The role played by super massive black holes in magnetizing the circum-galactic medium

The circum-galactic medium (CGM) holds the key to galaxy formation and evolution as it provides direct constrains on the stellar and supermassive black hole (SMBH) feedback processes widely believed to regulate galaxy global properties (mass, size, morphology). Yet, detailed numerical hydrodynamics simulations designed to capture these feedback processes have so far failed to produce a CGM which matches that observed around high-redshift galaxies. Presumably this failure reflects the fact that star formation and stellar feedback, and SMBH formation, accretion and feedback, take place on extremely small, sub-galactic scales, making it a tremendous challenge for simulations to model them with reasonable accuracy whilst resolving the galaxy larger scale environment at the same time.

Thanks to a super Lagrangian refinement technique specifically tuned to increase numerical resolution in the CGM, coupled to an accurate radiative transfer method to self-consistently
follow the interaction of ionising photons with the gas, the NEPHTHYS suite of cosmological zoom simulations we have recently embarked upon has started to remedy the situation.
Indeed, such an approach has, for the first time, revealed a richness of features in the CGM comparable to that observed. On the other hand, important physics is still missing from the simulations. In particular, the impact of magnetic fields --- which are measured to be in equipartition with thermal and turbulent energy in the interstellar medium of galaxies --- on the structure of the CGM remains uncharted territory. Meanwhile, theoretical predictions regarding the role these fields play in shaping galaxy evolution will undoubtedly be required to help make sense of the unprecedentedly deep radio data soon to revolutionize the field.

The DPhil project therefore consists of two stages. At first, the student will expand the NEPHTHYS suite of high-resolution cosmological simulations targetting the CGM of massive galaxies, by running their MHD counterpart and including SMBH accretion and feedback, building upon state-of-the-art algorithms previously developed within our group. Secondly, they will develop their own model for galaxy synchrotron emission based on the post-processing of these MHD simulations, in a view to produce realistic mock observational data for the coming Square Kilometer Array instrument and its precursors (in interaction with the radio astronomy observational group at Oxford centred around Prof. Jarvis).

This research falls within STFC's science programme challenge A: How did the Universe begin and how it is evolving?, and more specifically sub-challenges A.4: When and how were the first stars, black holes and galaxies born? and A.5: How do stars and galaxies evolve?