Panel a: difference between spatial distributions of Gaia members (according to both proper motion and parallax) with μ_α less and above 1.33 mas yr⁻¹, respectively. Only Gaia sources with μ_α errors less than 0.5 mas yr⁻¹ are considered. In blue (yellow) are negative (positive) values, with green indicating zero difference. Dashed squares are the Chandra FOVs. The red and black dotted contours describe the original distributions in the two μ_α ranges, whose difference is shown by the map. Panel b: same as panel a, but showing the difference between distributions of stars with μ_δ less and above −2.0 mas yr⁻¹.