Curriculum Vitaes
Profile Information
- Affiliation
- School of Medicine Faculty of Medicine, Fujita Health University
- Degree
- 博士（理学）(名古屋大学)
- J-GLOBAL ID
- 200901003971539256
- researchmap Member ID
- 6000001840
Research Interests
8Research Areas
4Research History
1Education
1Papers
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The Astrophysical Journal, 998(2) 210-210, Feb 11, 2026 Peer-reviewedAbstract 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, Jan 28, 2026 Peer-reviewed
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NATURE ASTRONOMY, 10(1), Jan, 2026
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The Astrophysical Journal Letters, 994(1) L28-L28, Nov 18, 2025Abstract 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, Nov 17, 2025Abstract 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.
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The Astrophysical Journal Letters, 993(1) L11-L11, Oct 24, 2025Abstract The dynamics of the intracluster medium (ICM), the hot plasma that fills galaxy clusters, are shaped by gravity-driven cluster mergers and feedback from supermassive black holes (SMBHs) in the cluster cores. XRISM measurements of ICM velocities in several clusters offer insights into these processes. We compare XRISM measurements for nine galaxy clusters (Virgo, Perseus, Centaurus, Hydra-A, PKS 0745–19, A2029, Coma, A2319, and Ophiuchus) with predictions from three state-of-the-art cosmological simulation suites, TNG-Cluster, the Three Hundred Project GADGET-X, and GIZMO-SIMBA, that employ different models of feedback. In cool cores, XRISM reveals systematically lower velocity dispersions than the simulations predict, with all 10 measurements below the median simulated values by a factor of 1.5–1.7 on average and all falling within the bottom 10% of the predicted distributions. The observed kinetic-to-total pressure ratio is also lower, with a median value of 2.2%, compared to the predicted 5.0%–6.5% for the three simulations. Outside the cool cores and in non-cool-core (NCC) clusters, simulations show better agreement with XRISM measurements, except for the outskirts of the relaxed, cool-core cluster A2029, which exhibits an exceptionally low kinetic pressure support (<1%), with none of the simulated systems in either of the three suites reaching such low levels. The NCC Coma and A2319 exhibit dispersions at the lower end but within the simulated spread. Our comparison suggests that the three numerical models may overestimate the kinetic effects of SMBH feedback in cluster cores. Additional XRISM observations of NCC clusters will clarify if there is a systematic tension in the gravity-dominated regime as well.
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Astronomy & Astrophysics, 702 A147-A147, Oct 15, 2025Context. Accurate X-ray spectroscopic measurements are fundamental for deriving basic physical parameters of the most abundant baryon components in the Universe. The plethora of X-ray observatories currently operational enables a panchromatic view of the high-energy emission of celestial sources. However, uncertainties in the energy-dependent calibration of the instrument transfer functions (e.g. the effective area, energy redistribution, or gain) can limit - and historically, did limit - the accuracy of X-ray spectroscopic measurements. Aims. We revised the status of the cross-calibration among the scientific payload on board four operation missions: Chandra, NuSTAR, XMM-Newton, and the recently launched XRISM. XRISM carries the micro-calorimeter Resolve, which yields the best energy resolution at energies ≥2 keV. For this purpose, we used the data from a 10-day-long observational campaign targeting the nearby active galactic nucleus NGC 3783, carried out in July 2024. Methods. We present a novel model-independent method for assessing the cross-calibration status that is based on a multi-node spline of the spectra with the highest-resolving power (XRISM/Resolve in our campaign). We also estimated the impact of the intrinsic variability of NGC 3783 on the cross-calibration status due to the different time coverages of participating observatories and performed an empirical reassessment of the Resolve throughput at low energies. Results. Based on this analysis, we derived a set of energy-dependent correction factors of the observed responses, enabling a statistically robust analysis of the whole spectral dataset. They will be employed in subsequent papers describing the astrophysical results of the campaign.
