The imprint of cosmological non-Gaussianities on primordial structure formation

Abstract

We study via numerical N-body/smoothed particle hydrodynamics chemistry simulations the effects of primordial non-Gaussianities on the formation of the first stars and galaxies, and investigate the impact of supernova feedback in cosmologies with different f NL. Density distributions are biased to higher values, so star formation and the consequent feedback processes take place earlier in high-f NL models and later in low-f NL ones. Mechanical feedback is responsible for shocking and evacuating the gas from star-forming sites earlier in the highly non-Gaussian cases because of the larger bias at high densities. Chemical feedback translates into high-redshift metal filling factors that are larger by some orders of magnitude for larger f NL, but that converge within one Gyr, for both Population III and Population II-I stellar regimes. The efficient enrichment process, though, leads to metallicities >rsim 10 -2 Z ⊙ by redshift ~9, almost independently from f NL. The impact of non-Gaussianities on the formation of dark-matter haloes at high redshift is directly reflected in the properties of the gas in these haloes, as models with larger f NL show more concentrated gas profiles at early times. Non-Gaussian signatures in the gas behaviour are lost after the first feedback takes place and introduces a significant degree of turbulence and chaotic motions. Despite this, our results support the idea that non-Gaussianities can be imprinted in the gaseous and stellar features of primordial structures in the high-redshift Universe. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.