Electron Energy Distributions in H ii Regions and Planetary Nebulae: κ-distributions Do Not Apply

Abstract

Some authors have proposed that electron energy distributions in H ii regions and planetary nebulae may be significantly nonthermal, and κ -distributions have been suggested as being appropriate. Here it is demonstrated that the electron energy distribution function is extremely close to a Maxwellian up to electron kinetic energies of in H ii regions, and up to in planetary nebulae: κ -distributions are inappropriate. The small departures from a Maxwellian have negligible effects on line ratios. When observed line ratios in H ii regions deviate from models with a single electron temperature, it must arise from spatial variations in electron temperature, rather than local deviations from a Maxwellian.