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3,330 results on '"Kim, Jae-Young"'

1. Lost in the curve: Investigating the disappearing knots in the blazar 3C 454.3

Author: Traianou, Efthalia, Krichbaum, Thomas P., Gómez, José L., Lico, Rocco, Paraschos, Georgios Filippos, Cho, Ilje, Ros, Eduardo, Zhao, Guang-Yao, Liodakis, Ioannis, Dahale, Rohan, Toscano, Teresa, Fuentes, Antonio, Foschi, Marianna, Casadio, Carolina, MacDonald, Nicholas, Kim, Jae-Young, Hervet, Olivier, Jorstad, Svetlana, Lobanov, Andrei P., Hodgson, Jeffrey, Myserlis, Ioannis, Agudo, Ivan, Zensus, Anton J., and Marscher, Alan P.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: One of the most well-known extragalactic sources in the sky, quasar 3C 454.3, shows a curved parsec-scale jet that has been exhaustively monitored with very-long-baseline interferometry (VLBI) over the recent years. In this work, we present a comprehensive analysis of four years of high-frequency VLBI observations at 43 GHz and 86 GHz, between 2013-2017, in total intensity and linear polarization. The images obtained from these observations enabled us to study the jet structure and the magnetic field topology of the source on spatial scales down to 4.6 parsec in projected distance. The kinematic analysis reveals the abrupt vanishing of at least four new superluminal jet features in a characteristic jet region (i.e., region C), which is located at an approximate distance of 0.6 milliarcseconds from the VLBI core. Our results support a model in which the jet bends, directing the relativistic plasma flow almost perfectly toward our line of sight, co-spatially with the region where components appear to stop., Comment: 15 pages, 7 figures
Published: 2023

2. Unveiling the Bent Jet Structure and Polarization of OJ 287 at 1.7 GHz with Space VLBI

Author: Cho, Ilje, Gómez, José L., Lico, Rocco, Zhao, Guang-Yao, Traianou, Efthalia, Dahale, Rohan, Fuentes, Antonio, Toscano, Teresa, Foschi, Marianna, Kovalev, Yuri Y., Lobanov, Andrei, Pushkarev, Alexander B., Gurvits, Leonid I., Kim, Jae-Young, Lisakov, Mikhail, Voitsik, Petr, Myserlis, Ioannis, Pötzl, Felix, and Ros, Eduardo
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present total intensity and linear polarization images of OJ287 at 1.68GHz, obtained through space-based VLBI observations with RadioAstron on April 16, 2016. The observations were conducted using a ground array consisting of the VLBA and the EVN. Ground-space fringes were detected with a maximum projected baseline length of 5.6 Earth's diameter, resulting in an angular resolution of 530 uas. With this unprecedented resolution at such a low frequency, the progressively bending jet structure of OJ287 has been resolved up to 10 pc of the projected distance from the radio core. In comparison with close-in-time VLBI observations at 15, 43, 86 GHz from MOJAVE and VLBA-BU-BLAZAR monitoring projects, we obtain the spectral index map showing the opaque core and optically thin jet components. The optically thick core has a brightness temperature of 10$^{13}$ K, and is further resolved into two sub-components at higher frequencies labeled C1 and C2. These sub-components exhibit a transition from optically thick to thin, with a SSA turnover frequency estimated to be 33 and 11.5 GHz, and a turnover flux density 4 and 0.7 Jy, respectively. Assuming a Doppler boosting factor of 10, the SSA values provide the estimate of the magnetic field strengths from SSA of 3.4 G for C1 and 1.0 G for C2. The magnetic field strengths assuming equipartition arguments are also estimated as 2.6 G and 1.6 G, respectively. The integrated degree of linear polarization is found to be approximately 2.5 %, with the electric vector position angle being well aligned with the local jet direction at the core region. This alignment suggests a predominant toroidal magnetic field, which is in agreement with the jet formation model that requires a helical magnetic field anchored to either the black hole ergosphere or the accretion disk. Further downstream, the jet seems to be predominantly threaded by a poloidal magnetic field., Comment: 15 pages, 11 figures, 3 tables
Published: 2023
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3. Filamentary structures as the origin of blazar jet radio variability

Author: Fuentes, Antonio, Gómez, José L., Martí, José M., Perucho, Manel, Zhao, Guang-Yao, Lico, Rocco, Lobanov, Andrei P., Bruni, Gabriele, Kovalev, Yuri Y., Chael, Andrew, Akiyama, Kazunori, Bouman, Katherine L., Sun, He, Cho, Ilje, Traianou, Efthalia, Toscano, Teresa, Dahale, Rohan, Foschi, Marianna, Gurvits, Leonid I., Jorstad, Svetlana, Kim, Jae-Young, Marscher, Alan P., Mizuno, Yosuke, Ros, Eduardo, and Savolainen, Tuomas
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: Supermassive black holes at the centre of active galactic nuclei power some of the most luminous objects in the Universe. Typically, very long baseline interferometric (VLBI) observations of blazars have revealed only funnel-like morphologies with little information of the ejected plasma internal structure, or lacked the sufficient dynamic range to reconstruct the extended jet emission. Here we show microarcsecond-scale angular resolution images of the blazar 3C 279 obtained at 22 GHz with the space VLBI mission RadioAstron, which allowed us to resolve the jet transversely and reveal several filaments produced by plasma instabilities in a kinetically dominated flow. Our high angular resolution and dynamic range image suggests that emission features traveling down the jet may manifest as a result of differential Doppler-boosting within the filaments, as opposed to the standard shock-in-jet model invoked to explain blazar jet radio variability. Moreover, we infer that the filaments in 3C 279 are possibly threaded by a helical magnetic field rotating clockwise, as seen in the direction of the flow motion, with an intrinsic helix pitch angle of ~45 degrees in a jet with a Lorentz factor of ~13 at the time of observation., Comment: 15 pages, 7 figures. Initial version of an article published in Nature Astronomy
Published: 2023
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4. The Repeating Flaring Activity of Blazar AO 0235+164

Author: Pedrosa, Juan Escudero, Agudo, Iván, Tramacere, Andrea, Marscher, Alan P., Jorstad, Svetlana, Weaver, Z. R., Casadio, Carolina, Thum, Clemens, Myserlis, Ioannis, Fuentes, Antonio, Traianou, Efthalia, Kim, Jae-Young, Kramer, Joana, López-Coto, Rubén, D'Ammando, Filippo, Bernardos, M., Bonnoli, Giacomo, Blinov, Dmitriy A., Borman, G. A., Grishina, T. S., Hagen-Thorn, V. A., Kopatskaya, E. N., Larionova, E. G., Larionov, V. M., Larionova, L. V., Morozova, D. A., Savchenko, S. S., Troitskiy, I. S., Troitskaya, Y. V., and Vasilyev, A. A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Context. Blazar AO 0235+164, located at redshift z = 0.94, has undergone several sharp multi-spectral-range flaring episodes during the last decades. In particular, the episodes peaking in 2008 and 2015, that received extensive multi-wavelength coverage, exhibited interesting behavior. Aims. We study the actual origin of these two observed flares by constraining the properties of the observed photo-polarimetric variability, those of the broad-band spectral energy-distribution and the observed time-evolution behavior of the source as seen by ultra-high resolution total-flux and polarimetric Very-long-baseline interferometry (VLBI) imaging. Methods. The analysis of VLBI images allows us to constrain kinematic and geometrical parameters of the 7 mm jet. We use the Discrete Correlation Function to compute the statistical correlation and the delays between emission at different spectral ranges. Multi-epoch modeling of the spectral energy distributions allows us to propose specific models of emission; in particular for the unusual spectral features observed in this source in the X-ray region of the spectrum during strong multi spectral-range flares. Results. We find that these X-ray spectral features can be explained by an emission component originating in a separate particle distribution than the one responsible for the two standard blazar bumps. This is in agreement with the results of our correlation analysis that do not find a strong correlation between the X-rays and the remaining spectral ranges. We find that both external Compton dominated and synchrotron self-Compton dominated models can explain the observed spectral energy distributions. However, synchrotron self-Compton models are strongly favored by the delays and geometrical parameters inferred from the observations.
Published: 2023
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5. All-Trans Retinoic Acid-Induced Cell Surface Heat Shock Protein 90 Mediates Tau Protein Internalization and Degradation in Human Microglia

Author: Nguyen, Ngoc Lan, Hoang, Thi Xoan, and Kim, Jae Young
Published: 2024
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6. A Near Magnetic-to-kinetic Energy Equipartition Flare from the Relativistic Jet in AO 0235+164 during 2013-2019

Author: Cheong, Whee Yeon, Lee, Sang-Sung, Kim, Sang-Hyun, Kang, Sincheol, Kim, Jae Young, Rani, Bindu, Readhead, Anthony C. S., Kiehlmann, Sebastian, Lähteenmäki, Anne, Tornikoski, Merja, Tammi, Joni, Ramakrishnan, Venkatessh, Agudo, Iván, Fuentes, Antonio, Traianou, Efthalia, Escudero, Juan, Thum, Clemens, Myserlis, Ioannis, Casadio, Carolina, and Gurwell, Mark
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We present the multiwavelength flaring activity of the blazar AO 0235+164 during its recent active period from 2013 to 2019. From a discrete correlation function (DCF) analysis, we find a significant (>95%) correlation between radio and $\gamma$-ray light curves with flares at longer wavelengths following flares at shorter wavelengths. We identify a new jet component in 43 GHz VLBA data that was ejected from the radio core on MJD $57246^{+26}_{-30}$ (2015 August 12), during the peak of the 2015 radio flare. From the analysis of the jet component, we derived a Doppler factor of $\delta_{\rm var}=28.5\pm8.4$, a bulk Lorentz factor of $\Gamma=16.8^{+3.6}_{-3.1}$, and an intrinsic viewing angle of $\theta_{\rm v}=1.42^{+1.07}_{-0.52}\textrm{ degrees}$. Investigation of the quasi-simultaneous radio data revealed a partially absorbed spectrum with the turnover frequency varying in the range of $10-70$ GHz and the peak flux density varying in the range of $0.7-4$ Jy. We find the synchrotron self-absorption magnetic field strength to be $B_{\rm SSA}=15.3^{+12.6}_{-14.0}$ mG at the peak of the 2015 radio flare, which is comparable to the equipartition magnetic field strength of $B_{\rm EQ}=43.6^{+10.6}_{-10.4}$ mG calculated for the same epoch. Additional analysis of the radio emission region in the relativistic jet of AO 0235+164 suggests that it did not significantly deviate from equipartition during its recent flaring activity., Comment: 13 pages, 11 figures, 4 tables; Accepted for publication in MNRAS
Published: 2023

