Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 11 of 11 for “"Reionisation"”.
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Investigating the Epoch of Cosmic Reionisation with Radio Interferometers
The Epoch of Reionisation (EoR) marks the cosmic period during which the neutral hydrogen (H I) that pervaded the Universe transitioned to an almost entirely ionised state. This process was driven by the energetic photons emitted by the first luminous sources. As such, the EoR encodes crucial …
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Illuminating the Universe : New Probes of Reionization and Cosmology
We model the epoch of hydrogen reionisation of the universe, using analytic as well as numerical methods. In a detailed statistical analysis of our results, we find good agreement in the alternative descriptions of the morphology of ionized regions. We use the simulations to make predictions for …
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Quasars at the High Redshift Frontier
… galaxies, cosmic metal enrichment, and hydrogen reionisation have been studied using both refined observations and powerful numerical simulations. High-redshift quasars have become a ubiquitous tool in the study of this era with more than 115 quasars now spectroscopically confirmed at z>6.0. In …
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Spectroscopic studies of star-forming galaxies and the intergalactic medium in the early Universe
… of distant galaxies well into the Epoch of Reionisation (EoR). This crucial phase transition witnessed baryonic matter, mostly in the form of cold, neutral hydrogen gas, being chemically enriched, ionised, and heated as a result of the formation of the first stars and galaxies. Here, I …
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Interferometric Methods
… ambitious experiment is the Hydrogen Epoch of Reionisation Array (HERA) in South Africa which hopes to make the first direct detection of the Epoch of Reionisation through the red-shifted H{\sc i} signal which is a factor of $10^{5}$ smaller than the thermal-like noise. In this thesis, these …
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EXCALIBRATE Bayesian calibration for data-intensive astrophysical experimentation
… such as the Dark Ages, Cosmic Dawn and Epoch of Reionisation. Included are the designs and practical considerations for a receiver unit housing numerous calibration standards, a compact microcontroller unit, portable vector network analyser and Peltier-based thermal management system for …
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Data Analysis in Global 21cm Experiments: Physically Motivated Bayesian Modelling Techniques
… when the first stars formed, and the Epoch of Reionisation, making it a key objective of modern radio cosmology. This thesis primarily investigates the application of Bayesian data analysis techniques to global 21cm cosmology, to aid in overcoming two of the most prominent difficulties in …
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New insights into primeval galaxies in the era of JWST
… formation and evolution but also the broader reionisation process. While the Hubble Space Telescope (HST) was able to identify a small sample of candidate z>7 galaxies, the James Webb Space Telescope (JWST) has revolutionised the field. The sensitivity of the near infrared camera (NIRCam) and …
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Constraining the UV background with the proximity effect
After the epoch of reionisation the intergalactic medium (IGM) is kept at a high photoionisation level by the cosmic UV background radiation field. Primarily composed of the integrated contribution of quasars and young star forming galaxies, its intensity is subject to spatial and temporal …
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The Bayesian Global Sky Model (B-GSM)
Observations of the redshifted 21-cm signal of neutral hydrogen gas from the first billion years after the Big Bang have the potential to inform studies of cosmic structure formation and fundamental physics research [3, 5]. This signal is today visible at frequencies in the range 50-200~MHz. …
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Unveiling the epoch of reionization by simulations and high-redshift galaxies
The Epoch of Reionization marks after recombination the second major change in the ionization state of the universe, going from a neutral to an ionized state. It starts with the appearance of the first stars and galaxies; a fraction of high-energy photons emitted from galaxies permeate into the …