  We present deep I and z' imaging of the colour-selected cluster RzCS 052 and
study the color-magnitude relation of this cluster, its scatter, the
morphological distribution on the red sequence, the luminosity and stellar mass
functions of red galaxies and the cluster blue fraction. We find that the
stellar populations of early type galaxies in this cluster are uniformly old
and that their luminosity function does not show any sign of evolution other
than the passive evolution of their stellar populations. We rule out a
significant contribution from mergers in the buildup of the red sequence of
RzCS 052. The cluster has a large (~30%) blue fraction and and we infer that
the evolution of the blue galaxies is faster than an exponentially declining
star formation model and that these objects have probably experienced starburst
episodes. Mergers are unlikely to be the driver of the observed colour
evolution, because of the measured constancy of the mass function, as derived
from near-infrared photometry of 32 clusters, including RzCS 052, presented in
a related paper. Mechanisms with clustercentric radial dependent efficiencies
are disfavored as well, because of the observed constant blue fraction with
clustercentric distance.

Astrophysics