The Effect of Coupled Dark Energy on the Alignment between Dark Matter
  and Galaxy Distributions in Clusters
  We investigate the effects of a coupled Dark Energy (cDE) scalar field on the
alignment between satellites and matter distributions in galaxy clusters. Using
high-resolution N-body simulations for LCDM and cDE cosmological models, we
compute the probability density distribution for the alignment angle between
the satellite galaxies and underlying matter distributions, finding a
difference between the two scenarios. With respect to LCDM, in cDE cosmologies
the satellite galaxies are less preferentially located along the major axis of
the matter distribution, possibly reducing the tension with obersevational
data. A physical explanation is that the coupling between dark matter and dark
energy acts as an additional tidal force on the satellite galaxies diminishing
the alignments between their distribution and the matter one. Through a Wald
test based on the generalized chi-square statistics, the null hypothesis that
the two probability distributions come from the same parent population is
rejected at the 99 % confidence level. It is concluded that the galaxy-matter
alignment in clusters may provide a unique probe of dark sector interactions as
well as the nature of dark energy.
