Masao Mori, Astrophysics Group, University of Tsukuba

Jul. 11, 2025
As part of the Undergraduate Research Experience Seminar, students visited the PEGASUS supercomputer, located in the annex of the Center for Computational Sciences at the University of Tsukuba. PEGASUS consists of 150 compute nodes equipped with GPU accelerators, each achieving a theoretical peak performance of 51 teraflops in double-precision floating-point operations. The system’s total theoretical peak performance reaches 8.1 petaflops. In our simulations of galaxy mergers, self-gravity calculations are accelerated using GPUs to enhance computational efficiency.
Jul. 2, 2025
Akifumi Takayama, a first-year master’s student, presented his study “Galaxy Collisions and Activity of Supermassive Black Holes” at the 8th Supermassive Black Hole Research Promotion Meeting held at the University of Tsukuba.
Jun. 24, 2025
Yuka Kaneda, a third-year Ph.D. student, visited Prof. Andrea Ferrara at Scuola Normale Superiore in Pisa, Italy, where she presented a seminar on our latest research findings.
Jun. 23, 2025
A joint research meeting was held at the University of Tokyo's Kashiwa Campus with Yohei Miki, Misa Yamaguchi (1st-yr, Ph.D. student), Akifumi Takayama (1st-yr, Master's student), and Yoshitomo Takahashi (1st-yr, Master's student). Following the meeting, we visited the supercomputer MIYABI, a collaborative development by the University of Tsukuba and the University of Tokyo.

MIYABI recorded 46.80 PFLOPS on the TOP500 supercomputer performance ranking, making it the second-fastest research system in Japan, following RIKEN’s Fugaku. It plays a crucial role in our group’s investigations of galaxy evolution, black hole activity, and dark matter halos.
Jun. 22, 2025
As a recreational event, we enjoyed a sport climbing session for the first time in a while. With the participation of new members, it was a wonderful opportunity to strengthen ties not only within our team but also with colleagues from the broader theoretical astrophysics group.

A total of 11 members joined — six with prior experience and five trying it for the first time. In a friendly and supportive atmosphere, we challenged both bouldering and top-rope routes. Arriving at the climbing gym around noon, we ended up staying past 7 p.m., fully absorbed in the experience.
Jun. 16–20, 2025
Yuka Kaneda (3rd-yr, Ph.D. student) delivered a presentation on our research findings at the international conference “Dancing in the Dark: When Galaxies Shape Galaxies,” held in Sexten, Italy.
May 31–Jun. 4, 2025
We visited Zhejiang University (Hangzhou, China) to conduct collaborative research discussions with Dr Go Ogiya (Ph.D. 2014), focusing on recent progress and future plans.

The visit to Zhejiang University—surrounded by natural beauty and an expansive campus—was a highly valuable and stimulating experience. Dr. Go Ogiya, our first doctoral graduate, is currently serving as a tenure-track professor at the university. A highlight of the visit was the engaging research presentations and discussions with his graduate students, Junnan Shen and Zhihao Yin (2nd-yr, Master's student).
May 30, 2025
Misa Yamaguchi (1st-yr, Ph.D. student) has been awarded a fellowship under the JST Next Generation Researcher Challenging Research Program (SPRING). She will receive financial support for both her research and living expenses. Congratulations!
May 26–30, 2025
I participated in the international conference “Expanding the Boundaries of Dark Matter Halo” held at Shanghai Jiao Tong University, [Program], where Michi Shinozaki (1st-yr, Master's student) presented our joint work with Yuka Kaneda (3rd-yr, Ph.D. student) and Kohei Hayashi (Sendai KOSEN) titled “Understanding the Cusp-Core Transition and Characteristic Radius in Dark Matter Halos.” [Video Presentation]
May 26–30, 2025
Yuka Kaneda (3rd-yr, Ph.D. student) delivered a presentation titled “Split Stellar Streams as a Detector of Dark Satellites and Wandering Black Holes” at the international workshop “Galaxy Formation + AGORA in Asia 2025,” held at Osaka University’s Nakanoshima Center.
