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Session 31 - Quasars.
Oral session, Wednesday, January 07
International Ballroom East,
This thesis is a polarimetric survey of broad absorption line quasi- stellar objects. The continuum, absorption trough, and emission line polarization are studied in detail, yielding clues about the geometrical structure of gas in the inner regions of quasars. The continuum polarization rises to the blue, possibly ruling out optically thin electron scattering. The polarization rises in the troughs, due mainly to partial coverage of the scattering region by the broad absorption line region. Radiation from the broad emission line region is polarized at a lower level, perpendicular to the continuum. Resonantly scattered line photons from the C III] emission region are polarized parallel to the continuum. Resonantly scattered continuum photons from the broad absorption line region are detected for the first time. The combination of the various sources of polarized light and partial coverage of these sources by the broad absorption line region leads to position angle rotations in the broad absorption lines and in the broad emission lines. The variation of polarization with velocity in the trough is consistent with an expanding, accelerating outflow of ionized gas. It also suggests that the flow is non-radial, crossing the line of sight at an angle to the symmetry axis of the quasar. Broad absorption line quasars generally have higher polarization than other quasars, reinforcing the view that they are normal quasars viewed from a more equatorial aspect. However, there is a wide distribution of polarization values that may be due to intrinsic differences in the geometry or optical depth to scattering.
