Resolved Molecular Gas in a Quasar Host Galaxy at Redshift z=6.42

摘要

We present high-resolution VLA observations of the molecular gas in the hostgalaxy of the highest redshift quasar currently known, SDSS J1148+5251(z=6.42). Our VLA data of the CO(3-2) emission have a maximum resolution of0.17'' x 0.13'' (~1 kpc), and enable us to resolve the molecular gas emissionboth spatially and in velocity. The molecular gas in J1148+5251 is extended toa radius of 2.5 kpc, and the central region shows 2 peaks, separated by 0.3''(1.7 kpc). These peaks account for about half of the total emission, while theremainder is more extended. Each of these unresolved peaks contains a moleculargas mass of ~5 x 10^9 M_sun (similar to the total mass found in nearby ULIRGS)and has an intrinsic brightness temperature of ~35 K (averaged over the 1kpc-sized beam), comparable to what is found in nearby starburst centers.Assuming that the molecular gas is gravitationally bound, we estimate adynamical mass of ~4.5 x 10^10 M_sun within a radius of 2.5 kpc (~5.5 x 10^10M_sun if corrected for a derived inclination of i~65 deg.). This dynamical massestimate leaves little room for matter other than the detected molecular gas,and in particular the data are inconsistent with a ~10^12 M_sun stellar bulgewhich would be predicted based on the M_BH-sigma_bulge relation. This findingmay indicate that black holes form prior to the assembly of the stellar bulgesand that the dark matter halos are less massive than predicted based on theblack hole/bulge mass relationship.