May 24, 2025
The paper titled “Simultaneous Formation of the Andromeda Giant Southern Stream and the Substructures in the Andromeda Halo,” co-authored by Misa Yamaguchi (1st-yr, Ph.D. student), Takanobu Kirihara (Kitami Institute of Technology), Yohei Miki (University of Tokyo), Itsuki Ogami (NAOJ), Masashi Chiba (Tohoku University), Yutaka Komiyama (Hosei University), and Mikito Tanaka (Hosei University), has been published in PASJ. [PASJ]
May 21, 2025
The team grew to 13 members in 2025, and although a bit late, we finally had a welcome party to celebrate the new arrivals.
May 14–16, 2025
At the “Bigdata Astronomy 2025” workshop held at the University of Tsukuba, Yuka Kaneda (3rd-yr, Ph.D. student) presented her work titled “Estimating Dark Matter Halo Density Profiles from Stellar Streams Using Convolutional Neural Networks” and Misa Yamaguchi (1st-yr, Ph.D. student) presented her research titled “Simultaneous Formation of the Four Substructures in the Andromeda Halo.”
May 12, 2025
Our proposed project “Galaxy Collisions and the Evolution of the Galactic Habitable Zone” has been accepted as a 2025 NAOJ Astrobiology Center Project. All formal procedures have been completed.
May 11, 2025
The annual joint BBQ of the theoretical and observational astrophysics groups at the University of Tsukuba was held at "Yukari-no-Mori."
May 1, 2025
In 2025, I started a new challenge in sports science research. Building on our expertise in astrophysical fluid dynamics, I am exploring its potential applications to athletic performance and biomechanics.
Apr. 28, 2025
One of our undergraduate thesis students has chosen to pursue research through analytical approaches rather than numerical simulations. While this path may not produce the visually striking figures often seen in simulation work, it offers a powerful way to understand complex cosmic phenomena by tracing them back to fundamental physical processes — and can lead to deeply meaningful insights.
Apr. 21, 2025
All first-year students have now finalised their research topics. In our group, we emphasise thorough discussions to ensure that each topic is well-matched to the student’s interests and abilities.
Apr. 1, 2025
With the beginning of the new academic year, we have welcomed the following individuals to our team: as first-year students in the Master’s Programme — Kanta Aimoto, Mayuka Oda, Michi Shinozaki, Yoshitomo Takahashi, and Akifumi Takayama; and as undergraduate thesis students — Maria Arima, Taisei Nomura, and Kenta Hagiwara.

Mar. 27, 2025
A co-authored paper by Misa Yamaguchi (2nd-yr, Master's student), Takanobu Kirihara (Kitami Institute of Technology), Yohei Miki (University of Tokyo), Itsuki Ogami (SOKENDAI), Masashi Chiba (Tohoku University), Yutaka Komiyama (Hosei University), and Mikito Tanaka (Hosei University), entitled “Simultaneous Formation of the Andromeda Giant Southern Stream and the Substructures in the Andromeda Halo,” has been accepted for publication in PASJ.
[arXiv:2503.21217]
Mar. 25, 2025
Michi Shinozaki, a fourth-year undergraduate student in Physics, has been awarded the prestigious President's Award in recognition of her outstanding thesis, “Critical Conditions for the Cusp–Core Transition in Dark Matter Halos.” Congratulations on her exceptional achievements!
Mar. 25, 2025
This academic year, we celebrated the graduation of five students from our group.
Mar. 17–20, 2025
At the Spring Meeting of the Astronomical Society of Japan, held in Mito city, recent research results were presented by Yuka Kaneda (2nd-yr, Ph.D. student), Misa Yamaguchi (2nd-yr, Master's student), and Michi Shinozaki (4th-year undergraduate student).
