The H$\alpha$ surface brightness $-$ radius plane as a diagnostic tool for photoionized nebulae

TL;DR

The paper demonstrates that the H-alpha surface brightness-radius ($S-r$) plane effectively distinguishes different photoionized nebulae types and can serve as a diagnostic tool for classification and distance estimation.

Contribution

It extends the $S-r$ relation to various nebulae types, showing their distinct loci and potential for developing new distance indicators, especially for massive star ejecta.

Findings

Different nebulae occupy distinct regions in the $S-r$ plane.

The $S-r$ relation can classify nebulae types in galaxy surveys.

Potential for new distance indicators for massive star ejecta.

Abstract

The H$\alpha$ surface brightness $-$ radius ($S-r$) relation is a robust distance indicator for planetary nebulae (PNe), further enhanced by different populations of PNe having distinct loci in $S-r$ space. Other types of photoionized nebulae also plot in quite distinct regions in the $S-r$ plane, allowing its use as a diagnostic tool. In particular, the nova shells and massive star ejecta (MSE) plot on relatively tight loci illustrating their evolutionary sequences. For the MSE, there is potential to develop a distance indicator for these objects, based on their trend in $S-r$ space. As high-resolution, narrowband surveys of the nearest galaxies become more commonplace, the $S-r$ plane is a potentially useful diagnostic tool to help identify the various ionized nebulae in these systems.