Envelope Emission in Young Stellar Systems: A Subarcsecond Survey of Circumstellar Structure

We present modeling results for six of the eleven deeply embedded systemsfrom our sub-arcsecond 2.7 mm wavelength continuum interferometric survey. Themodeling, performed in the uv plane, assumes dust properties, allows for apower-law density profile, uses a self-consistent, luminosity conservingtemperature profile, and has an embedded point source to represent acircumstellar disk. Even though we have the highest spatial resolution to dateat these wavelengths, only the highest signal-to-noise systems can adequatelyconstrain the simple self-similar collapse models. Of the six sources modeled,all six were fit with a density power-law index of 2.0; however, in half of thesystems, those with the highest signal-to-noise, a density power-law index of1.5 can be rejected at the 95% confidence level. Further, we modeled thesystems using the pure Larson-Penston (LP) and Shu solutions with only age andsound speed as parameters. Overall, the LP solution provides a better fit tothe data, both in likelihood and providing the observed luminosity, but the ageof the systems required by the fits are surprising low (1000-2000 yrs). Wesuggest that either there is some overall time scaling of the self-similarsolutions that invalidate the age estimates, or more likely we are at the limitof the usefulness of these models. With our observations we have begun to reachthe stage where models need to incorporate more of the fundamental physics ofthe collapse process, probably including magnetic fields and/or turbulence. Inaddition to constraining collapse solutions, our modeling allows the separationof large-scale emission from compact emission, enabling the probing of thecircumstellar disk component embedded within the protostellar envelope.Comment: 28 pages, 8 figures. Accepted for publication in Ap