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 68 for “"Neutral Hydrogen"”.
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Neutral Hydrogen in Local Group Dwarf Galaxies
… thesis explores these questions by studying the neutral hydrogen (HI) component of dwarf galaxies. First, limits on the HI mass of the ultra-faint dwarfs are presented, and the HI content of all Local Group dwarf galaxies is examined from an environmental standpoint. We find that those Local …
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Solar-activity-based neutral hydrogen geocorona model
Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2024-05-01
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Neutral hydrogen observations of spiral and irregular galaxies
This thesis describes hydrogen-line observations using the Cambridge Half-Mile telescope. The initial chapters describe observations of two nearby galaxies af late spiral type, namely M33 and NGC 2403. The severe warping of the HI layer in the outer parts of M33 was clearly seen, and the origin of …
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Compact Galactic Neutral Hydrogen Clouds in the GALFA-HI Survey
… in our Galaxy appears. Since the detection of neutral hydrogen in 1951, each new survey has revealed new structure. Using the GALFA-HI survey, we have discovered five populations of compact neutral hydrogen clouds. We began by developing a machine-vision algorithm to identify compact clouds in …
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The Omniscope : mapping the Universe in 3D with neutral hydrogen
21 cm tomography has the potential to become the most powerful cosmological probe yet. The Omniscope is a novel radio telescope being built to take advantage of this signal. This thesis describes my work on integrating, testing, and characterizing all modules of the Omniscope and identifying …
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Neutral hydrogen mass distributions in galaxies uncovered by three-dimensional stacking
Atomic hydrogen (HI) serves as the raw fuel from which the star-forming molecular hydrogen forms - making it an important tracer of galaxy evolution. Due to the intrinsic faintness of the HI emission line (observed at rest at 21 cm), detecting HI emission in galaxies beyond a z = 0.1 becomes …
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Analysis of low-energy neutral hydrogen fluxes using an electron cyclotron resonance-heated discharge
… and proof-of-principle verification of a neutral hydrogen flux detection system, based on an ECRH discharge as the neutral flux ionizer. The significant features of the ionizer are its small size and simultaneous excitation of the ECRH mode using a 30 MHz RF driver and relatively small …
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Kinematics of neutral hydrogen in interacting galaxies in two groups from the MeerChoirs survey
… local universe as the extended distribution of neutral hydrogen makes it susceptible to a wide range of environmental effects that produce peculiar HI morphologies. Moreover, HI enables the study of how galaxies obtain and lose cold gas. The HI distribution of galaxies often exhibits warps, …
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Kinematics of neutral hydrogen in interacting galaxies in two groups from the MeerChoirs survey
… local universe as the extended distribution of neutral hydrogen makes it susceptible to a wide range of environmental effects that produce peculiar HI morphologies. Moreover, HI enables the study of how galaxies obtain and lose cold gas. The HI distribution of galaxies often exhibits warps, …
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Kinematics of neutral hydrogen in interacting galaxies in two groups from the MeerChoirs survey
… local universe as the extended distribution of neutral hydrogen makes it susceptible to a wide range of environmental effects that produce peculiar HI morphologies. Moreover, HI enables the study of how galaxies obtain and lose cold gas. The HI distribution of galaxies often exhibits warps, …
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Quenching mechanisms in recently quenched elliptical galaxies: insights from neutral hydrogen studies and environmental analysis
… and descendants (postRQEs), focusing on their neutral hydrogen (HI) content and star formation properties. Contrary to conventional quenching models emphasizing gas depletion, RQEs retain substantial HI reservoirs (fgas ≥ 17%), suggesting that quenching is not primarily driven by gas …
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Neutral gas and the magnetic field in the Galactic Center
… via Zeeman splitting of the 21-cm line of neutral hydrogen. In addition, I report a 3$\sigma$ upper limit of 2 mG for $B\sb\Vert$ in the neutral hydrogen within the circumnuclear disk of M82.
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H (sub) alpha & Neutral Density Scaling in the Maryland Centrifugal eXperiment
The Maryland Centrifugal eXperiment (MCX) is a hydrogen plasma confinement experiment with a rotating mirror magnetic configuration. This experiment was designed to test the concepts of centrifugal confinement and velocity shear stabilization which may allow scaleability to a fusion reactor. These …
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A HI search for galaxies hidden by the Galactic bulge
In this thesis, a deep neutral hydrogen (HI) galaxy search for galaxies hidden by the Galactic Bulge is presented. The HI Parkes deep HI Zone of Avoidance (ZOA) survey has been extended towards the higher latitudes in the Galactic Bulge region. The surveyed region covers 332° ≤ l ≤ 36° for the …
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Studying galaxy formation through Lyman alpha in emission and absorption
… of the central problems of Physical Cosmology. Neutral hydrogen plays an important role, linking the collapse of cooling 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 …
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Charge Transfer Cross-Sections for Nitrogen(v) and Sulfur(iii) Ions Interacting With Hydrogen Atoms in Astrophysical Plasmas
… values for the reactive cross sections involving neutral hydrogen and helium are not generally available. In the absence of such values, one must rely on theoretical calculations of the relevant reaction rates.
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Investigating the Epoch of Cosmic Reionisation with Radio Interferometers
… (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 information about the nature …
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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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Robust Estimation Techniques for the Cosmological Analysis of Large Scale Structure
… counts-in-cells statistic for the first time to neutral hydrogen. Neutral hydrogen is particularly interesting for counts-in-cells statistics because of the vast regions that can be covered by intensity mapping. We find percent-level accuracy when comparing the prediction for the density in …
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A multi-wavelength study of the dwarf galaxies NGC 2915 and NGC 1705 : star formation, gas dynamics and dark matter
… each galaxy consists of new observations of the neutral hydrogen (Hi) line obtained with the Australia Telescope Compact Array, October 2006 - May 2007. The stellar disk of NGC 1705 is host to an intense star-bursting core which is rapidly depleting the galaxy's central Hi reservoir. This galaxy …
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