The largest virtual universe ever constructed has been completed by the international Euclid Consortium to support the European Space Agency’s Euclid mission, launched in 2023. The vast simulation, containing 3.4 billion galaxies, will play a crucial role in mapping the large-scale structure of the cosmos and probing the elusive nature of dark matter and dark energy, the HUN-REN Research Centre for Astronomy and Earth Sciences announced on Monday.
The newly published catalogue records over 400 properties for each galaxy and forms the basis for what is set to become the most extensive three-dimensional map of the Universe. Euclid’s space telescope, launched in June 2023, aims to chart one-third of the sky over six years, creating the largest cosmic map ever made. To prepare for this, researchers developed the so-called Flagship simulation, which includes galaxies more than 10 billion light-years away.
This synthetic dataset is essential for interpreting Euclid’s observations. It allows scientists to study the cosmic web, test the standard cosmological model, and gain insights into dark matter and dark energy. The catalogue was developed by an international team led by the Institute of Space Sciences (ICE-CSIC) and the Port d’Informació Científica (PIC), and is accessible through the CosmoHub platform.
The models were built using supercomputing resources at the University of Zurich, simulating the gravitational interactions of four trillion particles. From these, scientists identified 16 billion gravitationally bound structures, or halos, then populated them with galaxies that Euclid is expected to observe, matching them to current astronomical data.
In total, the catalogue includes detailed information on brightness, position, velocity, and shape for billions of galaxies, accurately reproducing the cosmic web, galaxy clusters, and vast empty voids. Hungarian astrophysicist András Kovács, a group leader at HUN-REN, contributed expertise on cosmic voids and gravitational lensing.
‘The Flagship universe is analyzed with the same statistical tools we use for real observations, including data imperfections. This lets us test how precisely we can map the cosmic web and ensure that Euclid’s real data will yield maximum results,’ Kovács explained.
Building the catalogue posed both scientific and technical challenges, requiring new computational methods, improved models of galaxy formation and evolution, and integration with current theories of the Universe’s dark components. As Pablo Fosalba of ICE-CSIC noted, the simulation’s greatest value lies in its wide range of galaxy properties, many of which already align closely with real observations. Researchers are only beginning to explore how powerful its predictions could be for future surveys.
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