HI and H$_2$ gas evolution over cosmic times: ColdSIM

U. Maio

doi:10.1051/epjconf/202225700029

paper

HI and H $_{2}$ gas evolution over cosmic times: ColdSIM

arXiv:2111.01804 · doi:10.1051/epjconf/202225700029

Abstract

We present first results of the evolution of cold cosmic gas obtained through a set of state-of-the-art numerical simulations (ColdSIM). We model time-dependent atomic and molecular non-equilibrium chemistry coupled to HI and H $_{2}$ self-shielding, various UV backgrounds as suggested by the recent literature, H $_{2}$ dust grain catalysis, photoelectric heating, cosmic-ray heating, as well as hydrodynamics, star formation and feedback effects. By means of such non-equilibrium calculations we are finally able to reproduce the latest HI and H $_{2}$ observational data. The neutral-gas mass density parameter results around $Ω_{neutral} \sim 1 0^{- 3}$ and increases from lower to higher redshift ( $z$ ). The molecular-gas mass density parameter shows peak values of $Ω_{H_{2}} \sim 1 0^{- 4}$ , while expected H $_{2}$ fractions can be as high as 50% of the cold gas mass at $z \sim$ 4-8, in line with the latest high- $z$ measurements. Both observed HI and H $_{2}$ trends are well reproduced by our non-equilibrium H $_{2}$ -based star formation modelling. H $_{2}$ depletion times remain below the Hubble time and comparable to the dynamical time at all epochs. These findings suggest that, besides HI, non-equilibrium H $_{2}$ analyses are key probes for assessing the cold gas and the role of UV background radiation. Abridged.

arXiv commentTo appear in the Proceedings of the International Conference entitled "mm Universe $@$ NIKA2", Rome (Italy), June 2021, EPJ Web of conferences

HI and H2​ gas evolution over cosmic times: ColdSIM

Abstract

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HI and H $_{2}$ gas evolution over cosmic times: ColdSIM