Browsing by Author "Wielgus, Maciek"

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  • Collimation of the Relativistic Jet in the Quasar 3C 273
    (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
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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.
  • The Event Horizon Telescope Image of the Quasar NRAO 530
    (2023-02-01) Jorstad, Svetlana; Wielgus, Maciek; Lico, Rocco; Issaoun, Sara; Broderick, Avery E.; Pesce, Dominic W.; Liu, Jun; Zhao, Guang Yao; Krichbaum, Thomas P.; Blackburn, Lindy; Chan, Chi Kwan; Janssen, Michael; Ramakrishnan, Venkatessh; Akiyama, Kazunori; Alberdi, Antxon; Algaba, Juan Carlos; Bouman, Katherine L.; Cho, Ilje; Fuentes, Antonio; Gómez, José L.; Gurwell, Mark; , Event Horizon Telescope Collaborat
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We report on the observations of the quasar NRAO 530 with the Event Horizon Telescope (EHT) on 2017 April 5−7, when NRAO 530 was used as a calibrator for the EHT observations of Sagittarius A*. At z = 0.902, this is the most distant object imaged by the EHT so far. We reconstruct the first images of the source at 230 GHz, at an unprecedented angular resolution of ∼20 μas, both in total intensity and in linear polarization (LP). We do not detect source variability, allowing us to represent the whole data set with static images. The images reveal a bright feature located on the southern end of the jet, which we associate with the core. The feature is linearly polarized, with a fractional polarization of ∼5%-8%, and it has a substructure consisting of two components. Their observed brightness temperature suggests that the energy density of the jet is dominated by the magnetic field. The jet extends over 60 μas along a position angle ∼ −28°. It includes two features with orthogonal directions of polarization (electric vector position angle), parallel and perpendicular to the jet axis, consistent with a helical structure of the magnetic field in the jet. The outermost feature has a particularly high degree of LP, suggestive of a nearly uniform magnetic field. Future EHT observations will probe the variability of the jet structure on microarcsecond scales, while simultaneous multiwavelength monitoring will provide insight into the high-energy emission origin.
  • Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution
    (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
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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.
  • First Very Long Baseline Interferometry Detections at 870 μm
    (2024-09-01) Raymond, Alexander W.; Doeleman, Sheperd S.; Asada, Keiichi; Blackburn, Lindy; Bower, Geoffrey C.; Bremer, Michael; Broguiere, Dominique; Chen, Ming Tang; Crew, Geoffrey B.; Dornbusch, Sven; Fish, Vincent L.; García, Roberto; Gentaz, Olivier; Goddi, Ciriaco; Han, Chih Chiang; Hecht, Michael H.; Huang, Yau De; Janssen, Michael; Keating, Garrett K.; Koay, Jun Yi; Krichbaum, Thomas P.; Lo, Wen Ping; Matsushita, Satoki; Matthews, Lynn D.; Moran, James M.; Norton, Timothy J.; Patel, Nimesh; Pesce, Dominic W.; Ramakrishnan, Venkatessh; Rottmann, Helge; Roy, Alan L.; Sánchez, Salvador; Tilanus, Remo