Radial profiles of the in-band spectral index, optical depth, and temperature towards SM1. The solid purple line shows the in-band spectral index. The shaded area shows the 1σ uncertainty. The estimated 3 mm optical depth and temperature profiles are shown with dashed purple and dotted black lines, respectively. The temperature profile is extrapolated beyond r ∼ 15 au following a r^−0.5 power law. The observed brightness temperature profile is overlaid in solid gray, similar to Figure 1.