Spectral analysis of a parsec-scale jet in M 87: Observational constraint on the magnetic field strengths in the jet

Hyunwook Ro; Motoki Kino; Bong Won Sohn; Kazuhiro Hada; Jongho Park; Masanori Nakamura; Yuzhu Cui; Kunwoo Yi; Aeree Chung; Jeffrey Hodgson; Tomohisa Kawashima; Tao An; Sascha Trippe; Juan Carlos Algaba; Jae Young Kim; Satoko Sawada-Satoh; Kiyoaki Wajima; Zhiqiang Shen; Xiaopeng Cheng; Ilje Cho; Wu Jiang; Taehyun Jung; Jee Won Lee; Kotaro Niinuma; Junghwan Oh; Fumie Tazaki; Guang Yao Zhao; Kazunori Akiyama; Mareki Honma; Jeong Ae Lee; Rusen Lu; Yingkang Zhang; Keiichi Asada; Lang Cui; Yoshiaki Hagiwara; Tomoya Hirota; Noriyuki Kawaguchi; Shoko Koyama; Sang Sung Lee; Se Jin Oh; Koichiro Sugiyama; Mieko Takamura; Xuezheng Wang; Ju Yeon Hwang; Dong Kyu Jung; Hyo Ryoung Kim; Jeong Sook Kim; Hideyuki Kobayashi; Chung Sik Oh; Tomoaki Oyama; Duk Gyoo Roh; Jae Hwan Yeom

doi:10.1051/0004-6361/202142988

Spectral analysis of a parsec-scale jet in M 87: Observational constraint on the magnetic field strengths in the jet

Hyunwook Ro, Motoki Kino, Bong Won Sohn, Kazuhiro Hada, Jongho Park, Masanori Nakamura, Yuzhu Cui, Kunwoo Yi, Aeree Chung, Jeffrey Hodgson, Tomohisa Kawashima, Tao An, Sascha Trippe, Juan Carlos Algaba, Jae Young Kim, Satoko Sawada-Satoh, Kiyoaki Wajima, Zhiqiang Shen, Xiaopeng Cheng, Ilje ChoWu Jiang, Taehyun Jung, Jee Won Lee, Kotaro Niinuma, Junghwan Oh, Fumie Tazaki, Guang Yao Zhao, Kazunori Akiyama, Mareki Honma, Jeong Ae Lee, Rusen Lu, Yingkang Zhang, Keiichi Asada, Lang Cui, Yoshiaki Hagiwara, Tomoya Hirota, Noriyuki Kawaguchi, Shoko Koyama, Sang Sung Lee, Se Jin Oh, Koichiro Sugiyama, Mieko Takamura, Xuezheng Wang, Ju Yeon Hwang, Dong Kyu Jung, Hyo Ryoung Kim, Jeong Sook Kim, Hideyuki Kobayashi, Chung Sik Oh, Tomoaki Oyama, Duk Gyoo Roh, Jae Hwan Yeom

Department of Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

6 Scopus citations

Abstract

Context. Because of its proximity and the large size of its black hole, M 87 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 M 87 jet are limited to the innermost part of the jet (≲100 rs) or to HST-1 (∼105 rs). No attempt has yet been made to measure the magnetic field strength in between. Aims. We aim to infer the magnetic field strength of the M 87 jet out to a distance of several thousand rs by tracking the distance-dependent changes in the synchrotron spectrum of the jet from high-resolution very long baseline interferometry observations. Methods. 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 Very Long Baseline Array (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. Results. The overall spectral morphology is broadly consistent over the course of these observations. The observed synchrotron spectrum rapidly steepens from α22-43GHz ∼-0.7 at ∼2 mas to α22-43GHz ∼-2.5 at ∼6 mas. In the KaVA observations, the spectral index remains unchanged until ∼10 mas, but this trend is unclear in the VLBA observations. 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 rs-∼4500 rs in the deprojected distance) has a range of B = (0.3-1.0-G)(z/2mas)-0.73. Extrapolating to the Event Horizon Telescope scale yields consistent results, suggesting that the majority of the magnetic flux of the jet near the black hole is preserved out to ∼4500 rs without significant dissipation.

Original language	English
Article number	A159
Journal	Astronomy and Astrophysics
Volume	673
DOIs	https://doi.org/10.1051/0004-6361/202142988
State	Published - 1 May 2023

Bibliographical note

Publisher Copyright:
© 2023 EDP Sciences. All rights reserved.

