Probing the interstellar medium and star formation of the Most Luminous Quasar at z=6.3

Abstract: We report new IRAM/PdBI, JCMT/SCUBA-2, and VLA observations of the ultraluminous quasar SDSSJ010013.02+280225.8 (hereafter, J0100+2802) at z=6.3, which hosts the most massive supermassive black hole (SMBH) of 1.24x10^10 Msun known at z>6. We detect the [C II] 158 $\mu$m fine structure line and molecular CO(6-5) line and continuum emission at 353 GHz, 260 GHz, and 3 GHz from this quasar. The CO(2-1) line and the underlying continuum at 32 GHz are also marginally detected. The [C II] and CO detections suggest active star formation and highly excited molecular gas in the quasar host galaxy. The redshift determined with the [C II] and CO lines shows a velocity offset of ~1000 km/s from that measured with the quasar Mg II line. The CO (2-1) line luminosity provides direct constraint on the molecular gas mass which is about (1.0+/-0.3)x10^10 Msun. We estimate the FIR luminosity to be (3.5+/-0.7)x10^12 Lsun, and the UV-to-FIR spectral energy distribution of J0100+2802 is consistent with the templates of the local optically luminous quasars. The derived [C II]-to-FIR luminosity ratio of J0100+2802 is 0.0010+/-0.0002, which is slightly higher than the values of the most FIR luminous quasars at z~6. We investigate the constraint on the host galaxy dynamical mass of J0100+2802 based on the [C II] line spectrum. It is likely that this ultraluminous quasar lies above the local SMBH-galaxy mass relationship, unless we are viewing the system at a small inclination angle.