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    National Tsing Hua University Institutional Repository > 歷任校長 > 徐遐生 (2002-2006) > 期刊論文 >  Collapse of magnetized singular isothermal toroids. II. Rotation and magnetic braking


    Please use this identifier to cite or link to this item: http://nthur.lib.nthu.edu.tw/dspace/handle/987654321/80933


    Title: Collapse of magnetized singular isothermal toroids. II. Rotation and magnetic braking
    Authors: Allen, A.;Li, Z.Y.;Shu, F.H.
    教師: 徐遐生
    Date: 2003
    Publisher: American Astronomical Society
    Relation: ASTROPHYSICAL JOURNAL, American Astronomical Society, Volume 599, Issue 1, Part 1, DEC 10 2003, Pages 363-379
    Keywords: accretion, accretion disks
    ISM: clouds
    MHD
    stars: formation
    Abstract: We study numerically the collapse of rotating magnetized molecular cloud cores, focusing on rotation and magnetic braking during the main accretion phase of isolated star formation. Motivated by previous numerical work and analytic considerations, we idealize the precollapse core as a magnetized singular isothermal toroid, with a constant rotational speed everywhere. The collapse starts from the center and propagates outward in an inside-out fashion, satisfying exact self-similarity in space and time. For rotation rates and field strengths typical of dense low-mass cores, the main feature remains the flattening of the mass distribution along field lines-the formation of a pseudodisk, as in the nonrotating cases. The density distribution of the pseudodisk is little affected by rotation. On the other hand, the rotation rate is strongly modified by pseudodisk formation. Most of the centrally accreted material reaches the vicinity of the protostar through the pseudodisk. The specific angular momentum can be greatly reduced on the way, by an order of magnitude or more, even when the precollapse field strength is substantially below the critical value for dominant cloud support. The efficient magnetic braking is due to the pinched geometry of the magnetic field in the pseudodisk, which strengthens the magnetic field and lengthens the level arm for braking. Both effects enhance the magnetic transport of angular momentum from inside to outside. The excess angular momentum is carried away in a low-speed outflow that has, despite claims made by other workers, little in common with observed bipolar molecular outflows. We discuss the implications of our calculations for the formation of true disks that are supported against gravity by rotation.
    Relation Link: http://aas.org/
    URI: http://nthur.lib.nthu.edu.tw/dspace/handle/987654321/80933
    Appears in Collections:[ 徐遐生 (2002-2006)] 期刊論文
    [物理系] 期刊論文

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