Diffuse Intracluster Light at Intermediate Redshifts: ICL observations
  in a X-ray cluster at z=0.29
  The diffuse intracluster light (ICL) contains a significant fraction of the
total stellar mass in clusters of galaxies, and contributes in roughly equal
proportion as the hot intra-cluster medium (ICM) to the total baryon content of
clusters. Because of the potential importance of understanding the origin of
the ICL in the context of the formation and evolution of structure in the
Universe, the field has recently undergone a revival both in the quality and
quantity of observational and theoretical investigations. Due to cosmological
dimming, the observational work has mostly concentrated on low redshift
clusters, but clearly observations at higher redshifts can provide interesting
clues about the evolution of the diffuse component. In this paper we present
the first results of a program to characterize the ICL of intermediate redshift
clusters. We find that at z ~ 0.3, the X-ray cluster RX J0054.0-2823 already
has a significant ICL and that the fraction of the total light in the ICL and
the brightest cluster galaxy (BCG) is comparable to that of similar clusters at
lower redshift. We also find that the kinematics of the ICL is consistent with
it being the remnant of tidally destroyed galaxies streaming in the central
regions of the cluster, which has three central giant elliptical galaxies
acting as an efficient "grinding machine". Our cluster has a bi-modal
radial-velocity distribution and thus two possible values for the velocity
dispersion. We find that the cluster fits well in the correlation between
BCG+ICL fraction and cluster mass for a range of velocity dispersions, leading
us to question the validity of a relevant correlation between these two
quantities.
