TY - JOUR
T1 - Role of the H+2 channel in the primordial star formation under strong radiation field and the critical intensity for the supermassive star formation
AU - Sugimura, K.
AU - Coppola, C. M.
AU - Omukai, K.
AU - Galli, D.
AU - Palla, F.
N1 - Publisher Copyright:
© 2015 The Authors.
PY - 2016/2/11
Y1 - 2016/2/11
N2 - 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.
AB - 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.
KW - Cosmology: theory
KW - Molecular processes
KW - Quasars: supermassive black holes
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U2 - 10.1093/mnras/stv2655
DO - 10.1093/mnras/stv2655
M3 - Article
AN - SCOPUS:84959577029
VL - 456
SP - 270
EP - 277
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 1
ER -