The growth of proto-stellar discs

We compare interferometry observations with single-dish data at sub-millimetre wavelengths. The interferometer data trace circum-stellar discs around young stellar objects. As an example we show data for the Class I proto-star LI709B and show that it has a disc that can be modelled with a Gaussian of roughly 60 astronomical units full width at half maximum. We also review data of the Class II young stellar object TW Hydra compared to a Keplerian disc model. Using other data from the literature, we make the comparison between the flux seen by single-dish observations, which trace the envelope mass, and the flux recovered by interferometer observations, which trace the disc mass. We compare this ratio with the evolutionary status of proto-stars, as measured by their bolometric temperatures. We find that the ratio of the disc to envelope mass increases with evolutionary stage. Hence we purport that this ratio is an important diagnostic in the study of the evolution of young stellar objects, as their envelopes undergo dissipation and collapse onto their circumstellar discs.