Morphological overview of the sample. Continuum and molecular emission from ¹² CO, CS, H₂ CO, CN, and H₂CS is shown for the whole sample. Images of spectral lines are the flux-integrated map (moment 0) obtained by clipping fluxes below 3σ (the CO, CS, and H₂CO), 2σ (the CN and detected H₂CS), or without any clip (the undetected H₂CS). Continuum fluxes are expressed in mJy beam⁻¹ while line fluxes in mJy beam⁻¹ km s⁻¹. The symbols in the center of the images indicate the geometrical center of the continuum emission. The beam size is indicated tothe bottom-left corner of each panel. All images have the same angular scale, as indicated in the leftmost column. North is up, east is left.