Lick index-index diagrams for NGC 4513. Left plot: magnesium vs. iron index diagram which allows us to estimate a magnesium-to-iron ratio through the comparison of our measurements with the models by Thomas et al. (2003) for the different Mg/Fe ratios. By comparing the Hβ Lick index with a combined metallicity Lick index involving magnesium and iron lines (right plot), we solve the metallicity–age degeneracy and determine these stellar population parameters with the SSP evolutionary synthesis models by Thomas et al. (2003). Five different age sequences (red lines) are plotted as a reference frame; the blue lines crossing the model age sequences mark the metallicities of +0.67, +0.35, 0.00, and −0.33 from right to left. A large black star corresponds to the central core, R < 4″, and then we go along the radius through the galaxy structure components: R = 4″ − 8″ (bar), R = 8″ − 14″ (pseudobulge), and R = 14″ − 40″ (disc). The point corresponding to the outer stellar disc is outlined by a large square.
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