7. Precessing jet nozzle connecting to a spinning black hole in M87

Author: Cui, Yuzhu, Hada, Kazuhiro, Kawashima, Tomohisa, Kino, Motoki, Lin, Weikang, Mizuno, Yosuke, Ro, Hyunwook, Honma, Mareki, Yi, Kunwoo, Yu, Jintao, Park, Jongho, Jiang, Wu, Shen, Zhiqiang, Kravchenko, Evgeniya, Algaba, Juan-Carlos, Cheng, Xiaopeng, Cho, Ilje, Giovannini, Gabriele, Giroletti, Marcello, Jung, Taehyun, Lu, Ru-Sen, Niinuma, Kotaro, Oh, Junghwan, Ohsuga, Ken, Sawada-Satoh, Satoko, Sohn, Bong Won, Takahashi, Hiroyuki R., Takamura, Mieko, Tazaki, Fumie, Trippe, Sascha, Wajima, Kiyoaki, Akiyama, Kazunori, An, Tao, Asada, Keiichi, Buttaccio, Salvatore, Byun, Do-Young, Cui, Lang, Hagiwara, Yoshiaki, Hirota, Tomoya, Hodgson, Jeffrey, Kawaguchi, Noriyuki, Kim, Jae-Young, Lee, Sang-Sung, Lee, Jee Won, Lee, Jeong Ae, Maccaferri, Giuseppe, Melis, Andrea, Melnikov, Alexey, Migoni, Carlo, Oh, Se-Jin, Sugiyama, Koichiro, Wang, Xuezheng, Zhang, Yingkang, Chen, Zhong, Hwang, Ju-Yeon, Jung, Dong-Kyu, Kim, Hyo-Ryoung, Kim, Jeong-Sook, Kobayashi, Hideyuki, Li, Bin, Li, Guanghui, Li, Xiaofei, Liu, Zhiyong, Liu, Qinghui, Liu, Xiang, Oh, Chung-Sik, Oyama, Tomoaki, Roh, Duk-Gyoo, Wang, Jinqing, Wang, Na, Wang, Shiqiang, Xia, Bo, Yan, Hao, Yeom, Jae-Hwan, Yonekura, Yoshinori, Yuan, Jianping, Zhang, Hua, Zhao, Rongbing, and Zhong, Weiye
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: The nearby radio galaxy M87 offers a unique opportunity to explore the connections between the central supermassive black hole and relativistic jets. Previous studies of the inner region of M87 revealed a wide opening angle for the jet originating near the black hole. The Event Horizon Telescope resolved the central radio source and found an asymmetric ring structure consistent with expectations from General Relativity. With a baseline of 17 years of observations, there was a shift in the jet's transverse position, possibly arising from an eight to ten-year quasi-periodicity. However, the origin of this sideways shift remains unclear. Here we report an analysis of radio observations over 22 years that suggests a period of about 11 years in the position angle variation of the jet. We infer that we are seeing a spinning black hole that induces the Lense-Thirring precession of a misaligned accretion disk. Similar jet precession may commonly occur in other active galactic nuclei but has been challenging to detect owing to the small magnitude and long period of the variation., Comment: 41 pages, 7 figures, 7 tables
Published: 2023
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8. A search for pulsars around Sgr A* in the first Event Horizon Telescope dataset

Author: Torne, Pablo, Liu, Kuo, Eatough, Ralph P., Wongphechauxsorn, Jompoj, Cordes, James M., Desvignes, Gregory, De Laurentis, Mariafelicia, Kramer, Michael, Ransom, Scott M., Chatterjee, Shami, Wharton, Robert, Karuppusamy, Ramesh, Blackburn, Lindy, Janssen, Michael, Chan, Chi-kwan, Crew, Geoffrey B., Matthews, Lynn D., Goddi, Ciriaco, Rottmann, Helge, Wagner, Jan, Sanchez, Salvador, Ruiz, Ignacio, Abbate, Federico, Bower, Geoffrey C., Salamanca, Juan J., Gomez-Ruiz, Arturo I., Herrera-Aguilar, Alfredo, Jiang, Wu, Lu, Ru-Sen, Pen, Ue-Li, Raymond, Alexander W., Shao, Lijing, Shen, Zhiqiang, Paubert, Gabriel, Sanchez-Portal, Miguel, Kramer, Carsten, Castillo, Manuel, Navarro, Santiago, John, David, Schuster, Karl-Friedrich, Johnson, Michael D., Rygl, Kazi L. J., Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Bach, Uwe, Baczko, Anne-Kathrin, Ball, David, Balokovic, Mislav, Barrett, John, Bauboeck, Michi, Benson, Bradford A., Bintley, Dan, Blundell, Raymond, Bouman, Katherine L., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Bustamante, Sandra, Byun, Do-Young, Carlstrom, John E., Ceccobello, Chiara, Chael, Andrew, Chang, Dominic O., Chatterjee, Koushik, Chen, Ming-Tang, Chen, Yongjun, Cheng, Xiaopeng, Cho, Ilje, Christian, Pierre, Conroy, Nicholas S., Conway, John E., Crawford, Thomas M., Cruz-Osorio, Alejandro, Cui, Yuzhu, Dahale, Rohan, Davelaar, Jordy, Deane, Roger, Dempsey, Jessica, Dexter, Jason, Dhruv, Vedant, Doeleman, Sheperd S., Dougal, Sean, Dzib, Sergio A., Emami, Razieh, Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Foschi, Marianna, Fraga-Encinas, Raquel, Freeman, William T., Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, Gammie, Charles F., Garcia, Roberto, Gentaz, Olivier, Georgiev, Boris, Gold, Roman, Gomez, Jose L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Haworth, Kari, Hecht, Michael H., Hesper, Ronald, Heumann, Dirk, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Impellizzeri, C. M. Violette, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Jeter, Britton, Jimenez-Rosales, Alejandra, Jorstad, Svetlana, Joshi, Abhishek V., Jung, Taehyun, Karami, Mansour, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kocherlakota, Prashant, Kofuji, Yutaro, Koyama, Shoko, Krichbaum, Thomas P., Kuo, Cheng-Yu, La Bella, Noemi, Lauer, Tod R., Lee, Daeyoung, Lee, Sang-Sung, Leung, Po Kin, Levis, Aviad, Li, Zhiyuan, Lico, Rocco, Lindahl, Greg, Lindqvist, Michael, Lisakov, Mikhail, Liu, Jun, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin J., MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Marti-Vidal, Ivan, Matsushita, Satoki, Medeiros, Lia, Menten, Karl M., Michalik, Daniel, Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Muller, Cornelia, Muller, Hendrik, Mus, Alejandro, Musoke, Gibwa, Myserlis, Ioannis, Nadolski, Andrew, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Oh, Junghwan, Okino, Hiroki, Olivares, Hector, Ortiz-Leon, Gisela N., Oyama, Tomoaki, Ozel, Feryal, Palumbo, Daniel C. M., Paraschos, Georgios Filippos, Park, Jongho, Parsons, Harriet, Patel, Nimesh, Pesce, Dominic W., Pietu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Potzl, Felix M., Prather, Ben, Preciado-Lopez, Jorge A., Psaltis, Dimitrios, Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Rezzolla, Luciano, Ricarte, Angelo, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Romero-Cañizales, Cristina, Roshanineshat, Arash, Roy, Alan L., Ruszczyk, Chet, Sanchez-Arguelles, David, Sasada, Mahito, Satapathy, Kaushik, Savolainen, Tuomas, Schloerb, F. Peter, Schonfeld, Jonathan, Small, Des, Sohn, Bong Won, SooHoo, Jason, Souccar, Kamal, Sun, He, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Toscano, Teresa, Traianou, Efthalia, Trent, Tyler, Trippe, Sascha, Turk, Matthew, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Vos, Jesse, Ward-Thompson, Derek, Wardle, John, Weintroub, Jonathan, Wex, Norbert, Wielgus, Maciek, Wiik, Kaj, Witzel, Gunther, Wondrak, Michael F., Wong, George N., Wu, Qingwen, Yadlapalli, Nitika, Yamaguchi, Paul, Yfantis, Aristomenis, Yoon, Doosoo, Young, Andre, Young, Ken, Younsi, Ziri, Yu, Wei, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhang, Shuo, Zhao, Guang-Yao, and Zhao, Shan-Shan
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The Event Horizon Telescope (EHT) observed in 2017 the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz ($\lambda$=1.3 mm). The fundamental physics tests that even a single pulsar orbiting Sgr A* would enable motivate searching for pulsars in EHT datasets. The high observing frequency means that pulsars - which typically exhibit steep emission spectra - are expected to be very faint. However, it also negates pulse scattering, an effect that could hinder pulsar detections in the Galactic Center. Additionally, magnetars or a secondary inverse Compton emission could be stronger at millimeter wavelengths than at lower frequencies. We present a search for pulsars close to Sgr A* using the data from the three most-sensitive stations in the EHT 2017 campaign: the Atacama Large Millimeter/submillimeter Array, the Large Millimeter Telescope and the IRAM 30 m Telescope. We apply three detection methods based on Fourier-domain analysis, the Fast-Folding-Algorithm and single pulse search targeting both pulsars and burst-like transient emission; using the simultaneity of the observations to confirm potential candidates. No new pulsars or significant bursts were found. Being the first pulsar search ever carried out at such high radio frequencies, we detail our analysis methods and give a detailed estimation of the sensitivity of the search. We conclude that the EHT 2017 observations are only sensitive to a small fraction ($\lesssim$2.2%) of the pulsars that may exist close to Sgr A*, motivating further searches for fainter pulsars in the region., Comment: 33 pages, 7 figures, 6 Tables. Accepted for publication in ApJ
Published: 2023

9. Label-Free and Real-Time Electrical Impedance Monitoring of Macrophage Polarization of THP-1 Monocytes on Indium Tin Oxide Electrode

Author: Pham, Duc-Trung, Pham, Hoang Lan, Le, Hien T. Ngoc, Tieu, My-Van, Kim, Daesoo, Kim, Jae Young, and Cho, Sungbo
Published: 2024
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10. Accuracy improvement of CFD modeling of a hydraulics with wood pellet combustion operating in a full-loop circulating fluidized bed combustor (CFBC)

