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 (AGN) often invoke a close physical association between the broad-line region (BLR) and the accretion disk. We evaluate this theoretical expectation by investigating the relationship between the inclination angle of the BLR (θBLR) and the inclination angle of the inner accretion disk (θdisk). For a sample of eight AGN that have published values of θBLR 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 θdisk through broadband (0.3–78 keV) reflection spectroscopy. Mock spectra demonstrate that the results are generally not strongly affected by warm absorbers or the model used to fit the soft-band data. We find a strong, positive correlation between θBLR and θdisk (Pearson correlation coefficient 0.856, p-value 0.007), although Monte Carlo simulations indicate that the level of significance is only marginal (<3σ). Nevertheless, the nearly linear relation between θBLR and θdisk suggests 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.