Keywords

Galaxies: active
Galaxies: individual: M 87
Galaxies: jets
Radio continuum: galaxies
Relativistic processes
Techniques: interferometric

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10.1051/0004-6361/202142988

Cite this

Ro, H., Kino, M., Sohn, B. W., Hada, K., Park, J., Nakamura, M., Cui, Y., Yi, K., Chung, A., Hodgson, J., Kawashima, T., An, T., Trippe, S., Algaba, J. C., Kim, J. Y., Sawada-Satoh, S., Wajima, K., Shen, Z., Cheng, X., ... Yeom, J. H. (2023). Spectral analysis of a parsec-scale jet in M 87: Observational constraint on the magnetic field strengths in the jet. Astronomy and Astrophysics, 673, Article A159. https://doi.org/10.1051/0004-6361/202142988

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title = "Spectral analysis of a parsec-scale jet in M 87: Observational constraint on the magnetic field strengths in the jet",

abstract = "Context. Because of its proximity and the large size of its black hole, M 87 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 M 87 jet are limited to the innermost part of the jet (≲100 rs) or to HST-1 (∼105 rs). No attempt has yet been made to measure the magnetic field strength in between. Aims. We aim to infer the magnetic field strength of the M 87 jet out to a distance of several thousand rs by tracking the distance-dependent changes in the synchrotron spectrum of the jet from high-resolution very long baseline interferometry observations. Methods. 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 Very Long Baseline Array (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. Results. The overall spectral morphology is broadly consistent over the course of these observations. The observed synchrotron spectrum rapidly steepens from α22-43GHz ∼-0.7 at ∼2 mas to α22-43GHz ∼-2.5 at ∼6 mas. In the KaVA observations, the spectral index remains unchanged until ∼10 mas, but this trend is unclear in the VLBA observations. 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 rs-∼4500 rs in the deprojected distance) has a range of B = (0.3-1.0-G)(z/2mas)-0.73. Extrapolating to the Event Horizon Telescope scale yields consistent results, suggesting that the majority of the magnetic flux of the jet near the black hole is preserved out to ∼4500 rs without significant dissipation.",

keywords = "Galaxies: active, Galaxies: individual: M 87, Galaxies: jets, Radio continuum: galaxies, Relativistic processes, Techniques: interferometric",

author = "Hyunwook Ro and Motoki Kino and Sohn, {Bong Won} and Kazuhiro Hada and Jongho Park and Masanori Nakamura and Yuzhu Cui and Kunwoo Yi and Aeree Chung and Jeffrey Hodgson and Tomohisa Kawashima and Tao An and Sascha Trippe and Algaba, {Juan Carlos} and Kim, {Jae Young} and Satoko Sawada-Satoh and Kiyoaki Wajima and Zhiqiang Shen and Xiaopeng Cheng and Ilje Cho and Wu Jiang and Taehyun Jung and Lee, {Jee Won} and Kotaro Niinuma and Junghwan Oh and Fumie Tazaki and Zhao, {Guang Yao} and Kazunori Akiyama and Mareki Honma and Lee, {Jeong Ae} and Rusen Lu and Yingkang Zhang and Keiichi Asada and Lang Cui and Yoshiaki Hagiwara and Tomoya Hirota and Noriyuki Kawaguchi and Shoko Koyama and Lee, {Sang Sung} and Oh, {Se Jin} and Koichiro Sugiyama and Mieko Takamura and Xuezheng Wang and Hwang, {Ju Yeon} and Jung, {Dong Kyu} and Kim, {Hyo Ryoung} and Kim, {Jeong Sook} and Hideyuki Kobayashi and Oh, {Chung Sik} and Tomoaki Oyama and Roh, {Duk Gyoo} and Yeom, {Jae Hwan}",

year = "2023",

month = may,

day = "1",

doi = "10.1051/0004-6361/202142988",

language = "English",

volume = "673",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

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Ro, H, Kino, M, Sohn, BW, Hada, K, Park, J, Nakamura, M, Cui, Y, Yi, K, Chung, A, Hodgson, J, Kawashima, T, An, T, Trippe, S, Algaba, JC, Kim, JY, Sawada-Satoh, S, Wajima, K, Shen, Z, Cheng, X, Cho, I, Jiang, W, Jung, T, Lee, JW, Niinuma, K, Oh, J, Tazaki, F, Zhao, GY, Akiyama, K, Honma, M, Lee, JA, Lu, R, Zhang, Y, Asada, K, Cui, L, Hagiwara, Y, Hirota, T, Kawaguchi, N, Koyama, S, Lee, SS, Oh, SJ, Sugiyama, K, Takamura, M, Wang, X, Hwang, JY, Jung, DK, Kim, HR, Kim, JS, Kobayashi, H, Oh, CS, Oyama, T, Roh, DG & Yeom, JH 2023, 'Spectral analysis of a parsec-scale jet in M 87: Observational constraint on the magnetic field strengths in the jet', Astronomy and Astrophysics, vol. 673, A159. https://doi.org/10.1051/0004-6361/202142988

