Browsing by Author "Hada, Kazuhiro"

Now showing 1 - 10 of 10
  • Thumbnail Image
    Item
    Collimation of the Relativistic Jet in the Quasar 3C 273
    (IOP Publishing Ltd., 2022-11-01) Okino, Hiroki; Akiyama, Kazunori; Asada, Keiichi; Gómez, José L.; Hada, Kazuhiro; Honma, Mareki; Krichbaum, Thomas P.; Kino, Motoki; Nagai, Hiroshi; Bach, Uwe; Blackburn, Lindy; Bouman, Katherine L.; Chael, Andrew; Crew, Geoffrey B.; Doeleman, Sheperd S.; Fish, Vincent L.; Goddi, Ciriaco; Issaoun, Sara; Johnson, Michael D.; Jorstad, Svetlana; Koyama, Shoko; Lonsdale, Colin J.; Lu, Ru Sen; Martí-Vidal, Ivan; Matthews, Lynn D.; Mizuno, Yosuke; Moriyama, Kotaro; Nakamura, Masanori; Pu, Hung Yi; Ros, Eduardo; Savolainen, Tuomas; Tazaki, Fumie; Wagner, Jan; Wielgus, Maciek; Zensus, Anton; Department of Electronics and Nanoengineering; Metsähovi Radio Observatory; Anne Lähteenmäki Group; University of Tokyo; Massachusetts Institute of Technology; Academia Sinica Institute of Astronomy and Astrophysics; CSIC - Institute of Astrophysics of Andalusia; National Astronomical Observatory of Japan; Max Planck Institute for Radio Astronomy; Harvard University; California Institute of Technology; Princeton University; University of Cagliari; Boston University; Universidad de Valencia; National Taiwan Normal University
    The collimation of relativistic jets launched from the vicinity of supermassive black holes (SMBHs) at the centers of active galactic nuclei (AGNs) is one of the key questions to understand the nature of AGN jets. However, little is known about the detailed jet structure for AGN like quasars since very high angular resolutions are required to resolve these objects. We present very long baseline interferometry (VLBI) observations of the archetypical quasar 3C 273 at 86 GHz, performed with the Global Millimeter VLBI Array, for the first time including the Atacama Large Millimeter/submillimeter Array. Our observations achieve a high angular resolution down to ∼60 μas, resolving the innermost part of the jet ever on scales of ∼105 Schwarzschild radii. Our observations, including close-in-time High Sensitivity Array observations of 3C 273 at 15, 22, and 43 GHz, suggest that the inner jet collimates parabolically, while the outer jet expands conically, similar to jets from other nearby low-luminosity AGNs. We discovered the jet collimation break around 107 Schwarzschild radii, providing the first compelling evidence for structural transition in a quasar jet. The location of the collimation break for 3C 273 is farther downstream from the sphere of gravitational influence (SGI) from the central SMBH. With the results for other AGN jets, our results show that the end of the collimation zone in AGN jets is governed not only by the SGI of the SMBH but also by the more diverse properties of the central nuclei.
  • Thumbnail Image
    Item
    Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution
    (EDP SCIENCES, 2020-08-01) Kim, Jae Young; Krichbaum, Thomas P.; Broderick, Avery E.; Wielgus, Maciek; Blackburn, Lindy; Gómez, José L.; Johnson, Michael D.; Bouman, Katherine L.; Chael, Andrew; Akiyama, Kazunori; Jorstad, Svetlana; Marscher, Alan P.; Issaoun, Sara; Janssen, Michael; Chan, Chi Kwan; Savolainen, Tuomas; Pesce, Dominic W.; Özel, Feryal; Alberdi, Antxon; Alef, Walter; Asada, Keiichi; Azulay, Rebecca; Baczko, Anne Kathrin; Ball, David; Baloković, Mislav; Barrett, John; Bintley, Dan; Boland, Wilfred; Bower, Geoffrey C.; Bremer, Michael; Brinkerink, Christiaan D.; Brissenden, Roger; Britzen, Silke; Broguiere, Dominique; Bronzwaer, Thomas; Byun, Do Young; Carlstrom, John E.; Chatterjee, Shami; Chatterjee, Koushik; Chen, Ming Tang; Chen, Yongjun; Cho, Ilje; Christian, Pierre; Conway, John E.; Cordes, James M.; Crew, Geoffrey B.; Cui, Yuzhu; Davelaar, Jordy; De Laurentis, Mariafelicia; Deane, Roger; Dempsey, Jessica; Desvignes, Gregory; Dexter, Jason; Doeleman, Sheperd S.; Eatough, Ralph P.; Falcke, Heino; Fish, Vincent L.; Fomalont, Ed; Fraga-Encinas, Raquel; Friberg, Per; Fromm, Christian M.; Galison, Peter; Gammie, Charles F.; García, Roberto; Gentaz, Olivier; Georgiev, Boris; Goddi, Ciriaco; Gold, Roman; Gómez-Ruiz, Arturo I.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Hecht, Michael H.; Hesper, Ronald; Ho, Luis C.; Ho, Paul; Honma, Mareki; Huang, Chih Wei L.; Lei, Huang; Hughes, David H.; Ikeda, Shiro; Inoue, Makoto; James, David J.; Jannuzi, Buell T.; Jeter, Britton; Wu, Jiang; Jimenez-Rosales, Alejandra; Jung, Taehyun; Karami, Mansour; Karuppusamy, Ramesh; Kawashima, Tomohisa; Keating, Garrett K.; Kettenis, Mark; Kim, Junhan; Kim, Jongsoo; Kino, Motoki; Koay, Jun Yi; Koch, Patrick M.; Koyama, Shoko; Kramer, Michael; Kramer, Carsten; Kuo, Cheng Yu; Lauer, Tod R.; Lee, Sang Sung; Li, Yan Rong; Li, Zhiyuan; Lindqvist, Michael; Lico, Rocco; Kuo, Liu; Liuzzo, Elisabetta; Lo, Wen Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin; Lu, Ru Sen; Macdonald, Nicholas R.; Mao, Jirong; Markoff, Sera; Marrone, Daniel P.; Martí-Vidal, Iván; Matsushita, Satoki; Matthews, Lynn D.; Medeiros, Lia; Menten, Karl M.; Mizuno, Yosuke; Mizuno, Izumi; Moran, James M.; Moriyama, Kotaro; Moscibrodzka, Monika; Musoke, Gibwa; Müller, Cornelia; Nagai, Hiroshi; Nagar, Neil M.; Nakamura, Masanori; Narayan, Ramesh; Narayanan, Gopal; Natarajan, Iniyan; Neri, Roberto; Ni, Chunchong; Noutsos, Aristeidis; Okino, Hiroki; Olivares, Héctor; Ortiz-León, Gisela N.; Oyama, Tomoaki; Palumbo, Daniel C.M.; Park, Jongho; Patel, Nimesh; Pen, Ue Li; Piétu, Vincent; Plambeck, Richard; Popstefanija, Aleksandar; Porth, Oliver; Ben, Prather; Preciado-López, Jorge A.; Psaltis, Dimitrios; Pu, Hung Yi; Ramakrishnan, Venkatessh; Rao, Ramprasad; Rawlings, Mark G.; Raymond, Alexander W.; Rezzolla, Luciano; Ripperda, Bart; Roelofs, Freek; Rogers, Alan; Ros, Eduardo; Rose, Mel; Roshanineshat, Arash; Rottmann, Helge; Roy, Alan L.; Ruszczyk, Chet; Ryan, Benjamin R.; Rygl, Kazi L.J.; Sánchez, Salvador; Sánchez-Arguelles, David; Sasada, Mahito; Schloerb, F. Peter; Schuster, Karl Friedrich; Shao, Lijing; Shen, Zhiqiang; Small, Des; Sohn, Bong Won; Soohoo, Jason; Tazaki, Fumie; Tiede, Paul; Tilanus, Remo