Feb. 14, 2025
The Master’s thesis presentations by Misa Yamaguchi and Takuhiro Yuasa were successfully conducted. Both students were commended for the quality of their research and presentations.
Feb. 7, 2025
Our team produced the third instalment of the “Frontline Research” series, entitled “Is the Cold Dark Matter Hypothesis Correct? Searching for Dark Matter Halos through Stellar Stream Signatures.”

According to the cold dark matter hypothesis, which is one of the leading theories regarding the nature of dark matter, large galaxies such as the Milky Way and Andromeda are surrounded by numerous ‘dark satellites’—structures comparable in size to small galaxies. However, these dark satellites have yet to be directly observed. In this work, we propose a new method for detecting such invisible structures by analysing the dynamical signatures—specifically disruptions—in stellar streams.
Feb. 5, 2025
Michi Shinozaki received the Best Presentation Award at the undergraduate thesis presentations for her work entitled “Critical Conditions for the Cusp–Core Transition in Dark Matter Halos.” Congratulations to her on this accomplishment!
Feb. 5, 2025
The undergraduate thesis presentations by Kanta Aimoto, Michi Shinozaki, Akifumi Takayama, and Ryuoh Fujinomaki were successfully completed.
Feb. 4, 2025
Our team released the second instalment of the “Frontline Research” series: “Dark Matter and the Tears of Andromeda: Galactic Formation and Evolution.”

In the neighbouring Andromeda Galaxy, a galactic collision is underway. The resulting stellar stream, known as the "Andromeda Giant Southern Stream," provides valuable insight into the role of dark matter in shaping galactic structure.
Jan. 27, 2025
Our team released the first instalment of the “Frontline Research” series: “Do Stars Form in the Intergalactic Spaces? Formation of Dwarf Galaxies and Young Star Clusters in the M81 Group.”

In the M81 Group, approximately 12 million light-years away, young stellar systems have been discovered between galaxies. This study explores whether these systems were stripped from spiral galaxies or formed spontaneously in intergalactic space.
Jan. 16, 2025
We marked the beginning of 2025 with a festive gathering, celebrating the New Year and Dr Yohei Miki’s new academic position.
Jan. 10, 2025
A co-authored paper by Misa Yamaguchi (2nd-yr, Master's student), Takanobu Kirihara, Yohei Miki, Itsuki Ogami, Masashi Chiba, Yutaka Komiyama, and Mikito Tanaka, entitled “Simultaneous Formation of the Andromeda Giant Southern Stream and Eastern Extent,” has been submitted.
Dec. 26, 2024
A new paper co-authored by Yuka Kaneda (2nd-yr, Ph.D. student), Yohei Miki, Takanobu Kirihara, and Andreas Burkert (University of Munich) has been submitted.
Dec. 19, 2024
Preliminary reviews of undergraduate theses were held for the following students with successful outcomes: Kanta Aimoto (Dec. 11), Michi Shinozaki (Dec. 12), and Akifumi Takayama and Ryuoh Fujinomaki (Dec. 19).
Dec. 9, 2024
A co-authored paper with Itsuki Ogami (SOKENDAI), entitled “The Structure of the Stellar Halo of the Andromeda Galaxy Explored with the NB515 for Subaru/HSC. I: New Insights on the Stellar Halo up to 120 kpc,” has been published in the *Monthly Notices of the Royal Astronomical Society*.
Dec. 4, 2024
The interim thesis presentation by Takuhiro Yuasa (2nd-yr, Master's student) was successfully conducted.
Nov. 27, 2024
The interim thesis presentation by Misa Yamaguchi (2nd-yr, Master's student) was successfully conducted.
Nov. 5–8, 2024
At the “Workshop-Style School on Dark Matter and Its Exploration in the Universe,” held at Yokohama National University, Yuka Kaneda (2nd-yr, Ph.D. student) and Michi Shinozaki (4th-yr, Undergraduate student) presented their latest research. The lecture programme covered a broad range of topics, including cosmic-ray propagation, dark matter structure formation, relic abundance, and particle models of dark matter.
