Centroid map of the isolated hyperfine component of N₂H⁺ in the junction region. The light blue and dark red lines show the contours of the ¹³CO emission from the IRAM data integrated between 3.6 and 6.0 km s⁻¹, and between 6.3 and 9.3 km s⁻¹, corresponding to the north-eastern filament and the main filament, respectively. The levels are between 3 and 18 K km s⁻¹ by steps of 1.8 K km s⁻¹, and between 12 and 18 K km s⁻¹ by steps of 1.8 K km s⁻¹ for the blue and red contours, respectively. In the white area, no line fitting was attempted because the N₂ H ⁺ has a S/N <3.