Role of the H+2 channel in the primordial star formation under strong radiation field and the critical intensity for the supermassive star formation

K. Sugimura, C. M. Coppola, K. Omukai, D. Galli, F. Palla

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

We investigate the role of the H+2 channel on H2 molecule formation during the collapse of primordial gas clouds immersed in strong radiation fields which are assumed to have the shape of a diluted blackbody spectra with temperature Trad. Since the photodissociation rate of H+2 depends on its level population, we take full account of the vibrationally resolved H+2 kinetics.We find that in clouds under soft but intense radiation fields with spectral temperature Trad ≲ 7000 K, the H+2 channel is the dominant H2 formation process. On the other hand, for harder spectra with Trad ≳ 7000 K, the H- channel takes over H+2 in the production of molecular hydrogen.We calculate the critical radiation intensity needed for supermassive star formation by direct collapse and examine its dependence on the H+2 level population. Under the assumption of local thermodynamic equilibrium (LTE) level population, the critical intensity is underestimated by a factor of a few for soft spectra with Trad ≲ 7000 K. For harder spectra, the value of the critical intensity is not affected by the level population of H+2 . This result justifies previous estimates of the critical intensity assuming LTE populations since radiation sources like young and/or metal-poor galaxies are predicted to have rather hard spectra.

Original languageEnglish
Pages (from-to)270-277
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Volume456
Issue number1
DOIs
Publication statusPublished - 2016 Jan 1

Keywords

  • Cosmology: theory
  • Molecular processes
  • Quasars: supermassive black holes

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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