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.
Results
Showing 1 to 15 of 15 for “"Lyman-α"”.
-
Cosmology from the CMB and Lyman-α forest
… remnant radiation from the Big Bang, and the Lyman-α forest, absorption features in spectra of distant quasars. A six-parameter standard model of cosmology, the ΛCDM model, can explain to great accuracy how the Universe evolved from a hot, dense state to the web of galaxies that we observe …
-
Detecting and understanding extragalactic Lyman α emission using 3D spectroscopy
… spectroscopy to detect and understand of Lyman α (Lyα) emission from high-redshift galaxies. Intrinsically the Lyα emission at λ = 1216 Å is the strongest recombination line from galaxies. It arises from the 2p → 1s transition in hydrogen. In star-forming galaxies the line is powered by …
-
Understanding the Epoch of Reionization Using Simulations of Lyman-α Emitting Galaxies and 21-cm Emission
… model the intergalactic medium (IGM) and Lyman-α emitting (LAE) galaxies in the early universe. These galaxies are a key 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 …
-
Quasars at the High Redshift Frontier
… of z=7.1. Its spectrum shows a relatively weak Lyman-α emission line, which has been interpreted as evidence of absorption by neutral gas. Attributing this to a Gunn-Peterson damping wing has led to claims that the intergalactic medium is at least 10% neutral at that redshift. However, these …
-
Early stages in cosmic structure formation
… In the second project, using observations of the Lyman-α forest in the spectra of quasars, we characterize the redshift dependence of the flux probability distribution function of the Lyman-α forest in terms of an underlying lognormal model. We find that the lognormal model is good description of …
-
Search for rapidly star-forming galaxies at high redshift.
… a weaker break at 5800Å. We suggest these may be Lyman limit and Lyman α forest absorption at z-3.8 in a galaxy forming ≈400M(⊙) year⁻¹ of stars. A large sample of galaxies (100 objects) selected to have similar properties (R – I < .5, B – R > 1) has also been found. From this sample it appears …
-
Spectroscopic studies of star-forming galaxies and the intergalactic medium in the early Universe
… in the most prominent hydrogen emission line, Lyman-α. Turning to observations, I present and analyse multiple spectroscopic datasets of individual high-redshift galaxies with the aim of understanding the process of star formation on the scale of the interstellar medium. Firstly, I show the …
-
Constraining fundamental physics from cosmology
… overshoot trajectories. Current results from the Lyman-α forest assume that the primordial power spectrum of density perturbations follows a simple power-law form with running. I perform a large suite of numerical simulations, using them to calibrate a minimally parametric framework for describing …
-
Illuminating the Cosmos: dark matter, primordial black holes, and cosmic dawn
… and cosmological probes, including the Lyman-α forest, the blackbody spectrum of the cosmic microwave background, the power spectrum of the cosmic microwave background, and the formation of the earliest stars in our universe. Second, I have investigated the formation of primordial black …
-
Introducing the Texas Euclid Survey for Lyman Alpha (TESLA) survey : initial study correlating galaxy properties to Lyman-alpha emission
We present the Texas Euclid Survey for Lyman-Alpha (TESLA), a spectroscopic survey in the 10 deg² of the Euclid North Ecliptic Pole (NEP) field. Using TESLA, we study how the physical properties of Lyman-α emitters (LAEs) correlate with Lyα emission to understand the escape of Lyα from galaxies at …
-
1. Tests of the coupled shock tube/mass-spectrometer technique ; 2. The pyrolysis of neopentane by atomic resonance absorption spectrophotometry
… resonance absorption spectrophotometry at the Lyman-α line was performed on three mixtures (20 ppm, 10 ppm, 5 ppm) of neopentane in argon to give k₁ = .17 x 10¹⁸ exp (-84800±6200/RT) sec⁻¹. This result is in very good agreement with earlier single pulse shock tube experiments. In addition, …
-
Escape of hydrogen from the exosphere of Mars
… 6 and 7 revealed it to be optically thick in Lyman α emission, along with a characteristic temperature that was higher than the majority of the collisional atmosphere of Mars. Further exploration revealed that the hydrogen in the martian exosphere was formed from photodissociation of water …
-
Probing the First Stars with the 21-cm Signal: Theory, Methods, and Forecasts
… impact the 21-cm signal. Chapter 3 considers the Lyman-photon mediated impacts of the first stars, including the Wouthuysen-Field effect, Lyman-α heating, and Lyman-Werner feedback. Chapter 4 investigates how cosmic rays emitted via the supernovae of the first stars can heat the intergalactic …
-
New insights into primeval galaxies in the era of JWST
… intrinsically strongest hydrogen emission line, Lyman-α (Lyα), to constrain the escape fraction of UV-bright galaxies in the early Universe. This shows that UV-bright galaxies appear to have low escape fractions of ionising photons, setting the scene for JWST studies of the ionising capabilities …
-
Understanding the Mechanisms that Determine the Edge Electron Density Profile in Tokamaks
… C-Mod. This is enabled by measurements of Lyman-α (Lyₐ) emission made by the LYMID camera, as well as measurements of electron density, nₑ, and electron temperature, Tₑ, by the edge Thomson scattering (ETS) system. These result in a large database of inferred neutral density, n₀ and …