P.J.; Titus, Michael; Toma, Kenji; Torne, Pablo; Trent, Tyler; Traianou, Efthalia; Trippe, Sascha; Tsuda, Shuichiro; Van Bemmel, Ilse; Van Langevelde, Huib Jan; Van Rossum, Daniel R.; Jan, Wagner; Wardle, John; Ward-Thompson, Derek; Weintroub, Jonathan; Wex, Norbert; Wharton, Robert; Wong, George N.; Wu, Qingwen; Yoon, Doosoo; Young, André; Young, Ken; Younsi, Ziri; Feng, Yuan; Yuan, Ye Fei; Zensus, J. Anton; Zhao, Guangyao; Zhao, Shan Shan; Zhu, Ziyan; Algaba, Juan Carlos; Allardi, Alexander; Amestica, Rodrigo; Anczarski, Jadyn; Bach, Uwe; Baganoff, Frederick K.; Beaudoin, Christopher; Benson, Bradford A.; Berthold, Ryan; Blanchard, Jay M.; Blundell, Ray; Bustamente, Sandra; Cappallo, Roger; Castillo-Domínguez, Edgar; Chang, Chih Cheng; Chang, Shu Hao; Chang, Song Chu; Chen, Chung Chen; Chilson, Ryan; Chuter, Tim C.; Rosado, Rodrigo Córdova; Coulson, Iain M.; Crowley, Joseph; Derome, Mark; Dexter, Matthew; Dornbusch, Sven; Dudevoir, Kevin A.; Dzib, Sergio A.; Eckart, Andreas; Eckert, Chris; Erickson, Neal R.; Everett, Wendeline B.; Faber, Aaron; Farah, Joseph R.; Fath, Vernon; Folkers, Thomas W.; Forbes, David C.; Freund, Robert; Gale, David M.; Feng, Gao; Geertsema, Gertie; Graham, David A.; Greer, Christopher H.; Grosslein, Ronald; Gueth, Frédéric; Haggard, Daryl; Halverson, Nils W.; Han, Chih Chiang; Han, Kuo Chang; Hao, Jinchi; Hasegawa, Yutaka; Henning, Jason W.; Hernández-Gómez, Antonio; Herrero-Illana, Rubén; Heyminck, Stefan; Hirota, Akihiko; Hoge, James; Huang, Yau De; Violette Impellizzeri, C. M.; Jiang, Homin; John, David; Kamble, Atish; Keisler, Ryan; Kimura, Kimihiro; Kono, Yusuke; Kubo, Derek; Kuroda, John; Lacasse, Richard; Laing, Robert A.; Leitch, Erik M.; Li, Chao Te; Lin, Lupin C.C.; Liu, Ching Tang; Liu, Kuan Yu; Lu, Li Ming; Marson, Ralph G.; Martin-Cocher, Pierre L.; Massingill, Kyle D.; Matulonis, Callie; Mccoll, Martin P.; Mcwhirter, Stephen R.; Messias, Hugo; Zheng, Meyer Zhao; Michalik, Daniel; Montaña, Alfredo; Montgomerie, William; Mora-Klein, Matias; Muders, Dirk; Nadolski, Andrew; Navarro, Santiago; Neilsen, Joseph; Nguyen, Chi H.; Nishioka, Hiroaki; Norton, Timothy; Nowak, Michael A.; Nystrom, George; Ogawa, Hideo; Oshiro, Peter; Parsons, Harriet; Juan, Peñalver; Phillips, Neil M.; Poirier, Michael; Pradel, Nicolas; Primiani, Rurik A.; Raffin, Philippe A.; Rahlin, Alexandra S.; Reiland, George; Risacher, Christopher; Ruiz, Ignacio; Sáez-Madaín, Alejandro F.; Sassella, Remi; Schellart, Pim; Shaw, Paul; Silva, Kevin M.; Shiokawa, Hotaka; Smith, David R.; Snow, William; Souccar, Kamal; Sousa, Don; Sridharan, Tirupati K.; Srinivasan, Ranjani; Stahm, William; Stark, Antony A.; Story, Kyle; Timmer, Sjoerd T.; Vertatschitsch, Laura; Walther, Craig; Wei, Ta Shun; Whitehorn, Nathan; Whitney, Alan R.; Woody, David P.; Wouterloot, Jan G.A.; Wright, Melvin; Yamaguchi, Paul; Yu, Chen Yu; Zeballos, Milagros; Zhang, Shuo; Ziurys, Lucy; Department of Electronics and Nanoengineering; Metsähovi Radio Observatory; Anne Lähteenmäki Group; Max Planck Institute for Radio Astronomy; Perimeter Institute for Theoretical Physics; Harvard University; CSIC; Princeton University; Boston University; Radboud University Nijmegen; University of Arizona; Academia Sinica Institute of Astronomy and Astrophysics; Massachusetts Institute of Technology; East Asian Observatory; Nederlandse Onderzoekschool voor Astronomie; Academia Sinica; Institut de Radioastronomie Millimétrique; Korea Astronomy and Space Science Institute; University of Chicago; Cornell University; University of Amsterdam; CAS - Shanghai Astronomical Observatory; Chalmers University of Technology; National Astronomical Observatory of Japan; University of Naples Federico II; University of Pretoria; Centre National de la Recherche Scientifique (CNRS); University of Colorado Boulder; National Radio Astronomy Observatory; Goethe University Frankfurt; University of Illinois at Urbana-Champaign; University of Waterloo; Instituto Nacional de Astrofísica, Óptica y Electrónica; University of Groningen; Peking University; Max Planck Institute for Extraterrestrial Physics; Joint Institute for VLBI in Europe; California Institute of Technology; National Sun Yat-sen University; National Optical Astronomy Observatory; CAS - Institute of High Energy Physics; Nanjing University; INAF - Istituto di Radioastronomia; Instituto de Radioastronomía y Astrofísica; CAS - National Astronomical Observatories; Universidad de Valencia; Universidad de Concepción; University of Massachusetts; Rhodes University; University of California, Berkeley; Los Alamos National Laboratory; Instituto de Radioastronomía Milimétrica; Tohoku University; Seoul National University; Brandeis University; University of Central Lancashire; Huazhong University of Science and Technology; University of Science and Technology of China; University of Vermont; Villanova University; United States Department of Energy; Western University; Royal Netherlands Meteorological Institute; McGill University; Osaka Prefecture University; European Southern Observatory Santiago; University of Manchester; Rochester Institute of Technology; Washington University St. Louis; Systems and Technology Research; Georgia Institute of Technology; Stanford University; University of California, Los Angeles
    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 1.3mm (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-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, at an angular resolution of ∼20 μas (at a redshift of z = 0:536 this corresponds to ∼0:13 pc ∼ 1700 Schwarzschild radii with a black hole mass MBH = 8 × 108 M⊙). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation.We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across diffierent 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 c and ∼20 c (∼1:3 and ∼1:7 μas day-1, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3mm core and the outer jet. The intrinsic brightness temperature of the jet components are ≤1010 K, a magnitude or more lower than typical values seen at ≥7mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C 279 becomes optically thin at short (mm) wavelengths.
