Our results for M 82. Left: same as in Fig. 8, but applied to the Cα-transitions of M 82. We did not proceed with the stack cross-correlation because no significant outlier was identified in (B). The shaded region in gray shows the redshift range probed by M14. The red data point shows z_M 82 = 0.00070, the redshift corresponding to the peak of the RRL emission, as reported by M14. Right: stacked spectrum of M 82, in velocity units, with respect to z_M 82 = 0.00070. The error bars reflect the standard deviation of a weighted mean (see Sect. 3.1).