Large Magellanic Cloud planetary nebula morphology: Probing stellar populations and evolution

Planetary nebulae (PNe) in the Large Magellanic Cloud (LMC) offer the uniqu e opportunity to study both the population and evolution of low- and interm ediate-mass stars, by means of the morphological type of the nebula. Using observations from our LMC PN morphological survey, and including images ava ilable in the Hubble Space Telescope Data Archive and published chemical ab undances, we find that asymmetry in PNe is strongly correlated with a young er stellar population, as indicated by the abundance of elements that are u naltered by stellar evolution (Ne, Ar, and S). While similar results have b een obtained for Galactic PNe, this is the first demonstration of the relat ionship for extragalactic PNe, We also examine the relation between morphol ogy and abundance of the products of stellar evolution. We found that asymm etric PNe have higher nitrogen and lower carbon abundances than symmetric P Ne. Our two main results are broadly consistent with the predictions of ste llar evolution if the progenitors of asymmetric PNe have on average larger masses than the progenitors of symmetric PNe. The results bear on the quest ion of formation mechanisms for asymmetric PNe-specifically, that the genes is of PNe structure should relate strongly to the population type, and by i nference the mass, of the progenitor star and less strongly on whether the central star is a member of a close binary system.