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Challenges in Understanding Black Hole Powered Jets with VLBI

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A special issue of Galaxies (ISSN 2075-4434).

Deadline for manuscript submissions: closed (25 December 2022) | Viewed by 23890

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Special Issue Editors

Dr. Motoki Kino

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Guest Editor

Academic Support Center, Kogakuin University of Technology and Engineering, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan
Interests: black hole astrophysics; active galactic nuclei; high energy astrophysics; radio astronomy with Very Long Baseline Interferometry; relativistic jets

Dr. Yosuke Mizuno

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Guest Editor

School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
Interests: accretion and outflow in relativistic compact objects; magnetic activity in relativistic plasma; theory of gravity

Dr. Taehyun Jung

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Guest Editor

Korea Astronomy and Space Science Institute, Daedoku-daero 776, Daejeon 34055, Korea
Interests: radio astronomy with Very Long Baseline Interferometry; VLBI astrometry; active galactic nuclei

Special Issue Information

Dear Colleagues,

The Event Horizon Telescope (EHT) has made a breakthrough in capturing the black hole shadow at the base of the M87 jet for the first time. This discovery has given momentum to explore the formation and acceleration mechanism of jets powered by black holes, one of the biggest mysteries in astrophysics. Riding on this momentum, synergy with worldwide VLBI observation (such as GMVA, EAVN, VLBA, EVN, LBA etc.) is now being vigorously pursued as the key to elucidating the “jet formation and acceleration mechanism”.

We are now at a time of rapid progress in instrumental development, observation, and theoretical research, all of which are strongly influencing each other. A variety of unique and budding challenges are being taken up by each.

Therefore, in this Special Issue, we shall collect reviews and papers on research and development based on these various challenges and new perspectives to provide inspiration for the next steps to uncover the jet formation and acceleration mechanism. Since this Special Issue partly aims for an update on the whitepaper published in 2017 by East Asian VLBI Network (EAVN) user community actively observing M87 and Sagittarius A* as major objects together with the EHT collaboration, the content includes several topics on instrument development related to EAVN.

References :

“White Paper on East Asian Vision for mm/submm VLBI: Toward Black Hole Astrophysics down to Angular Resolution of 1 Rs” K. Asada, M. Kino, M. Honma et al. (2017)

https://arxiv.org/abs/1705.04776

Dr. Motoki Kino
Dr. Yosuke Mizuno
Dr. Taehyun Jung
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Galaxies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

black hole
active galactic nuclei
Very Long Baseline Interferometry (VLBI)
relativistic jets

Published Papers (11 papers)

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Research

Jump to: Review

15 pages, 5043 KiB

Open AccessArticle

Monitoring the Size and Flux Density of Sgr A* during the Active State in 2019 with East Asian VLBI Network

by Xiaopeng Cheng, Ilje Cho, Tomohisa Kawashima, Motoki Kino, Guang-Yao Zhao, Juan-Carlos Algaba, Yutaro Kofuji, Sang-Sung Lee, Jee-Won Lee, Whee Yeon Cheong, Wu Jiang and Junghwan Oh

Galaxies 2023, 11(2), 46; https://0-doi-org.brum.beds.ac.uk/10.3390/galaxies11020046 - 20 Mar 2023

Cited by 3 | Viewed by 1680

Abstract

In this work, we studied the Galactic Center supermassive black hole (SMBH), Sagittarius A* (Sgr A

^{*}

), with the KVN and VERA Array (KaVA)/East Asian VLBI Network (EAVN) monitoring observations. Especially in 13 May 2019, Sgr A

^{*}

experienced an unprecedented bright [...] Read more.