TY - JOUR

T1 - Spectral analysis of a parsec-scale jet in M 87

T2 - Observational constraint on the magnetic field strengths in the jet

AU - Ro, Hyunwook

AU - Kino, Motoki

AU - Sohn, Bong Won

AU - Hada, Kazuhiro

AU - Park, Jongho

AU - Nakamura, Masanori

AU - Cui, Yuzhu

AU - Yi, Kunwoo

AU - Chung, Aeree

AU - Hodgson, Jeffrey

AU - Kawashima, Tomohisa

AU - An, Tao

AU - Trippe, Sascha

AU - Algaba, Juan Carlos

AU - Kim, Jae Young

AU - Sawada-Satoh, Satoko

AU - Wajima, Kiyoaki

AU - Shen, Zhiqiang

AU - Cheng, Xiaopeng

AU - Cho, Ilje

AU - Jiang, Wu

AU - Jung, Taehyun

AU - Lee, Jee Won

AU - Niinuma, Kotaro

AU - Oh, Junghwan

AU - Tazaki, Fumie

AU - Zhao, Guang Yao

AU - Akiyama, Kazunori

AU - Honma, Mareki

AU - Lee, Jeong Ae

AU - Lu, Rusen

AU - Zhang, Yingkang

AU - Asada, Keiichi

AU - Cui, Lang

AU - Hagiwara, Yoshiaki

AU - Hirota, Tomoya

AU - Kawaguchi, Noriyuki

AU - Koyama, Shoko

AU - Lee, Sang Sung

AU - Oh, Se Jin

AU - Sugiyama, Koichiro

AU - Takamura, Mieko

AU - Wang, Xuezheng

AU - Hwang, Ju Yeon

AU - Jung, Dong Kyu

AU - Kim, Hyo Ryoung

AU - Kim, Jeong Sook

AU - Kobayashi, Hideyuki

AU - Oh, Chung Sik

AU - Oyama, Tomoaki

AU - Roh, Duk Gyoo

AU - Yeom, Jae Hwan

PY - 2023/5/1

Y1 - 2023/5/1

N2 - Context. Because of its proximity and the large size of its black hole, M 87 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 M 87 jet are limited to the innermost part of the jet (≲100 rs) or to HST-1 (∼105 rs). No attempt has yet been made to measure the magnetic field strength in between. Aims. We aim to infer the magnetic field strength of the M 87 jet out to a distance of several thousand rs by tracking the distance-dependent changes in the synchrotron spectrum of the jet from high-resolution very long baseline interferometry observations. Methods. 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 Very Long Baseline Array (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. Results. The overall spectral morphology is broadly consistent over the course of these observations. The observed synchrotron spectrum rapidly steepens from α22-43GHz ∼-0.7 at ∼2 mas to α22-43GHz ∼-2.5 at ∼6 mas. In the KaVA observations, the spectral index remains unchanged until ∼10 mas, but this trend is unclear in the VLBA observations. 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 rs-∼4500 rs in the deprojected distance) has a range of B = (0.3-1.0-G)(z/2mas)-0.73. Extrapolating to the Event Horizon Telescope scale yields consistent results, suggesting that the majority of the magnetic flux of the jet near the black hole is preserved out to ∼4500 rs without significant dissipation.

AB - Context. Because of its proximity and the large size of its black hole, M 87 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 M 87 jet are limited to the innermost part of the jet (≲100 rs) or to HST-1 (∼105 rs). No attempt has yet been made to measure the magnetic field strength in between. Aims. We aim to infer the magnetic field strength of the M 87 jet out to a distance of several thousand rs by tracking the distance-dependent changes in the synchrotron spectrum of the jet from high-resolution very long baseline interferometry observations. Methods. 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 Very Long Baseline Array (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. Results. The overall spectral morphology is broadly consistent over the course of these observations. The observed synchrotron spectrum rapidly steepens from α22-43GHz ∼-0.7 at ∼2 mas to α22-43GHz ∼-2.5 at ∼6 mas. In the KaVA observations, the spectral index remains unchanged until ∼10 mas, but this trend is unclear in the VLBA observations. 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 rs-∼4500 rs in the deprojected distance) has a range of B = (0.3-1.0-G)(z/2mas)-0.73. Extrapolating to the Event Horizon Telescope scale yields consistent results, suggesting that the majority of the magnetic flux of the jet near the black hole is preserved out to ∼4500 rs without significant dissipation.

KW - Galaxies: active

KW - Galaxies: individual: M 87

KW - Galaxies: jets

KW - Radio continuum: galaxies

KW - Relativistic processes

KW - Techniques: interferometric

UR - http://www.scopus.com/inward/record.url?scp=85161028820&partnerID=8YFLogxK

U2 - 10.1051/0004-6361/202142988

DO - 10.1051/0004-6361/202142988

M3 - Article

AN - SCOPUS:85161028820

SN - 0004-6361

VL - 673

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A159

ER -

Spectral analysis of a parsec-scale jet in M 87: Observational constraint on the magnetic field strengths in the jet

Abstract

Bibliographical note

Keywords

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