Modifying the unconstrained small-scale initial conditions of the Universe could be a game changer for our understanding of cosmic structure formation and help address challenges in small-scale galaxy formation. In this talk, I will present my investigations of the effects of significant small-scale primordial non-Gaussianities (PNG). I have found that such PNG introduce a distinct and potentially detectable feature in the matter power spectrum around the non-linear scale. This feature, combined with early dark energy, could potentially solve the H0 and S8 tensions simultaneously. In that case, the current cosmic tensions would stem entirely from pre-CMB physics. Moreover, PNG result in typical galaxy-sized halos reaching half of their present-day mass earlier and experiencing a quieter merging history for z<3 compared to the Gaussian case. This quieter merging history and less dense environment could have significant implications for the formation of bulges and bars in galaxies. Based on hydrodynamical simulations I conducted, I will show that, with all feedback prescriptions being otherwise identical, simulations with a positively skewed distribution form galaxies slightly later than in the standard ΛCDM model and lead to galaxies with more disky kinematics than in the standard case. Thus, such small-scale PNG could potentially help alleviate simultaneous tensions in cosmology and galaxy formation.
Location: bâtiment 709, salle Kepler
Local contact & organisation: Benjamin MAGNELLI
DAp