P.J.; Titus, Michael; Torne, Pablo; Wagner, Jan; Weintroub, Jonathan; Wielgus, Maciek; Young, André; Akiyama, Kazunori; Albentosa-Ruíz, Ezequiel; Alberdi, Antxon; Alef, Walter; Algaba, Juan Carlos; Anantua, Richard; Azulay, Rebecca; Bach, Uwe; Baczko, Anne Kathrin; Ball, David; Balokovic, Mislav; Bandyopadhyay, Bidisha; Barrett, John; Bauböck, Michi; Benson, Bradford A.; Bintley, Dan; Blundell, Raymond; Bouman, Katherine L.; Boyce, Hope; Brissenden, Roger; Britzen, Silke; Broderick, Avery E.; Bronzwaer, Thomas; Bustamante, Sandra; Carlstrom, John E.; Chael, Andrew; Chan, Chi Kwan; Chang, Dominic O.; Chatterjee, Koushik; Chatterjee, Shami; Chen, 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; De Laurentis, Mariafelicia; Deane, Roger; Dempsey, Jessica; Desvignes, Gregory; Dexter, Jason; Dhruv, Vedant; Dihingia, Indu K.; Dzib, Sergio A.; Eatough, Ralph P.; Emami, Razieh; Falcke, Heino; Farah, Joseph; Fomalont, Edward; Fontana, Anne Laure; Ford, H. Alyson; Foschi, Marianna; Fraga-Encinas, Raquel; Freeman, William T.; Friberg, Per; Fromm, Christian M.; Fuentes, Antonio; Galison, Peter; Gammie, Charles F.; Georgiev, Boris; Gold, Roman; Gómez-Ruiz, Arturo I.; Gómez, José L.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Haggard, Daryl; 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; Johnson, Michael D.; Jorstad, Svetlana; Jones, Adam C.; Joshi, Abhishek V.; Jung, Taehyun; Karuppusamy, Ramesh; Kawashima, Tomohisa; Kettenis, Mark; Kim, Dong Jin; Kim, Jae Young; Kim, Jongsoo; Kim, Junhan; Kino, Motoki; Kocherlakota, Prashant; Kofuji, Yutaro; Koch, Patrick M.; Koyama, Shoko; Kramer, Carsten; Kramer, Joana A.; Kramer, Michael; Kubo, Derek; Kuo, Cheng Yu; La Bella, Noemi; Lee, Sang Sung; Levis, Aviad; Li, Zhiyuan; Lico, Rocco; Lindahl, Greg; Lindqvist, Michael; Lisakov, Mikhail; Liu, Jun; Liu, Kuo; Liuzzo, Elisabetta; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin J.; Lowitz, Amy E.; Lu, Ru Sen; MacDonald, Nicholas R.; Mahieu, Sylvain; Maier, Doris; Mao, Jirong; Marchili, Nicola; Markoff, Sera; Marrone, Daniel P.; Marscher, Alan P.; Martí-Vidal, Iván; Medeiros, Lia; Menten, Karl M.; Mizuno, Izumi; Mizuno, Yosuke; Montgomery, Joshua; Moriyama, Kotaro; Moscibrodzka, Monika; Mulaudzi, Wanga; Müller, Cornelia; Müller, Hendrik; Mus, Alejandro; Musoke, Gibwa; Myserlis, Ioannis; Nagai, Hiroshi; Nagar, Neil M.; Nakamura, Masanori; Narayanan, Gopal; Natarajan, Iniyan; Nathanail, Antonios; Fuentes, Santiago Navarro; Neilsen, Joey; Ni, Chunchong; Nowak, Michael A.; Oh, Junghwan; Okino, Hiroki; Olivares Sánchez, Héctor Raúl; Oyama, Tomoaki; Özel, Feryal; Palumbo, Daniel C.M.; Paraschos, Georgios Filippos; Park, Jongho; Parsons, Harriet; Pen, Ue Li; Piétu, Vincent; PopStefanija, Aleksandar; Porth, Oliver; Prather, Ben; Principe, Giacomo; Psaltis, Dimitrios; Pu, Hung Yi; Raffin, Philippe A.; Rao, Ramprasad; Rawlings, Mark G.; Ricarte, Angelo; Ripperda, Bart; Roelofs, Freek; Romero-Cañizales, Cristina; Ros, Eduardo; Roshanineshat, Arash; Ruiz, Ignacio; Ruszczyk, Chet; Rygl, Kazi L.J.; Sánchez-Argüelles, David; Sánchez-Portal, Miguel; Sasada, Mahito; Satapathy, Kaushik; Savolainen, Tuomas; Schloerb, F. Peter; Schonfeld, Jonathan; Schuster, Karl Friedrich; Shao, Lijing; Shen, Zhiqiang; Small, Des; Sohn, Bong Won; SooHoo, Jason; Sosapanta