Example of absorption line spectra (black) after stellar subtraction (Sect. 3.2) and their modelling from the central region of MEGARA data (R = 145, i.e. 160 pc). The grey band indicates the spectral band blocked during the fitting due to residuals from stellar subtraction (see Sect. 3.3.2). The orange vertical lines and the red and green curves, as well as both vertical and horizontal yellow lines, are as in Fig. 4.