LowCollICM · Unraveling effects of anisotropy from low collisionality in the intracluster medium

Despite advances in both instrumental and computational capabilities, there still exists a mismatch between the observations of and theory describing galaxy clusters – the most massive gravitationally bound objects in the Universe. Galaxy clusters are used as probes for cosmological models and thus are important to our fundamental understanding of the Universe. Some differences clearly originate from an incorrect treatment of microphysical processes in large-scale cosmological simulations. This applies, in particular, to the intracluster medium (ICM). Particle collisions are rare in this hot, diffuse, magnetized plasma. In simulations the ICM is typically treated as a fully collisional fluid with an isotropic pressure. Hence, small-scale physics that stem, for example, from an anisotropic pressure, are missing. With this action the researcher will pave the way for the development of a model that allows for the incorporation of these small-scale effects into large-scale cosmological simulations. To achieve this, the researcher will implement anisotropic viscosity and thermal conduction in a next-generation, exascale simulation code. This code will then be used to conduct and analyze simulations of different aspects of the ICM covering both idealized, turbulent subvolumes and global isolated galaxy clusters. In doing so, the researcher will determine which effects are dynamically important, how they affect observables such as Faraday rotation measures and surface brightness discontinuities, and how to model them. Ultimately, future cosmological simulations employing a more accurate model will facilitate a more fundamental understanding of the magnetized Universe.