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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 29 for “"Lyman alpha"”.
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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 …
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Cosmological hydrodynamic simulations of the Lyman-alpha forest
… of the formation and evolution of Ly$\alpha$ forest absorbers were performed in three CDM-like cosmological models: the standard CDM model (SCDM), the flat CDM model with a nonzero cosmological constant ($\Lambda$CDM) and the open CDM model (OCDM). Synthetic spectra along random …
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The HI Lyman-alpha opacity at redshift 2.7 < z < 3.6
… into the IGM. Observations suggest that the HI Lyman-alpha effective optical depth, τ_eff, decreases with decreasing redshift, which is primarily due to the expansion of the Universe. However, some studies find a smaller value of the effective optical depth than expected at the specific redshift …
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Studying galaxy formation through Lyman alpha in emission and absorption
… gas into haloes with the formation of stars. Lyman alpha, hydrogen’s strongest spectral line, can directly probe neutral hydrogen in the high redshift Universe. Lyα can be observed in absorption in Damped Lyman Alpha systems (DLAs): high Hi column density regions that dominate the neutral gas …
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Effect of magnetic seed fields on Lyman Alpha emission from distant quasars
… gas in the intergalactic medium which affect the Lyman-Alpha spectrum we observe. In this work we investigate to what extent the properties of the Lyman-Alpha forest are sensitive to the presence of large-scale cosmological magnetic fields as a function of the seed field intensity. To do so, we …
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Erzeugung von kontinuierlicher kohärenter Lyman-alpha-Strahlung zur 1S-2P-Spektroskopie an Antiwasserstoff
… kontinuierlicher, kohärenter VUV-Strahlung bei Lyman-alpha und die Spektroskopie an Wasserstoff mit dieser Strahlung beschrieben. Die experimentellen Beobachtungen zur VUV-Erzeugung können durch Modell-Rechnungen richtig wiedergegeben werden. Lyman-alpha-Strahlung liegt bei einer Wellenlänge von …
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Measuring the Cosmological Constant Through the Lyman -Alpha Forest Using the Alcock -Paczynski Test
… in fundamental particle physics. The Lyalpha forest QSO spectra are observationally available from z ∼ 0 to z ∼ 4. Recently the concept of performing the Alcock-Paczynski test on the Lyalpha forest to determine the cosmological constant has been proposed. This motivates us to …
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Emission Line Galaxies from CADIS : High Redshift Lyman-Alpha Galaxies and Metal Poor Galaxies at Medium Redshift
… thesis, metal poor galaxies at 0.4<z<0.7 and Ly-alpha galaxies at z>4.7 have been searched for and investigated in a sample of 600 faint emission line galaxies from four fields of the Calar Alto Deep Imaging Survey (CADIS). Employing an imaging Fabry-Perot interferometer, CADIS detects emission …
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Experimental Studies of Neutral Particle Effects on Edge Transport Barriers in Tokamaks Using the Lyman-alpha Measurement Apparatus
… installed on the DIII-D tokamak to measure edge Lyman-alpha (Ly-𝛼) emission. Ly-𝛼 emission from hydrogenic isotopes can be used to infer hydrogenic neutral density and ionization rate profiles. To provide a high spatial resolution measurement in a compact footprint, the camera utilizes advanced …
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Tools, techniques, and early results in studies of 21 cm, Lyman-alpha, and H-alpha emission from the cosmic dawn
… of cross-correlation measurements between 21 cm, Lyman-a, and H-a emission from the EOR. We show that geometric effects produce percent-level correlations between low frequency radio fluxes and nearinfrared fluxes, and we set the first limit on the angular cross spectrum between 21 cm and Lyman-a …
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Spectral measurements of hydrogen Lyman-alpha in the atmospheres of Venus and Jupiter using a sounding rocket and the Hubble Space Telescope
The Lyman-alpha emission is a key signature of the presence of hydrogen, and from this emission many properties of planetary atmospheres can be analyzed. Two projects are studying this emission on two planets for two different scientific purposes. On Venus, the Lyman-alpha emission is being studied …
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Ly alpha emission galaxies in the FORS Deep Field
… Abdeckungsgrad. Alle Spektren enthalten die Lyman-alpha-Linie, welche von reiner Absorption bis zu starker Emission (Emissions-EW = -20 bis 270 Å) reicht. Die meisten Emissionslinien sind asymmetrisch, drei Galaxien besitzen ein Lyman-alpha-Profil mit zwei Emissionskomponenten. Die …
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Measurement of the Wavelength of the Lyman-alpha1 Transition of 208Pb81+ Using FOCAL Spectrometers
Measurement of theWavelength of the Lyman-alpha1 Transition of 208Pb81+ Using FOCAL Spectrometers - The goal of the experimental study is the determination of the 1s Lamb shift of a one-electron, very heavy ion with high precision by an accurate spectroscopy of the corresponding Lyman-alpha …
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QSO Absorption Lines
… epochs. This thesis describes a study of the Lyman alpha forest absorption systems seen in the spectra of high redshift QSOs. The Anglo-Australian Telescope has been used to obtain high resolution spectra of several bright QSOs. Considerable effort has gone into developing statistical …
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The transverse proximity effect in quasar spectra
… as a decreased level of absorption in the Lyman alpha forest of neutral hydrogen. This so-called proximity effect has been detected with high statistical significance towards luminous quasars. If quasars radiate rather isotropically, background quasar sightlines located near foreground …
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Quantification of the spatial structure and temporal variability of Earth's exosphere using optical tomography
… above Earth's surface. For the past decade, the Lyman-Alpha Detectors (LADs) onboard the National Aeronautics and Space Administration (NASA) Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) mission have obtained routine measurements of solar Lyman-Alpha (Ly-a) photons at 121.56 nm that …
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Properties of Galaxies Detected in Emission and Absorption with Background Quasars
… galaxies hosting Damped (DLA) and sub-Damped Lyman-alpha (sub-DLA) systems, we hope to shed some light on the subject. DLA and sub-DLA systems contain the vast majority of neutral gas in the universe, making them ideal candidates for studies of primordial gas. However, it is unclear how these …
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Quasar spectroscopy in UV and X-ray- probing the intergalactic medium using helium and oxygen
… column density and Dopper [beta]-parameter of Lyman-[alpha] ac lines, we perform Monte Carlo simulation to create a line list, from which we calculate the number of observable HeI lines. We expect that 4.5% of the HI lines have observable HeI counterparts. Future ultraviolet (UV) telescope with …
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Computational Bayesian techniques applied to cosmology
… whilst cosmic microwave background radiation and Lyman-$\alpha$ forest constraints are less significant. Specific models with a conformal time symmetry in the Friedmann equation and with an additional dark energy component are tested and shown to be competitive to the vacuum dark energy model by …
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Unveiling the epoch of reionization by simulations and high-redshift galaxies
… and the escape fraction of ionizing photons. Lyman Alpha Emitters (LAEs) represent a sample of high-redshift galaxies that are sensitive to all these galactic properties and the effects of reionization. In this thesis we aim to understand the progress of reionization by performing cosmological …
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