Series of plots showing the different steps of calculations carried out for each source. The example shows source 29, which is located in the center of the W43 complex at a velocity of 115 km s^-1. From left to right: a) ¹³CO (2–1) in [K km s^-1]; b) C¹⁸O (2–1) in [K km s^-1]; c) optical depth τ of ¹³CO (2–1); d) excitation temperature in [K]; and e) H₂ column density map in [cm^-2] derived from the CO lines as described in Sect. 4.1.3. The column density has been calculated from an assumed constant excitation temperature.