MODEL SCATTERING ENVELOPES OF YOUNG STELLAR OBJECTS .2. INFALLING ENVELOPES

We present scattered light images for models of young stellar objects surrounded by dusty envelopes. The envelopes are assumed to have finite angular momentum and are falling in steady flow onto a disk. The model envelopes include holes, such as might be created by energetic bipolar flows. We calculate images using the Monte Carlo method to follow the light scattered in the dusty envelope and circumstellar disk, assuming that the photons originate from the central source. Adopting typical interstellar medium dust opacities and expected mass infall rates for protostars M approximately 10(-6) M. yr-1. we find that detectable amounts of optical radiation can escape from envelopes falling into a disk as small as approximately 10-100 AU, depending upon the viewing angle and the size of the bipolar flow cavity. The models explain general features of polarization maps of many young stellar objects. In particular, parallel polarization patterns ('' polarization disks '') can be produced by multiple scattering effects very simply in envelopes and do not require large-scale disk structure. We suggest that the extended optical and near-IR light observed around several young stars is scattered by dusty infalling envelopes rather than disks.