We present a near-infrared extinction study of the dark globule B335 , a protostellar collapse candidate , using data from HST/NICMOS 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 _ { \mathrm { max } } = 12.5 \pm 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 exinction 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 _ { \mathrm { inf } } = 26 \pm 3 ^ { \prime \prime } ( 0.031 pc for 250 pc distance ) , and an outflow cone semi-opening angle of \alpha = 41 \pm 2 ^ { \circ } .
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 .