Last stand before WMAP: Cosmological parameters from lensing, CMB, and galaxy clustering

Cosmic shear measurements have now improved to the point where they deserve to be treated on par with cosmic microwave background (CMB) and galaxy clustering data for cosmological parameter analysis, using the full measured aperture mass variance curve rather than a mere phenomenological parametrization thereof. We perform a detailed 9-parameter analysis of recent lensing [the Red Sequence Cluster Survey (RCS)], CMB (up to Archeops) and galaxy clustering (2dF Collaboration) data, both separately and jointly. CMB and 2dF data are consistent with a simple flat adiabatic scale-invariant model with ΩΛ=0.72±0.09, h2Ωcdm=0.115±0.013, h2Ωb=0.024±0.003, and a hint of reionization around z∼8. Lensing helps further tighten these constraints, but reveals tension regarding the power spectrum normalization: including the RCS survey results raises σ8 significantly and forces other parameters to uncomfortable values. Indeed, σ8 is emerging as the currently most controversial cosmological parameter, and we discuss possible resolutions of this σ8 problem. We also comment on the disturbing fact that many recent analyses (including this one) obtain error bars smaller than the Fisher matrix bound. We produce a CMB power spectrum combining all existing experiments, useful for a 'WMAP versus world' comparison to test how realistic the error estimates have been in the cosmology community. Comparing with the WMAP results shows remarkably good agreement both on the power spectrum and on cosmological parameters, which means that precision cosmology has passed an important test