  • Thumbnail Image
    Item
    Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes
    (Institute of Physics Publishing, 2023-11-01) Roelofs, Freek; Johnson, Michael D.; Chael, Andrew; Janssen, Michael; Wielgus, Maciek; Broderick, Avery E.; Akiyama, Kazunori; Alberdi, Antxon; Alef, Walter; Algaba, Juan Carlos; Anantua, Richard; Asada, Keiichi; Azulay, Rebecca; Bach, Uwe; Baczko, Anne Kathrin; Ball, David; Baloković, Mislav; Barrett, John; Bauböck, Michi; Benson, Bradford A.; Bintley, Dan; Blackburn, Lindy; Blundell, Raymond; Bouman, Katherine L.; Bower, Geoffrey C.; Boyce, Hope; Bremer, Michael; Brinkerink, Christiaan D.; Brissenden, Roger; Britzen, Silke; Broguiere, Dominique; Bronzwaer, Thomas; Bustamante, Sandra; Byun, Do Young; Carlstrom, John E.; Ceccobello, Chiara; Chan, Chi Kwan; Chang, Dominic O.; Chatterjee, Koushik; Chatterjee, Shami; Chen, Ming Tang; Chen, Yongjun; Cheng, Xiaopeng; Cho, Ilje; Christian, Pierre; Conroy, Nicholas S.; Conway, John E.; Cordes, James M.; Crawford, Thomas M.; Crew, Geoffrey B.; Cruz-Osorio, Alejandro; Cui, Yuzhu; Dahale, Rohan; Davelaar, Jordy; De Laurentis, Mariafelicia; Deane, Roger; Dempsey, Jessica; Desvignes, Gregory; Dexter, Jason; Dhruv, Vedant; Doeleman, Sheperd S.; Dougal, Sean; Dzib, Sergio A.; Eatough, Ralph P.; Emami, Razieh; Falcke, Heino; Farah, Joseph; Fish, Vincent L.; Fomalont, Ed; Ford, H. Alyson; Foschi, Marianna; Fraga-Encinas, Raquel; Freeman, William T.; Friberg, Per; Fromm, Christian M.; Fuentes, Antonio; Galison, Peter; Gammie, Charles F.; García, Roberto; Gentaz, Olivier; Georgiev, Boris; Goddi, Ciriaco; Gold, Roman; Gómez-Ruiz, Arturo I.; Gómez, José L.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Haggard, Daryl; Haworth, Kari; Hecht, Michael H.; Hesper, Ronald; Heumann, Dirk; Ho, Luis C.; Ho, Paul; Honma, Mareki; Huang, Chih Wei L.; Huang, Lei; Hughes, David H.; Ikeda, Shiro; Impellizzeri, C. M.Violette; Inoue, Makoto; Issaoun, Sara; James, David J.; Jannuzi, Buell T.; Jeter, Britton; Jiang, Wu; Jiménez-Rosales, Alejandra; Jorstad, Svetlana; Joshi, Abhishek V.; Jung, Taehyun; Karami, Mansour; Karuppusamy, Ramesh; Kawashima, Tomohisa; Keating, Garrett K.; Kettenis, Mark; Kim, Dong Jin; Kim, Jae Young; Kim, Jongsoo; Kim, Junhan; Kino, Motoki; Koay, Jun Yi; Kocherlakota, Prashant; Kofuji, Yutaro; Koch, Patrick M.; Koyama, Shoko; Kramer, Carsten; Kramer, Joana A.; Kramer, Michael; Krichbaum, Thomas P.; Kuo, Cheng Yu; La Bella, Noemi; Lauer, Tod R.; Lee, Daeyoung; Lee, Sang Sung; Leung, Po Kin; Levis, Aviad; Li, Zhiyuan; Lico, Rocco; Lindahl, Greg; Lindqvist, Michael; Lisakov, Mikhail; Liu, Jun; Liu, Kuo; Liuzzo, Elisabetta; Lo, Wen Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin J.; Lowitz, Amy E.; Lu, Ru Sen; MacDonald, Nicholas R.; Mao, Jirong; Marchili, Nicola; Markoff, Sera; Marrone, Daniel P.; Marscher, Alan P.; Martí-Vidal, Iván; Matsushita, Satoki; Matthews, Lynn D.; Medeiros, Lia; Menten, Karl M.; Michalik, Daniel; Mizuno, Izumi; Mizuno, Yosuke; Moran, James M.; Moriyama, Kotaro; Moscibrodzka, Monika; Mulaudzi, Wanga; Müller, Cornelia; Müller, Hendrik; Mus, Alejandro; Musoke, Gibwa; Myserlis, Ioannis; Nadolski, Andrew; Nagai, Hiroshi; Nagar, Neil M.; Nakamura, Masanori; Narayan, Ramesh; Narayanan, Gopal; Natarajan, Iniyan; Nathanail, Antonios; Fuentes, Santiago Navarro; Neilsen, Joey; Neri, Roberto; Ni, Chunchong; Noutsos, Aristeidis; Nowak, Michael A.; Oh, Junghwan; Okino, Hiroki; Olivares, Héctor; Ortiz-León, Gisela N.; Oyama, Tomoaki; Özel, Feryal; Palumbo, Daniel C.M.; Paraschos, Georgios Filippos; Park, Jongho; Parsons, Harriet; Patel, Nimesh; Pen, Ue Li; Pesce, Dominic W.; Piétu, Vincent; Plambeck, Richard; PopStefanija, Aleksandar; Porth, Oliver; Pötzl, Felix M.; Prather, Ben; Preciado-López, Jorge A.; Psaltis, Dimitrios; Pu, Hung Yi; Ramakrishnan, Venkatessh; Rao, Ramprasad; Rawlings, Mark G.; Raymond, Alexander W.; Rezzolla, Luciano; Ricarte, Angelo; Ripperda, Bart; Rogers, Alan; Romero-Cañizales, Cristina; Ros, Eduardo; Roshanineshat, Arash; Rottmann, Helge; Roy, Alan L.; Ruiz, Ignacio; Ruszczyk, Chet; Rygl, Kazi L.J.; Sánchez, Salvador; Sánchez-Argüelles, David; Sánchez-Portal, Miguel; Sasada, Mahito; Satapathy, Kaushik; Savolainen, Tuomas; Schloerb, F. Peter; Schonfeld, Jonathan; Schuster, Karl Friedrich; Shao, Lijing; Shen, Zhiqiang; Small, Des; Sohn, Bong Won; SooHoo, Jason; Sosapanta Salas, León David; Souccar, Kamal; Sun, He; Tazaki, Fumie; Tetarenko, Alexandra J.; Tiede, Paul; Tilanus, Remo P.J.; Titus, Michael; Torne, Pablo; Toscano, Teresa; Traianou, Efthalia; Trent, Tyler; Trippe, Sascha; Turk, Matthew; van Bemmel, Ilse; van Langevelde, Huib Jan; van Rossum, Daniel R.; Vos, Jesse; Wagner, Jan; Ward-Thompson, Derek; Wardle, John; Washington, Jasmin E.; Weintroub, Jonathan; Wharton, Robert; Wiik, Kaj; Witzel, Gunther; Wondrak, Michael F.; Wong, George N.; Wu, Qingwen; Yadlapalli, Nitika; Yamaguchi, Paul; Yfantis, Aristomenis; Yoon, Doosoo; Young, André; Young, Ken; Younsi, Ziri; Yu, Wei; Yuan, Feng; Yuan, Ye Fei; Zensus, J. Anton; Zhang, Shuo; Zhao, Guang Yao; Zhao, Shan Shan; Metsähovi Radio Observatory; Department of Electronics and Nanoengineering; Anne Lähteenmäki Group; Harvard University; Princeton University; Max Planck Institute for Radio Astronomy; Perimeter Institute for Theoretical Physics; CSIC - Institute of Astrophysics of Andalusia; University of Malaya; Academia Sinica Institute of Astronomy and Astrophysics; University of Arizona; Yale University; Massachusetts Institute of Technology; University of Illinois at Urbana-Champaign; Fermi National Accelerator Laboratory; East Asian Observatory; California Institute of Technology; Radboud University Nijmegen; University of Chicago; Chalmers University of Technology; National Astronomical Observatory of Japan; Universidad de Valencia
    The Event Horizon Telescope (EHT) is a millimeter very long baseline interferometry (VLBI) array that has imaged the apparent shadows of the supermassive black holes M87* and Sagittarius A*. Polarimetric data from these observations contain a wealth of information on the black hole and accretion flow properties. In this work, we develop polarimetric geometric modeling methods for mm-VLBI data, focusing on approaches that fit data products with differing degrees of invariance to broad classes of calibration errors. We establish a fitting procedure using a polarimetric “m-ring” model to approximate the image structure near a black hole. By fitting this model to synthetic EHT data from general relativistic magnetohydrodynamic models, we show that the linear and circular polarization structure can be successfully approximated with relatively few model parameters. We then fit this model to EHT observations of M87* taken in 2017. In total intensity and linear polarization, the m-ring fits are consistent with previous results from imaging methods. In circular polarization, the m-ring fits indicate the presence of event-horizon-scale circular polarization structure, with a persistent dipolar asymmetry and orientation across several days. The same structure was recovered independently of observing band, used data products, and model assumptions. Despite this broad agreement, imaging methods do not produce similarly consistent results. Our circular polarization results, which imposed additional assumptions on the source structure, should thus be interpreted with some caution. Polarimetric geometric modeling provides a useful and powerful method to constrain the properties of horizon-scale polarized emission, particularly for sparse arrays like the EHT.
