Simulating extremely metal-poor gas and DLA metal content at redshift z ≃ 7

摘要: We present the first theoretical study of metals in damped-Ly α (DLA) systems at redshift z ≃ 7. The features cold, primordial gas are studied by means N-body, hydro, chemistry simulations, including atomic and molecular non-equilibrium chemistry, cooling, star formation for population III II-I regimes, stella r evolution, cosmic metal spreading according to proper yields (for He, C, O, Si, Fe, Mg, S, etc.) lifetimes, feedback effects. Theoretical expectations then compared recently available constraints from DLA observations. find that galaxies 7 account ∼ 10 per cent whole galaxy most metal-poor these epochs. About contain purely pristine material 34 them consist very weakly polluted gas, being, therefore, suitable candidates as pop ulation sites. remaining 59 enriched above −4 Z⊙. Additionally, appear have: masses . 2 × 8 M⊙; low rate, −3 − −2 M⊙/yr (significantly weaker than late-time counterparts); mean fractions covering a fairly wide range, xmol −6 ; typical metallicities Z 3 Z⊙ HI column densities NHI & 20 cm They no or weak correlations between their mass Z, NHI, xmol; moderate correlation linked ongoing moleculardriven pollution processes; mild anti-correlation xmol, due H depletion into molecules; chemical content is subject environmental dependencies.