We present the results of high signal-to-noise ratio VLT spectropolarimetry of a representative sample of 25 bright type 1 AGN at z < 0.37, of which nine are radio-loud. The sample covers uniformly the 5100 Å optical luminosity at L5100 ∼ 1044−1046 erg s−1, and H α width at FWHM ∼ 1000−10 000 $\rm {\, km \, s}^{-1}$. We derive the continuum and the H α polarization amplitude, polarization angle, and angle swing across the line, together with the radio properties. We find the following: (1) The broad line region (BLR) and continuum polarization are both produced by a single scattering medium. (2) The scattering medium is equatorial and at right angle to the system axis. (3) The scattering medium is located at or just outside the BLR. The continuum polarization and the H α polarization angle swing, can both serve as an inclination indicator. The observed line width is found to be affected by inclination, which can lead to an underestimate of the black hole mass by a factor of ∼5 for a close-to face-on view. The line width measured in the polarized flux overcomes the inclination bias and provides a close-to equatorial view of the BLR in all AGN, which allows to reduce the inclination bias in the BLR based black hole mass estimates.

中文翻译：

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低红移类星体的光谱偏振测量：偏振的起源和对黑洞质量估计的影响

我们展示了 25 个明亮的 1 型 AGN 的代表性样品在 z <; 0.37，其中九个是无线电响亮的。该样品均匀地覆盖了 L5100 ∼ 1044−1046 erg s−1 处的 5100 Å 光度，以及 FWHM ∼ 1000−10 000 $\rm {\, km \, s}^{-1}$ 处的 H α 宽度。我们推导出了连续谱和 H α 极化幅度、极化角和跨线的角度摆动，以及无线电特性。我们发现以下内容：（1）宽线区域（BLR）和连续偏振均由单一散射介质产生。(2) 散射介质是赤道的，与系统轴成直角。(3) 散射介质位于或刚好在 BLR 之外。连续偏振和H α 偏振角摆动，都可以作为倾角指示器。发现观察到的线宽受倾斜度的影响，这可能导致近距离观察时低估黑洞质量约 5 倍。在极化通量中测量的线宽克服了倾角偏差，并提供了所有 AGN 中 BLR 的接近赤道视图，这允许减少基于 BLR 的黑洞质量估计中的倾角偏差。