Left: zoom-in of position-velocity diagram shown in Fig. 8. Green box indicates the area in the diagram on the right. Right: N₂H⁺ position-velocity diagram of the northern portion of the ISF. Red line is the ¹³CO gas ridgeline while the green line shows thevelocity centroid of the N₂H⁺ line. The protostars (yellow ×-symbols) have velocities that are slightly displaced from the CO gas but directly associated with N₂H⁺. Ordinate is δ [deg].