Posterior PDFs for the total mass of BBH (M_••) as a function of i_BLR (black) and i_orb (red). Panels show different luminosity fractions of the secondary BH with f₂ = 100% (left), 95% (middle), and 90% (right) assumed in the Doppler boosting hypothesis (D’Orazio et al. 2015). In each panel, the black shaded region with the 68.3% and 95.4% confidence levels overlapped by black solid lines show the PDF result (p(i_BLR, M_••)) obtained from stacking the PDFs of the Lyα+N V, C IV, and C III]broad emission lines with S/N >  3. As a comparison, the top right shaded region correspond to mass ratios q = 0.0, 0.05, 0.1, and 0.2 (from pink to dark red).