Gas distribution, metal enrichment and baryon fraction in Gaussian and non-Gaussian universes

Abstract

We study the cosmological evolution of baryons in universes with and without primordial non-Gaussianities via N-body/hydrodynamical simulations, including gas cooling, star formation, stellar evolution, chemical enrichment from both population III and population II regimes, and feedback effects. We find that large fNL values for non-Gaussianities can alter the gas probability distribution functions, the metal pollution history, the halo baryon, gas and stellar fractions, mostly at early times. More precisely, (i) non-Gaussianities lead to an earlier evolution of primordial gas, structures and star formation; (ii) metal enrichment starts earlier (with respect to the Gaussian scenario) in non-Gaussian models with larger fNL; (iii) gas fractions within the haloes are not significantly affected by the different values of fNL, with deviations of ∼1–10%; (iv) the stellar fraction is quite sensitive to non-Gaussianities at early times, with discrepancies reaching up to a factor of ∼10 at very high z, and rapidly converging at low z; (v) the trends at low redshift are independent from fNL: they are mostly led by the ongoing baryonic evolution and by the feedback mechanisms, which determine a ∼25–30% discrepancy in the baryon fraction of galaxy groups/clusters with respect to the cosmic values; (vi) non-Gaussianity impacts on the cluster x-ray emission or on the Sunyaev–Zeldovic effect(s) are expected to be not very large and dominated by feedback mechanisms, whereas some effects on the 21 cm emission can be expected at early times; (vii) in order to address non-Gaussianities in the cosmological structure contest, high-redshift (z ∼ 10) investigations are required: first stars, galaxies, quasars and gamma-ray bursts may be potential cosmological probes of non-Gaussianities.