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Session 25 - Stellar Winds, Accretion, & Molecular Clouds.
Oral session, Monday, January 15
La Condesa, Hilton
Observations reveal a picture of dense (n \ga 10^4 cm^-3) molecular cloud cores embedded in much more massive, lower density (n \sim 10^2 - 10^3 cm^-3) molecular cloud envelopes. The low fraction of the total cloud mass contained in these cores and their tendency to give birth to stars soon after they are formed (\sim50% of dense cores contain detectable infrared sources) are consistent with the theoretical picture of magnetically supercritical core formation by ambipolar diffusion, with the cloud envelopes remaining supported by magnetic fields. We review a key result from a recent calculation (Basu and Mouschovias 1995, ApJ, 453, 271) which reveals a scaling law between the initial (ambient) magnetic field and the mass M_core and specific angular momentum (J/M)_core of a supercritical core. The magnetic field, through the processes of ambipolar diffusion and magnetic braking, enforces the approximate scaling laws M_core \propto B_0^-1 and (J/M)_core \propto B_0^-2, where B_0 is the ambient magnetic field. A physical explanation of this result is provided.
