We present a summary of the cosmological implications of the Wilkinson Microwave Anisotropy Probe (WMAP) cosmic microwave background (CMB) data after 3‐years of full operation. The survey has now expanded the its results along with high resolution, full‐sky temperature maps it now has full‐sky polarization maps in five frequency bands (K,Ka, Q,V,W) between 23 and 94 GHz.
The cosmological polarization signal is notedly smaller than the associated temperature anisotropies, and therefore extracting the signal from galactic foregrounds and intrumental noise presented a significant challenge.
The combination of temperature and polarization data leads to a significant improvement in the measurement of the reionization optical depth which WMAP constrains to τ = 0.093 ± 0.029. The temperature data alone suffers from significant degeneracies between the parameters determining the initial conditions for fluctuations, the matter content and the reionization era. Including polarization data breaks a number of key degeneracies making the CMB data alone a powerful lever on the universe’s matter components and the early universe physics that seeded the initial conditions for structure formation.
