The Planetary Nebula Luminosity Function at the Dawn of Gaia

TL;DR

This paper reviews and compares the planetary nebula luminosity function (PNLF) as a distance measurement tool, calibrates it against other methods, and discusses how space missions can enhance understanding of planetary nebulae and improve cosmic distance scales.

Contribution

It provides a comprehensive calibration of the PNLF method, compares it with other distance indicators, and explores how Gaia and Kepler data can refine planetary nebula physics and distance measurements.

Findings

PNLF distances agree with Cepheid and TRGB calibrations within uncertainties.

Surface Brightness Fluctuation method yields ~15% larger distances than PNLF.

Systematic errors from internal reddening likely explain discrepancies between methods.

Abstract

The [O III] 5007 Planetary Nebula Luminosity Function (PNLF) is an excellent extragalactic standard candle. In theory, the PNLF method should not work at all, since the luminosities of the brightest planetary nebulae (PNe) should be highly sensitive to the age of their host stellar population. Yet the method appears robust, as it consistently produces < 10% distances to galaxies of all Hubble types, from the earliest ellipticals to the latest-type spirals and irregulars. It is therefore uniquely suited for cross-checking the results of other techniques and finding small offsets between the Population I and Population II distance ladders. We review the calibration of the method and show that the zero points provided by Cepheids and the Tip of the Red Giant Branch are in excellent agreement. We then compare the results of the PNLF with those from Surface Brightness Fluctuation measurements, and show that, although both techniques agree in a relative sense, the latter method yields distances that are ~15% larger than those from the PNLF. We trace this discrepancy back to the calibration galaxies and argue that, due to a small systematic error associated with internal reddening, the true distance scale likely falls between the extremes of the two methods. We also demonstrate how PNLF measurements in the early-type galaxies that have hosted Type Ia supernovae can help calibrate the SN Ia maximum magnitude-rate of decline relation. Finally, we discuss how the results from space missions such as Kepler and Gaia can help our understanding of the PNLF phenomenon and improve our knowledge of the physics of local planetary nebulae.