The impact of the dynamical state of galaxy groups on the stellar
  populations of central galaxies
  We study the stellar populations of the brightest group galaxies (BGGs) in
groups with different dynamical states, using GAMA survey data. We use two
independent, luminosity dependent indicators to probe the relaxedness of their
groups; the magnitude gap between the two most luminous galaxies ($\Delta
M_{12}$), and offset between BGG and the luminosity center ($D_{offset}$) of
the group. Combined, these two indicators were previously found useful for
identifying relaxed and unrelaxed groups. We find that the BGGs of unrelaxed
groups have significantly bluer NUV-r colours than in relaxed groups. This is
also true at the fixed sersic index. We find the bluer colours cannot be
explained away by differing dust fraction, suggesting there are real
differences in their stellar populations. SFRs derived from SED-fitting tend to
be higher in unrelaxed systems. This is in part because of a greater fraction
of BGGs with non-elliptical morphology, but also because unrelaxed systems have
larger numbers of mergers, some of which may bring fuel for star formation. The
SED-fitted stellar metallicities of BGGs in unrelaxed systems also tend to be
higher by around 0.05 dex, perhaps because their building blocks were more
massive. We find that the $\Delta M_{12}$ parameter is the most important
parameter behind the observed differences in the relaxed/unrelaxed groups, in
contrast with the previous study of Trevisan et al. (2017). We also find that
groups selected to be unrelaxed using our criteria tend to have higher velocity
offsets between the BGG and their group.
