LVG calculations. We assumed N(SO) = 2 × 10¹³ cm^-2, N(H₂CO) = 1 × 10¹³ cm^-2, and N(C¹⁸O) = 2 × 10¹⁶ cm^-2. From top to bottom, we plot the I(SO J = 5₆ → 4₅)/I(C¹⁸O J = 2 → 1), I(SO J = 5₆ → 4₅)/I(H₂CO J = 3_0,3 → 2_0,2), and I(H₂CO J = 3₀₃ → 2₀₂)/I(C¹⁸O J = 2 → 1) line intensity ratios. The long-dashed line corresponds to a gas kinetic temperature of T_k = 30 K, which is the midplane temperature derived by Piétu et al. (2005) and Pacheco-Vázquez et al. (2015). Solid lines indicate the values derived from our maps (Fig. 5). The red and blue lines trace the maximum and minimum observed ratios, respectively.