Kinematics of the M87 Jet in the Collimation Zone: Gradual Acceleration and Velocity Stratification

Jongho Park; Kazuhiro Hada; Motoki Kino; Masanori Nakamura; Jeffrey Hodgson; Hyunwook Ro; Yuzhu Cui; Keiichi Asada; Juan Carlos Algaba; Satoko Sawada-Satoh; Sang Sung Lee; Ilje Cho; Zhiqiang Shen; Wu Jiang; Sascha Trippe; Kotaro Niinuma; Bong Won Sohn; Taehyun Jung; Guang Yao Zhao; Kiyoaki Wajima; Fumie Tazaki; Mareki Honma; Tao An; Kazunori Akiyama; Do Young Byun; Jongsoo Kim; Yingkang Zhang; Xiaopeng Cheng; Hideyuki Kobayashi; Katsunori M. Shibata; Jee Won Lee; Duk Gyoo Roh; Se Jin Oh; Jae Hwan Yeom; Dong Kyu Jung; Chungsik Oh; Hyo Ryoung Kim; Ju Yeon Hwang; Yoshiaki Hagiwara

doi:10.3847/1538-4357/ab5584

Kinematics of the M87 Jet in the Collimation Zone: Gradual Acceleration and Velocity Stratification

Jongho Park, Kazuhiro Hada, Motoki Kino, Masanori Nakamura, Jeffrey Hodgson, Hyunwook Ro, Yuzhu Cui, Keiichi Asada, Juan Carlos Algaba, Satoko Sawada-Satoh, Sang Sung Lee, Ilje Cho, Zhiqiang Shen, Wu Jiang, Sascha Trippe, Kotaro Niinuma, Bong Won Sohn, Taehyun Jung, Guang Yao Zhao, Kiyoaki WajimaFumie Tazaki, Mareki Honma, Tao An, Kazunori Akiyama, Do Young Byun, Jongsoo Kim, Yingkang Zhang, Xiaopeng Cheng, Hideyuki Kobayashi, Katsunori M. Shibata, Jee Won Lee, Duk Gyoo Roh, Se Jin Oh, Jae Hwan Yeom, Dong Kyu Jung, Chungsik Oh, Hyo Ryoung Kim, Ju Yeon Hwang, Yoshiaki Hagiwara

Department of Physics and Astronomy

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

54 Scopus citations

Abstract

We study the kinematics of the M87 jet using the first-year data of the KVN and VERA Array (KaVA) large program, which has densely monitored the jet at 22 and 43 GHz since 2016. We find that the apparent jet speeds generally increase from ≈0.3c at ≈0.5 mas from the jet base to ≈2.7c at ≈20 mas, indicating that the jet is accelerated from subluminal to superluminal speeds on these scales. We perform a complementary jet kinematic analysis by using archival Very Long Baseline Array monitoring data observed in 2005-2009 at 1.7 GHz and find that the jet is moving at relativistic speeds up to ≈5.8c at distances of 200-410 mas. We combine the two kinematic results and find that the jet is gradually accelerated over a broad distance range that coincides with the jet collimation zone, implying that conversion of Poynting flux to kinetic energy flux takes place. If the jet emission consists of a single streamline, the observed trend of jet acceleration (Γ ∝ z ^0.16±0.01) is relatively slow compared to models of a highly magnetized jet. This indicates that Poynting flux conversion through the differential collimation of poloidal magnetic fields may be less efficient than expected. However, we find a nonnegligible dispersion in the observed speeds for a given jet distance, making it difficult to describe the jet velocity field with a single power-law acceleration function. We discuss the possibility that the jet emission consists of multiple streamlines following different acceleration profiles, resulting in jet velocity stratification.

Original language	English
Article number	147
Journal	Astrophysical Journal
Volume	887
Issue number	2
DOIs	https://doi.org/10.3847/1538-4357/ab5584
State	Published - 20 Dec 2019

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© 2019. The American Astronomical Society. All rights reserved.

