研究者業績
基本情報
- 所属
- 国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 宇宙物理学研究系 教授総合研究大学院大学 先端学術院 宇宙科学コース 教授東京科学大学 理学院物理学系物理学コース 特定教授関西学院大学 大学院理工学研究科 客員教授
- 学位
- 理学博士(東京大学)
- J-GLOBAL ID
- 200901025041369206
- researchmap会員ID
- 1000144439
専門はＸ線天文学。特に、中性子星やブラックホールを含むX線連星の観測的研究および衛星搭載X線CCDカメラの開発研究。
受賞
1-
1996年
論文
246-
The Astrophysical Journal 998(2) 210-210 2026年2月11日Abstract The XRISM/Resolve microcalorimeter directly measured the gas velocities in the core of the Virgo Cluster, the closest example of active galactic nucleus (AGN) feedback in a cluster. This proximity allows us to resolve the kinematic impact of feedback on scales down to 5 kpc. Our spectral analysis reveals a high velocity dispersion of km s −1 near the AGN, which steeply declines to ∼60 km s −1 between 5 and 25 kpc in the northwest direction. The observed line-of-sight bulk velocity in all regions is broadly consistent with the central galaxy, M87, with a mild trend toward blueshifted motions at larger radii. Systematic uncertainties have been carefully assessed and do not affect the measurements. The central velocities, if attributed entirely to isotropic turbulence, correspond to a transonic intracluster medium at sub-6 kpc scales with 3D Mach number and a nonthermal pressure fraction of . Simple models of weak shocks and sound waves and calculations assuming isotropic turbulence both support the hypothesis that the velocity field reflects a mix of shock-driven expansion and turbulence. Compared to other clusters observed by XRISM to date, M87’s central region stands out as the most kinematically disturbed, exhibiting both the highest velocity dispersion and the largest 3D Mach number, concentrated at the smallest physical scales.
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Nature 650(8101) 309-313 2026年1月28日
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NATURE ASTRONOMY 10(1) 2026年1月
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The Astrophysical Journal Letters 994(1) L28-L28 2025年11月18日Abstract We stack 3.75 Ms of early XRISM Resolve observations of 10 galaxy clusters to search for unidentified spectral lines in the E = 2.5–15 keV band (rest frame), including the E = 3.5 keV line reported in earlier low spectral resolution studies of cluster samples. Such an emission line may originate from the decay of the sterile neutrino, a warm dark matter (DM) candidate. No unidentified lines are detected in our stacked cluster spectrum, with the 3 σ upper limit on the m s ∼ 7.1 keV DM particle decay rate (which corresponds to an E = 3.55 keV emission line) of Γ ∼ 1.0 × 10 −27 s −1 . This upper limit is 3–4 times lower than the one derived by Hitomi Collaboration from the Perseus observation but still 5 times higher than the XMM-Newton detection reported by E. Bulbul et al. in the stacked cluster sample. XRISM Resolve, with its high spectral resolution but small field of view, may reach the sensitivity needed to test the XMM-Newton cluster sample detection by combining several years worth of future cluster observations.
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Publications of the Astronomical Society of Japan 77(6) 1278-1289 2025年11月17日Abstract We present results from XRISM/Resolve observations of the core of the galaxy cluster Abell 2319, focusing on its kinematic properties. The intracluster medium (ICM) exhibits temperatures of approximately 8 keV across the core, with a prominent cold front and a high-temperature region ($\sim$11 keV) in the north-west. The average gas velocity in the $3{^{\prime } } \times$ $4 {^{\prime } }$ region around the brightest cluster galaxy (BCG) covered by two Resolve pointings is consistent with that of the BCG to within 40 km s$^{-1}$ and we found modest average velocity dispersion of 230–250 km s$^{-1}$. On the other hand, spatially resolved spectroscopy reveals interesting variations. A blueshift of up to $\sim$230 km s$^{-1}$ is observed around the east edge of the cold front, where the gas with the lowest specific entropy is found. The region further south inside the cold front shows only a small velocity difference from the BCG; however, its velocity dispersion is enhanced to $\sim$400 km s$^{-1}$, implying the development of turbulence. These characteristics indicate that we are observing sloshing motion with some inclination angle following BCG and that gas phases with different specific entropy participate in sloshing with their own velocities, as expected from simulations. No significant evidence for a high-redshift ICM component associated with the subcluster Abell 2319B was found in the region covered by the current Resolve pointings. These results highlight the importance of sloshing and turbulence in shaping the internal structure of Abell 2319. Further deep observations are necessary to better understand the mixing and turbulent processes within the cluster.
