Using Strong Gravitational Lensing to Identify Fossil Group Progenitors
  Fossil galaxy systems are classically thought to be the end result of galaxy
group/cluster evolution, as galaxies experiencing dynamical friction sink to
the center of the group potential and merge into a single, giant elliptical
that dominates the rest of the members in both mass and luminosity. Most fossil
systems discovered lie within $z < 0.2$, which leads to the question: what were
these systems' progenitors? Such progenitors are expected to have imminent or
ongoing major merging near the brightest group galaxy (BGG) that, when
concluded, will meet the fossil criteria within the look back time. Since
strong gravitational lensing preferentially selects groups merging along the
line of sight, or systems with a high mass concentration like fossil systems,
we searched the CASSOWARY survey of strong lensing events with the goal of
determining if lensing systems have any predisposition to being fossil systems
or progenitors. We find that $\sim$13% of lensing groups are identified as
traditional fossils while only $\sim$3% of non-lensing control groups are. We
also find that $\sim$23% of lensing systems are traditional fossil progenitors
compared to $\sim$17% for the control sample. Our findings show that strong
lensing systems are more likely to be fossil/pre-fossil systems than comparable
non-lensing systems. Cumulative galaxy luminosity functions of the lensing and
non-lensing groups also indicate a possible, fundamental difference between
strong lensing and non-lensing systems' galaxy populations with lensing systems
housing a greater number of bright galaxies even in the outskirts of groups.
