L_bol vs. M_env diagram for the massive YSOs (solid circles with IDs). The dotted blue lines represent the evolutionary tracks from André et al. (2008). Evolution proceeds from the upper left to the lower right (indicated by arrows at the end of each track). The final stellar masses of these tracks in solar units are given above the lower axis. The slanted red line corresponds to the location where 50% of the initial core mass is converted into stellar mass (see Bontemps et al. 1996; André et al. 2000).