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1. Broadband Multi-wavelength Properties of M87 during the 2018 EHT Campaign including a Very High Energy Flaring Episode

Author: Algaba, J. C., Balokovic, M., Chandra, S., Cheong, W. Y., Cui, Y. Z., D'Ammando, F., Falcone, A. D., Ford, N. M., Giroletti, M., Goddi, C., Gurwell, M. A., Hada, K., Haggard, D., Jorstad, S., Kaur, A., Kawashima, T., Kerby, S., Kim, J. Y., Kino, M., Kravchenko, E. V., Lee, S. S., Lu, R. S., Markoff, S., Michail, J., Neilsen, J., Nowak, M. A., Principe, G., Ramakrishnan, V., Ripperda, B., Sasada, M., Savchenko, S. S., Sheridan, C., Akiyama, K., Alberdi, A., Alef, W., Anantua, R., Asada, K., Azulay, R., Bach, U., Baczko, A. -K., Ball, D., Bandyopadhyay, B., Barrett, J., Bauböck, M., Benson, B. A., Bintley, D., Blackburn, L., Blundell, R., Bouman, K. L., Bower, G. C., Boyce, H., Bremer, M., Brissenden, R., Britzen, S., Broderick, A. E., Broguiere, D., Bronzwaer, T., Bustamante, S., Carlstrom, J. E., Chael, A., Chan, C. -K., Chang, D. O., Chatterjee, K., Chatterjee, S., Chen, M. -T., Chen, Y., Cheng, X., Cho, I., Christian, P., Conroy, N. S., Conway, J. E., Crawford, T. M., Crew, G. B., Cruz-Osorio, A., Dahale, R., Davelaar, J., De Laurentis, M., Deane, R., Dempsey, J., Desvignes, G., Dexter, J., Dhruv, V., Dihingia, I. K., Doeleman, S. S., Dzib, S. A., Eatough, R. P., Emami, R., Falcke, H., Farah, J., Fish, V. L., Fomalont, E., Ford, H. A., Foschi, M., Fraga-Encinas, R., Freeman, W. T., Friberg, P., Fromm, C. M., Fuentes, A., Galison, P., Gammie, C. F., García, R., Gentaz, O., Georgiev, B., Gold, R., Gómez-Ruiz, A. I., Gómez, J. L., Gu, M., Hesper, R., Heumann, D., Ho, L. C., Ho, P., Honma, M., Huang, C. -W. L., Huang, L., Hughes, D. H., Ikeda, S., Impellizzeri, C. M. V., Inoue, M., Issaoun, S., James, D. J., Jannuzi, B. T., Janssen, M., Jeter, B., Jiang, W., Jiménez-Rosales, A., Johnson, M. D., Jones, A. C., Joshi, A. V., Jung, T., Karuppusamy, R., Keating, G. K., Kettenis, M., Kim, D. -J., Kim, J., Koay, J. Y., Kocherlakota, P., Kofuji, Y., Koch, P. M., Koyama, S., Kramer, C., Kramer, J. A., Kramer, M., Krichbaum, T. P., Kuo, C. -Y., La Bella, N., Levis, A., Li, Z., Lico, R., Lindahl, G., Lindqvist, M., Lisakov, M., Liu, J., Liu, K., Liuzzo, E., Lo, W. -P., Lobanov, A. P., Loinard, L., Lonsdale, C. J., Lowitz, A. E., MacDonald, N. R., Mao, J., Marchili, N., Marrone, D. P., Marscher, A. P., Martí-Vidal, I., Matsushita, S., Matthews, L. D., Medeiros, L., Menten, K. M., Mizuno, I., Mizuno, Y., Montgomery, J., Moran, J. M., Moriyama, K., Moscibrodzka, M., Mulaudzi, W., Müller, C., Müller, H., Mus, A., Musoke, G., Myserlis, I., Nagai, H., Nagar, N. M., Nair, D. G., Nakamura, M., Narayanan, G., Natarajan, I., Nathanail, A., Fuentes, S. Navarro, Ni, C., Oh, J., Okino, H., Olivares, H., Oyama, T., Özel, F., Palumbo, D. C. M., Paraschos, G. Filippos, Park, J., Parsons, H., Patel, N., Pen, U. -L., Pesce, D. W., Piétu, V., PopStefanija, A., Porth, O., Prather, B., Psaltis, D., Pu, H. -Y., Rao, R., Rawlings, M. G., Raymond, A. W., Rezzolla, L., Ricarte, A., Roelofs, F., Romero-Cañizales, C., Ros, E., Roshanineshat, A., Rottmann, H., Roy, A. L., Ruiz, I., Ruszczyk, C., Rygl, K. L. J., Sánchez, S., Sánchez-Argüelles, D., Sánchez-Portal, M., Satapathy, K., Savolainen, T., Schloerb, F. P., Schonfeld, J., Schuster, K. -F., Shao, L., Shen, Z., Small, D., Sohn, B. W., SooHoo, J., Salas, L. D. Sosapanta, Souccar, K., Stanway, J. S., Sun, H., Tazaki, F., Tetarenko, A. J., Tiede, P., Tilanus, R. P. J., Titus, M., Toma, K., Torne, P., Toscano, T., Traianou, E., Trent, T., Trippe, S., Turk, M., van Bemmel, I., van Langevelde, H. J., van Rossum, D. R., Vos, J., Wagner, J., Ward-Thompson, D., Wardle, J., Washington, J. E., Weintroub, J., Wharton, R., Wielgus, M., Wiik, K., Witzel, G., Wondrak, M. F., Wong, G. N., Wu, Q., Yadlapalli, N., Yamaguchi, P., Yfantis, A., Yoon, D., Young, A., Younsi, Z., Yu, W., Yuan, F., Yuan, Y. -F., Zensus, J. A., Zhang, S., Zhao, G. -Y., Zhao, S. -S., Bellazzini, R., Berenji, B., Bissaldi, E., Blandford, R. D., Bonino, R., Bruel, P., Cameron, R. A., Caraveo, P. A., Cavazzuti, E., Cheung, C. C., Ciprini, S., Orestano, P. Cristarella, Cutini, S., Di Lalla, N., Dinesh, A., Di Venere, L., Domínguez, A., Fegan, S. J., Franckowiak, A., Fukazawa, Y., Fusco, P., Gargano, F., Gasbarra, C., Germani, S., Giliberti, M., Grenier, I. A., Hays, E., Horan, D., Kuss, M., Larsson, S., Liodakis, I., Longo, F., Loparco, F., Lovellette, M. N., Maldera, S., Mazziotta, M. N., Mereu, I., Michelson, P. F., Mirabal, N., Mizuno, T., Monzani, M. E., Morselli, A., Negro, M., Omodei, N., Orlando, E., Persic, M., Rainò, S., Rani, B., Reimer, A., Reimer, O., Sánchez-Conde, M., Parkinson, P. M. Saz, Sgrò, C., Siskind, E. J., Spinelli, P., Suson, D. J., Tajima, H., Torres, D. F., Zaharijas, G., Aharonian, F., Benkhali, F. Ait, Aschersleben, J., Ashkar, H., Backes, M., Martins, V. Barbosa, Batzofin, R., Becherini, Y., Berge, D., Böttcher, M., Boisson, C., Bolmont, J., de Lavergne, M. de Bony, Borowska, J., Bouyahiaoui, M., Bradascio, F., Brose, R., Brown, A., Bruno, B., Bulik, T., Burger-Scheidlin, C., Casanova, S., Cecil, R., Celic, J., Cerruti, M., Chand, T., Chen, A., Chibueze, J., Chibueze, O., Czerny, T., Dainotti, M., Dubus, F., Dumm, J., D'Urso, G., Drouhin, A., Durouchoux, P., Fabbian, D., Franczak, D., Funk, M., Gabanyi, J., Gaggero, G., Garcia, N., Geiger, A., Giorgi, M. G., Gleeson, S., Gonzalez, S., Gauthier, G. T., Grasso, P., Hovatta, T., Hyman, J., Kaaret, C., Kirk, D., Lal, S., Lesch, T. M., Lohmann, K., Massaro, C., Mayer, M., Meintjes, P. J., Miral, E., Mirra, A., Neronov, J., Padovani, E., Paccagnella, F., Parisi, E., Piotrowska, A., Pohl, S., Puga, G., Ramirez, L. R., Reville, S., Rowell, D. S., Rudge, M., Rybka, G., Schlenstedt, M. S., Seo, E. S., Svirski, J., Taylor, J. R., Torres, F., Tsujimoto, K., Tosti, F., Volpi, S., Walraven, N. A., Welker, L., Zietkiewicz, M., Abdalla, G., Aleva, C., Benkhali, H. A. Ait, Aldous, M., Amin, M., Aschieri, M. A., de Deus, E., Santos, J. de Los, Fontanot, D., Jorfi, S., Levens, P., Zwart, A. E. E., Oliviero, S., Puglisi, D., Thiel, M., Zaharijas, C., Amaral, F., Boella, L., Holincheck, L., Queiroz, R., Sofue, H., Tellis, G., Wagner, G., Wierzcholska, A., Zacharias, M., Zdziarski, A. A., Zech, A., Zywucka, N., Abe, S., Abhir, J., Abhishek, A., Acciari, V. A., Aguasca-Cabot, A., Agudo, I., Aniello, T., Ansoldi, S., Antonelli, L. A., Engels, A. Arbet, Arcaro, C., Artero, M., Asano, K., Babic, A., de Almeida, U. Barres, Barrio, J. A., Batkovic, I., Bautista, A., Baxter, J., González, J. Becerra, Bednarek, W., Bernardini, E., Bernete, J., Berti, A., Besenrieder, J., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Bosnjak, Z., Bronzini, E., Burelli, I., Busetto, G., Campoy-Ordaz, A., Carosi, A., Carosi, R., Carretero-Castrillo, M., Castro-Tirado, A. J., Cerasole, D., Ceribella, G., Chai, Y., Cifuentes, A., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Amico, G., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., de Menezes, R., Delfino, M., Delgado, J., Mendez, C. Delgado, Di Pierro, F., Di Tria, R., Prester, D. Dominis, Donini, A., Dorner, D., Doro, M., Elsaesser, D., Escudero, J., Fariña, L., Fattorini, A., Foffano, L., Font, L., Fröse, S., Fukami, S., López, R. J. García, Garczarczyk, M., Gasparyan, S., Gaug, M., Paiva, J. G. Giesbrecht, Giglietto, N., Giordano, F., Gliwny, P., Godinovic, N., Gradetzke, T., Grau, R., Green, D., Green, J. G., Günther, P., Hadasch, D., Hahn, A., Hassan, T., Heckmann, L., Llorente, J. Herrera, Hrupec, D., Imazawa, R., Ishio, K., Martínez, I. Jiménez, Jormanainen, J., Kayanoki, T., Kerszberg, D., Kluge, G. W., Kobayashi, Y., Kouch, P. M., Kubo, H., Kushida, J., Laínez, M., Lamastra, A., Leone, F., Lindfors, E., Lombardi, S., López-Coto, R., López-Moya, M., López-Oramas, A., Loporchio, S., Lorini, A., Lyard, E., Fraga, B. Machado de Oliveira, Majumdar, P., Makariev, M., Maneva, G., Manganaro, M., Mangano, S., Mannheim, K., Mariotti, M., Martínez, M., Martínez-Chicharro, M., Mas-Aguilar, A., Mazin, D., Menchiari, S., Mender, S., Miceli, D., Miener, T., Miranda, J. M., Mirzoyan, R., González, M. Molero, Molina, E., Mondal, H. A., Moralejo, A., Morcuende, D., Nakamori, T., Nanci, C., Neustroev, V., Nickel, L., Rosillo, M. Nievas, Nigro, C., Nikolic, L., Nilsson, K., Nishijima, K., Ekoume, T. Njoh, Noda, K., Nozaki, S., Ohtani, Y., Okumura, A., Otero-Santos, J., Paiano, S., Paneque, D., Paoletti, R., Paredes, J. M., Peresano, M., Pihet, M., Pirola, G., Podobnik, F., Moroni, P. G. Prada, Prandini, E., Priyadarshi, C., Ribó, M., Rico, J., Righi, C., Sahakyan, N., Saito, T., Saturni, F. G., Schmidt, K., Schmuckermaier, F., Schubert, J. L., Schweizer, T., Sciaccaluga, A., Silvestri, G., Sitarek, J., Sliusar, V., Sobczynska, D., Spolon, A., Stamerra, A., Strišković, J., Strom, D., Strzys, M., Suda, Y., Suutarinen, S., Takahashi, M., Takeishi, R., Tavecchio, F., Temnikov, P., Terauchi, K., Terzic, T., Teshima, M., Truzzi, S., Tutone, A., Ubach, S., van Scherpenberg, J., Acosta, M. Vazquez, Ventura, S., Verna, G., Viale, I., Vigorito, C. F., Vitale, V., Vovk, I., Walter, R., Will, M., Wunderlich, C., Yamamoto, T., Acharyya, A., Adams, C. B., Bangale, P., Bartkoske, J. T., Benbow, W., Christiansen, J. L., Duerr, A., Errando, M., Feng, Q., Foote, G. M., Fortson, L., Furniss, A., Hanlon, W., Hervet, O., Hinrichs, C. E., Holder, J., Humensky, T. B., Jin, W., Johnson, M. N., Kaaret, P., Kertzman, M., Kieda, D., Kleiner, T. K., Korzoun, N., Krennrich, F., Kumar, S., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E., Millard, M. J., Mooney, C. L., Moriarty, P., Mukherjee, R., Ning, W., O'Brien, S., Ong, R. A., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Ryan, J. L., Sadeh, I., Saha, L., Santander, M., Sembroski, G. H., Shang, R., Splettstoesser, M., Talluri, A. K., Tucci, J. V., Valverde, J., Vassiliev, V. V., Williams, D. A., Wong, S. L., Chen, Z., Cui, L., Hirota, T., Li, B., Li, G., Liu, Q., Liu, X., Liu, Z., Ma, J., Niinuma, K., Ro, H., Sakai, N., Sawada-Satoh, S., Wajima, K., Wang, J., Wang, N., Xia, B., Yan, H., Yonekura, Y., Zhang, H., Zhao, R., Zhong, W., group, The Event Horizon Telescope - Multi-wavelength science working, Collaboration, The Event Horizon Telescope, Collaboration, The Fermi Large Area Telescope, Collaboration, H. E. S. S., Collaboration, MAGIC, Collaboration, VERITAS, and Collaboration, EAVN
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: The nearby elliptical galaxy M87 contains one of the only two supermassive black holes whose emission surrounding the event horizon has been imaged by the Event Horizon Telescope (EHT). In 2018, more than two dozen multi-wavelength (MWL) facilities (from radio to gamma-ray energies) took part in the second M87 EHT campaign. The goal of this extensive MWL campaign was to better understand the physics of the accreting black hole M87*, the relationship between the inflow and inner jets, and the high-energy particle acceleration. Understanding the complex astrophysics is also a necessary first step towards performing further tests of general relativity. The MWL campaign took place in April 2018, overlapping with the EHT M87* observations. We present a new, contemporaneous spectral energy distribution (SED) ranging from radio to very high energy (VHE) gamma-rays, as well as details of the individual observations and light curves. We also conduct phenomenological modelling to investigate the basic source properties. We present the first VHE gamma-ray flare from M87 detected since 2010. The flux above 350 GeV has more than doubled within a period of about 36 hours. We find that the X-ray flux is enhanced by about a factor of two compared to 2017, while the radio and millimetre core fluxes are consistent between 2017 and 2018. We detect evidence for a monotonically increasing jet position angle that corresponds to variations in the bright spot of the EHT image. Our results show the value of continued MWL monitoring together with precision imaging for addressing the origins of high-energy particle acceleration. While we cannot currently pinpoint the precise location where such acceleration takes place, the new VHE gamma-ray flare already presents a challenge to simple one-zone leptonic emission model approaches, and emphasises the need for combined image and spectral modelling., Comment: 46 pages, 23 figures, accepted by Astronomy & Astrophysics on August. 29, 2024
Published: 2024

