Testing primordial non-Gaussianities on galactic scales at high redshift

TL;DR

This study investigates how primordial non-Gaussianities influence high-redshift galaxy formation by running simulations, revealing significant deviations in halo and galaxy mass functions that could impact understanding of cosmic reionization.

Contribution

The paper demonstrates the effect of local non-Gaussianity on galaxy formation at high redshift through cosmological simulations consistent with Planck constraints.

Findings

Non-Gaussian initial conditions cause >0.3 dex increase in low-mass halo abundance at z>10.

Altered halo mass functions lead to changes in galaxy stellar mass functions.

Results suggest potential observable signatures in future high-redshift galaxy surveys.

Abstract

Primordial non-Gaussianities provide an important test of inflationary models. Although the Planck CMB experiment has produced strong limits on non-Gaussianity on scales of clusters, there is still room for considerable non-Gaussianity on galactic scales. We have tested the effect of local non-Gaussianity on the high redshift galaxy population by running five cosmological N-body simulations down to z=6.5. For these simulations, we adopt the same initial phases, and either Gaussian or scale-dependent non-Gaussian primordial fluctuations, all consistent with the constraints set by Planck on clusters scales. We then assign stellar masses to each halo using the halo - stellar mass empirical relation of Behroozi et al. (2013). Our simulations with non-Gaussian initial conditions produce halo mass functions that show clear departures from those obtained from the analogous simulations with Gaussian initial conditions at z>~10. We observe a >0.3 dex enhancement of the low-end of the halo mass function, which leads to a similar effect on the galaxy stellar mass function, which should be testable with future galaxy surveys at z>10. As cosmic reionization is thought to be driven by dwarf galaxies at high redshift, our findings may have implications for the reionization history of the Universe.