Context : Studying the evolution of galaxies located within groups may have important implications for our understanding of the global evolution of the galaxy population as a whole .
The fraction of galaxies bound in groups at z \sim 0 is as high as 60 % and therefore any mechanism ( among the many suggested ) that could quench star formation when a galaxy enters group environment would be an important driver for galaxy evolution .

Aims : Using the group catalog obtained from zCOSMOS spectroscopic data and the complementary photometric data from the COSMOS survey , we explore segregation effects occurring in groups of galaxies at intermediate/high redshifts .
Our aim is to reveal if , and how significantly , group environment affects the evolution of infalling galaxies .

Methods : We built two composite groups at intermediate ( 0.2 \leq z \leq 0.45 ) and high ( 0.45 < z \leq 0.8 ) redshifts , and we divided the corresponding composite group galaxies into three samples according to their distance from the group center .
The samples roughly correspond to galaxies located in a group ’ s inner core , intermediate , and infall region .
We explored how galaxy stellar masses and colors - working in narrow bins of stellar masses - vary as a function of the galaxy distance from the group center .

Results : We found that the most massive galaxies in our sample ( \log ( { \cal M } _ { gal } / { \cal M } _ { \odot } ) \geq 10.6 ) do not display any strong group-centric dependence of the fractions of red/blue objects .
For galaxies of lower masses ( 9.8 \leq \log ( { \cal M } _ { gal } / { \cal M } _ { \odot } ) \leq 10.6 ) there is a radial dependence in the changing mix of red and blue galaxies .
This dependence is most evident in poor groups , whereas richer groups do not display any obvious trend of the blue fraction .
Interestingly , mass segregation shows the opposite behavior : it is visible only in rich groups , while poorer groups have a a constant mix of galaxy stellar masses as a function of radius .

Conclusions : These findings can be explained in a simple scenario where color- and mass-segregation originate from different physical processes .
While dynamical friction is the obvious cause for establishing mass segregation , both starvation and galaxy-galaxy collisions are plausible mechanisms to quench star formation in groups at a faster rate than in the field .
In poorer groups the environmental effects are caught in action superimposed to secular galaxy evolution .
Their member galaxies display increasing blue fractions when moving from the group center to more external regions , presumably reflecting the recent accretion history of these groups .