Café-Club, Clément STAHL: “Exploring the effects of primordial non-Gaussianity at galactic scales”

Clément STAHL (Observatoire astronomique de Strasbourg): “Exploring the effects of primordial non-Gaussianity at galactic scales”.

You can find the schedule of upcoming café-clubs and the video of old ones here.

Take care,
Carlo, Meriam, Mathilde

—————-
ABSTRACT

In this talk, I will show you my investigation of the effect of significant small-scale primordial non-Gaussianity on structure formation and the galaxy formation process. Specifically, we explored four different types of non-Gaussianities: positive and negative skeweness and kurtosis. Generically, we find a distinct and potentially detectable feature in the matter power spectrum around the non-linear scale. The feature might have interesting consequences for the S8 tension. We then show in particular that a positively skewed distribution with fNL of the order of 1000 at these scales, implies
that typical galaxy-sized halos reach half of their present-day mass at an earlier stage. Building up galaxies earlier is highly relevant in the light the young massive galaxies observed by JWST. These galaxies have a quieter merging history at z < 3 than in the Gaussian case and their environment between 0.5 and 4 virial radii at z = 0 is less dense than in the Gaussian case. This quieter history and less dense environment has potentially interesting consequences in terms of the formation of bulges and bars. Moreover, we show that the two most massive subhalos around their host tend to display an interesting anti-correlation of velocities, indicative of kinematic coherence. Finally, all feedback prescriptions being otherwise identical,
simulations with a negative (positive) fNL on small scales, display a slightly more (less) disky kinematics than in the Gaussian case. All these hints will need to be statistically confirmed in larger-box simulations with scale-dependent non-Gaussian initial conditions, followed by hydrodynamical zoom-in simulations to explore the detailed consequences of small-scale non-Gaussianities on galaxy formation.