11Japan Academy Prize to:Satoshi Miyazaki
Director and Professor,
Subaru Telescope, National
Astronomical Observatory of JapanandMasamune Oguri
Professor,
Center for Frontier Science,
Chiba University

for “Pioneering and Promoting Cosmological Research Using Gravitational Lensing
Eﬀects” (Joint Research)

Outline of the work:
The existence of unknown dark matter and dark energy was discovered through various
astronomical observations over the last half-century. However, understanding the nature of dark
matter and dark energy remains a major challenge in modern physics and cosmology. Althoughinvisible, dark matter is detectable through its gravitational eﬀects. The total mass of dark matterassociated with galaxies and galaxy clusters is approximately five times that of stars and gases,
and the dark matter is thought to have played a key role in forming the large-scale structure of theuniverse. No candidate such as nonluminous low-mass objects, primordial black holes, axions,or fuzzy dark matter has been yet identified as dark matter despite various observational andexperimental searches.
The gravitational lensing eﬀect of a massive cloud of dark matter influences light fromsources behind, resulting in multiple images as well as image brightness enhancement and distortion. Multiple images of a quasar owing to a strong lensing eﬀect were first detected in 1979,
sparking interest in observing weak lensing eﬀects to evaluate the distribution of dark matter.
In the 1990s, Dr. Satoshi Miyazaki led the development of Suprime-Cam, a wide-field CCD
camera at the prime focus of the Subaru Telescope. He analyzed the first light images obtainedin 2000 to evaluate subtle distortions in the images of distant galaxies behind a galaxy cluster. In
2002, he demonstrated the feasibility of retrieving the distribution of dark matter by solving the“inverse problem” of weak lensing eﬀects. The retrieved distribution corresponds well with thedistribution of galaxy clusters identified through X-ray and optical observations.

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Building upon this success, Dr. Miyazaki proposed the construction of a larger camera for
the Subaru Telescope: Hyper Suprime-Cam (HSC), featuring 106 CCD devices. He completed
the construction in 2012 and led an international team in utilizing it to map the deep universe.
This endeavor spanned 330 nights over seven years, commencing in 2014. With its wide fieldof view as well as excellent image quality and sensitivity, HSC is currently the world’s largest
camera that is employed in surveying the universe. HSC image data are openly available to thepublic and are utilized in various areas of astronomical research, including dark matter studies.
Dr. Masamune Oguri analyzed gravitationally lensed quasar images from the Sloan DigitalSky Survey to ascertain the distribution of dark matter in lensing galaxies. Additionally, heexamined images captured by the Subaru Telescope and Hubble Space Telescope that include
the eﬀects of gravitational lensing for diverse investigations. He refined Dr. Miyazaki’s weaklensing study, yielding the three-dimensional spatial distribution of dark matter and its evolution
over billions of years. Furthermore, he succeeded in unveiling the phenomenon of dark mattercoalescence and aggregation. Moreover, Dr. Oguri and his collaborators indicated that the modelof the expanding universe derived from the distribution of numerous galaxies at a redshift ofapproximately 1 may be inconsistent with the model obtained through analysis of the cosmic
background radiation at a redshift of 1000.
Dr. Oguri further predicted that a newly found distant supernova would appear as multiple,
time-delayed images owing to gravitational lensing eﬀects; this was confirmed one year later. He
made another notable discovery when he observed a lone, distant primordial star whose brightness was substantially intensified by an ultrastrong gravitational lensing eﬀect while traversing
the causal line of the lensing eﬀect. This demonstrated that by carefully probing gravitational
lensing eﬀects we have chances to witness distant, faint objects that would never be visible.
Many of the abovementioned scientific achievements are recorded in the outstanding images
obtained using HSC, which were developed and well-utilized by Dr. Miyazaki. The quality andquantity of HSC data are globally unparalleled. The observations using HSC are also expected tobe jointly coordinated with those by the Euclid Space Telescope Project in Europe and the Rubin
Telescope Project in the United States to evaluate the accelerating expansion of the universe. By
conducting creative and precise analyses of valuable observational data from the perspective ofgravitational lensing, Dr. Oguri demonstrated the possibility of directly observing the stars in theearly universe a feat beyond the sensitivity of existing large telescopes by skillfully exploiting
the amplification function of gravitational lensing.
Dr. Satoshi Miyazaki and Dr. Masamune Oguri, who led a series of pioneering investigations in gravitational lensing astronomy, are worthy of the Japan Academy Prize.

