Linking cluster formation to large-scale structure

We use two high-resolution cold dark matter (CDM) simulations to investigat e how the formation of clusters of galaxies is related to the distribution of the surrounding mass. It is well known that in CDM universes objects gro w in a hierarchical fashion. This process cannot be completely independent of its environment. We show that when clusters form the infall pattern is n ot random, but shows clear features, which are correlated in time. In addit ion, this infall pattern correlates with the large-scale structure (LSS) su rrounding the cluster. Thus LSS not only exerts a tidal field on clustering but also specifies preferred directions from which clusters are built up. We extend this point of view and study the distribution of mass outside the clusters. We and that LSS shows a mix of both filaments and sheets, which can be clearly identified using the representation chosen for this study. F ilaments and sheets appear to be clumpy rather than homogeneous. Having ide ntified filaments we obtain mass estimates for them. We show that the mass fraction in filaments is slightly larger in a low-density universe.