The new simulation covers a spherical volume with a radius of 600 million light years from the Milky Way and is able to reproduce accurately all the known large-scale structures in the Local Universe.
The simulation thus confirms the critical role of dark matter in the formation of galaxies and galaxy clusters, as predicted by the standard model of cosmology. The international research team was led by the University of Helsinki and the results of the study have been published in the Monthly Notices of the Royal Astronomical Society (MNRAS) journal.
Previous simulations have typically modelled random patches of the Universe, in which case the comparison with observations can only be done in a statistical sense. In this new simulation all the simulated objects have real counterparts in the observed Local Universe, meaning that the comparison with observations is now much more straightforward.
In addition, we can directly study the formation and evolution of the known structures in the Local Universe. The production of this numerical simulation has required the use of advanced algorithms, which enables the simulation of a particular patch of the Universe based on observational inputs. The simulation contained over 130 billion dark matter particles and running the simulation required several millions of computing hours producing over 1000 Terabytes of simulation data. The simulation was performed on the DiRAC COSmology MAchine (COSMA) supercomputer, which is located at Durham University in the United Kingdom.
– It is remarkable, that the simulation is able to accurately reproduce all the known galaxy clusters, such as the Virgo, Coma and Perseus clusters, in addition to the Local Group of galaxies, which also contains the Milky Way and the Andromeda galaxy, says postdoctoral researcher Stuart McAlpine from the University of Helsinki.
– Previous simulations have only examined random patches of the Universe. They are like maps of an unfamiliar city, which can provide you with some information, but cannot be used for detailed navigation. On the other hand, Sibelius is for astronomers like a map of their hometown. It faithfully represents real structures from the Milky Way to the Coma galaxy cluster, which can really be observed, says Till Sawala from the University of Helsinki, who is also the principal investigator of the SIBELIUS project.
– These simulations are really groundbreaking, as they enable a direct comparison between the simulations and the observations, and thus provide us with the necessary tools to understand the formation and evolution of many well-known objects in the Local Universe says Peter Johansson, also from the University of Helsinki.
Dark matter and the standard model of cosmology
The simulation can be used to test the standard model of cosmology, which is supported by a plethora of observations.
– The simulations demonstrate that the currently favoured standard model of cosmology, the so called cold dark matter model, is able to give rise to all the observed galaxies in the Universe. According to this model our local patch of the Universe was formed over the past 13.7 billion years, when gas cooled inside dark matter haloes, thus forming galaxies, says McAlpine.
The now published SIBELIUS-DARK project is part of the “Simulations Beyond the Local Universe” (SIBELIUS)-project, which is also funded by the Academy of Finland. The lead author of the research article is Stuart McAlpine from the University of Helsinki. Other contributors from Helsinki include Academy Research Fellow Till Sawala and professor Peter Johansson, with the remaining authors coming from the United Kingdom, France, the Netherlands and Sweden.