Synchronized Coevolution between Supermassive Black Holes and Galaxies over the Last Seven Billion Years as Revealed by Hyper Suprime-Cam

We measure the evolution of the MBH-M relation using 584 uniformly selected Sloan Digital Sky Survey quasars at 0.2 < z < 0.8. The black hole masses (MBH) are derived from the single-epoch virial mass estimator using the Hβ emission line and span the range . The host-galaxy stellar masses (M*), which cover the interval, are determined by performing two-dimensional quasar-host decomposition of the Hyper Suprime-Cam images and spectral energy distribution fitting. To quantify sample selection biases and measurement uncertainties on the mass terms, a mock quasar sample is constructed to jointly constrain the redshift evolution of the MBH-M* relation and its intrinsic scatter (σ μ ) through forward modeling. We find that the level of evolution is degenerate with σ μ , such that both a positive mild evolution (i.e., increases with redshift) with a small σ μ and a negative mild evolution with a larger σ μ are consistent with our data. The posterior distribution of σ μ enables us to put a strong constraint on the intrinsic scatter of the MBH-M* relation, which has a best inference of 0.25-0.04+0.03 dex, consistent with the local value. The redshift evolution of the MBH-M* relation relative to the local relation is constrained to be (1+z)0.12-0.27+0.28, in agreement with no significant evolution since z ∼ 0.8. The tight and unevolving MBH-M* relation is suggestive of a coupling through active galactic nuclei feedback or/and a common gas supply at work, thus restricting the mass ratio of galaxies and their black holes to a limited range. Given the considerable stellar disk component, the MBH-Mbulge relation may evolve as previously seen at higher redshifts.