Poster abstract details
A Detailed Look at Chemical Abundances in Magellanic Cloud Planetary Nebulae
Abstract
We present an analysis of elemental abundances of He, N, O, Ne, S, and Ar in Magellanic Cloud planetary nebulae (PNe). We derived the abundances from a combination of deep, high dispersion optical spectra, space-based slitless optical spectra, as well as mid-IR spectra from the Spitzer Space Telescope and UV spectra from IUE and HST/STIS. Through the use of wider wavelength coverage, higher dispersion, and more accurate flux calibration, we have been able to derive elemental abundances which are among the most accurate available, and allow us to examine elemental yields in these low metalicity environments with greater precision than most studies have been able to achieve.
We used ionic abundances derived from IR emission lines, including those from ionization stages not observable in the optical, to examine the accuracy of some commonly used recipes for ionization correction factors (ICFs). We find that most of these ICFs work very well even in the limit of substantially sub-Solar metallicities, except for PNe with very high ionization. Our abundance analysis shows enhancements of He and N that are predicted from prior dredge-up processes of the progenitors on the AGB, and which agree well with expectations from nebular morphology. The derived elemental abundances for Ne, S, and Ar, which are not expected to change significantly from nucleosynthesis in the prior AGB phase, show significant dispersion with respect to the O abundance. In addition, the S and Ar abundances are systematically low compared to H~{\sc ii} regions in each galaxy, while the Ne abundance is on average elevated.
Finally, we identified MG~8 as an interesting limiting case of a PN central star with a $\approx3.5$~M$_\sun$ progenitor in which hot-bottom burning did not occur in its prior AGB evolution.
We used ionic abundances derived from IR emission lines, including those from ionization stages not observable in the optical, to examine the accuracy of some commonly used recipes for ionization correction factors (ICFs). We find that most of these ICFs work very well even in the limit of substantially sub-Solar metallicities, except for PNe with very high ionization. Our abundance analysis shows enhancements of He and N that are predicted from prior dredge-up processes of the progenitors on the AGB, and which agree well with expectations from nebular morphology. The derived elemental abundances for Ne, S, and Ar, which are not expected to change significantly from nucleosynthesis in the prior AGB phase, show significant dispersion with respect to the O abundance. In addition, the S and Ar abundances are systematically low compared to H~{\sc ii} regions in each galaxy, while the Ne abundance is on average elevated.
Finally, we identified MG~8 as an interesting limiting case of a PN central star with a $\approx3.5$~M$_\sun$ progenitor in which hot-bottom burning did not occur in its prior AGB evolution.