Data histograms and LTE models of the emission of the rotational transitions of ¹²CO and its isotopologs mapped in the extended G field with the IRAM 30 m and APEX: 1. ¹³CO (1–0) vs. ¹²CO(1–0); 2. ¹³CO (1–0) vs. C¹⁸O(1–0); 3. [¹³CO(1–0)] / [C¹⁸O (1–0)] vs. [¹²CO(1–0)] / [¹³CO (1–0)]; and 4. ¹²CO(3–2) / ¹²CO (2–1) vs. ¹²CO(2–1) / ¹²CO (1–0). The color map corresponds to the amount of data points (line of sight and velocity channels) that fall into a given bin of the histogram. The curves represent families of models of the LTE intensity as a function of the kinetic temperature of ¹³CO. The arrows indicate the direction in which the kinetic temperature grows along a given curve. Control parameters of the LTEmodels are given in Table 4 for each histogram. The dashed black lines represent the 3σ detection level for each axis (histograms 1 and 2).