Notes. Columns (2) and (3) report the source flux density at 1.0 mm and spectral index between 1 and 3 mm, respectively, from the best fit two-layer disk models adopted in Ricci et al. (2010a,b, 2011a,b). The uncertainties of fluxes in the millimeter range are typically dominated by the uncertainty on the absolute flux scale of the observations. Values of these uncertainties depend on the particular instrument and conditions during the observations, but have typical values around 10−20%. Contrary to Figs. 1 and 2, the 1 mm-fluxes reported here do not consider any correction for the different distances of the three regions. Column (4) lists the product between dust mass and dust opacity at 1 mm from the same models. Columns (5) and (6) report the inferred dust mass for values of 2.5 and 3, respectively, for the power-law slope q of the grain size numberdensity (see e.g. Ricci et al. 2010a for more details). Blank fields in Cols. (4)−(6) are for cases in which no good fit could be obtained.