"Observing" Unrelaxed Clusters in Dark Matter Simulations
  We present a detailed study of relaxed and unrelaxed galaxy clusters in a
large dark-matter only simulation. Recent work has demonstrated clear
differences between the galaxy populations in clusters which have Gaussian
velocity distributions (relaxed) compared to those that do not (unrelaxed). To
directly compare with observations, we identify unrelaxed clusters in the
simulations using one-dimensional velocity distributions. We show that
non-Gaussian clusters have had recent major mergers and enhanced rates of
galaxy infall relative to systems with Gaussian velocity profiles. Furthermore,
we find that the fraction of non-Gaussian clusters increases strongly with
cluster mass and modestly with redshift. For comparison, we also make use of
three-dimensional information available in the simulations to explore the
impact of projection on observational measurements. Differences between
Gaussian and non-Gaussian clusters are much stronger when three-dimensional
information is considered, which demonstrates that the strength of observed
trends with cluster dynamics are diluted by observed velocity information being
limited to one line-of-sight.
