The Age of the Galactic Stellar Halo from Gaia White Dwarfs

Understand

We use 156 044 white dwarf candidates with $\geq5\sigma$ significant parallax measurements from the Gaia mission to measure the velocity dispersion of the Galactic disc; $(\sigma_U,\sigma_V,\sigma_W) = (30.8, 23.9, 20.0)$ km s$^{-1}$.

• We identify 142 objects that are inconsistent with disc membership at the $>5\sigma$ level.
• This is the largest sample of field halo white dwarfs identified to date.
• We perform a detailed model atmosphere analysis using optical and near-infrared photometry and parallaxes to constrain the mass and cooling age of each white dwarf.