Exploring Cosmology via Large Scale Structure

Abstract

This thesis presents a study of the large-scale structure (LSS) of the Universe as evidenced in observations of the cosmic microwave background (CMB) and in galaxy redshift surveys. We first investigate several anomalies reported in the Wilkinson Microwave Anisotropy Probe (WMAP) CMB temperature map. In particular, we have used the Planck Early Data Release to test the WMAP beam profiles. We confirm that stacked beam profiles at Q, V and particularly at W, appear wider than expected when compared to the Jupiter beam, normalised either directly to the radio source profiles or using Planck fluxes. We also find that the WMAP source fluxes demonstrate possible non-linearity with Planck fluxes. Additionally, we find that the stacked Sunyaev-Zel'dovich (SZ) decrements of galaxy clusters observed by Planck are in agreement with the WMAP data. We find that there is no evidence for a WMAP SZ deficit as has previously been reported. We conclude that beam profile systematics can have significant effects on the CMB power spectrum with potentially important implications for Cosmology parameter fitting.
We have also mapped the local density field using K and r limited galaxy redshift distributions and number counts from the 6dF Galaxy Redshift Survey (6dFGS), Two Micron All Sky Survey (2MASS), Galaxy And Mass Assembly (GAMA) and Sloan Digital Sky Survey (SDSS) redshift surveys. We find evidence for significant galaxy underdensities in three large regions of the high latitude sky. This is in agreement with the corresponding peculiar velocities which are not compatible with recovering the CMB rest frame in the volume probed. We therefore conclude that there is some consistent evidence from both counts and Hubble diagrams for a `Local Hole' with a ≈ 150h−1Mpc under-density that deeper counts and redshifts in the Northern Galactic cap suggest may extend to ≈ 300h−1 Mpc.