Stacked outer disk spectrum: Grey represents the mean co-added spectrum of AGB plus RGB stars with F814W magnitude brighter than 25.72. Red: Co-added spectrum smoothed by a Gaussian kernel of 2 pixels weighted by the inverse variance of the sky spectrum. Blue: Best fit from pPXF. Upper panel: Full spectrum wavelength, 4800–8800 Å, used to measure velocity with pPXF. Bottom panel: Zoom on the CaT region and marked with a black dashed lines the position of these lines: 8498, 8542 and 8662 Å in the restframe. Black solid lines mark the position of the observed CaT lines.