The Broad-Line Region Size-Luminosity Relation in AGN Constrained by the Viewing Angle with the FRADO Model
Abstract
We investigate the Hβ broad-line region (BLR) size-luminosity (RBLR-L5100) relation of active galactic nuclei (AGN) using a Bayesian viewing angle inference framework based on the Failed Radiatively Accelerated Dusty Outflow (FRADO) model. First, we update the FRADO model by introducing a phase factor to account for the anisotropic visibility of the illuminated cloud surface. Second, we construct a Bayesian framework to constrain the viewing angle by matching the FRADO-based RBLR to the measured Hβ lags of 151 AGN from Wang & Woo (2024). We successfully reproduce the slope and intrinsic scatter of the observed RBLR-L5100 relation, finding that the inferred viewing angles are broadly consistent with the estimates from dynamical modeling of velocity-resolved reverberation data, albeit with substantial scatter. As the observed Hβ time lag and line velocity depend on the viewing angle, the black hole mass (MBH) calibrated from our work is typically larger than the reverberation-mapping estimates using an average virial factor. Our results provide a physically motivated interpretation of the RBLR-L5100 relation and the systematic uncertainties in reverberation and single-epoch MBH estimates.
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BibTeX
@misc{myong2026broadline,
title = {{The Broad-Line Region Size-Luminosity Relation in AGN Constrained by the Viewing Angle with the FRADO Model}},
author = {Junhee Myong and Jong-Hak Woo and Mohammad-Hassan Naddaf and Bożena Czerny and Jimin Kim},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.41594},
eprint = {2610.41594},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.41594},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The Broad-Line Region Size-Luminosity Relation in AGN Constrained by the Viewing Angle with the FRADO Model
AU - Junhee Myong
AU - Jong-Hak Woo
AU - Mohammad-Hassan Naddaf
AU - Bożena Czerny
AU - Jimin Kim
PY - 2026
DA - 2026/10/30
PB - arXiv
DO - 10.48550/arxiv.2610.41594
UR - https://arxiv.org/abs/2610.41594
AB - We investigate the Hβ broad-line region (BLR) size-luminosity (R_BLR-L_5100) relation of active galactic nuclei (AGN) using a Bayesian viewing angle inference framework based on the Failed Radiatively Accelerated Dusty Outflow (FRADO) model. First, we update the FRADO model by introducing a phase factor to account for the anisotropic visibility of the illuminated cloud surface. Second, we construct a Bayesian framework to constrain the viewing angle by matching the FRADO-based R_BLR to the measured Hβ lags of 151 AGN from Wang & Woo (2024). We successfully reproduce the slope and intrinsic scatter of the observed R_BLR-L_5100 relation, finding that the inferred viewing angles are broadly consistent with the estimates from dynamical modeling of velocity-resolved reverberation data, albeit with substantial scatter. As the observed Hβ time lag and line velocity depend on the viewing angle, the black hole mass (M_BH) calibrated from our work is typically larger than the reverberation-mapping estimates using an average virial factor. Our results provide a physically motivated interpretation of the R_BLR-L_5100 relation and the systematic uncertainties in reverberation and single-epoch M_BH estimates.
ER -