340GHz SMA obs. of 50 nearby protoplanetary disks

The observed visibility data were modeled with a simple prescription for the radial surface brightness profile. The results were used to extract intuitive, empirical estimates of the emission "size" for each disk, R_eff_, defined as the radius that encircles a fixed fraction of the total continuum luminosity, L_mm_.

We find a significant correlation between the sizes and luminosities, such that R_eff_{propto}L_mm_^0.5^, providing a confirmation and quantitative characterization of a putative trend that was noted previously. This correlation suggests that these disks have roughly the same average surface brightness interior to their given effective radius, ~0.2Jy/arcsec^2^ (or 8K in brightness temperature). The same trend remains, but the 0.2dex of dispersion perpendicular to this relation essentially disappears, when we account for the irradiation environment of each disk with a crude approximation of the dust temperatures based on the stellar host luminosities.