Dust and molecules in extra-galactic planetary nebulae

TL;DR

This paper reviews how dust and molecules in extra-galactic planetary nebulae vary with metallicity, highlighting the impact on dust production and complex organic molecule formation in different galactic environments.

Contribution

It provides a comparative observational analysis of dust and molecular content in extra-galactic versus Galactic planetary nebulae, emphasizing metallicity effects.

Findings

Lower metallicity environments have reduced dust production.

Higher frequency of complex molecules like fullerenes in low-metallicity PNe.

Metallicity influences dust processing and organic molecule formation.

Abstract

Extra-galactic planetary nebulae (PNe) permit the study of dust and molecules in metallicity environments other than the Galaxy. Their known distances lower the number of free parameters in the observations vs. models comparison, providing strong constraints on the gas-phase and solid-state astrochemistry models. Observations of PNe in the Galaxy and other Local Group galaxies such as the Magellanic Clouds (MC) provide evidence that metallicity affects the production of dust as well as the formation of complex organic molecules and inorganic solid-state compounds in their circumstellar envelopes. In particular, the lower metallicity MC environments seem to be less favorable to dust production and the frequency of carbonaceous dust features and complex fullerene molecules is generally higher with decreasing metallicity. Here, I present an observational review of the dust and molecular content in extra-galactic PNe as compared to their higher metallicity Galactic counterparts. A special attention is given to the level of dust processing and the formation of complex organic molecules (e.g., polycyclic aromatic hydrocarbons, fullerenes, and graphene precursors) depending on metallicity.