2. Ordered magnetic fields around the 3C 84 central black hole

Author: Paraschos, G. F., Kim, J. -Y., Wielgus, M., Röder, J., Krichbaum, T. P., Ros, E., Agudo, I., Myserlis, I., Moscibrodzka, M., Traianou, E., Zensus, J. A., Blackburn, L., Chan, C. -K., Issaoun, S., Janssen, M., Johnson, M. D., Fish, V. L., Akiyama, K., Alberdi, A., Alef, W., Algaba, J. C., Anantua, R., Asada, K., Azulay, R., Bach, U., Baczko, A. -K., Ball, D., Baloković, M., Barrett, J., Bauböck, M., Benson, B. A., Bintley, D., Blundell, R., Bouman, K. L., Bower, G. C., Boyce, H., Bremer, M., Brinkerink, C. D., Brissenden, R., Britzen, S., Broderick, A. E., Broguiere, D., Bronzwaer, T., Bustamante, S., Byun, D. -Y., Carlstrom, J. E., Ceccobello, C., Chael, A., Chang, D. O., Chatterjee, K., Chatterjee, S., Chen, M. T., Chen, Y., Cheng, X., Cho, I., Christian, P., Conroy, N. S., Conway, J. E., Cordes, J. M., Crawford, T. M., Crew, G. B., Cruz-Osorio, A., Cui, Y., Dahale, R., Davelaar, J., De Laurentis, M., Deane, R., Dempsey, J., Desvignes, G., Dexter, J., Dhruv, V., Doeleman, S. S., Dougal, S., Dzib, S. A., Eatough, R. P., Emami, R., Falcke, H., Farah, J., Fomalont, E., Ford, H. A., Foschi, M., Fraga-Encinas, R., Freeman, W. T., Friberg, P., Fromm, C. M., Fuentes, A., Galison, P., Gammie, C. F., García, R., Gentaz, O., Georgiev, B., Goddi, C., Gold, R., Gómez-Ruiz, A. I., Gómez, J. L., Gu, M., Gurwell, M., Hada, K., Haggard, D., Haworth, K., Hecht, M. H., Hesper, R., Heumann, D., Ho, L. C., Ho, P., Honma, M., Huang, C. L., Huang, L., Hughes, D. H., Ikeda, S., Impellizzeri, C. M. V., Inoue, M., James, D. J., Jannuzi, B. T., Jeter, B., Jaing, W., Jiménez-Rosales, A., Jorstad, S., Joshi, A. V., Jung, T., Karami, M., Karuppusamy, R., Kawashima, T., Keating, G. K., Kettenis, M., Kim, D. -J., Kim, J., Kino, M., Koay, J. Y., Kocherlakota, P., Kofuji, Y., Koch, P. M., Koyama, S., Kramer, C., Kramer, J. A., Kramer, M., Kuo, C. -Y., La Bella, N., Lauer, T. R., Lee, D., Lee, S. -S., Leung, P. K., Levis, A., Li, Z., Lico, R., Lindahl, G., Lindqvist, M., Lisakov, M., Liu, J., Liu, K., Liuzzo, E., Lo, W. -P., Lobanov, A. P., Loinard, L., Lonsdale, C. J., Lowitz, A. E., Lu, R. -S., MacDonald, N. R., Mao, J., Marchili, N., Markoff, S., Marrone, D. P., Marscher, A. P., Martí-Vidal, I., Matsushita, S., Matthews, L. D., Medeiros, L., Menten, K. M., Michalik, D., Mizuno, I., Mizuno, Y., Moran, J. M., Moriyama, K., Mulaudzi, W., Müller, C., Müller, H., Mus, A., Musoke, G., Nadolski, A., Nagai, H., Nagar, N. M., Nakamura, M., Narayanan, G., Natarajan, I., Nathanail, A., Fuentes, S. Navarro, Neilsen, J., Neri, R., Ni, C., Noutsos, A., Nowak, M. A., Oh, J., Okino, H., Olivares, H., Ortiz-León, G. N., Oyama, T., Özel, F., Palumbo, D. C. M., Park, J., Parsons, H., Patel, N., Pen, U. -L., Piétu, V., Plambeck, R., PopStefanija, A., Porth, O., Pötzl, F. M., Prather, B., Preciado-López, J. A., Psaltis, D., Pu, H. -Y., Ramakrishnan, V., Rao, R., Rawlings, M. G., Raymond, A. W., Rezzolla, L., Ricarte, A., Ripperda, B., Roelofs, F., Rogers, A., Romero-Cañizales, C., Roshanineshat, A., Rottmann, H., Roy, A. L., Ruiz, I., Ruszczyk, C., Rygl, K. L. J., Sánchez, S., Sánchez-Argüelles, D., Sánchez-Portal, M., Sasada, M., Satapathy, K., Savolainen, T., Schloerb, F. P., Schonfeld, J., Schuster, K., Shao, L., Shen, Z., Small, D., Sohn, B. W., SooHoo, J., Salas, L. D. Sosapanta, Souccar, K., Sun, H., Tazaki, F., Tetarenko, A. J., Tiede, P., Tilanus, R. P. J., Titus, M., Torne, P., Toscano, T., Trent, T., Trippe, S., Turk, M., van Bemmel, I., van Langevelde, H. J., van Rossum, D. R., Vos, J., Wagner, J., Ward-Thompson, D., Wardle, J., Washington, J. E., Weintroub, J., Wharton, R., Wiik, K., Witzel, G., Wondrak, M. F., Wong, G. N., Wu, Q., Yadlapalli, N., Yamaguchi, P., Yfantis, A., Yoon, D., Young, A., Young, K., Younsi, Z., Yu, W., Yuan, F., Yuan, Y. -F., Zhang, S., Zhao, G. Y., and Zhao, S. -S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: 3C84 is a nearby radio source with a complex total intensity structure, showing linear polarisation and spectral patterns. A detailed investigation of the central engine region necessitates the use of VLBI above the hitherto available maximum frequency of 86GHz. Using ultrahigh resolution VLBI observations at the highest available frequency of 228GHz, we aim to directly detect compact structures and understand the physical conditions in the compact region of 3C84. We used EHT 228GHz observations and, given the limited (u,v)-coverage, applied geometric model fitting to the data. We also employed quasi-simultaneously observed, multi-frequency VLBI data for the source in order to carry out a comprehensive analysis of the core structure. We report the detection of a highly ordered, strong magnetic field around the central, SMBH of 3C84. The brightness temperature analysis suggests that the system is in equipartition. We determined a turnover frequency of $\nu_m=(113\pm4)$GHz, a corresponding synchrotron self-absorbed magnetic field of $B_{SSA}=(2.9\pm1.6)$G, and an equipartition magnetic field of $B_{eq}=(5.2\pm0.6)$G. Three components are resolved with the highest fractional polarisation detected for this object ($m_\textrm{net}=(17.0\pm3.9)$%). The positions of the components are compatible with those seen in low-frequency VLBI observations since 2017-2018. We report a steeply negative slope of the spectrum at 228GHz. We used these findings to test models of jet formation, propagation, and Faraday rotation in 3C84. The findings of our investigation into different flow geometries and black hole spins support an advection-dominated accretion flow in a magnetically arrested state around a rapidly rotating supermassive black hole as a model of the jet-launching system in the core of 3C84. However, systematic uncertainties due to the limited (u,v)-coverage, however, cannot be ignored., Comment: 15 pages, 6 figures, published in A&A
Published: 2024
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3. Interferometric Monitoring of Gamma-ray Bright AGNs: Measuring the Magnetic Field Strength of 4C +29.45

Author: Kang, S., Lee, S. -S., Hodgson, J., Algaba, J. -C., Lee, J. W., Kim, J. -Y., Park, J., Kino, M., Kim, D., and Trippe, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We present the results of multi-epoch, multi-frequency monitoring of a blazar 4C +29.45, which was regularly monitored as part of the Interferometric Monitoring of GAmma-ray Bright Active Galactic Nuclei (iMOGABA) program - a key science program of the Korean Very long baseline interferometry Network (KVN). Observations were conducted simultaneously at 22, 43, 86, and 129 GHz during the 4 years from 5 December 2012 to 28 December 2016. We also used additional data from the 15 GHz Owens Valley Radio Observatory (OVRO) monitoring program. From the 15 GHz light curve, we estimated the variability time scales of the source during several radio flux enhancements. We found that the source experienced 6 radio flux enhancements with variability time scales of 9-187 days during the observing period, yielding corresponding variability Doppler factors of 9-27. From the multi-frequency simultaneous KVN observations, we were able to obtain accurate radio spectra of the source and hence to more precisely measure the turnover frequencies $\nu_{\rm r}$ of synchrotron self-absorbed (SSA) emission with a mean value of $\nu_{rm r}$ = 28.9 GHz. Using jet geometry assumptions, we estimated the size of the emitting region at the turnover frequency. We found that the equipartition magnetic field strength is up to two orders of magnitudes higher than the SSA magnetic field strength (0.001-0.1 G). This is consistent with the source being particle dominated. We performed a careful analysis of the systematic errors related to making these estimations. From the results, we concluded that the equipartition region locates upstream the SSA region., Comment: 19 pages, 8 figures, 10 tables, accepted for publication in A&A
Published: 2021
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4. Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign

Author: Algaba, J. C., Anczarski, J., Asada, K., Balokovic, M., Chandra, S., Cui, Y. -Z., Falcone, A. D., Giroletti, M., Goddi, C., Hada, K., Haggard, D., Jorstad, S., Kaur, A., Kawashima, T., Keating, G., Kim, J. -Y., Kino, M., Komossa, S., Kravchenko, E. V., Krichbaum, T. P., Lee, S. -S., Lu, R. -S., Lucchini, M., Markoff, S., Neilsen, J., Nowak, M. A., Park, J., Principe, G., Ramakrishnan, V., Reynolds, M. T., Sasada, M., Savchenko, S. S., Williamson, K. E., Collaboration, The Event Horizon Telescope, Collaboration, The Fermi Large Area Telescope, Collaboration, H. E. S. S., Collaboration, MAGIC, Collaboration, VERITAS, and Collaboration, EAVN
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract: In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass approximately 6.5 x 10^9 M_solar. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous gamma-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the gamma-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded., Comment: 43 pages, 19 figures, 10 tables; complete author list available in manuscript; The Astrophysical Journal Letters, 2021, 911, L11; publication doi: 3847/2041-8213/abef71, data doi: 10.25739/mhh2-cw46
Published: 2021
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5. White Paper on East Asian Vision for mm/submm VLBI: Toward Black Hole Astrophysics down to Angular Resolution of 1~R$_{S}$

Author: Asada, K., Kino, M., Honma, M., Hirota, T., Lu, R. -S., Inoue, M., Sohn, B. -W., Shen, Z. -Q., Ho, P. T. P., Akiyama, K., Algaba, J-C., An, T., Bower, G., Byun, D-Y., Dodson, R., Doi, A., Edwards, P. G., Fujisawa, K., Gu, M-F., Hada, K., Hagiwara, Y., Jaroenjittichai, P., Jung, T., Kawashima, T., Koyama, S., Lee, S-S., Matsushita, S., Nagai, H., Nakamura, M., Niinuma, K., Phillips, C., Park, J-H., Pu, H-Y., Ro, H-W., Stevens, J., Trippe, S., Wajima, K., and Zhao, G-Y.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: This White Paper details the intentions and plans of the East Asian Very Long Baseline Interferometry (VLBI) community for pushing the frontiers of millimeter/submillimeter VLBI. To this end, we shall endeavor to actively promote coordinated efforts in the East Asia region. Our goal is to establish firm collaborations among the East Asia VLBI community in partnership with related institutes in North America and Europe and to expand existing global mm/submm VLBI arrays for (a) exploring the vicinity of black holes with an ultimate angular resolution down to 1~R$_{S}$ (Schwarzschild radius) and (b) investigating the dynamics of circumstellar gas in star-forming regions and late-type stars, and circumnuclear gas around active galactic nuclei (AGNs). In the first half of this White Paper, we highlight scientific accomplishments of the East Asia (EA) VLBI community. Various VLBI research results on M87, Sgr A*, blazars, narrow-line Seyfert~1 galaxies, and compact symmetric objects are described, and future visions of our VLBI science are briefly presented. Maser science of star formation, stellar evolution, and physics of accretion disks around AGNs are also discussed. A new vision for conducting multi-transition maser studies using mm/submm VLBI together with the Atacama Large Millimeter/Submillimeter Array (ALMA) is described. In the second half of this White Paper, we describe the EA community's vision for using mm/submm VLBI arrays in the framework or extended version of the Event Horizon Telescope (EHT) and the Global Millimeter VLBI Array (GMVA). The accomplishment of the aforementioned goal will maximize the overall scientific outcomes of mm/submm VLBI in the world., Comment: 93 pages, 54 figures. White Paper from East Asia VLBI community
Published: 2017