Nov. 1, 2024
Dr. Yohei Miki (Ph.D., 2014) has been appointed Associate Professor at the Information Technology Center of the University of Tokyo. Congratulations to him on this significant achievement.
Oct. 29, 2024
A paper co-authored with Yudai Kazuno (Master’s graduate, 2023), entitled “Cosmological Evolution of Dark Matter Subhaloes under Tidal Stripping by Growing Milky Way-like Galaxies,” has been accepted for publication in PASJ. This study analyses cosmological simulation data to investigate the mass evolution and dynamical responses of subhaloes embedded within Milky Way-scale dark matter halos.
Oct. 28 – Nov. 1, 2024
At the Kashiwa-no-ha Dark Matter and Cosmology Symposium, held at the University of Tokyo’s Kashiwa Campus, Yuka Kaneda (2nd-yr, Ph.D. student) presented a talk on the formation of parallel stellar streams triggered by encounters with dark matter subhaloes or intermediate-mass black holes. Michi Shinozaki (4th-yr, Undergraduate student) presented a poster on the physical conditions required for cusp–core transitions in dark matter halos and engaged in extensive discussions with fellow participants.
Oct. 18–19, 2024
At the 2024 Star Formation Workshop held at the University of Tsukuba, Yuka Kaneda (2nd-yr, Ph.D. student), Misa Yamaguchi (2nd-yr, Master's student), Takuhiro Yuasa (2nd-yr, Master's student), Kanta Aimoto (4th-yr, Undergraduate student), Michi Shinozaki (4th-yr, Undergraduate student), and Akifumi Takayama (4th-yr, Undergraduate student) presented their latest research findings.
Oct. 18–19, 2024
At the 2024 Star Formation Workshop held at the University of Tsukuba, Yuka Kaneda (2nd-yr, Ph.D. student), Misa Yamaguchi (2nd-yr, Master's student), Takuhiro Yuasa (2nd-yr, Master's student), Kanta Aimoto (4th-yr, Undergraduate student), Michi Shinozaki (4th-yr, Undergraduate student), and Akifumi Takayama (4th-yr, Undergraduate student) presented their latest research findings.
Oct. 10, 2024
A co-authored paper with Itsuki Ogami (SOKENDAI), titled “The Structure of the Stellar Halo of the Andromeda Galaxy Explored with the NB515 for Subaru/HSC. I: New Insights on the Stellar Halo up to 120 kpc,” has been accepted for publication in Monthly Notices of the Royal Astronomical Society. The study presents detailed observational evidence of past galactic collisions in the halo of M31. This international collaboration includes researchers from SOKENDAI, NAOJ, Tohoku University, University of Tsukuba, UCLA, University of Notre Dame, Johns Hopkins University, and other institutions.
Oct. 7–8, 2024
At the international symposium “16th Symposium on Discovery, Fusion, Creation of New Knowledge by Multidisciplinary Computational Sciences,” held at the Tsukuba International Congress Center, our team presented recent research results. Michi Shinozaki (4th-yr, Undergraduate student) delivered a presentation on the physical conditions required for cusp–core transitions in dark matter halos.
Sep. 26–27, 2024
Misa Yamaguchi (2nd-yr, Master's student) and I participated in the workshop “The Violent Universe,” held at the National Astronomical Observatory of Japan, where recent research findings were presented.
Sep. 11–13, 2024
At the Autumn Meeting of the Astronomical Society of Japan 2024, held at Kwansei Gakuin University (Sanda Campus, Hyogo), Misa Yamaguchi (2nd-yr, Master's student) and I presented the latest research on the Andromeda Giant Stream and dark matter halos. In conjunction with the conference, a kickoff meeting was also held with collaborators from Tohoku University, NAOJ, Hosei University, and the University of Tokyo to launch a new joint research project.
