Local stellar formation history from the 40 pc white dwarf sample

TL;DR

This study uses the largest volume-complete sample of white dwarfs within 40 parsecs, derived from Gaia data, to reconstruct the local stellar formation history over the past 10.5 billion years, confirming a uniform formation rate.

Contribution

It provides the first detailed local stellar formation history derived from a large, spectroscopically classified white dwarf sample, with robustness tests on model assumptions.

Findings

A uniform star formation history fits the data well.

Assumptions in the model minimally affect the relative formation rate.

The onset of star formation is sensitive to white dwarf cooling models.

Abstract

We derive the local stellar formation history from the Gaia-defined 40 pc white dwarf sample. This is currently the largest volume-complete sample of white dwarfs for which spectroscopy is available, allowing for classification of the chemical abundances at the photosphere, and subsequently accurate determination of the atmospheric parameters. We create a population synthesis model and show that a uniform stellar formation history for the last ~10.5 Gyr provides a satisfactory fit to the observed distribution of absolute Gaia G magnitudes. To test the robustness of our derivation, we vary various assumptions in the population synthesis model, including the initial mass function, initial-to-final mass relation, kinematic evolution, binary fraction and white dwarf cooling timescales. From these tests, we conclude that the assumptions in our model have an insignificant effect on the derived relative stellar formation rate as a function of look-back time. However, the onset of stellar formation (age of Galactic disc) is sensitive to a variety of input parameters including the white dwarf cooling models. Our derived stellar formation history gives a much better fit to the absolute Gaia G magnitudes than most previous studies.