Hydrodynamical simulations of galaxy formation with non-Gaussian initial conditions

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 f _NL 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 f _NL could have interesting consequences for the cosmological S ₈ 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 f _NL ∼ -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.