Unidentified infrared bands do not correlate with C/O ratio in planetary nebulae

TL;DR

This paper challenges the previously suggested correlation between unidentified infrared bands and the C/O ratio in planetary nebulae, showing that larger space-based datasets do not support a direct link.

Contribution

It demonstrates that the supposed correlation between UIB strength and C/O ratio in planetary nebulae is not supported by recent space-based observations, refuting prior claims.

Findings

Larger space-based data disprove the UIB and C/O ratio correlation.

Interstellar UIB carriers likely do not originate from carbon-rich PNe.

Previous air-born observations suggested a correlation that is not confirmed by newer data.

Abstract

The concrete evidence adduced to support the widely held idea that unidentified infrared bands (UIBs) are enhanced in carbon-rich planetary nebulae (PNe) is a remarkable UIB 7.7 {\mu}m versus C/O ratio correlation plot for six PNe, obtained from air-born observations and published in 1986 by M. Cohen and coworkers. However, the space-born data presented by Cohen & Barlow in 2005 undercut this correlation, and I show that the larger dataset they provide disproves a specific link between UIBs and carbon abundance in PNe. It also follows from these data that interstellar UIB carriers cannot originate from the atmosphere of carbon-rich PNe.