Figure 1: Distribution of dark matter in Uchuu's snapshot Images show the dark matter cloud of the largest cluster galaxy formed by simulation at different magnifications. Credit to Tomoaki Ishiyama
Online games promise a whole new world to explore. A team of international researchers created a virtual universe and made it available to all on the cloud.
Uchuu, which means "outer space" (in Japanese), is the most accurate and realistic simulation of the universe. Uchuu's simulation is composed of 2.1 trillion particles within a computational cube that measures 9.63 billion light years to one side. This is roughly three-quarters of the distance between Earth, the nearest galaxies and the Earth. Uchuu shows the evolution of the universe at a scale and depth that was unimaginable before.
Uchuu is interested in the large-scale structure and fate of the universe. These structures can be scaled from the largest galaxies to the most massive galaxy clusters. Individual planets and stars are not resolved so you shouldn't expect to see alien civilizations in Uchuu. Uchuu is unique in that it simulates the evolution and development of matter for almost all of the 13.8 billion years of the universe's history, from the Big Bang up to the present. This is more than 30 times the time it took for animal life to emerge from the oceans of Earth.
Time evolution of dark matter structures at Uchuu. Credit: Hirotaka Nakayama and Tomoaki Ishiyama. 4D2U Project. NAOJ
Julia F. Ereza is a Ph.D student at IAA–CSIC and uses Uchuu for studying the large-scale structure and evolution of the universe. She says that Uchuu is like an "Internet of Things": We can zoom in and out on individual galaxies or the whole cluster to see the entire universe. This is an important tool in understanding the cosmos.
Uchuu was created by an international team of researchers from Japan and other countries, including Australia, Chile, France (U.S.A.), Argentina, Chile, Australia, Chile, France, Chile, France, Italy, and Chile. It was created using ATERUI II the most powerful supercomputer in the world dedicated to astronomy. Uchuu was still produced even with all the power. It took over a year. Tomoaki Ishiyama (a Chiba University associate professor) developed the code that generated Uchuu. He explained, "To make Uchuu we used... all 40.200 processors (CPU Cores). These CPU cores are only available for 48 hours per month." 20 million supercomputer hours were used, and 3 Petabytes worth of data were created, which is equivalent to 894,784,853 photos from a 12-megapixel mobile phone.
The research team used high-performance computing techniques to compress the information about the formation and evolution dark matter haloes within the Uchuu simulation into an 100-terabyte catalog. The catalog is now accessible to all users on the cloud in an easily-useable format thanks to the computational infrastructure skun6 at the Instituto de Astrofsica de Andaluca, the RedIRIS group and the Galician Supercomputing Center. Future data releases will include catalogs for virtual galaxies as well as gravitational lensing maps.
This simulation predicts the time evolution of the number and types of halos within each mass range. Horizontal bars extending from each triangle and circle represent the range of halo mass sizes. The vertical axis represents the number of haloes in a cube measuring 9.6 billion light years on each side. The categories of objects found within haloes with that mass are represented by the gradient bars at their top. According to the Uchuu simulation, many haloes of similar mass as our galaxy's were formed around 13 billion years ago. Credit to Tomoaki Ishiyama
Uchuu's Big Data science products will assist astronomers in learning how to interpret Big Data galaxy survey data expected in the future from facilities such as the Subaru Telescope or the ESA Euclid satellite mission.
These results were published by Ishiyama and colleagues. "The Uchuu Simulations: Data Release 1 & Dark Matter Halo Concentrations" is available in the September 2021 issue of Monthly Notices of The Royal Astronomical Society.
Center for Computational Astrophysics
