Halo cluster shapes: Insights from simulated galaxies and ICL with
  prospects for weak lensing applications
  We present a detailed study of the shapes and alignments of different galaxy
cluster components using hydrodynamical simulations. We compute shape
parameters from the Dark Matter (DM) distribution, the galaxy members and the
intra-cluster light (ICL). We assess how well the DM cluster shape can be
constrained by means of the identified galaxy member positions and the ICL.
Further, we address the dilution factor introduced when estimating the cluster
elongation using weak-lensing stacking techniques, which arises due to the
misalignment between the total surface mass distribution and the distribution
of luminous tracers. The dilution is computed considering the alignment between
the DM and the Brightest Cluster Galaxy, the galaxy members and the ICL. Our
study shows that distributions of galaxy members and ICL are less spherical
than the DM component, although both are well aligned with the semi-major axis
of the later. We find that the distribution of galaxy members hosted in more
concentrated subhalos is more elongated than the distribution of the DM.
Moreover, these galaxies are better aligned with the dark matter component
compared to the distribution of galaxies hosted in less concentrated subhalos.
We conclude that the positions of galaxy members can be used as suitable
tracers to estimate the cluster surface density orientation, even when a low
number of members is considered. Our results provide useful information for
interpreting the constraints on the shapes of galaxy clusters in observational
studies.
