Mutual Constraints Between Reionization Models and Parameter Extraction From Cosmic Microwave Background Data

Spectroscopic studies of high-redshift objects combined with increasingly precise data on the cosmic microwave background (CMB) are beginning to place strong bounds on the epoch of hydrogen reionization. Parameter estimation from current CMB data continues, however, to be subject to several degeneracies. Here, we focus on those degeneracies in CMB parameter forecasts related to the optical depth to reionization. We extend earlier work on the mutual constraints that such analyses of CMB data and a reionization model may place on each other to a more general parameter set, and to the case of data anticipated from the MAP satellite. A reionization model provides useful complementary information for cosmological parameter extraction from the CMB, particularly for the degeneracies between the optical depth and either of the amplitude and scalar index of the primordial power spectrum, which are still present in the most recent data. Alternatively, by using a reionization model, known limits on astrophysical quantities can reduce the forecasted errors on cosmological parameters. Forthcoming CMB data also have the potential to constrain the sites of early star formation, as well as the fraction of baryons that participate in it, if reionization were caused by stellar activity at high redshifts. Finally, we examine the implications of an independent, e.g., spectroscopic, determination of the epoch of reionization for the determination of cosmological parameters from the CMB. Subject headings: cosmic microwave background—cosmological parameters—cosmology: theory—intergalactic medium