Gas cooling (left) and heating (right) rates determined in the best-fit CO model. The cooling includes contributions from CO, H₂O and H₂ line cooling, adiabatic cooling, and cooling due to non-collisional interactions of gas and dust (Hdt). The heating includes some CO line heating (when the cooling is negative), heating from dust-gas collisions, and photoelectric heating from the interstellar radiation field. There is a slight “wiggle” in the CO cooling function due to unavoidable Monte-Carlo noise. This does not have an impact on our results.