Testing atomic collision theory with the two-photon continuum of astrophysical nebulae

F. Guzmán, N. R. Badnell, M. Chatzikos, P. A. M. van Hoof, R. J. R. Williams, G. J. Ferland

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Abstract

Accurate rates for energy-degenerate l-changing collisions are needed to determine cosmological abundances and recombination. There are now several competing theories for the treatment of this process, and it is not possible to test these experimentally. We show that the H i two-photon continuum produced by astrophysical nebulae is strongly affected by l-changing collisions. We perform an analysis of the different underlying atomic processes and simulate the recombination and two-photon spectrum of a nebula containing H and He. We provide an extended set of effective recombination coefficients and updated l-changing 2s − 2p transition rates using several competing theories. In principle, accurate astronomical observations could determine which theory is correct.
Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Early online date1 Feb 2017
DOIs
Publication statusE-pub ahead of print - 1 Feb 2017

Keywords

  • cosmology
  • cosmic background
  • cosmic observations
  • atomic data
  • atomic processes
  • H ii regions
  • planetary nebulae

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