Representative fits of Eq. (3) with significant γ values to illustrate the importance of two temperatures in the fitting function. The long-dashed red curves show the MBB with T_cool, the dot-dashed blue curves T_warm, and the gray (solid) ones the overall best fit. The (heavy) purple long-dashed curve corresponds to a single-temperature MBB with T_dust, normalized to the 160 μm data point. For γ > 0, the simple MBB is clearly missing the contribution toward higher frequencies caused by warm dust at T_warm.