Temperature (in Kelvin) as function of the H₂CO (5_1,5−4_1,4)/(4_1,4−3_1,3) line ratio. The black datapoints illustrate the calculated excitation temperatures from the individual pixels of the corresponding line ratio maps. The gray lines indicate RADEX models of the kinetic temperature as function of line ratio for different values of H₂ volume density as indicated in the lower right panel. The models were computed using ortho-H₂CO column densities of (a) 2.9 × 10¹⁴ cm⁻² (b) 3.9 × 10¹³ cm⁻², which correspond to the values at A/B and the average on the other positions, respectively. Color markers indicate the line ratios and temperatures observed at the positions stated in the upper left corners.