The evolution of the warm-hot intergalactic medium in a hierarchically evolving Universe

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Using quasar absorption-line spectroscopy and numerical simulations we want to continue our studies on the properties of the warm-hot intergalactic medium (WHIM) and its evolution from high to low redshifts. Recent studies indicate that this high-temperature gas phase of the intergalactic medium (IGM) contains about 30 percent of the total baryon budget in the local Universe and further may represent a reservoir of the metals produced in galaxies at high redshift. In this project we are studying the distribution of baryons and metals in the WHIM from z=3 to z=0 and analyze the relation between warm-hot intergalactic gas and galactic structures at different epochs of the Universe. We want to continue our on-going analysis of HI and high-ion absorption systems in high-resolution optical and ultraviolet spectra and in synthetic spectra from numerical simulations. Using both observational and simulated spectral data we want to characterize the physical and statistical properties of WHIM absorption systems and identify the various processes that contribute to the occurrence of hot gas in the IGM, such as galactic winds and collapsing large-scale filaments. The combined analysis of simulated and observational data of the WHIM is a powerful method to tackle the problem of the “missing metals” and “missing baryons” in the Universe. Our project thus will lead to a better understanding of the evolution of the intergalactic medium in the context of a hierarchically evolving Universe.