The Fornax 3D project: PNe populations and stellar metallicity in edge-on galaxies

TL;DR

This study investigates how stellar metallicity influences planetary nebulae populations in edge-on galaxies, revealing that PNe abundance does not significantly vary between metal-rich and metal-poor regions, emphasizing the importance of spatial consistency in such analyses.

Contribution

It provides new insights into the relationship between stellar metallicity and PNe populations using integral-field spectroscopy of three edge-on galaxies in the Fornax cluster.

Findings

No increase in PNe specific abundance from metal-rich to metal-poor regions.

Spatial consistency is crucial to avoid misleading correlations.

Variations in PNe may occur only in extreme metallicity regimes.

Abstract

Context. Extragalactic Planetary Nebulae (PNe) are useful distance indicators and are often used to trace the dark-matter content in external galaxies. At the same time, PNe can also be used as probes of their host galaxy stellar populations and to help understanding the later stages of stellar evolution. Previous works have indicated that specific number of PNe per stellar luminosity can vary across different galaxies and as a function of stellar-population properties, for instance increasing with decreasing stellar metallicity. Aims. In this study we further explore the importance of stellar metallicity in driving the properties of the PNe population in early-type galaxies, using three edge-on galaxies in the Fornax cluster offering a clear view into their predominantly metal-rich and metal-poor regions near the equatorial plane or both below and above it, respectively . Methods. Using VLT-MUSE integral-field observations and dedicated PNe detection procedures, we construct the PNe luminosity function and compute the luminosity-specific number of PNe alpha in both in- and off-plane regions of our edge-on systems. Results. Comparing these alpha values with metallicity measurements also based on the same MUSE data, we find no evidence for an increase in the specific abundance of PNe when transitioning between metal-rich and metal-poor regions. Conclusions. Our analysis highlights the importance of ensuring spatial consistency to avoid misleading results when investigating the link between PNe and their parent stellar populations and suggest that in passively-evolving systems variations in the specific number of PNe may pertain to rather extreme metallicity regimes found either in the innermost or outermost regions of galaxies.