Intergalactic stellar populations in intermediate redshift clusters
  A substantial fraction of the total stellar mass in rich clusters of galaxies
resides in a diffuse intergalactic component usually referred to as the
Intra-Cluster Light (ICL). Theoretical models indicate that these intergalactic
stars originate mostly from the tidal interaction of the cluster galaxies
during the assembly history of the cluster, and that a significant fraction of
these stars could have formed in-situ from the late infall of cold metal-poor
gas clouds onto the cluster. The models make predictions about the age
distribution of the ICL stars, which may provide additional observational
constraints. However, these models also over-predict the fraction of stellar
mass in the ICL by a substantial margin. Here we present population synthesis
models for the ICL of a dumb-bell dominated intermediate redshift (z=0.29)
X-ray cluster for which we have deep MOS data obtained with the FORS2
instrument. In a previous paper we have proposed that the dumbell galaxy act as
a grinding machine tearing to pieces the galaxies that pass nearby thus
enriching the intergalactic medium. In this paper we analyze the spectra at
different locations within the ICL and find that it is dominated by old metal
rich stars, at odds with what has been found in nearby clusters where the stars
that dominate the ICL are old and metal poor. While we see a weak evidence of a
young, metal poor, component, if real, these young stars would amount to less
than 1% of the total ICL mass, much less than the up to 30% predicted by the
models. We propose that the very metal rich (i.e. 2.5 times solar) stars in the
ICL of our cluster, which comprise approximately 40% of the total mass,
originate mostly from the central dumb-bell galaxy, while the remaining solar
and metal poor stars come from spiral, post-starburst (E+A), and metal poor
dwarf galaxies. About 16% of the ICL stars are old and metal poor.
