惑星分光観測衛星プロジェクトチーム
Profile Information
- Affiliation
- Institute of Space and Astronautical Science, Japan Aerospace Exploration AgencySchool of Physical Sciences Department of Space and Astronautical Science, The Graduate University for Advanced Studies
- Degree
- 博士 (理学)(Mar, 2005, 東京大学)
- Researcher number
- 90403641
- ORCID ID
https://orcid.org/0000-0003-4384-9568- J-GLOBAL ID
- 201101033666007265
- researchmap Member ID
- B000004312
Research Interests
11Research Areas
3Research History
3-
Apr, 2005 - Mar, 2007
Papers
97-
Monthly Notices of the Royal Astronomical Society, 530(3) 2590-2607, Apr 15, 2024ABSTRACT A substantial fraction of quasars display broad absorption lines (BALs) in their rest-frame ultraviolet spectra. While the origin of BALs is thought to be related to the accretion disc wind, it remains unclear whether the observed ratio of BAL to non-BAL quasars is a result of orientation. We conducted observations of 48 BAL quasars and the same number of non-BAL quasars at 322 MHz using the Giant Metrewave Radio Telescope. Combined with previous flux measurements ranging from MHz to GHz frequencies, we compared continuum radio spectra between the two quasar groups. These data offer insights into low-frequency radio properties that have been difficult to investigate with previous observations only at GHz frequencies. Our results show that 73 ± 13 per cent of the BAL quasars exhibit steep or peaked spectra, a higher proportion than the 44 ± 14 per cent observed in the non-BAL quasars. In contrast, there are no discernible differences between the two quasar groups in the radio luminosity, peak frequency, and spectral index distributions of sources with steep or peaked spectra and sources with flat or inverted spectra. Generally, as the jet axis and line of sight become closer to parallel, quasars exhibit flat or inverted spectra rather than steep or peaked spectra. Therefore, these results suggest that BAL quasars are more frequently observed farther from the jet axis than non-BAL quasars. However, given that a certain proportion of BAL quasars exhibit flat or inverted spectra, more than the simple orientation scenario is required to elucidate the radio properties of BAL quasars.
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JAXA Research and Development Report, 23(003) 1-21, Feb, 2024 Peer-reviewed
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Publications of the Astronomical Society of Japan, Oct 3, 2023 Peer-reviewed
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The Astrophysical Journal, Jul 1, 2023 Peer-reviewed
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Nature, 616(7958) 686-690, Apr 26, 2023 Peer-reviewedAbstract The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation1,2. Event Horizon Telescope observations of M87 in 2017, at a wavelength of 1.3 mm, revealed a ring-like structure, which was interpreted as gravitationally lensed emission around a central black hole3. Here we report images of M87 obtained in 2018, at a wavelength of 3.5 mm, showing that the compact radio core is spatially resolved. High-resolution imaging shows a ring-like structure of $${8.4}_{-1.1}^{+0.5}$$ Schwarzschild radii in diameter, approximately 50% larger than that seen at 1.3 mm. The outer edge at 3.5 mm is also larger than that at 1.3 mm. This larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects, in addition to the gravitationally lensed ring-like emission. The images show that the edge-brightened jet connects to the accretion flow of the black hole. Close to the black hole, the emission profile of the jet-launching region is wider than the expected profile of a black-hole-driven jet, suggesting the possible presence of a wind associated with the accretion flow.
Misc.
64-
宇宙科学技術連合講演会講演集(CD-ROM), 67th, 2023
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Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray, Aug 31, 2022
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VLBI Future Planning Working Group Review Report, June 2021, 4th Edition, Jun, 2021
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Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave, Dec 13, 2020
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Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray, Dec 13, 2020
Presentations
28Research Projects
12-
Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2023 - Mar, 2028
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Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Japan Society for the Promotion of Science, Apr, 2020 - Mar, 2023
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科学研究費(基盤研究(B)), 日本学術振興会, Apr, 2017 - Mar, 2020
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研究助成金, カシオ科学振興財団, Oct, 2016 - Nov, 2017
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Observational study of jet-formation regions in supermassive black holes with a novel VLBI techniqueGrants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2014 - Mar, 2017
