Updated on 2023/02/05

写真a

 
KOYAMA Shiyoko
 
Organization
Academic Assembly Institute of Science and Technology Fundamental Sciences Assistant Professor
Graduate School of Science and Technology Fundamental Sciences Assistant Professor
College of Creative Studies Creative Studies Course Assistant Professor
Title
Assistant Professor
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Degree

  • 博士(理学) ( 2013.9   東京大学 )

Research Interests

  • 高エネルギー天体物理学、電波天文学、活動銀河核、ブラックホール、宇宙ジェット

Research Areas

  • Natural Science / Astronomy

Research History (researchmap)

  • 台湾中央研究院天文及天文物理研究所   Visiting Scholar

    2021.5

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  • Niigata University   Assistant Professor

    2021.4

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  • Academia Sinica Institute for Astronomy and Astrophysics   Greenland Telescope group   Postdoc fellow

    2017.4 - 2021.3

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    Country:Taiwan, Province of China

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  • Max Planck Institute for Radio Astronomy   Very Long Baseline Interferometry group   Postdoc Fellow

    2014.4 - 2017.3

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    Country:Germany

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  • The University of Tokyo   Graduate School of Science

    2013.10 - 2014.3

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Research History

  • Niigata University   Assistant Professor

    2021.4

  • Niigata University   Fundamental Sciences, Institute of Science and Technology, Academic Assembly   Assistant Professor

    2021.4

  • Niigata University   Creative Studies Course, College of Creative Studies   Assistant Professor

    2021.4

  • Niigata University   Fundamental Sciences, Graduate School of Science and Technology   Assistant Professor

    2021.4

Education

  • The University of Tokyo   Graduate School of Science Doctoral Program   Astronomy

    2010.4 - 2013.9

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    Country: Japan

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  • The University of Tokyo   Graduate School of Science   Department of Astronomy

    2008.4 - 2010.3

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    Country: Japan

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  • Waseda University   School of Science and Engineering   Physics

    2004.4 - 2008.3

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    Country: Japan

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Professional Memberships

 

Papers

  • Stable Radio Core of the Blazar Mrk 501 during High-energy Active State in 2012 Reviewed

    Shoko Koyama, Motoki Kino, Akihiro Doi, Kotaro Niinuma, Marcello Giroletti, David Paneque, Kazunori Akiyama, Gabriele Giovannini, Guang-Yao Zhao, Eduardo Ros, Jun Kataoka, Monica Orienti, Kazuhiro Hada, Hiroshi Nagai, Naoki Isobe, Hideyuki Kobayashi, Mareki Honma, Rocco Lico

    The Astrophysical Journal   884 ( 2 )   132 - 132   2019.10

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    Authorship:Lead author   Publishing type:Research paper (scientific journal)   Publisher:American Astronomical Society  

    DOI: 10.3847/1538-4357/ab4260

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    Other Link: https://iopscience.iop.org/article/10.3847/1538-4357/ab4260

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

    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

    The Astrophysical Journal   875 ( 1 )   L4 - L4   2019.4

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    Publishing type:Research paper (scientific journal)   Publisher:American Astronomical Society  

    DOI: 10.3847/2041-8213/ab0e85

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    Other Link: https://iopscience.iop.org/article/10.3847/2041-8213/ab0e85

  • Discovery of off-axis jet structure of TeV blazar Mrk 501 with mm-VLBI Reviewed

    S. Koyama, M. Kino, M. Giroletti, A. Doi, G. Giovannini, M. Orienti, K. Hada, E. Ros, K. Niinuma, H. Nagai, T. Savolainen, T. P. Krichbaum, M. Á. Pérez-Torres

    Astronomy & Astrophysics   586   A113 - A113   2016.2

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:EDP Sciences  

    Context. High-resolution millimeter wave very-long-baseline interferometry (mm-VLBI) is an ideal tool for probing the structure at the base of extragalactic jets in detail. The TeV blazar Mrk 501 is one of the best targets among BL Lac objects for studying the nature of off-axis jet structures because it shows different jet position angles at different scales. Aims. The aim of this study is to investigate the properties of the off-axis jet structure through high-resolution mm-VLBI images at the jet base and physical parameters such as kinematics, flux densities, and spectral indices. Methods. We performed Very Long Baseline Array (VLBA) observations over six epochs from 2012 February to 2013 February at 43 GHz. Quasi-simultaneous Global Millimeter VLBI Array (GMVA) observations at 86 GHz were performed in May 2012. Results. We discover a new jet component at the northeast direction from the core in all the images at 43 and 86 GHz. The new component shows the off-axis location from the persistent jet extending to the southeast. The 43 GHz images reveal that the scattering of the positions of the NE component is within ∼0.2 mas. The 86 GHz data reveals a jet component located 0.75 mas southeast of the radio core. We also discuss the spectral indices between 43 and 86 GHz, where the northeast component has steeper spectral index and the southeast component has comparable or flatter index than the radio core does.

    DOI: 10.1051/0004-6361/201526541

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  • Probing the precise location of the radio core in the TeV blazar Mrk 501 with VERA at 43 GHz Reviewed

    Shoko Koyama, Motoki Kino, Akihiro Doi, Kotaro Niinuma, Kazuhiro Hada, Hiroshi Nagai, Mareki Honma, Kazunori Akiyama, Marcello Giroletti, Gabriele Giovannini, Monica Orienti, Naoki Isobe, Jun Kataoka, David Paneque, Hideyuki Kobayashi, Keiichi Asada

    Publications of the Astronomical Society of Japan   67 ( 4 )   67 - 67   2015.8

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Oxford University Press (OUP)  

    We investigate the position of the radio core in a blazar by multi-epoch astrometric observations at 43 GHz. Using the VLBI Exploration of Radio Astrometry (VERA), we have conducted four adjacent observations in 2011 February and another four in 2011 October, and succeeded in measuring the position of the radio core in the TeV blazar Mrk 501 relative to a distant compact quasar NRAO 512. During our observations, we find that (1) there is no positional change within ∼0.2 mas or ∼2.0 pc de-projected with ±1 σ error for the weighted-mean phase-referenced positions of the Mrk 501 core relative to NRAO 512 over four adjacent days, and (2) there is an indication of position change for the 3C 345 core relative to NRAO 512. By applying our results to the standard internal shock model for blazars, we constrain the bulk Lorenz factors of the ejecta.

    DOI: 10.1093/pasj/psu144

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  • Millimeter Light Curves of Sagittarius A* Observed during the 2017 Event Horizon Telescope Campaign

    Maciek Wielgus, Nicola Marchili, Ivan Marti-Vidal, Garrett K. Keating, Venkatessh Ramakrishnan, Paul Tiede, Ed Fomalont, Sara Issaoun, Joey Neilsen, Michael A. Nowak, Lindy Blackburn, Charles F. Gammie, Ciriaco Goddi, Daryl Haggard, Daeyoung Lee, Monika Moscibrodzka, Alexandra J. Tetarenko, Geoffrey C. Bower, Chi-kwan Chan, Koushik Chatterjee, Paul M. Chesler, Jason Dexter, Sheperd S. Doeleman, Boris Georgiev, Mark Gurwell, Michael D. Johnson, Daniel P. Marrone, Alejandro Mus, Dimitrios Psaltis, Bart Ripperda, Gunther Witzel, Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, David Ball, Mislav Balokovic, John Barrett, Michi Baubock, Bradford A. Benson, Dan Bintley, Raymond Blundell, Wilfred Boland, Katherine L. Bouman, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Avery E. Broderick, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamante, Do-Young Byun, John E. Carlstrom, Chiara Ceccobello, Andrew Chael, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Ilje Cho, Pierre Christian, Nicholas S. Conroy, 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, Vedant Dhruv, Sergio A. Dzib, Ralph P. Eatough, Razieh Emami, Heino Falcke, Joseph Farah, Vincent L. Fish, H. Alyson Ford, Raquel Fraga-Encinas, William T. Freeman, Per Friberg, Christian M. Fromm, Antonio Fuentes, Peter Galison, Roberto Garcia, Olivier Gentaz, Roman Gold, Arturo Gomez-Ruiz, Jose L. Gomez, Minfeng Gu, Kazuhiro Hada, Kari Haworth, Michael H. Hecht, Ronald Hesper, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Shiro Ikeda, C. M. Violette Impellizzeri, Makoto Inoue, David J. James, Buell T. Jannuzi, Michael Janssen, Britton Jeter, Wu Jiang, Alejandra Jimenez-Rosales, Svetlana Jorstad, Abhishek Joshi, Taehyun Jung, Mansour Karami, Ramesh Karuppusamy, Tomohisa Kawashima, Mark Kettenis, Dong-Jin Kim, Jae-Young Kim, Jongsoo Kim, Junhan Kim, Motoki Kino, Jun Yi Koay, Prashant Kocherlakota, Yutaro Kofuji, Patrick M. Koch, Shoko Koyama, Carsten Kramer, Michael Kramer, Thomas P. Krichbaum, Cheng-Yu Kuo, Noemi La Bella, Tod R. Lauer, Sang-Sung Lee, Po Kin Leung, Aviad Levis, Zhiyuan Li, Rocco Lico, Greg Lindahl, Michael Lindqvist, Mikhail Lisakov, Jun Liu, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin Lonsdale, Ru-Sen Lu, Jirong Mao, Sera Markoff, Alan P. Marscher, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Daniel Michalik, Izumi Mizuno, Yosuke Mizuno, James M. Moran, Kotaro Moriyama, Cornelia Mueller, Gibwa Musoke, Ioannis Myserlis, Andrew Nadolski, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Antonios Nathanail, Santiago Navarro Fuentes, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Junghwan Oh, Hiroki Okino, Hector Olivares, Gisela N. Ortiz-Leon, Tomoaki Oyama, Feryal Ozel, Daniel C. M. Palumbo, Georgios Filippos Paraschos, Jongho Park, Harriet Parsons, Nimesh Patel, Ue-Li Pen, Dominic W. Pesce, Vincent Pietu, Richard Plambeck, Aleksandar PopStefanija, Oliver Porth, Felix M. Potzl, Ben Prather, Jorge A. Preciado-Lopez, Hung-Yi Pu, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, Luciano Rezzolla, Angelo Ricarte, Freek Roelofs, Alan Rogers, Eduardo Ros, Cristina Romero-Canizales, Arash Roshanineshat, Helge Rottmann, Alan L. Roy, Ignacio Ruiz, Chet Ruszczyk, Kazi L. J. Rygl, Salvador Sanchez, David Sanchez-Arguelles, Miguel Sanchez-Portal, Mahito Sasada, Kaushik Satapathy, Tuomas Savolainen, F. Peter Schloerb, Karl-Friedrich Schuster, Lijing Shao, Zhiqiang Shen, Des Small, Bong Won Sohn, Jason SooHoo, Kamal Souccar, He Sun, Fumie Tazaki, Remo P. J. Tilanus, Michael Titus, Pablo Torne, Efthalia Traianou, Tyler Trent, Sascha Trippe, Ilse van Bemmel, Huib Jan van Langevelde, Daniel R. van Rossum, Jesse Vos, Jan Wagner, Derek Ward-Thompson, John Wardle, Jonathan Weintroub, Norbert Wex, Robert Wharton, Kaj Wiik, Michael F. Wondrak, George N. Wong, Qingwen Wu, Paul Yamaguchi, Doosoo Yoon, Andre Young, Ken Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Shuo Zhang, Guang-Yao Zhao, Shan-Shan Zhao

    ASTROPHYSICAL JOURNAL LETTERS   930 ( 2 )   2022.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing Ltd  

    The Event Horizon Telescope (EHT) observed the compact radio source, Sagittarius A* (Sgr A*), in the Galactic Center on 2017 April 5-11 in the 1.3 mm wavelength band. At the same time, interferometric array data from the Atacama Large Millimeter/submillimeter Array and the Submillimeter Array were collected, providing Sgr A* light curves simultaneous with the EHT observations. These data sets, complementing the EHT very long baseline interferometry, are characterized by a cadence and signal-to-noise ratio previously unattainable for Sgr A* at millimeter wavelengths, and they allow for the investigation of source variability on timescales as short as a minute. While most of the light curves correspond to a low variability state of Sgr A*, the April 11 observations follow an X-ray flare and exhibit strongly enhanced variability. All of the light curves are consistent with a red-noise process, with a power spectral density (PSD) slope measured to be between -2 and -3 on timescales between 1 minute and several hours. Our results indicate a steepening of the PSD slope for timescales shorter than 0.3 hr. The spectral energy distribution is flat at 220 GHz, and there are no time lags between the 213 and 229 GHz frequency bands, suggesting low optical depth for the event horizon scale source. We characterize Sgr A*'s variability, highlighting the different behavior observed just after the X-ray flare, and use Gaussian process modeling to extract a decorrelation timescale and a PSD slope. We also investigate the systematic calibration uncertainties by analyzing data from independent data reduction pipelines.

    DOI: 10.3847/2041-8213/ac6428

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  • Selective Dynamical Imaging of Interferometric Data

    Joseph Farah, Peter Galison, Kazunori Akiyama, Katherine L. Bouman, Geoffrey C. Bower, Andrew Chael, Antonio Fuentes, Jose L. Gomez, Mareki Honma, Michael D. Johnson, Yutaro Kofuji, Daniel P. Marrone, Kotaro Moriyama, Ramesh Narayan, Dominic W. Pesce, Paul Tiede, Maciek Wielgus, Guang-Yao Zhao, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Anne-Kathrin Baczkovic, David Ball, Mislay Balokovic, John Barrett, Bradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Wilfred Boland, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Avery E. Broderick, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamente, Do-Young Byun, John E. Carlstrom, Chi-kwan Chan, Koushik Chatterjee, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, 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, Sheperd S. Doeleman, Ralph P. Eatough, Heino Falcke, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Raquel Fraga-Encinas, Per Friberg, Christian M. Fromm, Charles F. Gammie, Roberto Garc'a, Olivier Gentaz, Ciriaco Goddi, Roman Gold, Arturo Gomez-Ruiz, Minfeng Gu, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Michael H. Hecht, Ronald Hesper, Luis C. Ho, Paul Ho, 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, Patrick M. Koch, Shoko Koyama, Carsten Kramer, Michael Kramer, Thomas P. Krichbaum, Cheng-Yu Kuo, Tod R. Lauer, Sang-Sung Lee, Aviad Levis, Yan-Rong Li, Zhiyuan Li, Rocco Lico, Greg Lindahl, Michael Lindqvist, 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, Alan P. Marscher, Ivan Marti-Vidal, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Izumi Mizuno, Yosuke Mizuno, James M. Moran, Monika Moscibrodzka, Cornelia Muller, Alejandro Mus Mejas, Gibwa Musoke, 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, Hector Olivares, Gisela N. Ortiz-Leon, Tomoaki Oyama, Feryal Zel, Daniel C. M. Palumbo, Jongho Park, Nimesh Patel, Ue-Li Pen, Vincent Pietu, Richard Plambeck, Aleksandar PopStefanija, Oliver Porth, Felix M. Potzl, Ben Prather, Jorge A. Preciado-Lopez, 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 Sanchez, David Sanchez-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, Remo P. J. Tilanus, Michael Titus, Kenji Toma, Pablo Torne, Efthalia Traianou, Tyler Trent, 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, Kaj Wiik, George N. Wong, Qingwen Wu, Doosoo Yoon, Andre Young, Ken Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Shan-Shan Zhao

    ASTROPHYSICAL JOURNAL LETTERS   930 ( 2 )   2022.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing Ltd  

    Recent developments in very long baseline interferometry (VLBI) have made it possible for the Event Horizon Telescope (EHT) to resolve the innermost accretion flows of the largest supermassive black holes on the sky. The sparse nature of the EHT's (u, v)-coverage presents a challenge when attempting to resolve highly time-variable sources. We demonstrate that the changing (u, v)-coverage of the EHT can contain regions of time over the course of a single observation that facilitate dynamical imaging. These optimal time regions typically have projected baseline distributions that are approximately angularly isotropic and radially homogeneous. We derive a metric of coverage quality based on baseline isotropy and density that is capable of ranking array configurations by their ability to produce accurate dynamical reconstructions. We compare this metric to existing metrics in the literature and investigate their utility by performing dynamical reconstructions on synthetic data from simulated EHT observations of sources with simple orbital variability. We then use these results to make recommendations for imaging the 2017 EHT Sgr A* data set.

    DOI: 10.3847/2041-8213/ac6615

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  • Characterizing and Mitigating Intraday Variability: Reconstructing Source Structure in Accreting Black Holes with mm-VLBI

    Avery E. Broderick, Roman Gold, Boris Georgiev, Dominic W. Pesce, Paul Tiede, Chunchong Ni, Kotaro Moriyama, Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, David Ball, Mislav Balokovic, John Barrett, Michi Baubock, Bradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Katherine L. Bouman, Geoffrey C. Bower, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamante, Do-Young Byun, John E. Carlstrom, Chiara Ceccobello, Andrew Chael, Chi-kwan Chan, Koushik Chatterjee, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Xiaopeng Cheng, Ilje Cho, Pierre Christian, Nicholas S. Conroy, 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, Jason Dexter, Vedant Dhruv, Sheperd S. Doeleman, Sean Dougal, Sergio A. Dzib, Ralph P. Eatough, Razieh Emami, Heino Falcke, Joseph Farah, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Raquel Fraga-Encinas, William T. Freeman, Per Friberg, Christian M. Fromm, Antonio Fuentes, Peter Galison, Charles F. Gammie, Roberto Garcia, Olivier Gentaz, Ciriaco Goddi, Arturo Gomez-Ruiz, Jose L. Gomez, Minfeng Gu, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Kari Haworth, Michael H. Hecht, Ronald Hesper, Dirk Heumann, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Shiro Ikeda, C. M. Violette Impellizzeri, Makoto Inoue, Sara Issaoun, David J. James, Buell T. Jannuzi, Michael Janssen, Britton Jeter, Wu Jiang, Alejandra Jimenez-Rosales, Michael D. Johnson, Svetlana Jorstad, Abhishek Joshi, 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, Prashant Kocherlakota, Yutaro Kofuji, Patrick M. Koch, Shoko Koyama, Carsten Kramer, Michael Kramer, Thomas P. Krichbaum, Cheng-Yu Kuo, Noemi La Bella, Tod R. Lauer, Daeyoung Lee, Sang-Sung Lee, Po Kin Leung, Aviad Levis, Zhiyuan Li, Rocco Lico, Greg Lindahl, Michael Lindqvist, Mikhail Lisakov, Jun Liu, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin J. Lonsdale, Ru-Sen Lu, Jirong Mao, Nicola Marchili, Sera Markoff, Daniel P. Marrone, Alan P. Marscher, Ivan Marti-Vidal, Satoki Matsushita, Lynn D. Matthews, Karl M. Menten, Daniel Michalik, Izumi Mizuno, Yosuke Mizuno, James M. Moran, Monika Moscibrodzka, Cornelia Muller, Alejandro Mus, Gibwa Musoke, Ioannis Myserlis, Andrew Nadolski, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Antonios Nathanail, Santiago Navarro Fuentes, Joey Neilsen, Roberto Neri, Aristeidis Noutsos, Michael A. Nowak, Junghwan Oh, Hiroki Okino, Hector Olivares, Gisela N. Ortiz-Leon, Tomoaki Oyama, Daniel C. M. Palumbo, Georgios Filippos Paraschos, Jongho Park, Harriet Parsons, Nimesh Patel, Ue-Li Pen, Vincent Pietu, Richard Plambeck, Aleksandar PopStefanija, Oliver Porth, Felix M. Potzl, Ben Prather, Jorge A. Preciado-Lopez, Hung-Yi Pu, Venkatessh Ramakrishnan, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, Luciano Rezzolla, Angelo Ricarte, Bart Ripperda, Freek Roelofs, Alan Rogers, Eduardo Ros, Cristina Romero-Canizales, Arash Roshanineshat, Helge Rottmann, Alan L. Roy, Ignacio Ruiz, Chet Ruszczyk, Kazi L. J. Rygl, Salvador Sanchez, David Sanchez-Arguelles, Miguel Sanchez-Portal, Mahito Sasada, Kaushik Satapathy, Tuomas Savolainen, F. Peter Schloerb, Jonathan Schonfeld, Karl-Friedrich Schuster, Lijing Shao, Zhiqiang Shen, Des Small, Bong Won Sohn, Jason SooHoo, Kamal Souccar, He Sun, Fumie Tazaki, Alexandra J. Tetarenko, Remo P. J. Tilanus, Michael Titus, Pablo Torne, Efthalia Traianou, Tyler Trent, Sascha Trippe, Matthew Turk, Ilse van Bemmel, Huib Jan van Langevelde, Daniel R. van Rossum, Jesse Vos, Jan Wagner, Derek Ward-Thompson, John Wardle, Jonathan Weintroub, Norbert Wex, Robert Wharton, Maciek Wielgus, Kaj Wiik, Gunther Witzel, Michael F. Wondrak, George N. Wong, Qingwen Wu, Paul Yamaguchi, Doosoo Yoon, Andre Young, Ken Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Guang-Yao Zhao, Shuo Zhang, Shan-Shan Zhao

    ASTROPHYSICAL JOURNAL LETTERS   930 ( 2 )   2022.5

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    The extraordinary physical resolution afforded by the Event Horizon Telescope has opened a window onto the astrophysical phenomena unfolding on horizon scales in two known black holes, M87* and Sgr A*. However, with this leap in resolution has come a new set of practical complications. Sgr A* exhibits intraday variability that violates the assumptions underlying Earth aperture synthesis, limiting traditional image reconstruction methods to short timescales and data sets with very sparse (u, v) coverage. We present a new set of tools to detect and mitigate this variability. We develop a data-driven, model-agnostic procedure to detect and characterize the spatial structure of intraday variability. This method is calibrated against a large set of mock data sets, producing an empirical estimator of the spatial power spectrum of the brightness fluctuations. We present a novel Bayesian noise modeling algorithm that simultaneously reconstructs an average image and statistical measure of the fluctuations about it using a parameterized form for the excess variance in the complex visibilities not otherwise explained by the statistical errors. These methods are validated using a variety of simulated data, including general relativistic magnetohydrodynamic simulations appropriate for Sgr A* and M87*. We find that the reconstructed source structure and variability are robust to changes in the underlying image model. We apply these methods to the 2017 EHT observations of M87*, finding evidence for variability across the EHT observing campaign. The variability mitigation strategies presented are widely applicable to very long baseline interferometry observations of variable sources generally, for which they provide a data-informed averaging procedure and natural characterization of inter-epoch image consistency.

