The project focused on advancing the theoretical understanding of the intracluster medium (ICM) through large-scale numerical simulations and the development of new analysis tools. The core activities included the generation of high-resolution cosmological simulations of galaxy clusters, the implementation of improved numerical techniques, and the detailed analysis of turbulence, magnetic fields, and plasma processes in the ICM.
A major technical achievement was the construction of a new parent cosmological simulation covering a volume of 1 Gpc/h, from which 272 massive galaxy clusters were identified. From this sample, 24 clusters were re-simulated using high-resolution “zoom-in” techniques at IllustrisTNG300 resolution while ensuring contamination-free initial conditions. In addition, the a very massive cluster was re-simulated at IllustrisTNG100 resolution, resulting in the highest-mass, highest-resolution cosmological galaxy cluster simulation currently available with the IllustrisTNG model galaxy formation model. These simulations were performed using the AREPO2 code, enabling improved accuracy and scalability to the unprecedented numerical resolution for massive galaxy clusters.
The project also delivered several important software developments. A new initial-condition generation method was created to eliminate numerical contamination, addressing a limitation of some other cluster zoom simulations. A dedicated turbulence-diagnostics code was developed to separate cluster turbulence from bulk motions. In addition, a modern visualisation and analysis framework was produced to enable efficient exploration of the very large simulation datasets.
Scientifically, the simulations were used to investigate turbulence generation, magnetic-field amplification, and viscous heating in galaxy clusters. The work provided new insight into how plasma microphysics and heat transport affect turbulent motions, particularly in cluster outskirts. A detailed post-processing analysis of viscous (Braginskii) heating in MHD simulations indicated that while viscous heating is not sufficient to maintain thermal balance alone, it represents a non-negligible contribution. The project also demonstrated that magnetic fields are primarily amplified within galaxies at early times, implying that detailed microphysical plasma effects are not essential for capturing the large-scale magnetic dynamo in clusters.
Overall, the project produced a unique, high-resolution simulation suite, new numerical tools, and a set of quantitative predictions that can be compared with X-ray and radio observations of galaxy clusters.
