The Gaia DR2 halo white dwarf population: the luminosity function, mass distribution and its star formation history

Understand

We analyze the volume-limited nearly complete 100 pc sample of 95 halo white dwarf candidates identified by the second data release of Gaia.

• Based on a detailed population synthesis model, we apply a method that relies on Gaia astrometry and photometry to accurately derive the individual white dwarf parameters (mass, radius, effective temperature, bolometric luminosity and age).
• This method is tested with 25 white dwarfs of our sample for which we took optical spectra and performed spectroscopic analysis.
• We build and analyse the halo white dwarf luminosity function, for which we find for the first time possible evidences of the cut-off at its faintest end, leading to an age estimate of $\simeq12\pm0.5 $Gyr.