  • Thumbnail Image
    Item
    The Polarized Image of a Synchrotron-emitting Ring of Gas Orbiting a Black Hole
    (IOP Publishing Ltd., 2021-05-01) Narayan, Ramesh; Palumbo, Daniel C.M.; Johnson, Michael D.; Gelles, Zachary; Himwich, Elizabeth; Chang, Dominic O.; Ricarte, Angelo; Dexter, Jason; Gammie, Charles F.; Chael, Andrew A.; Akiyama, Kazunori; Alberdi, Antxon; Alef, Walter; Algaba, Juan Carlos; Anantua, Richard; Asada, Keiichi; Azulay, Rebecca; Baczko, Anne Kathrin; Ball, David; Baloković, Mislav; Barrett, John; Benson, Bradford A.; Bintley, Dan; Blackburn, Lindy; Blundell, Raymond; Boland, Wilfred; Bouman, Katherine L.; Bower, Geoffrey C.; Boyce, Hope; Bremer, Michael; Brinkerink, Christiaan D.; Brissenden, Roger; Britzen, Silke; Broderick, Avery E.; Broguiere, Dominique; Bronzwaer, Thomas; Byun, Do Young; Carlstrom, John E.; Chan, Chi Kwan; Chatterjee, Shami; Chatterjee, Koushik; Chen, Ming Tang; Chen, Yongjun; Chesler, Paul M.; Cho, Ilje; Christian, Pierre; Conway, John E.; Cordes, James M.; Crawford, Thomas M.; Crew, Geoffrey B.; Cruz-Osorio, Alejandro; Cui, Yuzhu; Davelaar, Jordy; De Laurentis, Mariafelicia; Deane, Roger; Dempsey, Jessica; Desvignes, Gregory; Doeleman, Sheperd S.; Eatough, Ralph P.; Falcke, Heino; Farah, Joseph; Fish, Vincent L.; Fomalont, Ed; Ford, H. Alyson; Fraga-Encinas, Raquel; Friberg, Per; Fromm, Christian M.; Fuentes, Antonio; Galison, Peter; García, Roberto; Gentaz, Olivier; Georgiev, Boris; Goddi, Ciriaco; Gold, Roman; Gómez, José L.; Gómez-Ruiz, Arturo I.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Haggard, Daryl; Hecht, Michael H.; Hesper, Ronald; Ho, Luis C.; Ho, Paul; Honma, Mareki; Huang, Chih Wei L.; Huang, Lei; Hughes, David H.; Ikeda, Shiro; Inoue, Makoto; Issaoun, Sara; James, David J.; Jannuzi, Buell T.; Janssen, Michael; Jeter, Britton; Jiang, Wu; Jimenez-Rosales, Alejandra; Jorstad, Svetlana; Jung, Taehyun; Karami, Mansour; Karuppusamy, Ramesh; Kawashima, Tomohisa; Keating, Garrett K.; Kettenis, Mark; Kim, Dong Jin; Kim, Jae Young; Kim, Jongsoo; Kim, Junhan; Kino, Motoki; Koay, Jun Yi; Kofuji, Yutaro; Koch, Patrick M.; Koyama, Shoko; Kramer, Michael; Kramer, Carsten; Krichbaum, Thomas P.; Kuo, Cheng Yu; Lauer, Tod R.; Lee, Sang Sung; Levis, Aviad; Li, Yan Rong; Li, Zhiyuan; Lindqvist, Michael; Lico, Rocco; Lindahl, Greg; Liu, Jun; Liu, Kuo; Liuzzo, Elisabetta; Lo, Wen Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin; Lu, Ru Sen; Macdonald, Nicholas R.; Mao, Jirong; Marchili, Nicola; Markoff, Sera; Marrone, Daniel P.; Marscher, Alan P.; Martí-Vidal, Iván; Matsushita, Satoki; Matthews, Lynn D.; Medeiros, Lia; Menten, Karl M.; Mizuno, Izumi; Mizuno, Yosuke; Moran, James M.; Moriyama, Kotaro; Moscibrodzka, Monika; Müller, Cornelia; Musoke, Gibwa; Mejías, Alejandro Mus; Nagai, Hiroshi; Nagar, Neil M.; Nakamura, Masanori; Natarajan, Iniyan; Nathanail, Antonios; Neilsen, Joey; Neri, Roberto; Ni, Chunchong; Noutsos, Aristeidis; Nowak, Michael A.; Okino, Hiroki; Olivares, Héctor; Ortiz-León, Gisela N.; Oyama, Tomoaki; Özel, Feryal; Park, Jongho; Patel, Nimesh; Pen, Ue Li; Pesce, Dominic W.; Piétu, Vincent; Plambeck, Richard; Popstefanija, Aleksandar; Porth, Oliver; Pötzl, Felix M.; Prather, Ben; Preciado-López, Jorge A.; Psaltis, Dimitrios; Pu, Hung Yi; Ramakrishnan, Venkatessh; Rao, Ramprasad; Rawlings, Mark G.; Raymond, Alexander W.; Rezzolla, Luciano; Ripperda, Bart; Roelofs, Freek; Rogers, Alan; Ros, Eduardo; Rose, Mel; Roshanineshat, Arash; Rottmann, Helge; Roy, Alan L.; Ruszczyk, Chet; Rygl, Kazi L.J.; Sánchez, Salvador; Sánchez-Arguelles, David; Sasada, Mahito; Savolainen, Tuomas; Schloerb, F. Peter; Schuster, Karl Friedrich; Shao, Lijing; Shen, Zhiqiang; Small, Des; Sohn, Bong Won; Soohoo, Jason; Sun, He; Tazaki, Fumie; Tetarenko, Alexandra J.; Tiede, Paul; Tilanus, Remo P.J.; Titus, Michael; Toma, Kenji; Torne, Pablo; Trent, Tyler; Traianou, Efthalia; Trippe, Sascha; Van Bemmel, Ilse; Van Langevelde, Huib Jan; Van Rossum, Daniel R.; Wagner, Jan; Ward-Thompson, Derek; Wardle, John; Weintroub, Jonathan; Wex, Norbert; Wharton, Robert; Wielgus, Maciek; Wong, George N.; Wu, Qingwen; Yoon, Doosoo; Young, André; Young, Ken; Younsi, Ziri; Yuan, Feng; Yuan, Ye Fei; Zensus, J. Anton; Zhao, Guang Yao; Zhao, Shan Shan; Metsähovi Radio Observatory; Department of Electronics and Nanoengineering; Anne Lähteenmäki Group; Harvard University; University of Colorado Boulder; University of Illinois at Urbana-Champaign; Princeton University; CSIC; Max Planck Institute for Radio Astronomy; University of Malaya; Academia Sinica Institute of Astronomy and Astrophysics; University of Arizona; Massachusetts Institute of Technology; United States Department of Energy; East Asian Observatory; Nederlandse Onderzoekschool voor Astronomie; McGill University; Institut de Radioastronomie Millimétrique; Radboud University Nijmegen; Perimeter Institute for Theoretical Physics; Korea Astronomy and Space Science Institute; University of Chicago; Cornell Center for Astrophysics and Planetary Science; University of Amsterdam; CAS - Shanghai Astronomical Observatory; Fairfield University; Chalmers University of Technology; Goethe University Frankfurt; National Astronomical Observatory of Japan; University of the Witwatersrand, Johannesburg; Observatoire de Paris; National Radio Astronomy Observatory; University of Waterloo; Instituto Nacional de Astrofísica, Óptica y Electrónica; University of Groningen; Peking University; Boston University; University of Tokyo; Joint Institute for VLBI in Europe; National Optical Astronomy Observatory; California Institute of Technology; CAS - Institute of High Energy Physics; Nanjing University; INAF - Istituto di Radioastronomia; Instituto de Radioastronomía y Astrofísica; CAS - National Astronomical Observatories; Universidad de Valencia; Universidad de Concepción; Villanova University; Washington University St. Louis; University of California, Berkeley; University of Massachusetts; Simons Foundation; Instituto de Radioastronomía Milimétrica; Tohoku University; Seoul National University; University of Central Lancashire; Brandeis University; Huazhong University of Science and Technology; University of Science and Technology of China
    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.
  • Thumbnail Image
    Item
    RadioAstron Space VLBI Imaging of the Jet in M87. I. Detection of High Brightness Temperature at 22 GHz
    (Institute of Physics Publishing, 2023-07-01) Kim, Jae Young; Savolainen, Tuomas; Voitsik, Petr; Kravchenko, Evgeniya V.; Lisakov, Mikhail M.; Kovalev, Yuri Y.; Müller, Hendrik; Lobanov, Andrei P.; Sokolovsky, Kirill V.; Bruni, Gabriele; Edwards, Philip G.; Reynolds, Cormac; Bach, Uwe; Gurvits, Leonid I.; Krichbaum, Thomas P.; Hada, Kazuhiro; Giroletti, Marcello; Orienti, Monica; Anderson, James M.; Lee, Sang Sung; Sohn, Bong Won; Zensus, J. Anton; Department of Electronics and Nanoengineering; Metsähovi Radio Observatory; Anne Lähteenmäki Group; Kyungpook National University; RAS - P.N. Lebedev Physics Institute; Max Planck Institute for Radio Astronomy; University of Illinois at Urbana-Champaign; National Institute for Astrophysics (INAF); Commonwealth Scientific and Industrial Research Organisation (CSIRO); Joint Institute for VLBI in Europe; National Astronomical Observatory of Japan; INAF - Istituto di Radioastronomia; Leibniz Institute for Agricultural Engineering and Bioeconomy; Korea Astronomy and Space Science Institute
    We present results from the first 22 GHz space very long baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part of the Nearby AGN Key Science Program, the source was observed in 2014 February at 22 GHz with 21 ground stations, reaching projected (u, v) spacings up to ∼11 Gλ. The imaging experiment was complemented by snapshot RadioAstron data of M87 obtained during 2013-2016 from the AGN Survey Key Science Program. Their longest baselines extend up to ∼25 Gλ. For all of these measurements, fringes are detected only up to ∼2.8 Earth diameter or ∼3 Gλ baseline lengths, resulting in a new image with angular resolution of ∼150 μas or ∼20 Schwarzschild radii spatial resolution. The new image not only shows edge-brightened jet and counterjet structures down to submilliarcsecond scales but also clearly resolves the VLBI core region. While the overall size of the core is comparable to those reported in the literature, the ground-space fringe detection and slightly superresolved RadioAstron image suggest the presence of substructures in the nucleus, whose minimum brightness temperature exceeds T B , min ∼ 10 12 K. It is challenging to explain the origin of this record-high T B , min value for M87 by pure Doppler boosting effect with a simple conical jet geometry and known jet speed. Therefore, this can be evidence for more extreme Doppler boosting due to a blazar-like small jet viewing angle or highly efficient particle acceleration processes occurring already at the base of the outflow.
