Galaxy and Mass Assembly (GAMA): Probing the merger histories of massive
  galaxies via stellar populations
  The merging history of galaxies can be traced with studies of dynamically
close pairs. These consist of a massive primary galaxy and a less massive
secondary (or satellite) galaxy. The study of the stellar populations of
secondary (lower mass) galaxies in close pairs provides a way to understand
galaxy growth by mergers. Here we focus on systems involving at least one
massive galaxy - with stellar mass above $10^{11}M_\odot$ in the highly
complete GAMA survey. Our working sample comprises 2,692 satellite galaxy
spectra (0.1<z<0.3). These spectra are combined into high S/N stacks, and
binned according to both an "internal" parameter, the stellar mass of the
satellite galaxy (i.e. the secondary), and an "external" parameter, selecting
either the mass of the primary in the pair, or the mass of the corresponding
dark matter halo. We find significant variations in the age of the populations
with respect to environment. At fixed mass, satellites around the most massive
galaxies are older and possibly more metal rich, with age differences ~1-2Gyr
within the subset of lower mass satellites ($\sim 10^{10}M_\odot$). These
variations are similar when stacking with respect to the halo mass of the group
where the pair is embedded. The population trends in the lower-mass satellites
are consistent with the old stellar ages found in the outer regions of massive
galaxies.
