Longitude-velocity diagram of the 511 keV positron annihilation line in the central radian of the Milky Way. In black, independent data points and one-sigma measurement uncertainties are shown. In addition, the Doppler-velocity measurements of decaying ²⁶Al at 1808.63 keV from Kretschmer et al. (2013) (orange), and line of sight velocity from CO measurements (Dame et al. 2001)(blue-shaded areas) are shown for comparison.