From top to bottom: TRD of ¹²CO 2-1, ¹²CO 3-2, ¹³CO 2-1, C¹⁸O 2-1 and HCO⁺ 3-2: (a) TRD of the observations. (b) TRD of the final result of the models. (c) Difference between the observations and model TRD. For ¹²CO (2-1), the residuals range from −2 to 2 K, while for the ¹²CO (3-2) transition, they extend from −3 to 2 K. In the case of ¹³CO (2-1), the differences are between 0 and 2 K. For C¹⁸O (2-1), the deviations range from −1 to 2 K, and for HCO⁺ (3-2), they span from −1 to 3 K. The vertical black line represents the effective resolution, and the two error bars show the widening of the beam as a function of radius caused by the TRD method. The contours are defined from 4 K to 20 K in steps of 2 K for the observational and model maps, and from −3 K to 3 K in steps of 1 K for the residual maps.