    DOI: 10.3847/2041-8213/ac6584

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  • First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole

    Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, David Ball, Mislav Balokovic, John Barrett, Michi Baubock, Bradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Katherine L. Bouman, Geoffrey C. Bower, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Avery E. Broderick, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamante, Do-Young Byun, John E. Carlstrom, Chiara Ceccobello, Andrew Chael, Chi-kwan Chan, Koushik Chatterjee, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Xiaopeng Cheng, Ilje Cho, Pierre Christian, Nicholas S. Conroy, 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, Jason Dexter, Vedant Dhruv, Sheperd S. Doeleman, Sean Dougal, Sergio A. Dzib, Ralph P. Eatough, Razieh Emami, Heino Falcke, Joseph Farah, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Raquel Fraga-Encinas, William T. Freeman, Per Friberg, Christian M. Fromm, Antonio Fuentes, Peter Galison, Charles F. Gammie, Roberto Garcia, Olivier Gentaz, Boris Georgiev, Ciriaco Goddi, Roman Gold, Arturo Gomez-Ruiz, Jose L. Gomez, Minfeng Gu, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Kari Haworth, Michael H. Hecht, Ronald Hesper, Dirk Heumann, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Shiro Ikeda, C. M. Violette Impellizzeri, Makoto Inoue, Sara Issaoun, David J. James, Buell T. Jannuzi, Michael Janssen, Britton Jeter, Wu Jiang, Alejandra Jimenez-Rosales, Michael D. Johnson, Svetlana Jorstad, Abhishek Joshi, 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, Prashant Kocherlakota, Yutaro Kofuji, Patrick M. Koch, Shoko Koyama, Carsten Kramer, Michael Kramer, Thomas P. Krichbaum, Cheng-Yu Kuo, Noemi La Bella, Tod R. Lauer, Daeyoung Lee, Sang-Sung Lee, Po Kin Leung, Aviad Levis, Zhiyuan Li, Rocco Lico, Greg Lindahl, Michael Lindqvist, Mikhail Lisakov, Jun Liu, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin J. Lonsdale, Ru-Sen Lu, Jirong Mao, Nicola Marchili, Sera Markoff, Daniel P. Marrone, Alan P. Marscher, Ivan Marti-Vidal, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Daniel Michalik, Izumi Mizuno, Yosuke Mizuno, James M. Moran, Kotaro Moriyama, Monika Moscibrodzka, Cornelia Mueller, Alejandro Mus, Gibwa Musoke, Ioannis Myserlis, Andrew Nadolski, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Antonios Nathanail, Santiago Navarro Fuentes, Joey Neilsen, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Michael A. Nowak, Junghwan Oh, Hiroki Okino, Hector Olivares, Gisela N. Ortiz-Leon, Tomoaki Oyama, Feryal Ozel, Daniel C. M. Palumbo, Georgios Filippos Paraschos, Jongho Park, Harriet Parsons, Nimesh Patel, Ue-Li Pen, Dominic W. Pesce, Vincent Pietu, Richard Plambeck, Aleksandar PopStefanija, Oliver Porth, Felix M. Potzl, Ben Prather, Jorge A. Preciado-Lopez, Dimitrios Psaltis, Hung-Yi Pu, Venkatessh Ramakrishnan, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, Luciano Rezzolla, Angelo Ricarte, Bart Ripperda, Freek Roelofs, Alan Rogers, Eduardo Ros, Cristina Romero-Canizales, Arash Roshanineshat, Helge Rottmann, Alan L. Roy, Ignacio Ruiz, Chet Ruszczyk, Kazi L. J. Rygl, Salvador Sanchez, David Sanchez-Arguelles, Miguel Sanchez-Portal, Mahito Sasada, Kaushik Satapathy, Tuomas Savolainen, F. Peter Schloerb, Jonathan Schonfeld, Karl-Friedrich Schuster, Lijing Shao, Zhiqiang Shen, Des Small, Bong Won Sohn, Jason SooHoo, Kamal Souccar, He Sun, Fumie Tazaki, Alexandra J. Tetarenko, Paul Tiede, Remo P. J. Tilanus, Michael Titus, Pablo Torne, Efthalia Traianou, Tyler Trent, Sascha Trippe, Matthew Turk, Ilse van Bemmel, Huib Jan van Langevelde, Daniel R. van Rossum, Jesse Vos, Jan Wagner, Derek Ward-Thompson, John Wardle, Jonathan Weintroub, Norbert Wex, Robert Wharton, Maciek Wielgus, Kaj Wiik, Gunther Witzel, Michael F. Wondrak, George N. Wong, Qingwen Wu, Paul Yamaguchi, Doosoo Yoon, Andre Young, Ken Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Shuo Zhang, Guang-Yao Zhao, Shan-Shan Zhao, Tin Lok Chan, Richard Qiu, Sean Ressler, Chris White

    ASTROPHYSICAL JOURNAL LETTERS   930 ( 2 )   2022.5

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    In this paper we provide a first physical interpretation for the Event Horizon Telescope's (EHT) 2017 observations of Sgr A*. Our main approach is to compare resolved EHT data at 230 GHz and unresolved non-EHT observations from radio to X-ray wavelengths to predictions from a library of models based on time-dependent general relativistic magnetohydrodynamics simulations, including aligned, tilted, and stellar-wind-fed simulations; radiative transfer is performed assuming both thermal and nonthermal electron distribution functions. We test the models against 11 constraints drawn from EHT 230 GHz data and observations at 86 GHz, 2.2 mu m, and in the X-ray. All models fail at least one constraint. Light-curve variability provides a particularly severe constraint, failing nearly all strongly magnetized (magnetically arrested disk (MAD)) models and a large fraction of weakly magnetized models. A number of models fail only the variability constraints. We identify a promising cluster of these models, which are MAD and have inclination i <= 30 degrees. They have accretion rate (5.2-9.5) x 10(-9) M (circle dot) yr(-1), bolometric luminosity (6.8-9.2) x 10(35) erg s(-1), and outflow power (1.3-4.8) x 10(38) erg s(-1). We also find that all models with i >= 70 degrees fail at least two constraints, as do all models with equal ion and electron temperature; exploratory, nonthermal model sets tend to have higher 2.2 mu m flux density; and the population of cold electrons is limited by X-ray constraints due to the risk of bremsstrahlung overproduction. Finally, we discuss physical and numerical limitations of the models, highlighting the possible importance of kinetic effects and duration of the simulations.

    DOI: 10.3847/2041-8213/ac6672

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  • First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass

    Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, David Ball, Mislav Balokovic, John Barrett, Michi Baubock, Bradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Katherine L. Bouman, Geoffrey C. Bower, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Avery E. Broderick, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamante, Do-Young Byun, John E. Carlstrom, Chiara Ceccobello, Andrew Chael, Chi-kwan Chan, Koushik Chatterjee, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Xiaopeng Cheng, Ilje Cho, Pierre Christian, Nicholas S. Conroy, 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, Jason Dexter, Vedant Dhruv, Sheperd S. Doeleman, Sean Dougal, Sergio A. Dzib, Ralph P. Eatough, Razieh Emami, Heino Falcke, Joseph Farah, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Raquel Fraga-Encinas, William T. Freeman, Per Friberg, Christian M. Fromm, Antonio Fuentes, Peter Galison, Charles F. Gammie, Roberto Garcia, Olivier Gentaz, Boris Georgiev, Ciriaco Goddi, Roman Gold, Arturo Gomez-Ruiz, Jose L. Gomez, Minfeng Gu, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Kari Haworth, Michael H. Hecht, Ronald Hesper, Dirk Heumann, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Shiro Ikeda, C. M. Violette Impellizzeri, Makoto Inoue, Sara Issaoun, David J. James, Buell T. Jannuzi, Michael Janssen, Britton Jeter, Wu Jiang, Alejandra Jimenez-Rosales, Michael D. Johnson, Svetlana Jorstad, Abhishek Joshi, 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, Prashant Kocherlakota, Yutaro Kofuji, Patrick M. Koch, Shoko Koyama, Carsten Kramer, Michael Kramer, Thomas P. Krichbaum, Cheng-Yu Kuo, Noemi La Bella, Tod R. Lauer, Daeyoung Lee, Sang-Sung Lee, Po Kin Leung, Aviad Levis, Zhiyuan Li, Rocco Lico, Greg Lindahl, Michael Lindqvist, Mikhail Lisakov, Jun Liu, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin J. Lonsdale, Ru-Sen Lu, Jirong Mao, Nicola Marchili, Sera Markoff, Daniel P. Marrone, Alan P. Marscher, Ivan Marti-Vidal, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Daniel Michalik, Izumi Mizuno, Yosuke Mizuno, James M. Moran, Kotaro Moriyama, Monika Moscibrodzka, Cornelia Muller, Alejandro Mus, Gibwa Musoke, Ioannis Myserlis, Andrew Nadolski, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Antonios Nathanail, Santiago Navarro Fuentes, Joey Neilsen, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Michael A. Nowak, Junghwan Oh, Hiroki Okino, Hector Olivares, Gisela N. Ortiz-Leon, Tomoaki Oyama, Daniel C. M. Palumbo, Georgios Filippos Paraschos, Jongho Park, Harriet Parsons, Nimesh Patel, Ue-Li Pen, Dominic W. Pesce, Vincent Pietu, Richard Plambeck, Aleksandar PopStefanija, Oliver Porth, Felix M. Potzl, Ben Prather, Jorge A. Preciado-Lopez, Hung-Yi Pu, Venkatessh Ramakrishnan, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, Luciano Rezzolla, Angelo Ricarte, Bart Ripperda, Freek Roelofs, Alan Rogers, Eduardo Ros, Cristina Romero-Canizales, Arash Roshanineshat, Helge Rottmann, Alan L. Roy, Ignacio Ruiz, Chet Ruszczyk, Kazi L. J. Rygl, Salvador Sanchez, David Sanchez-Arguelles, Miguel Sanchez-Portal, Mahito Sasada, Kaushik Satapathy, Tuomas Savolainen, F. Peter Schloerb, Jonathan Schonfeld, Karl-Friedrich Schuster, Lijing Shao, Zhiqiang Shen, Des Small, Bong Won Sohn, Jason SooHoo, Kamal Souccar, He Sun, Fumie Tazaki, Alexandra J. Tetarenko, Paul Tiede, Remo P. J. Tilanus, Michael Titus, Pablo Torne, Efthalia Traianou, Tyler Trent, Sascha Trippe, Matthew Turk, Ilse van Bemmel, Huib Jan van Langevelde, Daniel R. van Rossum, Jesse Vos, Jan Wagner, Derek Ward-Thompson, John Wardle, Jonathan Weintroub, Norbert Wex, Robert Wharton, Maciek Wielgus, Kaj Wiik, Gunther Witzel, Michael F. Wondrak, George N. Wong, Qingwen Wu, Paul Yamaguchi, Doosoo Yoon, Andre Young, Ken Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Shuo Zhang, Guang-Yao Zhao, Shan-Shan Zhao, Dominic O. Chang

    ASTROPHYSICAL JOURNAL LETTERS   930 ( 2 )   2022.5

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    In this paper we quantify the temporal variability and image morphology of the horizon-scale emission from Sgr A*, as observed by the EHT in 2017 April at a wavelength of 1.3 mm. We find that the Sgr A* data exhibit variability that exceeds what can be explained by the uncertainties in the data or by the effects of interstellar scattering. The magnitude of this variability can be a substantial fraction of the correlated flux density, reaching similar to 100% on some baselines. Through an exploration of simple geometric source models, we demonstrate that ring-like morphologies provide better fits to the Sgr A* data than do other morphologies with comparable complexity. We develop two strategies for fitting static geometric ring models to the time-variable Sgr A* data; one strategy fits models to short segments of data over which the source is static and averages these independent fits, while the other fits models to the full data set using a parametric model for the structural variability power spectrum around the average source structure. Both geometric modeling and image-domain feature extraction techniques determine the ring diameter to be 51.8 +/- 2.3 mu as (68% credible intervals), with the ring thickness constrained to have an FWHM between similar to 30% and 50% of the ring diameter. To bring the diameter measurements to a common physical scale, we calibrate them using synthetic data generated from GRMHD simulations. This calibration constrains the angular size of the gravitational radius to be 4.8(-0.7)(+1.4) mu as, which we combine with an independent distance measurement from maser parallaxes to determine the mass of Sgr A* to be 4.0(-0.6)(+1.1) x 10(6) M-circle dot.

    DOI: 10.3847/2041-8213/ac6736

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  • First Sagittarius A* Event Horizon Telescope Results. III. Imaging of the Galactic Center Supermassive Black Hole

    Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, David Ball, Mislav Balokovic, John Barrett, Michi Baubock, Bradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Katherine L. Bouman, Geoffrey C. Bower, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Avery E. Broderick, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamante, Do-Young Byun, John E. Carlstrom, Chiara Ceccobello, Andrew Chael, Chi-kwan Chan, Koushik Chatterjee, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Xiaopeng Cheng, Ilje Cho, Pierre Christian, Nicholas S. Conroy, 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, Jason Dexter, Vedant Dhruv, Sheperd S. Doeleman, Sean Dougal, Sergio A. Dzib, Ralph P. Eatough, Razieh Emami, Heino Falcke, Joseph Farah, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Raquel Fraga-Encinas, William T. Freeman, Per Friberg, Christian M. Fromm, Antonio Fuentes, Peter Galison, Charles F. Gammie, Roberto Garcia, Olivier Gentaz, Boris Georgiev, Ciriaco Goddi, Roman Gold, Arturo Gomez-Ruiz, Jose L. Gomez, Minfeng Gu, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Kari Haworth, Michael H. Hecht, Ronald Hesper, Dirk Heumann, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Shiro Ikeda, C. M. Violette Impellizzeri, Makoto Inoue, Sara Issaoun, David J. James, Buell T. Jannuzi, Michael Janssen, Britton Jeter, Wu Jiang, Alejandra Jimenez-Rosales, Michael D. Johnson, Svetlana Jorstad, Abhishek Joshi, 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, Prashant Kocherlakota, Yutaro Kofuji, Patrick M. Koch, Shoko Koyama, Carsten Kramer, Michael Kramer, Thomas P. Krichbaum, Cheng-Yu Kuo, Noemi La Bella, Tod R. Lauer, Daeyoung Lee, Sang-Sung Lee, Po Kin Leung, Aviad Levis, Zhiyuan Li, Rocco Lico, Greg Lindahl, Michael Lindqvist, Mikhail Lisakov, Jun Liu, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin J. Lonsdale, Ru-Sen Lu, Jirong Mao, Nicola Marchili, Sera Markoff, Daniel P. Marrone, Alan P. Marscher, Ivan Marti-Vidal, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Daniel Michalik, Izumi Mizuno, Yosuke Mizuno, James M. Moran, Kotaro Moriyama, Monika Moscibrodzka, Cornelia Mueller, Alejandro Mus, Gibwa Musoke, Ioannis Myserlis, Andrew Nadolski, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Antonios Nathanail, Santiago Navarro Fuentes, Joey Neilsen, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Michael A. Nowak, Junghwan Oh, Hiroki Okino, Hector Olivares, Gisela N. Ortiz-Leon, Tomoaki Oyama, Feryal Ozel, Daniel C. M. Palumbo, Georgios Filippos Paraschos, Jongho Park, Harriet Parsons, Nimesh Patel, Ue-Li Pen, Dominic W. Pesce, Vincent Pietu, Richard Plambeck, Aleksandar PopStefanija, Oliver Porth, Felix M. Potzl, Ben Prather, Jorge A. Preciado-Lopez, Dimitrios Psaltis, Hung-Yi Pu, Venkatessh Ramakrishnan, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, Luciano Rezzolla, Angelo Ricarte, Bart Ripperda, Freek Roelofs, Alan Rogers, Eduardo Ros, Cristina Romero-Canizales, Arash Roshanineshat, Helge Rottmann, Alan L. Roy, Ignacio Ruiz, Chet Ruszczyk, Kazi L. J. Rygl, Salvador Sanchez, David Sanchez-Arguelles, Miguel Sanchez-Portal, Mahito Sasada, Kaushik Satapathy, Tuomas Savolainen, F. Peter Schloerb, Jonathan Schonfeld, Karl-Friedrich Schuster, Lijing Shao, Zhiqiang Shen, Des Small, Bong Won Sohn, Jason SooHoo, Kamal Souccar, Fumie Tazaki, Alexandra J. Tetarenko, Paul Tiede, Remo P. J. Tilanus, Michael Titus, Pablo Torne, Efthalia Traianou, Tyler Trent, Sascha Trippe, Matthew Turk, Ilse van Bemmel, Huib Jan van Langevelde, Daniel R. van Rossum, Jesse Vos, Jan Wagner, Derek Ward-Thompson, John Wardle, Jonathan Weintroub, Norbert Wex, Robert Wharton, Maciek Wielgus, Kaj Wiik, Gunther Witzel, Michael F. Wondrak, George N. Wong, Qingwen Wu, Paul Yamaguchi, Doosoo Yoon, Andre Young, Ken Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Shuo Zhang, Guang-Yao Zhao, Shan-Shan Zhao

    ASTROPHYSICAL JOURNAL LETTERS   930 ( 2 )   2022.5

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    We present the first event-horizon-scale images and spatiotemporal analysis of Sgr A* taken with the Event Horizon Telescope in 2017 April at a wavelength of 1.3 mm. Imaging of Sgr A* has been conducted through surveys over a wide range of imaging assumptions using the classical CLEAN algorithm, regularized maximum likelihood methods, and a Bayesian posterior sampling method. Different prescriptions have been used to account for scattering effects by the interstellar medium toward the Galactic center. Mitigation of the rapid intraday variability that characterizes Sgr A* has been carried out through the addition of a "variability noise budget" in the observed visibilities, facilitating the reconstruction of static full-track images. Our static reconstructions of Sgr A* can be clustered into four representative morphologies that correspond to ring images with three different azimuthal brightness distributions and a small cluster that contains diverse nonring morphologies. Based on our extensive analysis of the effects of sparse (u, v)-coverage, source variability, and interstellar scattering, as well as studies of simulated visibility data, we conclude that the Event Horizon Telescope Sgr A* data show compelling evidence for an image that is dominated by a bright ring of emission with a ring diameter of similar to 50 mu as, consistent with the expected "shadow" of a 4 x 10(6) M (circle dot) black hole in the Galactic center located at a distance of 8 kpc.

