Direct Imaging of a Compact Molecular Outflow from a Very Low-luminosity
  Object; L1521F-IRS
  We report interferometric observations of the VeLLO L1521F-IRS, in 12CO (2-1)
line emission and the 1.3 mm continuum emission, using the Submillimeter Array
(SMA). With the 12CO high-resolution observations, we have spatially resolved a
compact but poorly collimated molecular outflow associated with L1521F-IRS for
the first time. The blueshifted and redshifted lobes are aligned along the east
and west side of L1521F-IRS with a lobe size of ~1000 AU. The estimated outflow
mass, maximum outflow velocity, and outflow force are (9.0-80)x10^{-4} M_{sol},
7.2 km s^{-1}, and (7.4-66)x10^{-7} M_{sol} km s^{-1} yr^{-1}, respectively.
The estimated outflow parameters such as size, mass, and momentum rate are
similar to values derived for other VeLLOs, and are located at the lower end of
values compared to previously studied outflows associated with low- to
high-mass star forming regions. Low-velocity less collimated (1.5 km
s^{-1}/1200 AU) and higher-velocity compact (4.0 km s^{-1}/920 AU) outflow
components are suggested by the data. These velocity structures are not
consistent with those expected in the jet driven or wind driven outflow models,
perhaps suggesting a remnant outflow from the FHSC as well as an undeveloped
outflow from the protostar. Detection of an infrared source and compact
millimeter continuum emission suggest the presence of the protostar, while its
low bolometric luminosity (0.034-0.07 L$_{\odot}$), and small outflow, suggests
that L1521F is in the earliest protostellar stage ($<10^{4}$ yr) and contains a
substellar mass object. The bolometric (or internal) luminosity of L1521F-IRS
suggests that the current mass accretion rate is an order-of-magnitude lower
than expected in the standard mass accretion model (~10^{-6} M_{sol} yr^{-1}),
which may imply that L1521F-IRS is currently in a low activity phase.
