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Baryonic Feedback: the Impact of Galaxy Formation Physics on Cosmology

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Extracting accurate cosmology from weak lensing surveys requires accurate modelling of the matter power spectrum, including the non-linear scales which are affected by baryonic processes. Hydrodynamical simulations have demonstrated that energetic feedback processes, arising predominantly from AGN , suppress the non-linear matter power spectrum. However, the amplitude, redshift and scale dependence of this suppression remains largely unknown. A more complete understanding of baryonic feedback processes and its degeneracies with cosmological parameters is therefore crucial to make progress in the field. In this talk, I will describe my work which explores baryonic feedback from two viewpoints. The first project tests modifications to the AGN feedback model in the FABLE suite of cosmological hydrodynamical simulations. I will discuss extreme baryonic feedback as a possible solution to the ‘S8 tension’ and present the development of a new empirical AGN feedback model which predicts an increased suppression of the matter power spectrum. The second project I will discuss assesses standard and new methods of mitigating for baryonic feedback in cosmic shear analyses using the Dark Energy Survey Y3 cosmic shear dataset. I present a comparison of the approaches by considering the impact on the cosmological parameters and the constraints on the power spectrum suppression. Finally, I will demonstrate that the kinematic Sunyaev-Zel’dovich (kSZ) effect provides a promising avenue for understanding baryonic feedback in a new regime and can be effectively utilised in a joint shear+kSZ analysis to better constrain feedback parameters.

This talk is part of the Institute of Astronomy Seminars series.

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