Warm Gas in the Vicinity of a Supermassive Black hole 13 Billion Years Ago

Quasars, powered by supermassive black holes (SMBH), are among the brightest objects in the universe. In the vicinity of an SMBH, X-ray photons from an active galactic nucleus (AGN) can heat the surrounding gas to several hundred kelvin. Here we report observations of dust continuum and CO J=13-12 and J=14-13 line emissions at a resolution of 130 parsecs in a luminous quasar at z=6. We successfully detected these high-J CO line emissions from warm gas in a compact disk component. The CO luminosity ratio in the central region of the compact disk is consistent with theoretical models in which X-ray heating dominates the CO excitation and the gas column density is as high as 10${}^{25}$ cm${}^{-2}$. This demonstrates that high-resolution observations of high-J CO lines are promising ways to identify extremely dust-obscured quasars in the early universe.