Abstract

FERLAND, G. J.; HENNEY, W. J.; O’DELL, C. R.  and  PEIMBERT, M.. The abundance discrepancy factor and t ² in nebulae: are non-thermal electrons the culprits?. Rev. mex. astron. astrofis [online]. 2016, vol.52, n.2, pp.261-269. ISSN 0185-1101.

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.

Keywords : atomic processes; galaxies: active; methods: numerical; molecular processes; radiation mechanisms.

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