“Hunter-plot” displaying the nitrogen abundance vs. projected rotational speed. Population synthesis from Brott et al. (2011b), for T_eff ≥ 29 kK and a magnitude limit V ≤ 15.29, shown as a density plot in the background. The color coding corresponds to the number of stars per bin, with binsize 5 km   s^-1  ×  0.04 dex. Overplotted are data from this study. Black: N11 stars; blue: field stars. Circles, diamonds and squares correspond to objects with low, intermediate and strong helium enrichment, respectively (see text). Alternative solutions for N11-031 (intermediate He enrichment) as in Fig. 8.