08 December 2021Séminaire – Max Grönke (MPA)

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The challenge of modeling turbulent, multiphase gas


Astrophysical systems, such as the interstellar, intracluster medium, or the circumgalactic medium, are usually multiphase with a colder phase embedded in a volume filling hot environment. Although ubiquitous, multiphase gas is notoriously hard to model which leads to often unconverged cold gas properties in large scale (cosmological) simulations. In such (turbulent) systems, hydrodynamical instabilities can destroy the cold gas on a short timescale. However, this mixing leads to intermediate temperature gas which can radiatively cool and (re)form cold gas. In this talk, I want to discuss under which conditions the cold gas can survive in a turbulent medium, and what sets the mass transfer between the phases. I will show that the survival criterion sets a characteristic scale of cold gas but the dynamics and growth will lead to a scale-free mass distribution. I will discuss implications for observations, and convergence criteria for large scale simulations, and – time permitting – why we do not have to resolve the Field length as often assumed in order to obtain converged cold gas properties.