Inner Structure of Protostellar Collapse Candidate B335 Derived from Millimeter‐Wave Interferometry

We present a study of the density structure of the protostellar collapsecandidate B335 using continuum observations from the IRAM Plateau de BureInterferometer made at wavelengths of 1.2mm and 3.0mm. We analyze these data,which probe spatial scales from 5000 AU to 500 AU, directly in the visibilitydomain by comparison to synthetic observations constructed from models thatassume different physical conditions. This approach allows for much morestringent constraints to be derived from the data than from analysis of images.A single radial power law in density provides a good description of the data,with best fit power law index p=1.65+/-0.05. Through simulations, we quantifythe sensitivity of this result to various model uncertainties, includingassumptions of temperature distribution, outer boundary, dust opacity spectralindex, and an unresolved central component. The largest uncertainty comes fromthe unknown presence of a centralized point source. A point source with 1.2mmflux of F=12+/-7 mJy reduces the density index to p=1.47+/-0.07. The remainingsources of systematic uncertainty, the most important of which is thetemperature distribution, likely contribute a total uncertainty of < 0.2. Wetherefore find strong evidence that the power law index of the densitydistribution within 5000 AU is significantly less than the value at largerradii, close to 2.0 from previous studies of dust emission and extinction.These results conform well to the generic paradigm of isolated, low-mass starformation which predicts a power law density index close to p=1.5 for an innerregion of gravitational free fall onto the protostar.Comment: Accepted to the Astrophysical Journal; 27 pages, 3 figure