Molecular outflow launched beyond the disk edge

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstr. 1, 85748 Garching, Germany
e-mail: falves@mpe.mpg.de
² Institut de Ciències de l’Espai (CSIC-IEEC), Campus UAB, Carrer de Can Magrans S/N, 08193 Cerdanyola del Vallès, Catalonia, Spain
³ Departamento de Física–ICEx–UFMG, Caixa Postal 702, 30. 123-970 Belo Horizonte, Brazil
⁴ Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
⁵ School of Physics & Astronomy, University of Leeds, LS2 9 LN Leeds, UK
⁶ Department of Physics and Astronomy, Rice University, Main Street, 77005 Houston, USA

Received: 1 May 2017
Accepted: 5 July 2017

Abstract

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 (λ₀ ~ 1.3 mm) and molecular lines (CO, C¹⁸O and H₂CO), which are suitable tracers of disk, envelope, and outflow dynamics at a spatial resolution of ~30 AU. We report a bipolar outflow that was launched at symmetric positions with respect to the disk (~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 offset 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.