6. Multiple simultaneous Gamma-ray emission sites in 3C 84

Author: Hodgson, Jeffrey A., Lee, S. S., Rani, B., and Algaba, J. C.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The mis-aligned active galactic nuclei (AGN), 3C\,84, has been observed approximately monthly at four frequencies simultaneously (22\,GHz -- 129\,GHz) on the Korean VLBI Network (KVN) since 2013 as part of the interferometric monitoring of $\gamma$-ray bright AGN (iMOGABA) program. 3C\,84 is known to have to sites of bright radio emission, with the first thought to be near the central super-massive black hole and the second in a slowly moving emission feature, several milliarcseconds south of the core. Analysis of this data suggests that the highly variable Gamma-ray emission originates near the SMBH and the slowly rising $\gamma$-ray emission originates in the slow moving feature., Comment: Submitted to the proceedings of the 13th EVN Symposium and Users Meeting held in St. Petersburg, Russia, 20-23 September 2016. Contributed poster: 4 pages, 1 figure
Published: 2016

7. Ordered magnetic fields around the 3C 84 central black hole

Author: Paraschos, G. F., primary, Kim, J.-Y., additional, Wielgus, M., additional, Röder, J., additional, Krichbaum, T. P., additional, Ros, E., additional, Agudo, I., additional, Myserlis, I., additional, Moscibrodzka, M., additional, Traianou, E., additional, Zensus, J. A., additional, Blackburn, L., additional, Chan, C.-K., additional, Issaoun, S., additional, Janssen, M., additional, Johnson, M. D., additional, Fish, V. L., additional, Akiyama, K., additional, Alberdi, A., additional, Alef, W., additional, Algaba, J. C., additional, Anantua, R., additional, Asada, K., additional, Azulay, R., additional, Bach, U., additional, Baczko, A.-K., additional, Ball, D., additional, Baloković, M., additional, Barrett, J., additional, Bauböck, M., additional, Benson, B. A., additional, Bintley, D., additional, Blundell, R., additional, Bouman, K. L., additional, Bower, G. C., additional, Boyce, H., additional, Bremer, M., additional, Brinkerink, C. D., additional, Brissenden, R., additional, Britzen, S., additional, Broderick, A. E., additional, Broguiere, D., additional, Bronzwaer, T., additional, Bustamante, S., additional, Byun, D.-Y., additional, Carlstrom, J. E., additional, Ceccobello, C., additional, Chael, A., additional, Chang, D. O., additional, Chatterjee, K., additional, Chatterjee, S., additional, Chen, M. T., additional, Chen, Y., additional, Cheng, X., additional, Cho, I., additional, Christian, P., additional, Conroy, N. S., additional, Conway, J. E., additional, Cordes, J. M., additional, Crawford, T. M., additional, Crew, G. B., additional, Cruz-Osorio, A., additional, Cui, Y., additional, Dahale, R., additional, Davelaar, J., additional, De Laurentis, M., additional, Deane, R., additional, Dempsey, J., additional, Desvignes, G., additional, Dexter, J., additional, Dhruv, V., additional, Doeleman, S. S., additional, Dougal, S., additional, Dzib, S. A., additional, Eatough, R. P., additional, Emami, R., additional, Falcke, H., additional, Farah, J., additional, Fomalont, E., additional, Ford, H. A., additional, Foschi, M., additional, Fraga-Encinas, R., additional, Freeman, W. T., additional, Friberg, P., additional, Fromm, C. M., additional, Fuentes, A., additional, Galison, P., additional, Gammie, C. F., additional, García, R., additional, Gentaz, O., additional, Georgiev, B., additional, Goddi, C., additional, Gold, R., additional, Gómez-Ruiz, A. I., additional, Gómez, J. L., additional, Gu, M., additional, Gurwell, M., additional, Hada, K., additional, Haggard, D., additional, Haworth, K., additional, Hecht, M. H., additional, Hesper, R., additional, Heumann, D., additional, Ho, L. C., additional, Ho, P., additional, Honma, M., additional, Huang, C. L., additional, Huang, L., additional, Hughes, D. H., additional, Ikeda, S., additional, Impellizzeri, C. M. V., additional, Inoue, M., additional, James, D. J., additional, Jannuzi, B. T., additional, Jeter, B., additional, Jaing, W., additional, Jiménez-Rosales, A., additional, Jorstad, S., additional, Joshi, A. V., additional, Jung, T., additional, Karami, M., additional, Karuppusamy, R., additional, Kawashima, T., additional, Keating, G. K., additional, Kettenis, M., additional, Kim, D.-J., additional, Kim, J., additional, Kino, M., additional, Koay, J. Y., additional, Kocherlakota, P., additional, Kofuji, Y., additional, Koch, P. M., additional, Koyama, S., additional, Kramer, C., additional, Kramer, J. A., additional, Kramer, M., additional, Kuo, C.-Y., additional, La Bella, N., additional, Lauer, T. R., additional, Lee, D., additional, Lee, S.-S., additional, Leung, P. K., additional, Levis, A., additional, Li, Z., additional, Lico, R., additional, Lindahl, G., additional, Lindqvist, M., additional, Lisakov, M., additional, Liu, J., additional, Liu, K., additional, Liuzzo, E., additional, Lo, W.-P., additional, Lobanov, A. P., additional, Loinard, L., additional, Lonsdale, C. J., additional, Lowitz, A. E., additional, Lu, R.-S., additional, MacDonald, N. R., additional, Mao, J., additional, Marchili, N., additional, Markoff, S., additional, Marrone, D. P., additional, Marscher, A. P., additional, Martí-Vidal, I., additional, Matsushita, S., additional, Matthews, L. D., additional, Medeiros, L., additional, Menten, K. M., additional, Michalik, D., additional, Mizuno, I., additional, Mizuno, Y., additional, Moran, J. M., additional, Moriyama, K., additional, Mulaudzi, W., additional, Müller, C., additional, Müller, H., additional, Mus, A., additional, Musoke, G., additional, Nadolski, A., additional, Nagai, H., additional, Nagar, N. M., additional, Nakamura, M., additional, Narayanan, G., additional, Natarajan, I., additional, Nathanail, A., additional, Navarro Fuentes, S., additional, Neilsen, J., additional, Neri, R., additional, Ni, C., additional, Noutsos, A., additional, Nowak, M. A., additional, Oh, J., additional, Okino, H., additional, Olivares, H., additional, Ortiz-León, G. N., additional, Oyama, T., additional, Özel, F., additional, Palumbo, D. C. M., additional, Park, J., additional, Parsons, H., additional, Patel, N., additional, Pen, U.-L., additional, Piétu, V., additional, Plambeck, R., additional, PopStefanija, A., additional, Porth, O., additional, Pötzl, F. M., additional, Prather, B., additional, Preciado-López, J. A., additional, Psaltis, D., additional, Pu, H.-Y., additional, Ramakrishnan, V., additional, Rao, R., additional, Rawlings, M. G., additional, Raymond, A. W., additional, Rezzolla, L., additional, Ricarte, A., additional, Ripperda, B., additional, Roelofs, F., additional, Rogers, A., additional, Romero-Cañizales, C., additional, Roshanineshat, A., additional, Rottmann, H., additional, Roy, A. L., additional, Ruiz, I., additional, Ruszczyk, C., additional, Rygl, K. L. J., additional, Sánchez, S., additional, Sánchez-Argüelles, D., additional, Sánchez-Portal, M., additional, Sasada, M., additional, Satapathy, K., additional, Savolainen, T., additional, Schloerb, F. P., additional, Schonfeld, J., additional, Schuster, K., additional, Shao, L., additional, Shen, Z., additional, Small, D., additional, Sohn, B. W., additional, SooHoo, J., additional, Sosapanta Salas, L. D., additional, Souccar, K., additional, Sun, H., additional, Tazaki, F., additional, Tetarenko, A. J., additional, Tiede, P., additional, Tilanus, R. P. J., additional, Titus, M., additional, Torne, P., additional, Toscano, T., additional, Trent, T., additional, Trippe, S., additional, Turk, M., additional, van Bemmel, I., additional, van Langevelde, H. J., additional, van Rossum, D. R., additional, Vos, J., additional, Wagner, J., additional, Ward-Thompson, D., additional, Wardle, J., additional, Washington, J. E., additional, Weintroub, J., additional, Wharton, R., additional, Wiik, K., additional, Witzel, G., additional, Wondrak, M. F., additional, Wong, G. N., additional, Wu, Q., additional, Yadlapalli, N., additional, Yamaguchi, P., additional, Yfantis, A., additional, Yoon, D., additional, Young, A., additional, Young, K., additional, Younsi, Z., additional, Yu, W., additional, Yuan, F., additional, Yuan, Y.-F., additional, Zhang, S., additional, Zhao, G. Y., additional, and Zhao, S.-S., additional
Published: 2024
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8. Measuring Mass Accretion Rate onto the Supermassive Black Hole in M 87 Using Faraday Rotation Measure with the Submillimeter Array

Author: Kuo, C. Y., Asada, K., Rao, R., Nakamura, M., Algaba, J. C., Liu, H. B., Inoue, M., Koch, P. M., Ho, P. T. P., Matsushita, S., Pu, H. -Y., Akiyama, K., Nishioka, H., and Pradel, N.
Subjects: Astrophysics - Galaxy Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the first constraint on Faraday rotation measure (RM) at submillimeter wavelengths for the nucleus of M 87. By fitting the polarization position angles ($\chi$) observed with the SMA at four independent frequencies around $\sim$230 GHz and interpreting the change in $\chi$ as a result of \emph{external} Faraday rotation associated with accretion flow, we determine the rotation measure of the M 87 core to be between $-$7.5$\times$10$^{5}$ and 3.4$\times$10$^{5}$ rad/m$^{2}$. Assuming a density profile of the accretion flow that follows a power-law distribution and a magnetic field that is ordered, radial, and has equipartition strength, the limit on the rotation measure constrains the mass accretion rate $\dot{M}$ to be below 9.2$\times$10$^{-4}$ M$_{\odot}$~yr$^{-1}$ at a distance of 21 Schwarzchild radii from the central black hole. This value is at least two orders of magnitude smaller than the Bondi accretion rate, suggesting significant suppression of the accretion rate in the inner region of the accretion flow. Consequently, our result disfavors the classical \emph{advection dominated accretion flow} (ADAF) and prefers the \emph{adiabatic inflow-outflow solution} (ADIOS) or \emph{convection-dominated accretion flow} (CDAF) for the hot accretion flow in M 87., Comment: 11 pages, 4 figures, accepted by ApJL
Published: 2014
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9. Greenland Telescope (GLT) Project: 'A Direct Confirmation of Black Hole with Submillimeter VLBI'

Author: Nakamura, M., Algaba, J. -C., Asada, K., Chen, B., Chen, M. -T., Han, J., Ho, P. H. P., Hsieh, S. -N., Huang, T., Inoue, M., Koch, P., Kuo, C. -Y., Martin-Cocher, P., Matsushita, S., Meyer-Zhao, Z., Nishioka, H., Nystom, G., Pradel, N., Pu, H. -Y., Raffin, P., Shen, H. -Y., Tseng, C. -Y., and Team, the Greenland Telescope Project
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The GLT project is deploying a new submillimeter (submm) VLBI station in Greenland. Our primary scientific goal is to image a shadow of the supermassive black hole (SMBH) of six billion solar masses in M87 at the center of the Virgo cluster of galaxies. The expected SMBH shadow size of 40-50 $\mu$as requires superbly high angular resolution, suggesting that the submm VLBI would be the only way to obtain the shadow image. The Summit station in Greenland enables us to establish baselines longer than 9,000 km with ALMA in Chile and SMA in Hawaii as well as providing a unique $u$--$v$ coverage for imaging M87. Our VLBI network will achieve a superior angular resolution of about 20 $\mu$as at 350 GHz, corresponding to $\sim2.5$ times of the Schwarzschild radius of the supermassive black hole in M87. We have been monitoring the atmospheric opacity at 230 GHz since August. 2011; we have confirmed the value on site during the winter season is comparable to the ALMA site thanks to high altitude of 3,200 m and low temperature of $-50\degr$C. We will report current status and future plan of the GLT project towards our expected first light on 2015--2016., Comment: 4 pages, 5 figures; to appear in the conference proceedings of "Innermost Regions of Relativistic Jets and Their Magnetic Fields", June 10-14, 2013, Granada, Spain
Published: 2013
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10. Helical magnetic fields in the M87 jet at arc-second scales

Author: Algaba, J. C., Asada, K., and Nakamura, M.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We investigate the magnetic field configuration of the M87 jet at arc-second scales by using archival polarimetric VLA data at 8, 15, 22 and 43 GHz. By stacking images over three years in order to enhance the sensitivity, we reveal, for the first time, systematic transverse gradients of the Faraday rotation measure in several knots along the jet. Combining this result with polarization properties and the dynamics of the jet, we suggest the magnetic structure in several knots at kiloparsec scales consists of a systematically wrapped, tightly wound helical configuration. Our analysis brings us a new paradigm where the M87 jet is a fundamentally current carrying system produced in the vicinity of the supermassive black hole, transferring a huge amount of the electromagnetic energy over the host galaxy scale., Comment: Reanalysis with new approach and further discussion in arXiv:1603.08437
Published: 2013

11. High Frequency VLBI Rotation Measure of 8 AGN

Author: Algaba, J. C.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We have studied Very Long Baseline Array (VLBA) polarimetric observations of 8 sources including quasars and BL Lacs at 12, 15, 22, 24 and 43 GHz and high frequency rotation measure ($RM$) maps are presented. We find typical values for the $RM$ in the VLBI core of several thousand rad/m$^2$, which are higher than values in the literature at lower frequencies. Assuming a dependence of the form $RM\propto \nu^a$, we obtain an average value of $a=3.6\pm1.3$, which is larger than that expected by theoretical considerations. Rotation measures are detected in the jet of only two sources and we find that only 0906+430 (and possibly 1633+382) show indications of a robust gradient. We discuss the Faraday--corrected polarization properties of the sources. Our interpretation supports the presence of helical magnetic fields with new, unresolved, components affecting the intrinsic direction of polarization close to the base of the jet of some objects., Comment: 14 pages, 2 tables, 9 figures. Accepted for publication in MNRAS
Published: 2012
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12. Probing Helical Magnetic Fields in AGN by Rotation Measure Gradients Studies

Author: Algaba, J. C.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: One of the tools that can provide evidence about the existence of helical magnetic fields in AGN is the observation of rotation measure gradients across the jet. Such observations have been previously made successfully, proving that such gradients are far from being rare, but common and typically persistent over several years, although some of them may show a reversal in the direction along the jet. Further studies of rotation measure gradients can help us in our understanding of the magnetic field properties and structure in the base of the jets. We studied Very Long Baseline Array (VLBA) polarimetric observations of 8 sources consistent of some quasars and BL Lacs at 12, 15, 22, 24 and 43 GHz and we find that all but two sources show indications of rotation measure gradients, either parallel or perpendicular to the jet. We interpret gradients perpendicular to the jet as indications of the change of the line of sight of the magnetic field due to its helicity, and gradients parallel to the jet as the decrease of magnetic field strength and/or electron density as we move along the jet. When comparing our results with the literature, we find tentative evidence of a rotation measure gradient flip, which can be explained as a change of the pitch angle or jet bending., Comment: 4 pages, 2 figures. Contribution for the Proceedings of HEPRO3 (Barcelona, 27 June - 1 July 2011). To be published on the International Journal of Modern Physics Conference Series, edited by J.M. Paredes, M. Rib\'o, F.A. Aharonian and G.E. Romero
Published: 2011
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13. Search for correlations between the optical and radio polarization of AGNs II: VLBA polarization data at 12+15+22+24+43 GHz

