Cosmological parameters after WMAP5: forecasts for Planck and future galaxy surveys

With its increased sensitivity and resolution, the Planck satellite is expected to improve the measurement of most cosmological parameters by several factors with respect to current Wilkinson Microwave Anisotropy Probe results. The actual performance, however, may depend upon various aspects of the data analysis. In this paper, we analyse the impact of specifics of the data analysis on the actual final results. We also explore the synergies in combining Planck results with future galaxy surveys. We find that Planck will improve constraints on most cosmological parameters by a factor of 3-4 and on the tensor-to-scalar ratio r by a factor of 9. Also, inflationary parameters, like r, n(s) and n(run), are practically not degenerate any longer. The tensor spectral index, however, is little constrained. A combination of the 70 to 143 GHz channels will contain about 90 per cent of all possible information, with 143 GHz polarization information carrying about half of the constraining power on r. Also, the error on r degrades by a factor of 2 if no B modes are considered in the analysis. High-l temperature information is essential for determination of n(s) and (b), while improving noise properties increases the l-range where Planck would be cosmic-variance-limited in polarization, implying a significant improvement on the determination of r, tau and A(s). However, a sub-per-cent difference in the full width at half-maximum used in the data analysis with respect to the one in the map will result in a bias for several parameters. Finally, Planck will greatly help future missions like Large Synoptic Survey Telescope and Cosmic Inflation Probe reach their potentials by providing tight constraints on parameters like n(s) and n(run). Considering Planck together with these probes will help in breaking degeneracies between (K) and (Lambda) or (dm) and f(nu), resulting in improvements of several factors in the error associated with these parameters.