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 26 for “"Chemical Abundances"”.
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Chemical abundances in planetary nebulae in NGG 6822
… in the XX37 - XX71 spectral ranges, the relative abundances of He, N, , Ne, S are calculated with respect to H (Log (H) = 12.) for each nebula. Electron densities are derived for the planetary nebulae from the ratio of the Cs IlU line intensities, I(6716)/I(6731), while their temperatures are …
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Chemical gradients in the Milky Way from unsupervised chemical abundances measurements of the RAVE spectroscopic data set
… Experiment (RAVE) with the goal of measuring chemical abundances from the RAVE spectra and exploit them to investigate the chemical gradients along the plane of the Galaxy to provide constraints on possible Galactic formation scenarios. RAVE is a large spectroscopic survey which aims to …
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Hobby-Eberly Telescope Chemical Abundances of Stars in the Halo (CASH) project : spectroscopic analyses of the first ~80 stars
The Hobby-Eberly Telescope Chemical Abundances of Stars in the Halo (CASH) project aims to characterize the nature of the early universe through the study of metal-poor stars in the stellar halo of the galaxy. Once completed, this will be the largest set of abundances determined for metal-poor …
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Chemical and kinematic properties of bright metal poor stars
… log(g), [mu], [Fe/H]} and obtain also their chemical abundances for 17 elements including Fe, C, Sr, and Ba. Three of these stars are found to possess an overabundance of Carbon relative to Iron. Combining these chemical abundances with those from previously analyzed spectra from the same …
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Signatures of the first stars in relics of the first galaxies
… record of their past. In this thesis, I use the chemical abundances of stars in old dwarf galaxies to open a window into the era of first stars and galaxies. I begin by exploring theoretical models for interpreting the chemical signatures preserved in these relic stars. Then, I help run a suite …
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The Chemical and Dynamical Evolution of Simulated Late-Type Galaxies
… Milky Way analogues. Specifically, I investigate chemical abundances in the solar-neighbourhood and of the outflow rates of gas of Milky Way analogue discs. In the first project, I describe a galaxy simulated with the code RAMSES-CH and compare this with chemical abundance data from the Gaia-ESO …
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A pipeline for the analysis of stellar spectra
… data files into tables of stellar parameters and chemical abundances in far less time than if they were analysed by hand. The results from these surveys open new windows on to the history of our galaxy and other disk galaxies. In this thesis, we present the development of a new pipeline, the …
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Investigating the Relationship Between Chemical Abundance Ratios and Ages in Red Giant Stars
… observation of stellar pulsations by Kepler with chemical abundances from high quality spectra collected with HIRES, at the Keck Telescope, and kinematic information made available by the Gaia mission. Here, we dissect in depth a sample of 23 stars, making a detailed chemical analysis from their …
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Investigating the Relationship Between Chemical Abundance Ratios and Ages in Red Giant Stars
… observation of stellar pulsations by Kepler with chemical abundances from high quality spectra collected with HIRES, at the Keck Telescope, and kinematic information made available by the Gaia mission. Here, we dissect in depth a sample of 23 stars, making a detailed chemical analysis from their …
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Star formation, quenching and chemical enrichment in local galaxies from integral field spectroscopy
… is to expand the study of star formation and chemical abundances to resolved scales within galaxies by using integral field spectroscopy (IFS) data, mostly from the ongoing SDSS- IV MaNGA survey. In the first part of this thesis I demonstrate the ubiquitous presence of extended low ionisation …
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The Evolution of Massive Stars: The Influence of Initial Composition and Mass Loss
… in the initial metal content relative to solar abundances is to cause the models to be bluer and, in general, slightly more luminous at comparable stages of evolution. In the absence of mass loss, models with M(,i) (LESSTHEQ) 30 M(,(CIRCLE)) and Z < 0.001 do not become red supergiants prior to …
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Intergalactic baryon enrichment and implications for galaxy evolution at high redshift
… Gyr of the Universe. At z ~ 3.5, we study chemical abundances of Lyman limit systems (LLSs) and evaluate their potential to represent expected reservoirs of cold, low-metallicity gas whose accretion onto galaxies is necessary to maintain star formation. In an initial survey focused only on …
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Multi-dimensional analysis of the chemical and physical properties of spiral galaxies
… 2D spectroscopic studies are proven. The chemical composition of the whole surface of a spiral galaxy is characterised for the first time as a function not only of radius, but of the intrinsic morphology of the galaxy, allowing a more realistic determination of their physical properties. …
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The chemical evolution of galaxies explored through multi-object integral field spectroscopy
… in the process. In this way, measurements of chemical abundances within galaxies can provide insight into the different physical processes that drive galaxy evolution. The interplay between these different processes has been well studied in the local Universe by large spectroscopic surveys …
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The spatial distribution of metals in disc galaxies, via simulations and observations
… it is by a deep analysis of the distribuNon of chemical abundances in the stellar populaNons of the disc component. Abundance gradients let us reconstruct the puzzle of the formaNon and evoluNon of this type of galaxies, once we learn about the different elements that are released to the …
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Spatially-resolved studies of nearby star-forming galaxies
… are essential to understand various physical and chemical phenomena at play in the interstellar medium in the galaxies, and consequently to obtain a comprehensive picture of galaxy formation and evolution. In this thesis, I perform spatially-resolved analyses of chemical abundances and …
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THE CEPHEIDS OF M33: DISTANCE AND METALLICITY EFFECTS THROUGH SLOAN FILTERS
… large corrections, suggesting that the use of chemical abundances derived from such tracers as a proxy for Cepheid metallicity is unreliable. An independent distance determination to M33 was obtained with the tip of the red giant branch method. An average distance modulus of 24.53 \pm 0.11 mag …
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Retrieval of atmospheric properties of extrasolar planets
We present a new method to retrieve molecular abundances and temperature profiles from exoplanet atmosphere photometry and spectroscopy. Our method allows us to run millions of 1-D atmosphere models in order to cover the large range of allowed parameter space. In order to run such a large number of …
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