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Title: Angular momentum exchange by gravitational torques and infall in the circumbinary disk of the protostellar system L1551 NE

We report an ALMA observation of the Class I binary protostellar system L1551 NE in the 0.9 mm continuum, C{sup 18}O (3-2), and {sup 13}CO (3-2) lines at a ∼1.6 times higher resolution and a ∼6 times higher sensitivity than those of our previous SubMillimeter Array (SMA) observations, which revealed a r ∼ 300 AU scale circumbinary disk in Keplerian rotation. The 0.9 mm continuum shows two opposing U-shaped brightenings in the circumbinary disk and exhibits a depression between the circumbinary disk and the circumstellar disk of the primary protostar. The molecular lines trace non-axisymmetric deviations from Keplerian rotation in the circumbinary disk at higher velocities relative to the systemic velocity, where our previous SMA observations could not detect the lines. In addition, we detect inward motion along the minor axis of the circumbinary disk. To explain the newly observed features, we performed a numerical simulation of gas orbits in a Roche potential tailored to the inferred properties of L1551 NE. The observed U-shaped dust features coincide with locations where gravitational torques from the central binary system are predicted to impart angular momentum to the circumbinary disk, producing shocks and hence density enhancements seen as a pair of spiral arms.more » The observed inward gas motion coincides with locations where angular momentum is predicted to be lowered by the gravitational torques. The good agreement between our observation and model indicates that gravitational torques from the binary stars constitute the primary driver for exchanging angular momentum so as to permit infall through the circumbinary disk of L1551 NE.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6]
  1. Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China)
  2. Joint ALMA Observatory, Ave. Alonso de Cordova 3107, Vitacura, Santiago (Chile)
  3. ALMA Project Office, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan)
  4. Faculty of Humanity and Environment, Hosei University, Chiyoda-ku, Tokyo 102-8160 (Japan)
  5. Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong)
  6. Center for Frontier Science, Chiba University, Inage-ku, Chiba 263-8522 (Japan)
Publication Date:
OSTI Identifier:
22370208
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 796; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANGULAR MOMENTUM; AXIAL SYMMETRY; BINARY STARS; COMPUTERIZED SIMULATION; DENSITY; DUSTS; MOLECULES; RESOLUTION; ROTATION; SENSITIVITY; VELOCITY