Aug. 30, 2024
A co-authored paper with Yudai Kazuno (MSc, 2023), titled “Cosmological Evolution of Dark Matter Subhaloes under Tidal Stripping by Growing Milky Way-like Galaxies,” has been submitted to Publications of the Astronomical Society of Japan.
Aug. 30, 2024
Dr. Koki Otaki (PhD, 2024, now at Kagoshima University) departed for Rome to begin his new position as a research fellow at Sapienza University. Members of my team, past and present, gathered in Tsukuba to hold a farewell event in his honour.
Aug. 5, 2024
A project meeting for a new collaborative study was held at the University of Tokyo Kashiwa Campus.
Jul. 30, 2024
A co-authored paper by Takuhiro Yuasa (2nd-yr, Master's student) and Yohei Miki (University of Tokyo), titled “Novel Individual Timestep Integrator with Symplectic Property using Hamiltonian Splitting for SPH,” has been submitted to The Astrophysical Journal.
Jul. 25, 2024
The University of Tsukuba held its annual Open Campus. Our booth welcomed approximately 150 visitors, who explored recent research highlights, including galaxy collision simulations and current developments in astrophysical research.
Jul. 19, 2024
We welcomed Dr. Sakurako Okamoto from the NAOJ Hawaii Observatory for a collaborative research meeting. A new project has been launched, and we look forward to its future developments.
Jul. 16, 2024
A co-authored paper by Koki Otaki (postdoctoral fellow at Kagoshima University), Yohei Miki (University of Tokyo), and Daisuke Takahashi (University of Tsukuba), titled “Accelerated Hermite Integrator for Orbital Integration with OpenACC,” has been submitted to Computer Physics Communications. The paper analyses the performance of an N-body simulation code that implements Hermite integration accelerated using GPUs via OpenACC.
Jul. 15, 2024
A co-authored paper by Yuka Kaneda (2nd-yr, Ph.D. student), titled “A Universal Scaling Relation Incorporating the Cusp-to-Core Transition of Dark Matter Haloes,” has been accepted for publication in Publications of the Astronomical Society of Japan. The study elucidates the physical origin of unusual scaling relations observed in dark matter halos across galaxies and galaxy clusters, and discusses their connection to the cusp–core problem within the cold dark matter paradigm.
[arXiv:2407.03614]
Jul. 8, 2024
A co-authored paper by Yuka Kaneda (2nd-yr, Ph.D. student), currently under review at PASJ, has been made publicly available on arXiv: “A Universal Scaling Relation Incorporating the Cusp-to-Core Transition of Dark Matter Haloes.”
[arXiv:2407.03614]
Jul. 7, 2024
A co-authored paper by Takuhiro Yuasa (2nd-yr, Master's student), titled “Novel Hydrodynamic Schemes Capturing Shocks and Contact Discontinuities and Comparison Study with Existing Methods,” has been published in New Astronomy. The paper presents a new SPH method developed to resolve shock waves and contact discontinuities in compressible hydrodynamic simulations.
[New Astronomy, arXiv:2312.03224v3]
Jul. 2, 2024
An interview with Yuka Kaneda (2nd-yr, Master's student as of March 2023), recorded during the IAU Symposium “Dynamical Masses of Local Group Galaxies” in Potsdam, has been published on YouTube (8:35–10:14). In the video, she offers an accessible explanation of the cusp–core problem in cold dark matter halos, intended for the general public.
Jun. 29, 2024
Members of SCUTA (Space Theory and Climbing Club, University of Tsukuba) challenged lead climbing together.
May 20, 2024
Misa Yamaguchi (2nd-yr, Master's student)’s travel report, funded by the Hayakawa Yukio Foundation of the Astronomical Society of Japan, was published in the June issue of Tenmon Geppou.