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Park, J., Hada, K., Kino, M., Nakamura, M., Hodgson, J., Ro, H., Cui, Y., Asada, K., Algaba, J. C., Sawada-Satoh, S., Lee, S. S., Cho, I., Shen, Z., Jiang, W., Trippe, S., Niinuma, K., Sohn, B. W., Jung, T., Zhao, G. Y., ... Hagiwara, Y. (2019). Kinematics of the M87 Jet in the Collimation Zone: Gradual Acceleration and Velocity Stratification. Astrophysical Journal, 887(2), Article 147. https://doi.org/10.3847/1538-4357/ab5584

@article{d2a574b812d346c686e1504fc7d01a9d,

title = "Kinematics of the M87 Jet in the Collimation Zone: Gradual Acceleration and Velocity Stratification",

abstract = "We study the kinematics of the M87 jet using the first-year data of the KVN and VERA Array (KaVA) large program, which has densely monitored the jet at 22 and 43 GHz since 2016. We find that the apparent jet speeds generally increase from ≈0.3c at ≈0.5 mas from the jet base to ≈2.7c at ≈20 mas, indicating that the jet is accelerated from subluminal to superluminal speeds on these scales. We perform a complementary jet kinematic analysis by using archival Very Long Baseline Array monitoring data observed in 2005-2009 at 1.7 GHz and find that the jet is moving at relativistic speeds up to ≈5.8c at distances of 200-410 mas. We combine the two kinematic results and find that the jet is gradually accelerated over a broad distance range that coincides with the jet collimation zone, implying that conversion of Poynting flux to kinetic energy flux takes place. If the jet emission consists of a single streamline, the observed trend of jet acceleration (Γ ∝ z 0.16±0.01) is relatively slow compared to models of a highly magnetized jet. This indicates that Poynting flux conversion through the differential collimation of poloidal magnetic fields may be less efficient than expected. However, we find a nonnegligible dispersion in the observed speeds for a given jet distance, making it difficult to describe the jet velocity field with a single power-law acceleration function. We discuss the possibility that the jet emission consists of multiple streamlines following different acceleration profiles, resulting in jet velocity stratification.",

author = "Jongho Park and Kazuhiro Hada and Motoki Kino and Masanori Nakamura and Jeffrey Hodgson and Hyunwook Ro and Yuzhu Cui and Keiichi Asada and Algaba, {Juan Carlos} and Satoko Sawada-Satoh and Lee, {Sang Sung} and Ilje Cho and Zhiqiang Shen and Wu Jiang and Sascha Trippe and Kotaro Niinuma and Sohn, {Bong Won} and Taehyun Jung and Zhao, {Guang Yao} and Kiyoaki Wajima and Fumie Tazaki and Mareki Honma and Tao An and Kazunori Akiyama and Byun, {Do Young} and Jongsoo Kim and Yingkang Zhang and Xiaopeng Cheng and Hideyuki Kobayashi and Shibata, {Katsunori M.} and Lee, {Jee Won} and Roh, {Duk Gyoo} and Oh, {Se Jin} and Yeom, {Jae Hwan} and Jung, {Dong Kyu} and Chungsik Oh and Kim, {Hyo Ryoung} and Hwang, {Ju Yeon} and Yoshiaki Hagiwara",

year = "2019",

month = dec,

day = "20",

doi = "10.3847/1538-4357/ab5584",

language = "English",

volume = "887",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "American Astronomical Society",

number = "2",

}

Park, J, Hada, K, Kino, M, Nakamura, M, Hodgson, J, Ro, H, Cui, Y, Asada, K, Algaba, JC, Sawada-Satoh, S, Lee, SS, Cho, I, Shen, Z, Jiang, W, Trippe, S, Niinuma, K, Sohn, BW, Jung, T, Zhao, GY, Wajima, K, Tazaki, F, Honma, M, An, T, Akiyama, K, Byun, DY, Kim, J, Zhang, Y, Cheng, X, Kobayashi, H, Shibata, KM, Lee, JW, Roh, DG, Oh, SJ, Yeom, JH, Jung, DK, Oh, C, Kim, HR, Hwang, JY & Hagiwara, Y 2019, 'Kinematics of the M87 Jet in the Collimation Zone: Gradual Acceleration and Velocity Stratification', Astrophysical Journal, vol. 887, no. 2, 147. https://doi.org/10.3847/1538-4357/ab5584