    DOI: 10.3847/2041-8213/ac6429

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  • First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration

    Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, David Ball, Mislav Balokovic, John Barrett, Michi Baubock, Bradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Katherine L. Bouman, Geoffrey C. Bower, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Avery E. Broderick, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamante, Do-Young Byun, John E. Carlstrom, Chiara Ceccobello, Andrew Chael, Chi-kwan Chan, Koushik Chatterjee, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Xiaopeng Cheng, Ilje Cho, Pierre Christian, Nicholas S. Conroy, 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, Jason Dexter, Vedant Dhruv, Sheperd S. Doeleman, Sean Dougal, Sergio A. Dzib, Ralph P. Eatough, Razieh Emami, Heino Falcke, Joseph Farah, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Raquel Fraga-Encinas, William T. Freeman, Per Friberg, Christian M. Fromm, Antonio Fuentes, Peter Galison, Charles F. Gammie, Roberto Garcia, Olivier Gentaz, Boris Georgiev, Ciriaco Goddi, Roman Gold, Arturo Gomez-Ruiz, Jose L. Gomez, Minfeng Gu, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Kari Haworth, Michael H. Hecht, Ronald Hesper, Dirk Heumann, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Shiro Ikeda, C. M. Violette Impellizzeri, Makoto Inoue, Sara Issaoun, David J. James, Buell T. Jannuzi, Michael Janssen, Britton Jeter, Wu Jiang, Alejandra Jimenez-Rosales, Michael D. Johnson, Svetlana Jorstad, Abhishek Joshi, 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, Prashant Kocherlakota, Yutaro Kofuji, Patrick M. Koch, Shoko Koyama, Carsten Kramer, Michael Kramer, Thomas P. Krichbaum, Cheng-Yu Kuo, Noemi La Bella, Tod R. Lauer, Daeyoung Lee, Sang-Sung Lee, Po Kin Leung, Aviad Levis, Zhiyuan Li, Rocco Lico, Greg Lindahl, Michael Lindqvist, Mikhail Lisakov, Jun Liu, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin J. Lonsdale, Ru-Sen Lu, Jirong Mao, Nicola Marchili, Sera Markoff, Daniel P. Marrone, Alan P. Marscher, Ivan Marti-Vidal, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Daniel Michalik, Izumi Mizuno, Yosuke Mizuno, James M. Moran, Kotaro Moriyama, Monika Moscibrodzka, Cornelia Muller, Alejandro Mus, Gibwa Musoke, Ioannis Myserlis, Andrew Nadolski, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Antonios Nathanail, Santiago Navarro Fuentes, Joey Neilsen, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Michael A. Nowak, Junghwan Oh, Hiroki Okino, Hector Olivares, Gisela N. Ortiz-Leon, Tomoaki Oyama, Daniel C. M. Palumbo, Georgios Filippos Paraschos, Jongho Park, Harriet Parsons, Nimesh Patel, Ue-Li Pen, Dominic W. Pesce, Vincent Pietu, Richard Plambeck, Aleksandar PopStefanija, Oliver Porth, Felix M. Potzl, Ben Prather, Jorge A. Preciado-Lopez, Hung-Yi Pu, Venkatessh Ramakrishnan, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, Luciano Rezzolla, Angelo Ricarte, Bart Ripperda, Freek Roelofs, Alan Rogers, Eduardo Ros, Cristina Romero-Canizales, Arash Roshanineshat, Helge Rottmann, Alan L. Roy, Ignacio Ruiz, Chet Ruszczyk, Kazi L. J. Rygl, Salvador Sanchez, David Sanchez-Arguelles, Miguel Sanchez-Portal, Mahito Sasada, Kaushik Satapathy, Tuomas Savolainen, F. Peter Schloerb, Jonathan Schonfeld, Karl-Friedrich Schuster, Lijing Shao, Zhiqiang Shen, Des Small, Bong Won Sohn, Jason SooHoo, Kamal Souccar, He Sun, Fumie Tazaki, Alexandra J. Tetarenko, Paul Tiede, Remo P. J. Tilanus, Michael Titus, Pablo Torne, Efthalia Traianou, Tyler Trent, Sascha Trippe, Matthew Turk, Ilse van Bemmel, Huib Jan van Langevelde, Daniel R. van Rossum, Jesse Vos, Jan Wagner, Derek Ward-Thompson, John Wardle, Jonathan Weintroub, Norbert Wex, Robert Wharton, Maciek Wielgus, Kaj Wiik, Gunther Witzel, Michael F. Wondrak, George N. Wong, Qingwen Wu, Paul Yamaguchi, Doosoo Yoon, Andre Young, Ken Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Shuo Zhang, Guang-Yao Zhao, Shan-Shan Zhao, Claudio Agurto, Juan Pablo Araneda, Oriel Arriagada, Alessandra Bertarini, Ryan Berthold, Jay Blanchard, Ken Brown, Mauricio Cardenas, Michael Cantzler, Patricio Caro, Tim C. Chuter, Miroslaw Ciechanowicz, Iain M. Coulson, Joseph Crowley, Nathalie Degenaar, Sven Dornbusch, Carlos A. Duran, Karl Forster, Gertie Geertsema, Edouard Gonzalez, Dave Graham, Frederic Gueth, Chih-Chiang Han, Cristian Herrera, Ruben Herrero-Illana, Stefan Heyminck, James Hoge, Yau-De Huang, Homin Jiang, David John, Thomas Klein, Derek Kubo, John Kuroda, Caleb Kwon, Robert Laing, Ching-Tang Liu, Kuan-Yu Liu, Felipe Mac-Auliffe, Pierre Martin-Cocher, Callie Matulonis, Hugo Messias, Zheng Meyer-Zhao, Francisco Montenegro-Montes, William Montgomerie, Dirk Muders, Hiroaki Nishioka, Timothy J. Norton, Rodrigo Olivares, Juan Pablo Perez-Beaupuits, Rodrigo Parra, Michael Poirier, Nicolas Pradel, Philippe A. Raffin, Jorge Ramirez, Mark Reynolds, Alejandro F. Saez-Madain, Jorge Santana, Kevin M. Silva, Don Sousa, William Stahm, Karl Torstensson, Paulina Venegas, Craig Walther, Gundolf Wieching, Rudy Wijnands, Jan G. A. Wouterloot

    ASTROPHYSICAL JOURNAL LETTERS   930 ( 2 )   2022.5

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    We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5-11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of similar to 50 mu as, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*'s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior.

    DOI: 10.3847/2041-8213/ac6675

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  • First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way

    Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, David Ball, Mislav Balokovic, John Barrett, Michi Baubock, Bradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Katherine L. Bouman, Geoffrey C. Bower, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Avery E. Broderick, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamante, Do-Young Byun, John E. Carlstrom, Chiara Ceccobello, Andrew Chael, Chi-kwan Chan, Koushik Chatterjee, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Xiaopeng Cheng, Ilje Cho, Pierre Christian, Nicholas S. Conroy, 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, Jason Dexter, Vedant Dhruv, Sheperd S. Doeleman, Sean Dougal, Sergio A. Dzib, Ralph P. Eatough, Razieh Emami, Heino Falcke, Joseph Farah, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Raquel Fraga-Encinas, William T. Freeman, Per Friberg, Christian M. Fromm, Antonio Fuentes, Peter Galison, Charles F. Gammie, Roberto Garcia, Olivier Gentaz, Boris Georgiev, Ciriaco Goddi, Roman Gold, Arturo Gomez-Ruiz, Jose L. Gomez, Minfeng Gu, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Kari Haworth, Michael H. Hecht, Ronald Hesper, Dirk Heumann, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Shiro Ikeda, C. M. Violette Impellizzeri, Makoto Inoue, Sara Issaoun, David J. James, Buell T. Jannuzi, Michael Janssen, Britton Jeter, Wu Jiang, Alejandra Jimenez-Rosales, Michael D. Johnson, Svetlana Jorstad, Abhishek Joshi, 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, Prashant Kocherlakota, Yutaro Kofuji, Patrick M. Koch, Shoko Koyama, Carsten Kramer, Michael Kramer, Thomas P. Krichbaum, Cheng-Yu Kuo, Noemi La Bella, Tod R. Lauer, Daeyoung Lee, Sang-Sung Lee, Po Kin Leung, Aviad Levis, Zhiyuan Li, Rocco Lico, Greg Lindahl, Michael Lindqvist, Mikhail Lisakov, Jun Liu, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin J. Lonsdale, Ru-Sen Lu, Jirong Mao, Nicola Marchili, Sera Markoff, Daniel P. Marrone, Alan P. Marscher, Ivan Marti-Vidal, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Daniel Michalik, Izumi Mizuno, Yosuke Mizuno, James M. Moran, Kotaro Moriyama, Monika Moscibrodzka, Cornelia Muller, Alejandro Mus, Gibwa Musoke, Ioannis Myserlis, Andrew Nadolski, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Antonios Nathanail, Santiago Navarro Fuentes, Joey Neilsen, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Michael A. Nowak, Junghwan Oh, Hiroki Okino, Hector Olivares, Gisela N. Ortiz-Leon, Tomoaki Oyama, Daniel C. M. Palumbo, Georgios Filippos Paraschos, Jongho Park, Harriet Parsons, Nimesh Patel, Ue-Li Pen, Dominic W. Pesce, Vincent Pietu, Richard Plambeck, Aleksandar PopStefanija, Oliver Porth, Felix M. Potzl, Ben Prather, Jorge A. Preciado-Lopez, Hung-Yi Pu, Venkatessh Ramakrishnan, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, Luciano Rezzolla, Angelo Ricarte, Bart Ripperda, Freek Roelofs, Alan Rogers, Eduardo Ros, Cristina Romero-Canizales, Arash Roshanineshat, Helge Rottmann, Alan L. Roy, Ignacio Ruiz, Chet Ruszczyk, Kazi L. J. Rygl, Salvador Sanchez, David Sanchez-Arguelles, Miguel Sanchez-Portal, Mahito Sasada, Kaushik Satapathy, Tuomas Savolainen, F. Peter Schloerb, Jonathan Schonfeld, Karl-Friedrich Schuster, Lijing Shao, Zhiqiang Shen, Des Small, Bong Won Sohn, Jason SooHoo, Kamal Souccar, He Sun, Fumie Tazaki, Alexandra J. Tetarenko, Paul Tiede, Remo P. J. Tilanus, Michael Titus, Pablo Torne, Efthalia Traianou, Tyler Trent, Sascha Trippe, Matthew Turk, Ilse van Bemmel, Huib Jan van Langevelde, Daniel R. van Rossum, Jesse Vos, Jan Wagner, Derek Ward-Thompson, John Wardle, Jonathan Weintroub, Norbert Wex, Robert Wharton, Maciek Wielgus, Kaj Wiik, Gunther Witzel, Michael F. Wondrak, George N. Wong, Qingwen Wu, Paul Yamaguchi, Doosoo Yoon, Andre Young, Ken Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Shuo Zhang, Guang-Yao Zhao, Shan-Shan Zhao, Feryal Ozel, Claudio Agurto, Alexander Allardi, Rodrigo Amestica, Juan Pablo Araneda, Oriel Arriagada, Jennie L. Berghuis, Alessandra Bertarini, Ryan Berthold, Jay Blanchard, Ken Brown, Mauricio Cardenas, Michael Cantzler, Patricio Caro, Edgar Castillo-Dominguez, Tin Lok Chan, Chih-Cheng Chang, Dominic O. Chang, Shu-Hao Chang, Song-Chu Chang, Chung-Chen Chen, Ryan Chilson, Tim C. Chuter, Miroslaw Ciechanowicz, Edgar Colin-Beltran, Iain M. Coulson, Joseph Crowley, Nathalie Degenaar, Sven Dornbusch, Carlos A. Duran, Wendeline B. Everett, Aaron Faber, Karl Forster, Miriam M. Fuchs, David M. Gale, Gertie Geertsema, Edouard Gonzalez, Dave Graham, Frederic Gueth, Nils W. Halverson, Chih-Chiang Han, Kuo-Chang Han, Yutaka Hasegawa, Jose Luis Hernandez-Rebollar, Cristian Herrera, Ruben Herrero-Illana, Stefan Heyminck, Akihiko Hirota, James Hoge, Shelbi R. Hostler Schimpf, Ryan E. Howie, Yau-De Huang, Homin Jiang, Hao Jinchi, David John, Kimihiro Kimura, Thomas Klein, Derek Kubo, John Kuroda, Caleb Kwon, Richard Lacasse, Robert Laing, Erik M. Leitch, Chao-Te Li, Ching-Tang Liu, Kuan-Yu Liu, Lupin C-C Lin, Li-Ming Lu, Felipe Mac-Auliffe, Pierre Martin-Cocher, Callie Matulonis, John K. Maute, Hugo Messias, Zheng Meyer-Zhao, Alfredo Montana, Francisco Montenegro-Montes, William Montgomerie, Marcos Emir Moreno Nolasco, Dirk Muders, Hiroaki Nishioka, Timothy J. Norton, George Nystrom, Hideo Ogawa, Rodrigo Olivares, Peter Oshiro, Juan Pablo Perez-Beaupuits, Rodrigo Parra, Neil M. Phillips, Michael Poirier, Nicolas Pradel, Richard Qiu, Philippe A. Raffin, Alexandra S. Rahlin, Jorge Ramirez, Sean Ressler, Mark Reynolds, Ivan Rodriguez-Montoya, Alejandro F. Saez-Madain, Jorge Santana, Paul Shaw, Leslie E. Shirkey, Kevin M. Silva, William Snow, Don Sousa, T. K. Sridharan, William Stahm, Anthony A. Stark, John Test, Karl Torstensson, Paulina Venegas, Craig Walther, Ta-Shun Wei, Chris White, Gundolf Wieching, Rudy Wijnands, Jan G. A. Wouterloot, Chen-Yu Yu, Wei Yu, Milagros Zeballos

    ASTROPHYSICAL JOURNAL LETTERS   930 ( 2 )   2022.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing Ltd  

    We present the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength of lambda = 1.3 mm. The EHT data resolve a compact emission region with intrahour variability. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of 51.8 +/- 2.3 mu as (68% credible interval). The ring has modest azimuthal brightness asymmetry and a comparatively dim interior. Using a large suite of numerical simulations, we demonstrate that the EHT images of Sgr A* are consistent with the expected appearance of a Kerr black hole with mass similar to 4 x 10(6) M (circle dot), which is inferred to exist at this location based on previous infrared observations of individual stellar orbits, as well as maser proper-motion studies. Our model comparisons disfavor scenarios where the black hole is viewed at high inclination (i > 50 degrees), as well as nonspinning black holes and those with retrograde accretion disks. Our results provide direct evidence for the presence of a supermassive black hole at the center of the Milky Way, and for the first time we connect the predictions from dynamical measurements of stellar orbits on scales of 10(3)-10(5) gravitational radii to event-horizon-scale images and variability. Furthermore, a comparison with the EHT results for the supermassive black hole M87* shows consistency with the predictions of general relativity spanning over three orders of magnitude in central mass.

    DOI: 10.3847/2041-8213/ac6674

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  • First Sagittarius A* Event Horizon Telescope Results. VI. Testing the Black Hole Metric

    Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, David Ball, Mislav Balokovic, John Barrett, Michi Baubock, Bradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Katherine L. Bouman, Geoffrey C. Bower, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Avery E. Broderick, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamante, Do-Young Byun, John E. Carlstrom, Chiara Ceccobello, Andrew Chael, Chi-kwan Chan, Koushik Chatterjee, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Xiaopeng Cheng, Ilje Cho, Pierre Christian, Nicholas S. Conroy, 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, Jason Dexter, Vedant Dhruv, Sheperd S. Doeleman, Sean Dougal, Sergio A. Dzib, Ralph P. Eatough, Razieh Emami, Heino Falcke, Joseph Farah, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Raquel Fraga-Encinas, William T. Freeman, Per Friberg, Christian M. Fromm, Antonio Fuentes, Peter Galison, Charles F. Gammie, Roberto Garcia, Olivier Gentaz, Boris Georgiev, Ciriaco Goddi, Roman Gold, Arturo Gomez-Ruiz, Jose L. Gomez, Minfeng Gu, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Kari Haworth, Michael H. Hecht, Ronald Hesper, Dirk Heumann, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Shiro Ikeda, C. M. Violette Impellizzeri, Makoto Inoue, Sara Issaoun, David J. James, Buell T. Jannuzi, Michael Janssen, Britton Jeter, Wu Jiang, Alejandra Jimenez-Rosales, Michael D. Johnson, Svetlana Jorstad, Abhishek Joshi, 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, Prashant Kocherlakota, Yutaro Kofuji, Patrick M. Koch, Shoko Koyama, Carsten Kramer, Michael Kramer, Thomas P. Krichbaum, Cheng-Yu Kuo, Noemi La Bella, Tod R. Lauer, Daeyoung Lee, Sang-Sung Lee, Po Kin Leung, Aviad Levis, Zhiyuan Li, Rocco Lico, Greg Lindahl, Michael Lindqvist, Mikhail Lisakov, Jun Liu, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin J. Lonsdale, Ru-Sen Lu, Jirong Mao, Nicola Marchili, Sera Markoff, Daniel P. Marrone, Alan P. Marscher, Ivan Marti-Vidal, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Daniel Michalik, Izumi Mizuno, Yosuke Mizuno, James M. Moran, Kotaro Moriyama, Monika Moscibrodzka, Cornelia Muller, Alejandro Mus, Gibwa Musoke, Ioannis Myserlis, Andrew Nadolski, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Antonios Nathanail, Santiago Navarro Fuentes, Joey Neilsen, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Michael A. Nowak, Junghwan Oh, Hiroki Okino, Hector Olivares, Gisela N. Ortiz-Leon, Tomoaki Oyama, Feryal Ozel, Daniel C. M. Palumbo, Georgios Filippos Paraschos, Jongho Park, Harriet Parsons, Nimesh Patel, Ue-Li Pen, Dominic W. Pesce, Vincent Pietu, Richard Plambeck, Aleksandar PopStefanija, Oliver Porth, Felix M. Potzl, Ben Prather, Jorge A. Preciado-Lopez, Dimitrios Psaltis, Hung-Yi Pu, Venkatessh Ramakrishnan, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, Luciano Rezzolla, Angelo Ricarte, Bart Ripperda, Freek Roelofs, Alan Rogers, Eduardo Ros, Cristina Romero-Canizales, Arash Roshanineshat, Helge Rottmann, Alan L. Roy, Ignacio Ruiz, Chet Ruszczyk, Kazi L. J. Rygl, Salvador Sanchez, David Sanchez-Arguelles, Miguel Sanchez-Portal, Mahito Sasada, Kaushik Satapathy, Tuomas Savolainen, F. Peter Schloerb, Jonathan Schonfeld, Karl-Friedrich Schuster, Lijing Shao, Zhiqiang Shen, Des Small, Bong Won Sohn, Jason SooHoo, Kamal Souccar, He Sun, Fumie Tazaki, Alexandra J. Tetarenko, Paul Tiede, Remo P. J. Tilanus, Michael Titus, Pablo Torne, Efthalia Traianou, Tyler Trent, Sascha Trippe, Matthew Turk, Ilse van Bemmel, Huib Jan van Langevelde, Daniel R. van Rossum, Jesse Vos, Jan Wagner, Derek Ward-Thompson, John Wardle, Jonathan Weintroub, Norbert Wex, Robert Wharton, Maciek Wielgus, Kaj Wiik, Gunther Witzel, Michael F. Wondrak, George N. Wong, Qingwen Wu, Paul Yamaguchi, Doosoo Yoon, Andre Young, Ken Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Shuo Zhang, Guang-Yao Zhao, Shan-Shan Zhao

    ASTROPHYSICAL JOURNAL LETTERS   930 ( 2 )   2022.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing Ltd  

    Astrophysical black holes are expected to be described by the Kerr metric. This is the only stationary, vacuum, axisymmetric metric, without electromagnetic charge, that satisfies Einstein's equations and does not have pathologies outside of the event horizon. We present new constraints on potential deviations from the Kerr prediction based on 2017 EHT observations of Sagittarius A* (Sgr A*). We calibrate the relationship between the geometrically defined black hole shadow and the observed size of the ring-like images using a library that includes both Kerr and non-Kerr simulations. We use the exquisite prior constraints on the mass-to-distance ratio for Sgr A* to show that the observed image size is within similar to 10% of the Kerr predictions. We use these bounds to constrain metrics that are parametrically different from Kerr, as well as the charges of several known spacetimes. To consider alternatives to the presence of an event horizon, we explore the possibility that Sgr A* is a compact object with a surface that either absorbs and thermally reemits incident radiation or partially reflects it. Using the observed image size and the broadband spectrum of Sgr A*, we conclude that a thermal surface can be ruled out and a fully reflective one is unlikely. We compare our results to the broader landscape of gravitational tests. Together with the bounds found for stellar-mass black holes and the M87 black hole, our observations provide further support that the external spacetimes of all black holes are described by the Kerr metric, independent of their mass.