Author: Algaba, J. C., Gabuzda, D. C., and Smith, P. S.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Previous research showed most BL Lac objects and some quasars have aligned VLBI-core and optical polarizations, although some of the AGNs also showed no obvious relationship between VLBI-core and optical polarization angles. This may indicate that some AGNs have co-spatial regions of optical and radio emission, while others do not. Another possibility is that some of the VLBI cores had Faraday rotations of several tens of thousand of rad/m^2, which were not properly fit using the three-frequency data due to n\pi ambiguities in the observed polarization angles, leading to incorrect subtraction of the effects of the core Faraday rotation, and so incorrect intrinsic radio polarization angles \chi_0. We obtained additional 12+15+22+24+43GHz plus optical observations for 8 of 40 AGNs previously considered. Our results indicate that, although some VLBI radio cores have comparatively high rotation measures, this alone cannot explain the misalignments found between the radio core and optical VLBI polarization angles, \Delta\chi = |\chi_opt - \chi_0|. Comparison between \Delta\chi and (i) the orientation of \chi_0 relative to the jet direction, (ii) the degree of polarization of the core, (iii) a depolarization factor, (iv) the core rotation measures and (v) the core magnetic fields 1pc from the jet base do not yield evidence for any correlations between these properties. There is some evidence that the maximum observed \Delta\chi tends to decrease as the core-region magnetic field increases, suggesting that misalignments in \Delta\chi could be associated in part with relatively low core magnetic fields. Thus, although the overall distribution of \Delta\chi for all 40 sources in our sample does show a significant peak at \Delta\chi\sim0, it remains unclear what distinguishes these AGN cores from those showing appreciable misalignment between optical and VLBI-core polarization position angles., Comment: 13 pages, 5 figures, 9 tables. Accepted for publication in MNRAS
Published: 2011
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14. Hints of High Core Faraday Rotations from a Joint Analysis of VLBA and Optical Polarization Data

Author: Algaba, J. C., Gabuzda, D. C., and Smith, P. S.
Subjects: Astrophysics - Galaxy Astrophysics
Abstract: Although the continua of radio-loud Active Galactic Nuclei (AGN) are typically dominated by synchrotron radiation over virtually the entire spectrum, it is not clear whether the radio and higher-frequency emission originate in the same or different parts of the jet. Several different radio--optical correlations based on polarization data have been found recently, suggesting that the optical and radio polarization may be closely related, and that the corresponding emission regions may be cospatial (Gabuzda et. al2006, Jorstad et al. 2007, D'Arcangelo et al. 2007) Our joint analysis of optical and VLBA polarization data for a sample of about 40 AGNs shows that, after correction for the inferred VLBA core Faraday rotations, most BL Lac objects and some quasars have aligned VLBA-core and optical polarizations, although many quasars also show no obvious relationship between their VLBA-core and optical polarization angles. This may indicate that not all AGNs have cospatial regions of optical and radio emission in their jets. However, another possibility is that some of the 7mm-2cm VLBA cores have Faraday rotations of the order of several tens of thousand of rad/m^2, which were not properly fit by our three-frequency data due to n*pi ambiguities in the observed polarization angles, leading to incorrect subtraction of the effects of the core Faraday rotation, and so incorrect "zero-wavelength" radio polarization angles. The possibility of such high core Faraday rotations is supported by the results of the parsec-scale Faraday-rotation studies of Zavala & Taylor (2004) and Jorstad et al. (2007)., Comment: 6 pages, 2 figures, reference removed, to be published in Proceedings of Science, proceedings of The 9th European VLBI Network Symposium on The role of VLBI in the Golden Age for Radio Astronomy and EVN Users Meeting, September 23-26, 2008, Bologna, Italy
Published: 2009

15. On the dynamics of the ABDoradus system

Author: Guirado, J. C., Marti-Vidal, I., Marcaide, J. M., Close, L. M., Algaba, J. C., Brandner, W., Lestrade, J. -F., Jauncey, D. L., Jones, D. L., Preston, R. A., and Reynolds, J. E.
Subjects: Astrophysics
Abstract: We present an astrometric analysis of the binary systems ABDorA /ABDorC and ABDorBa / ABDorBb. These two systems of well-known late-type stars are gravitationally associated and they constitute the quadruple ABDoradus system. From the astrometric data available at different wavelengths, we report: (i) a determination of the orbit of ABDorC, the very low mass companion to ABDorA, which confirms the mass estimate of 0.090Msun reported in previous works; (ii) a measurement of the parallax of ABDorBa, which unambiguously confirms the long-suspected physical association between this star and ABDorA; and (iii) evidence of orbital motion of ABDorBa around ABDorA, which places an upper bound of 0.4Msun on the mass of the pair ABDorBa / ABDorBb (50% probability). Further astrometric monitoring of the system at all possible wavelengths would determine with extraordinary precision the dynamical mass of its four components., Comment: 7 pages, 4 figures
Published: 2005
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16. Interferometric monitoring of gamma-ray bright AGNs: Measuring the magnetic field strength of 4C +29.45

Author: Kang, S., primary, Lee, S.-S., additional, Hodgson, J., additional, Algaba, J.-C., additional, Lee, J. W., additional, Kim, J.-Y., additional, Park, J., additional, Kino, M., additional, Kim, D., additional, and Trippe, S., additional
Published: 2021
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17. Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign

