Measuring Cosmological Parameters in an Imperfect Universe

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TegmarkAST-0071213Progress in detector, space and computer technology has triggered an avalanche of high-qualitycosmological data from ongoing and upcoming experiments. However, the accuracy of present and upcoming measurements of cosmological parameters is limited by real-world headaches such as parameter degeneracies, microwave foregrounds, galaxy bias, and a long list of possible systematic errors. To take full advantage of the avalanche of great new data, the new higher level of ambition for precision cosmology must therefore be matched by a corresponding improvement in our understanding of these murky and often unpleasant issues. This is the purpose of the present proposal: to apply a number of recently developed techniques to currently available data sets to address a range of such real-world issues.The proposed work has the following main objectives: using the results of measurements of the Cosmic Microwave Background radiation field, Large Scale Structure surveys, and the recent SNIa surveys,:1. To compute joint constraints of all relevant cosmological constraints on the following ten cosmological parameters : Baryon density, Cold dark matter density , Massive neutrino density , Contribution from vacuum energy , Reionization optical depth, Spatial curvature k , Spectral index of scalar fluctuations, Spectral index of gravity waves, Primordial fluctuation amplitude, and the Relative amplitude of gravity waves, and to study the robustness of these results with respect to problems with the various input data sets.2. To compare overlapping CMB experiments to assess the levels of systematic problems, relative calibration errors and frequency-dependent foreground contamination, to combine consistent data sets into a single larger foreground-cleaned map and to compute its power spectrum with uncorrelated error bars.3. To reanalyze a number of key galaxy redshift surveys in a uniform way using the new Schlegel,Davis & Finkbeiner extinction maps and a matrix-based analysis technique that allows anexact calculation of window functions, including the so-called integral constraint, as well asthe production of a power spectrum with uncorrelated error bars. This analysis will alsoinclude the complications of scale-dependent stochastic bias, using redshift-space distortions.Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***