Integrated-intensity maps towards IRAS 4B1 and 4B2 (green stars) for various molecules. The transitions we used and their upper-level energies are given above the respective panel. Contours are at −5σ, 5σ, and 10σ, and then increase by a factor of 3 for all but SiO, CO, H₂CO, and CH₃OH, for which contours start at −10σ and 10σ. The noise level, σ, is measured in the respective map and is written in the bottom right corner. The velocity range (in kms⁻¹) used for the integration is indicated in the top left corner. The grey scale shows the sum of the red- and blueshifted maps. The HPBW is shown in the bottom left corner. The dashed grey circle indicates the primary beam (~23″). The positions R1 and B1 (green circles) are selected for further spectral line analysis.