Correlations between multiple tracers of the cosmic web

Tracey Friday

Published 2020-09-03Version 1

The large-scale structure of the Universe is a cosmic web of interconnected clusters, filaments, and sheets of matter. This PhD comprises two complementary projects investigating the cosmic web using correlations between three different tracers: the cosmic microwave background (CMB), supernovae (SNe), and large quasar groups (LQGs). In the first project we re-analyse the apparent correlation between CMB temperature and SNe redshift reported by Yershov, Orlov and Raikov. They presented evidence that the WMAP/Planck CMB pixel-temperatures at SNe locations tend to increase with increasing redshift. They suggest this could be caused by the Integrated Sachs-Wolfe effect and/or by residual foreground contamination. Our analysis supports the prima facie existence of the correlation but attributes it instead to a composite selection bias caused by the chance alignment of seven deep survey fields with CMB hotspots. These seven fields contain just 9.2% of the SNe sample. We estimate the likelihood of their falling on CMB hotspots by chance is approximately 1 in 11. In the second project we investigate for the first time the apparent coherent alignment of LQGs in the redshift range 1.0 <= z <= 1.8. We find that the position angles (PAs) of LQGs are correlated, specifically aligned and orthogonal, with a maximum significance of ~2.4 sigma at typical angular (comoving) separations of ~30 degrees (~1.6 Gpc). Spatial coincidence between our LQG sample and regions of quasar polarization alignment first reported by Hutsemekers, and the similarity between LQG PAs and radio polarization angles reported by Pelgrims and Hutsemekers, suggest an interesting result.