Structure of protostellar collapse candidate B335 derived from near-infrared extinction maps

We present a near-infrared extinction study of the dark globule B335, a protostellar collapse candidate, using data from the Hubble Space Telescope/Near Infrared Camera and Multi-Object Spectrometer and the W. M. Keck Observatory. These data allow a new quantitative test of the inside-out collapse model previously proposed to explain molecular line profiles observed toward this region. We find that the shape of the density profile is well matched by the collapse model but that the amount of extinction corresponds to larger column densities than predicted. An unstable Bonnor-Ebert sphere with dimensionless outer radius xi (max) = 12.5 +/- 2.6 provides an equally good description of the density profile and is indistinguishable from the collapse model over the range in radius sampled by the extinction data. The bipolar outflow driven by the embedded young stellar object has an important effect on the extinction through the core, and modeling the outflow as a hollowed-out bipolar cone of constant opening angle provides a good match to the observations. The complete extinction map is well reproduced by a model that includes both infall and outflow and an additional 20% dispersion that likely results from residual turbulent motions. This fitted model has an infall radius of R(inf) = 26 +/- 3 (0.031 pc for 250 pc distance) and an outflow cone semiopening angle of alpha = 41 degrees +/- 2 degrees. The fitted infall radius is consistent with those derived from molecular line observations and supports the inside-out collapse interpretation of the density structure. The fitted opening angle for the outflow is slightly larger than observed in high-velocity CO emission, perhaps because the full extent of the outflow cone in CO becomes confused with ambient core emission at low velocities.