Author: Park, Sang Shin, Moon, Ji-Hong, Yoon, Sang-Hee, Baek, Geon-Uk, Jo, Sungho, Park, Sung-Jin, Kim, Jae-Young, Yoon, Sang-Jun, Lee, Jae-Goo, Ra, Ho Won, Yoon, Sung-Min, and Mun, Tae-Young
Published: 2024
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11. Two lineages of Lemna aequinoctialis (Araceae, Lemnoideae) based on physiology, morphology, and phylogeny

Author: Lee, Yuri, Kato, Syou, Kim, Jae Young, Shimono, Yoshiko, and Shiga, Takashi
Published: 2024
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12. Double SSA Spectrum and Magnetic Field Strength of the FSRQ 3C 454.3

Author: Jeong, Hyeon-Woo, Lee, Sang-Sung, Cheong, Whee Yeon, Kim, Jae-Young, Lee, Jee Won, Kang, Sincheol, Kim, Sang-Hyun, Rani, B., Park, Jongho, and Gurwell, Mark A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We present the results of a radio multi-frequency ($\rm 3-340~GHz$) study of the blazar 3C~454.3. After subtracting the quiescent spectrum corresponding to optically thin emission, we found two individual synchrotron self-absorption (SSA) features in the wide-band spectrum. The one SSA had a relatively low turnover frequency ($\nu_{\rm m}$) in the range of $\rm 3-37~GHz$ (lower $\nu_{\rm m}$ SSA spectrum, LSS), and the other one had a relatively high $\nu_{\rm m}$ of $\rm 55-124~GHz$ (higher $\nu_{\rm m}$ SSA spectrum, HSS). Using the SSA parameters, we estimated magnetic field strengths at the surface where optical depth $\tau=1$. The estimated magnetic field strengths were $\rm >7~mG$ and $\rm >0.2~mG$ for the LSS and HSS, respectively. The LSS emitting region was magnetically dominated before the June 2014 $\gamma$-ray flare. The quasi-stationary component (C), $\sim 0.6~{\rm mas}$ apart from the 43 GHz radio core, became brighter than the core with decreasing observing frequency, and we found that component C was related to the LSS. A decrease in jet width was found near component C. As a moving component, K14 approached component C, and the flux density of the component was enhanced while the angular size decreased. The high intrinsic brightness temperature in the fluid frame was obtained as $T_{\rm B, int} \approx (7.0\pm1.0) \times 10^{11}~{\rm K}$ from the jet component after the 2015 August $\gamma$-ray flare, suggesting that component C is a high-energy emitting region. The observed local minimum of jet width and re-brightening behavior suggest a possible recollimation shock in component C., Comment: 16 pages, 12 figures, 5 tables, Accepted for publication in MNRAS
Published: 2023
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13. Darwin: A DRAM-based Multi-level Processing-in-Memory Architecture for Data Analytics

Author: Kim, Donghyuk, Kim, Jae-Young, Han, Wontak, Won, Jongsoon, Choi, Haerang, Kwon, Yongkee, and Kim, Joo-Young
Subjects: Electrical Engineering and Systems Science - Systems and Control
Abstract: Processing-in-memory (PIM) architecture is an inherent match for data analytics application, but we observe major challenges to address when accelerating it using PIM. In this paper, we propose Darwin, a practical LRDIMM-based multi-level PIM architecture for data analytics, which fully exploits the internal bandwidth of DRAM using the bank-, bank group-, chip-, and rank-level parallelisms. Considering the properties of data analytics operators and DRAM's area constraints, Darwin maximizes the internal data bandwidth by placing the PIM processing units, buffers, and control circuits across the hierarchy of DRAM. More specifically, it introduces the bank processing unit for each bank in which a single instruction multiple data (SIMD) unit handles regular data analytics operators and bank group processing unit for each bank group to handle workload imbalance in the condition-oriented data analytics operators. Furthermore, Darwin supports a novel PIM instruction architecture that concatenates instructions for multiple thread executions on bank group processing entities, addressing the command bottleneck by enabling separate control of up to 512 different in-memory processing units simultaneously. We build a cycle-accurate simulation framework to evaluate Darwin with various DRAM configurations, optimization schemes and workloads. Darwin achieves up to 14.7x speedup over the non-optimized version. Finally, the proposed Darwin architecture achieves 4.0x-43.9x higher throughput and reduces energy consumption by 85.7% than the baseline CPU system (Intel Xeon Gold 6226 + 4 channels of DDR4-2933). Compared to the state-of-the-art PIM, Darwin achieves up to 7.5x and 7.1x in the basic query operators and TPC-H queries, respectively. Darwin is based on the latest GDDR6 and requires only 5.6% area overhead, suggesting a promising PIM solution for the future main memory system., Comment: 14 pages, 16 figures
Published: 2023

14. A ring-like accretion structure in M87 connecting its black hole and jet

Author: Lu, Ru-Sen, Asada, Keiichi, Krichbaum, Thomas P., Park, Jongho, Tazaki, Fumie, Pu, Hung-Yi, Nakamura, Masanori, Lobanov, Andrei, Hada, Kazuhiro, Akiyama, Kazunori, Kim, Jae-Young, Marti-Vidal, Ivan, Gómez, José L., Kawashima, Tomohisa, Yuan, Feng, Ros, Eduardo, Alef, Walter, Britzen, Silke, Bremer, Michael, Broderick, Avery E., Doi, Akihiro, Giovannini, Gabriele, Giroletti, Marcello, Ho, Paul T. P., Honma, Mareki, Hughes, David H., Inoue, Makoto, Jiang, Wu, Kino, Motoki, Koyama, Shoko, Lindqvist, Michael, Liu, Jun, Marscher, Alan P., Matsushita, Satoki, Nagai, Hiroshi, Rottmann, Helge, Savolainen, Tuomas, Schuster, Karl-Friedrich, Shen, Zhi-Qiang, de Vicente, Pablo, Walker, R. Craig, Yang, Hai, Zensus, J. Anton, Algaba, Juan Carlos, Allardi, Alexander, Bach, Uwe, Berthold, Ryan, Bintley, Dan, Byun, Do-Young, Casadio, Carolina, Chang, Shu-Hao, Chang, Chih-Cheng, Chang, Song-Chu, Chen, Chung-Chen, Chen, Ming-Tang, Chilson, Ryan, Chuter, Tim C., Conway, John, Crew, Geoffrey B., Dempsey, Jessica T., Dornbusch, Sven, Faber, Aaron, Friberg, Per, García, Javier González, Garrido, Miguel Gómez, Han, Chih-Chiang, Han, Kuo-Chang, Hasegawa, Yutaka, Herrero-Illana, Ruben, Huang, Yau-De, Huang, Chih-Wei L., Impellizzeri, Violette, Jiang, Homin, Jinchi, Hao, Jung, Taehyun, Kallunki, Juha, Kirves, Petri, Kimura, Kimihiro, Koay, Jun Yi, Koch, Patrick M., Kramer, Carsten, Kraus, Alex, Kubo, Derek, Kuo, Cheng-Yu, Li, Chao-Te, Lin, Lupin Chun-Che, Liu, Ching-Tang, Liu, Kuan-Yu, Lo, Wen-Ping, Lu, Li-Ming, MacDonald, Nicholas, Martin-Cocher, Pierre, Messias, Hugo, Meyer-Zhao, Zheng, Minter, Anthony, Nair, Dhanya G., Nishioka, Hiroaki, Norton, Timothy J., Nystrom, George, Ogawa, Hideo, Oshiro, Peter, Patel, Nimesh A, Pen, Ue-Li, Pidopryhora, Yurii, Pradel, Nicolas, Raffin, Philippe A., Rao, Ramprasad, Ruiz, Ignacio, Sanchez, Salvador, Shaw, Paul, Snow, William, Sridharan, T. K., Srinivasan, Ranjani, Tercero, Belén, Torne, Pablo, Traianou, Efthalia, Wagner, Jan, Walther, Craig, Wei, Ta-Shun, Yang, Jun, and Yu, Chen-Yu
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies, General Relativity and Quantum Cosmology
Abstract: The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation^{1,2}. Event Horizon Telescope observations of M87 in 2017, at a wavelength of 1.3 mm, revealed a ring-like structure, which was interpreted as gravitationally lensed emission around a central black hole^3. Here we report images of M87 obtained in 2018, at a wavelength of 3.5 mm, showing that the compact radio core is spatially resolved. High-resolution imaging shows a ring-like structure of 8.4_{-1.1}^{+0.5} Schwarzschild radii in diameter, approximately 50% larger than that seen at 1.3 mm. The outer edge at 3.5 mm is also larger than that at 1.3 mm. This larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects in addition to the gravitationally lensed ring-like emission. The images show that the edge-brightened jet connects to the accretion flow of the black hole. Close to the black hole, the emission profile of the jet-launching region is wider than the expected profile of a black-hole-driven jet, suggesting the possible presence of a wind associated with the accretion flow., Comment: 50 pages, 18 figures, 3 tables, author's version of the paper published in Nature
Published: 2023
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15. RadioAstron Space VLBI Imaging of the jet in M87: I. Detection of high brightness temperature at 22 GHz

Author: Kim, Jae-Young, Savolainen, Tuomas, Voitsik, Petr, Kravchenko, Evgeniya V., Lisakov, Mikhail M., Kovalev, Yuri Y., Müller, Hendrik, Lobanov, Andrei P., Sokolovsky, Kirill V., Bruni, Gabriele, Edwards, Philip G., Reynolds, Cormac, Bach, Uwe, Gurvits, Leonid I., Krichbaum, Thomas P., Hada, Kazuhiro, Giroletti, Marcello, Orienti, Monica, Anderson, James M., Lee, Sang-Sung, Sohn, Bong Won, and Zensus, J. Anton
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present results from the first 22 GHz space very-long-baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part of the Nearby AGN Key Science Program, the source was observed in Feb 2014 at 22 GHz with 21 ground stations, reaching projected $(u,v)$-spacings up to $\sim11\,$G$\lambda$. The imaging experiment was complemented by snapshot RadioAstron data of M87 obtained during 2013--2016 from the AGN Survey Key Science Program. Their longest baselines extend up to $\sim25\,$G$\lambda$. For all these measurements, fringes are detected only up to $\sim$2.8 Earth Diameter or $\sim$3 G$\lambda$ baseline lengths, resulting in a new image with angular resolution of $\sim150\,\mu$as or $\sim20$ Schwarzschild radii spatial resolution. The new image not only shows edge-brightened jet and counterjet structures down to submilliarcsecond scales but also clearly resolves the VLBI core region. While the overall size of the core is comparable to those reported in the literature, the ground-space fringe detection and slightly super-resolved RadioAstron image suggest the presence of substructures in the nucleus, whose minimum brightness temperature exceeds $T_{\rm B, min}\sim10^{12}\,$K. It is challenging to explain the origin of this record-high $T_{\rm B, min}$ value for M87 by pure Doppler boosting effect with a simple conical jet geometry and known jet speed. Therefore, this can be evidence for more extreme Doppler boosting due to a blazar-like small jet viewing angle or highly efficient particle acceleration processes occurring already at the base of the outflow., Comment: 27 pages, 13 figures, accepted for publication in ApJ
Published: 2023
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16. Capella: A Space-only High-frequency Radio VLBI Network Formed by a Constellation of Small Satellites

