POWRE: Mapping Dark Matter in Superclusters of Galaxies

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Abstract - Ma AST 9973461A concerted observational and theoretical effort to investigate the distribution of luminous and dark matter in superclusters of galaxies will be carried out. The studies of superclusters are of fundamental importance because they provide information about how light traces mass and how the mass-to-light ratio varies on the little explored distance scales of 10 Megaparsec and greater. Robust measurements of the mass-to-light ratio on such large scales are also more likely to give a representative value for the fundamental parameter, Omega, that is important in deducing the matter density of the universe. The technique of observing gravitational lensing effects may be used to study the distribution of matter in the Universe, and this research project will be one of the first attempts to apply the gravitational lensing method on supercluster scales.The research has three components: (1) Data acquisition via optical wavelength observations. In order to maximize the feasibility of detecting gravitational lensing signals, the 10-meter Keck telescope in Hawaii will be used to obtain high-quality images and spectra of two carefully chosen superclustering fields; (2) Data analysis of the observations in both the strong lensing (gravitational arcs) and weak lensing (correlated distortion in images of background galaxies) regimes will be used to construct the mass density maps; (3) A theoretical study of systematic effects and the dependence of lensing signatures on cosmological parameters will be carried out. Numerical simulations, on supercomputers, of various plausible cosmological models will be performed to quantify the level of contamination due to intervening mass fluctuations in the lower-density intra-cluster regions of superclusters. These numerical simulation results will be used to allow the statistically significance of the observational results to be assessed.