2013ApJ...778...47S

Black-hole-galaxy scaling relations provide information about the coevolution of supermassive black holes and their host galaxies. We compare the black-hole mass-circular-velocity (M_BH-V_c) relation with the black-hole-mass-bulge-stellar-velocity-dispersion (M_BH-σ_*) relation to see whether the scaling relations can passively emerge from a large number of mergers or require a physical mechanism, such as feedback from an active nucleus. We present Very Large Array H I observations of five galaxies, including three water megamaser galaxies, to measure the circular velocity. Using 22 galaxies with dynamical M_BH measurements and V_c measurements extending to large radius, our best-fit M_BH-V_crelation, logM_BH = α + βlog(V_c/200km/s) , yields α = 7.43_–0.13^+0.13, β = 3.68_–1.20^+1.23, and an intrinsic scatter ∈_int = 0.51_–0.09^+0.11. The intrinsic scatter may well be higher than 0.51, as we take great care to ascribe conservatively large observational errors. We find comparable scatter in the M_BH-σ_* relations, ∈_int = 0.48_–0.08^+0.10., while pure merging scenarios would likely result in a tighter scaling with the dark halo (as traced by V_c) properties rather than the baryonic (σ_*) properties. Instead, feedback from the active nucleus may act on bulge scales to tighten the M_BH-σ_* relation with respect to the M_BH-V_crelation, as observed.