Nonhomologous contraction and equilibria of self-gravitating, magnetic interstellar clouds embedded in an intercloud medium: star formation. II. Results

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Abstract

The paper studies the equilibrium of self-gravitating isothermal models of interstellar clouds with a frozen-in magnetic field linked smoothly to the field of a hot tenuous intercloud medium. Equilibrium states are determined which can be reached by clouds contracting nonhomologously from a spherical uniform initial state. Three free parameters characterize the problem: a dimensionless initial radius related to the Jeans length of the cloud, the initial ratio of the magnetic and gas pressures in the cloud, and the initial ratio of the intercloud and cloud pressures. The dependence of the solutions on each of these parameters is investigated. It is found that: (1) the frozen-in field causes the cloud to become oblate with its major axis normal to the field lines; (2) the flattening increases as the magnetic-field strength, gravitational forces, or intercloud pressure increases; (3) increasing intercloud pressure eventually leads to gravitational collapse; and (4) the cloud can reach equilibrium only if its radius does not exceed some critical value. The observed inefficiency of the star-formation process within massive clouds is examined and explained in terms of magnetic phenomena in a collapsing cloud.
Original languageEnglish (US)
Pages (from-to)141-158
Number of pages18
JournalThe Astrophysical journal
Volume207
DOIs
StatePublished - Jul 1976
Externally publishedYes

Keywords

  • Gravitational Effects
  • Interstellar Magnetic Fields
  • Interstellar Matter
  • Magnetic Clouds
  • Star Formation
  • Zeeman Effect
  • Astronomical Models
  • Correlation
  • Equilibrium
  • Gas Pressure
  • Gravitational Collapse
  • Astrophysics

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