The FLAMINGO project: the coupling between baryonic feedback and cosmology in light of the $S_8$ tension

Understand

Large-scale structure surveys have reported measurements of the density of matter, $\Omega_\mathrm{m}$, and the amplitude of clustering, $\sigma_8$, that are in tension with the values inferred from observations of the cosmic microwave background.

• While this may be a sign of new physics that slows the growth of structure at late times, strong astrophysical feedback processes could also be responsible.
• In this work, we argue that astrophysical processes are not independent of cosmology and that their coupling naturally leads to stronger baryonic feedback in cosmological models with suppressed structure formation or when combined with a mechanism that removes dark matter from halos.
• We illustrate this with two well-motivated extensions of the Standard Model known to suppress structure formation: massive neutrinos and decaying dark matter.