Origin of the Excess of High-energy Retrograde Stars in the Galactic Halo

Abstract

We report on the very low α -element abundances of a group of metal-poor stars with high orbital energy and with large retrograde motion in the Milky Way halo, whose excess has been reported recently from metallicity and kinematics. We constructed a sample of halo stars with measured abundances and precise kinematics, including ∼880 stars with [Fe/H]