Author: Trippe, Sascha, Jung, Taehyun, Lee, Jung-Won, Wagner, Jan, Han, Jeong-Yeol, Kang, Wonseok, Kyeong, Jae-Hyun, Oh, Junghwan, Kim, Jae-Young, Park, Jongho, and Hodgson, Jeffrey A.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: Very long baseline radio interferometry (VLBI) with ground-based observatories is limited by the size of Earth, the geographic distribution of antennas, and the transparency of the atmosphere. In this whitepaper, we present Capella, a tentative design of a space-only VLBI system. Using four small (<500 kg) satellites in two orthogonal polar low-Earth orbit planes, and single-band heterodyne receivers operating at frequencies around 690 GHz, the interferometer is able to achieve angular resolutions of approximately 7 microarcsec. Within a total observing time of three days, a near-complete uv plane coverage can be reached. The technology for all key components required for Capella - radio telescope, receiver, sampler, recorder, frequency standard, positioning system, data downlink, and pointing control system - is already available, partially off-the-shelf. Making realistic assumptions, the science payload of each satellite has a mass of about 190 kg and consumes about 460 W of power. The data from the telescopes can be correlated on the ground using dedicated versions of existing Fourier transform (FX) software correlators. With the specifications assumed in this whitepaper, Capella will be able to address a range of science cases, including: photon rings around supermassive black holes; the acceleration and collimation zones of plasma jets emitted from the vicinity of supermassive black holes; the chemical composition of accretion flows into active galactic nuclei through observations of molecular absorption lines; mapping supermassive binary black holes; the magnetic activity of stars; and nova eruptions of symbiotic binary stars - and, like any substantially new observing technique, has the potential for unexpected discoveries., Comment: 20 pages, 3 figures, 1 table. Whitepaper version 1.4. Updates: frequency reference, sensitivity, mass and power budgets, list of authors. Abstract abridged. Living document, will be updated when necessary
Published: 2023

17. Comparison of Polarized Radiative Transfer Codes used by the EHT Collaboration

Author: Prather, Ben S., Dexter, Jason, Moscibrodzka, Monika, Pu, Hung-Yi, Bronzwaer, Thomas, Davelaar, Jordy, Younsi, Ziri, Gammie, Charles F., Gold, Roman, Wong, George N., Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Bach, Uwe, Baczko, Anne-Kathrin, Ball, David, Baloković, Mislav, Barrett, John, Bauböck, Michi, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bustamante, Sandra, Byun, Do-Young, Carlstrom, John E., Ceccobello, Chiara, Chael, Andrew, Chan, Chi-kwan, Chang, Dominic O., Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Cheng, Xiaopeng, Cho, Ilje, Christian, Pierre, Conroy, Nicholas S., Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dhruv, Vedant, Doeleman, Sheperd S., Dougal, Sean, Dzib, Sergio A., Eatough, Ralph P., Emami, Razieh, Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Fraga-Encinas, Raquel, Freeman, William T., Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, García, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gómez-Ruiz, Arturo I., Gómez, José L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Haworth, Kari, Hecht, Michael H., Hesper, Ronald, Heumann, Dirk, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Impellizzeri, C. M. Violette, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jeter, Britton, Jiang, Wu, Jiménez-Rosales, Alejandra, Johnson, Michael D., Jorstad, Svetlana, Joshi, Abhishek V., Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kocherlakota, Prashant, Kofuji, Yutaro, Koyama, Shoko, Kramer, Carsten, Kramer, Michael, Krichbaum, Thomas P., Kuo, Cheng-Yu, La Bella, Noemi, Lauer, Tod R., Lee, Daeyoung, Lee, Sang-Sung, Leung, Po Kin, Levis, Aviad, Li, Zhiyuan, Lico, Rocco, Lindahl, Greg, Lindqvist, Michael, Lisakov, Mikhail, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin J., Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Iván, Matsushita, Satoki, Matthews, Lynn D., Medeiros, Lia, Menten, Karl M., Michalik, Daniel, Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moriyama, Kotaro, Müller, Cornelia, Mus, Alejandro, Musoke, Gibwa, Myserlis, Ioannis, Nadolski, Andrew, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Fuentes, Santiago Navarro, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Oh, Junghwan, Okino, Hiroki, Olivares, Héctor, Ortiz-León, Gisela N., Oyama, Tomoaki, Özel, Feryal, Palumbo, Daniel C. M., Paraschos, Georgios Filippos, Park, Jongho, Parsons, Harriet, Patel, Nimesh, Pen, Ue-Li, Pesce, Dominic W., Piétu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Pötzl, Felix M., Preciado-López, Jorge A., Psaltis, Dimitrios, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Rezzolla, Luciano, Ricarte, Angelo, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Romero-Cañizales, Cristina, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruiz, Ignacio, Ruszczyk, Chet, Rygl, Kazi L. J., Sánchez, Salvador, Sánchez-Argüelles, David, Sánchez-Portal, Miguel, Sasada, Mahito, Satapathy, Kaushik, Savolainen, Tuomas, Schloerb, F. Peter, Schonfeld, Jonathan, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Souccar, Kamal, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Torne, Pablo, Traianou, Efthalia, Trent, Tyler, Trippe, Sascha, Turk, Matthew, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Vos, Jesse, Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wielgus, Maciek, Wiik, Kaj, Witzel, Gunther, Wondrak, Michael F., Wu, Qingwen, Yamaguchi, Paul, Yfantis, Aristomenis, Yoon, Doosoo, Young, André, Young, Ken, Yu, Wei, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhang, Shuo, Zhao, Guang-Yao, and Zhao, Shan-Shan
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Interpretation of resolved polarized images of black holes by the Event Horizon Telescope (EHT) requires predictions of the polarized emission observable by an Earth-based instrument for a particular model of the black hole accretion system. Such predictions are generated by general relativistic radiative transfer (GRRT) codes, which integrate the equations of polarized radiative transfer in curved spacetime. A selection of ray-tracing GRRT codes used within the EHT collaboration is evaluated for accuracy and consistency in producing a selection of test images, demonstrating that the various methods and implementations of radiative transfer calculations are highly consistent. When imaging an analytic accretion model, we find that all codes produce images similar within a pixel-wise normalized mean squared error (NMSE) of 0.012 in the worst case. When imaging a snapshot from a cell-based magnetohydrodynamic simulation, we find all test images to be similar within NMSEs of 0.02, 0.04, 0.04, and 0.12 in Stokes I, Q, U , and V respectively. We additionally find the values of several image metrics relevant to published EHT results to be in agreement to much better precision than measurement uncertainties., Comment: Accepted for publication in ApJ
Published: 2023
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18. Spectral analysis of a parsec-scale jet in M87: Observational constraint on the magnetic field strengths in the jet

Author: Ro, Hyunwook, Kino, Motoki, Sohn, Bong Won, Hada, Kazuhiro, Park, Jongho, Nakamura, Masanori, Cui, Yuzhu, Yi, Kunwoo, Chung, Aeree, Hodgson, Jeffrey, Kawashima, Tomohisa, An, Tao, Trippe, Sascha, Algaba, Juan-Carlos, Kim, Jae-Young, Sawada-Satoh, Satoko, Wajima, Kiyoaki, Shen, Zhiqiang, Cheng, Xiaopeng, Cho, Ilje, Jiang, Wu, Jung, Taehyun, Lee, Jee-Won, Niinuma, Kotaro, Oh, Junghwan, Tazaki, Fumie, Zhao, Guang-Yao, Akiyama, Kazunori, Honma, Mareki, Lee, Jeong Ae, Lu, Rusen, Zhang, Yingkang, Asada, Keiichi, Cui, Lang, Hagiwara, Yoshiaki, Hirota, Tomoya, Kawaguchi, Noriyuki, Koyama, Shoko, Lee, Sang-Sung, Oh, Se-Jin, Sugiyama, Koichiro, Takamura, Mieko, Wang, Xuezheng, Hwang, Ju-Yeon, Jung, Dong-Kyu, Kim, Hyo-Ryoung, Kim, Jeong-Sook, Kobayashi, Hideyuki, Oh, Chung-Sik, Oyama, Tomoaki, Roh, Duk-Gyoo, and Yeom, Jae-Hwan
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Because of its proximity and the large size of its black hole, M87 is one of the best targets for studying the launching mechanism of active galactic nucleus jets. Currently, magnetic fields are considered to be an essential factor in the launching and accelerating of the jet. However, current observational estimates of the magnetic field strength of the M87 jet are limited to the innermost part of the jet or to HST-1. No attempt has yet been made to measure the magnetic field strength in between. We aim to infer the magnetic field strength of the M87 jet out to a distance of several thousand $r_s$ by tracking the distance-dependent changes in the synchrotron spectrum of the jet from high-resolution very long baseline interferometry observations. In order to obtain high-quality spectral index maps, quasi-simultaneous observations at 22 and 43 GHz were conducted using the KVN and VERA Array (KaVA) and the VLBA. We compared the spectral index distributions obtained from the observations with a model and placed limits on the magnetic field strengths as a function of distance. The overall spectral morphology is broadly consistent over the course of these observations. The observed synchrotron spectrum rapidly steepens from $\alpha_{22-43 GHz}$ ~ -0.7 at ~ 2 mas to $\alpha_{22-43 GHz}$ ~ -2.5 at ~ 6 mas. A spectral index model in which nonthermal electron injections inside the jet decrease with distance can adequately reproduce the observed trend. This suggests the magnetic field strength of the jet at a distance of 2 - 10 mas (~ 900 $r_s$ - ~ 4500 $r_s$ in the deprojected distance) has a range of $B=(0.3 - 1.0 G)(z/2 mas)^{-0.73}$. Extrapolating to the EHT scale yields consistent results, suggesting that the majority of the magnetic flux of the jet near the black hole is preserved out to ~ 4500 $r_s$ without significant dissipation., Comment: 16 pages, 9 figures. Accepted for publication in Astronomy & Astrophysics
Published: 2023
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19. The Event Horizon Telescope Image of the Quasar NRAO 530

