On the existence of a very metal-poor disc in the Milky Way

Abstract

The question of whether the Milky Way's disc extends to low metallicity has been the subject of debate for many years. We aim to address the question by employing a large sample of giant stars with radial velocities and homogeneous metallicities based on the Gaia Data Release 3 BP/RP(XP) spectra. We study the 3D velocity distribution of stars in various metallicity ranges, including the very metal-poor (VMP) regime ([M/H] 1, starts to emerge only around [M/H] ∼-1.3, and is not visible for [M/H]