Salas, León David; Souccar, Kamal; Stanway, Joshua S.; Sun, He; Tazaki, Fumie; Tetarenko, Alexandra J.; Tiede, Paul; Toma, Kenji; Toscano, Teresa; Traianou, Efthalia; Trent, Tyler; Trippe, Sascha; Turk, Matthew; van Bemmel, Ilse; van Langevelde, Huib Jan; van Rossum, Daniel R.; Vos, Jesse; Ward-Thompson, Derek; Wardle, John; Washington, Jasmin E.; Wharton, Robert; Wiik, Kaj; Witzel, Gunther; Wondrak, Michael F.; Wong, George N.; Wu, Qingwen; Yadlapalli, Nitika; Yamaguchi, Paul; Yfantis, Aristomenis; Yoon, Doosoo; Younsi, Ziri; Yu, Wei; Yuan, Feng; Yuan, Ye Fei; Zensus, J. Anton; Zhang, Shuo; Zhao, Guang Yao; Zhao, Shan Shan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The first very long baseline interferometry (VLBI) detections at 870 μm wavelength (345 GHz frequency) are reported, achieving the highest diffraction-limited angular resolution yet obtained from the surface of the Earth and the highest-frequency example of the VLBI technique to date. These include strong detections for multiple sources observed on intercontinental baselines between telescopes in Chile, Hawaii, and Spain, obtained during observations in 2018 October. The longest-baseline detections approach 11 Gλ, corresponding to an angular resolution, or fringe spacing, of 19 μas. The Allan deviation of the visibility phase at 870 μm is comparable to that at 1.3 mm on the relevant integration timescales between 2 and 100 s. The detections confirm that the sensitivity and signal chain stability of stations in the Event Horizon Telescope (EHT) array are suitable for VLBI observations at 870 μm. Operation at this short wavelength, combined with anticipated enhancements of the EHT, will lead to a unique high angular resolution instrument for black hole studies, capable of resolving the event horizons of supermassive black holes in both space and time.
  • Millimeter Light Curves of Sagittarius A* Observed during the 2017 Event Horizon Telescope Campaign
    (2022-05-01) Wielgus, Maciek; Marchili, Nicola; Martí-Vidal, Iván; Keating, Garrett K.; Ramakrishnan, Venkatessh; Tiede, Paul; Fomalont, Ed; Issaoun, Sara; Neilsen, Joey; Nowak, Michael A.; Blackburn, Lindy; Gammie, Charles F.; Goddi, Ciriaco; Haggard, Daryl; Lee, Daeyoung; Moscibrodzka, Monika; Tetarenko, Alexandra J.; Bower, Geoffrey C.; Chan, Chi Kwan; Chatterjee, Koushik; Chesler, Paul M.; Dexter, Jason; Doeleman, Sheperd S.; Georgiev, Boris; Gurwell, Mark; Johnson, Michael D.; Marrone, Daniel P.; Mus, Alejandro; Psaltis, Dimitrios; Ripperda, Bart; Witzel, Gunther; 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; Kim, Dong Jin; Savolainen, Tuomas; Wagner, Jan; , Event Horizon Telescope Collaborat
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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.
  • Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes
    (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
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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.
  • The Polarized Image of a Synchrotron-emitting Ring of Gas Orbiting a Black Hole
    (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
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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.
