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 a 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),
C$^{18}$O ($J$=2-1), N$_2$D$^+$ ($J$=3-2), and DCN ($J$=3-2) emissions. With
the ALMA high angular resolution ($\sim$0''.2), we detected a very compact and
highly centrally condensed continuum emission with a size of 0''.45 $\times$
0''.32 (P.A.=0.22$^\circ$). 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 $\sim$6800 au
(P.A.=75$^\circ$) in the C$^{18}$O ($J$=2-1) emission. Moreover, a bipolar
outflow was detected in the CO ($J$=2-1) emission for the first time. The
outflow elongates roughly perpendicular to the long axis of the envelope
detected in the C$^{18}$O ($J$=2-1) emission. Compact high-velocity CO gas in
the (red-shifted) velocity range of 22-30 km s$^{-1}$, presumably tracing a
jet, was detected near the 1.3 mm continuum peak. A compact and faint
red-shifted SiO emission was marginally detected on the CO outflow lobe. The
physical quantities of the outflow in MMS 3 are relatively 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
$\sim$10$^3$ yr.
