# The effects of $^{22}$Ne sedimentation and metallicity on the local 40 pc white dwarf luminosity function

## TL;DR

This study investigates how $^{22}$Ne sedimentation and metallicity variations influence the local white dwarf luminosity function, using population synthesis models to improve fit with observed data and estimate the Galactic disk age.

## Contribution

It introduces a combined model including $^{22}$Ne sedimentation, metallicity dispersion, and thick disk contribution to accurately reproduce the white dwarf luminosity function.

## Key findings

- Metallicity dispersion improves model fit to observations.
- $^{22}$Ne sedimentation marginally affects the luminosity function.
- Estimated thin disk age is approximately 8.8 Gyr.

## Abstract

We analyze the effect of the sedimentation of $^{22}$Ne on the local white dwarf luminosity function by studying scenarios under different Galactic metallicity models. We make use of an up-to-date population synthesis code based on Monte Carlo techniques to derive the synthetic luminosity function. Constant solar metallicity models are not able to simultaneously reproduce the peak and cut-off of the white dwarf luminosity function. The extra release of energy due to $^{22}$Ne sedimentation piles up more objects in brighter bins of the faint end of the luminosity function. The contribution of a single burst thick disk population increases the number of stars in the magnitude interval centered around $M_{\rm bol}=15.75$. Among the metallicity models studied, the one following a Twarog's profile is disposable. Our best fit model was obtained when a dispersion in metallicities around the solar metallicity value is considered along with a $^{22}$Ne sedimentation model, a thick disk contribution and an age of the thin disk of $8.8\pm0.2$ Gyr. Our population synthesis model is able to reproduce the local white dwarf luminosity function with a high degree of precision when a dispersion in metallicities around the solar value model is adopted. Although the effects of $^{22}$Ne sedimentation are only marginal and the contribution of a thick disk population is minor, both of them help in better fitting the peak and the cut-off regions of the white dwarf luminosity function.