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Nature, 646(8083) 57-61, Sep 17, 2025 Peer-reviewed
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Publications of the Astronomical Society of Japan, 77(Supplement_1) S242-S253, Aug 18, 2025Abstract We report on a detailed spectroscopic study of the gas dynamics and hydrostatic mass bias of the galaxy cluster Abell 2029, utilizing high-resolution observations from XRISM Resolve. Abell 2029, known for its cool core and relaxed X-ray morphology, provides an excellent opportunity to investigate the influence of gas motions beyond the central region. Expanding upon prior studies that revealed low turbulence and bulk motions within the core, our analysis covers regions out to the scale radius $R_{2500}$ (670 kpc) based on three radial pointings extending from the cluster center toward the northern side. We obtain accurate measurements of bulk and turbulent velocities along the line of sight. The results indicate that non-thermal pressure accounts for no more than 2% of the total pressure at all radii, with a gradual decrease outward. The observed radial trend differs from many numerical simulations, which often predict an increase in non-thermal pressure fraction at larger radii. These findings suggest that deviations from hydrostatic equilibrium are small, leading to a hydrostatic mass bias of around 2% across the observed area.
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Publications of the Astronomical Society of Japan, 77(Supplement_1) S193-S208, Aug 18, 2025Abstract We present an analysis of high-resolution spectra from the shock-heated plasmas in SN 1987A, based on an observation using the Resolve instrument onboard the X-Ray Imaging and Spectroscopy Mission (XRISM). The 1.7–10 keV Resolve spectra are accurately represented by a single-component, plane-parallel shock plasma model, with a temperature of $2.84_{-0.08}^{+0.09}$ keV and an ionization parameter of $2.64_{-0.45}^{+0.58}$ × $10^{11}\,\,{\rm s\,\, cm}^{-3}$. The Resolve spectra are also well reproduced by the 3D magneto-hydrodynamic simulation presented by Orlando et al. (2020, A&A, 636, A22) suggesting substantial contribution from the ejecta. The metal abundances obtained with Resolve align with the Large Magellanic Cloud value, indicating that the X-rays in 2024 originate from “non-metal-rich” shock-heated ejecta and the reverse shock has not reached the inner metal-rich region of ejecta. Doppler widths of the atomic lines from Si, S, and Fe correspond to velocities of 1500–1700 km s$^{-1}$, where the thermal broadening effects in this non-metal-rich plasma are negligible. Therefore, the line broadening seen in Resolve spectra is determined by the large bulk motion of ejecta. For reference, we determined a $90\%$ upper limit on non-thermal emission from a pulsar wind nebula at $4.3 \times 10^{-13}$ erg cm$^{-2}$ s$^{-1}$ in the 2–10 keV range, aligning with NuSTAR findings by Greco et al. (2022, ApJ, 931, 132). Additionally, we searched for the $^{44}$Sc K line feature and found a $1\sigma$ upper limit of $1.0 \times 10^{-6}$ photons cm$^{-2}$ s$^{-1}$, which translates to an initial $^{44}$Ti mass of approximately $2 \times 10^{-4}\, M_{\odot }$, consistent with previous X-ray to soft gamma-ray observations (Boggs et al. 2015, Science, 348, 670; Grebenev et al. 2012, Nature, 490, 373; Leising 2006, ApJ, 651, 1019).
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The Astrophysical Journal Letters, 988(2) L58-L58, Jul 28, 2025 Peer-reviewed
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The Astrophysical Journal Letters, 985(1) L20-L20, May 19, 2025 Peer-reviewed
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Nature, 641(8065) 1132-1136, May 14, 2025 Peer-reviewed
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The Astrophysical Journal Letters, 982(1) L5-L5, Mar 12, 2025 Peer-reviewed
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Nature, 638(8050) 365-369, Feb 12, 2025 Peer-reviewed
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Publications of the Astronomical Society of Japan, 77(1) L1-L8, Dec 26, 2024 Peer-reviewed
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The Astrophysical Journal Letters, 977(2) L34-L34, Dec 11, 2024 Peer-reviewedAbstract The X-ray binary system Cygnus X-3 (4U 2030+40, V1521 Cyg) is luminous but enigmatic owing to the high intervening absorption. High-resolution X-ray spectroscopy uniquely probes the dynamics of the photoionized gas in the system. In this Letter, we report on an observation of Cyg X-3 with the XRISM/Resolve spectrometer, which provides unprecedented spectral resolution and sensitivity in the 2–10 keV band. We detect multiple kinematic and ionization components in absorption and emission whose superposition leads to complex line profiles, including strong P Cygni profiles on resonance lines. The prominent Fe xxv Heα and Fe xxvi Lyα emission complexes are clearly resolved into their characteristic fine-structure transitions. Self-consistent photoionization modeling allows us to disentangle the absorption and emission components and measure the Doppler velocity of these components as a function of binary orbital phase. We find a significantly higher velocity amplitude for the emission lines than for the absorption lines. The absorption lines generally appear blueshifted by ∼−500–600 km s−1. We show that the wind decomposes naturally into a relatively smooth and large-scale component, perhaps associated with the background wind itself, plus a turbulent, denser structure located close to the compact object in its orbit.
