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22 October 2015

Magneticum Pathfinder: Evolution of the universe in an unmatched precision

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, theoretical astrophysicists carry out cosmological simulations. They transform their 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.

A group of theoretical astrophysicists from the LMU led by Klaus Dolag has now, as part of the Magneticum Pathfinder project, 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 - the dark energy, the dark matter and the visible matter.

The scientists incorporated a variety of physical processes in the calculations, including 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 massive amounts of energy into the universe.

The most comprehensive simulation covers the spatial area of a cube with a box size of 12.5 billion light years. This tremendous large section of the universe was never part of a simulation 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.

For the first time, these numerous characteristics make it possible to compare a cosmological simulation in detail with large-scale astronomical surveys. "Astronomical surveys from space telescopes like Planck or Hubble observe a large segment of the visible universe while sophisticated simulations so far could only model very small parts of the universe, making a direct comparison virtually impossible," says Klaus Dolag. "Thus, Magneticum Pathfinder marks the beginning of a new era in computer-based cosmology."