Local stellar formation history from the 40 pc white dwarf sample

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 approximate to 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 time-scales. 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.

Automated summary

We use the Gaia-defined 40 pc white dwarf sample to derive the local stellar formation history. This is the largest sample of white dwarfs with available spectroscopy, allowing for classification of chemical abundances and accurate determination of atmospheric parameters. Our population synthesis model shows that a uniform stellar formation history over the past 10.5 billion years fits well with the observed distribution of absolute Gaia G magnitudes. We test the robustness of our model by varying several assumptions, and find that the relative stellar formation rate is not significantly affected, although the onset of stellar formation is sensitive to input parameters like white dwarf cooling models.