May 12, 2024
A joint welcome party for new students of the Theoretical and Observational Astrophysics Groups at the University of Tsukuba was held at Yukari-no-Mori. Seven members from Team Mori participated, enjoying BBQ and fostering interaction with students from observational and other theoretical groups.
Apr. 22, 2024
Four new undergraduate research students have joined our group: Kanta Aimoto, Michi Shinozaki, Akifumi Takayama, and Ryuoh Fujinomaki.
Apr. 20, 2024
Koki Otaki (Ph.D. 2024)’s travel report, supported by the Hayakawa Yukio Foundation of the Astronomical Society of Japan, was published in the May issue of Tenmon Geppou.
Apr. 1, 2024
We welcomed Taisei Takeuchi as a new first-year student in the Master’s Programme. In addition, our 2017 graduate Dr. Takanobu Kirihara has been appointed Associate Professor at the Kitami Institute of Technology. Congratulations!

Mar. 31, 2024
Kazuma Koyata (2nd-yr, Master's student) has entered a private company, and Koki Otaki (3rd-yr, Ph.D. student) has moved to Kagoshima University as a postdoctoral researcher. He is also scheduled to transfer to the University of Rome as a research fellow once preparations are complete.
Mar. 26, 2024
After a two-week stay in Germany beginning on Mar. 12, I returned to Japan today. During the visit, I held collaborative discussions with Prof. Andreas Burkert at the Max Planck Institute for Extraterrestrial Physics near Munich and Prof. Andreas Koch at the Astronomisches Rechen-Institut, Heidelberg University.
Mar. 12, 2024
From today, I will be staying in Germany for approximately two weeks to hold research meetings at the Max Planck Institute for Extraterrestrial Physics, the University Observatory of Ludwig Maximilian University of Munich, and the Astronomisches Rechen-Institut at Heidelberg University.
Mar. 11, 2024
We are participating in the Spring 2024 Annual Meeting of the Astronomical Society of Japan, held for two days at the University of Tokyo (Hongo Campus). In the special session titled “Galaxy and Galactic Evolution Unveiled by Subaru PFS,” research presentations are being given by Masao Mori, Koki Otaki (3rd-yr, Ph.D. student), Yuka Kaneda (1st-yr, Ph.D. student), and Misa Yamaguchi (1st-yr, Master's student).
Mar. 9, 2024
Yuka Kaneda (1st-yr, Ph.D. student) and I participated in the satellite workshop “Galaxy and Galactic Evolution Unveiled by Subaru PFS,” held at the National Astronomical Observatory of Japan.
Mar. 1, 2024
We attended the international workshop “Dark Matter in the Universe: The Present and Future of Galactic Archaeology and Near-field Cosmology,” held over three days at the Matsushima Century Hotel (Miyagi Prefecture). Presentations were given by Masao Mori, Koki Otaki (3rd-yr, Ph.D. student), Yuka Kaneda (1st-yr, Ph.D. student), and Misa Yamaguchi (1st-yr, Master's student).
Feb. 21, 2024
Koki Otaki (3rd-yr, Ph.D. student) successfully passed the defence of his doctoral thesis titled “Formation of Dwarf Galaxies Induced by Dark Matter Subhalo Collisions.”
Feb. 15, 2024
A paper by Takuhiro Yuasa (1st-yr, Master's student), titled “Novel hydrodynamic schemes capturing shocks and contact discontinuities and comparison study with existing methods,” has been accepted for publication in *New Astronomy*. [arXiv:2312.03224]
Feb. 15, 2024
Kazuma Koyata (2nd-yr, Master's student) successfully passed the public defence of his master’s thesis titled “Hydrodynamic Interactions in Collisions Between Dwarf Galaxies and Galactic Discs.”
Jan. 31, 2024
Taisei Takeuchi (4th-yr, Undergraduate student) successfully passed the public defence of his bachelor’s thesis titled “Toward Understanding Galaxy Collisions and Hydrodynamic Interactions.”

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