The total stellar halo mass of the Milky Way

Understand

We measure the total stellar halo luminosity using red giant branch (RGB) stars selected from Gaia data release 2.

• Using slices in magnitude, colour and location on the sky, we decompose RGB stars belonging to the disc and halo by fitting 2-dimensional Gaussians to the Galactic proper motion distributions.
• The number counts of RGB stars are converted to total stellar halo luminosity using a suite of isochrones weighted by age and metallicity, and by applying a volume correction based on the stellar halo density profile.
• Our method is tested and calibrated using Galaxia and N-body models.