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Register a new userAn Optical Emission Line Survey of Large Planetary Nebulae
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G.J. Madsen
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Accurate emission line fluxes from planetary nebulae (PNe) provide important constraints on the nature of the final phases of stellar evolution. Large, evolved PNe may trace the latest stages of PN evolution, where material from the AGB wind is returned to the interstellar medium. However, the low surface brightness and spatially extended emission of large PNe have made accurate measurements of line fluxes difficult with traditional long-slit spectroscopic techniques. Furthermore, distinguishing these nebulae from HII regions, supernova remnants, or interstellar gas ionized by a hot, evolved stellar core can be challenging. Here, we report on an ongoing survey of large Galactic PNe (r > 5) with the Wisconsin H-Alpha Mapper (WHAM), a Fabry-Perot spectrograph designed to detect faint diffuse optical emission lines with high sensitivity and spectral resolution. Our sample includes newly revealed H-alpha enhancements from the AAO/UKST and WHAM H-alpha surveys of Parker et al. and Haffner et al. We present accurate emission line fluxes of H-alpha, [NII], and [OIII], and compare our data to other measurements. We use the emission line ratios and kinematics of the ionized gas to assess, or in some cases reassess, the identification of some nebulae.
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The Planetary Nebulae (PNe) return nuclear processed stellar material back to the interstellar medium (ISM) and thus have an important influence on the chemical evolution of our Galaxy. We present results of a survey of PNe in decay which have reached a density comparable to the ambient ISM which leads to an interaction with it. This gives us the opportunity to investigate properties of the ISM. We have identified about 20 new examples for this interaction, demonstrating that it is a more common phenomenon than previously expected: Different stages of interaction, ranging from the early (asymmetric brightness distribution) to the very advanced (parabolic or distorted shape and/or an off-center central star) are obvious.
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