(a) Scatterplot of M_BH and M_gas for our sample of PG (squares), IR (circles), and HE (triangles) quasars. Colors indicate the Eddington ratio: λ_Edd > 1 (red), 1 ≥ λ_Edd > 0.1 (green), and 0.1 ≥ λ_Edd (blue). The dashed diagonal lines indicate that M_gas is 1, 10, 100, and 1000 times M_BH. One can estimate M_gas/M_bulge from these lines by assuming the local co-evolutionary relationship such as M_BH ≃ 0.005 × M_bulge (Kormendy & Ho 2013). The black cross shows the typical uncertainty (0.3 dex for both M_BH and M_gas). (b) As (a), but for the subsample (see subsection 3.1 for details).