In this work, we studied the Galactic Center supermassive black hole (SMBH), Sagittarius A* (Sgr A

^{*}

), with the KVN and VERA Array (KaVA)/East Asian VLBI Network (EAVN) monitoring observations. Especially in 13 May 2019, Sgr A

^{*}

experienced an unprecedented bright near infra-red (NIR) flare; so, we find a possible counterpart at 43 GHz (7 mm). As a result, a large temporal variation of the flux density at the level ∼15.4%, with the highest flux density of 2.04 Jy, is found on 11 May 2019. Interestingly, the intrinsic sizes are also variable, and the area and major-axis size show marginal correlation with flux density with ≳2

σ

. Thus, we interpret that the emission region at 43 GHz follows the larger-when-brighter relation in 2019. The possible origins are discussed with an emergence of a weak jet/outflow component and the position angle change of the rotation axis of the accretion disk in time. Full article

(This article belongs to the Special Issue Challenges in Understanding Black Hole Powered Jets with VLBI)

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9 pages, 788 KiB

Open AccessArticle

Super-Resolved Image of M87 Observed with East Asian VLBI Network

by Fumie Tazaki, Yuzhu Cui, Kazuhiro Hada, Motoki Kino, Ilje Cho, Guang-Yao Zhao, Kazunori Akiyama, Yosuke Mizuno, Hyunwook Ro, Mareki Honma, Ru-Sen Lu, Zhi-Qiang Shen, Lang Cui and Yoshinori Yonekura

Galaxies 2023, 11(2), 39; https://0-doi-org.brum.beds.ac.uk/10.3390/galaxies11020039 - 28 Feb 2023

Viewed by 1250

Abstract

Obtaining high-resolution images at centimeter-or-longer wavelengths is vital for understanding the physics of jets. We reconstructed images from the M87 22 GHz data observed with the East Asian VLBI Network (EAVN) by using the regularized maximum likelihood (RML) method, which is different from the conventional imaging method CLEAN. Consequently, a bright core and jet extending about 30 mas to the northwest were detected with a higher resolution than in the CLEAN image. The width of the jet was 0.5 mas at 0.3 mas from the core, consistent with the width measured in the 86 GHz image in the previous study. In addition, three ridges were able to be detected at around 8 mas from the core, even though the peak-to-peak separation was only 1.0 mas. This indicates that the RML image’s spatial resolution is at least 30% higher than that of the CLEAN image. This study is an important step for future multi-frequency and high-cadence observations of the EAVN to discuss the more detailed structure of the jet and its time variability. Full article

(This article belongs to the Special Issue Challenges in Understanding Black Hole Powered Jets with VLBI)

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13 pages, 7877 KiB

Open AccessArticle

Transverse Oscillations of the M87 Jet Revealed by KaVA Observations

by Hyunwook Ro, Kunwoo Yi, Yuzhu Cui, Motoki Kino, Kazuhiro Hada, Tomohisa Kawashima, Yosuke Mizuno, Bong Won Sohn and Fumie Tazaki

Galaxies 2023, 11(1), 33; https://0-doi-org.brum.beds.ac.uk/10.3390/galaxies11010033 - 15 Feb 2023

Cited by 3 | Viewed by 1130

Abstract

Recent VLBI monitoring has found transverse motions of the M87 jet. However, due to the limited cadence of previous observations, details of the transverse motion have not been fully revealed yet. We have regularly monitored the M87 jet at KVN and VERA Array (KaVA) 22 GHz from December 2013 to June 2016. The average time interval of the observation is ∼0.1 year, which is suitable for tracking short-term structural changes. From these observations, the M87 jet is well represented by double ridge lines in the region 2–12 mas from the core. We found that the ridge lines exhibit transverse oscillations in all observed regions with an average period of

0.94 \pm 0.12

years. When the sinusoidal fit is performed, we found that the amplitude of this oscillation is an order of ∼0.1 mas, and the oscillations in the northern and southern limbs are almost in phase. Considering the amplitude, it does not originate from Earth’s parallax. We propose possible scenarios of the transverse oscillation, such as the propagation of jet instabilities or magneto-hydrodynamic (MHD) waves or perturbed mass injection around magnetically dominated accretion flows. Full article

(This article belongs to the Special Issue Challenges in Understanding Black Hole Powered Jets with VLBI)

