Evolution of Planetary Nebulae with WR-type Central Stars

Abstract

Bibliography: pages 387-442.%%%%Chapter 1. Introduction – Part I. Planetary nebulae with [WC] stars – Chapter 2. Spatially resolved kinematics – Chapter 3. Physical conditions and chemical abundances – Chapter 4. Hb 4: a planetary nebula with FLIERs – Part II. Planetary nebulae with [WN] stars – Chapter 5. Abell 48 with a [WN]-type star – Chapter 6. PB 8 with a [WN/WC]-type star – Part III. Planetary nebulae with PG 1159-type stars – Chapter 7. SuWt 2 with a PG 1159-type star – Chapter 8. Conclusions and Future Work – References – Part IV. Appendices%%%%In this thesis I present a study of the kinematics, physical conditions and chemical abundances for a sample of Galactic planetary nebulae (PNe) with Wolf-Rayet (WR) and weak emission-line stars (wels), based on optical integralfield unit (IFU) spectroscopy obtained with the Wide Field Spectrograph (WiFeS) on the Australian National University 2.3 telescope at Siding Spring Observatory, and complemented by spectra from the literature. PNe surroundingWR-type stars constitute a particular study class for this study. A considerable fraction of currently well-identified central stars of PNe exhibit ‘hydrogendeficient’ fast expanding atmospheres characterized by a large mass-loss rate.Most of them were classified as the carbon-sequence and a few of them as the nitrogen-sequence of the WR-type stars. What is less clear are the physical mechanisms and evolutionary paths that remove the hydrogen-rich outerlayer from these degenerate cores, and transform it into a fast stellar wind. The aim of this thesis is to determine kinematic structure, density distribution, thermal structure and elemental abundances for a sample of PNe with differenthydrogen-deficient central stars, which might provide clues about the origin and formation of their hydrogen-deficient stellar atmospheres.%%%%The Hɑ and [N II] emission features were used to measure the nebular radial velocities. Based on the spatially resolved velocity distributions of these emission lines combined with archival Hubble Space Telescope imaging for compact PNe, the kinematic structures of these PNe were determined. Comparing the velocity maps observed by the IFU spectrograph with those predicted by morpho-kinematic models excluded the projection effect from the nebula’s appearanceand identified the morphology of most PNe, apart from the compact objects. The results indicate that these PNe have axisymmetric morphologies, either bipolar or elliptical. In many cases, the associated kinematic maps for PNe around hot WR-type stars also show the presence of so-called fast lowionization emission regions (FLIERs).%%%%The WiFeS observations, complemented with archival spectra from the literature, have been used to carry out plasma diagnostics and abundance analysis using both collisionally excited lines (CELs) and optical recombination lines(ORLs). ORL abundances for carbon, nitrogen and oxygen have been derived where adequate recombination lines were available. The weak temperature dependence of ORLs has also been used to…