First YearWilkinson Microwave Anisotropy ProbeObservations: Dark Energy Induced Correlation with Radio Sources

The first-year WMAP data, in combination with any one of a number of other cosmic probes, show that we live in a flat -dominated CDM universe with ₘ ~ 0. 27 and _ ~ 0. 73. In this model the late-time action of the dark energy, through the integrated Sachs-Wolfe effect, should produce CMB anisotropies correlated with matter density fluctuations at z0 (95% CL, statistical errors only) with the peak of the likelihood at _=0. 68, consistent with the preferred WMAP value. A closed model with ₘ=1. 28, h=0. 33, and no dark energy component (_=0), marginally consistent with the WMAP CMB TT angular power spectrum, would produce an anti-correlation between the matter distribution and the CMB. Our analysis of the cross-correlation of the WMAP data with the NVSS catalog rejects this cosmology at the 3 level.