Position-velocity plots along the direction with PA = +45° for H¹³CO⁺ and C³⁴S. The offsets are measured from the phase center, positive to the northeast. The vertical dashed lines indicate the position of cores A, B, C, D, E, and F. The horizontal solid line indicates the V_LSR. The dotted ellipses outline two possibilities for explaining the morphology of the emission: a cavity centered on core A (red ellipse) or alternatively, a cavity centered close to the IR peak (green ellipse; see Sect. 4.4).