Unveiling the properties of the first galaxies through their connection with the intergalactic medium

ended

To understand how the first galaxies formed, we need to characterise their properties. Studying these galaxies directly is challenging, as they are hard to detect in emission. Another way of understanding galaxies in the early Universe is through their interactions with the cosmic web of gas surrounding them, which is observed as absorption lines in the spectra of distant quasars. By studying the ionization state and chemical enrichment of this gas, we can put constraints on theories of galaxy formation. During this fellowship, hosted at the Leibniz-Institut für Astrophysik Potsdam, I will use radiative transfer and hydrodynamic cosmological simulations to model the connection between galaxies and the intergalactic medium (IGM). This research will combine my skills in modelling the IGM with the expertise of my supervisor Prof. Dr. Christoph Pfrommer in the physical processes that drive galaxy outflows. The novel aspect of my work is that I will simultaneously model the evolution of the intergalactic medium on large scales, and the physics driving galaxy formation on smaller scales. In particular, I will focus on modelling metal absorption lines, which are a signature of galactic outflows. Typically, interpreting these metal lines is hard, due to the degeneracy between the ionization state of the gas and its metallicity. I will break that degeneracy by carefully calibrating the ionization state of the simulations against existing data from the Lyman-alpha forest. This will allow me to constrain the efficiency of galactic outflows, and to understand the nature of the galaxies that enriched the IGM with metals. I will construct mock observations from my simulations to make direct comparisons with real data, testing models of galaxy formation and constraining the timing of reionization. My results will be essential for interpreting existing and forthcoming observations, as well as for making predictions for the next generation of 30-metre telescopes.