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16 pages, 3421 KiB

Open AccessArticle

HINOTORI and Its Perspectives in the Black-Hole Jet Study

by Toshihisa Tsutsumi, Kotaro Niinuma, Hiroshi Imai, Ryoko Amari, Yusuke Shimizu, Hideo Ogawa, Atsushi Nishimura, Chieko Miyazawa, Tomoaki Oyama, Hiroyuki Kaneko, Keisuke Nakashima, Satoko Sawada-Satoh and Takahiro Aoki

Galaxies 2023, 11(1), 30; https://0-doi-org.brum.beds.ac.uk/10.3390/galaxies11010030 - 13 Feb 2023

Cited by 1 | Viewed by 1203

Abstract

Simultaneous multi-band very long baseline interferometry (VLBI) observations at millimeter wavelengths have huge potential for various science cases. However, there exist difficulties in expanding the scientific targets, as the sensitivity of radio telescopes at millimeter wavelengths is typically lower compared to that at centimeter wavelengths. In order to realize high-sensitivity mm-VLBI observations in the East Asia region, we are promoting the HINOTORI (Hybrid Installation project in NObeyama, Triple-band ORIented) project, which aims to launch the wide-band and simultaneous triple-band (22/43/86 GHz) VLBI system with the Nobeyama 45 m Radio Telescope (NRO45). The simultaneous 22/43 GHz observation mode has already been operated for the open-use program. We have recently completed the performance evaluation of the receiver and observing system at 86 GHz. In addition, a new wide-band VLBI back-end system has been installed on the NRO45 and the performance of this receiving system has been found to be sufficient to meet scientific requirements. Currently, we are performing commissioning observations to establish regular VLBI operation with simultaneous triple-band mode together with the Korean VLBI Network. The participation of the NRO45 is expected to strengthen the mm-VLBI observation network in the East Asia region and to be a very powerful addition with respect to the science of of black hole jets. Full article

(This article belongs to the Special Issue Challenges in Understanding Black Hole Powered Jets with VLBI)

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14 pages, 2414 KiB

Open AccessArticle

Demonstration of Ultrawideband Polarimetry Using VLBI Exploration of Radio Astrometry (VERA)

by Yoshiaki Hagiwara, Kazuhiro Hada, Mieko Takamura, Tomoaki Oyama, Aya Yamauchi and Syunsaku Suzuki

Galaxies 2022, 10(6), 114; https://0-doi-org.brum.beds.ac.uk/10.3390/galaxies10060114 - 08 Dec 2022

Cited by 4 | Viewed by 1248

Abstract

We report on recent technical developments in the front- and back-ends for the four 20 m radio telescopes of the Japanese Very-Long-Baseline Interferometry (VLBI) project, VLBI Exploration of Radio Astrometry (VERA). We present a brief overview of a dual-circular polarization receiving and ultrawideband [...] Read more.

^{- 1}

) recording systems that were installed on each of the four telescopes operating at 22 and 43 GHz bands. The wider-band capability improves the sensitivity of VLBI observations for continuum emission, and the dual-polarization capability enables the study of magnetic fields in relativistic jets ejected from supermassive black holes in active galactic nuclei and in sites of star formation and around evolved stars.We present the linear polarization intensity maps of extragalactic sources at 22 and 43 GHz obtained from the most recent test observations to show the state of the art of the VERA polarimetric observations. At the end of this article, given the realization of VLBI polarimetry with VERA, we describe the future prospects for scientific aims and further technical developments. Full article

(This article belongs to the Special Issue Challenges in Understanding Black Hole Powered Jets with VLBI)

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11 pages, 2709 KiB

Open AccessArticle

Diverse Polarimetric Features of AGN Jets from Various Viewing Angles: Towards a Unified View

by Yuh Tsunetoe, Shin Mineshige, Tomohisa Kawashima, Ken Ohsuga, Kazunori Akiyama and Hiroyuki R. Takahashi

