ζ₂ variation as a function of D_GC for the high-mass cores shown in Fig. 5. Circles refer to our estimates of ζ₂ in high-mass star-forming regions in different evolutionary stages (see legend). The same colour-coding as in Fig. 5 is assumed for diamonds. The galactocentric radii are taken from Table 1 (circles), van der Tak & van Dishoeck (2000) (red), Morales Ortiz et al. 2014 (magenta), Winkel et al. 2017 (blue), Spina et al. 2017, and Yan et al. 2019 (cyan). D_CG are scaled assuming a distance to the Galactic Center of 8.35 kpc.