The GALAH survey and Gaia DR2: dissecting the stellar disc's phase space by age, action, chemistry and location

Understand

We use the second data releases of the ESA Gaia astrometric survey and the high-resolution GALAH spectroscopic survey to analyse the structure of our Galaxy's disc components.

• With GALAH, we separate the alpha-rich and alpha-poor discs (with respect to Fe), which are superposed in both position and velocity space, and examine their distributions in action space.
• We study the distribution of stars in the zV_z phase plane, for both V_phi and V_R, and recover the remarkable "phase spiral" discovered by Gaia.
• We identify the anticipated quadrupole signature in zV_z of a tilted velocity ellipsoid for stars above and below the Galactic plane.