NoSOCS in SDSS III - The interplay between galaxy evolution and the
  dynamical state of galaxy clusters
  We investigate relations between the color and luminosity distributions of
cluster galaxies and the evolutionary state of their host clusters. Our aim is
to explore some aspects of cluster galaxy evolution and the dynamical state of
clusters as two sides of the same process. We used 10,721 member galaxies of
183 clusters extracted from the Sloan Digital Sky Survey using a list of NoSOCS
and CIRS targets. First, we classified the clusters into two categories,
Gaussian and non-Gaussian, according to their velocity distribution
measurements, which we used as an indicator of their dynamical state. We then
used objective criteria to split up galaxies according to their luminosities,
colors, and photometric mean stellar age. This information was then used to
evaluate how galaxies evolve in their host clusters. Meaningful color
gradients, i.e., the fraction of red galaxies as a function of radius from the
center, are observed for both the Gaussian velocity distribution and the
non-Gaussian velocity distribution cluster subsamples, which suggests that
member galaxy colors change on a shorter timescale than the time needed for the
cluster to reach dynamical equilibrium. We also found that larger portions of
fainter red galaxies are found, on average, in smaller radii. The luminosity
function in Gaussian clusters has a brighter characteristic absolute magnitude
and a steeper faint-end slope than it does in the non-Gaussian velocity
distribution clusters. Our findings suggest that cluster galaxies experience
intense color evolution before virialization, while the formation of faint
galaxies through dynamical interactions probably takes place on a longer
timescale, possibly longer than the virialization time.
