On the Relation between the Inclination Angle of the Accretion Disk and the Broad-line Region in Active Galactic Nuclei

Models of active galactic nuclei often invoke a close physical association between the broad-line region and the accretion disk. We evaluate this theoretical expectation by investigating the relationship between the inclination angle of the BLR (${\theta }_{\mathrm{B}\mathrm{L}\mathrm{R}}$) and the inclination angle of the inner accretion disk (${\theta }_{\mathrm{d}\mathrm{i}\mathrm{s}\mathrm{k}}$). For a sample of eight active galactic nuclei that have published values of ${\theta }_{\mathrm{B}\mathrm{L}\mathrm{R}}$ estimated from dynamical modeling of the BLR based on velocity-resolved reverberation mapping experiments, we analyze high-quality, joint XMM-Newton and NuSTAR X-ray observations to derive new, robust measurements of ${\theta }_{\mathrm{d}\mathrm{i}\mathrm{s}\mathrm{k}}$ through broadband (0.3–78,keV) reflection spectroscopy. We find a strong, positive correlation between ${\theta }_{\mathrm{B}\mathrm{L}\mathrm{R}}$ and ${\theta }_{\mathrm{d}\mathrm{i}\mathrm{s}\mathrm{k}}$ (Pearson correlation coefficient 0.856, $p$-value 0.007), although Monte Carlo simulations indicate that the level of significance is only marginal ($<3\sigma$). Nevertheless, the nearly linear relation between ${\theta }_{\mathrm{B}\mathrm{L}\mathrm{R}}$ and ${\theta }_{\mathrm{d}\mathrm{i}\mathrm{s}\mathrm{k}}$ suggests of a possible physical alignment between the accretion disk and the BLR. Future studies with a larger and more homogeneous sample are needed to confirm the correlation and refine our understanding of the structure and dynamics of the central regions of active galaxies.