Galaxies 2022, 10(5), 103; https://0-doi-org.brum.beds.ac.uk/10.3390/galaxies10050103 - 21 Oct 2022

Cited by 1 | Viewed by 1534

Abstract

Here, we demonstrate that polarization properties show a wide diversity depending on viewing angles. To simulate images of a supermassive black hole and surrounding plasma, we performed a full-polarimetric general relativistic radiative transfer based on three-dimensional general relativistic magnetohydrodynamics models with moderate magnetic strengths. Under an assumption of a hot-jet and cold-disk in the electron temperature prescription, we confirmed a typical scenario where polarized synchrotron emissions from the funnel jet experience Faraday rotation and conversion in the equatorial disk. Further, we found that linear polarization vectors are inevitably depolarized for edge-on-like observers, whereas a portion of vectors survive and reach the observers in face-on-like cases. We also found that circular polarization components have persistent signs in the face-on cases, and changing signs in the edge-on cases. It is confirmed that these features are smoothly connected via intermediate viewing-angle cases. These results are due to Faraday rotation/conversion for different viewing angles, and suggest that a combination of linear and circular polarimetry can give a constraint on the inclination between the observer and black hole’s (and/or disk’s) rotating-axis and plasma properties in the jet–disk structure. These can also lead to a more statistical and unified interpretation for a diversity of emissions from active galactic nuclei. Full article

(This article belongs to the Special Issue Challenges in Understanding Black Hole Powered Jets with VLBI)

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10 pages, 533 KiB

Open AccessArticle

Particle Motion and Plasma Effects on Gravitational Weak Lensing in Lorentzian Wormhole Spacetime

by Farruh Atamurotov, Sanjar Shaymatov and Bobomurat Ahmedov

Galaxies 2021, 9(3), 54; https://0-doi-org.brum.beds.ac.uk/10.3390/galaxies9030054 - 03 Aug 2021

Cited by 22 | Viewed by 2581

Abstract

Here we study particle motion in the specific Lorentzian wormhole spacetime characterized, in addition to the total mass M, with the dimensionless parameter

λ

. In particular we calculate the radius of the innermost stable circular orbit (ISCO) for test particles and [...] Read more.

Here we study particle motion in the specific Lorentzian wormhole spacetime characterized, in addition to the total mass M, with the dimensionless parameter

λ

. In particular we calculate the radius of the innermost stable circular orbit (ISCO) for test particles and the photonsphere for massless particles. We show that the effect of the dimensionless wormhole parameter decreases the ISCO radius and the radius of the photon orbit. Then, we study plasma effects on gravitational weak lensing in wormhole spacetime and obtain the deflection angle of the light. We show that the effect of

λ

decreases the deflection angle. We study the effects of uniform and non-uniform plasma on the light deflection angle separately, and show that the uniform plasma causes the deflection angle to be smaller in contrast to the non-uniform plasma. Full article

(This article belongs to the Special Issue Challenges in Understanding Black Hole Powered Jets with VLBI)

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Review

Jump to: Research

15 pages, 2742 KiB

Open AccessReview

The Past and Future of East Asia to Italy: Nearly Global VLBI

by Gabriele Giovannini, Yuzhu Cui, Kazuhiro Hada, Kunwoo Yi, Hyunwook Ro, Bong Won Sohn, Mieko Takamura, Salvatore Buttaccio, Filippo D’Ammando, Marcello Giroletti, Yoshiaki Hagiwara, Motoki Kino, Evgeniya Kravchenko, Giuseppe Maccaferri, Alexey Melnikov, Kotaro Niinuma, Monica Orienti, Kiyoaki Wajima, Kazunori Akiyama, Akihiro Doi, Do-Young Byun, Tomoya Hirota, Mareki Honma, Taehyun Jung, Hideyuki Kobayashi, Shoko Koyama, Andrea Melis, Carlo Migoni, Yasuhiro Murata, Hiroshi Nagai, Satoko Sawada-Satoh and Matteo Stagni Show full author list Hide full author list

