Mass–metallicity plane. Both panels show mass and metallicity for the host galaxies of our sample at 1.0 R_eff where available (rightward triangles, otherwise leftward triangles), NSCs (plus symbols) and GCs (coloured circles, from Fahrion et al. 2020b). Left: components are colour-coded by mean age, inferred from full spectrum fitting. Right: shown for comparison are the literature NSCs (orange and brown crosses) and their hosts galaxies (light blue and purple stars) from Paudel et al. (2011) and Spengler et al. (2017), and MW GCs (small grey dots) from Harris (1996).