Contribution of non-linear structure to the kinetic Sunyaev-Zeldovich power spectrum

In the last two decades, a satisfactory standard cosmological model has been established. On the other side, a wealth of new precise data from various astronomical observations is becoming available, leading to increased interest in details of the CMB foreground physics. In this thesis we investigate a very promising foreground effect, the kinetic Sunyaev-Zeldovich (kSZ) effect, and calculate its contribution to the CMB power spectrum. The kSZ effect is due to the interaction of CMB photons with a moving structure between the observer and the surface of last scattering, such as a cluster of galaxies, that contains ionized gas and moves with a certain peculiar velocity. The strength of the effect is determined by both the non-linear density distribution of matter inside clusters and the peculiar velocity which is governed by the linearly perturbed matter density around them. We analyze the relative importance of the the linear and non-linear contributions to the kSZ considering only gravitational interactions. We find that the non-linear contribution significantly change the power spectrum in very small scales, thus we believe including baryonic physics which also governing the nonlinear evolution of the structures is necessary. The effect of baryons is to redistribute matter toward the centres of halos, which can be dramatic when baryon component is allowed to cool. We calculate this deviation as well as its impact on the kSZ CMB power spectrum.