Benson Bradford A. , Bintley Dan , Blundell Raymond , Bouman Katherine L. , Boyce Hope , Brissenden Roger , Britzen Silke , Broderick Avery E. , Bronzwaer Thomas , Bustamante Sandra , Carlstrom John E. , Chael Andrew , Chan Chi-kwan , Chang Dominic O. , Chatterjee Koushik , Chatterjee Shami , Chen 陈 Yongjun 永军 , Cheng Xiaopeng , Cho Ilje , Christian Pierre , Conroy Nicholas S. , Conway John E. , Crawford Thomas M. , Cruz-Osorio Alejandro , Cui 崔 Yuzhu 玉竹 , Dahale Rohan , Davelaar Jordy , De Laurentis Mariafelicia , Deane Roger , Dempsey Jessica , Desvignes Gregory , Dexter Jason , Dhruv Vedant , Dihingia Indu K. , Dzib Sergio A. , Eatough Ralph P. , Emami Razieh , Falcke Heino , Farah Joseph , Fomalont Edward , Fontana Anne-Laure , Ford H. Alyson , Foschi Marianna , Fraga-Encinas Raquel , Freeman William T. , Friberg Per , Fromm Christian M. , Fuentes Antonio , Galison Peter , Gammie Charles F. , Georgiev Boris , Gold Roman , Gómez-Ruiz Arturo I. , Gómez José L. , Gu 顾 Minfeng 敏峰 , Gurwell Mark , Hada Kazuhiro , Haggard Daryl , Hesper Ronald , Heumann Dirk , Ho 何 Luis C. 子山 , Ho Paul , Honma Mareki , Huang Chih-Wei L. , Huang 黄 Lei 磊 , Hughes David H. , Ikeda Shiro , Impellizzeri C. M. Violette , Inoue Makoto , Issaoun Sara , James David J. , Jannuzi Buell T. , Jeter Britton , Jiang 江 Wu 悟 , Jiménez-Rosales Alejandra , Johnson Michael D. , Jorstad Svetlana , Jones Adam C. , Joshi Abhishek V. , Jung Taehyun , Karuppusamy Ramesh , Kawashima Tomohisa , Kettenis Mark , Kim Dong-Jin , Kim Jae-Young , Kim Jongsoo , Kim Junhan , Kino Motoki , Kocherlakota Prashant , Kofuji Yutaro , Koch Patrick M. , Koyama Shoko , Kramer Carsten , Kramer Joana A. , Kramer Michael , Kubo Derek , Kuo Cheng-Yu , La Bella Noemi , Lee Sang-Sung , Levis Aviad , Li 李 Zhiyuan 志远 , Lico Rocco , Lindahl Greg , Lindqvist Michael , Lisakov Mikhail , Liu 刘 Jun 俊 , Liu Kuo , Liuzzo Elisabetta , Lobanov Andrei P. , Loinard Laurent , Lonsdale Colin J. , Lowitz Amy E. , Lu 路 Ru-Sen 如森 , MacDonald Nicholas R. , Mahieu Sylvain , Maier Doris , Mao 毛 Jirong 基荣 , Marchili Nicola , Markoff Sera , Marrone Daniel P. , Marscher Alan P. , Martí-Vidal Iván , Medeiros Lia , Menten Karl M. , Mizuno Izumi , Mizuno Yosuke , Montgomery Joshua , Moriyama Kotaro , Moscibrodzka Monika , Mulaudzi Wanga , Müller Cornelia , Müller Hendrik , Mus Alejandro , Musoke Gibwa , Myserlis Ioannis , Nagai Hiroshi , Nagar Neil M. , Nakamura Masanori , Narayanan Gopal , Natarajan Iniyan , Nathanail Antonios , Fuentes Santiago Navarro , Neilsen Joey , Ni Chunchong , Nowak Michael A. , Oh Junghwan , Okino Hiroki , Olivares Sánchez Héctor Raúl , Oyama Tomoaki , Özel Feryal , Palumbo Daniel C. M. , Paraschos Georgios Filippos , Park Jongho , Parsons Harriet , Pen Ue-Li , Piétu Vincent , PopStefanija Aleksandar , Porth Oliver , Prather Ben , Principe Giacomo , Psaltis Dimitrios , Pu Hung-Yi , Raffin Philippe A. , Rao Ramprasad , Rawlings Mark G. , Ricarte Angelo , Ripperda Bart , Roelofs Freek , Romero-Cañizales Cristina , Ros Eduardo , Roshanineshat Arash , Ruiz Ignacio , Ruszczyk Chet , Rygl Kazi L. J. , Sánchez-Argüelles David , Sánchez-Portal Miguel , Sasada Mahito , Satapathy Kaushik , Savolainen Tuomas , Schloerb F. Peter , Schonfeld Jonathan , Schuster Karl-Friedrich , Shao Lijing , Shen 沈 Zhiqiang 志强 , Small Des , Sohn Bong Won , SooHoo Jason , Sosapanta Salas León David , Souccar Kamal , Srinivasan Ranjani , Stanway Joshua S. , Sun 孙 He 赫 , Tazaki Fumie , Tetarenko Alexandra J. , Tiede Paul , Toma Kenji , Toscano Teresa , Traianou Efthalia , Trent Tyler , Trippe Sascha , Turk Matthew , van Bemmel Ilse , van Langevelde Huib Jan , van Rossum Daniel R. , Vos Jesse , Ward-Thompson Derek , Wardle John , Washington Jasmin E. , Wharton Robert , Wiik Kaj , Witzel Gunther , Wondrak Michael F. , Wong George N. , Wu 吴 Qingwen 庆文 , Yadlapalli Nitika , Yamaguchi Paul , Yfantis Aristomenis , Yoon Doosoo , Younsi Ziri , Yu 于 Wei 威 , Yuan 袁 Feng 峰 , Yuan 袁 Ye-Fei 业飞 , Zensus J. Anton , Zhang Shuo , Zhao Guang-Yao , Zhao 赵 Shan-Shan 杉杉 
Published: August 2024

Abstract
The first very long baseline interferometry (VLBI) detections at 870 μm wavelength (345 GHz frequency) are reported, achieving the highest diffraction-limited angular resolution yet obtained from the surface of the Earth and the highest-frequency example of the VLBI technique to date. These include strong detections for multiple sources observed on intercontinental baselines between telescopes in Chile, Hawaii, and Spain, obtained during observations in 2018 October. The longest-baseline detections approach 11 Gλ, corresponding to an angular resolution, or fringe spacing, of 19 μas. The Allan deviation of the visibility phase at 870 μm is comparable to that at 1.3 mm on the relevant integration timescales between 2 and 100 s. The detections confirm that the sensitivity and signal chain stability of stations in the Event Horizon Telescope (EHT) array are suitable for VLBI observations at 870 μm. Operation at this short wavelength, combined with anticipated enhancements of the EHT, will lead to a unique high angular resolution instrument for black hole studies, capable of resolving the event horizons of supermassive black holes in both space and time.