Vertical velocity dispersion (σ_z) of the inner, local, and outer subsamples as a function of stellar ages. In the top panel we display the relation obtained for the main sample; in the bottom panels we show the relation representative of the thick disk selected with [α/Fe] > 0.10 and age older than 8 Gyr (triangles) and the thin disk sample selected with [α/Fe] < 0.10 dex and age younger than 8 Gyr (squares). This selection allows us to avoid the region in which the thin and thick disk populations mix and the possible YAR candidates. σ_z is determined for 1 Gyr age bins and the points are plotted in the middle of each bin. The colorcoding indicates the mean of the individual [α/Fe] (top and middle) and [Fe/H] (bottom) of the stars in each bin. For each population, the bin with the fraction of stars exceeding 1% of the total number of stars is shown. The pink thick line represents the global trend of the main sample. A blue line at σ_z = 30 km/s is also shown for reference.