Position-velocity diagram along M 82’s major axis showing the motion of gas and stars; the vertical dashed lines indicate the extent of the bar (x₂ and x₁-orbits). At the top: measurements at near-IR wavelengths, which probe the center region. At the bottom: measurements at blue wavelengths, which probe the more outer regions. a) From McK93. b) Black dots: from GWNP (10′′ bins); open circles: stellar Ca II measurements by Westmoquette et al. (2009). c) Black dots: average (5′′ bins) of [SII], [NII] emission lines from Fig. 3, A–E, simulating a slit of  ~±7′′ width; gray dots: individual measurements. d) Black dots: Na D measurements by Saito et al. (1984); connected gray open circles: Hα absorption line (component C4) measurement by Westmoquette et al. (2009); open squares: absorption line data from Mayall (1960). e), f) From McK93; f) gray dots: individual measurements.