Formation and evolution of heavy sub-structures in the centre of galaxy   clusters: the local effect of dark energy
  We discuss how the centres of galaxy clusters evolve in time, showing the results of a series of direct N-body simulations. In particular, we followed the evolution of a galaxy cluster with a mass $M_{clus} \simeq 10^{14} $M$_{\odot}$ in different configurations. The dynamical evolution of the system leads in all the cases to the formation of dense and massive sub-structures in the cluster centre, that form in consequence of a series of collisions and merging among galaxies travelling in the cluster core. We investigate how the structural properties of the main merging product depends on the characteristics of those galaxies that contributed to its formation. 
Manuel Arca Sedda, Martina Donnari, Marco Merafina
astro-ph.CO astro-ph.GA