    DOI: 10.3847/2041-8213/ac6756

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  • A Universal Power-law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows

    Boris Georgiev, Dominic W. Pesce, Avery E. Broderick, George N. Wong, Vedant Dhruv, Maciek Wielgus, Charles F. Gammie, Chi-kwan Chan, Koushik Chatterjee, Razieh Emami, Yosuke Mizuno, Roman Gold, Christian M. Fromm, Angelo Ricarte, Doosoo Yoon, Abhishek Joshi, Ben Prather, Alejandro Cruz-Osorio, Michael D. Johnson, Oliver Porth, Hector Olivares, Ziri Younsi, Luciano Rezzolla, Jesse Vos, Richard Qiu, Antonios Nathanail, Ramesh Narayan, Andrew Chael, Richard Anantua, Monika Moscibrodzka, Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Keiichi Asada, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, David Ball, Mislav Balokovic, John Barrett, Michi Baubock, Bradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Katherine L. Bouman, Geoffrey C. Bower, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamante, Do-Young Byun, John E. Carlstrom, Chiara Ceccobello, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Xiaopeng Cheng, Ilje Cho, Pierre Christian, Nicholas S. Conroy, John E. Conway, James M. Cordes, Thomas M. Crawford, Geoffrey B. Crew, Yuzhu Cui, Jordy Davelaar, Mariafelicia De Laurentis, Roger Deane, Jessica Dempsey, Gregory Desvignes, Jason Dexter, Sheperd S. Doeleman, Sean Dougal, Sergio A. Dzib, Ralph P. Eatough, Heino Falcke, Joseph Farah, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Raquel Fraga-Encinas, William T. Freeman, Per Friberg, Antonio Fuentes, Peter Galison, Roberto Garcia, Olivier Gentaz, Ciriaco Goddi, Arturo Gomez-Ruiz, Jose L. Gomez, Minfeng Gu, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Kari Haworth, Michael H. Hecht, Ronald Hesper, Dirk Heumann, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Shiro Ikeda, C. M. Violette Impellizzeri, 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, Prashant Kocherlakota, Yutaro Kofuji, Patrick M. Koch, Shoko Koyama, Carsten Kramer, Michael Kramer, Thomas P. Krichbaum, Cheng-Yu Kuo, Noemi La Bella, Tod R. Lauer, Daeyoung Lee, Sang-Sung Lee, Luis Lehner, Po Kin Leung, Aviad Levis, Zhiyuan Li, Rocco Lico, Greg Lindahl, Michael Lindqvist, Mikhail Lisakov, Jun Liu, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin J. Lonsdale, Ru-Sen Lu, Jirong Mao, Nicola Marchili, Sera Markoff, Daniel P. Marrone, Alan P. Marscher, Ivan Marti-Vidal, Satoki Matsushita, Lynn D. Matthews, Karl M. Menten, Daniel Michalik, Izumi Mizuno, James M. Moran, Kotaro Moriyama, Cornelia Muller, Alejandro Mus, Gibwa Musoke, Ioannis Myserlis, Andrew Nadolski, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Gopal Narayanan, Iniyan Natarajan, Santiago Navarro Fuentes, Joey Neilsen, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Michael A. Nowak, Junghwan Oh, Hiroki Okino, Gisela N. Ortiz-Leon, Tomoaki Oyama, Daniel C. M. Palumbo, Georgios Filippos Paraschos, Jongho Park, Harriet Parsons, Nimesh Patel, Ue-Li Pen, Vincent Pietu, Richard Plambeck, Aleksandar PopStefanija, Felix M. Potzl, Jorge A. Preciado-Lopez, Hung-Yi Pu, Venkatessh Ramakrishnan, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, Bart Ripperda, Freek Roelofs, Alan Rogers, Eduardo Ros, Cristina Romero-Canizales, Arash Roshanineshat, Helge Rottmann, Alan L. Roy, Ignacio Ruiz, Chet Ruszczyk, Kazi L. J. Rygl, Salvador Sanchez, David Sanchez-Arguelles, Miguel Sanchez-Portal, Mahito Sasada, Kaushik Satapathy, Tuomas Savolainen, F. Peter Schloerb, Jonathan Schonfeld, Karl-Friedrich Schuster, Lijing Shao, Zhiqiang Shen, Des Small, Bong Won Sohn, Jason SooHoo, Kamal Souccar, He Sun, Fumie Tazaki, Alexandra J. Tetarenko, Paul Tiede, Remo P. J. Tilanus, Michael Titus, Pablo Torne, Efthalia Traianou, Tyler Trent, Sascha Trippe, Matthew Turk, Ilse van Bemmel, Huib Jan van Langevelde, Daniel R. van Rossum, Jan Wagner, Derek Ward-Thompson, John Wardle, Jonathan Weintroub, Norbert Wex, Robert Wharton, Kaj Wiik, Gunther Witzel, Michael F. Wondrak, Qingwen Wu, Paul Yamaguchi, Andre Young, Ken Young, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Shuo Zhang, Guang-Yao Zhao, Shan-Shan Zhao

    ASTROPHYSICAL JOURNAL LETTERS   930 ( 2 )   2022.5

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    We present a framework for characterizing the spatiotemporal power spectrum of the variability expected from the horizon-scale emission structure around supermassive black holes, and we apply this framework to a library of general relativistic magnetohydrodynamic (GRMHD) simulations and associated general relativistic ray-traced images relevant for Event Horizon Telescope (EHT) observations of Sgr A*. We find that the variability power spectrum is generically a red-noise process in both the temporal and spatial dimensions, with the peak in power occurring on the longest timescales and largest spatial scales. When both the time-averaged source structure and the spatially integrated light-curve variability are removed, the residual power spectrum exhibits a universal broken power-law behavior. On small spatial frequencies, the residual power spectrum rises as the square of the spatial frequency and is proportional to the variance in the centroid of emission. Beyond some peak in variability power, the residual power spectrum falls as that of the time-averaged source structure, which is similar across simulations; this behavior can be naturally explained if the variability arises from a multiplicative random field that has a steeper high-frequency power-law index than that of the time-averaged source structure. We briefly explore the ability of power spectral variability studies to constrain physical parameters relevant for the GRMHD simulations, which can be scaled to provide predictions for black holes in a range of systems in the optically thin regime. We present specific expectations for the behavior of the M87* and Sgr A* accretion flows as observed by the EHT.

    DOI: 10.3847/2041-8213/ac65eb

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  • Herschel discovery of far-infrared emission from the hotspot D in the radio galaxy Cygnus A

    Yuji Sunada, Naoki Isobe, Makoto S. Tashiro, Motoki Kino, Shoko Koyama, Satomi Nakahara

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   512 ( 4 )   5995 - 6006   2022.4

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    The far-infrared counterpart of hotspot D, the terminal hotspot of the eastern jet hosted by the radio galaxy Cygnus A, is detected with Herschel Aperture photometry of the source performed in 5 photometric bands covering the wavelength range of 70-350 mu m. After removing the contamination from another nearby hotspot, E, the far-infrared intensity of hotspot D is derived as 83 +/- 13 and 269 +/- 66 mJy at 160 and 350 mu m, respectively. Since the far-infrared spectrum of the object smoothly connects to the radio one, the far-infrared emission is attributed to the synchrotron radiation from the radio-emitting electron population. The radio-to-near-infrared spectrum is confirmed to exhibit a far-infrared break feature at the frequency of nu(br) = 2.0(-0.8)(+1.2) x 10(12) Hz. The change in energy index at the break (Delta alpha = 0.5) is interpreted as the impact of radiative cooling on an electron distribution sustained by continuous injection from diffusive shock acceleration. By ascribing the derived break to this cooling break, the magnetic field, B, in the hotspot is determined as a function of its radius, R within a uniform one-zone model combined with the strong relativistic shock condition. An independent B-R constraint is obtained by assuming the X-ray spectrum is wholly due to synchrotron self-Compton emission. By combining these conditions, the two parameters are tightly determined as B = 120-150 mu G and R = 1.3-1.6 kpc. A further investigation into the two conditions indicates the observed X-ray flux is highly dominated by the synchrotron self-Compton emission.

    DOI: 10.1093/mnras/stac826

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  • East Asian VLBI Network observations of active galactic nuclei jets: imaging with KaVA plus Tianma plus Nanshan

    Yu-Zhu Cui, Kazuhiro Hada, Motoki Kino, Bong-Won Sohn, Jongho Park, Hyun-Wook Ro, Satoko Sawada-Satoh, Wu Jiang, Lang Cui, Mareki Honma, Zhi-Qiang Shen, Fumie Tazaki, Tao An, Ilje Cho, Guang-Yao Zhao, Xiao-Peng Cheng, Kotaro Niinuma, Kiyoaki Wajima, Ying-Kang Zhang, Noriyuki Kawaguchi, Juan-Carlos Algaba, Shoko Koyama, Tomoya Hirota, Yoshinori Yonekura, Nobuyuki Sakai, Bo Xia, Yong-Bin Jiang, Lin-Feng Yu, Wei Gou, Ju-Yeon Hwang, Yong-Chen Jiang, Yun-Xia Sun, Dong-Kyu Jung, Hyo-Ryoung Kim, Jeong-Sook Kim, Hideyuki Kobayashi, Jee-Won Lee, Jeong-Ae Lee, Hua Zhang, Guang-Hui Li, Zhi-Qiang Xu, Peng Li, Jung-Hwan Oh, Se-Jin Oh, Chung-Sik Oh, Tomoaki Oyama, Duk-Gyoo Roh, Katsunori-M Shibata, Wen Guo, Rong-Bing Zhao, Wei-Ye Zhong, Jin-Qing Wang, Wen-Jun Yang, Hao Yan, Jae-Hwan Yeom, Bin Li, Xiao-Fei Li, Jian-Ping Yuan, Jian Dong, Zhong Chen, Kazunori Akiyama, Keiichi Asada, Do-Young Byun, Yoshiaki Hagiwara, Jeffrey Hodgson, Tae-Hyun Jung, Kee-Tae Kim, Sang-Sung Lee, Kunwoo Yi, Qing-Hui Liu, Xiang Liu, Ru-Sen Lu, Masanori Nakamura, Sascha Trippe, Na Wang, Xue-Zheng Wang, Bo Zhang

    RESEARCH IN ASTRONOMY AND ASTROPHYSICS   21 ( 8 )   2021.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:NATL ASTRONOMICAL OBSERVATORIES, CHIN ACAD SCIENCES  

    The East Asian Very Long Baseline Interferometry (VLBI) Network (EAVN) is a rapidly evolving international VLBI array that is currently promoted under joint efforts among China, Japan and Korea. EAVN aims at forming a joint VLBI Network by combining a large number of radio telescopes distributed over East Asian regions. After the combination of the Korean VLBI Network (KVN) and the VLBI Exploration of Radio Astrometry (VERA) into KaVA, further expansion with the joint array in East Asia is actively promoted. Here we report the first imaging results (at 22 and 43 GHz) of bright radio sources obtained with KaVA connected to Tianma 65-m and Nanshan 26-m Radio Telescopes in China. To test the EAVN imaging performance for different sources, we observed four active galactic nuclei (AGN) having different brightness and morphology. As a result, we confirmed that the Tianma 65-m Radio Telescope (TMRT) significantly enhances the overall array sensitivity, a factor of 4 improvement in baseline sensitivity and 2 in image dynamic range compared to the case of KaVA only. The addition of the Nanshan 26-m Radio Telescope (NSRT) further doubled the east-west angular resolution. With the resulting high-dynamic-range, high-resolution images with EAVN (KaVA+TMRT+NSRT), various fine-scale structures in our targets, such as the counter-jet in M87, a kink-like morphology of the 3C 273 jet and the weak emission in other sources are successfully detected. This demonstrates the powerful capability of EAVN to study AGN jets and to achieve other science goals in general. Ongoing expansion of EAVN will further enhance the angular resolution, detection sensitivity and frequency coverage of the network.

    DOI: 10.1088/1674-4527/21/8/205

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  • Event Horizon Telescope observations of the jet launching and collimation in Centaurus A

    Michael Janssen, Heino Falcke, Matthias Kadler, Eduardo Ros, Maciek Wielgus, Kazunori Akiyama, Mislav Baloković, Lindy Blackburn, Katherine L. Bouman, Andrew Chael, Chi-kwan Chan, Koushik Chatterjee, Jordy Davelaar, Philip G. Edwards, Christian M. Fromm, José L. Gómez, Ciriaco Goddi, Sara Issaoun, Michael D. Johnson, Junhan Kim, Jun Yi Koay, Thomas P. Krichbaum, Jun Liu, Elisabetta Liuzzo, Sera Markoff, Alex Markowitz, Daniel P. Marrone, Yosuke Mizuno, Cornelia Müller, Chunchong Ni, Dominic W. Pesce, Venkatessh Ramakrishnan, Freek Roelofs, Kazi L. J. Rygl, Ilse van Bemmel, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Anne-Kathrin Baczko, David Ball, John Barrett, Bradford A. Benson, Dan Bintley, Raymond Blundell, Wilfred Boland, 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, Shami 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, Mariafelicia De Laurentis, Roger Deane, Jessica Dempsey, Gregory Desvignes, Jason Dexter, Sheperd S. Doeleman, Ralph P. Eatough, Joseph Farah, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Raquel Fraga-Encinas, Per Friberg, Antonio Fuentes, Peter Galison, Charles F. Gammie, Roberto García, Zachary Gelles, Olivier Gentaz, Boris Georgiev, Roman Gold, Arturo I. Gómez-Ruiz, Minfeng Gu, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Michael H. Hecht, Ronald Hesper, Elizabeth Himwich, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Shiro Ikeda, Makoto Inoue, David J. James, Buell T. Jannuzi, 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, Motoki Kino, Yutaro Kofuji, Shoko Koyama, Michael Kramer, Carsten Kramer, Cheng-Yu Kuo, Tod R. Lauer, Sang-Sung Lee, Aviad Levis, Yan-Rong Li, Zhiyuan Li, Michael Lindqvist, Rocco Lico, Greg Lindahl, Kuo Liu, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin Lonsdale, Ru-Sen Lu, Nicholas R. MacDonald, Jirong Mao, Nicola Marchili, Alan P. Marscher, Iván Martí-Vidal, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Izumi Mizuno, James M. Moran, Kotaro Moriyama, Monika Moscibrodzka, Gibwa Musoke, Alejandro Mus Mejías, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Antonios Nathanail, Joey Neilsen, Roberto Neri, Aristeidis Noutsos, Michael A. Nowak, Hiroki Okino, Héctor Olivares, Gisela N. Ortiz-León, Tomoaki Oyama, Feryal Özel, Daniel C. M. Palumbo, Jongho Park, Nimesh Patel, Ue-Li Pen, Vincent Piétu, Richard Plambeck, Aleksandar PopStefanija, Oliver Porth, Felix M. Pötzl, Ben Prather, Jorge A. Preciado-López, Dimitrios Psaltis, Hung-Yi Pu, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, Luciano Rezzolla, Angelo Ricarte, Bart Ripperda, Alan Rogers, Mel Rose, Arash Roshanineshat, Helge Rottmann, Alan L. Roy, Chet Ruszczyk, 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, 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, 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

    Nature Astronomy   2021.7

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    <title>Abstract</title>Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (<italic>r</italic><sub>g</sub> ≡ <italic>G</italic><italic>M</italic>/<italic>c</italic><sup>2</sup>) scales in nearby sources<sup>1</sup>. Centaurus A is the closest radio-loud source to Earth<sup>2</sup>. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations<sup>3</sup>, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 <italic>r</italic><sub>g</sub> scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow<sup>4</sup> should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses<sup>5,6</sup>.

    DOI: 10.1038/s41550-021-01417-w

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  • Constraints on black-hole charges with the 2017 EHT observations of M87*

    Prashant Kocherlakota, Luciano Rezzolla, Heino Falcke, Christian M. Fromm, Michael Kramer, Yosuke Mizuno, Antonios Nathanail, Héctor Olivares, Ziri Younsi, 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, Andrew Chael, 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, Sheperd S. Doeleman, Ralph P. Eatough, Joseph Farah, Vincent L. Fish, Ed Fomalont, Raquel Fraga-Encinas, Per Friberg, H. Alyson Ford, Antonio Fuentes, Peter Galison, Charles F. Gammie, 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, Michael D. Johnson, 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, 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, James M. Moran, Kotaro Moriyama, Monika Moscibrodzka, Cornelia Müller, Gibwa Musoke, Alejandro Mus Mejías, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Joseph Neilsen, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Michael A. Nowak, Hiroki Okino, Gisela N. Ortiz-León, Tomoaki Oyama, Feryal Özel, Daniel C. M. Palumbo, 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, Angelo Ricarte, 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, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Guang-Yao Zhao, Shan-Shan Zhao

    Physical Review D   103 ( 10 )   2021.5

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevd.103.104047

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  • 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, 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

    The Astrophysical Journal   912 ( 1 )   35 - 35   2021.5

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    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.

    DOI: 10.3847/1538-4357/abf117

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  • First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon

    Kazunori Akiyama, Juan Carlos Algaba, Antxon Alberdi, Walter Alef, 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, Andrew Chael, 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, Jason Dexter, 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, Charles F. Gammie, Roberto García, Zachary Gelles, 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, Elizabeth Himwich, 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, Michael D. Johnson, 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, Daniel Michalik, Andrew Nadolski, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, 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, Daniel C. M. Palumbo, 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, Angelo Ricarte, 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

    The Astrophysical Journal Letters   910 ( 1 )   L13 - L13   2021.3

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    Event Horizon Telescope (EHT) observations at 230 GHz have now imaged polarized emission around the supermassive black hole in M87 on event-horizon scales. This polarized synchrotron radiation probes the structure of magnetic fields and the plasma properties near the black hole. Here we compare the resolved polarization structure observed by the EHT, along with simultaneous unresolved observations with the Atacama Large Millimeter/submillimeter Array, to expectations from theoretical models. The low fractional linear polarization in the resolved image suggests that the polarization is scrambled on scales smaller than the EHT beam, which we attribute to Faraday rotation internal to the emission region. We estimate the average density n(e) similar to 10(4-7) cm(-3), magnetic field strength B similar to 1-30 G, and electron temperature T-e similar to (1-12) x 10(10) K of the radiating plasma in a simple one-zone emission model. We show that the net azimuthal linear polarization pattern may result from organized, poloidal magnetic fields in the emission region. In a quantitative comparison with a large library of simulated polarimetric images from general relativistic magnetohydrodynamic (GRMHD) simulations, we identify a subset of physical models that can explain critical features of the polarimetric EHT observations while producing a relativistic jet of sufficient power. The consistent GRMHD models are all of magnetically arrested accretion disks, where near-horizon magnetic fields are dynamically important. We use the models to infer a mass accretion rate onto the black hole in M87 of (3-20) x 10(-4) M yr(-1).

    DOI: 10.3847/2041-8213/abe4de

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  • First M87 Event Horizon Telescope Results. VII. Polarization of the Ring

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

    The Astrophysical Journal Letters   910 ( 1 )   L12 - L12   2021.3

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    DOI: 10.3847/2041-8213/abe71d

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  • Polarimetric Properties of Event Horizon Telescope Targets from ALMA

    Ciriaco Goddi, Iván Martí-Vidal, Hugo Messias, Geoffrey C. Bower, Avery E. Broderick, Jason Dexter, Daniel P. Marrone, Monika Moscibrodzka, Hiroshi Nagai, Juan Carlos Algaba, Keiichi Asada, Geoffrey B. Crew, José L. Gómez, C. M. Violette Impellizzeri, Michael Janssen, Matthias Kadler, Thomas P. Krichbaum, Rocco Lico, Lynn D. Matthews, Antonios Nathanail, Angelo Ricarte, Eduardo Ros, Ziri Younsi, Kazunori Akiyama, Antxon Alberdi, Walter Alef, Richard Anantua, 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, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Dominique Broguiere, Thomas Bronzwaer, Do-Young Byun, John E. Carlstrom, Andrew Chael, 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, Alejandro Cruz-Osorio, Yuzhu Cui, Jordy Davelaar, Mariafelicia De Laurentis, Roger Deane, Jessica Dempsey, Gregory Desvignes, Sheperd S. Doeleman, Ralph P. Eatough, Heino Falcke, Joseph Farah, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Raquel Fraga-Encinas, William T. Freeman, Per Friberg, Christian M. Fromm, Antonio Fuentes, Peter Galison, Charles F. Gammie, Roberto García, Olivier Gentaz, Boris Georgiev, Roman Gold, 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, Makoto Inoue, Sara Issaoun, David J. James, Buell T. Jannuzi, Britton Jeter, Wu Jiang, Alejandra Jimenez-Rosales, Michael D. Johnson, 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, Cheng-Yu Kuo, Tod R. Lauer, Sang-Sung Lee, Aviad Levis, Yan-Rong Li, Zhiyuan Li, Michael Lindqvist, 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, Alan P. Marscher, Satoki Matsushita, Lia Medeiros, Karl M. Menten, Izumi Mizuno, Yosuke Mizuno, James M. Moran, Kotaro Moriyama, Cornelia Müller, Gibwa Musoke, Alejandro Mus Mejías, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Joey Neilsen, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Michael A. Nowak, Hiroki Okino, Héctor Olivares, Gisela N. Ortiz-León, Tomoaki Oyama, Feryal Özel, Daniel C. M. Palumbo, 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, 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, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Guang-Yao Zhao, Shan-Shan Zhao, Gabriele Bruni, A. Gopakumar, Antonio Hernández-Gómez, Ruben Herrero-Illana, Adam Ingram, S. Komossa, Y. Y. Kovalev, Dirk Muders, Manel Perucho, Florian Rösch, Mauri Valtonen

    The Astrophysical Journal Letters   910 ( 1 )   L14 - L14   2021.3

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    We present the results from a full polarization study carried out with the Atacama Large Millimeter/submillimeter Array (ALMA) during the first Very Long Baseline Interferometry (VLBI) campaign, which was conducted in 2017 April in the lambda 3 mm and lambda 1.3 mm bands, in concert with the Global mm-VLBI Array (GMVA) and the Event Horizon Telescope (EHT), respectively. We determine the polarization and Faraday properties of all VLBI targets, including Sgr A*, M87, and a dozen radio-loud active galactic nuclei (AGNs), in the two bands at several epochs in a time window of 10 days. We detect high linear polarization fractions (2%-15%) and large rotation measures (RM > 10(3.3)-10(5.5) rad m(-2)), confirming the trends of previous AGN studies at millimeter wavelengths. We find that blazars are more strongly polarized than other AGNs in the sample, while exhibiting (on average) order-of-magnitude lower RM values, consistent with the AGN viewing angle unification scheme. For Sgr A* we report a mean RM of (-4.2 0.3) x 10(5) rad m(-2) at 1.3 mm, consistent with measurements over the past decade and, for the first time, an RM of (-2.1 0.1) x 10(5) rad m(-2) at 3 mm, suggesting that about half of the Faraday rotation at 1.3 mm may occur between the 3 mm photosphere and the 1.3 mm source. We also report the first unambiguous measurement of RM toward the M87 nucleus at millimeter wavelengths, which undergoes significant changes in magnitude and sign reversals on a one year timescale, spanning the range from -1.2 to 0.3 x 10(5) rad m(-2) at 3 mm and -4.1 to 1.5 x 10(5) rad m(-2) at 1.3 mm. Given this time variability, we argue that, unlike the case of Sgr A*, the RM in M87 does not provide an accurate estimate of the mass accretion rate onto the black hole. We put forward a two-component model, comprised of a variable compact region and a static extended region, that can simultaneously explain the polarimetric properties observed by both the EHT (on horizon scales) and ALMA (which observes the combined emission from both components). These measurements provide critical constraints for the calibration, analysis, and interpretation of simultaneously obtained VLBI data with the EHT and GMVA.

