Ultraviolet imaging polarimetry of the Large Magellanic Cloud. II. Models

Motivated by new sounding-rocket wide-field polarimetric images of the Larg e Magellanic Cloud (reported simultaneously by Cole et al.), we have used a three-dimensional Monte Carlo radiation transfer code to investigate the e scape of near-ultraviolet photons from young stellar associations embedded within a disk of dusty material (i.e., a galaxy). As photons propagate thro ugh the disk, they may be scattered or absorbed by dust. Scattered photons are polarized and tracked until they escape the dust layer, allowing them t o be observed; absorbed photons heat the dust, which radiates isotropically in the far-infrared where the galaxy is optically thin. The code produces four output images: near-UV and far-IR flux, and near-UV images in the line ar Stokes parameters Q and U. From these images we construct simulated UV p olarization maps of the LMC. We use these maps to place constraints on the star+dust geometry of the LMC and the optical properties of its dust grains . By tuning the model input parameters to produce maps that match the obser ved polarization maps, we derive information about the inclination of the L MC disk to the plane of the sky and about the scattering phase function g. We compute a grid of models with i = 28 degrees, 36 degrees, and 45 degrees , and g = 0.64, 0.70, 0.77, 0.83, and 0.90. The model that best reproduces the observed polarization maps has i = 36 degrees(-5)(+2) and g approximate to 0.7. Because of the low signal-to-noise in the data, we cannot place fi rm constraints on the value of g. The highly inclined models do not match t he observed centrosymmetric polarization patterns around bright OB associat ions or the distribution of polarization values. Our models approximately r eproduce the observed ultraviolet photopolarimetry of the western side of t he LMC; however, the output images depend on many input parameters and are nonunique. We discuss some of the limitations of the models and outline fut ure steps to be taken; our models make some predictions regarding the polar ization properties of diffuse light across the rest of the LMC.