The case of NGC 6302: The impact of shocks in the derivation of Nitrogen abundances

TL;DR

This study investigates the role of shocks in the excitation and nitrogen abundance determination of the planetary nebula NGC 6302, revealing shocks' significance and proposing revised abundance calculation methods.

Contribution

It demonstrates the importance of shocks in NGC 6302 and challenges standard abundance derivation assumptions, providing a new distance estimate.

Findings

Shocks are significant in the nebula's peripheral regions.

Standard ICF methods may underestimate nitrogen abundances.

A new distance of 805±143 pc for NGC 6302 is proposed.

Abstract

High nitrogen abundance is characteristic of Type I planetary nebulae as well as their highly filamentary structure. In the present work we test the hypothesis of shocks as a relevant excitation mechanism for a Type-I nebula, NGC 6302, using recently released diagnostic diagrams to distinguish shocks from photoexcitation. The construction of diagrams depends on emission line ratios and kinematical information. NGC 6302 shows the relevance of shocks in peripheral regions and the importance to the whole nebula. Using shocks, we question the usual assumption of ICF calculation, justifying a warning to broadly used abundance derivation methods. From a kinematical analysis, we derive a new distance for NGC 6302 of $805\pm143\,$ pc.