I. McNabb (1), X. Fang (1), X.-W. Liu (1,2), P.J. Storey (3)
(1) Kavli Institute of Astronomy and Astrophysics at Peking University. (2) Department of Astronomy at Peking University. (3) Department of Physics and Astronomy at University College London
We carry out plasma diagnostic analysis for a number of planetary nebulae (PNe) and H II regions. We use N II and O II optical recombination lines (ORLs) with new effective recombination coefficients calculated under the intermediate coupling scheme, for a range of electron temperatures (Te) and densities (Ne) and fitted against the most reliable measurements. Comparing Te derived from ORLs, collisionally excited lines (CELs), the hydrogen Balmer Jump, and/or He I if available, we find the relation Te (ORLs) < Te (He I) < Te (H I BJ) < Te (CELs), confirming the physical conditions in the two-abundance model postulated by Liu et al. (2000), i.e. the nebula contains another cold, metal-rich and probably H-deficient component.
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