Poster abstract

It has been shown that very massive and compact clusters evolve in the so called bimodal regime. The gas reinserted by massive stars into the ISM in the outer parts of the cluster accelerates and flows out as a cluster wind, while the gas reinserted in the central region becomes thermally unstable, cools down and forms dense clumps. We use 3D hydrodynamic simulations to study the ISM within such clusters. The cluster is modelled as a set of stars blowing winds with properties obtained from stellar evolution models. This enables us to follow in detail the process of the thermalization of the mechanical energy of the winds and formation of the hot ISM inside the cluster. In this way we estimate the heating efficiency - an important and poorly-constrained parameter which determines the fraction of the reinserted gas that leaves the cluster as a wind. The remaining part stays inside, forming dense clumps which eventually transform into a new generation of stars.