  • Resolving the Inner Parsec of the Blazar J1924-2914 with the Event Horizon Telescope
    (2022-08-01) Issaoun, Sara; Wielgus, Maciek; Jorstad, Svetlana; Krichbaum, Thomas P.; Blackburn, Lindy; Janssen, Michael; Chan, Chi-kwan; Pesce, Dominic W.; Gomez, Jose L.; Akiyama, Kazunori; Moscibrodzka, Monika; Marti-Vidal, Ivan; Chael, Andrew; Lico, Rocco; Liu, Jun; Ramakrishnan, Venkatessh; Lisakov, Mikhail; Fuentes, Antonio; Zhao, Guang-Yao; Moriyama, Kotaro; Broderick, Avery E.; Tiede, Paul; MacDonald, Nicholas R.; Mizuno, Yosuke; Traianou, Efthalia; Loinard, Laurent; Davelaar, Jordy; Gurwell, Mark; Lu, Ru-Sen; Alberdi, Antxon; Alef, Walter; Algaba, Juan Carlos; Anantua, Richard; Asada, Keiichi; Azulay, Rebecca; Bach, Uwe; Baczko, Anne-Kathrin; Ball, David; Balokovic, Mislac; Barrett, John; Baubock, Michi; Benson, Bradford A.; Bintley, Dan; Blundell, Raymond; Boland, Wilfred; Bouman, Katherine L.; Bower, Geoffrey C.; Kim, Dong-Jin; Savolainen, Tuomas; Wagner, Jan; , Event Horizon Telescope Collaborat
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The blazar J1924–2914 is a primary Event Horizon Telescope (EHT) calibrator for the Galactic center’s black hole Sagittarius A *. Here we present the first total and linearly polarized intensity images of this source obtained with the unprecedented 20 µas resolution of the EHT. J1924–2914 is a very compact flat-spectrum radio source with strong optical variability and polarization. In April 2017 the source was observed quasi-simultaneously with the EHT (April 5–11), the Global Millimeter VLBI Array (April 3), and the Very Long Baseline Array (April 28), giving a novel view of the source at four observing frequencies, 230, 86, 8.7, and 2.3 GHz. These observations probe jet properties from the subparsec to 100 pc scales. We combine the multifrequency images of J1924–2914 to study the source morphology. We find that the jet exhibits a characteristic bending, with a gradual clockwise rotation of the jet projected position angle of about 90° between 2.3 and 230 GHz. Linearly polarized intensity images of J1924–2914 with the extremely fine resolution of the EHT provide evidence for ordered toroidal magnetic fields in the blazar compact core.
  • The science case and challenges of space-borne sub-millimeter interferometry
    (2022-07) Gurvits, Leonid I.; Paragi, Zsolt; Amils, Ricardo I.; van Bemmel, Ilse; Boven, Paul; Casasola, Viviana; Conway, John; Davelaar, Jordy; Díez-González, M. Carmen; Falcke, Heino; Fender, Rob; Frey, Sándor; Fromm, Christian M.; Gallego-Puyol, Juan D.; García-Miró, Cristina; Garrett, Michael A.; Giroletti, Marcello; Goddi, Ciriaco; Gómez, José L.; van der Gucht, Jeffrey; Guirado, José Carlos; Haiman, Zoltán; Helmich, Frank; Hudson, Ben; Humphreys, Elizabeth; Impellizzeri, Violette; Janssen, Michael; Johnson, Michael D.; Kovalev, Yuri Y.; Kramer, Michael; Lindqvist, Michael; Linz, Hendrik; Liuzzo, Elisabetta; Lobanov, Andrei P.; López-Fernández, Isaac; Malo-Gómez, Inmaculada; Masania, Kunal; Mizuno, Yosuke; Plavin, Alexander V.; Rajan, Raj T.; Rezzolla, Luciano; Roelofs, Freek; Ros, Eduardo; Rygl, Kazi L. J.; Savolainen, Tuomas; Schuster, Karl; Venturi, Tiziana; Verkouter, Marjolein; de Vicente, Pablo; Visser, Pieter N. A. M.; Wiedner, Martina C.; Wielgus, Maciek; Wiik, Kaj; Zensus, J. Anton
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Ultra-high angular resolution in astronomy has always been an important vehicle for making fundamental discoveries. Recent results in direct imaging of the vicinity of the supermassive black hole in the nucleus of the radio galaxy M87 by the millimeter VLBI system Event Horizon Telescope and various pioneering results of the Space VLBI mission RadioAstron provided new momentum in high angular resolution astrophysics. In both mentioned cases, the angular resolution reached the values of about 10–20 microarcseconds (0.05–0.1 nanoradian). Further developments towards at least an order of magnitude “sharper” values, at the level of 1 microarcsecond are dictated by the needs of advanced astrophysical studies. The paper emphasis