Distribution of the HDO(3_3,1–4_2,2) (upper panel), and CH₃CHO(18_0,18–17_0,17) E&A (middle and lower panels) centroid positions (from fits in the uv domain with1σ error bars) in the velocity channels (sampled at the original spectral resolution of 0.42 km s⁻¹). Magenta points show the emission in the channel sampling the systemic velocity, and red and blue datapoints denote the channels that are red- and blue-shifted in the velocity range (with respect to v_sys), as identified by the labels. The points are overlaid on the disc traced by Lee et al. (2017a) using ALMA Band 7 continuum observations (colour scale and contours).