W49N line of sight kinematics in a nutshell. The mottled blue line shows the galactocentric radius R at each velocity assuming a flat rotation curve with Θ(R) = Θ(R₀) = 220 km s^-1, R₀ = 8.5 kpc. The solid green curve shows the line of sight distance or distances ρ at each velocity and the distance to W49, ρ = 11.1 ± 0.8 kpc (Zhang et al. 2013) is illustrated by an an asterisk. The dotted red curve shows the line of sight velocity gradient dV/dρ due to Galactic rotation. Shown superposed to illustrate the observed range of spectral features are the CO profile in units of Kelvins, offset but not scaled, and the CF⁺ absorption spectrum scaled upward a factor of 100 and offset, both from Fig. 1.