List of Main Publications (Dr. Satoshi Miyazaki)
1) “Subaru Prime Focus Camera Suprime-Cam”, Miyazaki, S., Komiyama, Y., Sekiguchi,M., et al., 2002, PASJ, 54, 833–853.
2) “Searching for Dark Matter Halos in the Suprime-Cam 2 Square Degree Field”, Miyazaki,S., Hamana, T., Shimasaku, K., et al., 2002, ApJ Lett., 580, 97–100.
3) “A Subaru Weak-Lensing Survey. I. Cluster Candidates and Spectroscopic Verification”,

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Miyazaki, S., Hamana, T., Richard S. E., et al., 2007, ApJ, 669, 714–728.
4) “Properties of Weak Lensing Clusters Detected on Hyper Suprime-Cam’s 2.3 square degreefield”, Miyazaki, S., Oguri, M., Hamana, T., et al., 2015, ApJ, 807, 22–33.
5) “Hyper Suprime-Cam: System Design and Verification of Image Quality”, Miyazaki, S.,
Komiyama, Y., Kawanomoto, S., et al., 2018, PASJ, 70, S1 (1–26).
6) “The Hyper Suprime-Cam SSP Survey: Overview and Survey Design”, Aihara, H., Arimoto,N., Armstrong, R., ..., Miyazaki, S., ..., Oguri, M., et al., 2018, PASJ, 70, S4 (1-15).
7) “Two- and Three-dimensional Wide-field Weak Lensing Mass Maps from the HyperSuprime-Cam Subaru Strategic Program S16A Data”, Oguri, M., Miyazaki, S., Hikage,
C. et al., 2018, PASJ, 70, S26 (1–14).
8) “A Large Sample of Shear-selected Clusters from the Hyper Suprime-Cam Subaru Strategic
Program S16A Wide Field Mass Maps”, Miyazaki, S., Oguri, M., Hamana, T., et al., 2018,PASJ, 70, S27 (1–23).
9) “Cosmology from Cosmic Shear Power Spectra with Subaru Hyper Suprime-Cam First-YearData”, Hikage,C., Oguri, M., Hamana, T., ..., Miyazaki, S., et al., 2019, PASJ, 71, 43.
10) “Hundreds of Weak Lensing Shear-selected Clusters from the Hyper Suprime-Cam Subaru
Strategic Program S19A Data”, Oguri, M., Miyazaki, S., Li, X., et al., 2021, PASJ, 73,817–829.

List of Main Publications (Dr. Masamune Oguri)1) “Gravitational Lens Time Delays: A Statistical Assessment of Lens Model Dependences andImplications for the Global Hubble Constant”, Oguri, M., 2007, ApJ, 660, 1.
2) “Gravitationally Lensed Quasars and Supernovae in Future Wide-Field Optical Imaging Surveys”, Oguri, M. and Marshall P. J., 2010, MNRAS, 405, 2579–2593.
3) “Direct Measurement of Dark Matter Halo Ellipticity from Two-Dimensional Lensing Shear
Maps of 25 Massive Clusters”, Oguri, M., Takada, M., Okabe, N., et al., 2010, MNRAS,405, 2215–2230.
4) “Combined Strong and Weak Lensing Analysis of 28 Clusters from the Sloan Giant ArcsSurvey”, Oguri, M., Matthews, B. B., Hakon, D., et al., 2012, MNRAS, 420, 3213–3239.
5) “Detection of the Gravitational Lens Magnifying a Type Ia Supernova”, Quimby, R. M.,Oguri, M., More, A., et al., 2014, Science, 344, 396–399.
6) “Measuring the Distance-Redshift Relation with the Cross-Correlation of Gravitational
Wave Standard Sirens and Galaxies”, Oguri, M., 2016, Phys. Rev. D, 93, 083511.
7) “Eﬀect of Gravitational Lensing on the Distribution of Gravitational Waves from DistantBinary Black Hole Mergers”, Oguri, M., 2018, MNRAS, 480, 3842–3855.
8) “Understanding Caustic Crossings in Giant Arcs: Characteristic Scales, Event Rates, andConstraints on Compact Dark Matter”, Oguri, M., Diego, J. M., Kaiser, N., et al., 2018,Phys. Rev. D, 97, 023518.
9) “Cosmology from Cosmic Shear Power Spectra with Subaru Hyper Suprime-Cam First-YearData”, Hikage, C., Oguri, M., Hamana T., et al., 2019, PASJ, 71, 43.
10) “A Comprehensive Study of Galaxies at z∼9-16 Found in the Early JWST Data: Ultravio-14

let Luminosity Functions and Cosmic Star Formation History at the Preionization Epoch”,Harikane, Y., Ouchi, M., Oguri, M. et al., 2023, ApJS, 265, 5.