    DOI: 10.3847/2041-8213/abee6a

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  • Monitoring the Morphology of M87* in 2009–2017 with the Event Horizon Telescope Reviewed

    Maciek Wielgus, Kazunori Akiyama, Lindy Blackburn, Chi-kwan Chan, Jason Dexter, Sheperd S. Doeleman, Vincent L. Fish, Sara Issaoun, Michael D. Johnson, Thomas P. Krichbaum, Ru-Sen Lu, Dominic W. Pesce, George N. Wong, Geoffrey C. Bower, Avery E. Broderick, Andrew Chael, Koushik Chatterjee, Charles F. Gammie, Boris Georgiev, Kazuhiro Hada, Laurent Loinard, Sera Markoff, Daniel P. Marrone, Richard Plambeck, Jonathan Weintroub, Matthew Dexter, David H. E. MacMahon, Melvyn Wright, Antxon Alberdi, Walter Alef, Keiichi Asada, Rebecca Azulay, Anne-Kathrin Baczko, David Ball, Mislav Baloković, Enrico Barausse, John Barrett, Dan Bintley, Wilfred Boland, Katherine L. Bouman, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Dominique Broguiere, Thomas Bronzwaer, Do-Young Byun, John E. Carlstrom, Shami 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, Sergio A. Dzib, Ralph P. Eatough, Heino Falcke, Ed Fomalont, Raquel Fraga-Encinas, Per Friberg, Christian M. Fromm, Peter Galison, Roberto García, Olivier Gentaz, Ciriaco Goddi, Roman Gold, José L. Gómez, Arturo I. Gómez-Ruiz, Minfeng Gu, Mark Gurwell, Michael H. Hecht, Ronald Hesper, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Makoto Inoue, 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, Jae-Young Kim, Junhan Kim, Jongsoo Kim, Motoki Kino, Jun Yi Koay, Patrick M. Koch, Shoko Koyama, Michael Kramer, Carsten Kramer, Cheng-Yu Kuo, Tod R. Lauer, Sang-Sung Lee, Yan-Rong Li, Zhiyuan Li, Michael Lindqvist, Rocco Lico, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Colin Lonsdale, Nicholas R. MacDonald, Jirong Mao, Nicola Marchili, 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, Gibwa Musoke, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Antonios Nathanail, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Hiroki Okino, Héctor Olivares, Gisela N. Ortiz-León, Tomoaki Oyama, Feryal Özel, Daniel C. M. Palumbo, Jongho Park, Nimesh Patel, Ue-Li Pen, Vincent Piétu, 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, Efthalia Traianou, Sascha Trippe, Shuichiro Tsuda, Ilse van Bemmel, Huib Jan van Langevelde, Daniel R. van Rossum, Jan Wagner, John Wardle, Derek Ward-Thompson, Norbert Wex, Robert Wharton, Qingwen Wu, Doosoo Yoon, André Young, Ken Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Guangyao Zhao, Shan-Shan Zhao, Ziyan Zhu

    The Astrophysical Journal   901 ( 1 )   67 - 67   2020.9

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    DOI: 10.3847/1538-4357/abac0d

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  • Herschel SPIRE Discovery of Far-infrared Excess Synchrotron Emission from the West Hot Spot of the Radio Galaxy Pictor A Reviewed

    Naoki Isobe, Yuji Sunada, Motoki Kino, Shoko Koyama, Makoto Tashiro, Hiroshi Nagai, Chris Pearson

    The Astrophysical Journal   899 ( 1 )   17 - 17   2020.8

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    DOI: 10.3847/1538-4357/ab9d1c

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  • Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution Reviewed

    Jae-Young Kim, Thomas P. Krichbaum, Avery E. Broderick, Maciek Wielgus, Lindy Blackburn, José L. Gómez, Michael D. Johnson, Katherine L. Bouman, Andrew Chael, Kazunori Akiyama, Svetlana Jorstad, Alan P. Marscher, Sara Issaoun, Michael Janssen, Chi-kwan Chan, Tuomas Savolainen, Dominic W. Pesce, Feryal Özel, Antxon Alberdi, Walter Alef, Keiichi Asada, Rebecca Azulay, Anne-Kathrin Baczko, David Ball, Mislav Baloković, John Barrett, Dan Bintley, Wilfred Boland, Geoffrey C. Bower, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Dominique Broguiere, Thomas Bronzwaer, Do-Young Byun, John E. Carlstrom, 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, Per Friberg, Christian M. Fromm, Peter Galison, Charles F. Gammie, Roberto García, Olivier Gentaz, Boris Georgiev, Ciriaco Goddi, Roman Gold, Arturo I. Gómez-Ruiz, 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, David J. James, Buell T. Jannuzi, Britton Jeter, Wu Jiang, Alejandra Jimenez-Rosales, Taehyun Jung, Mansour Karami, Ramesh Karuppusamy, Tomohisa Kawashima, Garrett K. Keating, Mark Kettenis, Junhan Kim, Jongsoo Kim, Motoki Kino, Jun Yi Koay, Patrick M. Koch, Shoko Koyama, Michael Kramer, Carsten Kramer, Cheng-Yu Kuo, Tod R. Lauer, Sang-Sung Lee, Yan-Rong Li, Zhiyuan Li, Michael Lindqvist, Rocco Lico, 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, Iván Martí-Vidal, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Yosuke Mizuno, Izumi Mizuno, James M. Moran, Kotaro Moriyama, Monika Moscibrodzka, Gibwa Musoke, 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, Gisela N. Ortiz-León, Tomoaki Oyama, Daniel C. M. Palumbo, Jongho Park, Nimesh Patel, Ue-Li Pen, 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, 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, Efthalia Traianou, Sascha Trippe, Shuichiro Tsuda, Ilse van Bemmel, Huib Jan van Langevelde, Daniel R. van Rossum, Jan Wagner, John Wardle, Derek Ward-Thompson, Jonathan Weintroub, Norbert Wex, Robert Wharton, George N. Wong, Qingwen Wu, Doosoo Yoon, André Young, Ken Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Guangyao Zhao, Shan-Shan Zhao, Ziyan Zhu, Juan-Carlos Algaba, Alexander Allardi, Rodrigo Amestica, Jadyn Anczarski, Uwe Bach, Frederick K. Baganoff, Christopher Beaudoin, Bradford A. Benson, Ryan Berthold, Jay M. Blanchard, Ray Blundell, Sandra Bustamente, Roger Cappallo, Edgar Castillo-Domínguez, Chih-Cheng Chang, Shu-Hao Chang, Song-Chu Chang, Chung-Chen Chen, Ryan Chilson, Tim C. Chuter, Rodrigo Córdova Rosado, Iain M. Coulson, Joseph Crowley, Mark Derome, Matthew Dexter, Sven Dornbusch, Kevin A. Dudevoir, Sergio A. Dzib, Andreas Eckart, Chris Eckert, Neal R. Erickson, Wendeline B. Everett, Aaron Faber, Joseph R. Farah, Vernon Fath, Thomas W. Folkers, David C. Forbes, Robert Freund, David M. Gale, Feng Gao, Gertie Geertsema, David A. Graham, Christopher H. Greer, Ronald Grosslein, Frédéric Gueth, Daryl Haggard, Nils W. Halverson, Chih-Chiang Han, Kuo-Chang Han, Jinchi Hao, Yutaka Hasegawa, Jason W. Henning, Antonio Hernández-Gómez, Rubén Herrero-Illana, Stefan Heyminck, Akihiko Hirota, James Hoge, Yau-De Huang, C. M. Violette Impellizzeri, Homin Jiang, David John, Atish Kamble, Ryan Keisler, Kimihiro Kimura, Yusuke Kono, Derek Kubo, John Kuroda, Richard Lacasse, Robert A. Laing, Erik M. Leitch, Chao-Te Li, Lupin C.-C. Lin, Ching-Tang Liu, Kuan-Yu Liu, Li-Ming Lu, Ralph G. Marson, Pierre L. Martin-Cocher, Kyle D. Massingill, Callie Matulonis, Martin P. McColl, Stephen R. McWhirter, Hugo Messias, Zheng Meyer-Zhao, Daniel Michalik, Alfredo Montaña, William Montgomerie, Matias Mora-Klein, Dirk Muders, Andrew Nadolski, Santiago Navarro, Joseph Neilsen, Chi H. Nguyen, Hiroaki Nishioka, Timothy Norton, Michael A. Nowak, George Nystrom, Hideo Ogawa, Peter Oshiro, Tomoaki Oyama, Harriet Parsons, Juan Peñalver, Neil M. Phillips, Michael Poirier, Nicolas Pradel, Rurik A. Primiani, Philippe A. Raffin, Alexandra S. Rahlin, George Reiland, Christopher Risacher, Ignacio Ruiz, Alejandro F. Sáez-Madaín, Remi Sassella, Pim Schellart, Paul Shaw, Kevin M. Silva, Hotaka Shiokawa, David R. Smith, William Snow, Kamal Souccar, Don Sousa, Tirupati K. Sridharan, Ranjani Srinivasan, William Stahm, Antony A. Stark, Kyle Story, Sjoerd T. Timmer, Laura Vertatschitsch, Craig Walther, Ta-Shun Wei, Nathan Whitehorn, Alan R. Whitney, David P. Woody, Jan G. A. Wouterloot, Melvin Wright, Paul Yamaguchi, Chen-Yu Yu, Milagros Zeballos, Shuo Zhang, Lucy Ziurys

    Astronomy & Astrophysics   640   A69 - A69   2020.8

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    Publishing type:Research paper (scientific journal)   Publisher:EDP Sciences  

    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 variable <italic>γ</italic>-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 <italic>μ</italic>as (at a redshift of <italic>z</italic> = 0.536 this corresponds to ∼0.13 pc  ∼ 1700 Schwarzschild radii with a black hole mass <italic>M</italic><sub>BH</sub> = 8 × 10<sup>8</sup> <italic>M</italic><sub>⊙</sub>). 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 <italic>c</italic> and ∼20 <italic>c</italic> (∼1.3 and ∼1.7 <italic>μ</italic>as day<sup>−1</sup>, 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 ≲10<sup>10</sup> K, 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.

    DOI: 10.1051/0004-6361/202037493

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  • Verification of Radiative Transfer Schemes for the EHT Reviewed

    Roman Gold, Avery E. Broderick, Ziri Younsi, Christian M. Fromm, Charles F. Gammie, Monika Mościbrodzka, Hung-Yi Pu, Thomas Bronzwaer, Jordy Davelaar, Jason Dexter, David Ball, Chi-kwan Chan, Tomohisa Kawashima, Yosuke Mizuno, Bart Ripperda, Kazunori Akiyama, Antxon Alberdi, Walter Alef, Keiichi Asada, Rebecca Azulay, Anne-Kathrin Baczko, 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, Dominique Broguiere, Do-Young Byun, John E. Carlstrom, Andrew Chael, Koushik Chatterjee, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Ilje Cho, Pierre Christian, John E. Conway, James M. Cordes, Geoffrey B. Crew, Yuzhu Cui, Mariafelicia De Laurentis, Roger Deane, Jessica Dempsey, Gregory Desvignes, Sheperd S. Doeleman, Ralph P. Eatough, Heino Falcke, Vincent L. Fish, Ed Fomalont, Raquel Fraga-Encinas, Bill Freeman, Per Friberg, José L. Gómez, Peter Galison, Roberto García, Olivier Gentaz, Boris Georgiev, Ciriaco Goddi, 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, Makoto Inoue, Sara Issaoun, David J. James, Buell T. Jannuzi, Michael Janssen, Britton Jeter, Wu Jiang, Alejandra Jimenez-Rosales, Michael D. Johnson, Svetlana Jorstad, Taehyun Jung, Mansour Karami, Ramesh Karuppusamy, 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, Rocco Lico, Michael Lindqvist, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin Lonsdale, Ru-Sen Lu, Nicholas R. MacDonald, Sera Markoff, Jirong Mao, Daniel P. Marrone, Alan P. Marscher, Iván Martí-Vidal, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Izumi Mizuno, James M. Moran, Kotaro Moriyama, Cornelia Müller, Hiroshi Nagai, Masanori Nakamura, Neil M. Nagar, Ramesh Narayan, Gopal Narayanan, Iniyan Natarajan, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Hiroki Okino, Gisela N. Ortiz-León, Tomoaki Oyama, Feryal Özel, Daniel C. M. Palumbo, Jongho Park, Nimesh Patel, Ue-Li Pen, Dominic W. Pesce, Richard Plambeck, Vincent Piétu, Aleksandar PopStefanija, Oliver Porth, Jorge A. Preciado-López, Dimitrios Psaltis, Venkatessh Ramakrishnan, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, Luciano Rezzolla, 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, Karl-Friedrich Schuster, F. Peter Schloerb, Lijing Shao, Zhiqiang Shen, Des Small, Bong Won Sohn, Jason SooHoo, Paul Tiede, Fumie Tazaki, Remo P. J. Tilanus, Michael Titus, Kenji Toma, Pablo Torne, Tyler Trent, Thalia Traianou, Sascha Trippe, Shuichiro Tsuda, Huib Jan van Langevelde, Ilse van Bemmel, Daniel R. van Rossum, Jan Wagner, John Wardle, Norbert Wex, Jonathan Weintroub, Robert Wharton, Maciek Wielgus, George N. Wong, Qingwen Wu, Doosoo Yoon, Ken Young, André Young, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Guangyao Zhao, Shan-Shan Zhao, Ziyan Zhu

    The Astrophysical Journal   897 ( 2 )   148 - 148   2020.7

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    DOI: 10.3847/1538-4357/ab96c6

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  • THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope Reviewed

    Avery E. Broderick, Roman Gold, Mansour Karami, Jorge A. Preciado-López, Paul Tiede, Hung-Yi Pu, Kazunori Akiyama, Antxon Alberdi, Walter Alef, Keiichi Asada, Rebecca Azulay, Anne-Kathrin Baczko, 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, Dominique Broguiere, Thomas Bronzwaer, Do-Young Byun, John E. Carlstrom, Andrew Chael, Shami Chatterjee, Koushik Chatterjee, Ming-Tang Chen, Yongjun Chen, Ilje Cho, John E. Conway, James M. Cordes, Geoffrey B. Crew, Yuzhu Cui, Jordy Davelaar, Mariafelicia De Laurentis, Roger Deane, Jessica Dempsey, Gregory Desvignes, Sheperd S. Doeleman, Ralph P. Eatough, Heino Falcke, Vincent L. Fish, Ed Fomalont, Raquel Fraga-Encinas, Per Friberg, Christian M. Fromm, Peter Galison, Charles F. Gammie, Roberto García, Olivier Gentaz, Boris Georgiev, Ciriaco Goddi, José L. Gómez, 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, Makoto Inoue, Sara Issaoun, David J. James, Michael Janssen, Britton Jeter, Wu Jiang, Alejandra Jiménez-Rosales, Michael D. Johnson, Svetlana Jorstad, Taehyun Jung, Ramesh Karuppusamy, Tomohisa Kawashima, Garrett K. Keating, Mark Kettenis, Jae-Young Kim, Jongsoo Kim, Motoki Kino, Jun Yi Koay, Patrick M. Koch, Shoko Koyama, Michael Kramer, Carsten Kramer, Thomas P. Krichbaum, Cheng-Yu Kuo, Sang-Sung Lee, Yan-Rong Li, Zhiyuan Li, Michael Lindqvist, Rocco Lico, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin Lonsdale, Ru-Sen Lu, Nicholas R. MacDonald, Jirong Mao, Alan P. Marscher, Iván Martí-Vidal, Satoki Matsushita, Lynn D. Matthews, 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, Gisela N. Ortiz-León, Tomoaki Oyama, Daniel C. M. Palumbo, Jongho Park, Ue-Li Pen, Dominic W. Pesce, Vincent Piétu, Richard Plambeck, Aleksandar PopStefanija, Oliver Porth, Ben Prather, Venkatessh Ramakrishnan, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, Luciano Rezzolla, Bart Ripperda, Freek Roelofs, Alan Rogers, Eduardo Ros, Mel Rose, Helge Rottmann, 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, Remo P. J. Tilanus, Michael Titus, Kenji Toma, Pablo Torne, Efthalia Traianou, 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, Doosoo Yoon, André Young, Ken Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Guangyao Zhao, Shan-Shan Zhao, Ziyan Zhu

    The Astrophysical Journal   897 ( 2 )   139 - 139   2020.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Astronomical Society  

    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 ofThemis, howThemishas been validated thus far, and present additional analyses made possible byThemisthat illustrate its capabilities. Importantly, we demonstrate thatThemisis 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.Themishas already been used extensively in the scientific analysis and interpretation of the first EHT observations of M87.

    DOI: 10.3847/1538-4357/ab91a4

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  • SYMBA: An end-to-end VLBI synthetic data generation pipeline Reviewed

    F. Roelofs, M. Janssen, I. Natarajan, R. Deane, J. Davelaar, H. Olivares, O. Porth, S. N. Paine, K. L. Bouman, R. P. J. Tilanus, I. M. van Bemmel, H. Falcke, K. Akiyama, A. Alberdi, W. Alef, K. Asada, R. Azulay, A. Baczko, D. Ball, M. Baloković, J. Barrett, D. Bintley, L. Blackburn, W. Boland, G. C. Bower, M. Bremer, C. D. Brinkerink, R. Brissenden, S. Britzen, A. E. Broderick, D. Broguiere, T. Bronzwaer, D. Byun, J. E. Carlstrom, A. Chael, C. Chan, S. Chatterjee, K. Chatterjee, M. Chen, Y. Chen, I. Cho, P. Christian, J. E. Conway, J. M. Cordes, G. B. Crew, Y. Cui, M. De Laurentis, J. Dempsey, G. Desvignes, J. Dexter, S. S. Doeleman, R. P. Eatough, V. L. Fish, E. Fomalont, R. Fraga-Encinas, P. Friberg, C. M. Fromm, J. L. Gómez, P. Galison, C. F. Gammie, R. García, O. Gentaz, B. Georgiev, C. Goddi, R. Gold, M. Gu, M. Gurwell, K. Hada, M. H. Hecht, R. Hesper, L. C. Ho, P. Ho, M. Honma, C. L. Huang, L. Huang, D. H. Hughes, S. Ikeda, M. Inoue, S. Issaoun, D. J. James, B. T. Jannuzi, B. Jeter, W. Jiang, M. D. Johnson, S. Jorstad, T. Jung, M. Karami, R. Karuppusamy, T. Kawashima, G. K. Keating, M. Kettenis, J. Kim, J. Kim, J. Kim, M. Kino, J. Y. Koay, P. M. Koch, S. Koyama, M. Kramer, C. Kramer, T. P. Krichbaum, C. Kuo, T. R. Lauer, S. Lee, Y. Li, Z. Li, M. Lindqvist, R. Lico, K. Liu, E. Liuzzo, W. Lo, A. P. Lobanov, L. Loinard, C. Lonsdale, R. Lu, N. R. MacDonald, J. Mao, S. Markoff, D. P. Marrone, A. P. Marscher, I. Martí-Vidal, S. Matsushita, L. D. Matthews, L. Medeiros, K. M. Menten, Y. Mizuno, I. Mizuno, J. M. Moran, K. Moriyama, M. Moscibrodzka, C. Müller, H. Nagai, N. M. Nagar, M. Nakamura, R. Narayan, G. Narayanan, R. Neri, C. Ni, A. Noutsos, H. Okino, H. Olivares, G. N. Ortiz-León, T. Oyama, F. Özel, D. C. M. Palumbo, N. Patel, U. Pen, D. W. Pesce, V. Piétu, R. Plambeck, A. PopStefanija, B. Prather, J. A. Preciado-López, D. Psaltis, H. Pu, V. Ramakrishnan, R. Rao, M. G. Rawlings, A. W. Raymond, L. Rezzolla, B. Ripperda, A. Rogers, E. Ros, M. Rose, A. Roshanineshat, H. Rottmann, A. L. Roy, C. Ruszczyk, B. R. Ryan, K. L. J. Rygl, S. Sánchez, D. Sánchez-Arguelles, M. Sasada, T. Savolainen, F. P. Schloerb, K. Schuster, L. Shao, Z. Shen, D. Small, B. Won Sohn, J. SooHoo, F. Tazaki, P. Tiede, M. Titus, K. Toma, P. Torne, E. Traianou, T. Trent, S. Trippe, S. Tsuda, H. J. van Langevelde, D. R. van Rossum, J. Wagner, J. Wardle, J. Weintroub, N. Wex, R. Wharton, M. Wielgus, G. N. Wong, Q. Wu, A. Young, K. Young, Z. Younsi, F. Yuan, Y. Yuan, J. A. Zensus, G. Zhao, S. Zhao, Z. Zhu

    Astronomy & Astrophysics   636   A5 - A5   2020.4

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    <italic>Context.</italic> Realistic synthetic observations of theoretical source models are essential for our understanding of real observational data. In using synthetic data, one can verify the extent to which source parameters can be recovered and evaluate how various data corruption effects can be calibrated. These studies are the most important when proposing observations of new sources, in the characterization of the capabilities of new or upgraded instruments, and when verifying model-based theoretical predictions in a direct comparison with observational data.


