The role of stellar mass and environment for cluster blue fraction, AGN
  fraction and star-formation indicators from a targeted analysis of Abell 1691
  We present an analysis of the galaxy population of the intermediate X-ray
luminosity galaxy cluster, Abell 1691, from SDSS and Galaxy Zoo data to
elucidate the relationships between environment and galaxy stellar mass for a
variety of observationally important cluster populations that include the
Butcher-Oemler blue fraction, the active galactic nucleus (AGN) fraction and
other spectroscopic classifications of galaxies. From 342 cluster members, we
determine a cluster recession velocity of 21257+/-54 km/s and velocity
dispersion of 1009^+40_-36 km/s and show that although the cluster is fed by
multiple filaments of galaxies it does not possess significant sub-structure in
its core. We identify the AGN population of the cluster from a BPT diagram and
show that there is a mild increase in the AGN fraction with radius from the
cluster centre that appears mainly driven by high mass galaxies (log(stellar
mass)>10.8). Although the cluster blue fraction follows the same radial trend,
it is caused primarily by lower mass galaxies (log(stellar mass)<10.8).
Significantly, the galaxies that have undergone recent star-bursts or are
presently star-bursting but dust-shrouded (spectroscopic e(a) class galaxies)
are also nearly exclusively driven by low mass galaxies. We therefore suggest
that the Butcher-Oemler effect may be a mass-dependant effect. We also examine
red and passive spiral galaxies and show that the majority are massive
galaxies, much like the rest of the red and spectroscopically passive cluster
population. We further demonstrate that the velocity dispersion profiles of low
and high mass cluster galaxies are different. Taken together, we infer that the
duty cycle of high and low mass cluster galaxies are markedly different, with a
significant departure in star formation and specific star formation rates
observed beyond r_200 and we discuss these findings.
