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 20 of 22 for “"Epoch of reionization"”.
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Modelling the Epoch of Reionization with Cosmological Radiative Transfer Simulations
The epoch of reionization is the ionization of neutral hydrogen by UV photons emitted from the first sources. While its end is well constrained by Ly𝛼 forest observations, the timeline and contributing sources remain active research areas. In this thesis, I model reionization by post-processing a …
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Numerical Simulations of Galaxy Formation During the Epoch of Reionization
… open questions in galaxy formation during the epoch of reionization and presents multiple new computational techniques developed specifically to study this era. This work naturally divides into two main sections: 1) The formation of the first massive black holes and 2) Interpreting ALMA …
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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 …
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Probing the epoch of reionization with redshifted 21 cm HI emission
Emission and absorption features in the spectrum of the diffuse radio background below 200 MHz due to the 21 cm hyperfine transition line of neutral hydrogen gas in the high redshift intergalactic medium offer a new and potentially valuable probe into the evolution of the Universe during the poorly …
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Probing the early universe with the epoch of reionization and QSO spectroscopy
… to star formation. The weaker systems' lack of evolution does not fit within this interpretation, but may be reproduced by extrapolating low redshift scaling relations between host galaxy luminosity and absorbing halo radius to earlier epochs. Using new measurements from optical spectra of …
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Polarization and its Discontents: How Polarized Foregrounds Affect 21cm Epoch of Reionization Measurements
… and occured during what is called the Epoch of Reionization (EoR). The ionization history of the intergalactic medium can be directly measured by 21cm emission from the hyperfine transition of hydrogen. Measurments of the 21cm signal from the EoR can yield information about those first …
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Robust Statistical Radio Interferometric Methods for the Detection of the Epoch of Reionization
… to detect the highly redshifted spin-flip line of HI to constrain the properties of the Epoch of Reionization and to better understand the astrophysical and cosmological processes of the early Universe. The sensitivity requirements for such a detection are exacting, since astrophysical …
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Preliminary work for three-dimensional imaging of the epoch of reionization with interferometers
A cm line of hydrogen hyperfine structure gives us an opportunity to study the formation of the first stars [11, galaxies 121 and black holes [3] as well as the standard cosmological model in the Dark Ages and the Epoch of Reionization via both the power spectrum and direct imaging [4]. In order to …
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Understanding the Epoch of Reionization Using Simulations of Lyman-α Emitting Galaxies and 21-cm Emission
… observational probe for understanding the period of the Universe’s history known as the Epoch of Reionization (EoR). In this thesis I explore: (i) how we can use simulations to model the IGM transmission to LAEs during reionization, and what simulations reveal about the environmental dependence of …
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21 cm cosmology with optimized instrumentation and algorithms
… in the past two decades thanks to a large amount of high quality data from the Cosmic Microwave Background (CMB), galaxy surveys and other cosmological probes. However, most of our universe's volume, corresponding to the period between the CMB and when the first stars formed, remains unexplored. …
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Tools, techniques, and early results in studies of 21 cm, Lyman-alpha, and H-alpha emission from the cosmic dawn
… for low frequency radio observations of 21 cm emission from the Epoch of Reionization (EOR). Using satellite transmissions as probe signals, we map the all-sky, high dynamic range antenna response of the Murchison Widefield Array (MWA) and the Hydrogen Epoch of Reionization Array …
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Instrumental Effects in 21 cm Cosmology: One-point Statistics and Power Spectrum with the HERA Interferometer
The epoch of reionization (EoR) signifies a critical phase in the universe’s evolution, marking the shift from a predominantly neutral intergalactic medium to the ionized state observed today. A key aspect of studying the EoR involves observing the redshifted 21 cm line emission with radio …
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Digital signal processing hardware for a fast fourier transform radio telescope
… is a devoloping technique for measuring the Epoch of Reionization in the universe's history. The nature of the signal measured in 21-cm tomography is such that a new kind of radio telescope is needed: one that scales well into very large numbers of antennas. The Omniscope, a Fast Fourier …
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It's always darkest before the cosmic dawn : early results from novel tools and telescopes for 21 cm cosmology
21 cm cosmology, the statistical observation of the high redshift universe using the hyperfine transition of neutral hydrogen, has the potential to revolutionize our understanding of cosmology and the astrophysical processes that underlie the formation of the first stars, galaxies, and black holes …
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Lyα emission as a sensitive probe of galactic mergers and reionization
Lyα emission has emerged as a powerful probe of the epoch of reionization. This thesis investigates how various physical processes shape Lyα emission and its connection to cosmic reionization, using state-of-the-art cosmological zoom-in simulations. By post-processing these simulations, we generate …
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From theoretical promise to observational reality : calibration, foreground subtraction, and signal extraction in hydrogen cosmology
… 21 cm transition to map out the distribution of neutral hydrogen at high redshifts, hydrogen cosmology has the potential to place exquisite constraints on fundamental cosmological parameters, as well as to provide direct observations of our Universe prior to the formation of the fist luminous …
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EoR in alternative cosmological scenarios
The aim of this Thesis is to investigate the possibility that the observations related to the epoch of reionization can probe not only the evolution of the IGM state, but also the cosmological background in which this process occurs. In fact, the history of the IGM ionization is indeed affected by …
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Accelerating Astrophysical Simulations with GPUs: A Case Study of Radiative Transfer in arepo-rt
… crucial ingredient for self-consistent modelling of numerous astrophysical phenomena across cosmic history. However, on-the-fly integration into radiation-hydrodynamics (RHD) simulations is computationally demanding, particularly due to the stringent time-stepping conditions and increased …
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Initial exploration of 21-cm cosmology with imaging and power spectra from the Murchison Widefield Array
… in Western Australia with a primary goal of measuring the power spectrum of the 21-cm signal from neutral hydrogen during the Epoch of Reionization (EoR). In this thesis, we detail efforts to characterize the MWA system, and present scientific results from a 32-element prototype …
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Conceptual design of HADES a CubeSat conducting radio astronomy in lunar orbit
… a novel CubeSat architecture to address one of the most significant challenges in modern cosmology: the detection of the redshifted 21 cm neutral hydrogen signal from the Cosmic Dawn and Epoch of Reionization. Observations in the 1 to 100 MHz frequency regime are effectively impossible from …
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