Reduced proper motion with Gaia DR3

Using the colour range 0.45<(G-G_RP_)<0.715 where the main sequence is narrower, gives an even better accuracy down to 0.39kpc in distance. The distribution of these sources in the sky, together with their tangential component velocities, are very well-suited to study retrograde substructures. We explore the selection of two complex retrograde streams: GD-1 and Jhelum.

For these streams, we resolve the gaps, wiggles and density breaks reported in the literature more clearly and also derive metallicity dependent distances. We also illustrate the effect of the kinematic selection bias towards high proper motion stars and incompleteness at larger distances due to Gaia's scanning law. These examples showcase how the full RPM catalogue made available here can help us paint a more detailed picture of the build-up of the Milky Way halo.

It is a golden age to do Galactic Archaeology. Such a main sequence stars sample with the largest halo cartograph in the era of Gaia can also be used to provide spectroscopic targets to the next big spectroscopic surveys such as WEAVE, 4MOST, and SDSS-V because this catalogue complements the Gaia DR3 source spectra at the fainter end. Even low-resolution spectroscopic follow-up that can provide us with the missing line-of-sight velocities and/or metallicities can be extremely useful to disentangle the merger history of the inner stellar halo.