    <italic>Aims.</italic> We present the SYnthetic Measurement creator for long Baseline Arrays (<monospace>SYMBA</monospace>), a novel synthetic data generation pipeline for Very Long Baseline Interferometry (VLBI) observations. <monospace>SYMBA</monospace> takes into account several realistic atmospheric, instrumental, and calibration effects.


    <italic>Methods.</italic> We used <monospace>SYMBA</monospace> to create synthetic observations for the Event Horizon Telescope (EHT), a millimetre VLBI array, which has recently captured the first image of a black hole shadow. After testing <monospace>SYMBA</monospace> with simple source and corruption models, we study the importance of including all corruption and calibration effects, compared to the addition of thermal noise only. Using synthetic data based on two example general relativistic magnetohydrodynamics (GRMHD) model images of M 87, we performed case studies to assess the image quality that can be obtained with the current and future EHT array for different weather conditions.


    <italic>Results.</italic> Our synthetic observations show that the effects of atmospheric and instrumental corruptions on the measured visibilities are significant. Despite these effects, we demonstrate how the overall structure of our GRMHD source models can be recovered robustly with the EHT2017 array after performing calibration steps, which include fringe fitting, a priori amplitude and network calibration, and self-calibration. With the planned addition of new stations to the EHT array in the coming years, images could be reconstructed with higher angular resolution and dynamic range. In our case study, these improvements allowed for a distinction between a thermal and a non-thermal GRMHD model based on salient features in reconstructed images.

    DOI: 10.1051/0004-6361/201936622

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  • The Event Horizon General Relativistic Magnetohydrodynamic Code Comparison Project Reviewed

    Oliver Porth, Koushik Chatterjee, Ramesh Narayan, Charles F. Gammie, Yosuke Mizuno, Peter Anninos, John G. Baker, Matteo Bugli, Chi-kwan Chan, Jordy Davelaar, Luca Del Zanna, Zachariah B. Etienne, P. Chris Fragile, Bernard J. Kelly, Matthew Liska, Sera Markoff, Jonathan C. McKinney, Bhupendra Mishra, Scott C. Noble, Héctor Olivares, Ben Prather, Luciano Rezzolla, Benjamin R. Ryan, James M. Stone, Niccolò Tomei, Christopher J. White, Ziri Younsi, 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, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Ilje Cho, Pierre Christian, John E. Conway, James M. Cordes, Geoffrey, B. Crew, Yuzhu Cui, Mariafelicia De Laurentis, Roger Deane, Jessica Dempsey, Gregory Desvignes, Sheperd S. Doeleman, Ralph P. Eatough, Heino Falcke, Vincent L. Fish, Ed Fomalont, Raquel Fraga-Encinas, Bill Freeman, Per Friberg, Christian M. Fromm, José L. Gómez, Peter Galison, 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, Daniel P. Marrone, Alan P. Marscher, Iván Martí-Vidal, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Izumi Mizuno, James M. Moran, Kotaro Moriyama, Monika Moscibrodzka, Cornelia Müller, Hiroshi Nagai, Neil M. Nagar, Masanori Nakamura, Gopal Narayanan, Iniyan Natarajan, Roberto Neri, Chunchong Ni, Aristeidis Noutsos, Hiroki Okino, Tomoaki Oyama, Feryal Özel, Daniel C. M. Palumbo, Nimesh Patel, Ue-Li Pen, Dominic W. Pesce, Vincent Piétu, Richard Plambeck, Aleksandar PopStefanija, Jorge A. Preciado-López, Dimitrios Psaltis, Hung-Yi Pu, Venkatessh Ramakrishnan, Ramprasad Rao, Mark G. Rawlings, Alexander W. Raymond, 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, 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, Ken Young, André Young, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Guangyao Zhao, Shan-Shan Zhao, Ziyan Zhu

    The Astrophysical Journal Supplement Series   243 ( 2 )   26 - 26   2019.8

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    Publishing type:Research paper (scientific journal)   Publisher:American Astronomical Society  

    DOI: 10.3847/1538-4365/ab29fd

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  • Jet kinematics of the quasar 4C+21.35 from observations with the KaVA very long baseline interferometry array

    Taeseok Lee, Sascha Trippe, Motoki Kino, Bong Won Sohn, Jongho Park, Junghwan Oh, Kazuhiro Hada, Kotaro Niinuma, Hyunwook Ro, Taehyun Jung, Guang-Yao Zhao, Sang-Sung Lee, Juan-Carlos Algaba, Kazunori Akiyama, Kiyoaki Wajima, Satoko Sawada-Satoh, Fumie Tazaki, Ilje Cho, Jeffrey Hodgson, Jeong Ae Lee, Yoshiaki Hagiwara, Mareki Honma, Shoko Koyama, Tao An, Yuzhu Cui, Hyemin Yoo, Noriyuki Kawaguchi, Duk-Gyoo Roh, Se-Jin Oh, Jae-Hwan Yeom, Dong-Kyu Jung, Chungsik Oh, Hyo-Ryoung Kim, Ju-Yeon Hwang, Do-Young Byun, Se-Hyung Cho, Hyun-Goo Kim, Hideyuki Kobayashi, Katsunori M. Shibata, Zhiqiang Shen, Wu Jiang, Jee Won Lee

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   486 ( 2 )   2412 - 2421   2019.6

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    We present the jet kinematics of the flat spectrum radio quasar (FSRQ) 4C+21.35 using time-resolved KaVA very long baseline interferometry array radio maps obtained from 2014 September to 2016 July. During two out of three observing campaigns, observations were performed bi-weekly at 22 and 43 GHz quasi-simultaneously. At 22 GHz, we identified three jet components near the core with apparent speeds up to (14.4 +/- 2.1)c. The timing of the ejection of a new component detected in 2016 is consistent with a gamma-ray flare in 2014 November. At 43 GHz, we found four inner jet (<3 mas) components with speeds from (3.5 +/- 1.4)c to (6.8 +/- 1.5)c. Jet component speeds tend to be higher with increasing distances from the core. We compared our data with archival Very Long Baseline Array (VLBA) data from the Boston University (BU) 43 GHz and the Monitoring Of Jets in Active galactic nuclei with VLBA Experiments (MOJAVE) 15.4 GHz monitoring programmes. Whereas MOJAVE data and our data are in good agreement, jet speeds obtained from the BU programme data in the same time period are about twice as high as the ones we obtain from the KaVA data. The discrepancy at 43 GHz indicates that radio arrays with different angular resolution identify and trace different jet features even when the data are obtained at the same frequency and at the same time. The flux densities of jet components decay exponentially, in agreement with a synchrotron cooling time-scale of similar to 1 yr. Using known electron Lorentz factor values (similar to 9000), we estimate the magnetic field strength to be similar to 1-3 mu T. When adopting a jet viewing angle of 5 degrees, the intrinsic jet speed is of order 0.99c.

    DOI: 10.1093/mnras/stz970

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  • First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole Reviewed

    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, 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

    The Astrophysical Journal   875 ( 1 )   L6 - L6   2019.4

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    DOI: 10.3847/2041-8213/ab1141

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  • First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole Reviewed

    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, Gisela N. Ortiz-León, 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, Ken Young, André Young, Ziri Younsi, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Guangyao Zhao, Shan-Shan Zhao, Ziyan Zhu, Juan-Carlos Algaba, Alexander Allardi, Rodrigo Amestica, Jadyn Anczarski, Uwe Bach, Frederick K. Baganoff, Christopher Beaudoin, Bradford A. Benson, Ryan Berthold, Jay M. Blanchard, Ray Blundell, Sandra Bustamente, Roger Cappallo, Edgar Castillo-Domínguez, Chih-Cheng Chang, Shu-Hao Chang, Song-Chu Chang, Chung-Chen Chen, Ryan Chilson, Tim C. Chuter, Rodrigo Córdova Rosado, Iain M. Coulson, Thomas M. Crawford, Joseph Crowley, John David, Mark Derome, Matthew Dexter, Sven Dornbusch, Kevin A. Dudevoir, Sergio A. Dzib, Andreas Eckart, Chris Eckert, Neal R. Erickson, Wendeline B. Everett, Aaron Faber, Joseph R. Farah, Vernon Fath, Thomas W. Folkers, David C. Forbes, Robert Freund, Arturo I. Gómez-Ruiz, David M. Gale, Feng Gao, Gertie Geertsema, David A. Graham, Christopher H. Greer, Ronald Grosslein, Frédéric Gueth, Daryl Haggard, Nils W. Halverson, Chih-Chiang Han, Kuo-Chang Han, Jinchi Hao, Yutaka Hasegawa, Jason W. Henning, Antonio Hernández-Gómez, Rubén Herrero-Illana, Stefan Heyminck, Akihiko Hirota, James Hoge, Yau-De Huang, C. M. Violette Impellizzeri, Homin Jiang, Atish Kamble, Ryan Keisler, Kimihiro Kimura, Yusuke Kono, Derek Kubo, John Kuroda, Richard Lacasse, Robert A. Laing, Erik M. Leitch, Chao-Te Li, Lupin C.-C. Lin, Ching-Tang Liu, Kuan-Yu Liu, Li-Ming Lu, Ralph G. Marson, Pierre L. Martin-Cocher, Kyle D. Massingill, Callie Matulonis, Martin P. McColl, Stephen R. McWhirter, Hugo Messias, Zheng Meyer-Zhao, Daniel Michalik, Alfredo Montaña, William Montgomerie, Matias Mora-Klein, Dirk Muders, Andrew Nadolski, Santiago Navarro, Joseph Neilsen, Chi H. Nguyen, Hiroaki Nishioka, Timothy Norton, Michael A. Nowak, George Nystrom, Hideo Ogawa, Peter Oshiro, Tomoaki Oyama, Harriet Parsons, Scott N. Paine, Juan Peñalver, Neil M. Phillips, Michael Poirier, Nicolas Pradel, Rurik A. Primiani, Philippe A. Raffin, Alexandra S. Rahlin, George Reiland, Christopher Risacher, Ignacio Ruiz, Alejandro F. Sáez-Madaín, Remi Sassella, Pim Schellart, Paul Shaw, Kevin M. Silva, Hotaka Shiokawa, David R. Smith, William Snow, Kamal Souccar, Don Sousa, T. K. Sridharan, Ranjani Srinivasan, William Stahm, Anthony A. Stark, Kyle Story, Sjoerd T. Timmer, Laura Vertatschitsch, Craig Walther, Ta-Shun Wei, Nathan Whitehorn, Alan R. Whitney, David P. Woody, Jan G. A. Wouterloot, Melvin Wright, Paul Yamaguchi, Chen-Yu Yu, Milagros Zeballos, Shuo Zhang, Lucy Ziurys

    The Astrophysical Journal   875 ( 1 )   L1 - L1   2019.4

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    When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 +/- 3 mu as, which is circular and encompasses a central depression in brightness with a flux ratio greater than or similar to 10: 1. The emission ring is recovered using different calibration and imaging schemes, with its diameter and width remaining stable over four different observations carried out in different days. Overall, the observed image is consistent with expectations for the shadow of a Kerr black hole as predicted by general relativity. The asymmetry in brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to the speed of light around a black hole. We compare our images to an extensive library of ray-traced general-relativistic magnetohydrodynamic simulations of black holes and derive a central mass of M = (6.5 +/- 0.7) x 10(9) M-circle dot. Our radio-wave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies and as the central engines of active galactic nuclei. They also present a new tool to explore gravity in its most extreme limit and on a mass scale that was so far not accessible.

    DOI: 10.3847/2041-8213/ab0ec7

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  • First M87 Event Horizon Telescope Results. II. Array and Instrumentation Reviewed

    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, 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, Gisela N. Ortiz-León, 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, Juan-Carlos Algaba, Alexander Allardi, Rodrigo Amestica, Uwe Bach, Christopher Beaudoin, Bradford A. Benson, Ryan Berthold, Jay M. Blanchard, Ray Blundell, Sandra Bustamente, Roger Cappallo, Edgar Castillo-Domínguez, Chih-Cheng Chang, Shu-Hao Chang, Song-Chu Chang, Chung-Chen Chen, Ryan Chilson, Tim C. Chuter, Rodrigo Córdova Rosado, Iain M. Coulson, Thomas M. Crawford, Joseph Crowley, John David, Mark Derome, Matthew Dexter, Sven Dornbusch, Kevin A. Dudevoir, Sergio A. Dzib, Chris Eckert, Neal R. Erickson, Wendeline B. Everett, Aaron Faber, Joseph R. Farah, Vernon Fath, Thomas W. Folkers, David C. Forbes, Robert Freund, Arturo I. Gómez-Ruiz, David M. Gale, Feng Gao, Gertie Geertsema, David A. Graham, Christopher H. Greer, Ronald Grosslein, Frédéric Gueth, Nils W. Halverson, Chih-Chiang Han, Kuo-Chang Han, Jinchi Hao, Yutaka Hasegawa, Jason W. Henning, Antonio Hernández-Gómez, Rubén Herrero-Illana, Stefan Heyminck, Akihiko Hirota, James Hoge, Yau-De Huang, C. M. Violette Impellizzeri, Homin Jiang, Atish Kamble, Ryan Keisler, Kimihiro Kimura, Yusuke Kono, Derek Kubo, John Kuroda, Richard Lacasse, Robert A. Laing, Erik M. Leitch, Chao-Te Li, Lupin C.-C. Lin, Ching-Tang Liu, Kuan-Yu Liu, Li-Ming Lu, Ralph G. Marson, Pierre L. Martin-Cocher, Kyle D. Massingill, Callie Matulonis, Martin P. McColl, Stephen R. McWhirter, Hugo Messias, Zheng Meyer-Zhao, Daniel Michalik, Alfredo Montaña, William Montgomerie, Matias Mora-Klein, Dirk Muders, Andrew Nadolski, Santiago Navarro, Chi H. Nguyen, Hiroaki Nishioka, Timothy Norton, George Nystrom, Hideo Ogawa, Peter Oshiro, Tomoaki Oyama, Stephen Padin, Harriet Parsons, Scott N. Paine, Juan Peñalver, Neil M. Phillips, Michael Poirier, Nicolas Pradel, Rurik A. Primiani, Philippe A. Raffin, Alexandra S. Rahlin, George Reiland, Christopher Risacher, Ignacio Ruiz, Alejandro F. Sáez-Madaín, Remi Sassella, Pim Schellart, Paul Shaw, Kevin M. Silva, Hotaka Shiokawa, David R. Smith, William Snow, Kamal Souccar, Don Sousa, T. K. Sridharan, Ranjani Srinivasan, William Stahm, Antony A. Stark, Kyle Story, Sjoerd T. Timmer, Laura Vertatschitsch, Craig Walther, Ta-Shun Wei, Nathan Whitehorn, Alan R. Whitney, David P. Woody, Jan G. A. Wouterloot, Melvin Wright, Paul Yamaguchi, Chen-Yu Yu, Milagros Zeballos, Lucy Ziurys

    The Astrophysical Journal   875 ( 1 )   L2 - L2   2019.4

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    DOI: 10.3847/2041-8213/ab0c96

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  • First M87 Event Horizon Telescope Results. III. Data Processing and Calibration Reviewed

    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, 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, Gisela N. Ortiz-León, 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, Roger Cappallo, Joseph R. Farah, Thomas W. Folkers, Zheng Meyer-Zhao, Daniel Michalik, Andrew Nadolski, Hiroaki Nishioka, Nicolas Pradel, Rurik A. Primiani, Kamal Souccar, Laura Vertatschitsch, Paul Yamaguchi

    The Astrophysical Journal   875 ( 1 )   L3 - L3   2019.4

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    DOI: 10.3847/2041-8213/ab0c57

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  • First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring Reviewed

    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, 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 Mul̈ler, 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, Jadyn Anczarski, Frederick K. Baganoff, Andreas Eckart, Joseph R. Farah, Daryl Haggard, Zheng Meyer-Zhao, Daniel Michalik, Andrew Nadolski, Joseph Neilsen, Hiroaki Nishioka, Michael A. Nowak, Nicolas Pradel, Rurik A. Primiani, Kamal Souccar, Laura Vertatschitsch, Paul Yamaguchi, Shuo Zhang

    The Astrophysical Journal   875 ( 1 )   L5 - L5   2019.4

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    The Event Horizon Telescope (EHT) has mapped the central compact radio source of the elliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Here we consider the physical implications of the asymmetric ring seen in the 2017 EHT data. To this end, we construct a large library of models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by general relativistic ray tracing. We compare the observed visibilities with this library and confirm that the asymmetric ring is consistent with earlier predictions of strong gravitational lensing of synchrotron emission from a hot plasma orbiting near the black hole event horizon. The ring radius and ring asymmetry depend on black hole mass and spin, respectively, and both are therefore expected to be stable when observed in future EHT campaigns. Overall, the observed image is consistent with expectations for the shadow of a spinning Kerr black hole as predicted by general relativity. If the black hole spin and M87's large scale jet are aligned, then the black hole spin vector is pointed away from Earth. Models in our library of non-spinning black holes are inconsistent with the observations as they do not produce sufficiently powerful jets. At the same time, in those models that produce a sufficiently powerful jet, the latter is powered by extraction of black hole spin energy through mechanisms akin to the Blandford-Znajek process. We briefly consider alternatives to a black hole for the central compact object. Analysis of existing EHT polarization data and data taken simultaneously at other wavelengths will soon enable new tests of the GRMHD models, as will future EHT campaigns at 230 and 345 GHz.

    DOI: 10.3847/2041-8213/ab0f43

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  • Accretion disk versus jet orientation in H2O megamaser galaxies Reviewed

    F. Kamali, C. Henkel, S. Koyama, C. Y. Kuo, J. J. Condon, A. Brunthaler, M. J. Reid, J. E. Greene, K. M. Menten, C. M. V. Impellizzeri, J. A. Braatz, E. Litzinger, M. Kadler

    Astronomy & Astrophysics   624   A42 - A42   2019.4

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    <italic>Context</italic>. An essential part of the paradigm describing active galactic nuclei is the alignment between the radio jet and the associated rotation axis of the sub-pc accretion disks. Because of the small linear and angular scales involved, this alignment has not yet been checked in a sufficient number of low luminosity active galactic nuclei (LLAGNs).


    <italic>Aims</italic>. The project examines the validity of this paradigm by measuring the radio continuum on the same physical scale as the accretion disks to investigate any possible connection between these disks and the radio continuum.


    <italic>Methods</italic>. We observed a sample of 18 LLAGNs in the 4.8 GHz (6 cm) radio continuum using the Very Long Baseline Array (VLBA) with 3.3–6.5 ms resolution. The sources were selected to show both an edge-on accretion disk revealed by 22 GHz H<sub>2</sub>O megamaser emission and signatures of a radio jet. Furthermore, the sources were previously detected in 33 GHz radio continuum observations made with the Very Large Array.


    <italic>Results</italic>. Five out of 18 galaxies observed were detected at 8<italic>σ</italic> or higher levels (Mrk 0001, Mrk 1210, Mrk 1419, NGC 2273, and UGC 3193). While these five sources are known to have maser disks, four of them exhibit a maser disk with known orientation. For all four of these sources, the radio continuum is misaligned relative to the rotation axis of the maser disk, but with a 99.1% confidence level, the orientations are not random and are confined to a cone within 32<sup>°</sup> of the maser disk’s normal. Among the four sources the misalignment of the radio continuum with respect to the normal vector to the maser disk is smaller when the inner radius of the maser disk is larger. Furthermore, a correlation is observed between the 5 GHz VLBA radio continuum and the [OIII] luminosity and also with the H<sub>2</sub>O maser disk’s inner radius.