Galaxies 2023, 11(2), 49; https://0-doi-org.brum.beds.ac.uk/10.3390/galaxies11020049 - 22 Mar 2023

Cited by 2 | Viewed by 1952

Abstract

We present here the East Asia to Italy Nearly Global VLBI (EATING VLBI) project. How this project started and the evolution of the international collaboration between Korean, Japanese, and Italian researchers to study compact sources with VLBI observations is reported. Problems related to the synchronization of the very different arrays and technical details of the telescopes involved are presented and discussed. The relatively high observation frequency (22 and 43 GHz) and the long baselines between Italy and East Asia produced high-resolution images. We present example images to demonstrate the typical performance of the EATING VLBI array. The results attracted international researchers and the collaboration is growing, now including Chinese and Russian stations. New in progress projects are discussed and future possibilities with a larger number of telescopes and a better frequency coverage are briefly discussed herein. Full article

(This article belongs to the Special Issue Challenges in Understanding Black Hole Powered Jets with VLBI)

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25 pages, 66913 KiB

Open AccessReview

Overview of the Observing System and Initial Scientific Accomplishments of the East Asian VLBI Network (EAVN)

by Kazunori Akiyama, Juan-Carlos Algaba, Tao An, Keiichi Asada, Kitiyanee Asanok, Do-Young Byun, Thanapol Chanapote, Wen Chen, Zhong Chen, Xiaopeng Cheng, James O. Chibueze, Ilje Cho, Se-Hyung Cho, Hyun-Soo Chung, Lang Cui, Yuzhu Cui, Akihiro Doi, Jian Dong, Kenta Fujisawa, Wei Gou, Wen Guo, Kazuhiro Hada, Yoshiaki Hagiwara, Tomoya Hirota, Jeffrey A. Hodgson, Mareki Honma, Hiroshi Imai, Phrudth Jaroenjittichai, Wu Jiang, Yongbin Jiang, Yongchen Jiang, Takaaki Jike, Dong-Kyu Jung, Taehyun Jung, Noriyuki Kawaguchi, Dong-Jin Kim, Hyo-Ryoung Kim, Jaeheon Kim, Jeong-Sook Kim, Kee-Tae Kim, Soon-Wook Kim, Motoki Kino, Hideyuki Kobayashi, Shoko Koyama, Busaba H. Kramer, Jee-Won Lee, Jeong Ae Lee, Sang-Sung Lee, Sang Won Lee, Bin Li, Guanghui Li, Xiaofei Li, Zhixuan Li, Qinghui Liu, Xiang Liu, Ru-Sen Lu, Kazuhito Motogi, Masanori Nakamura, Kotaro Niinuma, Chungsik Oh, Hongjong Oh, Junghwan Oh, Se-Jin Oh, Tomoaki Oyama, Jongho Park, Saran Poshyachinda, Hyunwook Ro, Duk-Gyoo Roh, Wiphu Rujopakarn, Nobuyuki Sakai, Satoko Sawada-Satoh, Zhi-Qiang Shen, Katsunori M. Shibata, Bong Won Sohn, Boonrucksar Soonthornthum, Koichiro Sugiyama, Yunxia Sun, Mieko Takamura, Yoshihiro Tanabe, Fumie Tazaki, Sascha Trippe, Kiyoaki Wajima, Jinqing Wang, Na Wang, Shiqiang Wang, Xuezheng Wang, Bo Xia, Shuangjing Xu, Hao Yan, Wenjun Yang, Jae-Hwan Yeom, Kunwoo Yi, Sang-Oh Yi, Yoshinori Yonekura, Hasu Yoon, Linfeng Yu, Jianping Yuan, Youngjoo Yun, Bo Zhang, Hua Zhang, Yingkang Zhang, Guang-Yao Zhao, Rongbing Zhao, Weiye Zhong and on behalf of the East Asian VLBI Network Collaboration Show full author list Hide full author list

