Observed σ_los and estimated masses of UFDs. Upper panel: observed σ_los for the UFDs analyzed in this work sorted by σ_los,f=0. Lower panel: mass estimated with Eq. (3) versus the luminosity, both in log scale. The diagonal dashed gray lines indicate regions of constant M/L (= M_dyn(< r_1/2)/(L/2)) in solar units indicated by the numbers. The horizontal black lines show the 1σ ranges for L. The red, blue, and green vertical lines indicate the median and 1σ ranges for the values uncorrected by binaries, corrected assuming a uniform prior on f and corrected assuming f = 0.7, respectively. The shaded lines in the upper panel indicate the 3σ range.