Metallicity of the NSC as a function of the galaxy stellar mass (figure reconstructed and updated from Fig. 9 in Neumayer et al. 2020). The blue open circle indicates the [Fe/H] metallicity of the decomposed NSC of M 74. For comparison, [Fe/H] of the decomposed host galaxy is indicated with an open square, while a star indicates the [Fe/H] from the original (integrated) data cube of M 74 (see the text for all the details). The ETGs are indicated in red and LTGs in blue. Red circles are points from spectroscopic and photometric data (Koleva et al. 2009; Paudel et al. 2011; Spengler et al. 2017; Kacharov et al. 2018), as from Neumayer et al. (2020). The two solid black lines are the mass-metallicity relations of galaxies, given as reference, at the low-mass end (Kirby et al. 2013) and the high-mass end (Gallazzi et al. 2005). We have added the red triangles, which are NSC total metallicities ([M/H]) from Fahrion et al. (2021) and are therefore considered as upper limits for [Fe/H]. We have also added all the blue points. Blue triangles are for [M/H] and are thus upper limits of the NSCs in dwarf LTGs in Fahrion et al. (2022a). Blue circles are for the NSC [Fe/H] in more massive LTGs in Kacharov et al. (2018).