Chemo-kinematics of the $Gaia$ RR Lyrae: the halo and the disc

Understand

We present the results of a multi-component kinematic model of a large sample of RR Lyrae detected by $Gaia$.

• By imposing a four-fold symmetry and employing $Gaia$ proper motions, we are able to infer the behaviour of the velocity ellipsoid between $\approx3$ and $\approx30$ kpc from the centre of the Galaxy.
• We detect the presence of two distinct components: a dominant non-rotating halo-like population and a much smaller rotating disc-like population.
• We demonstrate that the halo RR Lyrae can be described as a superposition of an isotropic and radially-biased parts.