Abstract
Liu et al. (1995) and Luo, Liu & Barlow (2001) determined the CNONe abundances in NGC 7009 using optical recombination lines (ORLs) and found that they are all approximately a factor of five higher than the corresponding values derived from collisionally excited lines (CELs). We have obtained new deep high resolution long-slit spectra of NGC 7009. The data have been used to map the electron temperature, density and element abundances across the nebula, using both CELs and ORLs. While the electron temperature derived from the [O III] forbidden line ratio, Te([O III]), is found to be largely constant, that derived from Balmer jump of H I recombination spectrum, Te(BJ), shows large amplitude complicated variations. The ratios of the heavy element abundances derived from ORLs to those deduced from CELs are found to be correlated with the difference between the difference between Te([O III]) and Te(BJ) – a relation previously known to exist from analyses of the integration spectra of individual nebulae (Liu et al. 2001).
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