The abundance discrepancy factor and t2 in nebulae: Are non-thermal electrons the culprits?

G. J. Ferland, W. J. Henney, C. R. O'Dell, M. Peimbert

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


We discuss recent claims that the free electrons in ionized nebulae may not have a significantly Maxwellian velocity distribution. Supra-thermal electrons, electrons with much more energy than is encountered at electron temperatures found in nebulae, may solve the t2/ADF puzzle, the observations that abundances obtained from recombination and collisionally excited lines do not agree, and that different temperature indicators give different results. These non-Maxwellian electrons can be designated by the kappa formalism. We show that the distance over which heating rates change are much longer than the distance supra-thermal electrons can travel, and that the timescale to thermalize these electrons are much shorter than the heating or cooling timescales. These estimates show that supra-thermal electrons will have disappeared into the Maxwellian velocity distribution long before they affect the collisionally-excited forbidden and recombination lines, so the electron velocity distribution will be closely thermal.

Original languageEnglish
Pages (from-to)261-269
Number of pages9
JournalRevista Mexicana de Astronomia y Astrofisica
Issue number2
StatePublished - Oct 2016


  • Atomic processes
  • Galaxies: active
  • Methods: numerical
  • Molecular processes
  • Radiation mechanisms

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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