Imaging the elusive H-poor gas in planetary nebulae with large abundance discrepancy factors

TL;DR

This study investigates the origin of abundance discrepancies in planetary nebulae, linking large discrepancies to binary star evolution and revealing that ORL emissions are more centrally concentrated than CELs.

Contribution

It provides observational evidence connecting abundance discrepancies to binary central stars and demonstrates the spatial distribution differences of emission lines in planetary nebulae.

Findings

Largest abundance discrepancies are associated with close binary central stars.

O II ORL emission is more centrally concentrated than [O III] CELs.

Binary evolution may influence the abundance discrepancy phenomenon.

Abstract

The discrepancy between abundances computed using optical recombination lines (ORLs) and collisionally excited lines (CELs) is a major, unresolved problem with significant implications for the determination of chemical abundances throughout the Universe. In planetary nebulae (PNe), the most common explanation for the discrepancy is that two different gas phases coexist: a hot component with standard metallicity, and a much colder plasma enhanced in heavy elements. This dual nature is not predicted by mass loss theories, and direct observational support for it is still weak. In this work, we present our recent findings that demonstrate that the largest abundance discrepancies are associated with close binary central stars. OSIRIS-GTC tunable filter imaging of the faint O II ORLs and MUSE-VLT deep 2D spectrophotometry confirm that O II ORL emission is more centrally concentrated than that of [O III] CELs and, therefore, that the abundance discrepancy may be closely linked to binary evolution.