Molecular outflow launched beyond the disk edge

Artikel i vetenskaplig tidskrift, 2017

One of the long-standing problems of star formation is the excess of angular momentum of the parent molecular cloud. In the classical picture, a fraction of angular momentum of the circumstellar material is removed by the magneto-centrifugally driven disk wind that is launched from a wide region throughout the disk. In this work, we investigate the kinematics in the envelope-disk transition zone of the Class I object BHB07-11, in the B59 core. For this purpose, we used the Atacama Large Millimeter/submillimeter Array in extended configuration to observe the thermal dust continuum emission (lambda(0) similar to 1.3 mm) and molecular lines (CO, (CO)-O-18 and H2CO), which are suitable tracers of disk, envelope, and outflow dynamics at a spatial resolution of similar to 30 AU. We report a bipolar outflow that was launched at symmetric positions with respect to the disk (similar to 80 AU in radius), but was concentrated at a distance of 90-130 AU from the disk center. The two outflow lobes had a conical shape and the gas inside was accelerating. The large off set of the launching position coincided with the landing site of the infall materials from the extended spiral structure (seen in dust) onto the disk. This indicates that bipolar outflows are efficiently launched within a narrow region outside the disk edge. We also identify a sharp transition in the gas kinematics across the tip of the spiral structure, which pinpoints the location of the so-called centrifugal barrier.