Angular offsets (along the main axis with position angle 225° toward the southwest) of molecular vs. continuum centroid position (obtained from two-dimensional Gaussian fits) as a function of depth of the spectral dip near the systemic velocity in percent of the line peaks at V ≈ 430 km s⁻¹. The percentages given refer to a covered area of 0.25 arcmin² as described in Fig. 4. Molecular species are indicated. For details, also including line assignments, formal uncertainties and rest frequencies, see Sect. 4.1.2 and Table 1.