宇宙科学広報・普及主幹付
Profile Information
- Affiliation
- Professor, Institute of Space and Astronautical Science, Japan Aerospace Exploration AgencyGraduate School of Science, Department of Physics, The University of Tokyo(PI), International Center for Quantum-field Measurement Systems for Studies of the Universe and Particles (QUP)Graduate School of Science, Kitasato University
- Degree
- Ph. D.(Mar, 1996, The University of Tokyo)
- ORCID ID
https://orcid.org/0000-0003-4885-5537- J-GLOBAL ID
- 200901003330670433
- Researcher ID
- C-2252-2008
- researchmap Member ID
- 5000019022
- External link
Research Interests
8Research Areas
2Research History
2Education
2-
Apr, 1989 - Mar, 1993
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Apr, 1985 - Mar, 1989
Committee Memberships
2-
Oct, 2017 - Sep, 2023
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Oct, 2014 - Sep, 2017
Papers
277-
Publications of the Astronomical Society of Japan, Mar 3, 2026Abstract The thermodynamic properties of the intracluster medium (ICM) at the outskirts of galaxy clusters provide valuable insights into the growth of the dark matter halo and the heating of the ICM. Considering the results of the soft X-ray background study of noncluster Suzaku fields, we revisit 65 Suzaku pointing observations of the Perseus cluster in eight azimuthal directions beyond ${\sim }1$ Mpc ($\sim$0.8$r_{500}$). A possible foreground component, whose spectrum is modeled as a 1 keV collisional ionization equilibrium plasma, significantly affects the temperature and density measurements of the ICM in cluster outskirts. The emission measures in the six arms are similar, showing that the radial slopes of temperature and density follow $r^{-0.67\pm 0.25}$ and $r^{-2.21\pm 0.06}$, respectively. The radial pressure profile is close to the average profile measured by the Planck satellite. The resulting entropy slope is $\propto r^{0.81\pm 0.25}$, consistent with the theoretical slope of 1.1. The integrated gas fraction, the ratio of the integrated gas mass to the hydrostatic mass, is estimated to be 0.13 $\pm$ 0.01 and 0.18 $\pm$ 0.02 at $r_{500}$ and $r_{200}$, respectively, consistent with the cosmic baryon fraction. These results suggest that the ICM at the cluster outskirts is quite regular and close to hydrostatic equilibrium. The remaining two arms show that the emission measure is higher by a factor of 1.5–2, possibly due to accretion from filaments from the large-scale structure. A sudden drop in the emission measure also occurs in a direction toward one of the filaments.
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The Astrophysical Journal, 998(2) 210-210, Feb 11, 2026Abstract 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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Astronomy & Astrophysics, 706 A86-A86, Feb 3, 2026Context. Hot, X-ray emitting atmospheres pervading galaxy clusters (and groups) are rich in metals, which have been synthesised and released by asymptotic giant branch (AGB) stars, core-collapse supernovae (SNcc), and Type Ia supernovae (SNIa) over cosmic history. This makes the intracluster medium (ICM) an ideal astrophysical system to constrain its chemical composition, and hence ultimately understand metal production and enrichment on megaparsec scales. Aims. In this work, we take advantage of the unprecedented ∼5 eV resolution offered by the Resolve instrument on board the XRISM observatory to measure the chemical composition of the core of the bright, nearby, and metal-rich Centaurus cluster with unprecedented accuracy. We use these measurements to provide constraints on the stellar populations having enriched the cluster core. Methods. Through a deep (287 ks) Resolve full-array spectral analysis of Centaurus, we derived the Fe abundance and its relative Si/Fe, S/Fe, Ar/Fe, Ca/Fe, Cr/Fe, Mn/Fe, and Ni/Fe ratios. We completed this high-resolution view with N/Fe, O/Fe, Ne/Fe, and Mg/Fe ratios obtained with XMM-Newton /RGS archival data. This abundance pattern was then fitted with various combinations of AGBs, SNcc and SNIa nucleosynthesis yields with the aim of constraining their explosion and/or progenitor models. Results. Similarly to the core of Perseus (from previous Hitomi /SXS results), we find that nine out of our 11 measured abundance ratios are formally consistent with the chemical composition of our Solar System (within uncertainties of the latter). However, the (super-solar) N/Fe and (half-solar) Mg/Fe ratios significantly differ from Perseus and/or other systems, and thus they provide tension with the picture of a fully solar composition ubiquitous to all systems. In addition, possible uncertainties in O/Fe and Ne/Fe with atomic codes highlight the need for studying more systems at high spectral resolution to assess (or rule out) the universality of the ICM composition in clusters’ cool cores. Combinations of (AGB+)SNcc+SNIa yield models can reproduce our observed X/Fe ratios in all cases. However, whether two distinct populations of SNIa are needed depends on the weight of our RGS measurements. We also briefly discuss the possibility of a multi-metallicity gas phase in this respect.
