DIRECT IMAGING OF A COMPACT MOLECULAR OUTFLOW FROM A VERY LOW LUMINOSITY OBJECT: L1521F-IRS

Studying the physical conditions of very low luminosity objects (VeLLOs; L-bol < 0.1 L-circle dot) is important for understanding the earliest evolutionary stage of protostars and brown dwarfs. We report interferometric observations of the VeLLO L1521F-IRS, in (CO)-C-12 (2-1) line emission and the 1.3 mm continuum emission, using the Submillimeter Array. With the (CO)-C-12 (2-1) 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 approximate to 1000 AU. The estimated outflow mass, maximum outflow velocity, and outflow force are (9.0-80) x 10(-4) M-circle dot, 7.2 km s(-1), and (7.4-66) x 10(-7) M-circle dot 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 first hydrostatic core as well as an undeveloped outflow from the protostar. Detection of an infrared source and compact millimeter continuum emission suggests the presence of the protostar, while its low bolometric luminosity (0.034-0.07 L-circle dot) 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 (approximate to 10(-6) M-circle dot yr(-1)), which may imply that L1521F-IRS is currently in a low activity phase.