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JOINT DAUT-ICTP-OATS-SISSA COLLOQUIUM
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Speaker: Thom Theuns (Institute for Computational Cosmology, University of Durham, UK)

Title: The intergalactic medium at redshifts 2 -- 4

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Abstract: Spectra of distant quasars at redshifts 2 -- 6 show numerous absorption lines from intervening matter. The Hydrogen Lyman-alpha transition is uncontaminated by other Hydrogen transitions over typically 400 co-moving Mpc, and can be used to probe the matter distribution and estimate the amplitude and evolution of the UV-background. The presence of other elements such as Carbon, Silicon and Oxygen, indicates that the intergalactic medium is no longer pristine but shows evidence of galactic winds or a pre-galactic generation of stars. In the pixel optical depth method, absorption is analysed directly in terms of the optical depth, avoiding some the limitations of line-fitting. I will discuss its application to estimating the amplitude and shape of the ionising background, the proximity effect, and the distribution of intergalactic metals, using a sample of 27 high-resolution spectra from UVES and Keck.
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