Author: Algaba, J. C., additional, Anczarski, J., additional, Asada, K., additional, Baloković, M., additional, Chandra, S., additional, Cui, Y.-Z., additional, Falcone, A. D., additional, Giroletti, M., additional, Goddi, C., additional, Hada, K., additional, Haggard, D., additional, Jorstad, S., additional, Kaur, A., additional, Kawashima, T., additional, Keating, G., additional, Kim, J.-Y., additional, Kino, M., additional, Komossa, S., additional, Kravchenko, E. V., additional, Krichbaum, T. P., additional, Lee, S.-S., additional, Lu, R.-S., additional, Lucchini, M., additional, Markoff, S., additional, Neilsen, J., additional, Nowak, M. A., additional, Park, J., additional, Principe, G., additional, Ramakrishnan, V., additional, Reynolds, M. T., additional, Sasada, M., additional, Savchenko, S. S., additional, Williamson, K. E., additional, Akiyama, Kazunori, additional, Alberdi, Antxon, additional, Alef, Walter, additional, Anantua, Richard, additional, Azulay, Rebecca, additional, Baczko, Anne-Kathrin, additional, Ball, David, additional, Barrett, John, additional, Bintley, Dan, additional, Benson, Bradford A., additional, Blackburn, Lindy, additional, Blundell, Raymond, additional, Boland, Wilfred, additional, Bouman, Katherine L., additional, Bower, Geoffrey C., additional, Boyce, Hope, additional, Bremer, Michael, additional, Brinkerink, Christiaan D., additional, Brissenden, Roger, additional, Britzen, Silke, additional, Broderick, Avery E., additional, Broguiere, Dominique, additional, Bronzwaer, Thomas, additional, Byun, Do-Young, additional, Carlstrom, John E., additional, Chael, Andrew, additional, Chan, Chi-kwan, additional, Chatterjee, Shami, additional, Chatterjee, Koushik, additional, Chen, Ming-Tang, additional, Chen, Yongjun, additional, Chesler, Paul M., additional, Cho, Ilje, additional, Christian, Pierre, additional, Conway, John E., additional, Cordes, James M., additional, Crawford, Thomas M., additional, Crew, Geoffrey B., additional, Cruz-Osorio, Alejandro, additional, Davelaar, Jordy, additional, De Laurentis, Mariafelicia, additional, Deane, Roger, additional, Dempsey, Jessica, additional, Desvignes, Gregory, additional, Dexter, Jason, additional, Doeleman, Sheperd S., additional, Eatough, Ralph P., additional, Falcke, Heino, additional, Farah, Joseph, additional, Fish, Vincent L., additional, Fomalont, Ed, additional, Ford, H. Alyson, additional, Fraga-Encinas, Raquel, additional, Friberg, Per, additional, Fromm, Christian M., additional, Fuentes, Antonio, additional, Galison, Peter, additional, Gammie, Charles F., additional, García, Roberto, additional, Gentaz, Olivier, additional, Georgiev, Boris, additional, Gold, Roman, additional, Gómez, José L., additional, Gómez-Ruiz, Arturo I., additional, Gu, Minfeng, additional, Gurwell, Mark, additional, Hecht, Michael H., additional, Hesper, Ronald, additional, Ho, Luis C., additional, Ho, Paul, additional, Honma, Mareki, additional, Huang, Chih-Wei L., additional, Huang, Lei, additional, Hughes, David H., additional, Ikeda, Shiro, additional, Inoue, Makoto, additional, Issaoun, Sara, additional, James, David J., additional, Jannuzi, Buell T., additional, Janssen, Michael, additional, Jeter, Britton, additional, Jiang, Wu, additional, Jiménez-Rosales, Alejandra, additional, Johnson, Michael D., additional, Jung, Taehyun, additional, Karami, Mansour, additional, Karuppusamy, Ramesh, additional, Kettenis, Mark, additional, Kim, Dong-Jin, additional, Kim, Jongsoo, additional, Kim, Junhan, additional, Koay, Jun Yi, additional, Kofuji, Yutaro, additional, Koch, Patrick M., additional, Koyama, Shoko, additional, Kramer, Michael, additional, Kramer, Carsten, additional, Kuo, Cheng-Yu, additional, Lauer, Tod R., additional, Levis, Aviad, additional, Li, Yan-Rong, additional, Li, Zhiyuan, additional, Lindqvist, Michael, additional, Lico, Rocco, additional, Lindahl, Greg, additional, Liu, Jun, additional, Liu, Kuo, additional, Liuzzo, Elisabetta, additional, Lo, Wen-Ping, additional, Lobanov, Andrei P., additional, Loinard, Laurent, additional, Lonsdale, Colin, additional, MacDonald, Nicholas R., additional, Mao, Jirong, additional, Marchili, Nicola, additional, Marrone, Daniel P., additional, Marscher, Alan P., additional, Martí-Vidal, Iván, additional, Matsushita, Satoki, additional, Matthews, Lynn D., additional, Medeiros, Lia, additional, Menten, Karl M., additional, Mizuno, Izumi, additional, Mizuno, Yosuke, additional, Moran, James M., additional, Moriyama, Kotaro, additional, Moscibrodzka, Monika, additional, Müller, Cornelia, additional, Musoke, Gibwa, additional, Mejías, Alejandro Mus, additional, Nagai, Hiroshi, additional, Nagar, Neil M., additional, Nakamura, Masanori, additional, Narayan, Ramesh, additional, Narayanan, Gopal, additional, Natarajan, Iniyan, additional, Nathanail, Antonios, additional, Neri, Roberto, additional, Ni, Chunchong, additional, Noutsos, Aristeidis, additional, Okino, Hiroki, additional, Olivares, Héctor, additional, Ortiz-León, Gisela N., additional, Oyama, Tomoaki, additional, Özel, Feryal, additional, Palumbo, Daniel C. M., additional, Patel, Nimesh, additional, Pen, Ue-Li, additional, Pesce, Dominic W., additional, Piétu, Vincent, additional, Plambeck, Richard, additional, PopStefanija, Aleksandar, additional, Porth, Oliver, additional, Pötzl, Felix M., additional, Prather, Ben, additional, Preciado-López, Jorge A., additional, Psaltis, Dimitrios, additional, Pu, Hung-Yi, additional, Rao, Ramprasad, additional, Rawlings, Mark G., additional, Raymond, Alexander W., additional, Rezzolla, Luciano, additional, Ricarte, Angelo, additional, Ripperda, Bart, additional, Roelofs, Freek, additional, Rogers, Alan, additional, Ros, Eduardo, additional, Rose, Mel, additional, Roshanineshat, Arash, additional, Rottmann, Helge, additional, Roy, Alan L., additional, Ruszczyk, Chet, additional, Rygl, Kazi L. J., additional, Sánchez, Salvador, additional, Sánchez-Arguelles, David, additional, Savolainen, Tuomas, additional, Schloerb, F. Peter, additional, Schuster, Karl-Friedrich, additional, Shao, Lijing, additional, Shen, Zhiqiang, additional, Small, Des, additional, Sohn, Bong Won, additional, SooHoo, Jason, additional, Sun, He, additional, Tazaki, Fumie, additional, Tetarenko, Alexandra J., additional, Tiede, Paul, additional, Tilanus, Remo P. J., additional, Titus, Michael, additional, Toma, Kenji, additional, Torne, Pablo, additional, Trent, Tyler, additional, Traianou, Efthalia, additional, Trippe, Sascha, additional, van Bemmel, Ilse, additional, van Langevelde, Huib Jan, additional, van Rossum, Daniel R., additional, Wagner, Jan, additional, Ward-Thompson, Derek, additional, Wardle, John, additional, Weintroub, Jonathan, additional, Wex, Norbert, additional, Wharton, Robert, additional, Wielgus, Maciek, additional, Wong, George N., additional, Wu, Qingwen, additional, Yoon, Doosoo, additional, Young, André, additional, Young, Ken, additional, Younsi, Ziri, additional, Yuan, Feng, additional, Yuan, Ye-Fei, additional, Zensus, J. Anton, additional, Zhao, Guang-Yao, additional, Zhao, Shan-Shan, additional, D’Ammando, F., additional, Orienti, M., additional, Abdalla, H., additional, Adam, R., additional, Aharonian, F., additional, Benkhali, F. Ait, additional, Angüner, E. O., additional, Arcaro, C., additional, Armand, C., additional, Armstrong, T., additional, Ashkar, H., additional, Backes, M., additional, Baghmanyan, V., additional, Barbosa Martins, V., additional, Barnacka, A., additional, Barnard, M., additional, Becherini, Y., additional, Berge, D., additional, Bernlöhr, K., additional, Bi, B., additional, Böttcher, M., additional, Boisson, C., additional, Bolmont, J., additional, de Bony de Lavergne, M., additional, Breuhaus, M., additional, Brun, F., additional, Brun, P., additional, Bryan, M., additional, Büchele, M., additional, Bulik, T., additional, Bylund, T., additional, Caroff, S., additional, Carosi, A., additional, Casanova, S., additional, Chand, T., additional, Chen, A., additional, Cotter, G., additional, Curyło, M., additional, Damascene Mbarubucyeye, J., additional, Davids, I. D., additional, Davies, J., additional, Deil, C., additional, Devin, J., additional, deWilt, P., additional, Dirson, L., additional, Djannati-Ataï, A., additional, Dmytriiev, A., additional, Donath, A., additional, Doroshenko, V., additional, Duffy, C., additional, Dyks, J., additional, Egberts, K., additional, Eichhorn, F., additional, Einecke, S., additional, Emery, G., additional, Ernenwein, J.-P., additional, Feijen, K., additional, Fegan, S., additional, Fiasson, A., additional, de Clairfontaine, G. Fichet, additional, Fontaine, G., additional, Funk, S., additional, Füßling, M., additional, Gabici, S., additional, Gallant, Y. A., additional, Giavitto, G., additional, Giunti, L., additional, Glawion, D., additional, Glicenstein, J. F., additional, Gottschall, D., additional, Grondin, M.-H., additional, Hahn, J., additional, Haupt, M., additional, Hermann, G., additional, Hinton, J. A., additional, Hofmann, W., additional, Hoischen, C., additional, Holch, T. L., additional, Holler, M., additional, Hörbe, M., additional, Horns, D., additional, Huber, D., additional, Jamrozy, M., additional, Jankowsky, D., additional, Jankowsky, F., additional, Jardin-Blicq, A., additional, Joshi, V., additional, Jung-Richardt, I., additional, Kasai, E., additional, Kastendieck, M. A., additional, Katarzyński, K., additional, Katz, U., additional, Khangulyan, D., additional, Khélifi, B., additional, Klepser, S., additional, Kluźniak, W., additional, Komin, Nu., additional, Konno, R., additional, Kosack, K., additional, Kostunin, D., additional, Kreter, M., additional, Lamanna, G., additional, Lemière, A., additional, Lemoine-Goumard, M., additional, Lenain, J.-P., additional, Levy, C., additional, Lohse, T., additional, Lypova, I., additional, Mackey, J., additional, Majumdar, J., additional, Malyshev, D., additional, Marandon, V., additional, Marchegiani, P., additional, Marcowith, A., additional, Mares, A., additional, Martí-Devesa, G., additional, Marx, R., additional, Maurin, G., additional, Meintjes, P. J., additional, Meyer, M., additional, Moderski, R., additional, Mohamed, M., additional, Mohrmann, L., additional, Montanari, A., additional, Moore, C., additional, Morris, P., additional, Moulin, E., additional, Muller, J., additional, Murach, T., additional, Nakashima, K., additional, Nayerhoda, A., additional, de Naurois, M., additional, Ndiyavala, H., additional, Niederwanger, F., additional, Niemiec, J., additional, Oakes, L., additional, O’Brien, P., additional, Odaka, H., additional, Ohm, S., additional, Olivera-Nieto, L., additional, de Ona Wilhelmi, E., additional, Ostrowski, M., additional, Panter, M., additional, Panny, S., additional, Parsons, R. D., additional, Peron, G., additional, Peyaud, B., additional, Piel, Q., additional, Pita, S., additional, Poireau, V., additional, Noel, A. Priyana, additional, Prokhorov, D. A., additional, Prokoph, H., additional, Pühlhofer, G., additional, Punch, M., additional, Quirrenbach, A., additional, Rauth, R., additional, Reichherzer, P., additional, Reimer, A., additional, Reimer, O., additional, Remy, Q., additional, Renaud, M., additional, Rieger, F., additional, Rinchiuso, L., additional, Romoli, C., additional, Rowell, G., additional, Rudak, B., additional, Ruiz-Velasco, E., additional, Sahakian, V., additional, Sailer, S., additional, Sanchez, D. A., additional, Santangelo, A., additional, Sasaki, M., additional, Scalici, M., additional, Schutte, H. M., additional, Schwanke, U., additional, Schwemmer, S., additional, Seglar-Arroyo, M., additional, Senniappan, M., additional, Seyffert, A. S., additional, Shafi, N., additional, Shiningayamwe, K., additional, Simoni, R., additional, Sinha, A., additional, Sol, H., additional, Specovius, A., additional, Spencer, S., additional, Spir-Jacob, M., additional, Stawarz, Ł., additional, Sun, L., additional, Steenkamp, R., additional, Stegmann, C., additional, Steinmassl, S., additional, Steppa, C., additional, Takahashi, T., additional, Tavernier, T., additional, Taylor, A. M., additional, Terrier, R., additional, Tiziani, D., additional, Tluczykont, M., additional, Tomankova, L., additional, Trichard, C., additional, Tsirou, M., additional, Tuffs, R., additional, Uchiyama, Y., additional, van der Walt, D. J., additional, van Eldik, C., additional, van Rensburg, C., additional, van Soelen, B., additional, Vasileiadis, G., additional, Veh, J., additional, Venter, C., additional, Vincent, P., additional, Vink, J., additional, Völk, H. J., additional, Vuillaume, T., additional, Wadiasingh, Z., additional, Wagner, S. J., additional, Watson, J., additional, Werner, F., additional, White, R., additional, Wierzcholska, A., additional, Wong, Yu Wun, additional, Yusafzai, A., additional, Zacharias, M., additional, Zanin, R., additional, Zargaryan, D., additional, Zdziarski, A. A., additional, Zech, A., additional, Zhu, S. J., additional, Zorn, J., additional, Zouari, S., additional, Żywucka, N., additional, Acciari, V. A., additional, Ansoldi, S., additional, Antonelli, L. A., additional, Engels, A. Arbet, additional, Artero, M., additional, Asano, K., additional, Baack, D., additional, Babić, A., additional, Baquero, A., additional, de Almeida, U. Barres, additional, Barrio, J. A., additional, Becerra González, J., additional, Bednarek, W., additional, Bellizzi, L., additional, Bernardini, E., additional, Bernardos, M., additional, Berti, A., additional, Besenrieder, J., additional, Bhattacharyya, W., additional, Bigongiari, C., additional, Biland, A., additional, Blanch, O., additional, Bonnoli, G., additional, Bošnjak, Ž., additional, Busetto, G., additional, Carosi, R., additional, Ceribella, G., additional, Cerruti, M., additional, Chai, Y., additional, Chilingarian, A., additional, Cikota, S., additional, Colak, S. M., additional, Colombo, E., additional, Contreras, J. L., additional, Cortina, J., additional, Covino, S., additional, D’Amico, G., additional, D’Elia, V., additional, Da Vela, P., additional, Dazzi, F., additional, De Angelis, A., additional, De Lotto, B., additional, Delfino, M., additional, Delgado, J., additional, Delgado Mendez, C., additional, Depaoli, D., additional, Di Pierro, F., additional, Di Venere, L., additional, Do Souto Espiñeira, E., additional, Dominis Prester, D., additional, Donini, A., additional, Dorner, D., additional, Doro, M., additional, Elsaesser, D., additional, Fallah Ramazani, V., additional, Fattorini, A., additional, Ferrara, G., additional, Fonseca, M. V., additional, Font, L., additional, Fruck, C., additional, Fukami, S., additional, García López, R. J., additional, Garczarczyk, M., additional, Gasparyan, S., additional, Gaug, M., additional, Giglietto, N., additional, Giordano, F., additional, Gliwny, P., additional, Godinović, N., additional, Green, J. G., additional, Green, D., additional, Hadasch, D., additional, Hahn, A., additional, Heckmann, L., additional, Herrera, J., additional, Hoang, J., additional, Hrupec, D., additional, Hütten, M., additional, Inada, T., additional, Inoue, S., additional, Ishio, K., additional, Iwamura, Y., additional, Jiménez, I., additional, Jormanainen, J., additional, Jouvin, L., additional, Kajiwara, Y., additional, Karjalainen, M., additional, Kerszberg, D., additional, Kobayashi, Y., additional, Kubo, H., additional, Kushida, J., additional, Lamastra, A., additional, Lelas, D., additional, Leone, F., additional, Lindfors, E., additional, Lombardi, S., additional, Longo, F., additional, López-Coto, R., additional, López-Moya, M., additional, López-Oramas, A., additional, Loporchio, S., additional, Machado de Oliveira Fraga, B., additional, Maggio, C., additional, Majumdar, P., additional, Makariev, M., additional, Mallamaci, M., additional, Maneva, G., additional, Manganaro, M., additional, Mannheim, K., additional, Maraschi, L., additional, Mariotti, M., additional, Martínez, M., additional, Mazin, D., additional, Menchiari, S., additional, Mender, S., additional, Mićanović, S., additional, Miceli, D., additional, Miener, T., additional, Minev, M., additional, Miranda, J. M., additional, Mirzoyan, R., additional, Molina, E., additional, Moralejo, A., additional, Morcuende, D., additional, Moreno, V., additional, Moretti, E., additional, Neustroev, V., additional, Nigro, C., additional, Nilsson, K., additional, Nishijima, K., additional, Noda, K., additional, Nozaki, S., additional, Ohtani, Y., additional, Oka, T., additional, Otero-Santos, J., additional, Paiano, S., additional, Palatiello, M., additional, Paneque, D., additional, Paoletti, R., additional, Paredes, J. M., additional, Pavletić, L., additional, Peñil, P., additional, Perennes, C., additional, Persic, M., additional, Moroni, P. G. Prada, additional, Prandini, E., additional, Priyadarshi, C., additional, Puljak, I., additional, Rhode, W., additional, Ribó, M., additional, Rico, J., additional, Righi, C., additional, Rugliancich, A., additional, Saha, L., additional, Sahakyan, N., additional, Saito, T., additional, Sakurai, S., additional, Satalecka, K., additional, Saturni, F. G., additional, Schleicher, B., additional, Schmidt, K., additional, Schweizer, T., additional, Sitarek, J., additional, Šnidarić, I., additional, Sobczynska, D., additional, Spolon, A., additional, Stamerra, A., additional, Strom, D., additional, Strzys, M., additional, Suda, Y., additional, Surić, T., additional, Takahashi, M., additional, Tavecchio, F., additional, Temnikov, P., additional, Terzić, T., additional, Teshima, M., additional, Tosti, L., additional, Truzzi, S., additional, Tutone, A., additional, Ubach, S., additional, van Scherpenberg, J., additional, Vanzo, G., additional, Vazquez Acosta, M., additional, Ventura, S., additional, Verguilov, V., additional, Vigorito, C. F., additional, Vitale, V., additional, Vovk, I., additional, Will, M., additional, Wunderlich, C., additional, Zarić, D., additional, Adams, C. B., additional, Benbow, W., additional, Brill, A., additional, Capasso, M., additional, Christiansen, J. L., additional, Chromey, A. J., additional, Daniel, M. K., additional, Errando, M., additional, Farrell, K. A, additional, Feng, Q., additional, Finley, J. P., additional, Fortson, L., additional, Furniss, A., additional, Gent, A., additional, Giuri, C., additional, Hassan, T., additional, Hervet, O., additional, Holder, J., additional, Hughes, G., additional, Humensky, T. B., additional, Jin, W., additional, Kaaret, P., additional, Kertzman, M., additional, Kieda, D., additional, Kumar, S., additional, Lang, M. J., additional, Lundy, M., additional, Maier, G., additional, Moriarty, P., additional, Mukherjee, R., additional, Nieto, D., additional, Nievas-Rosillo, M., additional, O’Brien, S., additional, Ong, R. A., additional, Otte, A. N., additional, Patel, S., additional, Pfrang, K., additional, Pohl, M., additional, Prado, R. R., additional, Pueschel, E., additional, Quinn, J., additional, Ragan, K., additional, Reynolds, P. T., additional, Ribeiro, D., additional, Richards, G. T., additional, Roache, E., additional, Rulten, C., additional, Ryan, J. L., additional, Santander, M., additional, Sembroski, G. H., additional, Shang, R., additional, Weinstein, A., additional, Williams, D. A., additional, Williamson, T. J, additional, Hirota, Tomoya, additional, Cui, Lang, additional, Niinuma, Kotaro, additional, Ro, Hyunwook, additional, Sakai, Nobuyuki, additional, Sawada-Satoh, Satoko, additional, Wajima, Kiyoaki, additional, Wang, Na, additional, Liu, Xiang, additional, and Yonekura, Yoshinori, additional
Published: 2021
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18. Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign.

Author: Group, The EHT MWL Science Working, Algaba, J. C., Anczarski, J., Asada, K., Baloković, M., Chandra, S., Cui, Y.-Z., Falcone, A. D., Giroletti, M., Goddi, C., Hada, K., Haggard, D., Jorstad, S., Kaur, A., Kawashima, T., Keating, G., Kim, J.-Y., Kino, M., Komossa, S., and Kravchenko, E. V.
Published: 2021
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19. Exploring the Morphology and Origins of the 4C 38.41 Jet

Author: Algaba, J. C., primary, Rani, B., additional, Lee, S. S., additional, Kino, M., additional, Park, Jongho, additional, and Kim, Jae-Young, additional
Published: 2019
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20. RESOLVING THE GEOMETRY OF THE INNERMOST RELATIVISTIC JETS IN ACTIVE GALACTIC NUCLEI

Author: Algaba, J. C., primary, Nakamura, M., additional, Asada, K., additional, and Lee, S. S., additional
Published: 2017
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21. Millimeter VLBI observations of Sgr A* with KaVA and KVN.