Galaxies 2022, 10(6), 113; https://0-doi-org.brum.beds.ac.uk/10.3390/galaxies10060113 - 07 Dec 2022

Cited by 5 | Viewed by 4649

Abstract

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 Southeast Asian and European countries. EAVN currently consists of 16 radio telescopes and three correlators located in China, Japan, and Korea, and is operated mainly at three frequency bands, 6.7, 22, and 43 GHz with the longest baseline length of 5078 km, resulting in the highest angular resolution of 0.28 milliarcseconds at 43 GHz. One of distinct capabilities of EAVN is multi-frequency simultaneous data reception at nine telescopes, which enable us to employ the frequency phase transfer technique to obtain better sensitivity at higher observing frequencies. EAVN started its open-use program in the second half of 2018, providing a total observing time of more than 1100 h in a year. EAVN fills geographical gap in global VLBI array, resulting in enabling us to conduct contiguous high-resolution VLBI observations. EAVN has produced various scientific accomplishments especially in observations toward active galactic nuclei, evolved stars, and star-forming regions. These activities motivate us to initiate launch of the ’Global VLBI Alliance’ to provide an opportunity of VLBI observation with the longest baselines on the earth. Full article

(This article belongs to the Special Issue Challenges in Understanding Black Hole Powered Jets with VLBI)

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21 pages, 1100 KiB

Open AccessReview

Modeling Nearby Low-Luminosity Active-Galactic-Nucleus Jet Images at All VLBI Scales

by Hung-Yi Pu, Keiichi Asada and Masanori Nakamura

Galaxies 2022, 10(6), 104; https://0-doi-org.brum.beds.ac.uk/10.3390/galaxies10060104 - 25 Oct 2022

Viewed by 1561

Abstract

Relativistic jets from nearby low-luminosity active-galactic-nuclei (LLAGN) were observed by Very-Long Baseline Interferometry (VLBI) across many orders of magnitude in space, from milliparsec to sub-parsec scales, and from the jet base in the vicinity of black holes to the jet collimation and acceleration regions. With the improved resolution for VLBI observations, resolved VLBI jet morphologies provide valuable opportunities for testing and constraining black hole jet physics. In this review, we summarize and discuss the current progress of modeling nearby LLAGN jet images from horizon scales to large scales, including the construction of jet models and the assumed emission details. Illustrative examples for jet image modeling are also given to demonstrate how jet image features may vary with the underlying physics. Full article

(This article belongs to the Special Issue Challenges in Understanding Black Hole Powered Jets with VLBI)

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23 pages, 6794 KiB

Open AccessReview

Polarization Observations of AGN Jets: Past and Future

by Jongho Park and Juan Carlos Algaba

Galaxies 2022, 10(5), 102; https://0-doi-org.brum.beds.ac.uk/10.3390/galaxies10050102 - 20 Oct 2022

Cited by 6 | Viewed by 2440

Abstract

The magnetic field is believed to play a critical role in the bulk acceleration and propagation of jets produced in active galactic nuclei (AGN). Polarization observations of AGN jets provide valuable information about their magnetic fields. As a result of radiative transfer, jet structure, and stratification, among other factors, it is not always straightforward to determine the magnetic field structures from observed polarization. We review these effects and their impact on polarization emission at a variety of wavelengths, including radio, optical, and ultraviolet wavelengths in this paper. It is also possible to study the magnetic field in the launching and acceleration regions of AGN jets by using very long baseline interferometry (VLBI), which occurs on a small physical scale. Due to the weak polarization of the jets in these regions, probing the magnetic field is generally difficult. However, recent VLBI observations have detected significant polarization and Faraday rotation in some nearby sources. We present the results of these observations as well as prospects for future observations. Additionally, we briefly discuss recently developed polarization calibration and imaging techniques for VLBI data, which enable more in-depth analysis of the magnetic field structure around supermassive black holes and in AGN jets. Full article

(This article belongs to the Special Issue Challenges in Understanding Black Hole Powered Jets with VLBI)

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