Exploring Cosmology via Large Scale Structure

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

The galaxy luminosity function and the Local Hole

In a previous study Whitbourn & Shanks have reported evidence for a local void underdense by ≈15 per cent extending to 150–300 h−1 Mpc around our position in the Southern Galactic Cap (SGC). Assuming a local luminosity function they modelled K- and r-limited number counts and redshift distributions in the 6dFGS/2MASS and SDSS redshift surveys and derived normalized n(z) ratios relative to the standard homogeneous cosmological model. Here we test further these results using maximum likelihood techniques that solve for the galaxy density distributions and the galaxy luminosity function simultaneously. We confirm the results from the previous analysis in terms of the number density distributions, indicating that our detection of the ‘Local Hole’ in the SGC is robust to the assumption of either our previous, or newly estimated, luminosity functions. However, there are discrepancies with previously published K- and r-band luminosity functions. In particular the r-band luminosity function has a steeper faint end slope than the r0.1 results of Blanton et al. but is consistent with the r0.1 results of Montero-Dorta & Prada and Loveday et al

The propagation of electromagnetic waves in laboratory plasmas.

This thesis describes the initial stages of a program in the Wills Plasma Physics Department within the University of Sydney for developing far-infrared diagnostics of plasmas. The author is concerned with far—infrared hydrogen cyanide (HCN) gas lasers, wave interactions with the laser plasma, and the use of the HCN laser radiation for interferometric measurements of electron densities in transient laboratory plasmas

Cardiac outcomes 12 months post percutaneous coronary intervention

Cardiovascular disease (CVD) has over the last decade emerged as the single most important cause for death worldwide [1]. Percutaneous coronary intervention (PCI) is a very common revascularisation procedure for coronary artery disease (CAD). Despite advancement in surgical technology, PCI is associated with a range of post-procedural complications, including physical [2] and psychological morbidity [3]. Research findings are inconclusive as to the impact of PCI on quality of life post-procedure. There also appears to be no studies that have examined the notion of personal resilience in this group of patients. The aim of this longitudinal prognostic study was to evaluate cardiac outcomes including - health related quality of life (HRQoL), personal resilience, mental health and adherence behaviours in patients who have had undergone a PCI measured at two time points (6 months and 12 months) post-intervention

Cosmic variance of the local Hubble flow in large-scale cosmological simulations

The increasing precision in the determination of the Hubble parameter has reached a per cent level at which large-scale cosmic flows induced by inhomogeneities of the matter distribution become non-negligible. Here, we use large-scale cosmological N-body simulations to study statistical properties of the local Hubble parameter as measured by local observers. We show that the distribution of the local Hubble parameter depends not only on the scale of inhomogeneities, but also on how one defines the positions of observers in the cosmic web and what reference frame is used. Observers located in random dark matter haloes measure on average lower expansion rates than those at random positions in space or in the centres of cosmic voids, and this effect is stronger from the halo rest frames compared to the cosmic microwave background (CMB) rest frame. We compare the predictions for the local Hubble parameter with observational constraints based on Type Ia supernova (SNIa) and CMB observations. Due to cosmic variance, for observers located in random haloes we show that the Hubble constant determined from nearby SNIa may differ from that measured from the CMB by ±0.8 per cent at 1σ statistical significance. This scatter is too small to significantly alleviate a recently claimed discrepancy between current measurements assuming a flat Λ cold dark matter (ΛCDM) model. However, for observers located in the centres of the largest voids permitted by the standard ΛCDM model, we find that Hubble constant measurements from SNIa would be biased high by 5 per cent, rendering this tension non-existent in this extreme case

An Australian longitudinal pilot study examining health determinants of cardiac outcomes 12 months post percutaneous coronary intervention

Background Percutaneous coronary intervention (PCI) is a very common revascularisation procedure for coronary artery disease (CAD). The purpose of this study was to evaluate cardiac outcomes, health related quality of life (HRQoL), resilience and adherence behaviours in patients who have undergone a PCI at two time points (6 and 12 months) following their procedure. Methods A longitudinal pilot study was conducted to observe the cardiac outcomes across a cohort of patients who had undergone a percutaneous coronary intervention (PCI). Participants who had undergone PCI 6 months prior were invited. Those participants who met the inclusion criteria and provided consent then completed a telephone survey (time point 1). These participants were then contacted 6 months later (i.e. 12 months post-intervention, time point 2) and the measures were repeated. Results All patients (n = 51) were recorded as being alive at time point 1. The multiple model indicated that controlling for other factors, gender was significantly associated with a linear combination of outcome measures (p = 0.004). The effect was moderate in magnitude (partial-η2 = 0.303), where males performed significantly better than females 6 months after the PCI procedure physically and with mood. Follow-up univariate ANOVAs indicated that gender differences were grounded in the scale measuring depression (PHQ9) (p = 0.005) and the physical component score of the short form measuring HRQoL (SF12-PCS) (p = 0.003). Thirteen patients were lost to follow-up between time points 1 and 2. One patient was confirmed to have passed away. The pattern of correlations between outcome measures at time point 2 revealed statistically significant negative correlation between the PHQ instrument and the resilience scale (CD-RISC) (r = -0.611; p < 0.001); and the physical component score of the SF-12 instrument (r = -0.437; p = 0.054). Conclusions Men were performing better than women in the 6 months post-PCI, particularly in the areas of mood (depression) and physical health. This pilot results indicate gender-sensitive practices are recommended particularly up to 6 months post-PCI. Any gender differences observed at 6 month appear to disappear at 12 months post-PCI. Further research into the management of mood particularly for women post-PCI is warranted. A more detailed inquiry related to access/attendance to secondary prevention is also warranted