Planetary Nebulae Populations in External Galaxies

TL;DR

This review discusses how planetary nebulae in external galaxies serve as tools for understanding galaxy properties, including stellar populations, distances, and kinematics, with recent survey results highlighting their applications.

Contribution

It provides an overview of recent observational results on planetary nebulae in external galaxies, emphasizing their roles in galaxy kinematics, luminosity, and diffuse light tracing.

Findings

Kinematics of outer galaxy regions studied with planetary nebulae.

Luminosity-specific PN numbers (α parameter) analyzed in giant ellipticals.

Planetary nebulae effectively trace diffuse light in galaxy clusters.

Abstract

This review highlights the properties of the planetary nebulae in external galaxies as tracers of light, of the stellar population properties, and of the distances and kinematics of the parent galaxies. Recent results on the kinematics of the outer regions in giant elliptical galaxies and on the luminosity specific PN numbers (the \alpha\ parameter) in these systems are presented, based on current surveys of planetary nebulae with the Planetary Nebulae Spectrograph (PN.S) and other instruments. Finally a brief discussion is given of planetary nebulae as tracers of the diffuse light in the nearby clusters, such as Virgo and Hydra I.