The matter distribution in z ~ 0.5 redshift clusters of galaxies. II :
  The link between dark and visible matter
  We present an optical analysis of a sample of 11 clusters built from the
EXCPRES sample of X-ray selected clusters at intermediate redshift (z ~ 0.5).
With a careful selection of the background galaxies we provide the mass maps
reconstructed from the weak lensing by the clusters. We compare them with the
light distribution traced by the early-type galaxies selected along the red
sequence for each cluster. The strong correlations between dark matter and
galaxy distributions are confirmed, although some discrepancies arise, mostly
for merging or perturbed clusters. The average M/L ratio of the clusters is
found to be: M/L_r = 160 +/- 60 in solar units (with no evolutionary
correction), in excellent agreement with similar previous studies. No strong
evolutionary effects are identified even if the small sample size reduces the
significance of the result. We also provide a individual analysis of each
cluster in the sample with a comparison between the dark matter, the galaxies
and the gas distributions. Some of the clusters are studied for the first time
in the optical.
