Cosmic Microwave Background polarization and the ionization history of the Universe

Abstract

We point out that polarization measurements as planned for the upcoming PLANCK mission can significantly enhance the accuracy of cosmic parameter estimation compared to the temperature anisotropy spectrum alone. In order to illustrate this, we consider a standard cosmological model and several modifications that adjust one parameter each to fit the recently published Maxima-1 data. While all models produce acceptable fits as far as the power spectrum is concerned, their corresponding polarization spectra differ widely. The strongest differences are expected for a model with delayed recombination, reflecting the fact that polarization measurements are most sensitive to the processes governing the epoch of recombination.