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Publications of the Astronomical Society of Japan, 76(6) 1186-1201, Oct 10, 2024 Peer-reviewed
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The Astrophysical Journal Letters, 973(1) L25-L25, Sep 1, 2024 Peer-reviewed
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SPIE Proceedings, 13093 130931G-130931G, Aug 21, 2024
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Meeting Abstracts of the Physical Society of Japan, 79.2 711-711, 2024
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SPIE Proceedings, 12679 126791B-126791B, Oct 5, 2023
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SPIE Proceedings, 12181 1218122-1218122, Aug 31, 2022
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SPIE Proceedings, 12181 1218171-1218171, Aug 31, 2022
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SPIE Proceedings, 11444 114442X-114442X, Jan 4, 2021
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SPIE Proceedings, 11444 114442X-114442X, Dec 30, 2020
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SPIE Proceedings, 11444 144422-144422, Dec 13, 2020
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Publications of the Astronomical Society of Japan, 70(6) 113-113, Nov 9, 2018 Peer-reviewed
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Publications of the Astronomical Society of Japan, 70(3) 113-113, Apr 3, 2018 Peer-reviewed
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Journal of Astronomical Telescopes, Instruments, and Systems, 4(2) 021402-021402, Apr, 2018 Peer-reviewed
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Journal of Astronomical Telescopes, Instruments, and Systems, 4(02) 021407-021407, Mar 19, 2018 Peer-reviewed
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Publications of the Astronomical Society of Japan, 70(2) 11-11, Mar 1, 2018 Peer-reviewed
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Publications of the Astronomical Society of Japan, 70(2) 16-16, Mar 1, 2018 Peer-reviewed
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Publications of the Astronomical Society of Japan, 70(2) 17-17, Mar 1, 2018 Peer-reviewed
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Publications of the Astronomical Society of Japan, 70(2) 13-13, Mar 1, 2018 Peer-reviewed
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Publications of the Astronomical Society of Japan, 70(2) 9-9, Mar 1, 2018 Peer-reviewed
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Publications of the Astronomical Society of Japan, 70(2) 10-10, Mar 1, 2018 Peer-reviewed
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Publications of the Astronomical Society of Japan, 70(2) 15-15, Mar 1, 2018 Peer-reviewed
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Publications of the Astronomical Society of Japan, 70(2) 14-14, Mar 1, 2018 Peer-reviewed
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 70(2) 19-19, Mar, 2018 Peer-reviewed
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 70(2) 12-12, Mar, 2018 Peer-reviewed
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 70(2) 21-21, Mar, 2018 Peer-reviewed
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Journal of Astronomical Telescopes, Instruments, and Systems, 4(1) 011212-011212, Feb 28, 2018 Peer-reviewed
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Journal of Astronomical Telescopes, Instruments, and Systems, 4(1) 011210-011210, Jan 27, 2018 Peer-reviewed
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Journal of Astronomical Telescopes, Instruments, and Systems, 4(1) 011209-011209, Jan 22, 2018 Peer-reviewed
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SPIE Proceedings, 10699 1069922-1069922, Jan 1, 2018
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NATURE, 551(7681) 478-480, Nov, 2017 Peer-reviewed
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ASTROPHYSICAL JOURNAL LETTERS, 837(1) L15-L15, Mar, 2017 Peer-reviewed
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SPIE Proceedings, 10399 103990R-103990R, 2017
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SPIE Proceedings, 9905 99053U-99053U, Jul 26, 2016
Misc.
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大気球シンポジウム: 2020年度 = Balloon Symposium: 2020, Nov, 2020大気球シンポジウム 2020年度（2020年11月5-6日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)）, 相模原市, 神奈川県 Balloon Symposium 2020 (November 5-6, 2020. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)), Sagamihara, Kanagawa Japan 著者人数: 67名 資料番号: SA6000151012 レポート番号: isas20-sbs-012
Presentations
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大気球シンポジウム: 2024年度, Oct, 2024, 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)レポート番号: isas24-sbs-008
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日本物理学会講演概要集(CD-ROM), 2024
Teaching Experience
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物理学 (藤田保健衛生大学)
Professional Memberships
1Research Projects
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2023 - Mar, 2027
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2018 - Mar, 2022