Speaker
Description
Achieving robust cosmological constraints from cosmic shear involves several stages and many different analysis choices. Recent galaxy weak lensing analyses (DES & KiDS 2023) have shown that small shifts in parameter constraints are exacerbated by some combinations of analysis choices. As constraining power from cosmic shear improves, more complex modelling and accounting of systematics is required. Galaxy lensing is affected by baryonic feedback, primarily through active galactic nuclei redistributing matter at the centre of galaxies, when measuring small scales. We have performed a full mock-Rubin cosmic shear analysis and have found that removing data that is strongly affected by baryonic feedback would mean excluding almost 80% of the data, however marginalising over baryonic feedback parameters without any external information leads to minimal improvements in constraining power. This is because data from the Rubin Observatory is so precise that even a small effect is detectable. For baryon systematics we are currently dependent on cosmological hydrodynamical simulations, however cross-correlations with external probes such as X-ray or CMB measurements provide a more direct way to constrain baryons. We will present results on the potential impact of baryons on cosmic shear with Rubin Observatory and the interplay between baryons and other cosmic shear systematics.