Spatial distribution in the Galactic plane in heliocentric coordinates of the selected OB stars (left panel) and RGB stars with line-of-sight velocities (right panel). For the OB stars, we perform a bivariate kernel density estimation using an Epanechnikov kernel with a smoothing length of 200 pc. For the RGB stars, we construct a 2D histogram using cells of 100 × 100 pc. The Galactic centre is towards the right and is shown with a cross in the right-hand plot. Galactic rotation is clockwise. The position of the Sun is shown with a black dot. A logarithmic stretch is used for the map of the RGB stars to enhance lower-density regions.