The Impact of Radiation and Feedback from Stars and Supermassive Black Holes on the High-Redshift Circum-Galactic Medium

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One of the major conflicts between ACDM, our standard cosmological model, and observations, is that the number of satellite galaxies and amount of gas observed in the Universe is less than predicted. Thanks to the unprecedented resolution it reaches in the circum-galactic medium (CGM) of high-redshift galaxies, the NEPHTHYS suite of cosmological zoom simulations reveals that this CGM hosts complex novel structures shaped by the interplay of cold filamentary inflows and radiative outflows driven by massive stars and supermassive black holes embedded within the galaxies themselves. It is speculated that such powerful outflows could disrupt satellite galaxies and significantly heat up inflowing gas, generating in the process a pronounced warm CGM phase which would be extremely difficult to detect with current telescopes. Using the NEPHTHYS suite combined with a new photon tracer algorithm developed within our group, the student will explore the viability of this scenario, focussing on massive galaxies at z~2. More specifically, the aim of the DPhil project is to understand how the properties of the CGM of these galaxies change at different evolutionary stages,resolve how it is ionized by different classes of sources (stars, Active Galactic Nuclei) and determine how this affects absorption line diagnostics, in order to assess whether outflows can truly account for the discrepancies between ACDM and observations.