Top panel: K-band radially binned spectra obtained with LUCI at LBT for M87. Each spectrum has S/N ratio larger than 90 (per Å; see the text). An arbitrary vertical shift has been applied among different spectra. The main absorption features (see Sect. 4) are marked with gray shaded regions. Different colors correspond to different galactocentric distances, with red marking the center and blue the outermost radial bins (see the inset colored bar). All the spectra in the plot are shown at their nominal velocity dispersion, σ. Bottom panel: Examples of telluric absorption (black) and sky emission (gray) spectra in the restframe of M87 (assuming an heliocentric velocity of 1284 km s⁻¹ as in Cappellari et al. 2011). The sky emission spectrum is normalized to a maximum value of one for displaying purposes.