Constraining dark energy using real and mock galaxy surveys

Abstract

In this thesis, we study how dark energy may be constrained by measurements of large-scale clustering in future galaxy surveys, and through the imprint of a time-varying large-scale potential on the CMB (the integrated Sachs-Wolfe effect).

We use semi-analytical galaxy formation models implemented in N-body simulations to build mock galaxy catalogues which are well suited for use in conjunction with large photometric surveys. Using mock catalogues, we predict that Pan-STARRS1 will be able to detect 10^8 galaxies in all its 5 photometric bands. We investigate the photo-z performance of the mock survey, which is a crucial factor when measuring large-scale structure statistics from a survey of this kind. We find using Pan-STARRS1 alone, photo-z accuracy of dz/(1+z) ~ 0.06 is achievable. The accuracy can be improved by combining near infrared photometry or by choosing a red galaxy sample. We implemented the photo-z errors to investigate their influence on the detectability of dark energy in the survey via the baryonic acoustic oscillations.

We explore the challenges of using the ISW effect as a constraint on dark energy. In particular, we investigate the effect of non-linear gravitational evolution, using N-body simulations. We have quantified the non-linear contribution to the ISW measurements in terms of both its power spectrum and its cross-correlation with large-scale structure. We have discovered that the non-linear ISW effect is more important relative to the linear ISW effect at larger scales at higher redshifts. This draws attention to the need to accurately model the non-linear effect when using galaxy samples to do ISW tomography at high redshifts. We have developed a ray-tracing method for constructing full sky maps of the ISW effect including its non-linear aspect. Using these maps, we have developed a complete picture of the non-linear ISW effect in void and cluster regions. We quantify the total contribution of the linear and non-linear ISW effects to reported abnormal CMB cold spots and discuss possible confusion with the Sunyaev-Zel'dovich effect.