The galactic population of white dwarfs

TL;DR

This paper models the white dwarf populations in the Milky Way, revealing that halo white dwarfs are numerous but not dominant in mass, and highlighting the significant role of thick disc white dwarfs.

Contribution

It provides a new population model based on local observations and Galactic structure, clarifying the contributions of different populations to the Galaxy's stellar mass.

Findings

Halo white dwarfs are numerous but contribute less to stellar mass.

Thick disc white dwarfs are more significant than previously thought.

Misclassification affects estimates of halo white dwarf populations.

Abstract

The contribution of white dwarfs of the different Galactic populations to the stellar content of our Galaxy is only poorly known. Some authors claim a vast population of halo white dwarfs, which would be in accordance with some investigations of the early phases of Galaxy formation claiming a top-heavy initial-mass-function. Here, I present a model of the population of white dwarfs in the Milky Way based on observations of the local white dwarf sample and a standard model of Galactic structure. This model will be used to estimate the space densities of thin disc, thick disc and halo white dwarfs and their contribution to the baryonic mass budget of the Milky Way. One result of this investigation is that white dwarfs of the halo population contribute a large fraction of the Galactic white dwarf number count, but they are not responsible for the lion's share of stellar mass in the Milky Way. Another important result is the substantial contribution of the - often neglected - population of thick disc white dwarfs. Misclassification of thick disc white dwarfs is responsible for overestimates of the halo population in previous investigations.