Public seminar of MPhil Candidate:- Planetary Nebulae in the Galactic Bulge
Planetary Nebulae(PNe) are gaseous layers and dust shrouding dying stars with low- and intermediate-masses, showing predominant emission lines. With the advancement of wide-field and high-precision telescopes, e.g., the Hubble Space Telescope(HST) and the European Southern Observatory’s Very Large Telescope(ESO VLT), both high-resolution images and long-slit spectra became available for a growing sample of PNe. This allows an improvement in our understanding of both the formation of PNe, including the evolutionary history, mass-loss physics, and chemical evolution of their progenitors, furthermore, to analyse the chemical environment in which their progenitors were born. This could give powerful insights into the chemical evolution of the galaxies they reside. This MPhil project aims to make full use of the observation of 138 PNe in the Galactic bulge from the ESO 8.2mVLT. This set of observational data is comprised of high-resolution images and long-slit spectroscopic observations.
With the imaging data, the morphologies, position angles, as well as central star visibilities of PNe in the sample, were investigated in combination with the HST imagery where available. The excellent resolving power of the VLT and HST reveals many never-seen-before morphological features and central stars of PNe.
With the long-slit spectroscopic observations, the chemical abundances of this PN sample were derived after a careful data reduction. The oxygen abundance was then used as a metallicity indicator of their progenitors. An analysis of PN spatial distribution, oxygen abundance gradient and abundance distribution function was carried out to trace the origin of the Galactic bulge. Besides, weak optical recombination lines detected in the spectra allow a determination of the abundance discrepancy in this PN sample. Different nebular and central star properties were investigated to seek possible explanations to this discrepancy. The results confirm the like between ADFs and central star binarity, suggest possible relationships between ADFs, chemical abundances and electron densities noticed in previous studies.
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