135 citations · 1.3k across the 68 of their papers we have counts for
74 papers
The 2015-2017 Large EVPA Rotation in OJ 287: Dominant Propagating Component in a Helical Magnetic Field with Time-Dependent Viewing Geometry
Wanchaloem Khwammai, Minchul Kam, Motoki Kino +11
We present high-cadence, multi-frequency monitoring of the blazar OJ 287 using KVN (22--129 GHz), ALMA (91.5--343.5 GHz), and Metsähovi (37 GHz), covering 2012--2023, together with…
Cosmological Distance Measurements of High Redshift Blazars: OJ 248 (z=0.939) and 4C +38.41 (z=1.814)
Young-Bin Shin, Sang-Sung Lee, Sincheol Kang +3
In this study, we estimated the angular diameter distances to two high-redshift active galactic nuclei (AGNs), OJ 248 (z = 0.939) and 4C +38.41 (z = 1.814), using 43 GHz radio ligh…
A refined method for measuring cosmological distances using variability and proper motions in AGN with VLBI-detected counter-jets
Jeffrey A. Hodgson, Anthony Carr, David Parkinson +6
In a previous paper, we described a `standard speed-gun' (SSG) distance that uses the speed of light to standardize a ruler under the assumption that the radio variability seen in…
SKAVLBI view of AGN jets in the early Universe
C. Spingola, M. Mezcua, Y. Liu +33
Active Galactic Nuclei (AGN) are among the brightest sources in the Universe, and those that are also jetted are uniquely valuable at the earliest epochs, because their relativisti…
A Unified Origin of Faraday Rotation toward 3C 84: The Circumnuclear Ambient Medium within the Parsec-Scale Bondi Radius of the Host Galaxy NGC 1275
Minchul Kam, Jongho Park, Sascha Trippe +11
We present multi-frequency polarimetric observations of 3C 84 obtained with the Korean VLBI Network at 43-141 GHz, the Very Long Baseline Array at 43 GHz, and the High Sensitivity…
The variability angular diameter distance and the intrinsic brightness temperature of active galactic nuclei
Whee Yeon Cheong, Sang-Sung Lee, Chanwoo Song +5
Context. It has recently been suggested that angular diameter distances derived from comparing the variability timescales of blazars to angular size measurements with very long bas…
Discovery of Limb Brightening in the Parsec-scale Jet of NGC 315 through Global Very Long Baseline Interferometry Observations and Its Implications for Jet Models
Jongho Park, Guang-Yao Zhao, Masanori Nakamura +19
We report the first observation of the nearby giant radio galaxy NGC 315 using a global VLBI array consisting of 22 radio antennas located across five continents, including high-se…
Evidence for a toroidal magnetic field in the core of 3C 84
G. F. Paraschos, L. C. Debbrecht, J. A. Kramer +13
The spatial scales of relativistic radio jets, probed by relativistic magneto-hydrodynamic jet launching simulations (RMHDs) and by most very-long-baseline interferometry (VLBI) ob…
A study of the radio spectrum of Mrk 421
Jee Won Lee, Sang-Sung Lee, Jeffrey Hodgson +5
We present the results of a spectral analysis using simultaneous multifrequency (22, 43, 86, and 129 GHz) very long baseline interferometry (VLBI) observations of the Korean VLBI N…
Observational Evidence to Support a Dense Ambient Medium Shaping the Jet in 3C 84
Jongho Park, Motoki Kino, Hiroshi Nagai +4
Highly collimated relativistic jets are a defining feature of certain active galactic nuclei (AGN), yet their formation mechanism remains elusive. Previous observations and theoret…
Lost in the curve: Investigating the disappearing knots in the blazar 3C 454.3
Efthalia Traianou, Thomas P. Krichbaum, José L. Gómez +21
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 interfero…
Evolution of the Termination Region of the Parsec-Scale Jet of 3C 84 Over the Past 20 Years
Minchul Kam, Jeffrey A. Hodgson, Jongho Park +4
We present the kinematics of the parsec-scale jet in 3C 84 from 2003 November to 2022 June observed with the Very Long Baseline Array (VLBA) at 43 GHz. We find that the C3 componen…
Precessing jet nozzle connecting to a spinning black hole in M87
Yuzhu Cui, Kazuhiro Hada, Tomohisa Kawashima +76
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…
Exploring connections between the VLBI and optical morphology of AGNs and their host galaxies
David Fernández Gil, Jeffrey A. Hodgson, Benjamin L'Huillier
We analyse VLBI and optical images of AGNs and their host galaxies and look for statistical correlations between the shape and orientation of the galaxy and the direction of the je…
The Capella Program: Toward A Space-only High-frequency Radio VLBI Network Formed by Small Satellites in Low Earth Orbits
Sascha Trippe, Taehyun Jung, Jung-Won Lee +11
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…
Spectral analysis of a parsec-scale jet in M87: Observational constraint on the magnetic field strengths in the jet
Hyunwook Ro, Motoki Kino, Bong Won Sohn +49
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, magne…
Estimating the feasibility of `standard speed-gun' distances
Jeffrey A. Hodgson, Benjamin L'Huillier, Ioannis Liodakis +2
In a previous paper, we demonstrated a single-rung method for measuring cosmological distances in active galactic nuclei (AGN) that can be used from low redshift (z < 0.1) to high…
Overview of the Observing System and Initial Scientific Accomplishments of the East Asian VLBI Network (EAVN)
Kazunori Akiyama, Juan-Carlos Algaba, Tao An +101
The East Asian VLBI Network (EAVN) is an international VLBI facility in East Asia and is operated under mutual collaboration between East Asian countries, as well as part of Southe…
Jet kinematics in the transversely stratified jet of 3C 84 A two-decade overview
G. F. Paraschos, T. P. Krichbaum, J. -Y. Kim +11
3C84 (NGC1275) is one of the brightest radio sources in the mm radio-bands, which led to a plethora of VLBI observations at numerous frequencies over the years. They reveal a two-s…
The intrinsic structure of Sagittarius A* at 1.3 cm and 7 mm
Ilje Cho, Guang-Yao Zhao, Tomohisa Kawashima +63
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 interferomet…
Magnetic Field Strengths of the Synchrotron Self-Absorption Region in the Jet of CTA 102 During Radio Flares
Sang-Hyun Kim, Sang-Sung Lee, Jee Won Lee +15
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 stu…
A persistent double nuclear structure in 3C 84
Junghwan Oh, Jeffrey A. Hodgson, Sascha Trippe +11
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) betwe…
Pinpointing the jet apex in 3C 84
G. F. Paraschos, J. -Y. Kim, T. P. Krichbaum +4
Jets which are powered by an AGN are a crucial element in the study of their central black holes (BH) and their immediate surroundings. The formation of such jets is the subject of…
Interferometric Monitoring of Gamma-ray Bright AGNs: Measuring the Magnetic Field Strength of 4C +29.45
S. Kang, S. -S. Lee, J. Hodgson +7
We present the results of multi-epoch, multi-frequency monitoring of a blazar 4C +29.45, which was regularly monitored as part of the Interferometric Monitoring of GAmma-ray Bright…