v_mic–T_eff distribution of the sample stars divided into four spectral luminosity subgroups as defined in Sect. 5.2. Symbols and colours as indicated in the legend with LC V/IV and LC III/I targets highlighted by solid and open circles, respectively. In the top left panel the steep drop in v_mic is highlighted by a gray vertical line. For high-mass stars (M_init ≥8 M_⊙, Gr. 1&2) the uncertainty in the determination of v_mic is typically between 1 and 5 km s⁻¹; for low-mass ones (M_init ≤8 M_⊙, Gr. 3 & 4) it is generally below 1 km s⁻¹ (for more details, see the text).