Velocity-resolved Ionization Mapping of the Broad-line Region. II. Signatures of Eccentric Broad-line Regions from a Quantitative Photoionization-Based Model

Velocity-resolved reverberation mapping (RM) is one of the most powerful tools for probing the geometry and kinematics of the broad-line region in active galactic nuclei. However, its interpretation may be non-unique, as similar velocity-delay signatures can arise from different combinations of BLR geometry and kinematics. To address this degeneracy, this series of studies develops velocity-resolved ionization mapping (IM) as a complementary technique. In this second paper of the series, we construct photoionization-based BLR models to quantitatively demonstrate the diagnostic power of the joint RM+IM framework. We calculate local and emissivities with Cloudy, couple them with disk-like BLR models, and generate synthetic velocity-dependent line fluxes, lags, and Balmer decrements. The model reproduces the observed anti-correlation between the integrated BD and the incident ionizing continuum, with scatter naturally introduced by reverberation delays. We show that a virialized elliptical BLR can produce diverse velocity-delay maps and velocity-resolved lags that mimic RM signatures commonly attributed to virialized motion, inflow, or outflow. In contrast, the velocity-resolved BD is sensitive to the symmetry of the BLR gas distribution, providing a key diagnostic for distinguishing eccentric geometry from non-virial motions. Through proof-of-concept comparisons with one double-peaked and one single-peaked AGN, we show that an elliptical-disk BLR can simultaneously reproduce the observed line profiles, velocity-resolved lags, and velocity-resolved BDs. These results provide a quantitative basis for IM, support the presence of eccentric BLR structures in AGNs, and demonstrate the potential of joint RM+IM analyses to break the BLR geometry-kinematics degeneracy.