Author: Jorstad, Svetlana, Wielgus, Maciek, Lico, Rocco, Issaoun, Sara, Broderick, Avery E., Pesce, Dominic W., Liu, Jun, Zhao, Guang-Yao, Krichbaum, Thomas P., Blackburn, Lindy, Chan, Chi-Kwan, Janssen, Michael, Ramakrishnan, Venkatessh, Akiyama, Kazunori, Alberdi, Antxon, Algaba, Juan Carlos, Bouman, Katherine L., Cho, Ilje, Fuentes, Antonio, Gomez, Jose L., Gurwell, Mark, Johnson, Michael D., Kim, Jae-Young, Lu, Ru-Sen, Marti-Vidal, Ivan, Moscibrodzka, Monika, Poetzl, Felix M., Traianou, Efthalia, van Bemmel, Ilse, and Collaboration, the Event Horizon Telescope
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We report on the observations of the quasar NRAO 530 with the Event Horizon Telescope (EHT) on 2017 April 5-7, when NRAO 530 was used as a calibrator for the EHT observations of Sagittarius A*. At z=0.902 this is the most distant object imaged by the EHT so far. We reconstruct the first images of the source at 230 GHz, at an unprecedented angular resolution of $\sim$ 20 $\mu$as, both in total intensity and in linear polarization. We do not detect source variability, allowing us to represent the whole data set with static images. The images reveal a bright feature located on the southern end of the jet, which we associate with the core. The feature is linearly polarized, with a fractional polarization of $\sim$5-8% and has a sub-structure consisting of two components. Their observed brightness temperature suggests that the energy density of the jet is dominated by the magnetic field. The jet extends over 60 $\mu$as along a position angle PA$\sim -$28$^\circ$. It includes two features with orthogonal directions of polarization (electric vector position angle, EVPA), parallel and perpendicular to the jet axis, consistent with a helical structure of the magnetic field in the jet. The outermost feature has a particularly high degree of linear polarization, suggestive of a nearly uniform magnetic field. Future EHT observations will probe the variability of the jet structure on ${\mu}$as scales, while simultaneous multi-wavelength monitoring will provide insight into the high energy emission origin.
Published: 2023
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20. Developmental roles of glomerular epithelial protein-1 in mice molar morphogenesis

Author: Neupane, Sanjiv, Aryal, Yam Prasad, Kwak, Hee-Jin, Lee, Sung-Gwon, Kim, Tae-Young, Pokharel, Elina, Kim, Ji-Youn, Kim, Jung-Hyeuk, Sohn, Wern-Joo, An, Seo-Young, An, Chang-Hyeon, Jung, Jae-Kwang, Ha, Jung-Hong, Yamamoto, Hitoshi, Cho, Sung-Won, Lee, Sanggyu, Lee, Youngkyun, Park, Kwang-Kyun, Min, Bong-Ki, Park, Chungoo, Kwon, Tae-Yub, Cho, Sung-Jin, and Kim, Jae-Young
Published: 2024
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21. Unravelling the Innermost Jet Structure of OJ 287 with the First GMVA+ALMA Observations

Author: Zhao, Guang-Yao, Gomez, Jose L., Fuentes, Antonio, Krichbaum, Thomas P., Traianou, E., Lico, Rocco, Cho, Ilje, Ros, Eduardo, Komossa, S., Akiyama, Kazunori, Asada, Keiichi, Blackburn, Lindy, Britzen, Silke, Bruni, Gabriele, Crew, Geoffrey, Dahale, Rohan, Dey, Lankeswar, Gold, Roman, Gopakumar, Achamveedu, Issaoun, Sara, Janssen, Michael, Jorstad, Svetlana G., Kim, Jae-Young, Koay, Jun Yi, Kovalev, Yuri Y., Koyama, Shoko, Lobanov, Andrei, Loinard, Laurent, Lu, Rusen, Markoff, Sera, Marscher, Alan P., Marti-Vidal, Ivan, Mizuno, Yosuke, Park, Jongho, Savolainen, Tuomas, and Toscano, Teresa
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We present the first very-long-baseline interferometric (VLBI) observations of the blazar OJ287 carried out jointly with the Global Millimeter VLBI Array (GMVA) and the phased Atacama Large Millimeter/submillimeter Array (ALMA) at 3.5 mm on April 2, 2017. Participation of phased-ALMA not only has improved the GMVA north-south resolution by a factor of ~3, but also has enabled fringe detection with signal-to-noise ratios up to 300 at baselines longer than 2 G{\lambda}. The high sensitivity has motivated us to image the data with the newly developed regularized maximum likelihood imaging methods, revealing the innermost jet structure with unprecedentedly high angular resolution. Our images reveal a compact and twisted jet extending along the northwest direction with two bends within the inner 200 {\mu}as that resembles a precessing jet in projection. The component at the southeastern end shows a compact morphology and high brightness temperature, and is identified as the VLBI core. An extended jet feature that lies at ~200 {\mu}as northwest of the core shows a conical shape in both total and linearly polarized intensity, and a bimodal distribution of the linear polarization electric vector position angle. We discuss the nature of this feature by comparing our observations with models and simulations of oblique and recollimation shocks with various magnetic field configurations. Our high-fidelity images also enabled us to search for possible jet features from the secondary supermassive black hole (SMBH) and test the SMBH binary hypothesis proposed for this source., Comment: 15 pages, 7 figures, accepted for publication in ApJ
Published: 2022
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22. MeqSilhouette v2: Spectrally-resolved polarimetric synthetic data generation for the Event Horizon Telescope

Author: Natarajan, Iniyan, Deane, Roger, Martí-Vidal, Iván, Roelofs, Freek, Janssen, Michael, Wielgus, Maciek, Blackburn, Lindy, Blecher, Tariq, Perkins, Simon, Smirnov, Oleg, Davelaar, Jordy, Moscibrodzka, Monika, Chael, Andrew, Bouman, Katherine L., Kim, Jae-Young, Bernardi, Gianni, van Bemmel, Ilse, Falcke, Heino, Özel, Feryal, and Psaltis, Dimitrios
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: We present MeqSilhouette v2.0 (MeqSv2), a fully polarimetric, time-and frequency-resolved synthetic data generation software for simulating millimetre (mm) wavelength very long baseline interferometry (VLBI) observations with heterogeneous arrays. Synthetic data are a critical component in understanding real observations, testing calibration and imaging algorithms, and predicting performance metrics of existing or proposed sites. MeqSv2 applies physics-based instrumental and atmospheric signal corruptions constrained by empirically-derived site and station parameters to the data. The new version is capable of applying instrumental polarization effects and various other spectrally-resolved effects using the Radio Interferometry Measurement Equation (RIME) formalism and produces synthetic data compatible with calibration pipelines designed to process real data. We demonstrate the various corruption capabilities of MeqSv2 using different arrays, with a focus on the effect of complex bandpass gains on closure quantities for the EHT at 230 GHz. We validate the frequency-dependent polarization leakage implementation by performing polarization self-calibration of synthetic EHT data using PolSolve. We also note the potential applications for cm-wavelength VLBI array analysis and design and future directions., Comment: accepted for publication in MNRAS
Published: 2022
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23. Comparison of three different lactic acid bacteria-fermented proteins on RAW 264.7 osteoclast and MC3T3-E1 osteoblast differentiation

Author: Kim, Jae-Young, Song, Hyun Ji, Cheon, Sejin, An, Seokyoung, Lee, Chul Sang, and Kim, Sae Hun
Published: 2023
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24. Non-fullerene acceptor based photoelectric material for retinal prosthesis

Author: Song, Hyunsun, Roh, Hyeonhee, Kim, Jae Young, Lee, Byung Chul, Walker, Bright, and Im, Maesoon
Published: 2023
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25. Association between familial aggregation of chronic kidney disease and its incidence and progression

Author: Kim, Jae Young, Chun, Sung-youn, Lim, Hyunsun, and Chang, Tae Ik
Published: 2023
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26. Effective dose window for containing tumor burden under tolerable level

Author: Masud, M. A., Kim, Jae-Young, and Kim, Eunjung
Published: 2023
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27. Two-Terminal Lithium-Mediated Artificial Synapses with Enhanced Weight Modulation for Feasible Hardware Neural Networks

Author: Baek, Ji Hyun, Kwak, Kyung Ju, Kim, Seung Ju, Kim, Jaehyun, Kim, Jae Young, Im, In Hyuk, Lee, Sunyoung, Kang, Kisuk, and Jang, Ho Won
Published: 2023
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28. A Psychology of Working Perspective on Women of Color K-12 Educational Leaders' Work Experiences

Author: McGinnis, DorisAnn, primary, Kim, Jae Young, additional, Grooms, Ain, additional, Mahatmya, Duhita, additional, and Johnson, Ebonee, additional
Published: 2023
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29. The intrinsic structure of Sagittarius A* at 1.3 cm and 7 mm

