<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Measuring the Thermal State of the Intergalactic Medium"^^ . "The thermal evolution of the low density intergalactic medium (IGM) is a major diagnostic\r\ntool for understanding the nature and evolution of the predominant component\r\nof baryonic matter in the universe. In this study I present different approaches for\r\nmeasuring the thermal state of the IGM at different ages of the universe, in order to\r\nunderstand how it is affected by reionization processes. The main observable used to\r\nprobe the thermal state of the gas is the so-called Lyman-alpha forest. This observable\r\nconsists of a series of absorption lines in the spectra of distant quasi-stellar objects\r\n(QSOs) which arise due to the presence of residual intervening neutral hydrogen in the\r\nIGM between the observer and the QSO. Decomposing the Lyman-alpha forest into discrete\r\nabsorption profiles allows one to explore how the distribution of Lyman-alpha absorption\r\nline widths and column densities (b-NHI distribution) depends on the thermal state of\r\nthe gas, which is characterized by a temperature-density relation.\r\nIn this thesis, I quantify the parameters of the temperature-density relation using high\r\nquality UVES and HIRES QSO spectra and state of the art cosmological hydrodynamic\r\nsimulations. In the first part of this study, I apply a traditional cutoff Fitting method\r\nto the b-NHI distribution of the QSO spectra. Using simulations, I calibrate how the\r\nposition of the cutoff in the b-NHI distribution relates to the thermal state of the IGM. I\r\nfind that the thermal evolution of the IGM shows clear signatures of He II reionization\r\nat 2 < z < 3.4. In the second part of this thesis, I present a novel statistical method for\r\nconstraining the thermal state of the IGM using the full shape of the b-NHI distribution.\r\nI show that this method is more accurate and precise than the traditional cutoff Fitting\r\napproach, by applying it to mock data realizations. I confirm this by applying it to\r\nobservational data at z = 2. Finally, using this novel method, I quantify for the first\r\ntime the parameters of the temperature-density relation at low redshift (z = 0.1) using\r\nthe b-NHI distribution, and find broad agreement with theoretical expectations.\r\nOverall, this thesis demonstrates that the b-NHI distribution is a powerful statistical\r\ntool for studying the intergalactic medium and can place strong constraints on the\r\nevolution of its thermal state."^^ . "2019" . . . . . . . "Hector"^^ . "Hiß"^^ . "Hector Hiß"^^ . . . . . . "Measuring the Thermal State of the Intergalactic Medium (PDF)"^^ . . . "Hector_thesis.pdf"^^ . . . "Measuring the Thermal State of the Intergalactic Medium (Other)"^^ . . . . . . "indexcodes.txt"^^ . . "HTML Summary of #27299 \n\nMeasuring the Thermal State of the Intergalactic Medium\n\n" . "text/html" . . . "520 Astronomie"@de . "520 Astronomy and allied sciences"@en . . . "530 Physik"@de . "530 Physics"@en . .