Ages and Metallicities of Cluster Galaxies in A779 using Modified
  Str\"omgren Photometry
  In the quest for the formation and evolution of galaxy clusters, Rakos and
co-workers introduced a spectrophotometric method using the modified
Str\"omgren photometry. But with the considerable debate toward the project's
abilities, we re-introduce the system after a thorough testing of repeatability
of colors and reproducibility of the ages and metallicities for six common
galaxies in the three A779 data sets. A fair agreement has been found between
the modified Str\"omgren and Str\"omgren filter systems to produce similar
colors (with the precision of 0.09 mag in (uz-vz), 0.02 mag in (bz-yz), and
0.03 mag in (vz-vz)), ages and metallicities (with the uncertainty of 0.36 Gyr
and 0.04 dex from the PCA and 0.44 Gyr and 0.2 dex using the GALEV models). We
infer that the technique is able to relieve the age-metallicity degeneracy by
separating the age effects from the metallicity effects, but still unable to
completely break. We further extend this paper to re-study the evolution of
galaxies in the low mass, dynamically poor A779 cluster by correlating the
luminosity (mass), density, radial distance with the estimated age,
metallicity, and the star formation history. Our results distinctly show the
bimodality of the young, low-mass, metal-poor population with the mean age of
6.7 Gyr (\pm 0.5 Gyr) and the old, high-mass, metal-rich galaxies with the mean
age of 9 Gyr (\pm 0.5 Gyr). The method also observes the color evolution of the
blue cluster galaxies to red, and the downsizing phenomenon. Our analysis shows
that the modified Str\"omgren photometry is very well suited for studying low-
and intermediate-z clusters, as it is capable of observing deeper with better
spatial resolution at spectroscopic redshift limits, and the narrowband filters
estimate the age and metallicity with lesser uncertainties compared to other
methods that study stellar population scenarios.
