Collapse of Magnetized Singular Isothermal Toroids: I. Non-Rotating Case

Abstract

We study numerically the collapse of non-rotating, self-gravitating, magnetized, singular isothermal toroids characterized by sound speed, $a$, and level of magnetic to thermal support, $H_0$. In qualitative agreement with previous treatments by Galli & Shu and other workers, we find that the infalling material is deflected by the field lines towards the equatorial plane, creating a high-density, flattened structure -- a pseudodisk. The pseudodisk contracts dynamically in the radial direction, dragging the field lines threading it into a highly pinched configuration that resembles a split monopole. The oppositely directed field lines across the midplane and the large implied stresses may play a role in how magnetic flux is lost in the actual situation in the presence of finite resistivity or ambipolar diffusion. The infall rate into the central regions is given to 5% uncertainty by the formula, $\dot{M}=(1+H_0)a^3/G$, where $G$ is the universal gravitational constant, anticipated by semi-analytical studies of the self-similar gravitational collapses of the singular isothermal sphere and isopedically magnetized disks. The introduction of finite initial rotation results in a complex interplay between pseudodisk and true (Keplerian) disk formation that is examined in a companion paper.

26 pages, 8 figures. To appear in v599 n1 ApJ December 10, 2003 issue

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• A chemical solver to compute molecule and grain abundances and non-ideal MHD resistivities in prestellar core collapse calculations
• Does Magnetic Levitation or Suspension Define the Masses of Forming Stars?
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• Testing Magnetic Field Models for the Class 0 Protostar L1527
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• A new HLLD Riemann solver with Boris correction for reducing Alfvén speed
• Outflows, cores and magnetic field orientations in W43-MM1 as seen by ALMA
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• How Does a Protostar Form by Magnetized Gravitational Collapse?
• The Rotation Dip in the Envelope-Disk Transition of HH 111: Evidence for Magnetic Braking
• Magneto-Gravitational Regulated Streamer Accretion onto a Class 0 Protostellar System