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A MULTIFACETED EXPLORATION OF PLANETARY NEBULAE
[Thesis]. Manchester, UK: The University of Manchester; 2013.
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Abstract
ABSTRACT OF THESIS submitted by Lizette Guzman-Ramirez for the Degree of Doctor of Philosophy and entitled “A Multifaceted Exploration of Planetary Nebulae”, November 2012.This thesis analyses and proposes solutions for the following PNe mysteries:1. The missing PNe population. 100 new objects were spectroscopically observed and analysed using the INT Photometric Halpha Survey (IPHAS). 32 are PNe, 13 are possible PNe and the rest are HII regions, SNR and unclear objects. The new PNe were within the inner parts of the galactic plane. The IPHAS survey has been the deepest survey done in Halpha, and revealed objects never seen before.2. The mixed chemistry in Galactic Bulge PNe. These GBPNe are the end-products of low-mass stars (and therefore expected to be O-rich) and belong to a metal rich population. These PNe present dual-dust chemistry, with the presence of PAHs (carbon-rich) and crystalline silicates (oxygen-rich) in their spectra. This thesis analysed 40 Galactic Bulge PNe and found a strong correlation between intensity of the PAH bands and morphology, notably a massive torus. This torus provides the dense irradiated environment needed to form the PAHs. Follow-up observations using VISIR revealed a dense dusty tori in 11 PNe. PAHs are present in the outer edges of these tori, whereas ionised material is located within the dusty tori.3. The 3He problem. Using the VLA we observed three PNe, upper-limits of their 3He abundances were estimated. The resulting evolution of 3He is only consistent with the values determined in pre-solar material and the ISM, if the PNe observed represent only 4% of the population of low-mass stars, and the remaining 96% have undergone enhanced 3He depletion.