IUE Spectrophotometry and Optical Spectropolarimetry of the Extreme FeII-Emitting QSO IRAS 07598+6508

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Session 105 -- Broad Absorption Line Quasars
Display presentation, Saturday, January 1, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[105.08] IUE Spectrophotometry and Optical Spectropolarimetry of the Extreme FeII-Emitting QSO IRAS 07598+6508

Wills, B.J. \& Hines, D.C. (UT Austin)

We find Broad Absorption Lines (BALs) from high- and low-ionization species (Ly$\alpha$, NV, SiIV, AlIII$\lambda1857$, MgII, NaI). Thus IRAS 07598+6508 is a member of the rare class of low-ionization BAL QSOs. Our optical spectropolarimetry shows complex wavelength-dependent percentage polarization, a featureless, power-law polarized flux spectrum ($\alpha_\nu\approx 0$), and wavelength-independent position angle. The emission lines, including FeII, are essentially unpolarized. Unlike the total flux spectrum, the polarized flux spectrum does not show the broad NaI absorption.

The Spectral Energy Distribution (SED) is consistent with a standard QSO (or high-ionization BALQSO) spectrum reddened by E(B-V) = 0.12 $\pm 0.02$ assuming an SMC extinction law, consistent with SEDs of other low-ionization BALQSOs (Sprayberry \& Foltz 1992). We use the Boroson \& Green (1992) method to deblend the strong optical FeII emission, and find HI equivalent widths among the smallest measured for non-BALQSOs, and H$\alpha/$H$\beta \approx 6$ suggesting a line reddening E(B-V) = 0.45.

We explain the polarization with a consistent model in which a typical QSO featureless continuum source and Broad Emission Line Region are partially obscured from direct view by a region (torus) of dusty gas. The direct view of the QSO is highly reddened [E(B-V)$\approx 0.45$] and passes through the BAL region. Continuum emission from a central source emerging at the poles is scattered by dust near the Broad Emission Line Region into our line of sight and does not pass through the BALR. In the observed total light spectrum, the unreddened scattered flux causes us to underestimate the SED reddening, and reduces the HI equivalent widths. A strong 2200\AA\ ``emission'' feature in the scattered flux spectrum could cancel any 2200\AA\ feature in the direct spectrum. We suggest that such a scattering model may apply to all low-ionization BALQSOs, and may explain the universally red low-ionization BALQSO SEDs but lack of 2200\AA\ features.

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