A Spatially Resolved [CII] Survey of 31 z~7 Massive Galaxies Hosting Luminous Quasars

The [CII] 158 μm emission line and the underlying far-infrared (FIR) dust continuum are important tracers for studying star formation and kinematic properties of early galaxies. We present a survey of the [CII] emission lines and FIR continua of 31 luminous quasars at $z>6.5$ using the Atacama Large Millimeter Array (ALMA) and the NOrthern Extended Millimeter Array (NOEMA) at sub-arcsec resolution. This survey more than doubles the number of quasars with [CII] and FIR observations at these redshifts and enables statistical studies of quasar host galaxies deep into the epoch of reionization. We detect [CII] emission in 27 quasar hosts with a luminosity range of L[CII]=(0.3-5.5)×10⁹~L_ and detect the FIR continuum of 28 quasar hosts with a luminosity range of LFIR=(0.5-13.0)×10¹²~L_. Both L[CII] and LFIR are correlated (ρ0.4) with the quasar bolometric luminosity, albeit with substantial scatter. The quasar hosts detected by ALMA are clearly resolved with a median diameter of ~5 kpc. About 40% of the quasar host galaxies show a velocity gradient in [CII] emission, while the rest show either dispersion-dominated or disturbed kinematics. Basic estimates of the dynamical masses of the rotation-dominated host galaxies yield Mdyn=(0.1-7.5)×10¹¹~M_. Considering our findings alongside those of literature studies, we found that the ratio between MBH and Mdyn is about ten times higher than that of local MBH-Mdyn relation on average but with substantial scatter (the ratio difference ranging from ~0.6 to 60) and large uncertainties.