Baryon history and cosmic star formation in non-Gaussian cosmological models: numerical simulations

TL;DR

This study uses advanced simulations to explore how primordial non-Gaussianities influence early universe chemistry, star formation, and chemical evolution, finding subtle effects that are often overshadowed by other physical processes.

Contribution

First numerical simulations of cosmic structure formation in non-Gaussian models, analyzing their impact on early chemistry, star formation, and chemical evolution.

Findings

Non-Gaussianities cause ~10% changes in early molecular fractions.

Temperature fluctuations during primordial evolution are less than 10%.

Onset of star formation and PopIII/PopII transition can be affected by non-Gaussianities.

Abstract

We present the first numerical, N-body, hydrodynamical, chemical simulations of cosmic structure formation in the framework of non-Gaussian models. We study the impact of primordial non-Gaussianities on early chemistry (e, H, H+, H-, He, He+, He++, H2, H2+, D, D+, HD, HeH+), molecular and atomic gas cooling, star formation, metal (C, O, Si, Fe, Mg, S) enrichment, population III (popIII) and population II-I (popII) transition, and on the evolution of "visible" objects. We find that non-Gaussianities can have some consequences on baryonic structure formation at very early epochs, but the subsequent evolution at later times washes out any difference among the various models. When assuming reasonable values for primordial non-Gaussian perturbations, it turns out that they are responsible for: (i) altering early molecular fractions in the cold, dense gas phase of ~10 per cent; (ii) inducing small temperature fluctuations of <~10 per cent during the cosmic evolution of primordial objects; (iii) influencing the onset of the first star formation events, at z>~15, and of the popIII/popII transition of up to some 10^7yr; (iv) determining variations of <~10 per cent in the gas cloud and stellar mass distributions after the formation of the first structures; (v) causing only mild variations in the chemical history of the Universe. We stress, though, that purely non-Gaussian effects might be difficult to address, since they are strictly twisted with additional physical phenomena (e.g. primordial gas bulk flows, unknown primordial popIII stellar mass function, etc.) that have similar or stronger impact on the behaviour of the baryons.