An overabundance of oxygen in planetary nebulae of the solar neighborhood

TL;DR

This study compares oxygen abundances in nearby H II regions and planetary nebulae, revealing a significant overabundance of oxygen in most planetary nebulae compared to the local interstellar medium, using high-quality spectral data.

Contribution

It provides a consistent analysis of oxygen abundances in local nebulae using uniform methods, highlighting the overabundance in planetary nebulae relative to H II regions.

Findings

H II regions show homogeneous oxygen abundance (12+log(O/H)=8.45-8.54)

Most planetary nebulae have higher oxygen abundances (12+log(O/H)=8.65-8.80)

Overabundance persists when using recombination line data

Abstract

We study the oxygen abundance in five H II regions and seven planetary nebulae (PNe) located within 2 kpc from the Sun that have available spectra of high quality. Our analysis uses a similar procedure and the same atomic data to derive abundances in all the objects. The results calculated with collisionally excited lines for the H II regions indicate that the local interstellar medium is very homogeneous, with 12+log(O/H)=8.45-8.54. As for the PNe, six out of seven show significantly higher abundances: 12+log(O/H)=8.65-8.80. This overabundance of oxygen in PNe also holds when we consider the abundances implied by recombination lines.