Virialisation of Galaxy Clusters in Numerical Simulations

Numerical simulations of variants of the CDM~model with different cosmological parameters are used to compare statistical measures such as mass spectra, merger processes, and autocorrelation functions, for different models with relevant observations. The degree of virialisation of the halos is checked, and also which properties distinguish recent mergers. Mergers occur mostly in deep potential wells and mark the most important structure formation processes. As consequence, the autocorrelation function of merged halos has a higher amplitude and is steeper than that of the virialized clusters. This effect can also be seen for ultraluminous IRAS galaxies which are thought to be results from ongoing merging events.