Histogram of radial velocities of sources from Regions 1 and 4. Red bars correspond to GALAXIA predictions for the disk of the Milky Way, while gray bars correspond to predictions for the halo; blue dashed bars correspond to probability densities of Gaia DR2 data (13 sources in Region 1; 51 in Region 4). The probability density is an amount such that the sum of the values times the bin size is equal to 1. Bins were computed according to the Freedman–Diaconis rule.