Gaia Early Data Release 3: The Galactic anticentre
  We aim to demonstrate the scientific potential of the Gaia Early Data Release
3 (EDR3) for the study of the Milky Way structure and evolution. We used
astrometric positions, proper motions, parallaxes, and photometry from EDR3 to
select different populations and components and to calculate the distances and
velocities in the direction of the anticentre. We explore the disturbances of
the current disc, the spatial and kinematical distributions of early accreted
versus in-situ stars, the structures in the outer parts of the disc, and the
orbits of open clusters Berkeley 29 and Saurer 1. We find that: i) the dynamics
of the Galactic disc are very complex with vertical asymmetries, and new
correlations, including a bimodality with disc stars with large angular
momentum moving vertically upwards from below the plane, and disc stars with
slightly lower angular momentum moving preferentially downwards; ii) we resolve
the kinematic substructure (diagonal ridges) in the outer parts of the disc for
the first time; iii) the red sequence that has been associated with the
proto-Galactic disc that was present at the time of the merger with
Gaia-Enceladus-Sausage is currently radially concentrated up to around 14 kpc,
while the blue sequence that has been associated with debris of the satellite
extends beyond that; iv) there are density structures in the outer disc, both
above and below the plane, most probably related to Monoceros, the Anticentre
Stream, and TriAnd, for which the Gaia data allow an exhaustive selection of
candidate member stars and dynamical study; and v) the open clusters
Berkeley~29 and Saurer~1, despite being located at large distances from the
Galactic centre, are on nearly circular disc-like orbits. We demonstrate how,
once again, the Gaia are crucial for our understanding of the different pieces
of our Galaxy and their connection to its global structure and history.
