Dots with 3σ error bars mark the differences between the radial velocities measured with the Effelsberg 100-m telescope in 1977–1981 (Ungerechts & Güsten 1984) and in the present dataset toward the same positions in Do279P12. The red points indicate deviations from zero that are larger than 3σ. At two offsets, (Δα,Δδ) = (80′′,0′′) and (160′′, − 120′′), we detected double NH₃ profiles (see Fig. B.4).