Dynamical Evidence for a Magnetocentrifugal Wind from a 20 M ⊙ Binary Young Stellar Object
Abstract
In Orion BN/KL, proper motions of λ7 mm vibrationally excited SiO masers trace the rotation of a nearly edge-on disk and a bipolar wide-angle outflow 10-100 AU from radio source I, a binary young stellar object of ~20 M ⊙. Here we map ground-state λ7 mm SiO emission with the Very Large Array and track proper motions over 9 yr. The innermost and strongest emission lies in two extended arcs bracketing Source I. The proper motions trace a northeast-southwest bipolar outflow 100-1000 AU from Source I with a median three-dimensional motion of ~18 km s-1. An overlying distribution of λ1.3 cm H2O masers betrays similar flow characteristics. Gas dynamics and emission morphology traced by the masers suggest the presence of a magnetocentrifugal disk wind. Reinforcing evidence lies in the colinearity of the flow, apparent rotation across the flow parallel to the disk rotation, and recollimation that narrows the flow opening angle ~120 AU downstream. The arcs of ground-state SiO emission may mark the transition point to a shocked super-Alfvénic outflow.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2013
- DOI:
- 10.1088/2041-8205/770/2/L32
- arXiv:
- arXiv:1305.4150
- Bibcode:
- 2013ApJ...770L..32G
- Keywords:
-
- ISM: individual objects: Orion BN/KL;
- ISM: jets and outflows;
- ISM: kinematics and dynamics;
- ISM: molecules;
- masers;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 7 pages, 4 figures, and 1 table. Accepted for publication in ApJ Letters