On the coherent rotation of diffuse matter in numerical simulations of
  galaxy clusters
  We present a study on the coherent rotation of the intracluster medium and
dark matter components of simulated galaxy clusters extracted from a
volume-limited sample of the MUSIC project. The set is re-simulated with three
different recipes for the gas physics: $(i)$ non-radiative, $(ii)$ radiative
without AGN feedback, and $(iii)$ radiative with AGN feedback. Our analysis is
based on the 146 most massive clusters identified as relaxed, 57 per cent of
the total sample. We classify these objects as rotating and non-rotating
according to the gas spin parameter, a quantity that can be related to cluster
observations. We find that 4 per cent of the relaxed sample is rotating
according to our criterion. By looking at the radial profiles of their specific
angular momentum vector, we find that the solid body model is not a suitable
description of rotational motions. The radial profiles of the velocity of the
dark matter show a prevalence of the random velocity dispersion. Instead, the
intracluster medium profiles are characterized by a comparable contribution
from the tangential velocity and the dispersion. In general, the dark matter
component dominates the dynamics of the clusters, as suggested by the
correlation between its angular momentum and the gas one, and by the lack of
relevant differences among the three sets of simulations.
