V_LSR along the filament direction (from core 19 in the south-east to core 8 in the north-west). The transitions are shown with colours: N₂D⁺(2–1) – red circles; N₂H⁺(1–0) – blue squares; DCO⁺(2–1) – orange flipped triangles; H¹³CO⁺(1–0) – green triangles; and C¹⁸O(1–0) – black circles. The vertical bars show the N₂H⁺(1–0) emission peaks. Stars show the positions of YSOs from Rebull et al. (2010): black stars indicate flat and Class I objects, white stars indicate Class II and III objects.