Keck Spectropolarimetry of BALQSO

Abstract

Spectropolarimetry of broad absorption line quasi-stellar objects with the W. M. Keck Telescope is used to put constraints on their nuclear structure. If the continuum polarization is due to electron (or dust) scattering, then the scattered and direct rays probe the nucleus along multiple lines of sight, which suffer differing amounts of absorption. Multiple sources of polarized light contribute to the quasar emission, and the relative sizes and symmetries of these sources can be ascertained. The size of the electron scattering region relative to continuum source, broad emission line region, and broad absorption line region is determined using spectropolarimetry. The geometries of the scattering and broad absorption line regions are discussed in an attempt to discriminate between polar and equatorial outflows. The variation of polarization with velocity in the broad absorption troughs may also be used to study the dynamics of the absorbing gas.