    DOI: 10.1051/0004-6361/201834600

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  • A balloon-borne very long baseline interferometry experiment in the stratosphere: Systems design and developments Reviewed

    Akihiro Doi, Yusuke Kono, Kimihiro Kimura, Satomi Nakahara, Tomoaki Oyama, Nozomi Okada, Yasutaka Satou, Kazuyoshi Yamashita, Naoko Matsumoto, Mitsuhisa Baba, Daisuke Yasuda, Shunsaku Suzuki, Yutaka Hasegawa, Mareki Honma, Hiroaki Tanaka, Kosei Ishimura, Yasuhiro Murata, Reiho Shimomukai, Tomohiro Tachi, Kazuya Saito, Naohiko Watanabe, Nobutaka Bando, Osamu Kameya, Yoshinori Yonekura, Mamoru Sekido, Yoshiyuki Inoue, Hiraku Sakamoto, Nozomu Kogiso, Yasuhiro Shoji, Hideo Ogawa, Kenta Fujisawa, Masanao Narita, Hiroshi Shibai, Hideyuki Fuke, Kenta Uehara, Shoko Koyama

    Advances in Space Research   63 ( 1 )   779 - 793   2019.1

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    The balloon-borne very long baseline interferometry (VLBI) experiment is a technical feasibility study for performing radio interferometry in the stratosphere. The flight model has been developed. A balloon-borne VLBI station will be launched to establish interferometric fringes with ground-based VLBI stations distributed over the Japanese islands at an observing frequency of approximately 20 GHz as the first step. This paper describes the system design and development of a series of observing instruments and bus systems. In addition to the advantages of avoiding the atmospheric effects of absorption and fluctuation in high frequency radio observation, the mobility of a station can improve the sampling coverage ("uv-coverage") by increasing the number of baselines by the number of ground-based counterparts for each observation day. This benefit cannot be obtained with conventional arrays that solely comprise ground-based stations. The balloon-borne VLBI can contribute to a future progress of research fields such as black holes by direct imaging. (C) 2018 Published by Elsevier Ltd on behalf of COSPAR.

    DOI: 10.1016/j.asr.2018.09.020

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  • Parabolic Jets from the Spinning Black Hole in M87 Reviewed

    Masanori Nakamura, Keiichi Asada, Kazuhiro Hada, Hung-Yi Pu, Scott Noble, Chihyin Tseng, Kenji Toma, Motoki Kino, Hiroshi Nagai, Kazuya Takahashi, Juan-Carlos Algaba, Monica Orienti, Kazunori Akiyama, Akihiro Doi, Gabriele Giovannini, Marcello Giroletti, Mareki Honma, Shoko Koyama, Rocco Lico, Kotaro Niinuma, Fumie Tazaki

    The Astrophysical Journal   868 ( 2 )   146 - 146   2018.12

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    The M87 jet is extensively examined by utilizing general relativistic magnetohydrodynamic (GRMHD) simulations, as well as the steady axisymmetric force-free electrodynamic (FFE) solution. Quasi-steady funnel jets are obtained in GRMHD simulations up to the scale of similar to 100 gravitational radii (r(g)) for various black hole (BH) spins. As is known, the funnel edge is approximately determined by the following equipartitions: (i) the magnetic and rest-mass energy densities and (ii) the gas and magnetic pressures. Our numerical results give an additional factor that they follow the outermost parabolic streamline of the FFE solution, which is anchored to the event horizon on the equatorial plane. We also show that the matter-dominated, nonrelativistic corona/wind plays a dynamical role in shaping the funnel jet into the parabolic geometry. We confirm a quantitative overlap between the outermost parabolic streamline of the FFE jet and the edge of the jet sheath in very long baseline interferometry (VLBI) observations at similar to(10(1)-10(5))r(g), suggesting that the M87 jet is likely powered by the spinning BH. Our GRMHD simulations also indicate a lateral stratification of the bulk acceleration (i.e., the spine-sheath structure), as well as an emergence of knotty superluminal features. The spin characterizes the location of the jet stagnation surface inside the funnel. We suggest that the limb-brightened feature could be associated with the nature of the BH-driven jet, if the Doppler beaming is a dominant factor. Our findings can be examined with (sub)millimeter VLBI observations, giving a clue for the origin of the M87 jet.

    DOI: 10.3847/1538-4357/aaeb2d

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  • VERA monitoring of the radio jet 3C 84 in the period of 2007–2013: Detection of non-linear motion Reviewed

    Koichiro Hiura, Hiroshi Nagai, Motoki Kino, Kotaro Niinuma, Kazuo Sorai, Hikaru Chida, Kazunori Akiyama, Filippo D’Ammando, Gabriele Giovannini, Marcello Giroletti, Kazuhiro Hada, Mareki Honma, Shoko Koyama, Monica Orienti, Gabor Orosz, Satoko Sawada-Satoh

    Publications of the Astronomical Society of Japan   70 ( 5 )   2018.10

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    We present a kinematic study of the sub-parsec-scale radio jet of the radio galaxy 3C 84/NGC 1275 with the VLBI Exploration of Radio Astrometry (VERA) array at 22 GHz for 80 epochs from 2007 October to 2013 December. The averaged radial velocity of the bright component "C3" with reference to the radio core is found to be 0.27 +/- 0.02 c between 2007 October and 2013 December. This constant velocity of C3 is naturally explained by the advancing motion of the head of the mini-radio lobe. We also find a non-linear component in the motion of C3 with respect to the radio core. We briefly discuss possible origins of this non-linear motion.

    DOI: 10.1093/pasj/psy078

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  • Electronics instrumentation for the Greenland telescope Reviewed

    Derek Y. Kubo, Johnson C. C. Han, Hiroaki Nishioka, Ryan Chilson, Ranjani Srinivasan, Ta-Shun Wei, Chih-Wei L. Huang, Chen-Yu Yu, Peter Oshiro, Philippe Raffin, Yau-De Huang, Keiichi Asada, Shoko Koyama, Daniel Bintley, Craig Walther, Per Friberg, Ming-Tang Chen, Satoki Matsushita, Paul T. P. Ho, Kuan-Yu Liu, Pierre Martin-Cocher, Sheng-Feng Yen, Kuo-Chieh Fu, homin Jiang, Shu-Hao Chang, Chung-Cheng Chen, Makoto Inoue, Patrick Koch, Yang-Tai Shaw, Timothy J. Norton, Nimesh A. Patel, Shepherd S. Doeleman, Jessica Dempsey, Ching-Tang Liu, Kou-Chang Han, Song-Chu Chang, Li-Ming Lu, Hideo Ogawa, Kimihiro Kimura, Yutaka Hasegawa

    Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX   10708   2018.7

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:SPIE  

    The Greenland Telescope project has recently participated in an experiment to image the supermassive black hole shadow at the center of M87 using Very Long Baseline Interferometry technique in April of 2018. The antenna consists of the 12-m ALMA North American prototype antenna that was modified to support two auxiliary side containers and to withstand an extremely cold environment. The telescope is currently at Thule Air Base in Greenland with the long-term goal to move the telescope over the Greenland ice sheet to Summit Station. The GLT currently has a single cryostat which houses three dual polarization receivers that cover 84-96 GHz, 213-243 GHz and 271-377 GHz bands. A hydrogen maser frequency source in conjunction with high frequency synthesizers are used to generate the local oscillator references for the receivers. The intermediate frequency outputs of each receiver cover 4-8 GHz and are heterodyned to baseband for digitization within a set of ROACH-2 units then formatted for recording onto Mark-6 data recorders. A separate set of ROACH-2 units operating in parallel provides the function of auto-correlation for real-time spectral analysis. Due to the stringent instrumental stability requirements for interferometry a diagnostic test system was incorporated into the design. Tying all of the above equipment together is the fiber optic system designed to operate in a low temperature environment and scalable to accommodate a larger distance between the control module and telescope for Summit Station. A report on the progress of the above electronics instrumentation system will be provided.

    DOI: 10.1117/12.2312241

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  • GLT receiver commissioning at JCMT and future JCMT instrumentation Reviewed

    Daniel Bintley, Per Friberg, Ryan Berthold, Tim Chuter, Craig Walther, Kuan-Yu Liu, Jessica Dempsey, Paul T. P. Ho, Helen McGregor, Satoki Matsushita, Keiichi Asada, Shoko Koyama, Hiroaki Nishioka, Johnson C. C. Han, Chih-Wei L. Huang, Lupin C. C. Lin, Ta-Shun Wei, Ming-Tang Chen, Derek Y. Kubo, Ranjani Srinivasan, Geoff Bower, Peter Oshiro, Ramprasad Rao

    Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX   10708   2018.7

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    The Greenland Telescope (GLT) project and the East Asian Observatory (EAO) successfully commissioned the first light GLT instrument at the James Clerk Maxwell Telescope (JCMT) in Hawaii, prior to transferring the instrument to Greenland. The GLT instrument which comprises of a cryostat with three cartridge-type receivers (at 86GHz, 230GHz and 345GHz) was installed into the receiver cabin of JCMT and operated in three modes: - (a) Regular JCMT observing with the GLT instrument, using ACSIS, (JCMT's autocorrelation spectrometer) as the backend and JCMT software for telescope control, data reduction, pointing and antenna focus adjustment. (b) Single dish observations of astronomical spectral line sources, recording data onto mark 6 recorders for offline data reduction. (c) eSMA interferometer array observations at 230GHz in conjunction with the SMA. In this paper, we report on the installation and integration of the GLT instrument at JCMT, present results from commissioning and show how the success of the GLT instrument commissioning fits with our plans for future instrumentation at JCMT.

    DOI: 10.1117/12.2313083

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  • Control and monitoring system for the Greenland telescope: computers, network and software Reviewed

    Hiroaki Nishioka, Chih-Wei L. Huang, Patel A. Patel, Derek Y. Kubo, Pierre Martin-Cocher, Chih-Chiang J. Han, Chen-Yu Yu, Homin Jiang, Ranjani Srinivasan, Satoki Matsushita, Keiichi Asada, Geoffrey C. Bower, Shu-Hao Chang, Ming-Tang Chen, Paul T. P. Ho, Yau-De Huang, Makoto Inoue, Shoko Koyama, Lupin C. C. Lin, Ching-Tang Liu, Timothy J. Norton, George U. Nystrom, Ta-Shun Wei, Ryan M. Berthold, Per Friberg, Tim Chuter, Kuan-Yu Liu, Craig A. Walther, Jun-Yi Koay, Wen-Ping Lo, Patrick M. Koch, Oshiro Peter, Zheng Meyer-Zhao, Dan Bintley, Dempsey Jessica, Masanori Nakamura, Sheperd S. Doeleman

    Ground-based and Airborne Telescopes VII   10700   2018.7

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    We describe the control and monitoring system for the Greenland Telescope (GLT). The GLT is a 12-m radio telescope aiming to carry out the sub-millimeter Very Long Baseline Interferometry (VLBI) observations and image the shadow of the super massive black hole in M87. In November 2017 construction has been finished and commissioning activity has been started. In April 2018 we participated in the VLBI observing campaign for the Event Horizon Telescope (EHT) collaboration. In this paper we present the entire GLT control/monitoring system in terms of computers, network and software.

    DOI: 10.1117/12.2313104

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  • The Greenland telescope: Thule operations Reviewed

    Ming-Tang Chen, Philippe A. Raffin, Paul T. P. Ho, Keiichi Asada, Satoki Matsushita, Chih-Chiang J. Han, Hiroaki Nishioka, Ta-Shun Wei, Patrick M. Koch, Makoto Inoue, George U. Nystrom, Derek Y. Kubo, Jack C. Chang, Fang-Chia Hsieh, Hung-Yi Pu, Lupin C. Lin, Paul Y. Shaw, Homin Jiang, Ted Y. Huang, Locutus C. Huang, Joshua S. Chang, Timothy J. Norton, Nimesh A. Patel, Bill C. Liu, Pierre Martin-Cocher, Chung-Chen Chen, Ryan Chilson, Ranjani Srinivasan, Kuan-Yu Liu, Chen-Yu Yu, Geoffrey C. Bower, Peter Oshiro, William Snow, Shoko Koyama, Jun Yi Koay, Chao-Te Li, Weng-Ping Lo, Masanori Nakamura, Daniel Bintley, Craig Walther, Per Friberg, Jessica Dempsey, T.K. Sridharan, Sheperd S. Doeleman, Roger Brissenden, Hideo Ogawa, Kimihiro Hasegawa, Hao Jinchi, Kuo-Chang Han, Song-Chu Chang, Li-Ming L. Lu, Juan-Carlos Algaba Marcos, Alex Allardi, Aaron Faber, Wei-Long Chen, Fu-Li Hsu, Zheng Meyer-Zhao, Yutaka Hasegawa

    Ground-based and Airborne Telescopes VII   10700   2018.7

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    The Greenland Telescope Project (GLT) has successfully commissioned its 12-m sub-millimeter. In January 2018, the fringes were detected between the GLT and the Atacama Large Millimeter Array (ALMA) during a very-long-baseline-interferometry (VLBI) exercise. In April 2018, the telescope participated in global VLBI science observations at Thule Air Base (TAB). The telescope has been completely rebuilt, with many new components, from the ALMA NA (North America) Prototype antenna and equipped with a new set of sub-millimeter receivers operating at 86, 230, and 345 GHz, as well as a complete set of instruments and VLBI backends. This paper describes our progress and status of the project and its plan for the coming decade.

    DOI: 10.1117/12.2313378

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  • Commissioning status of the Greenland telescope Reviewed

    Satoki Matsushita, Jun-Yi Koay, Wen-Ping Lo, Aaron Faber, Kou-Chang Han, Song-Chu Chang, Li-Ming Lu, Keiichi Asada, Johnson C. C. Han, Hiroaki Nishioka, Shoko Koyama, Chih-Wei L. Huang, Lupin C. C. Lin, Kuan-Yu Liu, Chen-Yu Yu, Ming-Tang Chen, Paul T. P. Ho, Derek Y. Kubo, Ranjani Srinivasan, Geoffrey C. Bower, Makoto Inoue, Dan Bintley, Per Friberg, Ryan M. Berthold, Craig A. Walther, Jessica T. Dempsey, Jonathan Weintroub, André Young, Ken Young, Nimesh A. Patel, Patrick M. Koch, Zheng Meyer-Zhao, Do-Young Byun, Juan-Carlos Algaba Marcos, Shu-Hao Chang, Chung-Chen Chen, Ryan Chilson, Yau-De Huang, Homin Jiang, Ching-Tang Liu, Pierre Martin-Cocher, Masanori Nakamura, George Nystrom, Peter Oshiro, Hung-Yi Pu, Philippe Raffin, Paul Shaw, Williams Snow, Ta-Shun Wei, T. K. Sridharan, Sheperd S. Doeleman, Roger Brissenden, Hideo Ogawa, Kimihiro Kimura, Yutaka Hasegawa, Timothy J. Norton, Alex Allardi, Jinchi Hao

    Ground-based and Airborne Telescopes VII   10700   2018.7

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    The Greenland Telescope completed its construction, so the commissioning phase has been started since December 2017. Single-dish commissioning has started from the optical pointing, which produced the rst pointing model, followed by the radio pointing and focusing using the Moon for both the 86 GHz and the 230 GHz receivers. After Venus started to rise from the horizon, the focus positions has been improved for both receivers. Once we started the line pointing using the SiO(2-1) maser line and the CO(2-1) line for the 86 GHz and the 230 GHz receivers, respectively, the pointing accuracy also improved, and the nal pointing accuracy turned to be around 3 ''-5 '' for both receivers. In parallel, VLBI commissioning has been performed, with checking the frequency accuracy and the phase stability for all the components that would be used for the VLBI observations. After all the checks, we successfully joined the dress rehearsals and actual observations of the 86 GHz and 230 GHz VLBI observations. The rst dress rehearsal data between GLT and ALMA were correlated, and successfully detected the rst fringe, which con rmed that the GLT commissioning was successfully performed.

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  • Mid-infrared Excess from the West Hot Spot of the Radio Galaxy Pictor A Unveiled by WISE Reviewed

    Naoki Isobe, Shoko Koyama, Motoki Kino, Takehiko Wada, Takao Nakagawa, Hideo Matsuhara, Kotaro Niinuma, Makoto Tashiro

    The Astrophysical Journal   850 ( 2 )   193 - 193   2017.12

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    Mid-infrared properties are reported of the west hot spot of the radio galaxy Pictor A with the Wide-field Infrared Survey Explorer (WISE). The mid-infrared counterpart to the hot spot, WISE J051926.26-454554.1, is listed in the AllWISE source catalog. The source was detected in all four of the WISE photometric bands. A comparison between the WISE and radio images reinforces the physical association of the WISE source to the hot spot. The WISE flux density of the source was carefully evaluated. A close investigation of the multi-wavelength synchrotron spectral energy distribution from the object reveals a mid-infrared excess at the wavelength of λ = μm with a statistical significance of over the simple power-law extrapolation from the synchrotron radio spectrum. The excess is reinforced by single and double cutoff power-law modeling of the radio-to-optical spectral energy distribution. The synchrotron cutoff frequency of the main and excess components was evaluated as 7.1 × 1044 Hz and 5.5 × 1013 Hz, respectively. From the cutoff frequency, the magnetic field of the emission region was constrained as a function of the region size. In order to interpret the excess component, an electron population different from the main one dominating the observed radio spectrum is necessary. The excess emission is proposed to originate in a substructure within the hot spot, in which the magnetic field is a factor of a few stronger than that in the minimum-energy condition. The relation of the mid-infrared excess to the X-ray emission is briefly discussed.

    DOI: 10.3847/1538-4357/aa94c9

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  • Pilot KaVA monitoring on the M 87 jet: Confirming the inner jet structure and superluminal motions at sub-pc scales Reviewed

    Kazuhiro Hada, Jong Ho Park, Motoki Kino, Kotaro Niinuma, Bong Won Sohn, Hyun Wook Ro, Taehyun Jung, Juan-Carlos Algaba, Guang-Yao Zhao, Sang-Sung Lee, Kazunori Akiyama, Sascha Trippe, Kiyoaki Wajima, Satoko Sawada-Satoh, Fumie Tazaki, Ilje Cho, Jeffrey Hodgson, Jeong Ae Lee, Yoshiaki Hagiwara, Mareki Honma, Shoko Koyama, Junghwan Oh, Taeseak Lee, Hyemin Yoo, Noriyuki Kawaguchi, Duk-Gyoo Roh, Se-Jin Oh, Jae-Hwan Yeom, Dong-Kyu Jung, Chungsik Oh, Hyo-Ryoung Kim, Ju-Yeon Hwang, Do-Young Byun, Se-Hyung Cho, Hyun-Goo Kim, Hideyuki Kobayashi, Katsunori M. Shibata

    Publications of the Astronomical Society of Japan   69 ( 4 )   2017.8

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    We report the initial results of our high-cadence monitoring program on the radio jet in the active galaxy M 87, obtained by the KVN and VERA Array (KaVA) at 22 GHz. This is a pilot study that preceded a larger KaVA–M 87 monitoring program, which is currently ongoing. The pilot monitoring was mostly performed every two to three weeks from 2013 December to 2014 June, at a recording rate of 1 Gbps, obtaining data for a total of ten epochs. We successfully obtained a sequence of good quality radio maps that revealed the rich structure of this jet from 1 mas to 20 mas, corresponding to physical scales (projected) of ∼0.1–2 pc (or ∼140–2800 Schwarzschild radii). We detected superluminal motions at these scales, together with a trend of gradual acceleration. The first evidence for such fast motions and acceleration near the jet base were obtained from recent VLBA studies at 43 GHz, and the fact that very similar kinematics are seen at a different frequency and time with a different instrument suggests that these properties are fundamental characteristics of this jet. This pilot program demonstrates that KaVA is a powerful VLBI array for studying the detailed structural evolution of the M 87 jet and also other relativistic jets.

    DOI: 10.1093/pasj/psx054

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  • Exploring the Magnetic Field Configuration in BL Lac Using GMVA Reviewed

    Bindu Rani, Thomas Krichbaum, Jeff Hodgson, Shoko Koyama, Anton Zensus, Lars Fuhramnn, Alan Marscher, Svetlana Jorstad

    Galaxies   4 ( 3 )   32 - 32   2016.9

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    DOI: 10.3390/galaxies4030032

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  • X-ray measurement of electron and magnetic-field energy densities in the west lobe of the giant radio galaxy 3C 236 Reviewed

    Naoki Isobe, Shoko Koyama

    Publications of the Astronomical Society of Japan   67 ( 4 )   77 - 77   2015.8

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    X-ray emission associated with the west lobe of the giant radio galaxy 3C 236 was investigated with the Suzaku observatory to evaluate the energetics in the lobe. After removing contamination from point-like X-ray sources detected with Chandra and subtracting the X-ray and non-X-ray backgrounds, the Suzaku spectrum from the lobe was reproduced by a power-law model with a photon index of $\\Gamma = 2.23-{-0.38-0.12}^{+0.44+0.14}$, where the first and second errors represent the statistical and systematic ones, respectively. Within the errors, the X-ray index was consistent with the radio synchrotron one, Γ&lt
    inf&gt
    R&lt
    /inf&gt
    = 1.74 ± 0.07, estimated in the 326-2695 MHz range. This agreement supports that the X-ray emission is attributed to the inverse-Compton radiation from the synchrotron electrons filling the lobe, where the cosmic microwave background photons are up-scattered. This result made 3C 236 the largest radio galaxy of which the lobe has ever been probed through the inverse-Compton X-ray photons. When the photon index was fixed at Γ&lt
    inf&gt
    R&lt
    /inf&gt
    , the X-ray flux density at 1 keV was measured as S&lt
    inf&gt
    X&lt
    /inf&gt
    = 12.3 ± 2.0 ± 1.9 nJy. A comparison of the X-ray flux to the radio one (S&lt
    inf&gt
    R&lt
    /inf&gt
    = 1.11 ± 0.02 Jy at 608.5 MHz) yields the energy densities of the electrons and magnetic field in the west lobe as $u-{\\rm e} = 3.9-{-0.7 -0.9}^{+0.6 +1.0} \\times 10^{-14}$ erg cm&lt
    sup&gt
    -3&lt
    /sup&gt
    and $u-{\\rm m} = 0.92-{-0.15 -0.35}^{+0.21 +0.52}\\times 10^{-14}$ erg cm&lt
    sup&gt
    -3&lt
    /sup&gt
    , respectively, indicating a mild electron dominance of $u-{\\rm e}/u-{\\rm m} = 4.2-{-1.3 -2.3}^{+1.6 +4.1}$. The latter corresponds to the magnetic field strength of $B = 0.48-{-0.04 -0.10}^{+0.05 +0.12}\\ \\mu$G. These are typical among the lobes of giant radio galaxies. A summary of the u&lt
    inf&gt
    e&lt
    /inf&gt
    -size relation for the inverse-Compton-detected radio galaxies implies that the west lobe of 3C 236 is still actively energized by its jet.

