Jaydy Bellaard

Jaydy's bachelor thesis concerns the physics and philosophy of the effects of Active Galactic Nuclei (AGN) feedback on dark matter. AGN feedback is known to suppress the matter power spectrum on nonlinear scales. Modelling this suppression is of key importance for gravitational lensing surveys and has been the topic of much attention in cosmology recently. Many works attempt to find effective fits to the total matter power spectrum suppression from hydrodynamical simulations. Comparatively, little attention has gone into understanding the AGN feedback effect on the dark matter itself. We know from cosmological hydrodynamical simulations that the dark matter component backreacts to the presence of AGN feedback. The shape of this back reaction is quite different from the total matter power spectrum suppression. To our knowledge, no attempt has been made to find effective fits to this back reaction, nor to compare it across feedback realizations or redshift, to find a unified relation a la van Daalen+. This is the main goal of this project. In addition, this project will serve as a case study in philosophy of modeling, using it to apply and refine recent philosophical frameworks for modeling and simulation (Abelson, Gallagher, Smeenk, Jacquart, Meskhidze).