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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.
The role of accretion disks in the formation of low-mass stars has been well assessed by means of high angular resolution observations at various wavelengths. These findings confirm the prediction that conservation of angular momentum during the coll
The Spitzer-GLIMPSE point source catalog and images have been used to study a sample of 381 massive protostellar candidates. IRAC-Point source photometry was used to analyse colours, magnitudes and spectral indicies of the infrared counterparts (IRCs
A strong signature of a circumstellar disc around a high-mass protostar has been inferred from high resolution methanol maser observations in NGC7538-IRS1 N. This interpretation has however been challenged with a bipolar outflow proposed as an altern
We present the results of CS J=2-1 mapping observations towards 39 massive star-forming regions selected from the previous CO line survey of cold IRAS sources with high-velocity CO flows along the Galactic plane (Yang et al. 2002). All sources are de
We observe 84 candidate young high-mass sources in the rare isotopologues C17O and C18O to investigate whether there is evidence for depletion (freeze-out) towards these objects. Observations of the J=2-1 transitions of C18O and C17O are used to deri