Co-spatial UV-optical HST/STIS Spectra of Six Planetary Nebulae: Nebular and Stellar Properties

TL;DR

This study uses HST/STIS spectra and photoionization models to analyze six planetary nebulae, confirming their chemical homogeneity and constraining central star properties with minimal sensitivity to density profile assumptions.

Contribution

It provides the first comprehensive spatially-resolved chemical abundance analysis and refined stellar property constraints for six planetary nebulae.

Findings

Nebular abundances are consistent with chemical homogeneity.

Central star temperature and luminosity are only slightly affected by density profile choice.

Mass estimates align with post-AGB evolutionary models.

Abstract

This paper represents the conclusion of a project that had two main goals: (1) to investigate to what extent planetary nebulae (PNe) are chemically homogeneous; and (2) to provide physical constraints on the central star properties of each PN. We accomplished the first goal by using HST/STIS spectra to measure the abundances of seven elements in numerous spatial regions within each of six PN (IC 2165, IC 3568, NGC 2440, NGC 5315, NGC 5882, and NGC 7662). The second goal was achieved by computing a photoionization model of each nebula, using our observed emission line strengths as constraints. The major finding of our study is that the nebular abundances of He, C, N, O, Ne, S, and Ar are consistent with a chemically homogeneous picture for each PN. Additionally, we found through experimenting with three different density profiles (constant, Gaussian, and Gaussian with a power-law) that the determination of the central star's temperature and luminosity is only slightly sensitive to the profile choice. Lastly, post-AGB evolutionary model predictions of temperature and luminosity available in the literature were plotted along with the values inferred from the photoionization model analysis to yield initial and final mass estimates of each central star.