Testing the Standard Cosmological Model

Abstract

This thesis exploits the wealth of information contained in the existing cosmological surveys, and demonstrates how the use of tools such as two-point statistics permit the extraction of such information. In particular, the wide field imaging survey – the Sloan Digital Sky Survey (SDSS) in conjunction with Luminous Red Galaxy (LRG) spectroscopic surveys carried out by the Two-degree-Field (2dF) and AAOmega instruments on the Anglo-Australian telescope (AAT) are utilised here. This also includes the observations of the Cosmic Microwave Background (CMB) radiation from the Wilkinson Microwave Anisotropy Probe (WMAP) experiment.

Combining the imaging and spectroscopic surveys, we extract three photometric LRG samples at redshift 0.35, 0.55 and 0.7 which cover 7600 deg2 of the sky, probing a total cosmic volume of 5.5 h^−3 Gpc^3. We find very little clustering evolution in these massive early-type galaxies out to z~0.8 or nearly half the age of the Universe. The shape of the large-scale correlation functions is consistent with a simple ‘high-peaks’ bias and linear theory framework of the standard CDM model. The new z=0.7 LRG sample is then
used in the CMB-LSS cross-correlation analysis to look for the the Integrated Sachs-Wolfe (ISW) effect as a dynamical evidence for the accelerated expansion of the Universe. The
measured zero CMB-LRG correlation is inconsistent with the CDM model expectation at 2.2sigma significance level. Furthermore, our rotation tests show that the previous detections of the ISW effect may not be as significant as previously claimed.

We make independent estimates of the WMAP CMB temperature power spectra and show explicitly how sensitive they are to the instrumental beams. We propose an alternative method for determining the beam profiles by stacking radio point sources and demonstrate its robustness via Monte Carlo simulations plus realistic point source detection algorithm. Using this technique, we find significantly wider W-band beam profiles than the WMAP Jupiter beam analysis. We also find a tentative evidence for a non-linearity in the WMAP radio source fluxes when compared with the ground-based
measurements. Finally, we investigate if the recently claimed timing offset in the WMAP time-ordered data can explain the observed wider than expected beam profile.