TITLE:
Cosmological production of H2 before the formation of the first galaxies
AUTHOR(S):
Christopher M. Hirata (IAS) and Nikhil Padmanabhan (Princeton).
DATE:
2006 Jun 19 (arXiv, v1, posted); 2006 Jun 19 (MNRAS, submitted); 2006 Aug 07 (MNRAS, accepted);
2006 Sep 22 (MNRAS, published).
AVAILABILITY:
arXiv astro-ph/0606437 (free);
Blackwell-Synergy
(requires subscription).
PUBLICATION INFORMATION: Mon. Not. R. Astron. Soc., 372, 1175--1186, 2006.
ABSTRACT:
Previous calculations of the pregalactic chemistry have found that a small amount of H2, x[H2]=n[H2]/n[H] =
2.6x10-6, is produced catalytically through the H-, H2+, and HeH+ mechanisms. We revisit this
standard calculation taking into account the effects of the nonthermal radiation background produced by cosmic hydrogen recombination, which is
particularly effective at destroying H- via photodetachment. We also take into consideration the non-equilibrium level populations of
H2+, which occur since transitions among the rotational-vibrational levels are slow compared to photodissociation. The new
calculation predicts a final H2 abundance of x[H2] = 6x10-7 for the standard cosmology. This production is due almost
entirely to the H- mechanism, with ~1 per cent coming from HeH+ and ~0.004 per cent from H2+. We evaluate
the heating of the diffuse pregalactic gas from the chemical reactions that produce H2 and from rotational transitions in H2, and
find them to be negligible.
ADS BIBLIOGRAPHIC CODE: 2006MNRAS.372.1175H
COMMENTS: N/A.