Dark matter stripping in galaxy clusters: a look at the Stellar to Halo
  Mass relation in the Illustris simulation
  Satellite galaxies in galaxy clusters represent a significant fraction of the
global galaxy population. Because of the unusual dense environment of clusters,
their evolution is driven by different mechanisms than the ones affecting field
or central galaxies. Understanding the different interactions they are subject
to, and how they are influenced by them, is therefore an important step towards
explaining the global picture of galaxy evolution. In this paper, we use the
publicly-available high resolution hydrodynamical simulation Illustris-1 to
study satellite galaxies in the three most massive host haloes (with masses
$M_{200} > 10^{14}\,h^{-1}\rm{M}_{\odot}$) at $z=0$. We measure the
Stellar-to-Halo Mass Relation (hereafter SHMR) of the galaxies, and find that
for satellites it is shifted towards lower halo masses compared to the SHMR of
central galaxies. We provide simple fitting functions for both the central and
satellite SHMR. To explain the shift between the two, we follow the satellite
galaxies since their time of accretion into the clusters, and quantify the
impact of dark matter stripping and star formation. We find that subhaloes
start losing their dark matter as soon as they get closer than $\sim 1.5\times
R_{\rm{vir}}$ to the centre of their host, and that up to 80\% of their dark
matter content gets stripped during infall. On the other hand, star formation
quenching appears to be delayed, and galaxies continue to form stars for a few
Gyr after accretion. The combination of these two effects impacts the ratio of
stellar to dark matter mass which varies drastically during infall, from 0.03
to 0.3.
