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EVOLUTIONARY STATUS OF BRIGHTEST AND YOUNGEST SOURCE IN THE ORION MOLECULAR CLOUD −3 REGION

The brightest continuum source in the Orion molecular cloud-3 region (OMC-3), MMS 6, was observed with the Very Large Array (VLA), the Nobeyama Millimeter Array (NMA), and the Submillimeter Array (SMA). Our data were supplemented by near- to mid-infrared archival data taken by Spitzer Space Telescope. The compact continuum source, MMS 6-main, was detected with an H2 mass of 3.0 M☉ with a size of 510 AU. Despite its compact and well-condensed appearance, neither clear CO outflow, radio jet, nor infrared sources (at a wavelength shorter than 8 μm) were detected at MMS 6-main even with the present high angular resolution and high-sensitivity observations. The derived H2 column density, 2.6 × 1025 cm−2, corresponds to a visual extinction of Av ∼ 15, 000 mag, and the derived number density is at least two orders of magnitude higher than for the other OMC-2/3 continuum sources. The volume density profile of the source was estimated to have a power-law index of 2 or steeper down to a radius of ∼450 AU. The timescale to form a protostar at the center or the timescale elapsed after its formation is estimated to be 830 to 7600 yr. This is much shorter than the typical lifetime of the Class 0/I protostars, which is ∼104–105 yr, suggesting that MMS 6-main is probably in either the earliest stage of the protostellar core or in the latest stage of the prestellar phase.