Discovery of a Highly Collimated Molecular Outflow in the Southern Bok Globule BHR 71

Abstract

We report observations of the southern Bok globule BHR 71 in the J = 1 → 0 and J = 2 → 1 lines of 12CO, the J = 1 → 0 lines of 13CO and C18O, and (J, K) = (1, 1) and (2, 2) inversion lines of NH3 made with angular resolution of ~20'' to ~9'. We also report 1.3 mm continuum observations made with SEST with ~20'' resolution. The low angular resolution molecular observations indicate that the globule has a diameter of ~0.5 pc, a kinetic temperature of 11 K, a total mass of ~40 M☉, and an average molecular density of ~9 × 103 cm-3. The high angular resolution observations reveal the presence, near the center of the globule, of a highly collimated bipolar outflow with lobes extending by ~0.3 pc in opposite directions from a strong 1.3 mm continuum source. The morphology and velocity structure of the flow is found to be well described by a biconical outflow that is inclined from the line of sight at an angle of ~84°, has a semi-opening angle of 15°, and in which the gas moves outward with an approximate constant radial velocity (with respect to the cone apex) of ~28 km s-1. The outflow appears to be driven by a very young stellar object with Lbol ~ 9 L☉, whose characteristics at infrared and millimeter wavelengths are similar to those of the so-called Class 0 sources.