Origin of Cosmic Chemical Abundances

Umberto Maio, Edoardo Tescari
(Submitted on 11 Sep 2015)

Cosmological N-body hydrodynamic computations following atomic and molecular chemistry (e, H, H+, H, He, He+, He++, D, D+, H2, H+2, HD, HeH+), gas cooling, star formation and production of heavy elements (C, N, O, Ne, Mg, Si, S, Ca, Fe, etc.) from stars covering a range of mass and metallicity are used to explore the origin of several chemical abundance patterns and to study both the metal and molecular content during simulated galaxy assembly. The resulting trends show a remarkable similarity to up-to-date observations of the most metal-poor damped Lyman- absorbers at redshift z2. These exhibit a transient nature and represent collapsing gaseous structures captured while cooling is becoming effective in lowering the temperature below 104K, before they are disrupted by episodes of star formation or tidal effects. Our theoretical results agree with the available data for typical elemental ratios, such as [C/O], [Si/Fe], [O/Fe], [Si/O], [Fe/H], [O/H] at redshifts z27. Correlations between HI and H2 abundances show temporal and local variations and large spreads as a result of the increasing cosmic star formation activity from z6 to z3. The scatter we find in the abundance ratios is compatible with the observational data and is explained by simultaneous enrichment by sources from different stellar phases or belonging to different stellar populations. Simulated synthetic spectra support the existence of metal-poor cold clumps with large optical depth at z6 that could be potential population~III sites at low or intermediate redshift. The expected dust content is in line with recent determinations.

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:1509.03637 [astro-ph.CO]
(or arXiv:1509.03637v1 [astro-ph.CO] for this version)
Submission history
From: Umberto Maio PhD
[v1] Fri, 11 Sep 2015 20:04:37 GMT (1717kb)
http://arxiv.org/abs/1509.03637