CO SLED of 4C12.50 shown for transitions up to J = 22–21. The CO(22–21) line is seen at 3.5σ levels. Based on our RADEX modeling, the SLED of the three lowest transitions is best fit by gas with a kinetic temperature of 25 K (dashed line). Examples of RADEX models that are consistent with the Herschel data are also shown for gas with a kinetic temperature of 400 K, for a couple of column and volume density combinations (dashed-dotted and dotted lines). The SLEDs of other prototype sources are overplotted for comparison, normalized to L_{CO(1 − 0)}(4C12.50)/L_CO(1−0).