Cross-correlation between cosmic microwave background anisotropies and future galaxy surveys

Resumen

The cosmic microwave background (CMB) is a snapshot of the Universe at early times (z ∼ 1100). In the recent years, several experiments have provided constraints on the concordance ΛCDM model from a statistical analysis of the CMB anisotropies. On the other hand, many galaxy surveys will measure the 3D distribution of the dark matter component of the Universe with unprecedented sensitivity and sky coverage. This is a complementary probe to the CMB, since it traces the evolution of the Universe at low redshift. The addition of the two probes will break degeneracies in the parameters which are left when using either CMB or large scale structure (LSS). Moreover, the contributions to the CMB anisotropies along the line-of- sight -the so-called secondary CMB anisotropies- are correlated with the growth of perturbations at low redshift. Therefore, we have an important information in addition to the simple combination of the CMB with large scale structure (LSS) probes from galaxy surveys: the cross-correlation be- tween the CMB and LSS probes, such as galaxy number counts and weak lensing. In this thesis, we study the capability of the CMB-LSS cross- correlation for constraining cosmological parameters alone or in combination with the CMB and LSS, using mock data and statistical methodologies, in the perspective of upcoming and future cosmological surveys. First, we explore the capabilities of the lensing ratio between the CMB lensing - galaxy clustering and weak lensing - galaxy clustering cross- correlations, an estimator that under certain approximations is indepeddent on some astrophysical uncertainties such as the galaxy bias and on the multipoles. We forecast a measurement of this ratio with an error around 1-2% using Euclid and future CMB lensing experiments. Furthermore, we evaluate the impact on this ratio of the inclusion of general relativity contributions to the galaxy number counts. We find that accounting for the lensing magnification contribution induces a multipole dependence of the ratio that will not be negligible for future surveys, and propose a new estimator in order to take it into account. With the new formalism, we forecast by a Fisher matrix approach the capability of the lensing ratio for constraining cosmological parameters when it is added to the CMB information. We find that in extended cosmological models the lensing ratio can improve the errors on the dark energy parameters of state and on the curvature density. We have also investigated the global importance of the CMB - LSS cross-correlation in a 2D tomographic approach for a joint analysis CMB and galaxy number counts in the angular space. For this, we compute by a Fisher matrix approach the joint constraints on many extended cosmological models, including the dark energy parametrization for a redshift dependent equation of state, neutrino physics and primordial Universe parameters. We find that the inclusion of cross-correlation can improve the dark energy figure of merit up to a factor ∼ 2. We forecast a detection of the neutrino mass with >∼ 3σ significance by combining CMB-S4 with SPHEREx, just by the analysis of quasi-linear scales. We also predict the measurement of the primordial local non-Gaussianity parameter fNL with an uncertainty ∼1-2 by combining the CMB with future radio continuum surveys such as SKA. Our methodology is then applied to models of features caused by deviations from a power law primordial power spectrum. We find that the cross-correlation is useful for helping to constrain these models, in particular for surveys with large redshift coverage such as the radio continuum ones. As a further step, we extend the analysis to the inclusion of weak lensing as additional probe and present the results for the combination of the full Euclid likelihood with the CMB.