Molecules in the early Universe

TL;DR

This paper models the formation of molecules and ions in the early Universe, analyzing how uncertainties in cosmological parameters and recombination processes influence molecular abundances at high redshifts.

Contribution

It introduces a modified effective 3-level atom model for cosmological recombination and assesses the impact of parameter uncertainties on molecular abundances.

Findings

Molecular abundances are affected by 2-3% due to recombination inaccuracies.

Cosmological parameter uncertainties influence molecular abundances by up to 2%.

Specific abundance ratios at redshift z=10 are provided for various molecules.

Abstract

We study the formation of first molecules, negative Hydrogen ions and molecular ions in model of the Universe with cosmological constant and cold dark matter. The cosmological recombination is described in the framework of modified model of the effective 3-level atom, while the kinetics of chemical reactions in the framework of the minimal model for Hydrogen, Deuterium and Helium. It is found that the uncertainties of molecular abundances caused by the inaccuracies of computation of cosmological recombination are about 2-3%. The uncertainties of values of cosmological parameters affect the abundances of molecules, negative Hydrogen ions and molecular ions at the level of up to 2%. In the absence of cosmological reionization at redshift $z=10$ the ratios of abundances to the Hydrogen one are $3.08\times10^{-13}$ for $H^-$, $2.37\times10^{-6}$ for $H_2$, $1.26\times10^{-13}$ for $H_2^+$, $1.12\times10^{-9}$ for $HD$ and $8.54\times10^{-14}$ for $HeH^+$.