Could very low-metallicity stars with rotation-dominated orbits have been shepherded by the bar?

Understand

The most metal-poor stars (e.g.

• [Fe/H] $\leq-2.5$) are the ancient fossils from the early assembly epoch of our Galaxy, very likely before the formation of the thick disc.
• Recent studies have shown that a non-negligible fraction of them have prograde planar orbits, which makes their origin a puzzle.
• It has been suggested that a later-formed rotating bar could have driven these old stars from the inner Galaxy outward, and transformed their orbits to be more rotation-dominated.