2021MNRAS.500.4989N

Recent studies show that a universal relation between black hole (BH) growth and stellar mass (M_*) or star formation rate (SFR) is an oversimplification of BH-galaxy coevolution, and that morphological and structural properties of host galaxies must also be considered. Particularly, a possible connection between BH growth and host-galaxy compactness was identified among star-forming (SF) galaxies. Utilizing ≃6300 massive galaxies with I_814W < 24 at z < 1.2 in the Cosmic Evolution Survey (COSMOS) field, we perform systematic partial correlation analyses to investigate how sample-averaged BH accretion rate ( ) depends on host-galaxy compactness among SF galaxies, when controlling for morphology and M_* (or SFR). The projected central surface mass density within 1 kpc, Σ₁, is utilized to represent host-galaxy compactness in our study. We find that the -Σ₁ relation is stronger than either the -M_* or -SFR relation among SF galaxies, and this -Σ₁ relation applies to both bulge-dominated galaxies and galaxies that are not dominated by bulges. This -Σ₁ relation among SF galaxies suggests a link between BH growth and the central gas density of host galaxies on the kpc scale, which may further imply a common origin of the gas in the vicinity of the BH and in the central ∼kpc of the galaxy. This -Σ₁ relation can also be interpreted as the relation between BH growth and the central velocity dispersion of host galaxies at a given gas content (i.e. gas mass fraction), indicating the role of the host-galaxy potential well in regulating accretion on to the BH.