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D.C. Hines, G.D. Schmidt, K.D. Gordon (Steward Observatory), B.J. Wills (U. Texas), P.S. Smith, R.G. Allen (Steward Observatory), M.L. Sitko (U. Cincinnati)
We present UV & optical spectropolarimetry of two highly polarized IRAS-selected QSOs, IRAS 13349+2438 and the BALQSO IRAS 14026+4341. The polarization in both objects rises rapidly towards the blue, peaks near 3000Åin the rest frame and remains nearly constant for shorter wavelengths. The (rest frame) optical polarized flux density spectra rise rapidly towards shorter wavelengths, but decrease dramatically below 3000Å. This distinctive wavelength dependence of polarized flux density shows that the polarization is produced by dust scattering. As for many Seyfert, radio and Hyperluminous Infrared Galaxies, the lower polarization of the weak [OIII]5007 emission line in IRAS 13349+2438 suggests that the scattering grains lie interior to or mixed with the narrow line gas. We construct full radiative transfer models of these systems consisting of a large dusty sphere of modest optical depth illuminated axisymmetrically by a central powerlaw spectrum. We show that this simple model successfully reproduces the qualitative polarization properties of the objects.
Support for this work was provided by NASA through grant number GO-5829-01-94A from the Space Telescope Science Institute, which is operated by Association of Universities for Research in Astronomy Incorporated, under NASA contract NAS5-26555. DCH and KDG acknowledge additional support from the MIPS Project (MIPS Science Development is supported by NASA and the Jet Propulsion Laboratory under contract 960785 to the University of Arizona).
The author(s) of this abstract have provided an email address for comments about the abstract: dhines@as.arizona.edu