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

Abstract

Abstract We measure the evolution of the  BH –  ⋆ relation using 584 uniformly selected Sloan Digital Sky Survey quasars at 0.2 < z < 0.8. The black hole masses (  BH ) are derived from the single-epoch virial mass estimator using the Hβ emission line and span the range 7.0 < log  BH / M ⊙ < 9.5 . The host-galaxy stellar masses (  ⋆ ), which cover the interval 10.0 < log  ⋆ / M ⊙ < 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  BH –  ⋆ 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.,  BH /  ⋆ 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  BH –  ⋆ relation, which has a best inference of 0.25 − 0.04 + 0.03 dex, consistent with the local value. The redshift evolution of the  BH –  ⋆ 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  BH –  ⋆ 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  BH –  bulge relation may evolve as previously seen at higher redshifts.