Abstract
Collisionless simulations of structure formation with significant local primordial non-Gaussianities at Mpc scales have shown that a non-Gaussian tail favouring underdensities, with a negative fNL parameter, can significantly change the merging history of galaxy-sized dark matter halos, which then typically assemble later than in vanilla ΛCDM. Moreover, such a small-scale negative fNL could have interesting consequences for the cosmological S8 tension. Here, we complement our previous work on collisionless simulations with new hydrodynamical simulations of galaxy formation in boxes of 30 Mpc/h, using the RAMSES code. In particular, we show that all feedback prescriptions being otherwise identical, simulations with a negative fNL ∼ -1000 on small scales, hence forming galaxies a bit later than in vanilla ΛCDM, allow to form simulated galaxies with more disky kinematics than in the vanilla case. Therefore, such small-scale primordial non-Gaussianities could potentially help alleviate, simultaneously, tensions in cosmology and galaxy formation. These hydrodynamical simulations on small scales will need to be complemented with larger box simulations with scale-dependent non-Gaussianities, to statistically confirm these trends and explore their observational consequences in further detail.