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Nature, 650(8101) 309-313, Jan 28, 2026
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NATURE ASTRONOMY, 10(1), Jan, 2026
Misc.
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地球電磁気・地球惑星圏学会総会及び講演会(Web), 156th, 2024
Teaching Experience
1-
Mar, 2003 - PresentAstrophysics I (Dept. of Physics, University. of Tokyo)
Professional Memberships
3-
2010 - Present
Research Projects
22-
Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Nov, 2020 - Mar, 2025
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Nov, 2020 - Mar, 2025
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科学研究費助成事業 基盤研究(A), 日本学術振興会, Apr, 2019 - Mar, 2022
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2018 - Mar, 2022
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Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Japan Society for the Promotion of Science, Apr, 2018 - Mar, 2021
教育内容やその他の工夫
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SubjcetGraduate School in ISASSummaryWe accept graduate students from University of Tokyo and Kitasato University. Our main scope is observational research of the large scale structure in the Universe utilizing X-ray spectroscopy.
During the graduate school, professional education for development of new detectors and their applications, and observational astrophysics are accessed.
● 指導学生等の数
10-
Fiscal Year2018年度(FY2018)Doctoral program1Master’s program1
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Fiscal Year2019年度(FY2019)Doctoral program1Master’s program3
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Fiscal Year2020年度(FY2020)Doctoral program1Master’s program3
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Fiscal Year2018年度(FY2018)Doctoral program1Master’s program1
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Fiscal Year2019年度(FY2019)Doctoral program1Master’s program3
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Fiscal Year2020年度(FY2020)Doctoral program1Master’s program3
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Fiscal Year2022年度(FY2022)Doctoral program3Master’s program2
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Fiscal Year2023年度(FY2023)Doctoral program2Master’s program1
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Fiscal Year2024年度(FY2024)Doctoral program2Master’s program2
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Fiscal Year2025年度(FY2025)Doctoral program2Master’s program5
● 指導学生の顕著な論文
6-
Student nameRyota TakakuStudent affiliation東京大学Author(s), journal, volume number, pagination (year of publication)Takaku et al. , Journal of Applied Physics, 128(22), id.225302, (2020)TitleBroadband, millimeter-wave anti-reflective structures on sapphire ablatedwith femto-second laserDOIhttp://doi.org/10.1063/5.0022765
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Student nameYuki NakashimaStudent affiliationUniv. of TokyoAuthor(s), journal, volume number, pagination (year of publication)Nakashima et al. Applied Physics Letters, 117 122601 (2020)TitleLow-noise microwave SQUID multiplexed readout of 38 x-ray transition-edge sensor microcalorimetersDOIhttp://doi.org/10.1063/5.0016333
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Student nameRyohei KonnoStudent affiliationKitasato Univ.Author(s), journal, volume number, pagination (year of publication)Konno et al. Journal of Low Temperature Physics 199, 654 (2019)TitleDevelopment of TES micsrocalorimters with solar-axion converterDOIhttp://doi.org/10.1007/s10909-019-02257-9
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Student nameRyo YamamotoStudent affiliationUniv. of TokyoAuthor(s), journal, volume number, pagination (year of publication)Yamamoto et al. , Journal of Cosmokogy and Astrophysics, 02 (2020) 011TitleA Search for a Contribution from Axion-Like Particles to the X-Ray Diffuse Background Utilizing the Earth's Magnetic FieldDOIhttp://doi.org/10.1088/1475-7516/2020/02/011
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Student nameNorio SekiyaStudent affiliationUniversity. of TokyoAuthor(s), journal, volume number, pagination (year of publication)Sekiya, Yamasaki, and Mitsuda, Publications of Astronomical Society in Japan, 68(SP1), S31 (2016)TitleSearch for a keV Signature of Radiatively Decaying Dark Matter with Suzaku XIS Observations of the X-ray Diffuse BackgroundDOIhttp://doi.org/10.1093/pasj/psv081
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Student nameIkuyuki MitsuishiStudent affiliationUniv. of TokyoAuthor(s), journal, volume number, pagination (year of publication)Mitsuishi, Yamasaki, and Takei, Publications of Astronomical Society in Japan, 65, 44 (2013)TitleAn X-Ray Study of the Galactic-Scale Starburst-Driven Outflow in NGC 253DOIhttp://doi.org/10.1093/pasj/65.2.44
● 専任大学名
1-
Affiliation (university)東京大学（University of Tokyo)
● 所属する所内委員会
1-
ISAS CommitteeSteering committee for ISAS nono-electronics clean room
