This section is under construction...

Modelling the Disc of the Milky Way
...and the features seen in phase-space of the disc in Gaia DR2 see:

This N-body simulation shows the spontaneous formation of a galactic bar and a boxy/peanut bulge in a self-gravitating stellar disc (where the disc is made up of a thin, kinematically cold, a thick kinematically hot and an intermediate disc). In the video on the right the galaxy is rotated so that the bar is always aligned along the x-axis. In the top panel the face-on xy projection is shown and in the bottom panel the edge-on xz projection can be seen. The simulation has 20 million particles distributed in the disc and the dark matter halo. The time at the top is in Gyrs.