Author: Zhao, G.-Y., Kino, M., Cho, I.-J., Akiyama, K., Sohn, B. W., Jung, T., Algaba, J. C., Hada, K., Hagiwara, Y., Hodgson, J., Honma, M., Kawaguchi, N., Koyama, S., Lee, J. A., Lee, T., Niinuma, K., Oh, J., Park, J.-H., Ro, H., and Sawada-Satoh, S.
Abstract: We present recent observation results of Sgr A* at millimeter obtained with VLBI arrays in Korea and Japan.7 mm monitoring of Sgr A* is part of our AGN large project. The results at 7 epochs during 2013-2014, including high resolution maps, flux density and two-dimensional size measurements are presented. The source shows no significant variation in flux and structure related to the G2 encounter in 2014. According to recent MHD simulations by kawashima et al., flux and magnetic field energy can be expected to increase several years after the encounter; We will keep our monitoring in order to test this prediction.Astrometric observations of Sgr A* were performed in 2015 at 7 and 3.5 millimeter simultaneously. Source-frequency phase referencing was applied and a combined ”core-shift” of Sgr A* and a nearby calibrator was measured. Future observations and analysis are necessary to determine the core-shift in each source. [ABSTRACT FROM PUBLISHER]
Published: 2016
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22. RESOLVING THE ROTATION MEASURE OF THE M87 JET ON KILOPARSEC SCALES

Author: Algaba, J. C., primary, Asada, K., additional, and Nakamura, M., additional
Published: 2016
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23. Greenland Telescope (GLT) Project

Author: Nakamura M., Algaba J. C., Asada K., Chen B., Chen M.-T., Han J., Ho P. H. P., Hsieh S.-N., Huang T., Inoue M., Koch P., Kuo C.-Y., Martin-Cocher P., Matsushita S., Meyer-Zhao Z., Nishioka H., Nystrom G., Pradel N., Pu H.-Y., Raffin P., Shen H.-Y., and Tseng C.-Y.
Subjects: Physics, QC1-999
Abstract: The GLT project is deploying a new submillimeter (submm) VLBI station in Greenland. Our primary scientific goal is to image a shadow of the supermassive black hole (SMBH) of six billion solar masses in M87 at the center of the Virgo cluster of galaxies. The expected SMBH shadow size of 40-50 μas requires superbly high angular resolution, suggesting that the submm VLBI would be the only way to obtain the shadow image. The Summit station in Greenland enables us to establish baselines longer than 9,000 km with ALMA in Chile and SMA in Hawaii as well as providing a unique u–v coverage for imaging M87. Our VLBI network will achieve a superior angular resolution of about 20 μas at 350 GHz, corresponding to ∼ 2.5 times of the Schwarzschild radius of the supermassive black hole in M87. We have been monitoring the atmospheric opacity at 230 GHz since August. 2011; we have confirmed the value on site during the winter season is comparable to the ALMA site thanks to high altitude of 3,200 m and low temperature of −50°C. We will report current status and future plan of the GLT project towards our expected first light on 2015–2016.
Published: 2013

24. MEASURING MASS ACCRETION RATE ONTO THE SUPERMASSIVE BLACK HOLE IN M87 USING FARADAY ROTATION MEASURE WITH THE SUBMILLIMETER ARRAY

Author: Kuo, C. Y., primary, Asada, K., additional, Rao, R., additional, Nakamura, M., additional, Algaba, J. C., additional, Liu, H. B., additional, Inoue, M., additional, Koch, P. M., additional, Ho, P. T. P., additional, Matsushita, S., additional, Pu, H.-Y., additional, Akiyama, K., additional, Nishioka, H., additional, and Pradel, N., additional
Published: 2014
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25. High-frequency very long baseline interferometry rotation measure of eight active galactic nuclei

Author: Algaba, J. C., primary
Published: 2013
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26. Search for correlations between the optical and radio polarization of active galactic nuclei - II. VLBA polarization data at 12+15+22+24+43 GHz

Author: Algaba, J. C., primary, Gabuzda, D. C., additional, and Smith, P. S., additional
Published: 2011
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27. Search for correlations between the optical and radio polarization of active galactic nuclei - I. VLBA polarization data at 15 + 22 + 43 GHz

Author: Algaba, J. C., primary, Gabuzda, D. C., additional, and Smith, P. S., additional
Published: 2010
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28. The 15-43 GHz parsec-scale circular polarization of 41 active galactic nuclei

Author: Vitrishchak, V. M., primary, Gabuzda, D. C., additional, Algaba, J. C., additional, Rastorgueva, E. A., additional, O'Sullivan, S. P., additional, and O'Dowd, A., additional
Published: 2008
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29. INVESTIGATION OF CORRELATIONS BETWEEN THE OPTICAL AND VLBI CORE POLARIZATION OF AGN

Author: ALGABA, J. C., primary, GABUZDA, D. C., additional, and SMITH, P. S., additional
Published: 2008
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30. On the dynamics of the AB Doradus system

Author: Guirado, J. C., primary, Martí-Vidal, I., additional, Marcaide, J. M., additional, Close, L. M., additional, Algaba, J. C., additional, Brandner, W., additional, Lestrade, J.-F., additional, Jauncey, D. L., additional, Jones, D. L., additional, Preston, R. A., additional, and Reynolds, J. E., additional
Published: 2006
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31. Search for correlations between the optical and radio polarization of active galactic nuclei - II. VLBA polarization data at 12+15+22+24+43 GHz.

Author: Algaba, J. C., Gabuzda, D. C., and Smith, P. S.
Subjects: *STATISTICAL correlation, *OPTICAL polarization, *ACTIVE galactic nuclei, *BL Lacertae objects, *QUASARS, *VERY long baseline interferometry, *SOLAR radio emission, *SOLAR magnetic fields
Abstract: ABSTRACT Previous research showed that most BL Lac objects and some quasars have aligned very long baseline interferometry (VLBI) core and optical polarizations, although some of the active galactic nuclei (AGNs) also showed no obvious relationship between their VLBI core and optical polarization angles. This may indicate that some AGNs have cospatial regions of optical and radio emission, while others do not. However, another possibility is that some of the VLBI cores had Faraday rotations of the order of several tens of thousands of rad m−2, which were not properly fitted using the three-frequency data due to nπ ambiguities in the observed polarization angles, leading to incorrect subtraction of the effects of the core Faraday rotation, and so incorrect intrinsic radio polarization angles χ0. With this is mind, we obtained additional 12+15+22+24+43 GHz plus optical observations for eight of 40 AGNs previously considered, enabling improved sampling of Faraday effects. Our results indicate that, although some VLBI radio cores have comparatively high rotation measures, this alone cannot explain the misalignments found between the radio core and optical VLBI polarization angles, Δχ= |χopt−χ0|. Comparisons between Δχ and (i) the orientation of χ0 relative to the jet direction, (ii) the degree of polarization of the core, (iii) a depolarization factor, (iv) the core rotation measures and (v) the core magnetic fields 1 pc from the jet base do not yield evidence for any correlations between these properties. There is, however, some evidence that the maximum observed Δχ tends to decrease as the core-region magnetic field increases, suggesting that large misalignments in Δχ could be associated in part with relatively low core magnetic fields. Thus, although the overall distribution of Δχ for all 40 sources in our sample does show a significant peak at Δχ∼ 0, it remains unclear what distinguishes these AGN cores from those showing appreciable misalignment between optical and VLBI core polarization position angles. [ABSTRACT FROM AUTHOR]
Published: 2012
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32. Search for correlations between the optical and radio polarization of active galactic nuclei - I. VLBA polarization data at 15 + 22 + 43 GHz.

Author: Algaba, J. C., Gabuzda, D. C., and Smith, P. S.
Subjects: *STATISTICAL correlation, *ACTIVE galactic nuclei, *SYNCHROTRON radiation, *QUASARS, *SOLAR radio emission, *RADIO antennas
Abstract: Although the continua of radio-loud active galactic nuclei (AGNs) are typically dominated by synchrotron radiation over virtually the entire spectrum, it is not clear whether the radio and higher frequency emission originates in the same or different parts of the jet. In some inhomogeneous synchrotron source models, the radio and ultraviolet-optical-infrared emission may be co-spatial, depending on the model parameters considered. Indeed, several different radio-optical correlations based on polarization data have been found recently, suggesting that the optical and radio polarization may be closely related in some AGNs, and that the corresponding emission regions may be co-spatial. Our joint analysis of optical and GHz Very Long Baseline Array (VLBA) polarization data for a sample of about 40 AGNs shows that, after correction for the inferred VLBA core Faraday rotations, about 50-55 per cent of BL Lac objects and high-polarization quasars, and about 65 per cent of high-polarization quasars (LPQs) have aligned VLBA-core and optical polarization angles to within ; a considerable number of objects also show no obvious relationship between their VLBA-core and optical polarization angles. This may indicate that only some AGNs have co-spatial regions of optical and radio emission in their jets. However, another possibility is that some of the 15-43 GHz VLBA cores have Faraday rotations of the order of several tens of thousand of rad m, which were not properly fitted using our three-frequency data due to ambiguities in the observed polarization angles, leading to inaccurate subtraction of the effects of the core Faraday rotation and so incorrect 'zero-wavelength' radio polarization angles. [ABSTRACT FROM AUTHOR]
Published: 2011
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33. Relativistic reflection modeling in AGN and related variability from PCA: a brief review.

Author: Danehkar, A.
Subjects: GALACTIC X-ray sources, ACTIVE galactic nuclei, SUPERMASSIVE black holes, MACHINE learning, PRINCIPAL components analysis
Abstract: X-ray observations of active galactic nuclei (AGNs) reveal relativistic reflections from the innermost regions of accretion disks, which contain general-relativistic footprints caused by spinning supermassive black holes (SMBH). We anticipate the spin of a SMBH to be stable over the human timeframe, so brightness changes in the high-energy corona above the SMBH should slightly alter relativistic reflection. In this brief review, we discuss the latest developments in modeling relativistic reflection, as well as the rapid small variation in relativistic emission disclosed by the principal component analysis (PCA) of X-ray variability in AGN. PCA studies of X-ray spectra from AGNs have shown that relativistically blurred reflection has negligible fluctuations over the course of observations, which could originate from rapid (intrahour) intrinsic variations in near-horizon accretion flows and photon rings. The PCA technique is an effective way to disclose relativistic reflection from X-ray observations of AGNs, simplifying the complexity of largely variable X-ray data for automated spectral analysis with machine learning algorithms. [ABSTRACT FROM AUTHOR]
Published: 2024
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34. Fractional Einstein–Gauss–Bonnet Scalar Field Cosmology.

Author: Micolta-Riascos, Bayron, Millano, Alfredo D., Leon, Genly, Droguett, Byron, González, Esteban, and Magaña, Juan
Subjects: FRACTIONAL calculus, TYPE I supernovae, SUPERMASSIVE black holes, DYNAMICAL systems, LARGE space structures (Astronautics)
Abstract: Our paper introduces a new theoretical framework called the Fractional Einstein–Gauss–Bonnet scalar field cosmology, which has important physical implications. Using fractional calculus to modify the gravitational action integral, we derived a modified Friedmann equation and a modified Klein–Gordon equation. Our research reveals non-trivial solutions associated with exponential potential, exponential couplings to the Gauss–Bonnet term, and a logarithmic scalar field, which are dependent on two cosmological parameters, m and α 0 = t 0 H 0 and the fractional derivative order μ. By employing linear stability theory, we reveal the phase space structure and analyze the dynamic effects of the Gauss–Bonnet couplings. The scaling behavior at some equilibrium points reveals that the geometric corrections in the coupling to the Gauss–Bonnet scalar can mimic the behavior of the dark sector in modified gravity. Using data from cosmic chronometers, type Ia supernovae, supermassive Black Hole Shadows, and strong gravitational lensing, we estimated the values of m and α 0 , indicating that the solution is consistent with an accelerated expansion at late times with the values α 0 = 1.38 ± 0.05 , m = 1.44 ± 0.05 , and μ = 1.48 ± 0.17 (consistent with Ω m , 0 = 0.311 ± 0.016 and h = 0.712 ± 0.007 ), resulting in an age of the Universe t 0 = 19.0 ± 0.7 [Gyr] at 1 σ CL. Ultimately, we obtained late-time accelerating power-law solutions supported by the most recent cosmological data, and we proposed an alternative explanation for the origin of cosmic acceleration other than Λ CDM. Our results generalize and significantly improve previous achievements in the literature, highlighting the practical implications of fractional calculus in cosmology. [ABSTRACT FROM AUTHOR]
Published: 2024
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35. Discovery of Limb Brightening in the Parsec-scale Jet of NGC 315 through Global Very Long Baseline Interferometry Observations and Its Implications for Jet Models.

Author: Park, Jongho, Zhao, Guang-Yao, Nakamura, Masanori, Mizuno, Yosuke, Pu, Hung-Yi, Asada, Keiichi, Takahashi, Kazuya, Toma, Kenji, Kino, Motoki, Cho, Ilje, Hada, Kazuhiro, Edwards, Phil G., Ro, Hyunwook, Kam, Minchul, Yi, Kunwoo, Lee, Yunjeong, Koyama, Shoko, Byun, Do-Young, Phillips, Chris, and Reynolds, Cormac
Published: 2024
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36. Circular Polarization of Simulated Images of Black Holes.

Author: Joshi, Abhishek V., Prather, Ben S., Chan, Chi-kwan, Wielgus, Maciek, and Gammie, Charles F.
Subjects: MAGNETIC dipole moments, SUPERMASSIVE black holes, MAGNETIC flux density, CIRCULAR polarization, ACTIVE galactic nuclei
Abstract: Models of the resolved Event Horizon Telescope (EHT) sources Sgr A* and M87* are constrained by observations at multiple wavelengths, resolutions, polarizations, and time cadences. In this paper, we compare unresolved circular polarization (CP) measurements to a library of models, where each model is characterized by a distribution of CP over time. In the library, we vary the spin of the black hole, the magnetic field strength at the horizon (i.e., both SANE and magnetically arrested disk or MAD models), the observer inclination, a parameter for the maximum ion–electron temperature ratio assuming a thermal plasma, and the direction of the magnetic field dipole moment. We find that Atacama Large Millimeter/submillimeter Array (ALMA) observations of Sgr A* are inconsistent with all edge-on (i = 90°) models. Restricting attention to the MAD models favored by earlier EHT studies of Sgr A*, we find that only models with magnetic dipole moment pointing away from the observer are consistent with ALMA data. We also note that in 26 of the 27 passing MAD models, the accretion flow rotates clockwise on the sky. We provide a table of the means and standard deviations of the CP distributions for all model parameters, along with their trends. [ABSTRACT FROM AUTHOR]
Published: 2024
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37. A two-step strategy to identify episodic sources of gravitational waves and high-energy neutrinos in starburst galaxies.

