2003ApJ...590L..45S

We report the detection of a massive rotating disk around the high-mass Class 0 candidate NGC 7538S. The disk is well resolved with the Berkeley-Illinois-Maryland Association array (θ_A=3".7) in the 3.4 mm continuum and in H¹³CN J=1⟶0. It is seen nearly edge-on and has a size of ∼30,000 AU. A young, powerful outflow perpendicular to the rotating disk is mapped in SiO J=2⟶1 and HCO⁺ J=1⟶0. The dynamical age of the outflow is ≤10,000 yr. The velocity gradient seen in H¹³CN is consistent with Keplerian rotation. Assuming that the gas is gravitationally bound, the mass of the central object is ∼40 M_☉. The mass of the continuum ``disk'' is ≥100 M_☉ and has a luminosity of ∼10⁴ L_☉. H¹³CN gives a mass of ∼400 M_☉for the rotating disk and of ∼1000 M_☉for the extended (20") envelope. Our observations confirm that this is an extremely massive protostar in its earliest stages.