The polarization of thermal radiation from supermassive accretion disks

Thermal radiation from an accretion disk is a promising explanation for the optical-ultraviolet "bump" noted in the spectra of active galactic nuclei (AGN). However, the expected polarization of radiation from a standard thin disk conflicts with observation. We have computed the polarization of light emitted by a thin disk with a rough surface and by a thick disk (radiation torus). We find improved agreement with observations, particularly in the case of a thick disk.