Spatially Resolved Interstellar Medium and Highly Excited Dense Molecular Gas in the Most Luminous Quasar at z =6.327

Among more than 200 quasars known at z ⪆6, only one object, J0100+2802 (z =6.327), was found hosting a >10¹⁰ M _o supermassive black hole. In order to investigate the host galaxy properties of J0100+2802, we performed multi-band ALMA observations, aiming at mapping the dust continuum, [C ii] and CO(6-5) emission lines with subkiloparsec scale resolution, as well as detecting high-J CO lines in CO(11-10), CO(10-9), and CO(7-6). The galaxy size is measured to be R _major =3.6 +0.2 kpc from the high-resolution continuum observations. No ordered motion on kiloparsec scales was found in either the [C ii] or the CO(6-5) emission. The velocity dispersion is measured to be 161 +7 km s^-1, which is about three times smaller than that estimated from the local M-σ relation. In addition, we found that the CO emission is more concentrated (a factor of 1.8 + 0.4) than the [C ii] emission. Together with CO(2-1) detected by the Very Large Array (VLA), we measured the CO spectral line energy distribution, which is best fit by a two-component model that includes a cool component at ∼24 K with a density of cm^-3, and a warm component at ∼224 K with a density of cm^-3. We also fit the dust continuum with a graybody model. This indicated that the continuum has either a high dust emissivity β ⪆2 or a hot dust temperature T _dust ⪆60 K, or a combination of these two factors. The highly excited CO emission and hot dust temperature suggest that the powerful active galactic nucleus in J0100+2802 could contribute to the gas and dust heating, but future observations are needed to confirm this.