Author: Cho, Ilje, Zhao, Guang-Yao, Kawashima, Tomohisa, Kino, Motoki, Akiyama, Kazunori, Johnson, Michael D., Issaoun, Sara, Moriyama, Kotaro, Cheng, Xiaopeng, Algaba, Juan-Carlos, Jung, Taehyun, Sohn, Bong Won, Krichbaum, Thomas P., Wielgus, Maciek, Hada, Kazuhiro, Lu, Ru-Sen, Cui, Yuzhu, Sawada-Satoh, Satoko, Shen, Zhiqiang, Park, Jongho, Jiang, Wu, Ro, Hyunwook, Yi, Kunwoo, Wajima, Kiyoaki, Lee, Jee Won, Hodgson, Jeffrey, Tazaki, Fumie, Honma, Mareki, Niinuma, Kotaro, Trippe, Sascha, An, Tao, Zhang, Yingkang, Lee, Jeong Ae, Oh, Se-Jin, Byun, Do-Young, Lee, Sang-Sung, Kim, Jae-Young, Oh, Junghwan, Koyama, Shoko, Asada, Keiichi, Wang, Xuezheng, Cui, Lang, Hagiwara, Yoshiaki, Nakamura, Masanori, Takamura, Mieko, Hirota, Tomoya, Sugiyama, Koichiro, Kawaguchi, Noriyuki, Kobayashi, Hideyuki, Oyama, Tomoaki, Yonekura, Yoshinori, Kim, Jongsoo, Hwang, Ju-Yeon, Jung, Dong-Kyu, Kim, Hyo-Ryoung, Kim, Jeong-Sook, Oh, Chung-Sik, Roh, Duk-Gyoo, Yeom, Jae-Hwan, Xia, Bo, Zhong, Weiye, Li, Bin, Zhao, Rongbing, Wang, Jinqing, Liu, Qinghui, and Chen, Zhong
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Sagittarius A* (Sgr A*), the Galactic Center supermassive black hole (SMBH), is one of the best targets to resolve the innermost region of SMBH with very long baseline interferometry (VLBI). In this study, we have carried out observations toward Sgr A* at 1.349 cm (22.223 GHz) and 6.950 mm (43.135 GHz) with the East Asian VLBI Network, as a part of the multi-wavelength campaign of the Event Horizon Telescope (EHT) in 2017 April. To mitigate scattering effects, the physically motivated scattering kernel model from Psaltis et al. (2018) and the scattering parameters from Johnson et al. (2018) have been applied. As a result, a single, symmetric Gaussian model well describes the intrinsic structure of Sgr A* at both wavelengths. From closure amplitudes, the major-axis sizes are ~704$\pm$102 $\mu$as (axial ratio $\sim$1.19$^{+0.24}_{-0.19}$) and $\sim$300$\pm$25 $\mu$as (axial ratio $\sim$1.28$\pm$0.2) at 1.349 cm and 6.95 mm respectively. Together with a quasi-simultaneous observation at 3.5 mm (86 GHz) by Issaoun et al. (2019), we show that the intrinsic size scales with observing wavelength as a power-law, with an index $\sim$1.2$\pm$0.2. Our results also provide estimates of the size and compact flux density at 1.3 mm, which can be incorporated into the analysis of the EHT observations. In terms of the origin of radio emission, we have compared the intrinsic structures with the accretion flow scenario, especially the radiatively inefficient accretion flow based on the Keplerian shell model. With this, we show that a nonthermal electron population is necessary to reproduce the source sizes., Comment: accepted to ApJ
Published: 2021
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30. Magnetic Field Strengths of the Synchrotron Self-Absorption Region in the Jet of CTA 102 During Radio Flares

Author: Kim, Sang-Hyun, Lee, Sang-Sung, Lee, Jee Won, Hodgson, Jeffrey A., Kang, Sincheol, Algaba, Juan-Carlos, Kim, Jae-Young, Hodges, Mark, Agudo, Ivan, Fuentes, Antonio, Escudero, Juan, Myserlis, Ioannis, Traianou, Efthalia, Lähteenmäki, Anne, Tornikoski, Merja, Tammi, Joni, Ramakrishnan, Venkatessh, and Järvelä, Emilia
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: CTA 102 is a blazar implying that its relativistic jet points towards Earth and emits synchrotron radiation produced by energetic particles gyrating in the magnetic field. This study aims to figure out the physical origins of radio flares in the jet, including the connection between the magnetic field and the radio flares. The dataset in the range 2.6-343.5 GHz was collected over a period of 5.5 years (2012 November 20-2018 September 23). During the data collection period, seven flares at 15 GHz with a range of the variability time-scale of roughly 26-171 days were detected. The quasi-simultaneous radio data were used to investigate the synchrotron spectrum of the source. We found that the synchrotron radiation is self-absorbed. The turnover frequency and the peak flux density of the synchrotron self-absorption (SSA) spectra are in the ranges of 42-167 GHz and 0.9-10.2 Jy, respectively. From the SSA spectra, we derived the SSA magnetic field strengths to be 9.20 mG, 12.28 mG, and 50.97 mG on 2013 December 24, 2014 February 28, and 2018 January 13, respectively. We also derived the equipartition magnetic field strengths to be in the range 24-109 mG. The equipartition magnetic field strengths are larger than the SSA magnetic field strengths in most cases, which indicates that particle energy mainly dominates in the jet. Our results suggest that the flares in the jet of CTA 102 originated due to particle acceleration. We propose the possible mechanisms of particle acceleration., Comment: 19 pages, 8 figures, 6 tables, accepted for publication in MNRAS
Published: 2021
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31. Event Horizon Telescope observations of the jet launching and collimation in Centaurus A

Author: Janssen, Michael, Falcke, Heino, Kadler, Matthias, Ros, Eduardo, Wielgus, Maciek, Akiyama, Kazunori, Baloković, Mislav, Blackburn, Lindy, Bouman, Katherine L., Chael, Andrew, Chan, Chi-kwan, Chatterjee, Koushik, Davelaar, Jordy, Edwards, Philip G., Fromm, Christian M., Gómez, José L., Goddi, Ciriaco, Issaoun, Sara, Johnson, Michael D., Kim, Junhan, Koay, Jun Yi, Krichbaum, Thomas P., Liu, Jun, Liuzzo, Elisabetta, Markoff, Sera, Markowitz, Alex, Marrone, Daniel P., Mizuno, Yosuke, Müller, Cornelia, Ni, Chunchong, Pesce, Dominic W., Ramakrishnan, Venkatessh, Roelofs, Freek, Rygl, Kazi L. J., van Bemmel, Ilse, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Baczko, Anne-Kathrin, Ball, David, Barrett, John, Benson, Bradford A., Bintley, Dan, Blundell, Raymond, Boland, Wilfred, 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., Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Chesler, Paul M., Cho, Ilje, Christian, Pierre, Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Doeleman, Sheperd S., Eatough, Ralph P., Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Fraga-Encinas, Raquel, Friberg, Per, Fuentes, Antonio, Galison, Peter, Gammie, Charles F., García, Roberto, Gelles, Zachary, Gentaz, Olivier, Georgiev, Boris, Gold, Roman, Gómez-Ruiz, Arturo I., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Hecht, Michael H., Hesper, Ronald, Himwich, Elizabeth, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Inoue, Makoto, James, David J., Jannuzi, Buell T., Jeter, Britton, Jiang, Wu, Jimenez-Rosales, Alejandra, Jorstad, Svetlana, Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kino, Motoki, Kofuji, Yutaro, Koyama, Shoko, Kramer, Michael, Kramer, Carsten, Kuo, Cheng-Yu, Lauer, Tod R., Lee, Sang-Sung, Levis, Aviad, Li, Yan-Rong, Li, Zhiyuan, Lindqvist, Michael, Lico, Rocco, Lindahl, Greg, Liu, Kuo, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin, Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Marscher, Alan P., Martí-Vidal, Iván, Matsushita, Satoki, Matthews, Lynn D., Medeiros, Lia, Menten, Karl M., Mizuno, Izumi, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Musoke, Gibwa, Mejías, Alejandro Mus, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Neilsen, Joey, Neri, Roberto, Noutsos, Aristeidis, Nowak, Michael A., Okino, Hiroki, Olivares, Héctor, Ortiz-León, Gisela N., Oyama, Tomoaki, Özel, Feryal, Palumbo, Daniel C. M., Park, Jongho, Patel, Nimesh, Pen, Ue-Li, 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, Rogers, Alan, Rose, Mel, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruszczyk, Chet, Sánchez, Salvador, Sánchez-Arguelles, David, Sasada, Mahito, Savolainen, Tuomas, Schloerb, F. Peter, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Torne, Pablo, Trent, Tyler, Traianou, Efthalia, Trippe, Sascha, van Langevelde, Huib Jan, van Rossum, Daniel R., Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wong, George N., Wu, Qingwen, Yoon, Doosoo, Young, André, Young, Ken, Younsi, Ziri, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhao, Guang-Yao, and Zhao, Shan-Shan
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimeter wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to $10-100$ gravitational radii ($r_g=GM/c^2$) scales in nearby sources. Centaurus A is the closest radio-loud source to Earth. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our galactic center. A large southern declination of $-43^{\circ}$ has however prevented VLBI imaging of Centaurus A below ${\lambda}1$cm thus far. Here, we show the millimeter VLBI image of the source, which we obtained with the Event Horizon Telescope at $228$GHz. Compared to previous observations, we image Centaurus A's jet at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly-collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that Centaurus A's source structure resembles the jet in Messier 87 on ${\sim}500r_g$ scales remarkably well. Furthermore, we identify the location of Centaurus A's SMBH with respect to its resolved jet core at ${\lambda}1.3$mm and conclude that the source's event horizon shadow should be visible at THz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses., Comment: 27 pages, 9 figures. This is a post-peer-review, pre-copyedit version of an article published in Nature Astronomy. The final authenticated version is available online at: https://doi.org/10.1038/s41550-021-01417-w
Published: 2021
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32. The Variability of the Black-Hole Image in M87 at the Dynamical Time Scale

