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Open Access Publications from the University of California

Cosmology from quasar spectra

Abstract

High resolution spectroscopy of high redshift quasar spectra enables us to investigate the properties of the intergalactic medium (IGM) and measure cosmological parameters from the Ly⁺ forest. Toward high precision cosmology, this dissertation presents the following four topics. (1) Principal Component Analysis (PCA) on quasar spectrum: We introduce the PCA to describe quasar emission lines and continua quantitatively, and we attempt to make a prediction of the continuum shape in the Ly⁺ forest using wavelengths redward of Ly⁺ emission. (2) Flux calibration of Keck HIRES data: On our way to achieve high accuracy measurement, it was necessary to develop new calibration schemes and explore the origin of systematic errors. My contribution includes the following and is discussed throughout the thesis: (i) the development of the flux calibration scheme, (ii) the discovery of three emission lines in the Ly⁺ forest, (iii) the establishment of high resolution standard star spectra, and (iv) the identification of ozone lines in the spectrum. (3) D/H measurement: We present precise measurements of the primordial deuterium to hydrogen ratio (D/H) toward two quasars, HS0105+1619 and Q1243+3047, which constrains the baryon to photon ratio ₄ = 5.9 ± 0.5 \ 10-10 or the baryon density ⁾ bh2 = 0.0214 ± 0.0020 via the Big Bang Nucleosynthesis theory. (4) Studies of the Ly⁺ forest at z V 2: We also present the measurements of the total amount of neutral hydrogen absorption in the IGM. We compare our observed data with hydrodynamic simulations and find good agreement when we use the following cosmological parameters: Ho = 71 kin s-1Mpc-1, ⁾ ℓ = 0.73, ⁾m = 0.27, ⁾ b = 0.044, the amplitude of the power spectrum ¿ 8 = 0.9, and the photoinization rate œ912 = (1.44 ± 0.11) \ 10-12 s-1. We conclude that the measurements of the cosmological parameters from our primordial D/H measurements, recent WMAP satellite observation of the cosmic microwave background, and our the total amount of neutral hydrogen in the IGM at z V 2 are in a concordance with the ℓCDM model

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