Distribution of OCs in heliocentric X–Y in different age bins. The Galactic centre is towards positive X values, and the direction of the Galactic rotation is towards positive Y values. Blue crosses are OC with age estimations; regardless of whether they have available radial velocity measurements or not, from left to right and from top to bottom they correspond to: ages below 30 Myr, from 10 to 50 Myr, from 20 to 60 Myr, and from 40 to 80 Myr. The spiral arms defined by Reid et al. (2014) are overplotted.