C +2 Electron Temperatures in Planetary Nebulae

Abstract

Electron temperatures are calculated for 30 planetary nebulae from the flux ratios of the C III] λ1909 and C II λ4267 lines, both of which are produced in the C⁺² zone of the nebula. These temperatures correlate much better with optical [O III] temperatures than they do with those derived from [N II], except for low central star temperatures. However, as calculated from currently available atomic parameters, the T_e(C⁺²) average is ≡2000K lower than T_e[O III]. Possible solutions for this discrepancy are discussed.