The mysterious cut-off of the Planetary Nebula Luminosity Function

TL;DR

This paper explains the consistent bright-end cutoff of the Planetary Nebula Luminosity Function across different galaxies using new post-AGB evolutionary models, resolving a long-standing mystery and confirming its use as a distance indicator.

Contribution

The study demonstrates that recent post-AGB evolutionary tracks can explain the universal bright-end cutoff of the PNLF, linking stellar evolution to this extragalactic distance measure.

Findings

Post-AGB models reproduce the PNLF cutoff across galaxy types.

Models show progenitors between 1.1 and 2.0 solar masses evolve quickly enough.

The Sun will form a faint planetary nebula at the end of its life.

Abstract

Planetary Nebulae (PN) emit enormous amount of energy in several emission lines. Measuring the line-flux for PNe in a given stellar population, the Planetary Nebula Luminosity Function (PNLF) can be compiled. Surveys of PNe revealed that the faint-end of the PNLF can be approximated by a simple exponential dependency expected for an expanding spherical shell. However at the bright-end there exists a steep cut-off which was unexpected and remains unexplained. Interestingly, the cut-off value appears to be nearly the same for different stellar populations as young spiral galaxies and old elliptical galaxies and, despite the lack of understanding, became an extragalactic distance estimator. Here we show that the recently computed post-AGB evolutionary tracks are capable to explain the decades old mystery. All new models with ages between 1 and 7 Gyr (progenitor masses between 2.0 and 1.1 of solar mass) evolve fast enough to ionize the PN, and at similar post-AGB luminosity which allows the [O III] 500.7nm line to reach nearly the same magnitude. The new models predict that the Sun at the end of its life will form a rather faint PN.