Metallicity derivation. Top: calibration of metallicity based on CO and Na EW. The large symbols represent the 183 used calibration spectra; the symbol shape shows the source of spectra and metallicity (Magrini et al. 2010; Thorsbro et al. 2020; Ahumada et al. 2020; Arentsen et al. 2019). The value is indicated by the color within SINF indicates SINFONI. The background shows the derived relation; the color range saturates below [Fe/H] < −2.5 and above [Fe/H] > 0.6 (the range of the calibrators.), where the derived values are based on more uncertain extrapolation. The two vertical lines separate the application of the high and low CO solutions; in the overlap region in between both high and low CO solutions are used to derive metallicities. The small dots show all our KMOS targets with S/N > 30 and a CO based velocity. The background shows the derived value only for areas where either calibrators or the nuclear stars have coverage. Bottom: comparison between literature (x-axis) and our metallicities (y-axis). The thick black line indicates the identity line; the thin lines bracket the typical uncertainty. Stars are coded by CO depth; the hottest have the smallest depth.