THE EMBEDDED YOUNG STARS IN THE TAURUS-AURIGA MOLECULAR CLOUD .2. MODELS FOR SCATTERED-LIGHT IMAGES

We describe near-infrared imaging observations of embedded young stars in the Taurus-Auriga molecular cloud. We find a large range in J-K and H-K colors for these class I sources. The bluest objects have colors similar to the reddest T Tauri stars in the cloud; redder objects lie slightly above the reddening line for standard ISM dust and have apparent K extinctions of up to 5 mag. Most of these sources also show extended near-IR emission on scales of 10''-20'', which corresponds to linear sizes of 1500-3000 AU. The near-IR colors and nebular morphologies for this sample and the magnitude of linear polarization in several sources suggest scattered light produces most of the near-IR emission in these objects. We adopt the Terebey, Shu, and Cassen solution for an infalling, rotating protostellar cloud and use a two-dimensional Monte Carlo radiative transfer code to model the near-IR colors and images for the embedded sample. Our results suggest mass infall rates that agree with predictions for cold clouds (T approximately 10-20 K) and are generally consistent with rates estimated from radiative equilibrium models in a previous paper (e.g., M approximately 2-10 x 10(-6) M. yr-1). For reasonable dust grain parameters, the range of colors and extinctions require flattened density distributions with polar cavities evacuated by bipolar outflows. These results support the idea that infall and outflow occur simultaneously in deeply embedded, bipolar outflow sources. The data also indicate fairly large centrifugal radii, R(c) approximately 100 AU, and large inclinations to the rotational axis, i approximately 60-degrees - 90-degrees, for a typical source. Our centrifugal radius estimates agree with the disk radii inferred for many T Tauri stars in the Taurus-Auriga cloud. Better maps of polarization and molecular outflows in these objects can test our inclination estimates.