Bipolar reflection nebulae - Monte Carlo simulations

Abstract

A Monte Carlo technique is used to simulate three well-known bipolar reflection nebulae associated with evolved stars, the Red Rectangle (HD 44179), CRL 2688, and Minkovski's Footprint (M1-92). The simulated intensity distributions are found to be in good agreement with the photographs of these nebulae. Although a number of free parameters are present in the models, the basic geometrical configuration - a dust density which decreases monotonically with latitude above an equatorial plane and radially as the reciprocal of r-squared appears to provide a good description of bipolar nebulae in general. In spite of the high degree of linear polarization in the objects studied, multiple scattering is found to be important for reproducing the observed nebular forms. The models can be refined when accurate photometry and photopolarimetry are performed on these objects.