Monday, July 18, 2011 - 11:30am
"Strong-lensing clusters: how peculiar are they?"
Abstract. In modern cosmology, galaxy clusters are becoming more and more important, in particular to test the predictions of the cold-dark-matter paradigm on scales much smaller than those probed by CMB observations. Most important cosmological applications are based on accurate measurements of the mass profile of these structures. Among the methods to trace the matter content of clusters, gravitational lensing plays a fundamental role, thanks to its ability to constrain the mass distribution without making assumptions on the dynamical state of the cluster. In particular, it has been proofed that the combination of strong- and weak-lensing measurements allows to accurately measuring the mass profiles, improving significantly over methods based on weak-lensing only. However, if we focus on the sub-population of clusters that are able to produce strong-lensing effects, some odd behaviors are revealed by recent observations. For example, several strong lensing clusters seem to have extremely large Einstein radii and cross sections for large distortions. At the same time, in these clusters anomalously high concentrations are measured. These observations seem to indicate that strong lensing clusters may be extremely biased objects. These biases need to be properly understood and quantified if we aim at using clusters as cosmological tools. In this talk, I will discuss the properties of strong lensing clusters as they emerge from the analysis of a large number of numerically simulated halos in a LCDM context.