400 pc Imaging of a Massive Quasar Host Galaxy at a Redshift of 6.6

Abstract: We report high spatial resolution (~0.076", 410pc) Atacama Large Millimeter/submillimeter Array imaging of the dust continuum and the ionized carbon line [CII] in a luminous quasar host galaxy at z=6.6, 800 million years after the big bang. Based on previous studies, this galaxy hosts a ~1x10^9 M_sun black hole and has a star-formation rate of ~1500 M_sun/yr. The unprecedented high resolution of the observations reveals a complex morphology of gas within 3kpc of the accreting central black hole. The gas has a high velocity dispersion with little ordered motion along the line of sight, as would be expected from gas accretion that has yet to settle in a disk. In addition, we find the presence of [CII] cavities in the gas distribution (with diameters of ~0.5kpc), offset from the central black hole. This unique distribution and kinematics cannot be explained by a simple model. Plausible scenarios are that the gas is located in a truncated or warped disk, or the holes are created by interactions with nearby galaxies or due to energy injection into the gas. In the latter case, the energy required to form the cavities must originate from the central active galactic nucleus, as the required energy far exceeds the energy output expected from supernovae. This energy input into the gas, however, does not inhibit the high rate of star-formation. Both star-formation and black hole activity could have been triggered by interactions with satellite galaxies; our data reveal three additional companions detected in [CII] emission around the quasar.