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 M-BH-M-* relation using 584 uniformly-selected SDSS quasars at 0.2<z<0.8. The black-hole masses (M-BH) are derived from the single-epoch virial mass estimator using the H beta emission line, and span the range 7.0<log M-BH/M-circle dot<9.5. The host-galaxy stellar masses (M-*), which cover the interval 10.0<log M-*/M-circle dot<11.5, 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 M-BH-M-* relation and its intrinsic scatter (sigma(mu)) through forward modeling. We find that the level of evolution is degenerate with sigma(mu), such that both positive mild evolution (i.e, M-BH/M-* increases with redshift) with a small sigma(mu), and negative mild evolution with a larger sigma(mu) are consistent with our data. The posterior distribution of sigma(mu) enables us to put a strong constraint on the intrinsic scatter of the M-BH-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 M-BH-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 similar to 0.8. The tight and non-evolving M-BH-M-* relation is suggestive of a coupling through AGN 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 M-BH-M-bulge relation may evolve as previously seen at higher redshifts.