The Oxygen Abundance in the Solar Neighborhood

TL;DR

This study analyzes oxygen abundances in nearby H II regions and planetary nebulae, revealing overabundance in PNe and proposing dust-related explanations to reconcile different abundance measurements.

Contribution

It provides a homogeneous analysis of oxygen in local nebulae and introduces a dust component hypothesis to explain abundance discrepancies.

Findings

PNe are overabundant in oxygen by about 0.2 dex.

Reconciliation of abundance measurements suggests a refractory dust component in H II regions.

The presence of organic refractory dust explains oxygen depletion in different environments.

Abstract

We present a homogeneous analysis of the oxygen abundance in five H II regions and eight planetary nebulae (PNe) located at distances lower than 2 kpc and with available spectra of high quality. We find that both the collisionally excited lines and recombination lines imply that the PNe are overabundant in oxygen by about 0.2 dex. An explanation that reconciles the oxygen abundances derived with collisionally excited lines for H II regions and PNe with the values found for B-stars, the Sun, and the diffuse ISM requires the presence in H II regions of an organic refractory dust component that is not present in PNe. This dust component has already been invoked to explain the depletion of oxygen in molecular clouds and in the diffuse interstellar medium.