Distance of stars in the line of sight towards three Vela C fields and three control fields (see text) from Gaia DR2. The number of stars is displayed in bins of 50 pc in width, error bars are computed according to Poissonian statistics. a: farther control field outside the Galactic Plane, b: nearer control field outside the Galactic Plane (red) and control field located at l = 240°, b = 0° (blue), c: field centred on sub-field North, d: field centred on RCW36, and e: field centred on the South-Nest. The full line is a N ~ d^0.7 fit to the data in a, multiplied by two in b to e. The vertical dotted lines mark the sudden decrease in the number of stars, which is likely to coincide with the location of the molecular gas.