A Spherical Model for "Starless" Cores of Magnetic Molecular Clouds and Dynamical Effects of Dust Grains

Abstract

In the standard picture of isolated star formation, dense ``starless'' cores are formed out of magnetic molecular clouds due to ambipolar diffusion. Under the simplest spherical geometry, I demonstrate that ``starless'' cores formed this way naturally exhibit a large scale inward motion, whose size and speed are comparable to those detected recently by Taffala et al. and Williams et al. in ``starless'' core L1544. My model clouds have a relatively low mass (of order 10 $M_{\odot }$) and low field strength (of order 10 $\mu$G) to begin with. They evolve into a density profile with a central plateau surrounded by a power-law envelope, as found previously. The density in the envelope decreases with radius more steeply than those found by Mouschovias and collaborators for the more strongly magnetized, disk-like clouds. At high enough densities, dust grains become dynamically important by greatly enhancing the coupling between magnetic field and the neutral cloud matter. The trapping of magnetic flux associated with the enhanced coupling leads, in the spherical geometry, to a rapid assemblage of mass by the central protostar, which exacerbates the so-called ``luminosity problem'' in star formation.

27 pages, 4 figures, accepted by ApJ

References in corpus (3)

• A High Resolution Study of the Slowly Contracting, Starless Core L1544
• Turbulent Cooling Flows in Molecular Clouds
• Dynamical Collapse of Nonrotating Magnetic Molecular Cloud Cores: Evolution Through Point-Mass Formation

Cited by in corpus (16)

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• Protostellar Disk Formation Enabled by Removal of Small Dust Grains
• The dynamics of collapsing cores and star formation
• Magnetically Regulated Star Formation in Turbulent Clouds
• How to Identify Pre-Protostellar Cores
• The structure of molecular clumps around high-mass young stellar objects
• Generalized Collapse Solutions with Nonzero Initial Velocities for Star Formation in Molecular Cloud Cores
• A Coupled Dynamical and Chemical Model of Starless Cores of Magnetized Molecular Clouds: I. Formulation and Initial Results
• Non-Equilibrium Chemistry of Dynamically Evolving Prestellar Cores: I. Basic Magnetic and Non-Magnetic Models and Parameter Studies
• Discovery of a Dusty Ring in the Coalsack: A Dense Core Caught in the Act of Formation?
• Binary and Multiple Star Formation in Magnetic Clouds: Bar Growth and Fragmentation
• Fragmentation of Magnetically Subcritical Clouds into Multiple Supercritical Cores and the Formation of Small Stellar Groups
• The dynamical influence of cooling in the envelope of prestellar and protostellar cores
• Ring Formation in Magnetically Subcritical Clouds and Multiple Star Formation
• Dynamo and Electrical Jet in Hall Plasmas, Application to Astrophysics