Author: Allen, M. L., Biermann, P. L., Caramete, L. I., Chieffi, A., Chini, R., Frekers, D., Gergely, L. Á., Harms, B., Jaroschewski, I., Joshi, P. S., Kronberg, P. P., Kun, E., Meli, A., Seo, E.-S., Stanev, T., Reynoso, Matías Miguel, and Gu Chen
Subjects: GRAVITATIONAL waves, NEUTRINOS, STARBURSTS, SUPERMASSIVE black holes, ACTIVE galactic nuclei, PARTICLE acceleration, RELATIVISTIC particles
Abstract: Supermassive black hole (BH) mergers with spin-flips accelerate energetic particles through their relativistic precessing jets, producing high-energy neutrinos and finally gravitational waves (GWs). In star formation, massive stars form in pairs, triplets, and quadruplets, allowing second-generation mergers of the remnants with discrepant spin directions. The GW data support such a scenario. Earlier, we suggested that stellar mass BH mergers (visible in M82) with an associated spin-flip analogously allow the acceleration of energetic particles, with ensuing high-energy neutrinos and high-energy photons, and finally produce GWs. At cosmic distances, only the GWs and the neutrinos remain detectable. In this study, we generalize the argument to starburst and normal galaxies throughout their cosmic evolution and show that these galaxies may dominate over active galactic nuclei (AGN) in the flux of ultra-high-energy particles observed at Earth. All these sources contribute to the cosmic neutrino background, as well as the GW background (they detected lower frequencies). We outline a search strategy to find such episodic sources, which requires including both luminosity and flux density. [ABSTRACT FROM AUTHOR]
Published: 2024
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38. White Paper on East Asian Vision for mm/submm VLBI: Toward Black Hole Astrophysics down to Angular Resolution of 1~R$_{S}$

Author: Asada, K., Kino, M., Honma, M., Hirota, T., Lu, R. -S, Inoue, M., Sohn, B. -W, Shen, Z. -Q, Ho, P. T. P., Kazunori Akiyama, Algaba, J-C, An, T., Bower, G., Byun, D-Y, Dodson, R., Doi, A., Edwards, P. G., Fujisawa, K., Gu, M-F, Hada, K., Hagiwara, Y., Jaroenjittichai, P., Jung, T., Kawashima, T., Koyama, S., Lee, S-S, Matsushita, S., Nagai, H., Nakamura, M., Niinuma, K., Phillips, C., Park, J-H, Pu, H-Y, Ro, H-W, Stevens, J., Trippe, S., Wajima, K., and Zhao, G-Y
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), FOS: Physical sciences, Astrophysics - High Energy Astrophysical Phenomena
Abstract: This White Paper details the intentions and plans of the East Asian Very Long Baseline Interferometry (VLBI) community for pushing the frontiers of millimeter/submillimeter VLBI. To this end, we shall endeavor to actively promote coordinated efforts in the East Asia region. Our goal is to establish firm collaborations among the East Asia VLBI community in partnership with related institutes in North America and Europe and to expand existing global mm/submm VLBI arrays for (a) exploring the vicinity of black holes with an ultimate angular resolution down to 1~R$_{S}$ (Schwarzschild radius) and (b) investigating the dynamics of circumstellar gas in star-forming regions and late-type stars, and circumnuclear gas around active galactic nuclei (AGNs). In the first half of this White Paper, we highlight scientific accomplishments of the East Asia (EA) VLBI community. Various VLBI research results on M87, Sgr A*, blazars, narrow-line Seyfert~1 galaxies, and compact symmetric objects are described, and future visions of our VLBI science are briefly presented. Maser science of star formation, stellar evolution, and physics of accretion disks around AGNs are also discussed. A new vision for conducting multi-transition maser studies using mm/submm VLBI together with the Atacama Large Millimeter/Submillimeter Array (ALMA) is described. In the second half of this White Paper, we describe the EA community's vision for using mm/submm VLBI arrays in the framework or extended version of the Event Horizon Telescope (EHT) and the Global Millimeter VLBI Array (GMVA). The accomplishment of the aforementioned goal will maximize the overall scientific outcomes of mm/submm VLBI in the world., Comment: 93 pages, 54 figures. White Paper from East Asia VLBI community

39. Origin and evolution of the multi–band variability in the flat spectrum radio source 4C 38.41

Author: Algaba, J. C., Lee, S. S., Rani, B., Kim, D. -W, Kino, M., Hodgson, J., Zhao, G. -Y, Byun, D. -Y, Gurwell, M., Kang, S. -C, Kim, J. -Y, Kim, J. -S, Kim, S. -W, Park, J. -H, Trippe, S., and Kiyoaki Wajima

40. Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign

Author: Algaba, J. C., Anczarski, J., Asada, K., Baloković, M., Chandra, S., Cui, Y.-Z., Falcone, A. D., Giroletti, M., Goddi, C., Hada, K., Haggard, D., Jorstad, S., Kaur, A., Kawashima, T., Keating, G., Kim, J.-Y., Kino, M., Komossa, S., Kravchenko, E. V., Krichbaum, T. P., Lee, S.-S., Lu, R.-S., Lucchini, M., Markoff, S., Neilsen, J., Nowak, M. A., Park, J., Principe, G., Ramakrishnan, V., Reynolds, M. T., Sasada, M., Savchenko, S. S., Williamson, K. E., Hirota, Tomoya, Cui, Lang, Niinuma, Kotaro, Ro, Hyunwook, Sakai, Nobuyuki, Sawada-Satoh, Satoko, Wajima, Kiyoaki, Wang, Na, Liu, Xiang, Yonekura, Yoshinori, Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Anantua, Richard, Azulay, Rebecca, Baczko, Anne-Kathrin, Ball, David, Barrett, John, Bintley, Dan, Benson, Bradford A., 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., Chael, Andrew, 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, 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, E., Alyson Ford, H., Fraga-Encinas, Raquel, Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, Gammie, Charles F., García, Roberto, Gentaz, Olivier, Georgiev, Boris, Gold, Roman, Gómez, José L., Gómez-Ruiz, Arturo I., Gu, Minfeng, Gurwell, Mark, 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, Johnson, Michael D., Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kettenis, Mark, Kim, Dong-Jin, Kim, Jongsoo, Kim, Junhan, Koay, Jun Yi, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Michael, Kramer, Carsten, Kuo, Cheng-Yu, Lauer, Tod R., 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, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, 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, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Okino, Hiroki, Olivares, Héctor, Ortiz-León, Gisela N., Oyama, Tomoaki, Özel, Feryal, Palumbo, Daniel C. M., 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, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Rezzolla, Luciano, Ricarte, Angelo, 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, Savolainen, Tuomas, Peter Schloerb, F., 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, Anton Zensus, J., Zhao, Guang-Yao, Zhao, Shan-Shan, D'Ammando, F., Orienti, M., Abdalla, H., Adam, R., Aharonian, F., Ait Benkhali, F., Angüner, E. O., Arcaro, C., Armand, C., Armstrong, T., Ashkar, H., Backes, M., Baghmanyan, V., Barbosa Martins, V., Barnacka, A., Barnard, M., Becherini, Y., Berge, D., Bernlöhr, K., Bi, B., Böttcher, M., Boisson, C., Bolmont, J., de Bony de Lavergne, M., Breuhaus, M., Brun, F., Brun, P., Bryan, M., Büchele, M., Bulik, T., Bylund, T., Caroff, S., Carosi, A., Casanova, S., Chand, T., Chen, A., Cotter, G., Curyło, M., Damascene Mbarubucyeye, J., Davids, I. D., Davies, J., Deil, C., Devin, J., deWilt, P., Dirson, L., Djannati-Ataï, A., Dmytriiev, A., Donath, A., Doroshenko, V., Duffy, C., Dyks, J., Egberts, K., Eichhorn, F., Einecke, S., Emery, G., Ernenwein, J.-P., Feijen, K., Fegan, S., Fiasson, A., Fichet de Clairfontaine, G., Fontaine, G., Funk, S., Füßling, M., Gabici, S., Gallant, Y. A., Giavitto, G., Giunti, L., Glawion, D., Glicenstein, J. F., Gottschall, D., Grondin, M.-H., Hahn, J., Haupt, M., Hermann, G., Hinton, J. A., Hofmann, W., Hoischen, C., Holch, T. L., Holler, M., Hörbe, M., Horns, D., Huber, D., Jamrozy, M., Jankowsky, D., Jankowsky, F., Jardin-Blicq, A., Joshi, V., Jung-Richardt, I., Kasai, E., Kastendieck, M. A., Katarzyński, K., Katz, U., Khangulyan, D., Khélifi, B., Klepser, S., Kluźniak, W., Komin, Nu., Konno, R., Kosack, K., Kostunin, D., Kreter, M., Lamanna, G., Lemière, A., Lemoine-Goumard, M., Lenain, J.-P., Levy, C., Lohse, T., Lypova, I., Mackey, J., Majumdar, J., Malyshev, D., Marandon, V., Marchegiani, P., Marcowith, A., Mares, A., Martí-Devesa, G., Marx, R., Maurin, G., Meintjes, P. J., Meyer, M., Moderski, R., Mohamed, M., Mohrmann, L., Montanari, A., Moore, C., Morris, P., Moulin, E., Muller, J., Murach, T., Nakashima, K., Nayerhoda, A., de Naurois, M., Ndiyavala, H., Niederwanger, F., Niemiec, J., Oakes, L., O'Brien, P., Odaka, H., Ohm, S., Olivera-Nieto, L., de Ona Wilhelmi, E., Ostrowski, M., Panter, M., Panny, S., Parsons, R. D., Peron, G., Peyaud, B., Piel, Q., Pita, S., Poireau, V., Priyana Noel, A., Prokhorov, D. A., Prokoph, H., Pühlhofer, G., Punch, M., Quirrenbach, A., Rauth, R., Reichherzer, P., Reimer, A., Reimer, O., Remy, Q., Renaud, M., Rieger, F., Rinchiuso, L., Romoli, C., Rowell, G., Rudak, B., Ruiz-Velasco, E., Sahakian, V., Sailer, S., Sanchez, D. A., Santangelo, A., Sasaki, M., Scalici, M., Schutte, H. M., Schwanke, U., Schwemmer, S., Seglar-Arroyo, M., Senniappan, M., Seyffert, A. S., Shafi, N., Shiningayamwe, K., Simoni, R., Sinha, A., Sol, H., Specovius, A., Spencer, S., Spir-Jacob, M., Sun, L., Steenkamp, R., Stegmann, C., Steinmassl, S., Steppa, C., Takahashi, T., Tavernier, T., Taylor, A. M., Terrier, R., Tiziani, D., Tluczykont, M., Tomankova, L., Trichard, C., Tsirou, M., Tuffs, R., Uchiyama, Y., van der Walt, D. J., van Eldik, C., van Rensburg, C., van Soelen, B., Vasileiadis, G., Veh, J., Venter, C., Vincent, P., Vink, J., Völk, H. J., Vuillaume, T., Wadiasingh, Z., Wagner, S. J., Watson, J., Werner, F., White, R., Wierzcholska, A., Wong, Yu Wun, Yusafzai, A., Zacharias, M., Zanin, R., Zargaryan, D., Zdziarski, A. A., Zech, A., Zhu, S. J., Zorn, J., Zouari, S., Żywucka, N., Acciari, V. A., Ansoldi, S., Antonelli, L. A., Arbet Engels, A., Artero, M., Asano, K., Baack, D., Babić, A., Baquero, A., Barres de Almeida, U., Barrio, J. A., Becerra González, J., Bednarek, W., Bellizzi, L., Bernardini, E., Bernardos, M., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Busetto, G., Carosi, R., Ceribella, G., Cerruti, M., Chai, Y., Chilingarian, A., Cikota, S., Colak, S. M., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Amico, G., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Delgado Mendez, C., Depaoli, D., Di Pierro, F., Di Venere, L., Do Souto Espiñeira, E., Dominis Prester, D., Donini, A., Dorner, D., Doro, M., Elsaesser, D., Fallah Ramazani, V., Fattorini, A., Ferrara, G., Fonseca, M. V., Font, L., Fruck, C., Fukami, S., García López, R. J., Garczarczyk, M., Gasparyan, S., Gaug, M., Giglietto, N., Giordano, F., Gliwny, P., Godinović, N., Green, J. G., Green, D., Hadasch, D., Hahn, A., Heckmann, L., Herrera, J., Hoang, J., Hrupec, D., Hütten, M., Inada, T., Inoue, S., Ishio, K., Iwamura, Y., Jiménez, I., Jormanainen, J., Jouvin, L., Kajiwara, Y., Karjalainen, M., Kerszberg, D., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., López-Coto, R., López-Moya, M., López-Oramas, A., Loporchio, S., Machado de Oliveira Fraga, B., Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Menchiari, S., Mender, S., Mićanović, S., Miceli, D., Miener, T., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Neustroev, V., Nigro, C., Nilsson, K., Nishijima, K., Noda, K., Nozaki, S., Ohtani, Y., Oka, T., Otero-Santos, J., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Pavletić, L., Peñil, P., Perennes, C., Persic, M., Prada Moroni, P. G., Prandini, E., Priyadarshi, C., Puljak, I., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Saturni, F. G., Schleicher, B., Schmidt, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Spolon, A., Stamerra, A., Strom, D., Strzys, M., Suda, Y., Surić, T., Takahashi, M., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Tosti, L., Truzzi, S., Tutone, A., Ubach, S., van Scherpenberg, J., Vanzo, G., Vazquez Acosta, M., Ventura, S., Verguilov, V., Vigorito, C. F., Vitale, V., Vovk, I., Will, M., Wunderlich, C., Zarić, D., Adams, C. B., Benbow, W., Brill, A., Capasso, M., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Errando, M., A Farrell, K., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Gent, A., Giuri, C., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kieda, D., Kumar, S., Lang, M. J., Lundy, M., Maier, G., Moriarty, P., Mukherjee, R., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Patel, S., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Richards, G. T., Roache, E., Rulten, C., Ryan, J. L., Santander, M., Sembroski, G. H., Shang, R., Weinstein, A., Williams, D. A., J Williamson, T., The Event Horizon Telescope Collaboration, EAVN Collaboration, and The Fermi Large Area Telescope Collaboration
Subjects: 7. Clean energy
Abstract: The astrophysical journal 911(1), L11 (1-43) (2021). doi:10.3847/2041-8213/abef71, In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 10$^9 M_⊙$. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87’s spectrum. We can exclude that the simultaneous $γ$-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the $γ$-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded., Published by Univ., Chicago, Ill. [u.a.]