  • Thumbnail Image
    Item
    A ring-like accretion structure in M87 connecting its black hole and jet
    (Nature Publishing Group, 2023-04-01) Lu, Ru Sen; Asada, Keiichi; Krichbaum, Thomas P.; Park, Jongho; Tazaki, Fumie; Pu, Hung Yi; Nakamura, Masanori; Lobanov, Andrei; Hada, Kazuhiro; Akiyama, Kazunori; Kim, Jae Young; Marti-Vidal, Ivan; Gómez, José L.; Kawashima, Tomohisa; Yuan, Feng; Ros, Eduardo; Alef, Walter; Britzen, Silke; Bremer, Michael; Broderick, Avery E.; Doi, Akihiro; Giovannini, Gabriele; Giroletti, Marcello; Ho, Paul T.P.; Honma, Mareki; Hughes, David H.; Inoue, Makoto; Jiang, Wu; Kino, Motoki; Koyama, Shoko; Lindqvist, Michael; Liu, Jun; Marscher, Alan P.; Matsushita, Satoki; Nagai, Hiroshi; Rottmann, Helge; Savolainen, Tuomas; Schuster, Karl Friedrich; Shen, Zhi Qiang; de Vicente, Pablo; Walker, R. Craig; Yang, Hai; Zensus, J. Anton; Algaba, Juan Carlos; Allardi, Alexander; Bach, Uwe; Berthold, Ryan; Bintley, Dan; Byun, Do Young; Casadio, Carolina; Chang, Shu Hao; Chang, Chih Cheng; Chang, Song Chu; Chen, Chung Chen; Chen, Ming Tang; Chilson, Ryan; Chuter, Tim C.; Conway, John; Crew, Geoffrey B.; Dempsey, Jessica T.; Dornbusch, Sven; Faber, Aaron; Friberg, Per; García, Javier González; Garrido, Miguel Gómez; Han, Chih Chiang; Han, Kuo Chang; Hasegawa, Yutaka; Herrero-Illana, Ruben; Huang, Yau De; Huang, Chih Wei L.; Impellizzeri, Violette; Jiang, Homin; Jinchi, Hao; Jung, Taehyun; Kallunki, Juha; Kirves, Petri; Kimura, Kimihiro; Koay, Jun Yi; Koch, Patrick M.; Kramer, Carsten; Kraus, Alex; Kubo, Derek; Kuo, Cheng Yu; Li, Chao Te; Lin, Lupin Chun Che; Liu, Ching Tang; Liu, Kuan Yu; Lo, Wen Ping; Lu, Li Ming; MacDonald, Nicholas; Martin-Cocher, Pierre; Messias, Hugo; Meyer-Zhao, Zheng; Minter, Anthony; Nair, Dhanya G.; Nishioka, Hiroaki; Norton, Timothy J.; Nystrom, George; Ogawa, Hideo; Oshiro, Peter; Patel, Nimesh A.; Pen, Ue Li; Pidopryhora, Yurii; Pradel, Nicolas; Raffin, Philippe A.; Rao, Ramprasad; Ruiz, Ignacio; Sanchez, Salvador; Shaw, Paul; Snow, William; Sridharan, T. K.; Srinivasan, Ranjani; Tercero, Belén; Torne, Pablo; Traianou, Efthalia; Wagner, Jan; Walther, Craig; Wei, Ta Shun; Yang, Jun; Yu, Chen Yu; Department of Electronics and Nanoengineering; Metsähovi Radio Observatory; Anne Lähteenmäki Group; CAS - Shanghai Astronomical Observatory; Academia Sinica Institute of Astronomy and Astrophysics; Max Planck Institute for Radio Astronomy; National Astronomical Observatory of Japan; Harvard University; Universidad de Valencia; CSIC - Institute of Astrophysics of Andalusia; University of Tokyo; Institut de Radioastronomie Millimétrique; University of Waterloo; Institute of Space and Astronautical Science; Universitá di Bologna; INAF - Istituto di Radioastronomia; Instituto Nacional de Astrofísica, Óptica y Electrónica; Kogakuin University; Chalmers University of Technology; Boston University; Graduate University for Advanced Studies (SOKENDAI); National Radio Astronomy Observatory; University of Malaya; University of Vermont; East Asian Observatory; Korea Astronomy and Space Science Institute; Foundation for Research and Technology - Hellas; National Chung-Shan Institute of Science and Technology; Massachusetts Institute of Technology; Western University; European Southern Observatory Santiago; Leiden University; Metsähovi Radio Observatory; Japan Aerospace Exploration Agency (JAXA); National Sun Yat-sen University; National Cheng Kung University; Universidad de Concepción; IGN Yebes
    The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation1,2. Event Horizon Telescope observations of M87 in 2017, at a wavelength of 1.3 mm, revealed a ring-like structure, which was interpreted as gravitationally lensed emission around a central black hole3. Here we report images of M87 obtained in 2018, at a wavelength of 3.5 mm, showing that the compact radio core is spatially resolved. High-resolution imaging shows a ring-like structure of [Formula: see text] Schwarzschild radii in diameter, approximately 50% larger than that seen at 1.3 mm. The outer edge at 3.5 mm is also larger than that at 1.3 mm. This larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects, in addition to the gravitationally lensed ring-like emission. The images show that the edge-brightened jet connects to the accretion flow of the black hole. Close to the black hole, the emission profile of the jet-launching region is wider than the expected profile of a black-hole-driven jet, suggesting the possible presence of a wind associated with the accretion flow.
