  While most sources above 10^5Lsun have already formed an Ultracompact HII
region (UCHII), this is not necessarily the case for sources of lower
luminosity. Characterizing sources in the transition phase, i.e., very luminous
objects without any detectable free-free emission, is important for a general
understanding of massive star formation. Therefore, we observed the luminous
High-Mass Protostellar Object IRAS23151+5912 with the Submillimeter Array at
875mum in the submm continuum and spectral line emission at sub-arcsecond
resolution. The 875mum submm continuum emission has been resolved into at least
two condensations. The previously believed driving source of one of the
outflows, the infrared source IRS1, is ~0.9'' offset from the main submm peak.
Over the entire 4GHz bandwidth we detect an intermediate dense spectral line
forest with 27 lines from 8 different species, isotopologues or
vibrationally-torsionally excited states. Temperature estimates based on the
CH3OH line series result in values of T(Peak1)~150+-50K and T(Peak2)~80~30K for
the two submm peak positions, respectively. The SiO(8-7) red- and blue-shifted
line maps indicate the presence of two molecular outflows. In contrast, the
vibrationally-torsionally excited CH3OH line exhibits a velocity gradient
approximately perpendicular to one of the outflows. With a size of
approximately 5000AU and no Keplerian rotation signature, this structure does
not resemble a genuine accretion disk but rather a larger-scale rotating toroid
that may harbor a more common accretion disk at its so far unresolved center.