MISC
203-
Publications of the Astronomical Society of Japan 70(2) 2018年3月1日
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J. Astron. Telesc. Instrum. Syst. 4(1), 011211 (2018) 4(1) 2018年1月22日
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Proceedings of SPIE - The International Society for Optical Engineering 10699 2018年1月1日
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70(2) 2017年7月1日The Crab nebula originated from a core-collapse supernova (SN) explosion<br /> observed in 1054 A.D. When viewed as a supernova remnant (SNR), it has an<br /> anomalously low observed ejecta mass and kinetic energy for an Fe-core collapse<br /> SN. Intensive searches were made for a massive shell that solves this<br /> discrepancy, but none has been detected. An alternative idea is that the SN1054<br /> is an electron-capture (EC) explosion with a lower explosion energy by an order<br /> of magnitude than Fe-core collapse SNe. In the X-rays, imaging searches were<br /> performed for the plasma emission from the shell in the Crab outskirts to set a<br /> stringent upper limit to the X-ray emitting mass. However, the extreme<br /> brightness of the source hampers access to its vicinity. We thus employed<br /> spectroscopic technique using the X-ray micro-calorimeter onboard the Hitomi<br /> satellite. By exploiting its superb energy resolution, we set an upper limit<br /> for emission or absorption features from yet undetected thermal plasma in the<br /> 2-12 keV range. We also re-evaluated the existing Chandra and XMM-Newton data.<br /> By assembling these results, a new upper limit was obtained for the X-ray<br /> plasma mass of <~ 1Mo for a wide range of assumed shell radius, size, and<br /> plasma temperature both in and out of the collisional equilibrium. To compare<br /> with the observation, we further performed hydrodynamic simulations of the Crab<br /> SNR for two SN models (Fe-core versus EC) under two SN environments (uniform<br /> ISM versus progenitor wind). We found that the observed mass limit can be<br /> compatible with both SN models if the SN environment has a low density of <~<br /> 0.03 cm-3 (Fe core) or <~ 0.1 cm-3 (EC) for the uniform density, or a<br /> progenitor wind density somewhat less than that provided by a mass loss rate of<br /> 10-5 Mo yr-1 at 20 km s-1 for the wind environment.
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ASTROPHYSICAL JOURNAL LETTERS 837(1) 2017年3月
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SPACE TELESCOPES AND INSTRUMENTATION 2016: OPTICAL, INFRARED, AND MILLIMETER WAVE 9904 2016年 査読有り
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日本物理学会講演概要集 69(2) 37-37 2014年8月22日
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日本物理学会講演概要集 69(1) 129-129 2014年3月5日
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日本物理学会講演概要集 68(1) 134-134 2013年3月26日
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PASJ : publications of the Astronomical Society of Japan 64(5) "112-1"-"112-11" 2012年10月25日
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電子情報通信学会技術研究報告. SANE, 宇宙・航行エレクトロニクス 112(229) 17-22 2012年10月3日Japan Aerospace Exploration Agency (JAXA) has been developing an X-ray astronomy satellite named "ASTRO-H", which will be launched in 2014. This paper provides a summary of the design overview and development status of an electrical power subsystem for ASTRO-H. The subsystem consists of rigid solar array paddles that generate approximately 3500W at the end of life of the system, a power control unit that delivers an unregulated 50V bus power supply, shunt dissipators, battery charge control units, two 100-Ah Li-ion batteries, and a non-explosive actuator controller. Currently, manufacturing and verification tests for the satellite system have been implemented for the launch.
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日本物理学会講演概要集 67(2) 119-119 2012年8月24日
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日本物理学会講演概要集 67(2) 119-119 2012年8月24日
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Astrophysical Journal 753(2) 2012年7月10日
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PASJ : publications of the Astronomical Society of Japan 64(3) "53-1"-"53-12" 2012年6月25日
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日本物理学会講演概要集 67(1) 139-139 2012年3月5日
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SUZAKU 2011: Exploring the X-ray Universe: Suzaku and Beyond. AIP Conference Proceedings 1427 247-248 2012年3月
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SUZAKU 2011: EXPLORING THE X-RAY UNIVERSE: SUZAKU AND BEYOND 1427 253-254 2012年 査読有り
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日本物理学会講演概要集 66(2) 112-112 2011年8月24日
所属学協会
4-
2000年1月 - 現在
共同研究・競争的資金等の研究課題
15-
日本学術振興会 科学研究費助成事業 基盤研究(C) 2019年4月 - 2023年3月
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日本学術振興会 科学研究費助成事業 新学術領域研究(研究領域提案型) 2012年6月 - 2017年3月
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日本学術振興会 科学研究費助成事業 2012年4月 - 2015年3月
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日本学術振興会 科学研究費助成事業 基盤研究(B) 2010年4月 - 2013年3月
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日本学術振興会 科学研究費助成事業 特別研究員奨励費 2005年 - 2007年
● 指導学生等の数
1-
年度2021年度(FY2021)修士課程学生数2連携大学院制度による学生数2学術特別研究員数1
● 専任大学名
1-
専任大学名総合研究大学院大学（SOKENDAI)
