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Title: Formation of a Keplerian disk in the infalling envelope around L1527 IRS: transformation from infalling motions to Kepler motions

We report Atacama Large Millimeter/submillimeter Array (ALMA) cycle 0 observations of the C{sup 18}O (J = 2-1), SO (J{sub N} = 6{sub 5}-5{sub 4}), and the 1.3 mm dust continuum toward L1527 IRS, a class 0 solar-type protostar surrounded by an infalling and rotating envelope. C{sup 18}O emission shows strong redshifted absorption against the bright continuum emission associated with L1527 IRS, strongly suggesting infall motions in the C{sup 18}O envelope. The C{sup 18}O envelope also rotates with a velocity mostly proportional to r {sup –1}, where r is the radius, whereas the rotation profile at the innermost radius (∼54 AU) may be shallower than r {sup –1}, suggestive of formation of a Keplerian disk around the central protostar of ∼0.3 M {sub ☉} in dynamical mass. SO emission arising from the inner part of the C{sup 18}O envelope also shows rotation in the same direction as the C{sup 18}O envelope. The rotation is, however, rigid-body-like, which is very different from the differential rotation shown by C{sup 18}O. In order to explain the line profiles and the position-velocity (PV) diagrams of C{sup 18}O and SO observed, simple models composed of an infalling envelope surrounding a Keplerian disk of 54 AU inmore » radius orbiting a star of 0.3 M {sub ☉} are examined. It is found that in order to reproduce characteristic features of the observed line profiles and PV diagrams, the infall velocity in the model has to be smaller than the free-fall velocity yielded by a star of 0.3 M {sub ☉}. Possible reasons for the reduced infall velocities are discussed.« less
Authors:
 [1] ;  [2] ; ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ; ;  [8] ;  [9] ;  [10]
  1. Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, HI 96720 (United States)
  2. Chile Observatory, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan)
  3. Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
  4. Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501 (Japan)
  5. Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Fukuoka 812-8581 (Japan)
  6. Joint ALMA Observatory, Ave. Alonso de Cordova 3107, Vitacura, Santiago (Chile)
  7. Department of Physics, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502 (Japan)
  8. Academia Sinica Institute of Astronomy and Astrophysics, PO Box 23-141, Taipei 10617, Taiwan (China)
  9. Department of Astronomical Science, Princeton University, Princeton, NJ 08544 (United States)
  10. National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan)
Publication Date:
OSTI Identifier:
22370123
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 796; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; CARBON MONOXIDE; DUSTS; EMISSION; MASS; OXYGEN 18; PROTOSTARS; RED SHIFT; ROTATION; STARS; SULFUR OXIDES; TRANSFORMATIONS; VELOCITY