  By means of high-resolution N-body simulations in a LambdaCDM cosmology, we
verify that scaling relations similar to those observed for nearby galaxy
clusters are also defined by their dark matter hosts; the slopes, however, are
not the same. We then show that the scaling relations of galaxy clusters can be
explained as the result of the cosmological collapse of density fluctuations at
the appropriate scales, plus a systematic trend of the M/L ratio with cluster
mass. The empirical fact that the exponent of the Faber-Jackson relation of
elliptical galaxies is significantly different (higher) than that of clusters,
force us to conclude that the galaxy scaling laws might derive from the
cosmological collapse of density fluctuations at the epoch when galactic scales
became non-linear, plus modifications afterward due to early-time dissipative
merging.