Author: Satapathy, Kaushik, Psaltis, Dimitrios, Ozel, Feryal, Medeiros, Lia, Dougall, Sean T., Chan, Chi-kwan, Wielgus, Maciek, Prather, Ben S., Wong, George N., Gammie, Charles F., Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Baczko, Anne-Kathrin, Ball, David R., Baloković, Mislav, Barrett, John, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Boland, Wilfred, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope A., Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Bustamente, Sandra, Byun, Do-Young, Carlstrom, John E., Chael, Andrew, Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Cho, Ilje, Christian, Pierre, Conway, John E., Cordes, James M., Crawford, Thomas, Crew, Geoffrey B., Osorio, Alejandro Cruz, Cui, Yuzhu, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica T., Desvignes, Gregory, Dexter, Jason, Doeleman, Sheperd S., Eatough, Ralph, Falcke, Heino, Farah, Joseph R., Fish, Vincent, Fomalont, Edward B., Ford, H. Alyson, Fraga-Encinas, Raquel, Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, García, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gold, Roman, Gomez-Ruiz, Arturo I., Gómez, Jose L., Gu, Minfeng, Gurwell, Mark A., Hada, Kazuhiro, Haggard, Daryl, Hecht, Michael, Hesper, Ronald, Ho, Luis C., Ho, Paul T., 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, Rosales, Alejandra Jimenez, Johnson, Michael D., Jorstad, Svetlana G., Jung, Taehyun, Karami, Mr. Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Carsten, Kramer, Michael, Krichbaum, Thomas P., Kuo, Cheng-Yu, Lauer, Tod R., Lee, Sang-Sung, Levis, Aviad, Li, Yan-Rong, Li, Zhiyuan, Lindqvist, Michael, Lico, Rocco, Lindahl, Greg, Liu, Jun, Liu, Kuo, Liuzzo, Miss Elisabetta, Lo, Wen-Ping, Lobanov, Andrei, Loinard, Laurent, Lonsdale, Colin J., Lu, Rusen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel, Marscher, Alan P., Marti-Vidal, Ivan, Matsushita, Satoki, Matthews, Lynn, Menten, Karl M., Mizuno, Izumi, Mizuno, Yosuke, Moran, James, Moriyama, Kotaro, Moscibrodzka, Monika, Muller, Cornelia, Mejias, Alejandro M., Musoke, Gibwa, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Okino, Hiroki, Olivares, Hector, Ortiz-Leon, Gisela N., Oyama, Tomoaki, Palumbo, Daniel C., Park, Jongho, Patel, Nimesh A., Pen, Ue-Li, Pesce, Dominic W., Pietu, Vincent, Plambeck, Richard L., PopStefanija, Aleksandar, Porth, Oliver, Potzl, Felix, Preciado-López, Jorge A., Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark, Raymond, Alexander W., Rezzolla, Luciano, Ripperda, Bart, Roelofs, Freek, Rogers, Alan E. E., Ros, Eduardo, Rose, Mel, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruszczyk, Chet, Rygl, Kazi, Sanchez, Salvador, Sanchez-Arguelles, David, Sasada, Mahito, Savolainen, Tuomas, Schloerb, F Peter, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhi-Qiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo, Titus, Michael, Toma, Kenji, Torne, Pablo, Traianou, E., Trent, Tyler, Trippe, Sascha, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Wagner, Jan, Ward-Thompson, Derek, Wardle, John F., Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wiik, Kaj, Wu, Qingwen, Yoon, DooSoo, Young, Andre, Young, Ken H., Younsi, Ziri, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhao, Guang-Yao, and Zhao, Shan-Shan
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The black-hole images obtained with the Event Horizon Telescope (EHT) are expected to be variable at the dynamical timescale near their horizons. For the black hole at the center of the M87 galaxy, this timescale (5-61 days) is comparable to the 6-day extent of the 2017 EHT observations. Closure phases along baseline triangles are robust interferometric observables that are sensitive to the expected structural changes of the images but are free of station-based atmospheric and instrumental errors. We explored the day-to-day variability in closure phase measurements on all six linearly independent non-trivial baseline triangles that can be formed from the 2017 observations. We showed that three triangles exhibit very low day-to-day variability, with a dispersion of $\sim3-5^\circ$. The only triangles that exhibit substantially higher variability ($\sim90-180^\circ$) are the ones with baselines that cross visibility amplitude minima on the $u-v$ plane, as expected from theoretical modeling. We used two sets of General Relativistic magnetohydrodynamic simulations to explore the dependence of the predicted variability on various black-hole and accretion-flow parameters. We found that changing the magnetic field configuration, electron temperature model, or black-hole spin has a marginal effect on the model consistency with the observed level of variability. On the other hand, the most discriminating image characteristic of models is the fractional width of the bright ring of emission. Models that best reproduce the observed small level of variability are characterized by thin ring-like images with structures dominated by gravitational lensing effects and thus least affected by turbulence in the accreting plasmas., Comment: Accepted for Publication in ApJ
Published: 2021
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33. Molybdenum induced defective WO3 multifunctional nanostructure as an electrochromic energy storage device: Novel assembled photovoltaic-electrochromic Mo–WO3 film

Author: Krishna Prasad, Aryal, Kim, Jae-Young, Kang, Soon-Hyung, and Ahn, Kwang-Soon
Published: 2024
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34. A composite electrode of stabilized lithium metal powder and lithiophilic Ag-coated Cu powder for lithium metal batteries

Author: Kim, Jae-young and Lee, Jae-won
Published: 2024
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35. Transcriptomic profiling and the first spatial expression analysis of candidate genes in the salivary gland of the East Asian medicinal leech, Hirudo nipponia

Author: Kim, Jung-Hyeuk, Lee, Chan-Jun, Yu, Yun-Sang, Aryal, Yam Prasad, Kim, Sangil, Suh, Jo-Young, Kim, Jae-Young, Min, Sun Hong, Cha, In-Tae, Lee, Hae-Youn, Shin, Song Yub, and Cho, Sung-Jin
Published: 2024
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36. Secretome analysis reveals reduced expression of COL4A2 in hypoxic cancer-associated fibroblasts with a tumor-promoting function in gastric cancer

Author: Park, Seo-Gyu, Ji, Mi-Jung, Ham, In-Hye, Shin, Yoon-Hee, Lee, Su-Min, Lee, Chang Hoon, Kim, Eunjung, Hur, Hoon, Park, Hyun-Mee, and Kim, Jae-Young
Published: 2023
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37. A persistent double nuclear structure in 3C 84

Author: Oh, Junghwan, Hodgson, Jeffrey A., Trippe, Sascha, Krichbaum, Thomas P., Kam, Minchul, Paraschos, Georgios Filippos, Kim, Jae-Young, Rani, Bindu, Sohn, Bong Won, Lee, Sang-Sung, Lico, Rocco, Liuzzo, Elisabetta, Bremer, Michael, and Zensus, Anton
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: 3C 84 (NGC 1275) is the radio source at the center of the Perseus Cluster and exhibits a bright radio jet. We observed the source with the Global Millimeter VLBI Array (GMVA) between 2008 and 2015, with a typical angular resolution of $\sim$50 $\mu$as. The observations revealed a consistent double nuclear structure separated by $\sim$770 gravitational radii assuming a Black Hole mass of 3.2 $\times 10^{8}$ $M_{\odot}$. The region is likely too broad and bright to be the true jet base anchored in the accretion disk or Black Hole ergosphere. A cone and parabola were fit to the stacked (time averaged) image of the nuclear region. The data did not strongly prefer either fit, but combined with a jet/counter-jet ratio analysis, an upper limit on the viewing angle to the inner jet region of $\leq$35$^{\circ}$ was found. This provides evidence for a variation of the viewing angle along the jet (and therefore a bent jet) within $\sim$0.5 parsec of the jet launching region. In the case of a conical jet, the apex is located $\sim$2400 gravitational radii upstream of the bright nuclear region and up to $\sim$600 gravitational radii upstream in the parabolic case. We found a possible correlation between the brightness temperature and relative position angle of the double nuclear components, which may indicate rotation within the jet.
Published: 2021
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38. Modification of Anaerobic Digestion Model No. 1 for modeling anaerobic digestion of cattle manure with changing solids retention time

Author: Kim, Seunghwan, Lee, Changmin, Lee, Young Su, Kim, Junhyeon, and Kim, Jae Young
Published: 2024
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39. Transition of endochondral bone formation at the normal and botulinum-treated mandibular condyle of growing juvenile rat

Author: Tak, Hye-Jin, Moon, Joo-Won, Kim, Jae-Young, Kang, Sang-Hoon, and Lee, Sang-Hwy
Published: 2024
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40. Optimization of smoothing parameter for block matching and 3D filtering algorithm in low-dose chest and abdominal computed tomography images

Author: Park, Minji, Lim, Sewon, Kim, Hajin, Kim, Jae-Young, and Lee, Youngjin
Published: 2024
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41. Constraints on black-hole charges with the 2017 EHT observations of M87*

Author: Kocherlakota, Prashant, Rezzolla, Luciano, Falcke, Heino, Fromm, Christian M., Kramer, Michael, Mizuno, Yosuke, Nathanail, Antonios, Olivares, Hector, Younsi, Ziri, Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Baczko, Anne-Kathrin, Ball, David, Balokovic, Mislav, Barrett, John, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Boland, Wilfred, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Byun, Do-Young, Carlstrom, John E., 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, Cui, Yuzhu, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Doeleman, Sheperd S., Eatough, Ralph P., Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Fraga-Encinas, Raquel, Friberg, Per, Ford, H. Alyson, Fuentes, Antonio, Galison, Peter, Gammie, Charles F., Garcia, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gold, Roman, Gomez, Jose L., Gomez-Ruiz, Arturo I., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Hecht, Michael H., Hesper, Ronald, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jeter, Britton, Jiang, Wu, Jimenez-Rosales, Alejandra, Johnson, Michael D., Jorstad, Svetlana, Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Carsten, Krichbaum, Thomas P., Kuo, Cheng-Yu, Lauer, Tod R., Lee, Sang-Sung, Levis, Aviad, Li, Yan-Rong, Li, Zhiyuan, Lindqvist, Michael, Lico, Rocco, Lindahl, Greg, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin, Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Marti-Vidal, Ivan, Matsushita, Satoki, Matthews, Lynn D., Medeiros, Lia, Menten, Karl M., Mizuno, Izumi, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Muller, Cornelia, Musoke, Gibwa, Mejias, Alejandro Mus, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Neilsen, Joseph, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Okino, Hiroki, Ortiz-Leon, Gisela N., Oyama, Tomoaki, Ozel, Feryal, Palumbo, Daniel C. M., Park, Jongho, Patel, Nimesh, Pen, Ue-Li, Pesce, Dominic W., Pietu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Potzl, Felix M., Prather, Ben, Preciado-Lopez, Jorge A., Psaltis, Dimitrios, Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., 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., Sanchez, Salvador, Sanchez-Arguelles, David, Sasada, Mahito, Savolainen, Tuomas, Schloerb, F. Peter, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Toma, Kenji, Torne, Pablo, 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, Andre, Young, Ken, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhao, Guang-Yao, Zhao, Shan-Shan, and Collaboration, The EHT
Subjects: General Relativity and Quantum Cosmology
Abstract: Our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by the Event Horizon Telescope (EHT). We use here the M87* shadow size to infer constraints on the physical charges of a large variety of nonrotating or rotating black holes. For example, we show that the quality of the measurements is already sufficient to rule out that M87* is a highly charged dilaton black hole. Similarly, when considering black holes with two physical and independent charges, we are able to exclude considerable regions of the space of parameters for the doubly-charged dilaton and the Sen black holes., Comment: 15 pages, 4 figures, published in PRD on May 19
Published: 2021
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42. The Polarized Image of a Synchrotron Emitting Ring of Gas Orbiting a Black Hole

