The Age of the Galactic Stellar Halo from Gaia White Dwarfs

Mukremin Kilic, P. Bergeron, Kyra Dame, N. C. Hambly, N. Rowell, Courtney L. Crawford

Research output: Contribution to journalArticlepeer-review

Abstract

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. The white dwarf cooling ages of our targets range from 7 Myr for J1657+2056 to 10.3 Gyr for J1049-7400. The latter provides a firm lower limit of 10.3 Gyr for the age of the inner halo based on the well-understood physics of white dwarfs. Including the pre-white dwarf evolutionary lifetimes, and limiting our sample to the recently formed white dwarfs with cooling ages of \$
Original language English Monthly Notices of the Royal Astronomical Society https://doi.org/10.1093/mnras/sty2755 Published - 11 Oct 2018

• astro-ph.SR
• astro-ph.GA

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