  • Thumbnail Image
    Item
    A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set
    (Institute of Physics Publishing, 2023-12-01) Torne, Pablo; Liu, Kuo; Eatough, Ralph P.; Wongphechauxsorn, Jompoj; Cordes, James M.; Desvignes, Gregory; De Laurentis, Mariafelicia; Kramer, Michael; Ransom, Scott M.; Chatterjee, Shami; Wharton, Robert; Karuppusamy, Ramesh; Blackburn, Lindy; Janssen, Michael; Chan, Chi Kwan; Crew, Geoffrey, B.; Matthews, Lynn D.; Goddi, Ciriaco; Rottmann, Helge; Wagner, Jan; Sánchez, Salvador; Ruiz, Ignacio; Abbate, Federico; Bower, Geoffrey C.; Salamanca, Juan J.; Gómez-Ruiz, Arturo I.; Herrera-Aguilar, Alfredo; Jiang, Wu; Lu, Ru Sen; Pen, Ue Li; Raymond, Alexander W.; Shao, Lijing; Shen, Zhiqiang; Paubert, Gabriel; Sanchez-Portal, Miguel; Kramer, Carsten; Castillo, Manuel; Navarro, Santiago; John, David; Schuster, Karl Friedrich; Johnson, Michael D.; Rygl, Kazi L.J.; Akiyama, Kazunori; Alberdi, Antxon; Alef, Walter; Algaba, Juan Carlos; Anantua, Richard; Asada, Keiichi; Azulay, Rebecca; Bach, Uwe; Baczko, Anne Kathrin; Ball, David; Baloković, Mislav; Barrett, John; Bauböck, Michi; Benson, Bradford A.; Bintley, Dan; Blundell, Raymond; Bouman, Katherine L.; Boyce, Hope; Bremer, Michael; Brinkerink, Christiaan D.; Brissenden, Roger; Britzen, Silke; Broderick, Avery E.; Broguiere, Dominique; Bronzwaer, Thomas; Bustamante, Sandra; Byun, Do Young; Carlstrom, John E.; Ceccobello, Chiara; Chael, Andrew; Chang, Dominic O.; Chatterjee, Koushik; Chen, Ming Tang; Chen, Yongjun; Cheng, Xiaopeng; Cho, Ilje; Christian, Pierre; Conroy, Nicholas S.; Conway, John E.; Crawford, Thomas M.; Cruz-Osorio, Alejandro; Cui, Yuzhu; Dahale, Rohan; Davelaar, Jordy; Deane, Roger; Dempsey, Jessica; Dexter, Jason; Dhruv, Vedant; Doeleman, Sheperd S.; Dougal, Sean; Dzib, Sergio A.; Emami, Razieh; Falcke, Heino; Farah, Joseph; Fish, Vincent L.; Fomalont, Ed; Ford, H. Alyson; Foschi, Marianna; Fraga-Encinas, Raquel; Freeman, William T.; Friberg, Per; Fromm, Christian M.; Fuentes, Antonio; Galison, Peter; Gammie, Charles F.; García, Roberto; Gentaz, Olivier; Georgiev, Boris; Gold, Roman; Gómez, José L.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Haggard, Daryl; Haworth, Kari; Hecht, Michael H.; Hesper, Ronald; Heumann, Dirk; Ho, Luis C.; Ho, Paul; Honma, Mareki; Huang, Chih Wei L.; Huang, Lei; Hughes, David H.; Ikeda, Shiro; Impellizzeri, C. M.Violette; Inoue, Makoto; Issaoun, Sara; James, David J.; Jannuzi, Buell T.; Jeter, Britton; Jiménez-Rosales, Alejandra; Jorstad, Svetlana; Joshi, Abhishek V.; Jung, Taehyun; Karami, Mansour; Kawashima, Tomohisa; Keating, Garrett K.; Kettenis, Mark; Kim, Dong Jin; Kim, Jae Young; Kim, Jongsoo; Kim, Junhan; Kino, Motoki; Koay, Jun Yi; Kocherlakota, Prashant; Kofuji, Yutaro; Koyama, Shoko; Krichbaum, Thomas P.; Kuo, Cheng Yu; La Bella, Noemi; Lauer, Tod R.; Lee, Daeyoung; Lee, Sang Sung; Leung, Po Kin; Levis, Aviad; Li, Zhiyuan; Lico, Rocco; Lindahl, Greg; Lindqvist, Michael; Lisakov, Mikhail; Liu, Jun; Liuzzo, Elisabetta; Lo, Wen Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin J.; MacDonald, Nicholas R.; Mao, Jirong; Marchili, Nicola; Markoff, Sera; Marrone, Daniel P.; Marscher, Alan P.; Martí-Vidal, Iván; Matsushita, Satoki; Medeiros, Lia; Menten, Karl M.; Michalik, Daniel; Mizuno, Izumi; Mizuno, Yosuke; Moran, James M.; Moriyama, Kotaro; Moscibrodzka, Monika; Müller, Cornelia; Müller, Hendrik; Mus, Alejandro; Musoke, Gibwa; Myserlis, Ioannis; Nadolski, Andrew; Nagai, Hiroshi; Nagar, Neil M.; Nakamura, Masanori; Narayan, Ramesh; Narayanan, Gopal; Natarajan, Iniyan; Nathanail, Antonios; Neilsen, Joey; Neri, Roberto; Ni, Chunchong; Noutsos, Aristeidis; Nowak, Michael A.; Oh, Junghwan; Okino, Hiroki; Olivares, Héctor; Ortiz-León, Gisela N.; Oyama, Tomoaki; Özel, Feryal; Palumbo, Daniel C.M.; Paraschos, Georgios Filippos; Park, Jongho; Parsons, Harriet; Patel, Nimesh; Pesce, Dominic W.; Piétu, Vincent; Plambeck, Richard; PopStefanija, Aleksandar; Porth, Oliver; Pötzl, Felix M.; Prather, Ben; Preciado-López, Jorge A.; Psaltis, Dimitrios; Pu, Hung Yi; Ramakrishnan, Venkatessh; Rao, Ramprasad; Rawlings, Mark G.; Rezzolla, Luciano; Ricarte, Angelo; Ripperda, Bart; Roelofs, Freek; Rogers, Alan; Ros, Eduardo; Romero-Cañizales, Cristina; Roshanineshat, Arash; Roy, Alan L.; Ruszczyk, Chet; Sánchez-Argüelles, David; Sasada, Mahito; Satapathy, Kaushik; Savolainen, Tuomas; Schloerb, F. Peter; Schonfeld, Jonathan; Small, Des; Sohn, Bong Won; SooHoo, Jason; Souccar, Kamal; Sun, He; Tetarenko, Alexandra J.; Tiede, Paul; Tilanus, Remo P.J.; Titus, Michael; Toscano, Teresa; Traianou, Efthalia; Trent, Tyler; Trippe, Sascha; Turk, Matthew; van Bemmel, Ilse; van Langevelde, Huib Jan; van Rossum, Daniel R.; Vos, Jesse; Ward-Thompson, Derek; Wardle, John; Weintroub, Jonathan; Wex, Norbert; Wielgus, Maciek; Wiik, Kaj; Witzel, Gunther; Wondrak, Michael F.; Wong, George N.; Wu, Qingwen; Yadlapalli, Nitika; Yamaguchi, Paul; Yfantis, Aristomenis; Yoon, Doosoo; Young, André; Young, Ken; Younsi, Ziri; Yu, Wei; Yuan, Feng; Yuan, Ye Fei; Zensus, J. Anton; Zhang, Shuo; Zhao, Guang Yao; Zhao, Shan Shan; Metsähovi Radio Observatory; Department of Electronics and Nanoengineering; Anne Lähteenmäki Group; Max Planck Institute for Radio Astronomy; Cornell University; University of Naples Federico II; National Radio Astronomy Observatory; California Institute of Technology; Harvard University; University of Arizona; Massachusetts Institute of Technology MIT; Universidade de São Paulo; Academia Sinica Institute of Astronomy and Astrophysics; University of Oviedo; Instituto Nacional de Astrofísica, Óptica y Electrónica; Meritorious Autonomous University of Puebla; Chinese Academy of Sciences; Academia Sinica; INAF - Istituto di Radioastronomia; Instituto de Astrofísica de Andalucía; University of Malaya; Yale University; University of Illinois; Fermi National Accelerator Laboratory; East Asian Observatory; McGill University; Radboud University Nijmegen; University of Waterloo; University of Massachusetts; Korea Astronomy and Space Science Institute; University of Chicago; Chalmers University of Technology; Princeton University; Fairfield University; Goethe University Frankfurt; Shanghai Jiao Tong University; Columbia University; University of the Witwatersrand, Johannesburg; ASTRON - Netherlands Institute for Radio Astronomy; University of Colorado; Las Cumbres Observatory; University of Illinois at Urbana-Champaign; University of Southern Denmark; National Astronomical Observatory of Japan; University of Groningen; Peking University; Research Organization of Information and Systems, The Institute of Statistical Mathematics; Astraveo LLC; Boston University; Joint Institute for VLBI ERIC; Niigata University; National Sun Yat-sen University
    In 2017 the Event Horizon Telescope (EHT) observed the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz (λ = 1.3 mm). The fundamental physics tests that even a single pulsar orbiting Sgr A* would enable motivate searching for pulsars in EHT data sets. The high observing frequency means that pulsars—which typically exhibit steep emission spectra—are expected to be very faint. However, it also negates pulse scattering, an effect that could hinder pulsar detections in the Galactic center. Additionally, magnetars or a secondary inverse Compton emission could be stronger at millimeter wavelengths than at lower frequencies. We present a search for pulsars close to Sgr A* using the data from the three most sensitive stations in the EHT 2017 campaign: the Atacama Large Millimeter/submillimeter Array, the Large Millimeter Telescope, and the IRAM 30 m Telescope. We apply three detection methods based on Fourier-domain analysis, the fast folding algorithm, and single-pulse searches targeting both pulsars and burst-like transient emission. We use the simultaneity of the observations to confirm potential candidates. No new pulsars or significant bursts were found. Being the first pulsar search ever carried out at such high radio frequencies, we detail our analysis methods and give a detailed estimation of the sensitivity of the search. We conclude that the EHT 2017 observations are only sensitive to a small fraction (≲2.2%) of the pulsars that may exist close to Sgr A*, motivating further searches for fainter pulsars in the region.
