Outflows, Accretion, and Clustered Protostellar Cores around a Forming O
  Star
  We present a Submillimeter Array study in the 1.3 mm waveband of the NGC 7538
IRS 1--3 massive star-forming region. The brightest core in the mm continuum
map, MM1, harbors the IRS 1 young O star. The core has a gas temperature of
about 245 K and shows spatially unresolved emission in complex organic
molecules, all typical of a hot molecular core. Toward MM1, redshifted
absorption is seen in molecular lines with different energies above the ground
state. This absorption probes inward motion of the dense gas toward the central
young O star, and the estimated mass accretion rate reaches 10^{-3} Msun/yr.
Multiple outflows are seen in the CO and 13CO maps. The gas mass of 50 Msun and
mass outflow rate of 2.5 by 10^{-3} Msun/yr measured in CO line wings are
dominated by the MM1 outflow, which is most likely driven by a fast wide-angle
wind. Apart from MM1, we discover eight new dusty cores, MM2--9, within a
projected distance of 0.35 pc from MM1. These cores show no counterpart in
infrared or radio continuum emission, while seven of them appear to be forming
intermediate- to high-mass stars. This manifests a deeply embedded star-forming
component of the parent cloud of IRS 1--3. Apparently we are observing a
Trapezium system in formation, and the system is presumably surrounded by a
cluster of lower mass stars.