Author: Narayan, Ramesh, Palumbo, Daniel C. M., Johnson, Michael D., Gelles, Zachary, Himwich, Elizabeth, Chang, Dominic O., Ricarte, Angelo, Dexter, Jason, Gammie, Charles F., Chael, Andrew A., Collaboration, The Event Horizon Telescope, Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Baczko, Anne-Kathrin, Ball, David, Balokovic, Mislav, Barrett, John, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Boland, Wilfred, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Byun, Do-Young, Carlstrom, John E., Chan, Chi-kwan, Chatterjee, Shami, Chatterjee, Koushik, Chen, Ming-Tang, Chen, Yongjun, Chesler, Paul M., Cho, Ilje, Christian, Pierre, Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, Davelaar, Jordy, DeLaurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Doeleman, Sheperd S., Eatough, Ralph P., Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Fraga-Encinas, Raquel, Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, Garcıa, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gold, Roman, Gomez, Jose L., Gomez-Ruiz, Arturo I., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Hecht, Michael H., Hesper, Ronald, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jeter, Britton, Jiang, Wu, Jimenez-Rosales, Alejandra, Jorstad, Svetlana, Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Michael, Kramer, Carsten, Krichbaum, Thomas P., Kuo, Cheng-Yu, Lauer, Tod R., Lee, Sang-Sung, Levis, Aviad, Li, Yan-Rong, Li, Zhiyuan, Lindqvist, Michael, Lico, Rocco, Lindahl, Greg, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Pin, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin, Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Martı-Vidal, Alan P. Marscher Ivan, Matsushita, Satoki, Matthews, Lynn D., Medeiros, Lia, Menten, Karl M., Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Muller, Cornelia, Musoke, Gibwa, Mejıas, Alejandro Mus, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Okino, Hiroki, Olivares, Hector, Ortiz-Leon, Gisela N., Oyama, Tomoaki, Ozel, Feryal, Park, Jongho, Patel, Nimesh, Pen, Ue-Li, Pesce, Dominic W., Pietu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Potzl, Felix M., Prather, Ben, Preciado-Lopez, Jorge A., Psaltis, Dimitrios, Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Rezzolla, Luciano, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Rose, Mel, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruszczyk, Chet, Rygl, Kazi L. J., Sanchez, Salvador, Sanchez-Arguelles, David, Sasada, Mahito, Savolainen, Tuomas, Schloerb, F. Peter, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Toma, Kenji, Torne, Pablo, 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, Andre, Young, Ken, Younsi, Ziri, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhao, Guang-Yao, and Zhao, Shan-Shan
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Synchrotron radiation from hot gas near a black hole results in a polarized image. The image polarization is determined by effects including the orientation of the magnetic field in the emitting region, relativistic motion of the gas, strong gravitational lensing by the black hole, and parallel transport in the curved spacetime. We explore these effects using a simple model of an axisymmetric, equatorial accretion disk around a Schwarzschild black hole. By using an approximate expression for the null geodesics derived by Beloborodov (2002) and conservation of the Walker-Penrose constant, we provide analytic estimates for the image polarization. We test this model using currently favored general relativistic magnetohydrodynamic simulations of M87*, using ring parameters given by the simulations. For a subset of these with modest Faraday effects, we show that the ring model broadly reproduces the polarimetric image morphology. Our model also predicts the polarization evolution for compact flaring regions, such as those observed from Sgr A* with GRAVITY. With suitably chosen parameters, our simple model can reproduce the EVPA pattern and relative polarized intensity in Event Horizon Telescope images of M87*. Under the physically motivated assumption that the magnetic field trails the fluid velocity, this comparison is consistent with the clockwise rotation inferred from total intensity images., Comment: 29 pages, 11 figures, published in ApJ on May 3
Published: 2021
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43. Practical organic electronic noses using semi-permeable polymer membranes

Author: Kim, Jae Young, Haque, Farjana, Lee, Jae Hyun, Park, Yu Jung, Seo, Jung Hwa, Mativenga, Mallory, and Walker, Bright
Published: 2024
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44. Techno-environmental analysis of resource recovery processes from end-of-life PV panels

Author: Chung, Jaeshik, Seo, Bora, Lee, Miyeon, Park, Bogyeong, and Kim, Jae Young
Published: 2024
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45. Effect of orbital volume in unilateral orbital fracture on indirect traumatic optic neuropathy

Author: Senarak, Wirapha, Yongvikul, Atapol, Ku, Jeong-Kui, Kim, Jae-Young, and Huh, Jong-Ki
Published: 2023
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46. Developmental function of Piezo1 in mouse submandibular gland morphogenesis

Author: Pokharel, Elina, Aryal, Yam Prasad, Kim, Tae-Young, Kim, Anna, Kim, Ji-Youn, Yamamoto, Hitoshi, Cho, Sung-Won, Sohn, Wern-Joo, Kim, Jae-Young, and Jung, Jae-Kwang
Published: 2023
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47. In-situ construction of Mo2C–MoC heterostructure on Ni foam for efficient hydrogen evolution in alkaline media

Author: Hwang, Ji Young, Kim, Jae Young, and Youn, Duck Hyun
Published: 2024
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48. Engineering of binder-free cobalt carbonate hydroxide hydrate nanostructure for high-performance hybrid supercapacitors

Author: Rajesh, John Anthuvan, Manikandan, Ramu, Kim, Jae-Young, and Ahn, Kwang-Soon
Published: 2023
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49. Gravitational Test Beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole

Author: Psaltis, Dimitrios, Medeiros, Lia, Christian, Pierre, Ozel, Feryal, Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Asada, Keiichi, Azulay, Rebecca, Ball, David, Balokovic, Mislav, Barrett, John, Bintley, Dan, Blackburn, Lindy, Boland, Wilfred, Bower, Geoffrey C., Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broguiere, Dominique, Bronzwaer, Thomas, Byun, Do-Young, Carlstrom, John E., Chael, Andrew, Chan, Chi-kwan, Chatterjee, Shami, Chatterjee, Koushik, Chen, Ming-Tang, Chen, Yongjun, Cho, Ilje, Conway, John E., Cordes, James M., Crew, Geoffrey B., Cui, Yuzhu, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Eatough, Ralph P., Falcke, Heino, Fish, Vincent L., Fomalont, Ed, Fraga-Encinas, Raquel, Friberg, Per, Fromm, Christian M., Gammie, Charles F., García, Roberto, Gentaz, Olivier, Goddi, Ciriaco, Gomez, Jose L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Hesper, Ronald, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jiang, Wu, Jimenez-Rosales, Alejandra, Johnson, Michael D., Jorstad, Svetlana, Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Jae-Young, Kim, Junhan, Kim, Jongsoo, Kino, Motoki, Koay, Jun Yi, Koch, Patrick M., Koyama, Shoko, Kramer, Michael, Kramer, Carsten, Krichbaum, Thomas P., Kuo, Cheng-Yu, Lauer, Tod R., Lee, Sang-Sung, Li, Yan-Rong, Li, Zhiyuan, Lindqvist, Michael, Lico, Rocco, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Lonsdale, Colin, Lu, Ru-Sen, Mao, Jirong, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Ivan, Matsushita, Satoki, Mizuno, Yosuke, Mizuno, Izumi, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Muller, Cornelia, Musoke, Gibwa, Mejías, Alejandro Mus, Nagai, Hiroshi, Nagar, Neil M., Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Neri, Roberto, Noutsos, Aristeidis, Okino, Hiroki, Olivares, Hector, Oyama, Tomoaki, Palumbo, Daniel C. M., Park, Jongho, Patel, Nimesh, Pen, Ue-Li, Pietu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Prather, Ben, Preciado-Lopez, Jorge A., Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Rose, Mel, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruszczyk, Chet, Ryan, Benjamin R., Rygl, Kazi L. J., Sanchez, Salvador, Sanchez-Arguelles, David, Sasada, Mahito, Savolainen, Tuomas, Schloerb, F. Peter, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Tazaki, Fumie, Tilanus, Remo P. J., Titus, Michael, Torne, Pablo, Trent, Tyler, Traianou, Efthalia, Trippe, Sascha, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Wagner, Jan, Wardle, John, Ward-Thompson, Derek, Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wielgus, Maciek, Wong, George N., Wu, Qingwen, Yoon, Doosoo, Young, Andre, Young, Ken, Younsi, Ziri, Yuan, Feng, Yuan, Ye-Fei, Zhao, Shan-Shan, and Collaboration, the EHT
Subjects: General Relativity and Quantum Cosmology, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The 2017 Event Horizon Telescope (EHT) observations of the central source in M87 have led to the first measurement of the size of a black-hole shadow. This observation offers a new and clean gravitational test of the black-hole metric in the strong-field regime. We show analytically that spacetimes that deviate from the Kerr metric but satisfy weak-field tests can lead to large deviations in the predicted black-hole shadows that are inconsistent with even the current EHT measurements. We use numerical calculations of regular, parametric, non-Kerr metrics to identify the common characteristic among these different parametrizations that control the predicted shadow size. We show that the shadow-size measurements place significant constraints on deviation parameters that control the second post-Newtonian and higher orders of each metric and are, therefore, inaccessible to weak-field tests. The new constraints are complementary to those imposed by observations of gravitational waves from stellar-mass sources., Comment: Physical Review Letters
Published: 2020
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50. Interferometric Monitoring of Gamma-ray Bright AGNs: OJ 287

Author: Lee, Jee Won, Lee, Sang-Sung, Algaba, Juan-Carlos, Hodgson, Jeffrey, Kim, Jae-Young, Park, Jongho, Kino, Motoki, Kim, Dae-Won, Kang, Sincheol, Yoo, Sungmin, Kim, Sang Hyun, and Gurwell, Mark
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the results of simultaneous multi-frequency imaging observations at 22, 43, 86, and 129\,GHz of OJ\,287. We used the Korean VLBI Network as part of the Interferometric MOnitoring of GAmma-ray Bright active galactic nuclei (iMOGABA). The iMOGABA observations were performed during 31 epochs from 2013 January 16 to 2016 December 28. We also used 15\,GHz OVRO and 225\,GHz SMA flux density data. We analyzed four flux enhancements in the light curves. The estimated time scales of three flux enhancements were similar with time scales of $\sim$50 days at two frequencies. A fourth flux enhancement had a variability timescale approximately twice as long. We found that 225\,GHz enhancements led the 15\,GHz enhancements by a range of 7 to 30 days in the time delay analysis. We found the fractional variability did not change with frequency between 43 and 86\,GHz. We could reliably measure the turnover frequency, $\nu_{\rm c}$, of the core of the source in three epochs. This was measured to be in a range from 27 to 50\,GHz and a flux density at the turnover frequency, $S_{\rm m}$, ranging from 3-6\,Jy. The derived SSA magnetic fields, $B_{\rm SSA}$, are in a range from $0.157\pm0.104$ to $0.255\pm0.146$ mG. We estimated the equipartition magnetic field strengths to be in a range from $0.95\pm0.15$ to $1.93\pm0.30$ mG. The equipartition magnetic field strengths are up to a factor of 10 higher than the values of $B_{\rm SSA}$. We conclude that the downstream jet may be more particle energy dominated., Comment: 27 pages, 9 figures, Accepted for publication in ApJ
Published: 2020
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