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With the Submillimeter Array, the brightest (sub)millimeter continuum sourcein the OMC-2/3 region, MMS 6, has been observed in the 850 um continuumemission with approximately 10 times better angular resolution than previousstudies (~0.3"; ~120 AU at Orion). The deconvolved size, the mass, and thecolumn density of MMS 6-main are estimated to be 0.32"x0.29" (132 AUx120 AU),0.29 Mo, and 2.1x10^{25} cm^{-2}, respectively. The estimated extremely highmean number density, 1.5x10^{10} cm^{-3}, suggests that MMS 6-main is likelyoptically thick at 850 um. We compare our observational data with threetheoretical core models: prestellar core, protostellar core + disk-likestructure, and first adiabatic core. These comparisons clearly show that theobservational data cannot be modeled as a simple prestellar core with a gastemperature of 20 K. A self-luminous source is necessary to explain theobserved flux density in the (sub)millimeter wavelengths. Our recent detectionof a very compact and energetic outflow in the CO (3-2) and HCN (4-3) lines,supports the presence of a protostar. We suggest that MMS 6 is one of the firstcases of an intermediate mass protostellar core at an extremely young stage. Inaddition to the MMS 6-main peak, we have also spatially resolved a number ofspiky structures and sub-clumps, distributed over the central 1000 AU. Themasses of these sub-clumps are estimated to be 0.066-0.073 Mo, which are on theorder of brown dwarf masses. Higher angular resolution and higher sensitivityobservations with ALMA and EVLA will reveal the origin and nature of thesestructures such as whether they are originated from fragmentations, spiralarms, or inhomogeneity within the disk-like structures/envelope.

Spatially Resolving Substructures within the Massive Envelope around an Intermediate-mass Protostar: MMS 6/OMC-3