Revealing a Centrally Condensed Structure in OMC-3/MMS 3 with ALMA High-resolution Observations

Using the Atacama Large Millimeter/submillimeter Array (ALMA), we investigated the peculiar millimeter source MMS 3 located in the Orion Molecular Cloud 3 (OMC-3) region in the 1.3 mm continuum, CO (J = 2–1), SiO (J = 5–4), C¹⁸O (J = 2–1), N₂D⁺ (J = 3–2), and DCN (J = 3–2) emissions. With the ALMA high angular resolution (∼0.″2), we detected a very compact and highly centrally condensed continuum emission with a size of 0.″45 × 0.″32 (P.A. = 0.°22). The peak position coincides with the locations of previously reported Spitzer/IRAC and X-ray sources within their positional uncertainties. We also detected an envelope with a diameter of ∼6800 au (P.A. = 75°) in the C¹⁸O (J = 2–1) emission. Moreover, a bipolar outflow was detected in the CO (J = 2–1) emission for the first time. The outflow is elongated roughly perpendicular to the long axis of the envelope detected in the C¹⁸O (J = 2–1) emission. Compact high-velocity CO gas in the (redshifted) velocity range of 22–30 km s⁻¹, presumably tracing a jet, was detected near the 1.3 mm continuum peak. A compact and faint redshifted SiO emission was marginally detected in the CO outflow lobe. The physical quantities of the outflow in MMS 3 are somewhat smaller than those in other sources in the OMC-3 region. The centrally condensed object associated with the near-infrared and X-ray sources, the flattened envelope, and the faint outflow indicate that MMS 3 harbors a low-mass protostar with an age of ∼10³ yr.