Histograms of the estimated masses of indicated regions observed with Bands 7 and 9, using Equation (3) and the data in Table 2. Uncertainties in mass are calculated using the rms values (ΔM ∝ rms) and uncertainties in β values, and are shown as black error bars. Left: estimated mass adopting κ_λ ∝ κ_λ,0(λ/1 mm)^−β, with κ_λ,0 = 0.078 cm² g⁻¹ (V. Ossenkopf & T. Henning 1994). Right: estimated mass adopting κ_λ,0 = 0.35 cm² g⁻¹ (B. T. Draine 2003a, 2003b). Note the difference in the scaling of the y-axis between panels.