  • Thumbnail Image
    Item
    Testing the magnetic flux paradigm for AGN radio loudness with a radio-intermediate quasar
    (EDP SCIENCES, 2021-08-03) Chamani, Wara; Savolainen, Tuomas; Hada, Kazuhiro; Xu, Ming H.; Metsähovi Radio Observatory; Department of Electronics and Nanoengineering; Anne Lähteenmäki Group; National Astronomical Observatory of Japan
    For understanding the diversity of jetted active galactic nuclei (AGN) and especially the puzzling wide range in their radio loudness, it is important to understand what role the magnetic fields play in setting the power of relativistic jets in AGN. We have performed VLBA phase-referencing observations of the radio-intermediate quasar IIIZw 2 to estimate jet magnetic flux by measuring the core-shift effect. Multi-frequency observations at 4 GHz, 8 GHz, 15 GHz, and 24 GHz were made using three nearby calibrators as reference sources. By combining the self-referencing core shift of each calibrator with the phase-referencing core shifts, we obtained an upper limit of 0.16 mas for the core shift between 4 and 24 GHz in IIIZw 2. By assuming equipartition between magnetic and particle energy densities and adopting the flux-freezing approximation, we further estimated the upper limit for both the magnetic field strength and poloidal magnetic flux threading the black hole. We find that the upper limit to the measured magnetic flux is smaller by at least a factor of five compared to the value predicted by the magnetically arrested disk (MAD) model. An alternative way to derive the jet magnetic field strength from the turnover of the synchrotron spectrum leads to an even smaller upper limit. Hence, the central engine of IIIZw 2 has not reached the MAD state, which could explain why it has failed to develop a powerful jet even though the source harbours a fast-spinning black hole. However, it generates an intermittent jet, which is possibly triggered by small-scale magnetic field fluctuations, as predicted by the magnetic flux paradigm. We propose here that combining black hole spin measurements with magnetic field measurements from the very-long-baseline-interferometry core-shift observations of AGN over a range of jet powers could provide a strong test for the dominant factor that sets the jet power relative to the available accretion power.
  • Thumbnail Image
    Item
    THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope
    (IOP Publishing Ltd., 2020-07-10) Broderick, Avery E.; Gold, Roman; Karami, Mansour; Preciado-López, Jorge A.; Tiede, Paul; Pu, Hung Yi; Akiyama, Kazunori; Alberdi, Antxon; Alef, Walter; Asada, Keiichi; Azulay, Rebecca; Baczko, Anne Kathrin; Baloković, Mislav; Barrett, John; Bintley, Dan; Blackburn, Lindy; Boland, Wilfred; Bouman, Katherine L.; Bower, Geoffrey C.; Bremer, Michael; Brinkerink, Christiaan D.; Brissenden, Roger; Britzen, Silke; Broguiere, Dominique; Bronzwaer, Thomas; Byun, Do Young; Carlstrom, John E.; Chael, Andrew; Chatterjee, Shami; Chatterjee, Koushik; Chen, Ming Tang; Chen, Yongjun; Cho, Ilje; Conway, John E.; Cordes, James M.; Crew, Geoffrey B.; Cui, Yuzhu; Davelaar, Jordy; De Laurentis, Mariafelicia; Deane, Roger; Dempsey, Jessica; Desvignes, Gregory; Doeleman, Sheperd S.; Eatough, Ralph P.; Falcke, Heino; Fish, Vincent L.; Fomalont, Ed; Fraga-Encinas, Raquel; Friberg, Per; Fromm, Christian M.; Galison, Peter; Gammie, Charles F.; García, Roberto; Gentaz, Olivier; Georgiev, Boris; Goddi, Ciriaco; Gómez, José L.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Hecht, Michael H.; Hesper, Ronald; Ho, Luis C.; Ho, Paul; Honma, Mareki; Huang, Chih Wei L.; Huang, Lei; Hughes, David H.; Inoue, Makoto; Issaoun, Sara; James, David J.; Janssen, Michael; Jeter, Britton; Jiang, Wu; Jiménez-Rosales, Alejandra; Johnson, Michael D.; Jorstad, Svetlana; Jung, Taehyun; Karuppusamy, Ramesh; Kawashima, Tomohisa; Keating, Garrett K.; Kettenis, Mark; Kim, Jae Young; Kim, Jongsoo; Kino, Motoki; Koay, Jun Yi; Koch, Patrick M.; Koyama, Shoko; Kramer, Michael; Kramer, Carsten; Krichbaum, Thomas P.; Kuo, Cheng Yu; Lee, Sang Sung; Li, Yan Rong; Li, Zhiyuan; Lindqvist, Michael; Lico, Rocco; Liu, Kuo; Liuzzo, Elisabetta; Lo, Wen Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin; Lu, Ru Sen; MacDonald, Nicholas R.; Mao, Jirong; Marscher, Alan P.; Martí-Vidal, Iván; Matsushita, Satoki; Matthews, Lynn D.; Menten, Karl M.; Mizuno, Yosuke; Mizuno, Izumi; Moran, James M.; Moriyama, Kotaro; Moscibrodzka, Monika; Müller, Cornelia; Nagai, Hiroshi; Nagar, Neil M.; Nakamura, Masanori; Narayan, Ramesh; Narayanan, Gopal; Natarajan, Iniyan; Neri, Roberto; Ni, Chunchong; Noutsos, Aristeidis; Okino, Hiroki; Olivares, Héctor; Ortiz-León, Gisela N.; Oyama, Tomoaki; Palumbo, Daniel C.M.; Park, Jongho; Pen, Ue Li; Pesce, Dominic W.; Piétu, Vincent; Plambeck, Richard; Popstefanija, Aleksandar; Porth, Oliver; Prather, Ben; Ramakrishnan, Venkatessh; Rao, Ramprasad; Rawlings, Mark G.; Rezzolla, Luciano; Ripperda, Bart; Roelofs, Freek; Rogers, Alan; Ros, Eduardo; Rose, Mel; Rottmann, Helge; Ruszczyk, Chet; Ryan, Benjamin R.; Rygl, Kazi L.J.; Sánchez, Salvador; Sánchez-Arguelles, David; Sasada, Mahito; Savolainen, Tuomas; Schloerb, F. Peter; Schuster, Karl Friedrich; Shao, Lijing; Shen, Zhiqiang; Small, Des; Sohn, Bong Won; Soohoo, Jason; Tazaki, Fumie; Tilanus, Remo P.J.; Titus, Michael; Toma, Kenji; Torne, Pablo; Traianou, Efthalia; Trippe, Sascha; Tsuda, Shuichiro; Van Bemmel, Ilse; Van Langevelde, Huib Jan; Van Rossum, Daniel R.; Wagner, Jan; Wardle, John; Weintroub, Jonathan; Wex, Norbert; Wharton, Robert; Wielgus, MacIek; Wong, George N.; Wu, Qingwen; Yoon, Doosoo; Young, André; Young, Ken; Younsi, Ziri; Yuan, Feng; Yuan, Ye Fei; Zensus, J. Anton; Zhao, Guangyao; Zhao, Shan Shan; Zhu, Ziyan; Department of Electronics and Nanoengineering; Metsähovi Radio Observatory; Anne Lähteenmäki Group; Perimeter Institute for Theoretical Physics; National Radio Astronomy Observatory; CSIC; Max Planck Institute for Radio Astronomy; Academia Sinica Institute of Astronomy and Astrophysics; Harvard University; Massachusetts Institute of Technology; East Asian Observatory; Nederlandse Onderzoekschool voor Astronomie; Academia Sinica; Institut de Radioastronomie Millimétrique; Radboud University Nijmegen; Korea Astronomy and Space Science Institute; University of Chicago; Cornell University; University of Amsterdam; CAS - Shanghai Astronomical Observatory; Chalmers University of Technology; National Astronomical Observatory of Japan; Goethe University Frankfurt; University of Pretoria; University of Illinois at Urbana-Champaign; University of Groningen; Peking University; Instituto Nacional de Astrofísica, Óptica y Electrónica; Max Planck Institute for Extraterrestrial Physics; St. Petersburg State University; Joint Institute for VLBI in Europe; National Sun Yat-sen University; CAS - Institute of High Energy Physics; Nanjing University; National Institute for Astrophysics (INAF); Universidad Nacional Autónoma de México; Chinese Academy of Sciences; Boston University; University of Valencia; Universidad de Concepción; University of Massachusetts; Rhodes University; University of California, Berkeley; University of Arizona; Los Alamos National Laboratory; Instituto de Radioastronomía Milimétrica; Tohoku University; Seoul National University; Brandeis University; Huazhong University of Science and Technology; University of Science and Technology of China
    The Event Horizon Telescope (EHT) provides the unprecedented ability to directly resolve the structure and dynamics of black hole emission regions on scales smaller than their horizons. This has the potential to critically probe the mechanisms by which black holes accrete and launch outflows, and the structure of supermassive black hole spacetimes. However, accessing this information is a formidable analysis challenge for two reasons. First, the EHT natively produces a variety of data types that encode information about the image structure in nontrivial ways; these are subject to a variety of systematic effects associated with very long baseline interferometry and are supplemented by a wide variety of auxiliary data on the primary EHT targets from decades of other observations. Second, models of the emission regions and their interaction with the black hole are complex, highly uncertain, and computationally expensive to construct. As a result, the scientific utilization of EHT observations requires a flexible, extensible, and powerful analysis framework. We present such a framework, Themis, which defines a set of interfaces between models, data, and sampling algorithms that facilitates future development. We describe the design and currently existing components of Themis, how Themis has been validated thus far, and present additional analyses made possible by Themis that illustrate its capabilities. Importantly, we demonstrate that Themis is able to reproduce prior EHT analyses, extend these, and do so in a computationally efficient manner that can efficiently exploit modern high-performance computing facilities. Themis has already been used extensively in the scientific analysis and interpretation of the first EHT observations of M87.
