by Klaus Dolag
In cooperation with experts of the Excellence Cluster Universe's datacentre C2PAP and of the Leibniz Supercomputing Centre, the world's most elaborated cosmological simulation of the evolution of our universe was accomplished. The most comprehensive simulation within the Magneticum Pathfinder project pursues the development of a record number of 180 billion tiny spatial elements in a previously unreached spatial area of 12.5 billion light years. For the first time, a hydrodynamic cosmological simulation is large enough to be directly compared with large-scale astronomical surveys.
Within modern cosmology, the Big Bang marks the beginning of the universe and the creation of matter, space and time about 13.8 billion years ago. Since then, the visible structures of the cosmos have developed: billions of galaxies which bind gas, dust, stars and planets with gravity and host supermassive black holes in their centres. But how could these visible structures have formed from the universe's initial conditions?
To answer this question, we are carrying out cosmological simulations. They transform our knowledge about the physical processes forming our universe into mathematical models and simulate the evolution of our universe on high-performance computers over billions of years.
As part of the Magneticum Pathfinder project, we performed a new, unique hydrodynamic simulation of the large-scale distribution of the universe's visible matter. The most recent results regarding the three most important cosmic ingredients of the universe are taken into account: dark energy, dark matter and visible matter.
We incorporated a variety of physical processes in the calculations, among them three that are considered particularly important for the development of the visible universe: first, the condensation of matter into stars, second, their further evolution when the surrounding matter is heated by stellar winds and supernova explosions and enriched with chemical elements, and third, the feedback of supermassive black holes that eject enormous amounts of energy into the universe.
The most comprehensive simulation (shown in the zoom-in image) covers the spatial area of a cube with a box size of 12.5 billion light years. Such a tremendously large section of the universe was never simulated before. It was divided into a previously unattained number of 180 billion resolution elements, each representing the detailed properties of the universe and containing about 500 bytes of information.
The result of this simulation has been already used to calibrate the halo mass function (e.g. the theoretical predictions of how many objects with a certain, total mass exists in the universe at different times) and to explore the impact of the visible matter on such measurements, especially for future, high precision cosmological probes like eROSITA. Interestingly, the results from this study show that even for current observational studies like the one presented by the PLANCK satellite team, the large volume captured by the simulation allows to improve the quality of such predictions and seems to relax some tension which is present when comparing the observations from PLANCK to previous, theoretical predictions.
- Press release: Excellence Cluster Universe
- Baryon impact on the halo mass function: Fitting formulae and implications for cluster cosmology
- SZ effects in the Magneticum Pathfinder Simulation: Comparison with the Planck, SPT, and ACT results