A journey from the outskirts to the cores of groups I: Color- and
  mass-segregation in 20K-zCOSMOS groups
  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. We
built two composite groups at intermediate (0.2 <= z <= 0.45) and high (0.45 <
z <= 0.8) redshifts, and we divided the corresponding composite group galaxies
into three samples according to their distance from the group center. 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. We found that the most massive galaxies in our sample (Log(M_gal/M_sun)
>= 10.6) do not display any strong group-centric dependence of the fractions of
red/blue objects. For galaxies of lower masses (9.8 <= Log(M_gal/M_sun) <=
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. We suggest 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.