41. Atmospheric Limitations for High-frequency Ground-based Very Long Baseline Interferometry.

Author: Pesce, Dominic W., Blackburn, Lindy, Chaves, Ryan, Doeleman, Sheperd S., Freeman, Mark, Issaoun, Sara, Johnson, Michael D., Lindahl, Greg, Natarajan, Iniyan, Paine, Scott N., Palumbo, Daniel C. M., Roelofs, Freek, and Tiede, Paul
Subjects: VERY long baseline interferometry, INTERFEROMETRY, VISIBILITY, ATMOSPHERIC models
Abstract: Very long baseline interferometry (VLBI) provides the highest-resolution images in astronomy. The sharpest resolution is nominally achieved at the highest frequencies, but as the observing frequency increases, so too does the atmospheric contribution to the system noise, degrading the sensitivity of the array and hampering detection. In this paper, we explore the limits of high-frequency VLBI observations using ngehtsim, a new tool for generating realistic synthetic data. ngehtsim uses detailed historical atmospheric models to simulate observing conditions, and it employs heuristic visibility detection criteria that emulate single- and multifrequency VLBI calibration strategies. We demonstrate the fidelity of ngehtsim's predictions using a comparison with existing 230 GHz data taken by the Event Horizon Telescope (EHT), and we simulate the expected performance of EHT observations at 345 GHz. Though the EHT achieves a nearly 100% detection rate at 230 GHz, our simulations indicate that it should expect substantially poorer performance at 345 GHz; in particular, observations of M87* at 345 GHz are predicted to achieve detection rates of ≲20% that may preclude imaging. Increasing the array sensitivity through wider bandwidths and/or longer integration times—as enabled through, e.g., the simultaneous multifrequency upgrades envisioned for the next-generation EHT—can improve the 345 GHz prospects and yield detection levels that are comparable to those at 230 GHz. M87* and Sgr A* observations carried out in the atmospheric window around 460 GHz could expect to regularly achieve multiple detections on long baselines, but analogous observations at 690 and 875 GHz consistently obtain almost no detections at all. [ABSTRACT FROM AUTHOR]
Published: 2024
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42. Effects of Earth's Oblateness on Black Hole Imaging through Earth–Space and Space–Space Very Long Baseline Interferometry.

Author: Tamar, Aditya, Hudson, Ben, and Palumbo, Daniel C. M.
Subjects: VERY long baseline interferometry, BLACK holes, ASTROPHYSICAL radiation, EARTH (Planet)
Abstract: Earth-based very long baseline interferometry (VLBI) has made rapid advances in imaging black holes. However, due to the limitations imposed on terrestrial VLBI by the Earth's finite size and turbulent atmosphere, it is imperative to have a space-based component in future VLBI missions. This paper investigates the effect of the Earth's oblateness, also known as the J 2 effect, on orbiters in Earth–space and space–space VLBI. The paper provides an extensive discussion on how the J 2 effect can directly impact orbit selection for black hole observations and how, through informed choices of orbital parameters, the effect can be used to a mission's advantage, a fact that has not been addressed in previous space VLBI investigations. We provide a comprehensive study of how the orbital parameters of several current space VLBI proposals will vary specifically due to the J 2 effect. For black hole accretion flow targets of interest, we demonstrate how the J 2 effect leads to a modest increase in shorter-baseline coverage, filling gaps in the (u, v) plane. Subsequently, we construct a simple analytical formalism that allows isolation of the impact of the J 2 effect on the (u, v) plane without requiring computationally intensive orbit propagation simulations. By directly constructing (u, v) coverage using J 2-affected and J 2-invariant equations of motion, we obtain distinct coverage patterns for M87* and Sgr A* that show extremely dense coverage on short baselines as well as long-term orbital stability on longer baselines. [ABSTRACT FROM AUTHOR]
Published: 2024
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43. Dynamical Properties of Magnetized Low-angular-momentum Accretion Flows around a Kerr Black Hole.

Author: Dihingia, Indu K. and Mizuno, Yosuke
Subjects: KERR black holes, SUPERMASSIVE black holes, ACCRETION (Astrophysics), ANGULAR momentum (Mechanics), GALACTIC center, BLACK holes
Abstract: An essential factor for determining the characteristics of an accretion flow is its angular momentum. According to the angular momentum of the flow, semi-analytical analysis suggests various types of accretion solutions. It is critical to test these with numerical simulations, using the most advanced framework available (general relativistic magnetohydrodynamics), to understand how the flow changes with different angular momentum. By changing the initial condition of the accretion torus minimally, we can simulate a steady, low-angular-momentum accretion flow around a Kerr black hole. We focus primarily on the lower limits of angular momentum and find that an accretion flow with an intermediate range of angular momentum differs significantly from high- or very-low-angular-momentum flows. The intermediate-angular-momentum accretion flow has the highest density, pressure, and temperature near the black hole, making it easier to observe. We find that the density and pressure have power-law scalings ρ ∝ r n −3/2 and p g ∝ r n −5/2, which only hold for very-low-angular-momentum cases. With the increase in flow angular momentum, it develops a nonaxisymmetric nature. In this case, simple self-similarity does not hold. We also find that the sonic surface moves away from the innermost stable circular orbit as the angular momentum decreases. Finally, we emphasize that an intermediate-angular-momentum flow could provide a possible solution to explaining the complex observation features of the supermassive black hole Sgr A* at our galactic center. [ABSTRACT FROM AUTHOR]
Published: 2024
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44. SDSS J075217.84 + 193542.2: X-ray weighing of a secondary BH.

Author: Titarchuk, Lev and Seifina, Elena
Subjects: X-ray binaries, QUASARS, BINARY black holes, SPACE sciences, RADIO jets (Astrophysics), X-rays, ASTROPHYSICAL jets, DOPPLER effect
Abstract: Precise measurements of black hole (BH) masses are necessary to understand the coevolution of these sources and their host galaxies. Sometimes in the center of a galaxy, there is not one but two BHs. The BH duality of the quasar nucleus SDSS J075217.84 + 193542.2 (herein referred to as SDSS J0752) was recently proposed based on the observed strict periodicity of optical emission from the source. We tested this assumption using X-ray observations obtained using Swift/XRT (2008-2010). We fitted the SDSS J075217 spectrum using a Comptonization model and discovered soft X-ray variability in the 0.3-10- keV energy range. We pursued a scenario in which two supermassive BHs at the center of SDSS J0752 form a pair, and the less massive (secondary) BH periodically crosses/punctures the disk around the more massive (primary) BH. We associated these periodic crossings with tidal disruptions of the disk and, as a consequence, with an increase in X-rays observed as a flare in SDSS J0752. During such an X-ray flare event (2008-2010), we discovered a change in the source spectral states and the photon index saturation at the Γ ~ 3 level with mass accretion rate Ṁ. For BH mass scaling, we used OJ 287, M101 ULX-1, and HLX-1 ESO 243-49 as reference sources and found that M[sub SDSS] =9 x107 solar masses, assuming that d[sub SDSS] =500 Mpc. Thus, we obtained a lower limit to a BH mass due to the unknown inclination. In addition, we used the virial mass of the secondary BH based on H[sub α]-line measurements, and we estimated the inclination of the binary at SDSS J0752, i =80°, using a scaling technique. [ABSTRACT FROM AUTHOR]
Published: 2024
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45. The high energy X-ray probe (HEX-P): constraining supermassive black hole growth with population spin measurements.

Author: Piotrowska, J. M., Garcia, J. A., Walton, D. J., Beckmann, R. S., Stern, D., Ballantyne, D. R., Wilkins, D. R., Bianchi, S., Boorman, P. G., Buchner, J., Chen, C.-T., Coppi, P., Dauser, T., Fabian, A. C., Kammoun, E., Madsen, K., Mallick, L., Matt, G., Matzeu, G., and Nardini, E.
Subjects: BLACK holes, X-rays, X-ray spectra, ASTRONOMICAL observatories, SUPERMASSIVE black holes
Abstract: Constraining the primary growth channel of supermassive black holes (SMBHs) remains one the most actively debated questions in the context of cosmological structure formation. Owing to the expected connection between SMBH spin parameter evolution and the accretion and merger history of individual black holes, population spin measurements offer a rare observational window into the cosmic growth of SMBHs. As of today, the most common method for estimating SMBH spin relies on modeling the relativistically broaden atomic profiles in the reflection spectrum observed in X-rays. In this paper, we study the observational requirements needed to confidently distinguish between the primary SMBH growth channels based on their distinct spin-mass distributions predicted by the Horizon-AGN cosmological simulation. Indoing so, we characterize outstanding limitations associated with the existing measurements and discuss the landscape of future observational campaigns which could be planned and executed with future X-ray observatories. We focus our attention on the High-Energy X-ray Probe (HEX-P), a proposed probe-class mission designed to serve the high- energy community in the 2030s. [ABSTRACT FROM AUTHOR]
Published: 2024
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46. Synchrotron Polarization Signatures of Surface Waves in Supermassive Black Hole Jets.

Author: Davelaar, J., Ripperda, B., Sironi, L., Philippov, A. A., Olivares, H., Porth, O., Berg, B. van den, Bronzwaer, T., Chatterjee, K., and Liska, M.
Published: 2023
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47. Simulations of Linear Polarization of Precessing AGN Jets at Parsec Scales.

Author: Todorov, R. V., Kravchenko, E. V., Pashchenko, I. N., and Pushkarev, A. B.
Subjects: ASTROPHYSICAL jets, LINEAR polarization, VERY long baseline interferometry, JET planes, RADARSAT satellites, ACTIVE galactic nuclei, RADIO jets (Astrophysics), BREWSTER'S angle, QUASARS
Abstract: The latest results of the most detailed analysis of multi-epoch polarization-sensitive observations of active galactic nuclei (AGN) jets at parsecs scales by very long baseline interferometry (VLBI) reveal several characteristic patterns of linear polarization distribution and its variability [1, 2]. Some of the observed profiles can be reproduced by a simple model of a jet threaded by a helical magnetic field. However, none of the models presented to date can explain the observed polarization profiles with an increase in its degree towards the edges of the jet, and accompanied by a "fountain" type electrical vector pattern and its high temporal variability in the center. Based on simulations of the VLBI observations of relativistic jets, we show here that the observed transverse linear polarization profiles can be naturally produced in a model of jets precessing on ten-years scales. In this scenario, due to the finite resolution of VLBI arrays, the initially strong polarization along the jet axis is blurred due to the superposition of regions whose polarization angle changes significantly when projected onto the sky plane. In our simulations, we qualitatively reproduce the distribution of the electric vector and its variability, though the polarization distribution images are characterized by a bright spine due to weak suppression of polarized emission, which is poorly consistent with observations of quasars. More effective depolarization can be obtained in models with the suppressed emission of the jet spine. [ABSTRACT FROM AUTHOR]
Published: 2023
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48. Polarized Anisotropic Synchrotron Emission and Absorption and Its Application to Black Hole Imaging.

Author: Galishnikova, Alisa, Philippov, Alexander, and Quataert, Eliot
Subjects: BLACK holes, DISTRIBUTION (Probability theory), PLASMA temperature, PLASMA physics, HIGH temperature plasmas
Abstract: Low-collisionality plasma in a magnetic field generically develops anisotropy in its distribution function with respect to the magnetic field direction. Motivated by the application to radiation from accretion flows and jets, we explore the effect of temperature anisotropy on synchrotron emission. We derive analytically and provide numerical fits for the polarized synchrotron emission and absorption coefficients for a relativistic bi-Maxwellian plasma (we do not consider Faraday conversion/rotation). Temperature anisotropy can significantly change how the synchrotron emission and absorption coefficients depend on observing angle with respect to the magnetic field. The emitted linear polarization fraction does not depend strongly on anisotropy, while the emitted circular polarization does. We apply our results to black hole imaging of Sgr A* and M87* by ray tracing a GRMHD simulation and assuming that the plasma temperature anisotropy is set by the thresholds of kinetic-scale anisotropy-driven instabilities. We find that the azimuthal asymmetry of the 230 GHz images can change by up to a factor of 3, accentuating (T ⊥ > T ∥) or counteracting (T ⊥ < T ∥) the image asymmetry produced by Doppler beaming. This can change the physical inferences from observations relative to models with an isotropic distribution function, e.g., by allowing for larger inclination between the line of sight and spin direction in Sgr A*. The observed image diameter and the size of the black hole shadow can also vary significantly due to plasma temperature anisotropy. We describe how the anisotropy of the plasma can affect future multifrequency and photon ring observations. We also calculate kinetic anisotropy-driven instabilities (mirror, whistler, and firehose) for relativistically hot plasmas. [ABSTRACT FROM AUTHOR]
Published: 2023
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49. A Quantum Parallel Markov Chain Monte Carlo.

Author: Holbrook, Andrew J.
Subjects: MARKOV chain Monte Carlo, QUANTUM computing, PARALLEL algorithms
Abstract: We propose a novel hybrid quantum computing strategy for parallel MCMC algorithms that generate multiple proposals at each step. This strategy makes the rate-limiting step within parallel MCMC amenable to quantum parallelization by using the Gumbel-max trick to turn the generalized accept-reject step into a discrete optimization problem. When combined with new insights from the parallel MCMC literature, such an approach allows us to embed target density evaluations within a well-known extension of Grover's quantum search algorithm. Letting P denote the number of proposals in a single MCMC iteration, the combined strategy reduces the number of target evaluations required from O (P) to O (P) . In the following, we review the rudiments of quantum computing, quantum search and the Gumbel-max trick in order to elucidate their combination for as wide a readership as possible. [ABSTRACT FROM AUTHOR]
Published: 2023
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50. The EB Correlation in Resolved Polarized Images: Connections to the Astrophysics of Black Holes.

Author: Emami, Razieh, Doeleman, Sheperd S., Wielgus, Maciek, Chang, Dominic, Chatterjee, Koushik, Smith, Randall, Liska, Matthew, Steiner, James F., Ricarte, Angelo, Narayan, Ramesh, Tremblay, Grant, Finkbeiner, Douglas, Hernquist, Lars, Chan, Chi-Kwan, Blackburn, Lindy, Prather, Ben S., Tiede, Paul, Broderick, Avery E., Vogelsberger, Mark, and Alcock, Charles
Subjects: BLACK holes, ASTROPHYSICS, ELECTRON spin, FARADAY effect
Abstract: We present an in-depth analysis of the newly proposed correlation function in visibility space, between the E and B modes of linear polarization, hereafter the EB correlation, for a set of time-averaged general relativistic magnetohydrodynamical simulations compared with the phase map from different semianalytic models and the Event Horizon Telescope (EHT) 2017 data for M87*. We demonstrate that the phase map of time-averaged EB correlation contains novel information that might be linked to black hole (BH) spin, accretion state, and electron temperature. A detailed comparison with a semianalytic approach with different azimuthal expansion modes shows that to recover the morphology of real/imaginary part of the correlation function and its phase, we require higher orders of azimuthal modes. To extract the phase features, we use Zernike polynomial reconstruction developing an empirical metric to break degeneracies between models with different BH spins that are qualitatively similar. We use a set of geometrical ring models with various magnetic and velocity field morphologies, showing that both the image space and visibility-based EB -correlation morphologies in magnetically arrested disk simulations can be explained with simple fluid and magnetic field geometries as used in ring models. Standard and normal evolutions by contrast are harder to model, demonstrating that the simple fluid and magnetic field geometries of ring models are not sufficient to describe them owing to higher Faraday rotation depths. A qualitative comparison with the EHT data demonstrates that some of the features in the phase of EB correlation might be well explained by the current models for BH spins and electron temperatures, while others require larger theoretical surveys. [ABSTRACT FROM AUTHOR]
Published: 2023
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