Barred disks in dense environments
  We investigate the properties of bright (MV <= -18) barred and unbarred disks
in the Abell 901/902 cluster system at z~0.165 with the STAGES HST ACS survey.
To identify and characterize bars, we use ellipse-fitting. We use visual
classification, a Sersic cut, and a color cut to select disk galaxies, and find
that the latter two methods miss 31% and 51%, respectively of disk galaxies
identified through visual classification. This underscores the importance of
carefully selecting the disk sample in cluster environments. However, we find
that the global optical bar fraction in the clusters is ~30% regardless of the
method of disk selection. We study the relationship of the optical bar fraction
to host galaxy properties, and find that the optical bar fraction depends
strongly on the luminosity of the galaxy and whether it hosts a prominent bulge
or is bulgeless. Within a given absolute magnitude bin, the optical bar
fraction increases for galaxies with no significant bulge component. Within
each morphological type bin, the optical bar fraction increases for brighter
galaxies. We find no strong trend (variations larger than a factor of 1.3) for
the optical bar fraction with local density within the cluster between the core
and virial radius (R ~ 0.25 to 1.2 Mpc). We discuss the implications of our
results for the evolution of bars and disks in dense environments.
