The Three Hundred project: galaxy cluster mergers and their impact on
  the stellar component of brightest cluster galaxies
  Using the data set of The Three Hundred project, i.e. a suite of 324
hydrodynamical resimulations of cluster-sized haloes, we study galaxy cluster
mergers and their effect on colour and luminosity changes of their brightest
cluster galaxies (BCG). We track the main progenitor of each halo at z=0 and
search for merger situations based on its mass accretion history, defining
mergers as very rapid increases in the halo mass. Based upon the evolution of
the dynamical state of the cluster we define a pre- and post-merger phase. We
create a list of all these events and statistically study their mass ratio and
timescales, with the former verifying that all instances are in fact major
mergers. By comparing to a control sample of clusters without mergers, we study
the effect mergers have on the stellar component of the BCG. Analysing the
mass, age and metallicity of the BCG stellar particles, we find that the
stellar content of BCGs grows significantly during mergers and, even though the
main growth mechanism is the accretion of older stars, there is even a burst in
star formation induced by the merger. In our simulations, BCGs in mergers form
in median around 70 per cent more stars than those normally growing, although
this depends on the radius considered for defining the BCG. Regarding
observable properties, we see an increase in SDSS-u luminosity of 20 per cent
during mergers, accompanied by a slightly slower increase of the galaxy g-r
colour as compared to the control sample.
