Disk Properties and Density Structure of the Star‐forming Dense Core B335

We present subarcsecond resolution dust continuum observations of theprotostellar collapse candidate B335 made with the IRAM Plateau de BureInterferometer at wavelengths of 1.2 and 3.0 mm. These observations probe to <100 AU size scales and reveal a compact source component that we identify witha circumstellar disk. We analyze these data in concert with previous lowerresolution interferometer observations and find a best fit density structurefor B335 that consists of a power law envelope with index p=1.55 +/- 0.04 (r <5000 AU) together with a disk (r < 100 AU) of flux F_{1.2 mm}=21 +/-2 mJy. Weestimate a systematic uncertainty in the power law index delta(p) < 0.15, wherethe largest error comes from the assumed form of the dust temperature falloffwith radius. This determination of the inner density structure of B335 has aprecision unique amongst protostellar cores, and it is consistent with ther^{-1.5} profile of gravitational free-fall, in accord with basic expectationsfor the formation of a star. The flux (and implied mass) of the compactcomponent in B335 is typical of the disks around T Tauri stars.Comment: 16 pages, 2 figures. Accepted to the Astrophysical Journal, sched v596 (2003 Oct 10