Cold Fronts and Shocks Formed by Gas Streams in Galaxy Clusters
  Cold Fronts and shocks are hallmarks of the complex intra-cluster medium (ICM) in galaxy clusters. They are thought to occur due to gas motions within the ICM and are often attributed to galaxy mergers within the cluster. Using hydro-cosmological simulations of clusters of galaxies, we show that collisions of inflowing gas streams, seen to penetrate to the very centre of about half the clusters, offer an additional mechanism for the formation of shocks and cold fronts in cluster cores. Unlike episodic merger events, a gas stream inflow persists over a period of several Gyrs and it could generate a particular pattern of multiple cold fronts and shocks. 
Elad Zinger, Avishai Dekel, Yuval Birnboim, Daisuke Nagai, Erwin Lau   and Andrey. V. Kravtsov
astro-ph.GA