THE EMBEDDED YOUNG STARS IN THE TAURUS-AURIGA MOLECULAR CLOUD .1. MODELS FOR SPECTRAL ENERGY-DISTRIBUTIONS

We describe radiative transfer calculations of infalling, dusty envelo pes surrounding pre-main-sequence stars and use these models to derive physical properties for a sample of 21 heavily reddened young stars ( ''protostars'') in the Taurus-Auriga molecular cloud. The density dist ributions needed to match the far-infrared peaks in the spectral energ y distributions of these embedded sources suggest mass infall rates si milar to those predicted for simple thermally supported clouds with te mperatures approximately 10 K. Unless the dust opacities are badly in error, our models require substantial departures from spherical symmet ry in the envelopes of all sources, as in Terebey, Shu, & Cassen's rot ating infall solutions. These flattened envelopes may be produced by a combination of rotation and cavities excavated by bipolar flows. Tere bey, Shu, & Cassen's models indicate a centrifugal radius of approxima tely 70 AU for many objects if rotation is the only important physical effect, and this radius is reasonably consistent with typical estimat es for the sizes of circumstellar disks around T Tauri stars.