Resolved Molecular Gas Emission in J1148+5251: Fueling a Starburst at z = 6.4

摘要

We present high-resolution VLA observations of the molecular gas in the host galaxy 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 of 0.17 × 0.13 (1 kpc), and enable us to resolve the molecular gas emission both spatially and in velocity. The molecular gas in J1148+5251 is extended to a 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 the remainder is more extended. Each of these unresolved peaks contains a molecular gas mass of ~ 5 × 109 M (similar to the total mass found in nearby ULIRGS) and has an intrinsic brightness temperature of ~ 35 K (averaged over the 1 kpc-sized beam), comparable to what is found in nearby starburst centers. Assuming that the molecular gas is gravitationally bound, we estimate a dynamical mass of ~ 4.5 × 1010 M within a radius of 2.5 kpc (~ 5.5 × 1010 M if corrected for a derived inclination of i ~ 65°). This dynamical mass estimate leaves little room for matter other than the detected molecular gas, and in particular the data are inconsistent with a ~ 1012 M stellar bulge which would be predicted based on the MBH – bulge relation. The presence of abundant molecular gas in the host galaxy of SDSS J1148+5251 provides strong evidence that massive star formation is going on in this system (~ 870 Myr after the Big Bang).