Same as Fig. 1, but for IRAS4A. The white cross represents the position of secondary protostar IRAS4A2 determined from the 1.3 mm dust continuum emission (see Table 1). The black cross represents the position of the main protostar IRAS4A1 of the multiple system. The black lines represent the integrated intensity contours of each tracer starting at 5σ and increasing in steps of 30σ for N₂H⁺ and 10σ for C¹⁸O (see Tables B.3 and B.4.