that these higher values can only be achieved by placing millimeter and submillimeter wavelength interferometric systems in space. A concept of such the system, called Terahertz Exploration and Zooming-in for Astrophysics, has been proposed in the framework of the ESA Call for White Papers for the Voyage 2050 long term plan in 2019. In the current paper we present new science objectives for such the concept based on recent results in studies of active galactic nuclei and supermassive black holes. We also discuss several approaches for addressing technological challenges of creating a millimeter/sub-millimeter wavelength interferometric system in space. In particular, we consider a novel configuration of a space-borne millimeter/sub-millimeter antenna which might resolve several bottlenecks in creating large precise mechanical structures. The paper also presents an overview of prospective space-qualified technologies of low-noise analogue front-end instrumentation for millimeter/sub-millimeter telescopes. Data handling and processing instrumentation is another key technological component of a sub-millimeter Space VLBI system. Requirements and possible implementation options for this instrumentation are described as an extrapolation of the current state-of-the-art Earth-based VLBI data transport and processing instrumentation. The paper also briefly discusses approaches to the interferometric baseline state vector determination and synchronisation and heterodyning system. The technology-oriented sections of the paper do not aim at presenting a complete set of technological solutions for sub-millimeter (terahertz) space-borne interferometers. Rather, in combination with the original ESA Voyage 2050 White Paper, it sharpens the case for the next generation microarcsecond-level imaging instruments and provides starting points for further in-depth technology trade-off studies.
  • A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set
    (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
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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.
  • Selective Dynamical Imaging of Interferometric Data
    (2022-05-01) Farah, Joseph; Galison, Peter; Akiyama, Kazunori; Bouman, Katherine L.; Bower, Geoffrey C.; Chael, Andrew; Fuentes, Antonio; Gómez, José L.; Honma, Mareki; Johnson, Michael D.; Kofuji, Yutaro; Marrone, Daniel P.; Moriyama, Kotaro; Narayan, Ramesh; Pesce, Dominic W.; Tiede, Paul; Wielgus, Maciek; Zhao, Guang Yao; 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; 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.; Chan, Chi Kwan; Chatterjee, Koushik; Kim, Dong Jin; Ramakrishnan, Venkatessh; Savolainen, Tuomas; Wagner, Jan; , Event Horizon Telescope Collaborat
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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.
  • A Universal Power-law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows
    (2022-05-01) Georgiev, Boris; Pesce, Dominic W.; Broderick, Avery E.; Wong, George N.; Dhruv, Vedant; Wielgus, Maciek; Gammie, Charles F.; Chan, Chi Kwan; Chatterjee, Koushik; Emami, Razieh; Mizuno, Yosuke; Gold, Roman; Fromm, Christian M.; Ricarte, Angelo; Yoon, Doosoo; Joshi, Abhishek V.; Prather, Ben; Cruz-Osorio, Alejandro; Johnson, Michael D.; Porth, Oliver; Olivares, Héctor; Younsi, Ziri; Rezzolla, Luciano; Vos, Jesse; Qiu, Richard; Nathanail, Antonios; Narayan, Ramesh; Chael, Andrew; Anantua, Richard; Moscibrodzka, Monika; Akiyama, Kazunori; Alberdi, Antxon; Alef, Walter; Algaba, Juan Carlos; 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; Kim, Dong Jin; Ramakrishnan, Venkatessh; Savolainen, Tuomas; Wagner, Jan; , Event Horizon Telescope Collaborat
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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.
  • The Variability of the Black Hole Image in M87 at the Dynamical Timescale
    (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
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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.