Average brightness distributions, in a 3.3 km s⁻¹ wide channel centred on the systemic velocity, of selected molecules towards IRAS 15194–5115 (left panels) and IRAS 15082–4808 (right panels). The names of the species whose emissions are shown in colour and contours are given in the bottom right corner of each panel in green and white, respectively. The synthesised beams of the colour maps and contours are shown as filled and hollow ellipses, respectively, in the bottom left corner of each panel. Contours are from 3σ to 15σ in intervals of 1σ. The σ values of the contour maps are, for IRAS 15194–5115, SiC₂: 0.68 mJy beam⁻¹ and C₂H: 0.50 mJy beam⁻¹, and, for IRAS 15082–4808, SiC₂: 1.1 mJy beam⁻¹ and C₂H: 0.31 mJy beam⁻¹. The red + denotes the stellar position (continuum peak). Red circles of radius 2.″5, 5.″0 and 7.″5 are drawn on each map to facilitate comparisons.