TY - JOUR

T1 - Kinematics of the M87 Jet in the Collimation Zone

T2 - Gradual Acceleration and Velocity Stratification

AU - Park, Jongho

AU - Hada, Kazuhiro

AU - Kino, Motoki

AU - Nakamura, Masanori

AU - Hodgson, Jeffrey

AU - Ro, Hyunwook

AU - Cui, Yuzhu

AU - Asada, Keiichi

AU - Algaba, Juan Carlos

AU - Sawada-Satoh, Satoko

AU - Lee, Sang Sung

AU - Cho, Ilje

AU - Shen, Zhiqiang

AU - Jiang, Wu

AU - Trippe, Sascha

AU - Niinuma, Kotaro

AU - Sohn, Bong Won

AU - Jung, Taehyun

AU - Zhao, Guang Yao

AU - Wajima, Kiyoaki

AU - Tazaki, Fumie

AU - Honma, Mareki

AU - An, Tao

AU - Akiyama, Kazunori

AU - Byun, Do Young

AU - Kim, Jongsoo

AU - Zhang, Yingkang

AU - Cheng, Xiaopeng

AU - Kobayashi, Hideyuki

AU - Shibata, Katsunori M.

AU - Lee, Jee Won

AU - Roh, Duk Gyoo

AU - Oh, Se Jin

AU - Yeom, Jae Hwan

AU - Jung, Dong Kyu

AU - Oh, Chungsik

AU - Kim, Hyo Ryoung

AU - Hwang, Ju Yeon

AU - Hagiwara, Yoshiaki

PY - 2019/12/20

Y1 - 2019/12/20

N2 - We study the kinematics of the M87 jet using the first-year data of the KVN and VERA Array (KaVA) large program, which has densely monitored the jet at 22 and 43 GHz since 2016. We find that the apparent jet speeds generally increase from ≈0.3c at ≈0.5 mas from the jet base to ≈2.7c at ≈20 mas, indicating that the jet is accelerated from subluminal to superluminal speeds on these scales. We perform a complementary jet kinematic analysis by using archival Very Long Baseline Array monitoring data observed in 2005-2009 at 1.7 GHz and find that the jet is moving at relativistic speeds up to ≈5.8c at distances of 200-410 mas. We combine the two kinematic results and find that the jet is gradually accelerated over a broad distance range that coincides with the jet collimation zone, implying that conversion of Poynting flux to kinetic energy flux takes place. If the jet emission consists of a single streamline, the observed trend of jet acceleration (Γ ∝ z 0.16±0.01) is relatively slow compared to models of a highly magnetized jet. This indicates that Poynting flux conversion through the differential collimation of poloidal magnetic fields may be less efficient than expected. However, we find a nonnegligible dispersion in the observed speeds for a given jet distance, making it difficult to describe the jet velocity field with a single power-law acceleration function. We discuss the possibility that the jet emission consists of multiple streamlines following different acceleration profiles, resulting in jet velocity stratification.

AB - We study the kinematics of the M87 jet using the first-year data of the KVN and VERA Array (KaVA) large program, which has densely monitored the jet at 22 and 43 GHz since 2016. We find that the apparent jet speeds generally increase from ≈0.3c at ≈0.5 mas from the jet base to ≈2.7c at ≈20 mas, indicating that the jet is accelerated from subluminal to superluminal speeds on these scales. We perform a complementary jet kinematic analysis by using archival Very Long Baseline Array monitoring data observed in 2005-2009 at 1.7 GHz and find that the jet is moving at relativistic speeds up to ≈5.8c at distances of 200-410 mas. We combine the two kinematic results and find that the jet is gradually accelerated over a broad distance range that coincides with the jet collimation zone, implying that conversion of Poynting flux to kinetic energy flux takes place. If the jet emission consists of a single streamline, the observed trend of jet acceleration (Γ ∝ z 0.16±0.01) is relatively slow compared to models of a highly magnetized jet. This indicates that Poynting flux conversion through the differential collimation of poloidal magnetic fields may be less efficient than expected. However, we find a nonnegligible dispersion in the observed speeds for a given jet distance, making it difficult to describe the jet velocity field with a single power-law acceleration function. We discuss the possibility that the jet emission consists of multiple streamlines following different acceleration profiles, resulting in jet velocity stratification.

UR - http://www.scopus.com/inward/record.url?scp=85077639825&partnerID=8YFLogxK

U2 - 10.3847/1538-4357/ab5584

DO - 10.3847/1538-4357/ab5584

M3 - Article

AN - SCOPUS:85077639825

SN - 0004-637X

VL - 887

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2

M1 - 147

ER -

Kinematics of the M87 Jet in the Collimation Zone: Gradual Acceleration and Velocity Stratification

Abstract

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