Contour maps for H¹³CO⁺, C³⁴S, both C₂H doublets andboth c−C₃H₂ transitions, starting at 5σ and following a step of 4σ ( and are 6 mJy beam⁻¹ km s⁻¹, while and are 9 mJy beam⁻¹ km s⁻¹). Green contours represent low-velocity emission, from −1 to 1 km s⁻¹. Blue and redcontours indicate intermediate velocities, from −1 to −5 km s⁻¹ and from 1 to 5 km s⁻¹, respectively. The black contours represent the continuum emission of Fig. 1 for a value of 4 and 15σ (σ = 0.4 mJy beam⁻¹). The yellow and white stars indicate the position of Oph-IRS67A and B, respectively. The black diamond denotes the location of the high-density region. The synthesised beam for each species is represented by a black filled ellipse.