    DOI: 10.1093/pasj/psv046

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  • DISCOVERY OF A WANDERING RADIO JET BASE AFTER A LARGE X-RAY FLARE IN THE BLAZAR MARKARIAN 421 Reviewed

    K. Niinuma, M. Kino, A. Doi, K. Hada, H. Nagai, S. Koyama

    The Astrophysical Journal   807 ( 1 )   2015.7

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    We investigate the location of the radio jet bases ("radio cores") of blazars in radio images and their stationarity by means of dense very long baseline interferometry (VLBI) observations. In order to measure the position of a radio core, we conducted a 12 epoch astrometric observation of the blazar Markarian 421 with the VLBI Exploration of Radio Astrometry at 22 GHz immediately after a large X-ray flare, which occurred in the middle of 2011 September. For the first time,we find that the radio core is not stationary but rather changes its location toward 0.5 mas downstream. This angular scale corresponds to the de-projected length of a scale of 105 Schwarzschild radii (Rs) at the distance of Markarian 421. This radio-core wandering may be a new type of manifestation associated with the phenomena of large X-ray flares.

    DOI: 10.1088/2041-8205/807/1/L14

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  • VLBI observations of bright AGN jets with the KVN and VERA Array (KaVA): Evaluation of imaging capability Reviewed

    Kotaro Niinuma, Sang-Sung Lee, Motoki Kino, Bong Won Sohn, Kazunori Akiyama, Guang-Yao Zhao, Satoko Sawada-Satoh, Sascha Trippe, Kazuhiro Hada, Taehyun Jung, Yoshiaki Hagiwara, Richard Dodson, Shoko Koyama, Mareki Honma, Hiroshi Nagai, Aeree Chung, Akihiro Doi, Kenta Fujisawa, Myoung-Hee Han, Joeng-Sook Kim, Jeewon Lee, Jeong Ae Lee, Atsushi Miyazaki, Tomoaki Oyama, Kazuo Sorai, Kiyoaki Wajima, Jaehan Bae, Do-Young Byun, Se-Hyung Cho, Yoon Kyung Choi, Hyunsoo Chung, Moon-Hee Chung, Seog-Tae Han, Tomoya Hirota, Jung-Wook Hwang, Do-Heung Je, Takaaki Jike, Dong-Kyu Jung, Jin-Seung Jung, Ji-Hyun Kang, Jiman Kang, Yong-Woo Kang, Yukitoshi Kan-ya, Masahiro Kanaguchi, Noriyuki Kawaguchi, Bong Gyu Kim, Hyo Ryoung Kim, Hyun-Goo Kim, Jaeheon Kim, Jongsoo Kim, Kee-Tae Kim, Mikyoung Kim, Hideyuki Kobayashi, Yusuke Kono, Tomoharu Kurayama, Changhoon Lee, Jung-Won Lee, Sang Hyun Lee, Young Chol Minh, Naoko Matsumoto, Akiharu Nakagawa, Chung Sik Oh, Se-Jin Oh, Sun-Youp Park, Duk-Gyoo Roh, Tetsuo Sasao, Katsunori M. Shibata, Min-Gyu Song, Yoshiaki Tamura, Seog-Oh Wi, Jae-Hwan Yeom, Young Joo Yun

    Publications of the Astronomical Society of Japan   66 ( 6 )   103 - 103   2014.12

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    The Korean very-long-baseline interferometry (VLBI) network (KVN) and VLBI Exploration of Radio Astrometry (VERA) Array (KaVA) is the first international VLBI array dedicated to high-frequency (23-43GHz bands) observations in East Asia. Here, we report the first imaging observations of three bright active galactic nuclei (AGNs) known for their complex morphologies: 4C39.25, 3C273, and M87. This is one of the initial results of KaVA's early operation. Our KaVA images reveal extended outflows with complex substructures such as knots and limb brightening, in agreement with previous Very Long Baseline Array (VLBA) observations. Angular resolutions are better than 1.4 and 0.8 mas at 23 and 43GHz, respectively. KaVA achieves a high dynamic range of ∼1000, more than three times the value achieved by VERA. We conclude that KaVA is a powerful array with a great potential for the study of AGN outflows, at least comparable to the best existing radio interferometric arrays.

    DOI: 10.1093/pasj/psu104

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  • A STRONG RADIO BRIGHTENING AT THE JET BASE OF M 87 DURING THE ELEVATED VERY HIGH ENERGY GAMMA-RAY STATE IN 2012 Reviewed

    K. Hada, M. Giroletti, M. Kino, G. Giovannini, F. D'Ammando, C. C. Cheung, M. Beilicke, H. Nagai, A. Doi, K. Akiyama, M. Honma, K. Niinuma, C. Casadio, M. Orienti, H. Krawczynski, J. L. Gómez, S. Sawada-Satoh, S. Koyama, A. Cesarini, S. Nakahara, M. A. Gurwell

    The Astrophysical Journal   788 ( 2 )   165 - 165   2014.6

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    We report our intensive, high angular resolution radio monitoring observations of the jet in M 87 with the VLBI Exploration of Radio Astrometry (VERA) and the European VLBI Network (EVN) from 2011 February to 2012 October, together with contemporaneous high-energy (100 MeV &lt
    E &lt
    100 GeV) γ-ray light curves obtained by the Fermi Large Area Telescope. During this period (specifically from 2012 February to 2012 March), an elevated level of the M 87 flux is reported at very high energy (VHE
    E &gt
    100 GeV) γ rays by VERITAS. We detected a remarkable (up to ∼70%) increase of the radio flux density from the unresolved jet base (radio core) with VERA at 22 and 43 GHz coincident with the VHE activity. Meanwhile, we confirmed with EVN at 5 GHz that the peculiar knot, HST-1, which is an alternative favored γ-ray production site located at ≳120 pc from the nucleus, remained quiescent in terms of its flux density and structure. These results in the radio bands strongly suggest that the VHE γ-ray activity in 2012 originates in the jet base within 0.03 pc or 56 Schwarzschild radii (the VERA spatial resolution of 0.4 mas at 43 GHz) from the central supermassive black hole. We further conducted VERA astrometry for the M 87 core at six epochs during the flaring period, and detected core shifts between 22 and 43 GHz, a mean value of which is similar to that measured in the previous astrometric measurements. We also discovered a clear frequency-dependent evolution of the radio core flare at 43, 22, and 5 GHz
    the radio flux density increased more rapidly at higher frequencies with a larger amplitude, and the light curves clearly showed a time-lag between the peaks at 22 and 43 GHz, the value of which is constrained to be within ∼35-124 days. This indicates that a new radio-emitting component was created near the black hole in the period of the VHE event, and then propagated outward with progressively decreasing synchrotron opacity. By combining the obtained core shift and time-lag, we estimated an apparent speed of the newborn component propagating through the opaque region between the cores at 22 and 43 GHz. We derived a sub-luminal speed (less than ∼0.2c) for this component. This value is significantly slower than the super-luminal (∼1.1c) features that appeared from the core during the prominent VHE flaring event in 2008, suggesting that stronger VHE activity can be associated with the production of a higher Lorentz factor jet in M 87. © 2014. The American Astronomical Society. All rights reserved..

    DOI: 10.1088/0004-637x/788/2/165

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    Other Link: http://stacks.iop.org/0004-637X/788/i=2/a=165?key=crossref.16ebed5cf216fd30103363560c724407

  • Multifrequency VLBI Observations of the Broad Absorption Line Quasar J1020 4320: Recently Restarted Jet Activity? Reviewed

    Akihiro Doi, Yasuhiro Murata, Nanako Mochizuki, Hiroshi Takeuchi, Keiichi Asada, Takayuki J. Hayashi, Hiroshi Nagai, Katsunori M. Shibata, Tomoaki Oyama, Takaaki Jike, Kenta Fujisawa, Koichiro Sugiyama, Hideo Ogawa, Kimihiro Kimura, Mareki Honma, Hideyuki Kobayashi, Shoka Koyama

    Publications of the Astronomical Society of Japan   65 ( 3 )   57 - 57   2013.6

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    This paper reports on very-long-baseline interferometry observations of the radio-loud broad absorption line (BAL) quasar J1020+4320 at 1.7, 2.3, 6.7, and 8.4 GHz using the Japanese VLBI network (JVN) and European VLBI network (EVN). The radio morphology is compact with a size of -10 pc. The convex radio spectrum has been stable over the last decade; an observed peak frequency of 3.2 GHz is equivalent to 9.5 GHz in the rest frame, suggesting an age on the order of -100 years as a radio source, according to an observed correlation between the linear size and the peak frequency of compact steep spectrum (CSS) and giga-hertz peaked spectrum (GPS) radio sources. A low-frequency radio excess suggests a relic of past jet activity. J1020+4320 may be one of the quasars with recurrent and short-lived jet activity during a BAL-outflowing phase. © 2013. Astronomical Society of Japan.

    DOI: 10.1093/pasj/65.3.57

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  • VLBI Imagings of a Kilo-Parsec Knot in 3C 380 Reviewed

    Shoko Koyama, Motoki Kino, Hiroshi Nagai, Kazuhiro Hada, Seiji Kameno, Hideyuki Kobayashi

    Publications of the Astronomical Society of Japan   65 ( 2 )   29 - 29   2013.4

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Oxford University Press (OUP)  

    We investigated observational properties of a kilo-parsec scale knot in the radio-loud quasar 3C 380 by using two epoch archival data obtained by Very Long Baseline Interferometry (VLBI) at 5 GHz on 1998 July and 2001 April. We succeed to obtain the highest spatial resolution image of the bright knot K1 located at 732 mas, or ≥20 kpc deprojected, downstream from the nucleus three-times better than the previously obtained highest-resolution image by Papageorgiou et al. (2006, MNRAS, 373, 449). Our images reveal, with new clarity, an "inverted bow-shock" structure in K1 facing the nucleus
    its morphology resembles a conical shock wave. By comparing the two epoch images directly, we explored the kinematics of K1, and obtained the upper limit of the apparent velocity, 0.25 mas yr-1 or 9.8c of K1 for the first time. The upper limit of the apparent velocity is marginally smaller than superluminal motions seen in the core region. Further new epoch VLBI observations are necessary to measure the proper motion at K1. © 2013 Astronomical Society of Japan.

    DOI: 10.1093/pasj/65.2.29

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  • The GENJI Programme: Gamma-Ray Emitting Notable AGN Monitoring by Japanese VLBI Reviewed

    Hiroshi Nagai, Motoki Kino, Kotaro Niinuma, Kazunori Akiyama, Kazuhiro Hada, Shoko Koyama, Monica Orienti, Koichiro Hiura, Satoko Sawada-Satoh, Mareki Honma, Gabriele Giovannini, Marcello Giroletti, Katsunori Shibata, Kazuo Sorai

    Publications of the Astronomical Society of Japan   65 ( 2 )   24 - 24   2013.4

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    We introduce the gamma-ray emitting notable active galactic nucleus (AGN) monitoring by Japanese VLBI programme, which is the monitoring of gamma-ray bright AGNs with the VLBI Exploration of Radio Astrometry (VERA) array. This programme aims to conduct dense monitoring at 22 GHz toward the γ-ray emitting AGNs to investigate the time variation of the radio core and possible ejection of a new radio component, the motion of jets, and their relations with the emission at other wavelengths, especially at γ-rays. We are currently monitoring 8 notable γ-ray-emitting AGNs (DA55, 3C 84, M87, PKS 1510089, DA406, NRAO530, BL Lac, and 3C 454.3) about once every two weeks. This programme is promising for tracing the trend of radio time variation on shorter time scale than conventional VLBI monitoring programmes and is complementary to data of other programmes (e.g., MOJAVE
    Boston University Blazar Project). In particular, we successfully carried out quick follow-up observations after the GeV γ-ray flare in NRAO530 and 3C 454.3 reported by the Fermi Gamma-ray Space Telescope. Here, we present the initial results of morphology and light curves for the first 7-month operation. © 2013 Astronomical Society of Japan.

    DOI: 10.1093/pasj/65.2.24

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  • Radio and γ-ray follow-up of the exceptionally high-activity state of PKS 1510−089 in 2011 Reviewed

    M. Orienti, S. Koyama, F. D'Ammando, M. Giroletti, M. Kino, H. Nagai, T. Venturi, D. Dallacasa, G. Giovannini, E. Angelakis, L. Fuhrmann, T. Hovatta, W. Max-Moerbeck, F. K. Schinzel, K. Akiyama, K. Hada, M. Honma, K. Niinuma, D. Gasparrini, T. P. Krichbaum, I. Nestoras, A. C. S. Readhead, J. L. Richards, D. Riquelme, A. Sievers, H. Ungerechts, J. A. Zensus

    Monthly Notices of the Royal Astronomical Society   428 ( 3 )   2418 - 2429   2013.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Oxford University Press (OUP)  

    We investigate the radio and γ -ray variability of the flat spectrum radio quasar PKS 1510-089 in the time range between 2010 November and 2012 January. In this period the source showed an intense activity, with two major γ -ray flares detected in 2011 July and October. During the latter episode both the γ -ray and the radio flux density reached their historical peak. Multiwavelength analysis shows a rotation of about 380{ring operator} of the optical polarization angle close in time with the rapid and strong γ -ray flare in 2011 July. An enhancement of the optical emission and an increase of the fractional polarization both in the optical and in radio bands are observed about three weeks later, close in time with another γ -ray outburst. On the other hand, after 2011 September a huge radio outburst has been detected, first in the millimetre regime followed with some time delay at centimetre down to decimetre wavelengths. This radio flare is characterized by a rising and a decaying stage, in agreement with the formation of a shock and its evolution, as a consequence of expansion and radiative cooling. If the γ -ray flare observed in 2011 October is related to this radio outburst, then this strongly indicates that the region responsible for the γ -ray variability is not within the broad line, but a few parsecs downstream along the jet. © 2012 The Authors.

    DOI: 10.1093/mnras/sts201

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  • POSSIBLE DETECTION OF APPARENT SUPERLUMINAL INWARD MOTION IN MARKARIAN 421 AFTER THE GIANT X-RAY FLARE IN 2010 FEBRUARY Reviewed

    K. Niinuma, M. Kino, H. Nagai, N. Isobe, K. E. Gabanyi, K. Hada, S. Koyama, K. Asada, T. Oyama, K. Fujisawa

    The Astrophysical Journal   759 ( 2 )   84 - 84   2012.11

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing  

    We report on the very long baseline interferometry (VLBI) follow-up observations using the Japanese VLBI Network array at 22GHz for the largest X-ray flare of TeV blazar Mrk 421 that occurred in 2010 mid-February. The total of five epochs of observations were performed at intervals of about 20days between 2010 March 7 and May 31. No newborn component associated with the flare was seen directly in the total intensity images obtained by our multi-epoch VLBI observations. However, one jet component located at ∼1 mas northwest from the core was able to be identified, and its proper motion can be measured as -1.66 ± 0.46 mas yr-1, which corresponds to an apparent velocity of -3.48 ± 0.97c. Here, this negative velocity indicates that the jet component was apparently moving toward the core. As the most plausible explanation, we discuss that the apparent negative velocity was possibly caused by the ejection of a new component, which could not be resolved with our observations. In this case, the obtained Doppler factor of the new component is around 10-20, which is consistent with the ones typically estimated by model fittings of spectral energy distribution for this source. © 2012. The American Astronomical Society. All rights reserved..

    DOI: 10.1088/0004-637x/759/2/84

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  • EVIDENCE OF NON-THERMAL X-RAY EMISSION FROM RADIO LOBES OF CYGNUS A Reviewed

    Y. Yaji, M. S. Tashiro, N. Isobe, M. Kino, K. Asada, H. Nagai, S. Koyama, M. Kusunose

    The Astrophysical Journal   714 ( 1 )   37 - 44   2010.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing  

    Using deep Chandra Advanced CCD Imaging Spectrometer (ACIS) observation data for Cygnus A, we report evidence of non-thermal X-ray emission from radio lobes surrounded by a rich intracluster medium (ICM). The diffuse X-ray emission, which is associated with the eastern and western radio lobes, was observed in a 0.7-7 keV Chandra ACIS image. The lobe spectra are reproduced with not only a single-temperature Mekal model, such as that of the surrounding ICM component, but also an additional power-law (PL) model. The X-ray flux densities of PL components for the eastern and western lobes at 1 keV are derived as 77.7+28.9 -31.9 nJy and 52.4+42.9 -42.4 nJy, respectively, and the photon indices are 1.69 +0.07 -0.13 and 1.84+2.90 -0.12, respectively. The non-thermal component is considered to be produced via the inverse Compton (IC) process, as is often seen in the X-ray emission from radio lobes. From a re-analysis of radio observation data, the multiwavelength spectra strongly suggest that the seed photon source of the IC X-rays includes both cosmic microwave background radiation and synchrotron radiation from the lobes. The derived parameters indicate significant dominance of the electron energy density over the magnetic field energy density in the Cygnus A lobes under the rich ICM environment. © 2010. The American Astronomical Society. All rights reserved..

    DOI: 10.1088/0004-637x/714/1/37

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MISC

  • A balloon-borne very long baseline interferometry experiment in the stratosphere: Systems design and developments (vol 63, pg 779, 2019)

    Akihiro Doi, Yusuke Kono, Kimihiro Kimura, Satomi Nakahara, Tomoaki Oyama, Nozomi Okada, Yasutaka Satou, Kazuyoshi Yamashita, Naoko Matsumoto, Mitsuhisa Baba, Daisuke Yasuda, Shunsaku Suzuki, Yutaka Hasegawa, Mareki Honma, Hiroaki Tanaka, Kosei Ishimura, Yasuhiro Murata, Reiho Shimomukai, Tomohiro Tachi, Kazuya Saito, Naohiko Watanabe, Nobutaka Bando, Osamu Kameya, Yoshinori Yonekura, Mamoru Sekido, Yoshiyuki Inoue, Hiraku Sakamoto, Nozomu Kogiso, Yasuhiro Shoji, Hideo Ogawa, Kenta Fujisawa, Masanao Narita, Hiroshi Shibai, Hideyuki Fuke, Kenta Uehara, Shoko Koyama

    ADVANCES IN SPACE RESEARCH   66 ( 3 )   751 - 752   2020.8

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    Language:English   Publisher:ELSEVIER SCI LTD  

    DOI: 10.1016/j.asr.2020.04.044

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Awards

  • AAS Bruno Rossi Prize 2020 (EHT Collaboration)

    2020.1   American Astronomical Society  

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  • Einstein Medal 2020 (EHT Collaboration)

    2019.12   Albert Einstein Society  

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  • Smithsonian American Ingenuity Award 2019 (EHT Collaboration)

    2019.11   Smithsonian Institution  

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  • 2020 Breakthrough Prize in the Fundamental Physics (EHT Collaboration)

    2019.11   Breakthrough Foundation  

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  • 2019 Science and Technology Contribution Award (ASIAA Black Hole Research Group)

    2019.10   CTCI Foundation  

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  • NSF Diamond Achievement Award (EHT Collaboration)

    2019.5   National Science Foundation  

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Teaching Experience

  • 学問の扉 知と方法の最前線

    2022
    Institution name:新潟大学

  • データサイエンス実践 B

    2022
    Institution name:新潟大学

  • リフレクションデザイン I

    2022
    Institution name:新潟大学

  • データサイエンス概論

    2022
    Institution name:新潟大学

  • 宇宙物理学特論I

    2022
    Institution name:新潟大学

  • データサイエンス概説演習

    2021
    Institution name:新潟大学

  • 国際理解リテラシー

    2021
    Institution name:新潟大学

  • データサイエンス実践 C

    2021
    Institution name:新潟大学

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Media Coverage

  • Astronomers Reveal First Image of the Black Hole at the Heart of Our Galaxy Internet

    The Event Horizon Telescope  2022.5

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  • Astronomers Capture First Image of a Black Hole Internet

    The Event Horizon Telescope Collaboration 世界6箇所同時記者会見登壇(台北)  2019.4

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