The Intrinsic Structure of Sagittarius A* at 1.3 cm and 7 mm
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Published:2022-02-01
Issue:2
Volume:926
Page:108
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ISSN:0004-637X
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Container-title:The Astrophysical Journal
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language:
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Short-container-title:ApJ
Author:
Cho IljeORCID, Zhao Guang-YaoORCID, Kawashima TomohisaORCID, Kino MotokiORCID, Akiyama KazunoriORCID, Johnson Michael D.ORCID, Issaoun SaraORCID, Moriyama KotaroORCID, Cheng XiaopengORCID, Algaba Juan-CarlosORCID, Jung TaehyunORCID, Sohn Bong WonORCID, Krichbaum Thomas P.ORCID, Wielgus MaciekORCID, Hada KazuhiroORCID, Lu Ru-SenORCID, Cui YuzhuORCID, Sawada-Satoh SatokoORCID, Shen ZhiqiangORCID, Park JonghoORCID, Jiang WuORCID, Ro HyunwookORCID, Yi Kunwoo, Wajima KiyoakiORCID, Lee Jee WonORCID, Hodgson Jeffrey, Tazaki FumieORCID, Honma MarekiORCID, Niinuma KotaroORCID, Trippe SaschaORCID, An TaoORCID, Zhang Yingkang, Lee Jeong Ae, Oh Se-Jin, Byun Do-YoungORCID, Lee Sang-SungORCID, Kim Jae-YoungORCID, Oh JunghwanORCID, Koyama ShokoORCID, Asada Keiichi, Wang Xuezheng, Cui LangORCID, Hagiwara YoshiakiORCID, Nakamura MasanoriORCID, Takamura Mieko, Hirota TomoyaORCID, Sugiyama KoichiroORCID, Kawaguchi NoriyukiORCID, Kobayashi HideyukiORCID, Oyama Tomoaki, Yonekura YoshinoriORCID, Kim JongsooORCID, 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, Chen Zhong
Abstract
Abstract
Sagittarius A* (Sgr A*), the Galactic Center supermassive black hole (SMBH), is one of the best targets in which to resolve the innermost region of an 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 multiwavelength 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 ± 102 μas (axial ratio ∼
1.19
−
0.19
+
0.24
) and ∼300 ± 25 μas (axial ratio ∼1.28 ± 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 ∼1.2 ± 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.
Funder
National Research Foundation of Korea Ministerio de Ciencia, Innovación y Universidades National Science Foundation Mitsubishi Foundation Gordon and Betty Moore Foundation National Natural Science Foundation of China Spanish Ministerio de Economia y Competitividad Malaysian Fundamental Research Grant Scheme Japan Society for the Promotion of Science Research Program of Fundamental and Frontier Sciences
Publisher
American Astronomical Society
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
12 articles.
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