Two spectroscopically confirmed galaxy structures at z=0.61 and 0.74 in
  the CFHTLS Deep~3 field
  Adami et al. (2010) have detected several cluster candidates at z>0.5 as part
of a systematic search for clusters in the Canada France Hawaii Telescope
Legacy Survey, based on photometric redshifts. We focus here on two of them,
located in the D3 field: D3-6 and D3-43. We have obtained spectroscopy with
Gemini/GMOS and measured redshifts for 23 and 14 galaxies in the two
structures. These redshifts were combined with those available in the
literature. A dynamical and a weak lensing analysis were also performed,
together with the study of X-ray Chandra archive data. Cluster D3-6 is found to
be a single structure of 8 spectroscopically confirmed members at an average
redshift z=0.607, with a velocity dispersion of 423 km/s. It appears to be a
relatively low mass cluster. D3-43-S3 has 46 spectroscopically confirmed
members at an average redshift z=0.739. It can be decomposed into two main
substructures, having a velocity dispersion of about 600 and 350 km/s. An
explanation to the fact that D3-43-S3 is detected through weak lensing (only
marginally, at the ~3sigma level) but not in X-rays could be that the two
substructures are just beginning to merge more or less along the line of sight.
We also show that D3-6 and D3-43-S3 have similar global galaxy luminosity
functions, stellar mass functions, and star formation rate (SFR) distributions.
The only differences are that D3-6 exhibits a lack of faint early type
galaxies, a deficit of extremely high stellar mass galaxies compared to
D3-43-S3, and an excess of very high SFR galaxies. This study shows the power
of techniques based on photometric redshifts to detect low to moderately
massive structures, even at z~0.75.
