Transfer of polarized radiation in astronomical masers

Equations are obtained that describe the transfer of the linearly polarized radiation that occurs naturally in two- and three-dimensional astronomical masers. Although restricted, the geometries to which these equations apply do include disks, spheres, and shells, the properties of which will provide a useful indication of what might be expected for less idealized geometries. The equations are derived for circumstances in which magnetic fields can be ignored (Zeeman splitting <..0 transition specifically being considered. The possibility then exists that substantial linear polarization can be produced by natural asymmetries in the geometry without the need for magnetic fields or pumping mechanisms that select magnetic substates. The apparent sizes that result from the numerical integration will not contain the assumption of rapid cross-relaxation among magnetic sublevels on which previous studies have been based, but for which the justification is uncertain.