Abstract:
Clusters of galaxies, by virtue of their position at the high end ofthe cosmic mass function, play a fundamental role in testing models ofstructure formation. The ability of massive clusters, to significantlydistort the images of background objects via gravitational lensing,can provide direct and unique constraints on the nature of theunderlying matter distribution. I will present new results from acomprehensive strong-lensing, weak-lensing shear and magnificationanalysis of a sample of 20 high-mass clusters targeted in the CLASHsurvey. Our analysis combines high-quality data from 16-band HubbleSpace Telescope observations and wide-field multi-color imaging takenprimarily with Suprime-Cam on the Subaru Telescope. We reconstructsurface mass density profiles of individual clusters from a jointanalysis of the full lensing constraints, and determine masses andconcentrations for all clusters. For the X-ray-selected subsample, weexamine the concentration–mass relation and its intrinsic scatterusing a Bayesian regression approach. We show that the data are inexcellent agreement with LCDM predictions when the CLASH selectionfunction based on X-ray morphological regularity and the projectioneffects are taken into account. We also derive an ensemble-averagedsurface mass density profile of this subsample by stacking theirindividual profiles. The stacked lensing signal is well described by afamily of density profiles predicted for cuspy dark-matter-dominatedhalos in gravitational equilibrium, namely, the Navarro–Frenk–White,Einasto, and DARKexp models, whereas the single power-law, coredisothermal and Burkert density profiles are disfavored by the data. Weshow that cuspy halo models that include the large-scale two-halo termprovide improved agreement with the data. Finally, we develop andapply a new non-parametric method for extracting the ensemble massprofile and its logarithmic gradient. We will discuss thedetectability of the splashback radius, a physical halo boundary,using cluster lensing observations.