Top panel: MUSE LSF from Bacon et al. (2017) (thick black line) and in LEWIS data (thick red line, Eq. A.1). The red dashed line represents the MUSE LSF derived restricting the polynomial fit to λ > 5700 Å (Eq. A.2). The thin horizontal black line marks the spectral resolution of the E-MILES stellar library (FWHM = 2.51Å). Bottom panel: comparison of PPXF results for Bacon et al. (2017) LSF (black), LEWIS LSF (red, Eq. A.2) and constant LSF (grey, FWHM[4800-7000] = 2.69Å).