Non-equilibrium H${}_2$ formation in the early Universe: energy exchanges, rate coefficients and spectral distortions

Abstract

Energy exchange processes play a crucial role in the early Universe, affecting the thermal balance and the dynamical evolution of the primordial gas. In the present work we focus on the consequences of a non-thermal distribution of the level populations of H${}_2$: first, we determine the excitation temperatures of vibrational transitions and the non-equilibrium heat transfer; second, we compare the modifications to chemical reaction rate coefficients with respect to the values obtained assuming local thermodynamic equilibrium; third, we compute the spectral distortions to the cosmic background radiation generated by the formation of H${}_2$ in vibrationally excited levels. We conclude that non-equilibrium processes cannot be ignored in cosmological simulations of the evolution of baryons, although their observational signatures remain below current limits of detection. New fits to the equilibrium and non-equilibrium heat transfer functions are provided.

7 pages, 6 figures; accepted by ApJS

References in corpus (9)

• Lines in the cosmic microwave background spectrum from the epoch of cosmological helium recombination
• Cosmological hydrogen recombination: populations of the high level sub-states
• Two-photon transitions in hydrogen and cosmological recombination
• Effects of primordial chemistry on the cosmic microwave background
• Vibrational level population of H${}_2$ and H${}_2^{+}$ in the early Universe
• Radiative cooling functions for primordial molecules
• Cosmological production of H_2 before the formation of the first galaxies
• Cosmological hydrogen recombination: Lyn line feedback and continuum escape
• Supermassive Black Hole Formation at High Redshifts Through a Primordial Magnetic Field

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• Non-thermal photons and H2 formation in the early Universe
• Fragmentation inside atomic cooling haloes exposed to Lyman-Werner radiation
• The CH+ Abundance in Turbulent, Diffuse Molecular Clouds
• Positive or Negative? The Impact of X-ray Feedback on the Formation of Direct Collapse Black Hole Seeds
• Monte Carlo calculation of the translational relaxation of superthermal H atoms in thermal H2 gas
• Temperature and density dependent cooling function for H${}_2$ with updated H${}_2$/H collisional rates
• Non-thermal photons and direct photodissociation of H2, HD and HeH+ in the chemistry of the primordial Universe
• Rydberg States of H${}_3$ and HeH as Potential Coolants for Primordial Star Formation