Stellar Populations of BCGs, Close Companions and Intracluster Light in
  Abell 85, Abell 2457 and IIZw108
  We present the first results from an integral field (IFU) spectroscopic
survey of a 75kpc region around three Brightest Cluster Galaxies (BCGs),
combining over 100 IFU fibres to study the intracluster light (ICL). We fit
population synthesis models to estimate age and metallicity. For Abell 85 and
Abell 2457, the ICL is best-fit with a fraction of old, metal-rich stars like
in the BCG, but requires 30-50% young and metal-poor stars, a component not
found in the BCGs. This is consistent with the ICL having been formed by a
combination of interactions with less massive, younger, more metal-poor cluster
members in addition to stars that form the BCG. We find that the three galaxies
are in different stages of evolution and may be the result of different
formation mechanisms. The BCG in Abell 85 is near a relatively young,
metal-poor galaxy, but the dynamical friction timescale is long and the two are
unlikely to be undergoing a merger. The outer regions of Abell 2457 show a
higher relative fraction of metal-poor stars, and we find one companion, with a
higher fraction of young, metal-poor stars than the BCG, which is likely to
merge within a gigayear. Several luminous red galaxies are found at the centre
of the cluster IIZw108, with short merger timescales, suggesting the system is
about to embark on a series of major mergers to build up a dominant BCG. The
young, metal-poor component found in the ICL is not found in the merging
galaxies.
