The extremely high sensitivity and resolution of the Square Kilometre Array (SKA) will be useful for addressing a wide set of themes relevant for cosmology, in synergy with current and future cosmic microwave background (CMB) projects. Many of these
themes also have a link with future optical-IR and X-ray observations. We discuss the scientific perspectives for these goals, the instrumental requirements and the observational and data analysis approaches, and identify several topics that are important for cosmology and astrophysics at different cosmic epochs.
In this article we focus on the astrophysical results and the related cosmological implications derived from recent microwave surveys, with emphasis to those coming from the Planck mission. We critically discuss the impact of systematics effects and
the role of methods to separate the cosmic microwave background signal from the astrophysical emissions and each different astrophysical component from the others. We then review of the state of the art in diffuse emissions, extragalactic sources, cosmic infrared back- ground, and galaxy clusters, addressing the information they provide to our global view of the cosmic structure evolution and for some crucial physical parameters, as the neutrino mass. Finally, we present three different kinds of scientific perspectives for fundamental physics and cosmology offered by the analysis of on-going and future cosmic microwave background projects at different angular scales dedicated to anisotropies in total intensity and polarization and to absolute temperature.
We compute the imprints left on the CMB by two cosmic reionization models consistent with current observations but characterized by alternative radiative feedback prescriptions (suppression and filtering) resulting in a different suppression of star
formation in low-mass halos. The models imply different ionization and thermal histories and 21 cm background signals. The derived Comptonization, u, and free-free distortion, y_B, parameters are below current observational limits for both models. However, the value of u = 1.69 * 10^-7 (9.65 * 10^-8) for the suppression (filtering) model is in the detectability range of the next generation of CMB spectrum experiments. Through the dedicated Boltzmann code CMBFAST, modified to include the above ionization histories, we compute the CMB angular power spectrum (APS) of the TT, TE, and EE modes. For the EE mode the differences between these models are significantly larger than the cosmic and sampling variance over the multipole range l = 5-15, leaving a good chance of discriminating between these feedback mechanisms with forthcoming/future CMB polarization experiments. The main limitations come from foreground contamination: it should be subtracted at per cent level in terms of APS, a result potentially achievable by novel component separation techniques and mapping of Galactic foreground.
