Spectral indices measured in the bulge of NGC 7025. The reference grid has been created using three different metallicities [M/H] = −0.71, 0.00, and 0.22 (solid blue, green, and red lines, respectively). Ages range from 1 to 17 Gyr, and the ages (in Gyr) of some of the models are marked in the plot. Stars, including their uncertainties, represent the indices measured in the spectra of the elliptical rings we extracted from NGC 7025. The rings from the innermost to the outermost radii are colour-coded blue, orange, green, red, purple, and brown.