  • Thumbnail Image
    Item
    The Variability of the Black Hole Image in M87 at the Dynamical Timescale
    (IOP Publishing Ltd., 2022-01-01) Satapathy, Kaushik; Psaltis, Dimitrios; Ozel, Feryal; Medeiros, Lia; Dougall, Sean T.; Chan, Chi-Kwan; Wielgus, Maciek; Prather, Ben S.; Wong, George N.; Gammie, Charles F.; Akiyama, Kazunori; Alberdi, Antxon; Alef, Walter; Algaba, Juan Carlos; Anantua, Richard; Asada, Keiichi; Azulay, Rebecca; Baczko, Anne-Kathrin; Ball, David; Balokovic, Mislay; Barrett, John; Benson, Bradford A.; Bintley, Dan; Blackburn, Lindy; Blundell, Raymond; Boland, Wilfred; Bouman, Katherine L.; Bower, Geoffrey C.; Boyce, Hope; Bremer, Michael; Brinkerink, Christiaan D.; Brissenden, Roger; Britzen, Silke; Broderick, Avery E.; Broguiere, Dominique; Bronzwaer, Thomas; Bustamente, Sandra; Byun, Do-Young; Carlstrom, John E.; Chael, Andrew; Chatterjee, Koushik; Chatterjee, Shami; Chen, Ming-Tang; Chen, Yongjun; Cho, Ilje; Christian, Pierre; Conway, John E.; Cordes, James M.; Crawford, Thomas M.; Crew, Geoffrey B.; Cruz-Osorio, Alejandro; Cui, Yuzhu; Davelaar, Jordy; De Laurentis, Mariafelicia; Deane, Roger; Dempsey, Jessica; Desvignes, Gregory; Dexter, Jason; Doeleman, Sheperd S.; Eatough, Ralph P.; Falcke, Heino; Farah, Joseph; Fish, Vincent L.; Fomalont, Ed; Ford, H. Alyson; Fraga-Encinas, Raquel; Friberg, Per; Fromm, Christian M.; Fuentes, Antonio; Galison, Peter; Garcia, Roberto; Gentaz, Olivier; Georgiev, Boris; Goddi, Ciriaco; Gold, Roman; Gomez-Ruiz, Arturo; Gomez, Jose L.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Haggard, Daryl; Hecht, Michael H.; Hesper, Ronald; Ho, Paul; Honma, Mareki; Huang, Chih-Wei L.; Huang, Lei; Hughes, David H.; Ikeda, Shiro; Inoue, Makoto; Issaoun, Sara; James, David J.; Jannuzi, Buell T.; Janssen, Michael; Jeter, Britton; Jiang, Wu; Jimenez-Rosales, Alejandra; Johnson, Michael D.; Jorstad, Svetlana; Jung, Taehyun; Karami, Mansour; Karuppusamy, Ramesh; Kawashima, Tomohisa; Keating, Garrett K.; Kettenis, Mark; Kim, Dong-Jin; Kim, Jae-Young; Kim, Jongsoo; Kim, Junhan; Kino, Motoki; Koay, Jun Yi; Kofuji, Yutaro; Koch, Patrick M.; Koyama, Shoko; Kramer, Carsten; Kramer, Michael; Krichbaum, Thomas P.; Kuo, Cheng-Yu; Lauer, Tod R.; Lee, Sang-Sung; Levis, Aviad; Li, Yan-Rong; Li, Zhiyuan; Lindqvist, Michael; Lico, Rocco; Lindahl, Greg; Liu, Jun; Liu, Kuo; Liuzzo, Elisabetta; Lo, Wen-Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin; Lu, Ru-Sen; MacDonald, Nicholas R.; Mao, Jirong; Marchili, Nicola; Markoff, Sera; Marrone, Daniel P.; Marscher, Alan P.; Marti-Vidal, Ivan; Matsushita, Satoki; Matthews, Lynn D.; Menten, Karl M.; Mizuno, Izumi; Mizuno, Yosuke; Moran, James M.; Moriyama, Kotaro; Moscibrodzka, Monika; Mueller, Cornelia; Mejias, Alejandro Mus; Musoke, Gibwa; Nagai, Hiroshi; Nagar, Neil M.; Nakamura, Masanori; Narayan, Ramesh; Narayanan, Gopal; Natarajan, Iniyan; Nathanail, Antonios; Neilsen, Joey; Neri, Roberto; Ni, Chunchong; Noutsos, Aristeidis; Nowak, Michael A.; Okino, Hiroki; Olivares, Hector; Ortiz-Leon, Gisela N.; Oyama, Tomoaki; Palumbo, Daniel C. M.; Park, Jongho; Patel, Nimesh; Pen, Ue-Li; Pesce, Dominic W.; Pietu, Vincent; Plambeck, Richard; PopStefanija, Aleksandar; Porth, Oliver; Potzl, Felix M.; Preciado-Lopez, Jorge A.; Pu, Hung-Yi; Ramakrishnan, Venkatessh; Rao, Ramprasad; Rawlings, Mark G.; Raymond, Alexander W.; Rezzolla, Luciano; Ripperda, Bart; Roelofs, Freek; Rogers, Alan; Ros, Eduardo; Rose, Mel; Roshanineshat, Arash; Rottmann, Helge; Roy, Alan L.; Ruszczyk, Chet; Rygl, Kazi L. J.; Sanchez, Salvador; Sanchez-Arguelles, David; Sasada, Mahito; Savolainen, Tuomas; Schloerb, F. Peter; Schuster, Karl-Friedrich; Shao, Lijing; Shen, Zhiqiang; Small, Des; Sohn, Bong Won; SooHoo, Jason; Sun, He; Tazaki, Fumie; Tetarenko, Alexandra J.; Tiede, Paul; Tilanus, Remo P. J.; Titus, Michael; Toma, Kenji; Torne, Pablo; Traianou, Efthalia; Trent, Tyler; Trippe, Sascha; van Bemmel, Ilse; van Langevelde, Huib Jan; van Rossum, Daniel R.; Wagner, Jan; Ward-Thompson, Derek; Wardle, John; Weintroub, Jonathan; Wex, Norbert; Wharton, Robert; Wiik, Kaj; Wu, Qingwen; Yoon, Doosoo; Young, Andre; Young, Ken; Younsi, Ziri; Yuan, Feng; Yuan, Ye-Fei; Zensus, J. Anton; Zhao, Guang-Yao; Zhao, Shan-Shan; Department of Electronics and Nanoengineering; Metsähovi Radio Observatory; Anne Lähteenmäki Group
    The black hole images obtained with the Event Horizon Telescope (EHT) are expected to be variable at the dynamical timescale near their horizons. For the black hole at the center of the M87 galaxy, this timescale (5-61 days) is comparable to the 6 day extent of the 2017 EHT observations. Closure phases along baseline triangles are robust interferometric observables that are sensitive to the expected structural changes of the images but are free of station-based atmospheric and instrumental errors. We explored the day-to-day variability in closure-phase measurements on all six linearly independent nontrivial baseline triangles that can be formed from the 2017 observations. We showed that three triangles exhibit very low day-to-day variability, with a dispersion of ∼3°-5°. The only triangles that exhibit substantially higher variability (∼90°-180°) are the ones with baselines that cross the visibility amplitude minima on the u-v plane, as expected from theoretical modeling. We used two sets of general relativistic magnetohydrodynamic simulations to explore the dependence of the predicted variability on various black hole and accretion-flow parameters. We found that changing the magnetic field configuration, electron temperature model, or black hole spin has a marginal effect on the model consistency with the observed level of variability. On the other hand, the most discriminating image characteristic of models is the fractional width of the bright ring of emission. Models that best reproduce the observed small level of variability are characterized by thin ring-like images with structures dominated by gravitational lensing effects and thus least affected by turbulence in the accreting plasmas.